WO2001052344A1

WO2001052344A1 - Ceramic bandstop monoblock filter with coplanar waveguide transmission lines

Info

Publication number: WO2001052344A1
Application number: PCT/US2001/001285
Authority: WO
Inventors: Truc Hoang; Antonije Djordjevic
Original assignee: Cts Corporation
Priority date: 2000-01-14
Filing date: 2001-01-16
Publication date: 2001-07-19

Abstract

In a ceramic block filter having multiple resonators (241, 245, 150, 255), conductive electrodes called coplanar waveguide transmission lines (243) are placed on the top surface of a ceramic block filter in proximate relation to isolation ground structures, such as isolation holes, ground isolation holes (211, 221, 231), ground fingers (237, 247, 270) and top surface ground planes (252). By placing the top surface conductive electrodes on the top surface of a ceramic block in proximate relation to these ground structures, the frequency response of the surface mount ceramic block filter may be enhanced while maintaining or enhancing the desired output energy level for the filter. For instance, the present invention provides a filter with lower insertion losses in the bandpass region, minimized transition bands between the bandpass and bandstop cut-off frequencies, and greater rejection in the bandstop region.

Description

CERAMIC BANDSTOP MONOBLOCK FILTER

WITH COPLANAR WAVEGUIDE

TRANSMISSION LINES

Technical Field of the Invention

This invention relates to electrical ceramic monoblock filters used in high frequency telecommunication applications. More particularly, this invention relates to a ceramic, multi-stage bandstop filter and duplexer.

BACKGROUND OF THE INVENTION

The Fundamentals of Filters

The term filter as used in the telecommunications field was derived from optical science, in which different colored transparent materials were used to block certain light components (colors) from white light (white light is made up of different colored lights with varying wavelengths or, equivalently, frequencies). The "filtering" or separation of one component from another was based on the spectral content of the filtered light component.

All electrical signals that vary as a function of time may be represented by a frequency distribution curve disclosing frequency per respective energies. These electrical signals may be such real- world signals as those representing speech or dramatic scenes. In order to be graphically represented, these signals are converted by appropriate energy conversion devices from their original physical forms into electrical form. For speech, as an example, a transducer in a microphone converts speech from its natural energy form of acoustic pressure waves into a time-varying electrical current or voltage waveform. In addition to such natural signals, other signals mathematically defined using the elementary functions of algebra, trigonometry, and calculus, can be related by extension to the properties of the natural signals encountered in a telecommunications system. The following situations provide oppormnities for the application of electrical filters.

1. To shape the frequency spectrum of a signal. If the original signal spectrum is inappropriate for later processing, a "prewhitening" or "band- limiting" filter, is applied to the signal.

2. To select or separate one signal from others. This is the classical application of electrical filters in telecommunications, and its invention led to the implementation of analog carrier systems in the decades from about 1920 to 1950, using the principle of multiplexing a number of channels on a common transmission signal. The separation of signals also occurs when a transmitter and a receiver are duplexed on the same ceramic block filter.

3. Improvement of signal-to-noise ratios. Where overlap of signal spectra prevents the separation of a desired signal from other interfering signals or noise, filters can be applied to improve the signal-to-noise ratio of the desired signal over the interference.

The present application focuses primarily on the second category of filters. That is, it is often desirable in communication circuits to insert a network that will freely pass currents of one band of frequencies but that will greatly attenuate (stop or decrease) currents of frequencies outside this selected band of frequencies. Such selective networks are sometimes called electric filters because they separate one wavelength signal from many signals carried upon a carrier wave. Accordingly, the function of a filter is to modify the frequency content of a signal in a desired manner. Types of Filters

Filters are generally grouped as either lowpass, highpass, bandpass, or bandstop filters based upon the desired frequency response. Lowpass filters suppress electrical signals above a particular desired cutoff frequency, passing only signals below, or lower than, the cutoff frequency. An ideal lowpass filter is one in which the bandpass extends from w ^*■= 0 to = w₀ where w₀ is known as the cutoff frequency.

0 w 0 The lowpass filter passes all frequencies up to a cutoff frequency and then attenuates, or suppresses, all frequencies above this cutoff frequency. From a practical viewpoint, the reactances of the inductors are low at low frequencies, and they readily pass such frequencies. Also, the reactance of the capacitor is low to high frequencies, and it tends to shunt high frequencies.

Highpass filters suppress electrical signals below a particular cutoff frequency, passing only signals above, or higher than, the cutoff frequency. An ideal highpass filter is the complement of the lowpass filter in that the frequency range from 0 to w₀ is suppressed or attenuated, while the signals from w₀ or above are passed.

