JP2013205361A - Microwave sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a microwave sensor that outputs a radio wave of a first specific frequency different from a second specific frequency by using a semiconductor electronic component for generating high frequency for the second specific frequency, in which unnecessary emission is suppressed and the S/N ratio is improved.SOLUTION: A microwave sensor which is constituted so as to output a radio wave of a 24 GHz band to outside includes: a FET 10 that is constituted to be suitable for amplifying a signal of a 10 GHz; a signal amplification circuit 20 that is constituted so as to amplify a signal of a 24 GHz band together with the FET 10; and a ground circuit that releases current supplied to the FET 10 to a ground. Each of the signal amplification circuit and ground circuit includes: selective attenuation means 24 and 40 that are constituted so as to attenuate the signal of a 10 GHz band without attenuating the signal of a 24 GHz band out of the signals generated by the FET 10.

Description

  The present invention relates to a microwave sensor, and more particularly, to a microwave sensor configured using a high-frequency generating component adapted to a frequency different from an output signal frequency.

  Currently, in Japan, radio waves in the 10 GHz band can be used for consumer devices, so a semiconductor chip IC or semiconductor electronic component for generating high frequency optimized to output a signal in the 10 GHz band is supplied. ing. For example, FIG. 6 shows an example of frequency gain characteristics of such a semiconductor electronic component, which has a high gain in a wavelength range (5 to 15 GHz) centered at 10 GHz.

  On the other hand, in Japan and other countries in the world, radio waves in the 24 GHz band (24.05 to 24.25 GHz) can also be used in consumer devices. As shown in FIG. 7, the frequency gain characteristic of such a 24 GHz band radio wave sensor has a high gain only in the 24 GHz band (24.05 to 24.25 GHz) and has a very low gain in the other frequency bands. It is desirable.

  However, since the semiconductor electronic component for the 24 GHz band is only manufactured for a special purpose, the unit price is very high and the distribution amount is very small. Therefore, at present, it is necessary to develop and manufacture a 24 GHz band radio wave sensor using commercially available semiconductor electronic components for the 10 GHz band.

  When a radio wave sensor of 24 GHz band is manufactured using semiconductor electronic components for 10 GHz band, it must be configured to have high performance, that is, a high S / N ratio in the 24 GHz band. However, since the semiconductor electronic component itself is optimized for the 10 GHz band, the gain is high in the 10 GHz band and the gain is small in the 24 GHz band as shown in FIG. For this reason, even if a circuit for oscillating a signal in the 24 GHz band is configured simply using semiconductor electronic components for the 10 GHz band, only a gain as shown in FIG. 8 can be obtained. That is, the gain in the 10 GHz band is relatively increased with respect to the gain obtained in the 24 GHz band.

  Therefore, the radio wave in the 10 GHz band that is a noise component is large and the S / N ratio is low. Further, such a 10 GHz band radio wave having a predetermined intensity or more is unnecessary emission (spurious emission) for the radio sensor of the 24 GHz band and must be removed.

  As a method for increasing the S / N ratio of a radio wave sensor in a 24 GHz band, there are a method for amplifying a signal component (24 GHz band) and a method for reducing a noise component (such as a 10 GHz band). In the method of amplifying the signal component, it can be considered that the signal component is mainly amplified by adding a circuit configuration such as an amplifier. As a method of reducing noise components, a method of removing noise components other than a desired frequency by arranging a noise cut filter in the output path of an output signal is widely known (for example, Patent Document 1). reference).

  If power saving of the radio wave sensor is not taken into consideration, it is considered possible to increase the S / N ratio by the above method. On the other hand, in order to save power in the radio wave sensor, it is necessary to avoid unnecessarily amplifying the signal component. Therefore, it is preferable to employ only a method for reducing the noise component.

  However, when a noise cut filter is arranged in the output path, a part of a desired signal component (24 GHz band) is reduced in addition to a noise component (10 GHz band or the like). For this reason, it has been found that, in the power saving design, the radio signal component having a low gain is further reduced by the filter, which makes it difficult to ensure a sufficiently high S / N ratio.

  Therefore, the applicant of the present application selectively reflects a desired signal component (for example, 24 GHz) back to the high-frequency semiconductor component by reflecting the desired signal component (for example, 24 GHz) and a high-frequency semiconductor component suitable for signal amplification in a frequency band (for example, 10 GHz) that becomes a noise component. A reflection circuit configured to oscillate a desired signal component, and an attenuation circuit provided on the downstream side of the reflection circuit (distal side of the reflection circuit as viewed from the high-frequency semiconductor component) to remove the noise component Have been proposed (see Japanese Patent Application No. 2011-046462).

  According to this configuration, only the desired signal component of the high-frequency signal generated by the high-frequency semiconductor component is repeatedly reflected and amplified and oscillated by the reflection circuit, while the noise component is attenuated without being returned to the high-frequency semiconductor component. It can be removed with a circuit. As a result, noise components can be removed in the amplification stage, so that it is not necessary to arrange a filter for removing noise components in the output stage as in the prior art, and a desired signal component is reduced by the filter in the output stage. Can be prevented.

JP 2004-117132 A

  However, the present inventor has further studied that the noise component is likely to resonate between the reflection circuit and the ground circuit of the high-frequency semiconductor component, and that the noise component is only generated by the attenuation circuit disposed on the downstream side of the reflection circuit. I found it difficult to completely remove.

  The present invention has been made to solve such a problem, and uses a semiconductor electronic component for generating a high frequency at a second specific frequency, and has a first specific frequency different from the second specific frequency. An object of the present invention is to provide a microwave sensor that suppresses unnecessary emission and increases the S / N ratio in a microwave sensor that outputs radio waves.