0 w 0 f

Accordingly, the highpass filter passes all frequencies from a cut-off value, vv₀, up to very high values and attenuates all frequencies below the cut-off value. From a practical point of view, the series capacitor readily passes the high frequencies and the shunt-connected inductor bypasses the low frequencies so that they do not reach the load on the circuit.

Bandpass filters pass electrical signals between two cutoff frequencies. An ideal bandpass filter is one in which frequencies extending from w to w₂ are passed, while all other frequencies are suppressed. These filters are known to provide attenuation of signals having frequencies outside of a particular frequency range and to pass signals having frequencies within the particular frequency range of interest.

0 w. w. f

A bandstop filter suppresses electrical signals between first and second cutoff frequencies. The ideal bandstop filter is the complement of the bandpass filter where the frequencies from w, to w₂ are stopped and all other frequencies are passed.

0 w w. f

The frequency response curves provided in the explanations above use ideal (or square-edged) wave forms. In the real world, however, frequency response curves do not have square-edged transitions. In fact, a real-world response curve has rounded transitions because attenuation losses deform the ideal curve. Loss and attenuation characteristics must be considered in a real- world curve analysis.

A real-world frequency response curve (dB vs. freq.) for a bandstop filter is shown below.

This response curve shows attenuation charted against frequency, and identifies frequency ranges where: 0 to w, define the lower bandpass, w₂ to ∞ define the upper bandpass w₃ to w₄ define the bandstop, and Wj to w₃, and w₄ to w₂ define the transition bands. An optimum filter design attempts to minimize the width of the transition bands by sharpening the transition around the intended cut-off frequencies — in essence, attempting to minimize unintended attenuation and make the curve approximate the square-edged transitions of the ideal waveforms. In order to minimize the width of the lower transition band, one attempts to design a filter that will steepen the transition curve response from the w, frequency of the lower bandpass to the vv₃ frequency of the bandstop. Additionally, in order to minimize the upper transition band, one attempts to design a filter that will steepen the ascending portion of the response curve from the vv₄ frequency to the vv₂ frequency of the upper bandpass. Additionally, insertion loss is incurred when attenuation occurs in the bandpass regions. In the above example, any losses or signal attenuation occurring in the region from 0 to w, and vv₂ to ∞ (the lower and upper bandpass regions) could be considered an insertion loss. The optimum filter design would attempt to minimize insertion losses and thereby pass as much of the intended bandpass signal as possible. Surface Mount Devices

Printed circuit board wiring technology, although developed during the Second World War, first gained widespread acceptance in the 1960s. At that time electronic circuitry was assembled from discrete components that required relatively few connections to the board. Early integrated circuits rarely employed more than 16 leads, and board-insertion assembly technology (in which component leads were inserted and soldered into holes through the board) could easily accommodate the demands of the day. With the advent of the microprocessor and the growth of computer technology, circuit complexity has increased to the point that board-insertion assembly techniques are no longer adequate. Some types of digital integrated circuits, for example, must make well over 100 connections to the board. Packages with leads on 0.100-in (2.54-mm) centers become extremely inefficient in a board-insertion assembly.

Surface mount technology (SMT) was developed in part to overcome the limitations of existing techniques. Unlike the board-insertion assembly components, surface mount components are soldered directly to the board surface. Although the difference may at first seem insignificant, this change offers a number of advantages, including smaller size, lower weight, better electrical performance, and reduced cost.

Various approaches have been used to mount components to the surface of a circuit board since the inception of the printed wiring concept. The integrated circuit flatpack, for example, was the first package designed to house integrated circuits and is a true surface mount product. Earlier types of package designs were adapted from discrete semiconductor packages.

Surface mounting has been the predominant assembly method in the ceramic hybrid industry for many years because of the small physical size and improved performance it affords. It has also been popular in high-frequency circuits, where the lower parasitic reactances provide a clear advantage over prior board-insertion assembly designs.

While SMT has evolved from this background, it is not simply a new application of old technology. The term "surface mount technology, " as it has come to be known in the industry, is concerned with cost-effective methods for mounting components to the surface of printed wiring boards (PWBs) or ceramic substrates in an automated fashion. It is characterized by the fact that solder is employed to form both electrical and mechanical connections from component to board, thus distinguishing it from chip-and-wire or conductive epoxy methods of assembly.

By incorporating SMT into product designs, significant potential benefits can be obtained. For instance, surface mount assemblies can be made considerably smaller and lighter than equivalent board-insertion assembly circuits. Size reductions in component size are commonly realized. The size of the component is frequently limited by packaging requirements rather than by the functional device itself. For board-insertion assembly components, leads must be rugged enough to survive the insertion process without damage. Drilling and imaging tolerances on the printed wiring board limit how closely these leads may be spaced. This, in turn, limits how small component packages may be made in board-insertion assemblies.

In contrast, many SMT device types have no leads at all. Instead, the metallized ends of the components themselves serve as the connections to the board. Even when leads are employed, they can be closely spaced. As a result, component packages in SMT can be made two to five times smaller than their board-insertion assembly equivalents.

Surface Mount Ceramic Dielectric Block Filters

Ceramic dielectric block filters have found wide acceptance for use in radio communications devices, particularly high frequency devices such as pagers, cellular telephones, and other telecommunications devices. The blocks are relatively easy to manufacture, are rugged and have improved performance characteristics over discrete element circuits. These SMT ceramic filters are also relatively compact compared to discrete circuits. Ceramic block filters have recently become popular in many applications because of their performance characteristics at high frequencies, their manufacturability, their reduced size (compared to discrete element circuits).

Ceramic block filters are well-suited to perform either lowpass, highpass, bandpass, and bandstop functions at high frequency ranges. These devices are particularly well-suited at high frequencies because they typically employ incremental (e.g., quarter, half, three-quarters) wavelength sections to achieve the functions of discrete components.

Although various improvements have been made in the design of ceramic block filters, many designs incorporate metallized through holes to form resonators. These devices are typically comprised of several incremental wavelength sections that are configured to filter relatively narrow band of signals.

Essentially, these adjacent capacitances accommodate coupling of more of the desired frequency signals from an input terminal to an output terminal while suppressing other undesirable signals. In a bandstop filter that suppresses signals between two frequencies, a filter that uses several cascaded stages can provide wider, more highly attenuated response than other filters. In a multistage bandstop filter, it is important to minimize the leakage and coupling from the filter input to the filter output or between non-adjacent stages. Another trend in the industry involves the use of higher frequencies at higher bands in the electromagnetic spectrum for wireless telecommunications equipment. Whereas prior art filters were required to perform in the UHF field, some newer generation wireless telecommunications equipment will operate at much higher frequencies.

The ability of any single communication device to retain its viability and utility will directly depend upon its ability to scale and operate in higher frequency ranges. As a result, ceramic block filters must not only continue to reduce their size, cost and weight, but they must also continue to scale to operate at higher frequency bands in the electromagnetic spectrum. A mass-producible monolithic bandstop filter with minimum part count which can be easily manufactured would be considered an improvement in filters. For these reasons, a ceramic filter is needed which overcomes the foregning deficiencies. It is a general object of the present invention to provide a ceramic filter which overcomes the above-mentioned shortcomings.

SUMMARY OF THE INVENTION

The present invention is a ceramic block filter having multiple quarter- wavelength resonant through holes. In order to improve the coupling of resonator stages and improve filter performance, conductive electrodes called coplanar waveguide transmission lines are placed on the top surface of a ceramic block filter in proximate relation to isolation structures, such as isolation holes, ground isolation holes, ground fingers and top surface ground planes.

By placing the top surface conductive electrodes on the top surface of a ceramic block in proximate relation to these isolation structures, the frequency response of the surface mount ceramic block filter may be enhanced while maintaining or enhancing a desired output energy level for the signals compared to other filters. For instance, lower insertion losses are achieved in the bandpass region, and transition bands are further minimized between the bandpass and bandstop cut-off frequencies. Moreover, frequency rejection is maximized in the stopband frequency band.

BRIEF DESCRIPTION OF THE DRAWINGS

The objects and features of the invention will become more readily understood from the following detailed description and appended claims when read in conjunction with the accompanying drawing in which like numerals represent like elements and in which: FIG. 1 A is the top-surface view of one embodiment of the ceramic bandstop filter;

FIG. IB is a side surface of the ceramic block filter showing the input/ output pads;

FIG. 1C is the side surface of the ceramic bandstop filter opposite FIG. IB; FIG. ID is the frequency and attenuation characteristics of the ceramic bandstop filter shown in FIG. 1A;

FIG. 2 A is a duplex ceramic block filter having a transmission bandstop filter and a receiver bandpass filter;

FIG. 2B is a side surface of the duplex ceramic block filter showing the input, output, and ground pads;

FIG. 2C is the side surface of the duplex ceramic block filter opposite the side shown in FIG. 2B;