  In order to solve the above-described problem, the present invention is a microwave sensor configured to output a radio wave having a first specific frequency to the outside, and has a second specific frequency different from the first specific frequency. A high-frequency semiconductor component suitably configured to amplify a signal, a signal amplification circuit connected to the high-frequency semiconductor component and configured to amplify a signal of a first specific frequency together with the high-frequency semiconductor component, and a high-frequency semiconductor A ground circuit that is connected to the component and releases the current supplied to the high-frequency semiconductor component to the ground, and each of the signal amplification circuit and the ground circuit includes a first specific signal out of the signals generated by the high-frequency semiconductor component. It is characterized by comprising selective attenuating means configured to attenuate the signal of the second specific frequency band without attenuating the signal of the frequency band.

  When a microwave sensor of 24 GHz (first specific frequency) is manufactured using a high-frequency semiconductor component for 10 GHz (second specific frequency), since the high-frequency semiconductor component is not a dedicated component for 24 GHz, high performance at 24 GHz ( There arises a problem that a high S / N ratio) cannot be secured. In particular, a large noise is generated in the 10 GHz band where the gain of the high-frequency semiconductor component is high.

  As described above, as a method for improving the performance (S / N ratio) of the microwave sensor, a method of amplifying signal components to increase the S / N ratio, or a method of reducing noise components to increase the S / N ratio. Although there is a method of increasing the S / N ratio with a low power consumption, a method of increasing the S / N ratio by reducing the noise component is preferable.

  At present, as a method for reducing a noise component, a method of providing a noise cut filter in an output path is widely known. However, the present inventor has found that when the power consumption is suppressed and the S / N ratio is improved, the degree of improvement of the S / N ratio varies greatly depending on the installation position of the filter. That is, as described in the section of the prior art, when a noise cut filter is provided in the output path, not only the noise component (10 GHz band signal) but also the signal component (24 GHz signal) is reduced, resulting in a high S / N. It was found that the ratio could not be obtained.

  The present invention is for high-frequency generation for a second specific frequency different from a desired frequency without using a dedicated high-frequency generation semiconductor component adapted to the frequency of the desired output signal (first specific frequency). Provided is a microwave sensor using a semiconductor component, which has low power consumption (power saving) and high performance (high S / N ratio).

  For this reason, in the present invention, the high-frequency semiconductor component includes a signal amplification circuit for amplifying and oscillating a signal of the first specific frequency in cooperation with the high-frequency semiconductor component, and a DC supplied from the power source to the high-frequency semiconductor component. A selection is made to attenuate the signal of the second specific frequency band without attenuating the signal of the first specific frequency band in both of the signal amplification circuit and the ground circuit, and a ground circuit that releases the current to the ground is connected. Dynamic damping means are provided.

  Therefore, in the present invention, an unnecessary signal in the second specific frequency band that easily oscillates due to the characteristics of the high-frequency semiconductor component during signal amplification in the signal amplification circuit by the selective attenuating means provided in the signal amplification circuit. Therefore, it is not necessary to provide a noise cut filter in the output path as in the prior art. For this reason, since the signal of the first specific frequency can be taken out without being attenuated by the noise cut filter, a high S / N ratio can be obtained even if the output value of the output signal of the desired first specific frequency is low. It can be secured. Therefore, by efficiently reducing the noise component (the signal of the second specific frequency band) without consuming more power than necessary and amplifying the desired signal component (the signal of the first specific frequency), A high-performance (high S / N ratio) microwave sensor can be obtained.

  Furthermore, in the present invention, an unnecessary second specific frequency band signal that could not be completely removed by the selective attenuation circuit provided in the signal amplifier circuit resonates between the signal amplifier circuit and the ground circuit, In order to solve the new problem that this may be output as a noise component, selective attenuation means is provided in both the signal amplification circuit and the ground circuit that are the resonance sources. As described above, the present invention is a practically excellent invention capable of obtaining a high-performance (high S / N ratio) microwave sensor by devising the arrangement position of the selective attenuation means.

In the present invention, it is preferable that the selective attenuating means includes: an unnecessary radio wave removing means configured to attenuate a signal of the second specific frequency band; and a first of the signals generated by the high-frequency semiconductor component. Inflow blocking means for blocking a signal having a specific frequency from flowing into the unnecessary radio wave removing means.
According to the present invention configured as described above, in both the signal amplifier and the ground circuit, an unnecessary signal in the second specific frequency band can be attenuated by the unnecessary radio wave removing means, while the desired first frequency band can be attenuated. A signal in a specific frequency band is prevented from flowing into the unnecessary radio wave removing means by the inflow blocking means, so that it is efficiently amplified through the signal amplifier and the ground circuit without being attenuated by the unnecessary radio wave removing means. Can do. Thereby, a microwave sensor having a high S / N ratio can be obtained.

Preferably, in the present invention, the ground circuit includes a virtual ground circuit for a signal of the first specific frequency, and the selective attenuation means included in the ground circuit branches from a transmission line extending from the high-frequency semiconductor component to the virtual ground circuit. It is provided to do.
According to the present invention configured as described above, by providing the virtual ground circuit for the signal having the first specific frequency, the signal having the first specific frequency can be efficiently oscillated. At this time, if a direct grounding circuit is used instead of the virtual grounding circuit, a signal with a frequency other than the signal with the first specific frequency (including the signal with the second specific frequency) is grounded. In addition, when the direct ground circuit is used, signals of other frequencies flow directly to the ground circuit and are difficult to flow to the selective attenuating means, so that the signal of the second specific frequency is not attenuated by the selective attenuating means.

  In the present invention, a virtual ground circuit for a signal having the first specific frequency is provided, and a selective attenuating means is branched from the virtual ground circuit, so that only the signal having the first specific frequency is grounded. The second specific frequency signal generated between the signal amplification circuit and the ground circuit can be efficiently oscillated and the second specific frequency signal can be easily guided to the selective attenuation means. Can be effectively suppressed.