FIG. 3 A is an exemplary ceramic block filter showing the different types of ground isolation slots on the side of the ceramic block filter before metallization; FIG. 3B is an exemplary ceramic block filter showing the different types of ground isolation slots on the side of the ceramic block filter after metallization;

FIG. 4 is a frequency response curve for a four-pole bandstop filter;

FIG. 5 is a three-pole bandstop filter having round ground isolation slots;

FIG. 6 is a three-pole bandstop filter having square ground isolation slots; FIG. 7 is a three-pole bandstop filter having slanted ground isolation slots:

FIG. 8 is a frequency response curve representative of the three-pole devices shown in FIGS. 5-7; FIG. 9 is a three-pole bandstop filter having isolation side slots on both sides of the ceramic block;

FIG. 10 is a three-pole bandstop filter having alternating isolation side slots on both sides of the ceramic block; FIG. 11 is an input/output pad capacitively tapped to a resonator and surrounded by ground fingers;

FIG. 12 is a coplanar waveguide transmission line combination with two ground fingers and a top surface ground plane;

FIG. 13 is a coplanar waveguide transmission line combination with alternating ground fingers;

FIG. 14 is a coplanar waveguide transmission line combination showing multiple ground fingers and side isolation slots;

FIG. 15 is a coplanar waveguide transmission line combination showing a ground isolation hole and ground fingers; FIG. 16 is a coplanar waveguide transmission line combination with a wrap-around design on an isolation hole and ground fingers;

FIG. 17 is a coplanar waveguide transmission line combination with alternating ground fingers extending from opposite sides of ceramic block filters; and,

FIG. 18 is an input/output pad capacitively tapped to resonant hole with linear extension and ground finger.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring now to the drawings, there is shown in Figures 1A through 1C a three-pole ceramic dielectric filter 10 having a top surface 36 and a metallized ground electrode 18 on all exterior surfaces of the ceramic block except portions of the top surface 36 and areas surrounding the input/output pads 20. Input/ output pads 20 are shown on the side surface of Figure 1A. It is understood that the location of the input/output pads 20 may be moved to other portions of the ceramic block as needed.

The input/output pads 20 are connected to the linear conductor 24 which acts as a coplanar waveguide transmission line coupled to the other input/output pad 20. The coplanar waveguide transmission line 24 is a conductive electrode that extends in proximate relation to the resonator holes 28 and 32 and isolation structures 30 running the length of the ceramic block filter 10. In this embodiment, the isolation structure 30 is an isolation hole. As is shown in Figure 1A, the coplanar waveguide transmission line 24 makes a semicircular pattern in between resonator hole 28 and isolation structure 30 and likewise makes a semicircular pattern between the isolation structure 30 and the metal resonator hole 32. A mirror image of the semicircular pattern for the coplanar waveguide transmission line 24 is shown between the resonator hole 32 and isolation hole 30 on the right side of the top surface 36 of ceramic filter

10 and the isolation hole 30 and the resonant hole 28 on the top surface 36 of ceramic filter 10.

The top surface of the ceramic filter 10 also has a metal conductive plate 22 extending from the metallized ground electrode 18. The isolation holes 30 are surrounded by metallized regions 12 which extend to the side surface ground electrode 18. The resonant hole 32 is also surrounded by a conductive region 14 which is capacitively coupled to the ground metal region. The resonant holes 28 also possess a conductive region 16 which surrounds the resonant holes. Figure IB shows the side surface of the ground electrode 18 with the input/output pads 20, and Figure 1C shows the opposite side surface with the ground electrode 18. Figure ID shows the frequency transfer function response curve 50 for the three-pole device including the response curve 50 and the three transmission zeros resulting from the three-pole device. The frequency response curve 50 in Figure ID reduces the insertion losses in the upper and lower bandpass regions through the use of a coplanar waveguide transmission line. Further, the transition from the bandpass to the bandstop are much steeper with the coplanar waveguide transmission line — which translates into a closer approximation of the ideal filter characteristic. The resonator performance is improved by isolating the resonator from other transmission pathways. This isolation reduces cross-talk between resonators over known devices. Moreover, the coplanar waveguide transmission line tightly controls the coupling of the resonator thereby providing greater rejection of the signal in the bandstop area than prior art devices. Curve 55 in Figure ID shows the return loss curve for the three-pole device shown in Figure 1A.