In the present invention, it is preferable that the inflow prevention unit includes a stub circuit adapted to the signal having the first specific frequency, and the unnecessary radio wave removing unit is connected to the stub circuit, and the signal having the second specific frequency is provided. And an induction circuit for inducing a signal having a second specific frequency to the resistance.
According to the present invention configured as described above, the inflow blocking means functions as a pass prevention filter that suppresses the inflow of the signal of the first specific frequency by the stub circuit adapted to the signal of the first specific frequency, The unnecessary radio wave removing means functions to draw a signal of the second specific frequency into the resistor by the induction circuit and convert it into thermal energy by the resistor and consume it. Thus, both the inflow prevention means and the unnecessary radio wave removal means can prevent the inflow of the signal of the first specific frequency and attenuate the signal of the second specific frequency with a simple configuration.

  According to the present invention, unnecessary emission is suppressed in a microwave sensor that outputs a radio wave of a first specific frequency different from the second specific frequency using a semiconductor electronic component for generating a high frequency of a second specific frequency. Thus, the S / N ratio can be increased.

It is a block diagram of the microwave sensor in embodiment of this invention. It is a block diagram of the oscillator in embodiment of this invention. It is explanatory drawing of the amplification effect | action of the amplifier (FET) in embodiment of this invention. It is explanatory drawing of the selective amplification attenuation circuit in embodiment of this invention. It is explanatory drawing of the ground circuit in embodiment of this invention. It is a frequency gain characteristic of FET in the embodiment of the present invention. It is a desired frequency gain characteristic of the microwave sensor in the embodiment of the present invention. It is a frequency gain characteristic of the microwave sensor which concerns on the comparative example comprised using FET which has the frequency gain characteristic of FIG.

Next, a microwave sensor according to an embodiment of the present invention will be described with reference to FIGS. The microwave sensor of the present embodiment is preferably applied to an object detection sensor for indoor watering equipment.
As shown in FIG. 1, the microwave sensor 1 of this embodiment includes an oscillator 2 that generates a transmission signal having a frequency of 24 GHz (24.05 to 24.25 GHz), which is a first specific frequency band, and an oscillator. The antenna 4 that radiates the transmission wave (transmission signal) from 2 as a radio wave to the outside and receives the reflected wave (reception signal) reflected by the object (for example, a user of an indoor watering device), and the transmission signal and reception A mixer circuit 6 for mixing the signals and detecting the Doppler signal.

  In the present embodiment, the oscillator 2, the antenna 4 and the mixer circuit 6 are integrally formed on the electronic circuit board. The oscillator 2, the antenna 4 and the mixer circuit 6 are electrically connected on the substrate by a transmission line such as a metal foil.

  The microwave sensor 1 of this embodiment is configured to detect the movement of an object using radio waves. That is, the transmission wave output from the antenna 4 is a radio wave having a first specific frequency, and when reflected by a moving object, the frequency changes according to the movement of the object. A radio wave having a changed frequency (that is, a reflected wave) is received by the antenna 4. In the microwave sensor 1, transmitted waves and reflected waves having different frequencies are input to the mixer circuit 6, and the mixer circuit 6 outputs a detection signal (difference signal) representing movement information of the object. The microwave sensor 1 outputs this detection signal to the outside.

  FIG. 2 shows a circuit diagram of the oscillator 2 of the present embodiment. The oscillator 2 includes an FET 10 and a high-frequency oscillation circuit 12. The high-frequency oscillation circuit 12 includes a selective amplification and attenuation circuit 20, unnecessary radio wave removal circuits 30 and 40, a high-frequency ground circuit 50, an output circuit 60, and the like.

  The FET 10 includes a semiconductor chip for generating high frequency (a core part having a laminated structure of semiconductors), an external terminal, a bonding wire for connecting an electrode (gate electrode, drain electrode, source electrode) of the semiconductor chip and the external terminal, and a transmission line. A high-frequency semiconductor component or electronic component package having internal wiring such as the above and a resin material covering them. In the present embodiment, as shown in FIG. 6, the FET 10 is optimized so as to increase the gain in the 10 GHz band (5 to 15 GHz) that is the peripheral band of the second specific frequency (10 GHz). Therefore, the FET 10 has a small gain at the frequency of the radio wave in the 24 GHz band (24.05 to 24.25 GHz) that is the peripheral band of the first specific frequency (approximately 24 GHz) output from the microwave sensor 1 of the present embodiment. .

  As described above, since the FET 10 has a low gain in the 24 GHz band, even if a microwave sensor for the 24 GHz band is manufactured using the FET 10 by a power saving design, a large signal output can be obtained with a small power consumption in the 24 GHz band. difficult. On the other hand, since the noise component (10 GHz band) has a high gain in the 10 GHz band, the noise component may increase.

As shown in FIG. 3, the FET 10 can amplify the input X with a gain A corresponding to the frequency to obtain an output Y, and further repeat this amplification operation using a feedback circuit to obtain a desired frequency. A signal can be oscillated. As shown in FIG. 2, the FET 10 has three external terminals (gate G, drain D, source S). However, the source S has a first source terminal S1 and a second source terminal S2.
The high-frequency semiconductor component may be composed of a transistor. In this case, the gate, drain, and source can be read as the base, collector, and emitter, respectively.

  The input X is input to the gate G, and the output Y is output from the drain D. Note that a pass circuit is formed in the FET 10, and this pass circuit functions as a feedback circuit. The passing circuit is a capacitor C formed by a gap between the drain D and the gate G. Further, the passage circuit may be an external passage provided between the drain D and the gate G.

  The outline of the amplification action of the FET 10 is as follows. First, by supplying power to the FET 10, signals including various frequency signals are generated. These signals flow to the gate G and are transmitted to a downstream circuit (selective amplification attenuation circuit 20). Next, as described later, the signal in the 24 GHz band is returned to the gate G and input to the gate G. The signal input to the gate G is amplified by the amplification action of the FET 10 and output from the drain D which is an output stage. Then, a part of the signal output from the drain D returns to the gate G as the input stage via the feedback circuit. In this way, the signal in the 24 GHz band is amplified to a predetermined magnitude by repeating amplification, and is finally output to the output circuit 60 from the drain D which is an output stage.