Figure 2A shows a duplex ceramic block filter design having a transmitter bandstop filter on the left side of the ceramic filter 100 and a receiver bandpass filter on the right side of the ceramic block filter 100. The transmitter bandstop filter on the left side of the ceramic block filter 100 is a three-pole device having three resonator holes 128, 132 and 128 situated in proximate relation to two isolation holes 130. The isolation holes are surrounded by conductive regions 1 12 and the resonator holes 128 are surrounded by conductive regions on the top surface 116. The middle resonator hole 132 is surrounded by a conductive region 114.

The input/output pad 120 on the transmitter bandstop filter is coupled to the coplanar waveguide transmission line 124 which forms a semicircular pattern between each resonator hole and isolation hole in the transmitter bandstop. That is, coplanar waveguide transmission line 124 is configured to have a semicircular pattern between the resonator hole 128 and isolation hole 130 and between the isolation hole 130 and the resonator hole 132. A conductive plate 122 is also located on the top surface and is connected to the ground electrode which surrounds the ceramic filter 118. The ground pad 121 is located between the input/output pads 120 on the side surface.

The ground pad 121 is coupled to a metallized region 140 which surrounds the first resonator hole on the receiver bandpass filter. A series of three other resonator holes are capacitively coupled to the first resonator hole 140 and include resonator holes 145, 150 and 160 which are each surrounded by a metallized region. The resonator hole 160 is capacitively coupled to a conductor

165 which is coupled to the input/output pad 120 on the receiver bandpass filter. The top surface of the ceramic block filter 136 is designed to perform to the desired frequency.

Figure 2B shows the side surface of the ceramic block filter having input/ output pads 120 on either side of the ground pad 121. Figure 2C shows the opposite side of the ceramic block filter having a ground electrode 118.

Figure 3A is an exemplary ceramic block filter (without metallization) having three different types of groove designs for use as isolation structures in ceramic block filters. The first isolation groove 210 is a circular groove extending across the entire length of the ceramic filter. The slanted groove 220 extends the entire length of the ceramic block filter, and the notched or square slot 230 extends the entire length of the ceramic block filter. A complementary groove pattern 235 of a circular design (or other design, e.g. , square, slotted or notched) may be configured on the opposite side of the ceramic block to the groove patterns 210, 220 or 230 shown in the ceramic block filter 3A.

This groove pattern on the opposite side of the ceramic block may also be used to perform an isolation function similar to the isolation holes or the isolation groove patterns 210, 220 and 230. The hole patterns in Figure 3A vary depending on the desired frequencies and can include the circular pattern 240, a semicircular groove pattern 240 aligned horizontally with the length of the top surface of the ceramic pattern or a semicircular or elliptical pattern 250 which is peφendicular to the length of the top surface of the ceramic block filter. Various combinations of groove patterns may be used to accomplish various frequency curve modeling.

Figure 3B shows the example ceramic block filter after metallization and includes a circular groove pattern 211, a slanted slot pattern 221 and a square or slotted pattern 231 which extends partially up the side of the ceramic block filter. These slots are coated with a ground electrode 225 which surrounds the sides of the block filter (except around the input/output pads) and bottom surface of the ceramic block filter 205.

In Figure 3B, the input/ output pad 222 is coupled to the coplanar waveguide transmission line 243 which extends across the top surface and around various isolation grounding structures such as the grounding fingers 247 and 270, the grounding notch pattern 261 or the metallized ground area with the ground finger 252. Resonant holes 241 , 245, 250 and 255 produce a four-pole filter design wherein each of these resonator holes is surrounded by a metallized region 242, 246, 251 and 260, respectively. The transmission line 243 is coupled to the opposite input/ output pad 222 after extending across the top surface of the ceramic block.