  A selective amplification / attenuation circuit 20 is connected to the gate G which is an input unit. A power source 63 (for example, 3 VDC) and an output circuit 60 to the antenna 4 are connected to the drain D that is an output unit. An unnecessary radio wave removal circuit 40 and a high frequency ground circuit 50 are connected to the source S. The source S is substantially grounded with respect to the signal in the 24 GHz band by the high-frequency ground circuit 50 which is a virtual ground circuit. Therefore, the FET 10 is supplied with power from the power source 63 via the drain D, amplifies the signal in the 24 GHz band by repeatedly inputting the signal in the 24 GHz band to the gate G together with the selective amplification attenuation circuit 20, and the amplified output signal is drained. D is output to the output circuit 60.

The selective amplification / attenuation circuit 20 includes a reflection circuit 22 and an unnecessary radio wave removal circuit 24 connected to the reflection circuit 22 on the distal side or the downstream side of the reflection circuit 22 with respect to the FET 10. It is a frequency determination circuit.
The reflection circuit 22 includes a rectangular gate transmission line 22a having a predetermined length and a dielectric resonator 22b disposed on the side of the position P1 of the gate transmission line 22a (see FIG. 4).
The dielectric resonator 22b is magnetically coupled to the gate transmission line 22a at the position P1, and forms a resonance circuit in which the reflection coefficient of the electromagnetic wave increases near the resonance frequency (24 GHz).

  As shown in FIG. 4, the gate transmission line 22a is connected to the gate G (position P0) of the FET 10, and the length L1 from the gate G to the dielectric resonator 22b (position P1) is a signal wavelength of 24 GHz. It is set to approximately 0.75λ with respect to λ. The signal wavelength λ of 24 GHz is a wavelength when a 24 GHz signal is transmitted through the transmission line. The length L1 may be an odd multiple of λ / 4 (λ / 4 × (2n−1), where n is a natural number (1, 2, 3,...)).

  The position P0 may be the base end portion of the gate transmission line 22a. However, in order to set the length L1 more strictly, in the present embodiment, the position P0 is connected to the gate G of the FET 10 by an internal wiring. This is the position of the gate electrode of the semiconductor chip. Therefore, when considering the internal wiring from the gate electrode of the semiconductor chip to the base end of the gate transmission line 22a, the line length of the transmission line, and the line resistance, the length of the conductive path from the gate electrode of the semiconductor chip to the position P1. Is set to have a length that is substantially an odd multiple of λ / 4 (λ is a signal wavelength of 24 GHz).

  Instead of the dielectric resonator 22b, a reflective stub that branches sideways from the position P1 of the gate transmission line 22a may be provided. When this reflective stub is an open stub with an open end, its length can be an odd multiple of λ / 4, and when it is a short stub with a shorted end, The length can be a natural number times approximately λ / 2.

  As shown in FIG. 4, the gate transmission line 22a has a length L2 from the dielectric resonator 22b (position P1) to the tip 22c (position P2) of about 0. 0 with respect to the signal wavelength λ of 24 GHz. It is set to 25λ. Note that the length L2 may be an odd multiple of λ / 4 (λ / 4 × (2n−1), where n is a natural number (1, 2, 3,...)).

  By configuring the reflection circuit 22 in this way, when a signal in the 24 GHz band is transmitted from the position P0 toward the position P1 downstream (in the direction toward the unnecessary radio wave removal circuit 24), the signal in the 24 GHz band is obtained. Is totally reflected in the same phase by the dielectric resonator 22b, which is the first reflecting means, and returned to the FET 10 side.

  On the other hand, a part of the signal in the 24 GHz band is transmitted further downstream from the position P1 to the position P2 through the gate transmission line 22a without being reflected by the dielectric resonator 22b. That is, since it is difficult to completely reflect the signal in the 24 GHz band by the dielectric resonator 22b, a part of the signal passes through the position P1.

The signal in the 24 GHz band that has passed through the position P1 is totally reflected in the same phase at the front end portion 22c (position P2) of the gate transmission line 22a that is open to at least the signal in the 24 GHz band, and is returned to the FET 10 side. The tip 22c of the gate transmission line 22a corresponds to the second reflecting means of this embodiment.
At the position P1 of the gate transmission line 22a, the dielectric resonator 22b and the gate transmission line 22a are magnetically coupled, and a short state is obtained for a signal in the 24 GHz band. On the other hand, the front end portion 22c of the gate transmission line 22a is an open state, and thus is in an open state.

  In this embodiment, the transmission distance (length L2) from the open end of the gate transmission line 22a to the dielectric resonator 22b is set to a length that is an odd multiple of λ / 4 with respect to the signal in the 24 GHz band. Has been. As a result, the reflected wave in the 24 GHz band from the open end is short-circuited at the coupling portion (position P1) of the dielectric resonator 22b and has the same phase as the reflected wave from the dielectric resonator 22b. For this reason, in the 24 GHz band, the reflected signal from the open end and the signal from the dielectric resonator 22b reinforce each other without canceling each other.

  Thereby, in the present embodiment, a desired signal that has not been reflected by the first reflecting means (dielectric resonator 22b) is reflected by the second reflecting means (the end portion 22c of the gate transmission line 22a), In addition, the reflected signals from the first reflecting means and the reflected signals from the second reflecting means can be matched in phase so that they can be returned to the FET 10. For this reason, in this embodiment, a signal in the 24 GHz band can be reliably reflected to the FET 10 and the amplification efficiency can be improved.

  In the present embodiment, the distal end 22c of the gate transmission line 22a as the second reflecting means is an open end, but the present invention is not limited to this, and the end 22c is short-circuited and has a length L2. May be set to a natural number multiple of λ / 2. In this case, the tip 22c of the gate transmission line 22a can be short-circuited by disposing a dielectric resonator or grounding it.