The coplanar waveguide transmission line 243 extends in a semicircular loop next to the grounding finger 237. Further, the coplanar waveguide transmission line 243 extends across the length of the grounding finger 247 and surrounds the grounding finger 270 in a semicircular pattern. This semicircular pattern is repeated on the opposite side of the resonator hole 250. The coplanar waveguide transmission line 243 also extends across the length of the grounding finger 251 extending from the conductive region 252 on the right side of the ceramic filter 205. The isolation structures 211, 221, 231 do not extend across the entire length of the ceramic block, but the structures have a vertical axis which is defined as the axis extending along the length of the block in alignment with the length of the groove patterns. The frequency response curve for the four-pole device shown in Figure 3A and 3B can be shown in Figure 4 along curve 300. As compared to prior art devices the response curve 300 shows improved transition areas between the bandpass and bandstop cut-off frequencies, improved insertion loss and increased rejection in the bandstop region. Figure 5 shows a semicircular notched isolation groove pattern 530 on the side of the ceramic block filter 500. Also shown on Figure 5 is a coplanar waveguide transmission line 510 which extends from the input/ output pads 526. The transmission line 510 extends in a semicircular pattern between the resonator holes 515, 521 and 539. Each resonator hole 515, 521 and 539 is surrounded by a conductive region. The ground electrode 520 surrounding the side surface and bottom surface of the ceramic block filter extends onto the top surface with grounding extensions 540 and a separate conductive plate on the top surface 525. Figure 6 shows a square slotted ceramic block filter having the square slot regions 630. The ceramic block filter is covered with a conductive electrode 620 which extends onto the top surface of the ceramic block filter at conductive regions 625 and 640. The metallized regions on the top surface of the ceramic block filter 600 extending from the side metallized region include the grounding fingers which extend linearly onto the top surface 640 and a U-shaped metallized region on the top surface 625 which surrounds the coplanar waveguide transmission line 610 and forms a "U" shape with linear projections on either side of a parallel linear conductor extending between the resonator holes 635 and 621.

The coplanar waveguide transmission line 610 extends from the input/ output line 626 on the side surface of ceramic block filter 600. As is shown in Figure 6, the coplanar waveguide transmission line 610 extends in a semicircular pattern on the top surface of the ceramic block between resonant holes 635 and 621 and resonator hole 615. The resonator holes 635, 621 and 615 are surrounded by isolated conductive regions. Figure 7 shows a slanted slot pattern isolation groove 730 on the side surface of a three -pole ceramic filter design. The ceramic filter 700 is surrounded by metallized coat 720 and includes three resonator holes 735, 721 and 715, each surrounded by an isolated conductive region on the top surface of ceramic block filter 700. The input/output pads 726 are coupled to the coplanar waveguide transmission line 710 which is configured in a semicircular pattern between each resonator hole 735, 721 and 715. Conductive region 740 extends from the ground electrode 720 onto the top surface and is surrounded by the coplanar waveguide transmission line 721. The configuration of 740 is a linear conductive region extending onto the top surface of ceramic block filter 700. The conductive regions on the top surface of the ceramic block filter 700 also includes metallized regions 725 which are configured in a U-shaped configuration having two linear projections and a horizontal projection 725.

Each of the isolation grooves in Figures 5, 6 and 7, which include circular groove 530, square slotted groove 630 and slanted slot groove 730, act as isolation structures for the resonant holes on each of the three-pole devices. Each of these slots are only extended partially across the length of the ceramic block filter, but could occupy the entire length of the ceramic block filter if desired frequency range requires such a configuration. Even though the isolation structures extend partially along the length of the ceramic block, each isolation structure has a vertical alignment along the axis of the groove pattern along the length of the ceramic filter. At the very least, the coplanar waveguide transmission line extends in between the resonator hole and the isolation structure's vertical alignment along the length of the ceramic block. In Figure 8, the frequency response curve 800 shows the three transmission zeros along the frequency response curve. The specifics of the response curve will vary slightly depending on the specific configuration of isolation structures, but each of these transmission zeros is representative of the response curve obtained in Figures 5, 6 and 7 through the use of the different isolation slot patterns and the coplanar waveguide transmission line on the top surface of the ceramic block filter. Each of these filters could use combinations of different slot designs on the side surface of the ceramic block filter with corresponding adjustments in the conductive regions on the top surface. For instance, the conductive regions 525 shown on the top surface of Figure 5 could be used instead of the conductive regions 625 shown in Figures 6 or 725 shown in Figure 7. Likewise, corresponding region 740 which include linear projections could be used instead of the projections which are complementary to the linear electrodes 740 such as the electrodes 725 or 625 in Figures 7 and 6, respectively. Figure 9 shows a three-pole ceramic filter design 900 having three-resonant holes 915, 921 and 940 surrounded by conductive regions which are isolated from the ground electrode 920. Isolation grooves 930 are circular and extend the entire length of the ceramic block filter. The isolation grooves 930 are placed on both sides of the ceramic block filter 900. Additionally, the isolation grooves 930 extend on both sides of the ceramic block filter to provide a unique response curve for the ceramic block filter shown in Figure 9. The coplanar waveguide transmission line 910 extends from the input/output pad 926 to the corresponding input/output pad 926 on the side surface of ceramic block filter 900. As shown in Figure 9, the coplanar waveguide transmission line 910 makes a semicircular loop between the resonator hole 915 and the isolation grooves 930. the isolation grooves 930 and the resonator hole 921 , the resonator hole 921 and the isolation grooves 930, and the isolation grooves 930 and the resonator hole 940.