  In the present embodiment, two reflecting means are provided. However, the present invention is not limited to this, and three or more reflecting means may be provided so that the phases of the reflected waves are aligned. For example, a plurality of dielectric resonators may be arranged at a predetermined interval with respect to the gate transmission line 22a.

The unnecessary radio wave removal circuit 24 is provided on the downstream side of the reflection circuit 22, and is composed of transmission lines 24a and 24b, a reflection stub 24c, and a resistor 24d.
Of the signals transmitted from the gate G, it is desirable that the reflection circuit 22 be directly connected to the gate G in order to reliably return a signal in the 24 GHz band to the FET 10. For this reason, it is desirable to provide the unnecessary radio wave removing circuit 24 at the subsequent stage (downstream side) of the reflecting circuit 22.

As described above, since the signal generated by the FET 10 includes signals of various frequencies, the signal transmitted from the gate G toward the dielectric resonator 22b includes a signal in the 10 GHz band. . When the 10 GHz band signal is returned to the FET 10, the 10 GHz band signal is amplified with a large gain. Therefore, the unnecessary radio wave removing circuit 24 mainly removes the unnecessary signal for removing the 10 GHz band signal before it is amplified. It is comprised so that it may function as a removal means.
In addition, the transmission line 24 a and the reflection stub 24 c of the unnecessary radio wave removal circuit 24 function as an inflow blocking unit (passage prevention filter) that blocks signals in the 24 GHz band from flowing into the unnecessary radio wave removal circuit 24.

  Therefore, the unnecessary radio wave removing circuit 24 functions as an unnecessary signal removing unit and an inflow blocking unit so as to attenuate the 10 GHz band signal without attenuating the 24 GHz band signal among the signals generated by the FET 10. It functions as a configured selective attenuation means.

First, the inflow prevention means will be described.
A series circuit of the transmission line 24a and the reflective stub 24c having the open end functions as an inflow prevention means. This series circuit extends at least on the downstream side of the dielectric resonator 22b (between the position P1 and the position P2 of the gate transmission line 22a) so as to be orthogonal to the side on the side of the gate transmission line 22a. Preferably, the transmission line 24a is connected to the front end 22c (position P2) of the gate transmission line 22a or a position P5 close thereto. The position P5 is a position having a length L5 from the position P0.
The length L3 of the transmission line 24a and the length L4 of the reflection stub 24c are set to odd multiples of λ / 4 for signals in the 24 GHz band, respectively.

For a signal in the 24 GHz band, the position P4 (the tip of the reflective stub 24c) is in the open state, so the position P3 (the base end of the reflective stub 24c) is in the short state, and the position P5 is in the open state.
As described above, since the connection point between the serial circuit of the transmission line 24a and the reflection stub 24c and the gate transmission line 22a is an open point, an unnecessary radio wave removal circuit 24 is connected to the end of the connection point for the signal in the 24 GHz band. Looks like not. For this reason, the signal in the 24 GHz band is substantially prevented from flowing into the unnecessary radio wave removing circuit 24.

  Further, in the gate transmission line 22a, the direction in which a signal in the 24 GHz band flows is the length direction of the gate transmission line 22a. For this reason, in this embodiment, the transmission line 24a is connected to the gate transmission line 22a so as to be orthogonal to the length direction thereof, so that signals in the 24 GHz band are less likely to flow into the transmission line 24a. Yes.

  In the present embodiment, the transmission line 24a and the gate transmission line 22a are connected so as to be orthogonal to each other. However, the transmission line 24a and the gate transmission line 22a are not limited to this, and the transmission line 24a extends in the length direction from the tip 22c of the gate transmission line 22a. The line 24a may be connected. Also in this case, the tip 22c of the gate transmission line 22a is an open surface for signals in the 24 GHz band.

Next, unnecessary signal removing means will be described.
One end of the series circuit of the transmission line 24b and the resistor 24d is connected to the connection part of the transmission line 24a and the reflective stub 24c, or the base end part of the reflective stub 24c, and the other end is grounded. In the present embodiment, a circuit extending from the transmission line 24a to the ground via the transmission line 24b and the resistor 24d functions as an unnecessary signal removing unit.

Since a signal in the 10 GHz band is held in the ground only by flowing into the ground, it is desirable to convert the energy into heat and reliably consume it.
For this reason, in this embodiment, the series circuit of the transmission lines 24a and 24b as the induction circuit is optimized so as to efficiently draw an unnecessary signal mainly in the 10 GHz band into the resistor 24d, and is drawn into the resistor 24d. The unnecessary signal in the 10 GHz band is converted into heat by the resistor 24d and removed.
In this embodiment, since the resistor 24d provided for forming the gate potential is used as a part of the unnecessary radio wave removing circuit, the increase in size of the device can be suppressed.

  In the present embodiment, the 10 GHz band signal input from the reflection circuit 22 to the unnecessary radio wave removal circuit 24 is configured not to return to the FET 10, so that the connection point from the reflection circuit 22 to the unnecessary radio wave removal circuit 24 is 10 GHz band. The voltage standing wave ratio (VSWR) at is set to a small value. Specifically, when the VSWR is 1.4 or less, a 10 GHz band signal can be transmitted to the resistor 24d with less reflection.