The ceramic block filter 1000 in Figure 10 shows alternating circular groove patterns 1030 having no corresponding pairing of isolation grooves on the opposite side of the ceramic block filter. The isolation grooves 1030 extend the entire side surface of the ceramic block filter 1000. Resonator holes 1015 and 1021 are surrounded by isolated conductive regions such as region 1035. Linear metallized ground fingers 1025 extend onto the top surface and are placed in a linear relationship with the coplanar waveguide transmission line 1010. The coplanar waveguide transmission line 1010 makes a semicircular pattern between the resonator holes 1015 and 1021 and around the isolation groove 1030. This pattern is repeated on the right side of the ceramic block filter 1000.

Figure 11 shows a specific resonator hole 11 15 surrounded by a conductive region 1135 on ceramic block 1100. A metallized ground finger 1125 extends linearly in a notched and alternating pattern with ground pattern 1140. The coplanar waveguide transmission line 1110 extends from the input/ output line 1 126 from the side surface of the ceramic block filter 1100 to the adjoining resonator holes (not shown). The coplanar waveguide transmission line 1110 has a linear extension on both sides of the resonator hole 1115 and partially surround the resonator hole in a semicircular pattern before aligning itself linearly with both the ground electrode fingers 1125 and 1140.

Figure 12 shows the coplanar waveguide transmission line arrangement where coplanar waveguide transmission line 1210 extends in a linear relationship to the ground fingers 1225 and surrounds the grounding electrode 1240 in a semicircular pattern.

Figure 13 shows the linear relationship and proximate configuration for the coplanar waveguide transmission line 1310 extending in a linear relationship around grounding finger 1325 in a similar type of semicircular pattern. The coplanar waveguide transmission line is also shown to be extending in a linear pattern next to the grounding finger 1340.

In Figure 14, the coplanar waveguide transmission line 1410 extends between two isolation grooves in a circular pattern which extend the entire length of the ceramic block filter. The metallized ground finger 1425 includes a broad metallized region and a ground finger 1435 on the top surface of the ceramic block. The coplanar waveguide transmission line 1410 is linearly aligned with the grounding finger 1425 and surrounds the grounding finger 1435 in a semicircular pattern. Figure 15 discloses an isolation hole 1515 surrounded by a metallized region 1535. Ground fingers 1540 extend on either side of the isolation hole 1515. Between the grounding fingers 1540 and the metallized region 1535 surrounding the isolation hole 1515 is the coplanar waveguide transmission line 1510 which surrounds the isolation hole 1515 in a semicircular pattern and is linearly aligned with the grounding fingers 1540.

Figure 16 shows the coplanar waveguide transmission line 1610 extending between and circularly surrounding the resonator hole 1615 and the conductive region 1640 surrounding the resonator hole. Grounding fingers 1640 extend linearly on the top surface of the ceramic filter shown in Figure 16. Broad conductive regions 1625 surround the opposite side of the top surface from the grounding fingers 1640. The coplanar waveguide transmission line 1610 extends linearly along the ground fingers 1640 and circularly surrounds the resonator hole 1615. The metallized region 1640 surrounding the resonator hole 1615 extends around the semicircular arrangement formed by the coplanar waveguide transmission line 1610.

Figure 17 discloses a triple semicircular pattern where alternating grounding fingers 1725 and 1730 are placed in proximate relation to a coplanar waveguide transmission line 1710 which forms semicircular patterns between these grounding fingers. Figure 18 discloses resonator hole 1815 surrounded by a conductive region

1835 with a broad metallized region 1875 extending toward the conductive ground electrode extending on the top surface of the ceramic block region. The coplanar waveguide transmission line 1813 extends from the I/O pad 1820 and includes linear fingers 1840 extending in a semicircular pattern around the linear ground pattern 1825. A broad metallized ground region 1845 is situated on the opposite side of the coplanar waveguide transmission line 1813.

Although specific embodiments of the invention are disclosed in the above description, different elements may be configured differently to provide for slightly different frequency response curves. Although the present invention has been described and illustrated in detail, it is clearly understood that the same is by way of illustration an example only and is not to be taken by way of limitation. The spirit and scope of the present invention is limited only by the terms of the appended claims.