  For this reason, the transmission lines 24a and 24b serving as induction circuits constitute an impedance matching circuit for impedance matching between the resistor 24d and the end face of the reflection circuit 22 in the 10 GHz band. Specifically, as described above, the induction circuit is configured so that VSWR is 1.4 or less. This induction circuit is appropriately set according to the element resistance value and size of the resistor 24d. As described above, the length L3 of the transmission line 24a (an odd multiple of λ / 4) is determined by the signal wavelength λ in the 24 GHz band. Therefore, the length L6 of the transmission line 24b is determined by the transmission line 24a and the reflection stub 24c. It is determined in consideration of the width of

  With this configuration, the 10 GHz band signal input from the reflection circuit 22 to the unnecessary radio wave removal circuit 24 is transmitted to the resistor 24d without being reflected by the FET 10 and is consumed and removed as heat. In addition, in the present embodiment, since the signal in the 10 GHz band is removed by the unnecessary radio wave removing circuit 24 before amplification, it is necessary to remove the unnecessary signal by the noise cut filter arranged in the output path after the amplification as in the prior art. There is no. For this reason, it is possible to prevent a desired signal in the 24 GHz band from being attenuated by the noise cut filter.

The unnecessary radio wave removing circuit 30 has the same configuration as the above-described unnecessary radio wave removing circuit 24.
As shown in FIG. 2, the unnecessary radio wave removal circuit 30 constitutes a power supply unit, and a transmission line 31 connected to the drain D that is the output unit of the FET 10 and a reflection connected to the tip of the transmission line 31. A stub 32, a transmission line 33 branching from the rectangular reflective stub 32 at the distal end of the transmission line 31 (base end of the reflective stub 32), and a resistor 34 connected to a power source 63 are provided.
The unnecessary radio wave removing circuit 30 is configured not to transmit a 24 GHz band signal output from the FET 10 to the power supply 63 side, and to remove an unnecessary signal in the 10 GHz band output from the FET 10.

In the transmission line 31, the length of the conductive path from the drain electrode of the semiconductor chip of the FET 10 to the tip of the transmission line 31 via the internal wiring is an odd multiple of approximately λ / 4 with respect to the signal wavelength λ of 24 GHz ( The length is set so that λ / 4 × (2n−1), where n is a natural number.
The reflective stub 32 is set to a length (λ / 4 × (2n−1), where n is a natural number) that is approximately an odd multiple of λ / 4.

  Since the end surface of the reflective stub 32 is an open end, the tip portion is an open surface. On the other hand, the base end portion of the reflection stub 32 becomes a short surface because the phase of the signal is shifted by λ / 4 (2π / 4). Further, the base end portion of the transmission line 31 (specifically, the drain electrode of the semiconductor chip) is an open surface because the phase of the signal is shifted from the base end portion of the reflective stub 32 by λ / 4 (2π / 4). Therefore, by providing the transmission line 31 and the reflective stub 32, the connection surface (specifically, the drain electrode of the semiconductor chip) between the transmission line 31 and the FET 10 becomes an open surface for a signal in the 24 GHz band. Is not transmitted toward the reflective stub 32. Thereby, it can suppress that the signal of 24 GHz band which is an output signal is transmitted to the power supply 63 side, and is attenuated.

  On the other hand, a signal in the 10 GHz band is transmitted from the transmission line 31 toward the resistor 34, and part of the signal is reflected to return to the FET 10 side. However, in this embodiment, the width of the reflective stub 32 and the length of the transmission line 33 connected to the proximal end of the reflective stub 32 are such that all signals in the 10 GHz band are consumed (removed) by the resistor 34. Is set.

  That is, in this embodiment, the internal wiring of the semiconductor chip, the transmission line 31, the base end portion of the reflective stub 32, and the transmission line 33 constitute an impedance matching circuit (induction circuit). Note that the width of the reflective stub 32 and the length of the transmission line 33 are appropriately set according to the element resistance value and size of the resistor 34. As a result, the signal in the 10 GHz band is transmitted from the transmission line 31 to the resistor 34 through the reflection stub 32 and the transmission line 33 with almost no reflection, and therefore the signal in the 10 GHz band is removed by the resistor 34. Can do.

The high-frequency ground circuit 50 is for grounding the source S of the FET 10 with respect to a signal in the 24 GHz band.
In the present embodiment, the FET 10 has a first source terminal S1 and a second source terminal S2 as the source S. The first source terminal S1 and the second source terminal S2 are formed on the semiconductor chip by the internal wiring of the FET 10. Connected to the same source electrode.
The high-frequency ground circuit 50 includes a series circuit of a transmission line 51a and a reflective stub 52a connected to the first source terminal S1, and a series circuit of a transmission line 51b and a reflective stub 52b connected to the second source terminal S2. Yes. The reflective stubs 52a and 52b are open stubs whose tips are opened.

  If the high frequency grounding circuit 50 is designed so that the source S is grounded for signals of all frequencies (for example, the source S is directly grounded), the FET 10 easily oscillates a signal in the 10 GHz band, An output signal with a high S / N ratio (24 GHz band signal) cannot be obtained.

  Therefore, the high frequency grounding circuit 50 makes it difficult to oscillate a signal of an unnecessary frequency band, and does not serve as a ground for a signal of an unnecessary frequency band, and outputs a signal of a necessary frequency band (24 GHz band). In order to make it easy to oscillate, the grounding structure is such that it is grounded only for signals in a necessary frequency band.

  Specifically, as shown in FIG. 5, the length L7 from the source electrode of the semiconductor chip of the FET 10 to the tip of the reflective stub 52a through the internal wiring, the transmission line 51a and the reflective stub 52a, and the semiconductor chip The length L7 of the conductive path from the source electrode through the internal wiring, the transmission line 51b and the reflection stub 52b to the tip of the reflection stub 52b is approximately an odd multiple of λ / 4 with respect to the signal wavelength λ of 24 GHz. (Λ / 4 × (2n−1), where n is a natural number).

  For signals in the 24 GHz band, the front ends of the reflection stubs 52a and 52b are open surfaces, and the internal source electrode of the FET 10 has a phase of λ / 4 (2π / 4) from the front end of the reflection stubs 52a and 52b. Since it shifts, it becomes a short side. Therefore, the high frequency ground circuit 50 functions as a virtual ground circuit for signals in the 24 GHz band.

The unnecessary radio wave removing circuit 40 has the same configuration as the above-described unnecessary radio wave removing circuit 24 and the unnecessary radio wave removing circuit 30. Therefore, the unnecessary radio wave removing circuit 40 also functions as a selective attenuation unit.
In the present embodiment, the high-frequency grounding circuit 50 and the unnecessary radio wave removing circuit 40 constitute a grounding circuit for releasing the DC current supplied from the power supply 63 to the ground. Specifically, there is a conductive path from the first source terminal S1 to the ground through the transmission line 51a, the base end of the reflective stub 51a, the transmission line 41, the base end of the reflective stub 42, the transmission line 43, and the resistor 44. , A ground circuit for a DC current supplied to drive the FET 10 is configured.

  The unnecessary radio wave removing circuit 40 includes a transmission line 41, a reflection stub 42, a transmission line 43, and a resistor 44 connected to the distal end portion of the transmission line 51a or the proximal end portion of the reflection stub 52b. The resistor 44 is grounded. The unnecessary radio wave removing circuit 40 is the same as the unnecessary radio wave removing circuit 30 except that it is not connected to the power source 63 and is grounded.

  That is, the length of the conductive path from the source electrode of the semiconductor chip to the distal end of the transmission line 41 via the internal wiring, the first source terminal S1, the transmission line 51a, and the proximal end of the reflection stub 52b is 24 GHz. The length L8 of the transmission line 41 is set so that the length is an odd multiple of approximately λ / 4 with respect to the wavelength λ. The reflective stub 42 has a length L9 that is an odd multiple of approximately λ / 4 with respect to a signal wavelength λ of 24 GHz.

  Further, the leading end of the transmission line 43 from the source electrode of the semiconductor chip via the internal wiring, the first source terminal S1, the transmission line 51a, the base end of the reflection stub 52b, the base end of the transmission line 41 and the reflection stub 42. The conductive path (induction circuit) leading to (1) constitutes an impedance matching circuit for impedance matching between the source electrode of the FET 10 and the resistor 44 in the 10 GHz band. For this reason, the length L10 of the transmission line 43 is determined in consideration of the transmission lines 51a, 41 and the like.

  With this configuration, when an unnecessary 10 GHz band signal is sent to the high frequency ground circuit 50 together with a DC current, the 10 GHz band signal is drawn into the unnecessary radio wave removing circuit 40 by the induction circuit, and consumed and removed by the resistor 44 as heat. can do. As a result, it is possible to reliably suppress amplification and oscillation of a signal in the 10 GHz band, which is likely to be a noise component, between the gate G and the source S of the FET 10, so that an output signal with a high S / N ratio is obtained. (24 GHz band signal) can be obtained.

  In the present embodiment, the unnecessary radio wave removing circuit 40 is connected only to the first source terminal S1 of the FET 10. However, the present invention is not limited to this, and both the first source terminal S1 and the second source terminal S2 are separately provided. Alternatively, the same unnecessary radio wave removal circuit 40 may be connected.

An output circuit 60 that functions as an impedance matching circuit is connected to the drain D of the FET 10. The output circuit 60 is connected to the antenna 4 and the mixer circuit 6 as shown in FIG.
As the output circuit 60, for example, a DC cut filter or the like may be further connected in order to block transmission of a DC voltage from the power source 63 to the antenna 4 or the like.

Next, the operation of the microwave sensor 1 of the present embodiment will be described.
When power is supplied from the power supply 63 as described above, the FET 10 generates signals including various frequency signals, and these signals flow to the gate G and are transmitted to the selective amplification and attenuation circuit 20. Here, when attention is paid to a signal of 10 GHz band and a signal of 24 GHz band, when these signals are returned from the output part (drain D) of the FET 10 to the input part (gate G), the selective amplification attenuation circuit 20 is directed downstream. Transmit to.

The signal in the 24 GHz band is reflected in the direction of the gate G by the dielectric resonator 22b as the first reflecting means.
On the other hand, the signal in the 10 GHz band is not reflected by the dielectric resonator 22b, and is directed toward the front end portion 22c of the gate transmission line 22a together with a part of the signal in the 24 GHz band that has not been reflected by the dielectric resonator 22b. And transmit.

  The signal in the 24 GHz band transmitted downstream from the dielectric resonator 22b is reflected by the tip 22c of the gate transmission line 22a as the second reflecting means and reflected in the direction of the gate G (see arrow C). . As a result, the signal in the 24 GHz band that has not been completely reflected by the dielectric resonator 22b can be returned to the gate G, so that the signal in the 24 GHz band can be amplified more efficiently by performing amplification and oscillation of the signal in the 24 GHz band. Strength can be increased.

  On the other hand, the signal in the 10 GHz band is guided from the gate transmission line 22a to the unnecessary radio wave removal circuit 24 impedance-matched to the gate transmission line 22a, and is consumed and removed by the unnecessary radio wave removal circuit 24 as heat. Further, signals of other frequencies excluding signals in the 24 GHz band also flow into the unnecessary radio wave removing circuit 24 and are removed. That is, signals other than the 24 GHz band (especially signals in the 10 GHz band) are attenuated without being amplified during amplification and oscillation of the signals in the 24 GHz band.

  At this time, the signal in the 24 GHz band is blocked from flowing into the unnecessary radio wave removing circuit 24 by the inflow blocking means including the transmission line 24a and the reflection stub 24c, so that the signal in the 24 GHz band is not removed but the second reflecting means. Is returned to the direction of the gate G. Furthermore, in the present embodiment, the unnecessary radio wave removing circuit 24 is connected to the gate transmission line 22a in a direction orthogonal to the signal flow direction of the gate transmission line 22a, so that signals in the 24 GHz band can be removed. It is difficult to flow into the circuit 24.

  The signal in the 24 GHz band returned to the gate G is amplified by the FET 10 and output from the drain D. A part of the output signal is returned to the gate G through the feedback circuit, and is again selectively amplified and attenuated. 20 is transmitted. As a result, the signal in the 24 GHz band is repeatedly amplified and oscillated by the cooperation of the reflection circuit 22 and the FET 10. A signal in the 24 GHz band amplified to a predetermined value is transmitted from the drain D, which is the output part of the FET 10, to the antenna 4 and the mixer circuit 6 through the output circuit.

  Thus, in the microwave sensor 1 of the present embodiment, an unnecessary frequency band signal (in this example, a signal in the 10 GHz band) having a high gain due to the characteristics of the FET 10 is amplified and removed by the noise cut filter. Instead, in the amplification step by the FET 10, the signal in the 10 GHz band is removed without amplifying the signal in the 24 GHz band while amplifying the signal in the 24 GHz band. With this configuration, in this embodiment, it is possible to output a 24 GHz band signal generated by power saving to the outside without being attenuated by the noise cut filter.

In this embodiment, since the high frequency grounding circuit 50 suitable for the 24 GHz band is provided in the source S, the source electrode of the semiconductor chip in the FET 10 can be maintained in a short state with respect to the signal of the 24 GHz band. it can. Thereby, the FET 10 can efficiently oscillate a signal in the 24 GHz band.
On the other hand, for a signal in a frequency band other than the 24 GHz band (especially a signal in the 10 GHz band), the source electrode of the semiconductor chip in the FET 10 is not short-circuited. It becomes difficult to amplify.

  In the present embodiment, since the unnecessary radio wave removal circuit 40 is attached to the high-frequency ground circuit 50, unnecessary signals other than the 24 GHz band (particularly, signals in the 10 GHz band) are drawn into the unnecessary radio wave removal circuit 40 and attenuated. be able to. At this time, since the unnecessary radio wave removing circuit 40 is configured not to flow in a signal of 24 GHz band, the unnecessary radio wave removing circuit 40 does not remove the signal of 24 GHz band.

  Thus, in the present embodiment, both the selective amplification attenuation circuit 20 that is a signal amplification circuit and the unnecessary radio wave removal circuit 40 that constitutes the ground circuit for the DC current do not attenuate the signal in the 24 GHz band. Since the selective attenuating means for attenuating the signal in the 10 GHz band is provided at the gate, the resonance of the noise signal between the gate G and the source S of the FET 10 can be effectively suppressed.

In the above embodiment, the unnecessary radio wave removing circuits 24 and 40 have two functions as an unnecessary signal removing unit and an inflow blocking unit. However, the present invention is not limited to this, and only the function of the unnecessary signal removing unit is provided. You may comprise as follows.
In this case, the unnecessary radio wave removing circuit 24 can be configured by a series circuit of a transmission line and a resistor 24d connected between the transmission line 22a and the ground. In this series circuit, the transmission line between the transmission line 22a and the resistor 24d is impedance matched to the 10 GHz band signal so that the 10 GHz band signal can be easily drawn into the resistor 24d through the transmission line. It is done. The unnecessary radio wave removing circuit 40 is configured by a series circuit of a transmission line and a resistor 44 between the first source terminal S1 and the ground, which passes through the distal end portion of the transmission line 51a or the proximal end portion of the reflective stub 52a. Can do. In this series circuit, the internal wiring and the transmission line between the source electrode and the resistor 44 are adapted to the 10 GHz band signal so that the signal in the 10 GHz band can be easily drawn into the resistor 44 through the internal wiring and the transmission line. Impedance matching is taken.

  The microwave sensor 1 of the present embodiment can be applied to an object detection sensor for indoor watering equipment. The indoor watering device is, for example, an automatic flushing machine, a toilet seat mechanism, or the like, and the microwave sensor 1 can be used to determine use by the user. The microwave sensor 1 according to the present embodiment can be suitably used in an indoor watering device with a short determination distance to an object because the intensity of an output radio wave of 24 GHz is weak.

DESCRIPTION OF SYMBOLS 1 Microwave sensor 2 Oscillator 4 Antenna 6 Mixer circuit 10 FET (high frequency semiconductor component)
12 High-frequency oscillation circuit 20 Selective amplification attenuation circuit (signal amplification circuit)
22 reflection circuit 24 unnecessary radio wave removal circuit 30 high frequency grounding circuit 40 unnecessary radio wave removal circuit 50 high frequency grounding circuit
60 Output circuit 63 Power supply

Claims (4)

A microwave sensor configured to output radio waves of a first specific frequency to the outside,
A high-frequency semiconductor component configured to amplify a signal having a second specific frequency different from the first specific frequency;
A signal amplifying circuit connected to the high-frequency semiconductor component and configured to amplify the signal of the first specific frequency together with the high-frequency semiconductor component;
A ground circuit that is connected to the high-frequency semiconductor component and releases the current supplied to the high-frequency semiconductor component to the ground,
Each of the signal amplification circuit and the ground circuit attenuates the signal of the second specific frequency band without attenuating the signal of the first specific frequency band among the signals generated by the high frequency semiconductor component. A microwave sensor, comprising: a selective attenuating means configured to cause The selective attenuation means includes
Unnecessary radio wave removing means configured to attenuate the signal of the second specific frequency band;
Among the signals generated by the high-frequency semiconductor component, inflow prevention means for preventing the signal of the first specific frequency from flowing into the unnecessary radio wave removing means,
The microwave sensor according to claim 1, further comprising: The ground circuit includes a virtual ground circuit for the signal of the first specific frequency,
3. The microwave sensor according to claim 2, wherein the selective attenuation means provided in the ground circuit is provided so as to branch from a transmission line extending from the high-frequency semiconductor component to the virtual ground circuit. The inflow blocking means includes a stub circuit adapted to the signal of the first specific frequency;
The unnecessary radio wave removing means is connected to the stub circuit, a resistor for attenuating the signal of the second specific frequency, and an induction circuit for inducing the signal of the second specific frequency to the resistor The microwave sensor according to claim 3, further comprising:

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