Claims

CLAIMS:

1. An integrated dielectric filter comprising: a dielectric ceramic block having a plurality of resonant holes extending from a top exterior surface of the block to a bottom exterior surface of the block; electrodes on interior surfaces of the resonant holes; a ground electrode on all exterior surfaces of the block except for portions of the top exterior surface and areas surrounding the input/output pads; at least one isolation structure coupled to said ground electrode; input/output electrodes coupled to the ceramic block; a conductive electrode on the top surface of the ceramic block coupled to at least one input/output pad and extending between one of said resonator holes and the at least one of said isolation structure.

2. The dielectric filter of Claim 1 further comprising a conductive plate on the top surface of the ceramic block coupling one end of the isolation structure to the ground electrode.

3. The dielectric filter of Claim 1 further comprising a conductive ground plate extending onto the top surface of the ceramic block and coupled to the ground electrode.

4. The dielectric filter of Claim 1 further comprising a conductive resonator plate on the top surface of the ceramic block surrounding the end of each resonator hole.

5. The dielectric filter of Claim 1 further comprising the input/output electrodes mounted on the side of the ceramic block.

6. The dielectric filter of Claim 1 further comprising the conductive electrode coupled to both input/output pads on the ceramic block.

7. The dielectric filter of Claim 1 further comprising the conductive electrode extending between each of said resonator holes and each isolation structure.

8. The dielectric filter of Claim 7 further comprising a conductive plate coupling one end of the isolation structure to the ground electrode.

9. The dielectric filter of Claim 7 further comprising a conductive ground plate extending onto the top surface of the ceramic block and coupled to the ground electrode.

10. The dielectric filter of Claim 7 further comprising a conductive resonator plate on the top surface of the ceramic block surrounding the end of each resonator hole.

11. The dielectric filter of Claim 7 further comprising the input/output electrodes mounted on the side of the ceramic block.

12. The dielectric filter of Claim 7 further comprising the conductive electrode coupled to both input/output pads on the ceramic block.

13. The dielectric filter of Claim 1 further comprising the conductive electrode extending between one of said resonator holes and a vertical axis of an isolation structure.

14. The dielectric filter of Claim 13 further comprising the conductive electrode extending between each of said resonator holes and the vertical axis of each isolation structure.

15. The dielectric filter of Claim 13 further comprising a conductive plate coupling one end of the isolation structure to the ground electrode.

16. The dielectric filter of Claim 13 further comprising a conductive ground plate extending onto the top surface of the ceramic block and coupled to the ground electrode.

17. The dielectric filter of Claim 13 further comprising a conductive resonator plate on the top surface of the ceramic block surrounding the end of each resonator hole.

18. An integrated dielectric duplexer comprising: a dielectric ceramic block having a plurality of resonant holes extending from a top exterior surface of the dielectric block to a bottom exterior surface of the block; electrodes on interior surfaces of the resonant holes; a ground electrode disposed on the exterior surfaces of the block except for portions of the top surface of the dielectric block and areas surrounding the input/output pads; at least one isolation structure coupled to said ground electrode; input/output electrodes coupled to the ceramic block; a ground electrode coupled to a transmitter and a receiver section of the duplexer; a conductive electrode on the top surface of the ceramic block coupled to at least one input/output pad and extending between one of said resonator holes and the at least one of said isolation structure.

19. The dielectric duplexer of Claim 18 further comprising a conductive plate on the top surface of the ceramic block coupling one end of the isolation structure to the ground electrode.

20. The dielectric duplexer of Claim 18 further comprising a conductive ground plate extending onto the top surface of the ceramic block and coupled to the ground electrode.

21. The dielectric duplexer of Claim 18 further comprising a conductive resonator plate on the top surface of the ceramic block surrounding the end of each resonator hole.

22. The dielectric duplexer of Claim 18 further comprising the input/output electrodes mounted on the side of the ceramic block.

23. The dielectric duplexer of Claim 18 further comprising the conductive electrode coupled to both input/output pads on the ceramic block.

24. The dielectric duplexer of Claim 18 further comprising the conductive electrode extending between each of said resonator holes and each isolation structure.

25. The dielectric filter of Claim 24 further comprising a conductive plate coupling one end of the isolation structure to the ground electrode.

26. The dielectric filter of Claim 24 further comprising a conductive ground plate extending onto the top surface of the ceramic block and coupled to the ground electrode.

27. The dielectric filter of Claim 24 further comprising a conductive resonator plate on the top surface of the ceramic block surrounding the end of each resonator hole.

28. The dielectric filter of Claim 24 further comprising the input/output electrodes mounted on the side of the ceramic block.

29. The dielectric filter of Claim 24 further comprising the conductive electrode coupled to both input output pads on the ceramic block.

30. The dielectric filter of Claim 18 further comprising the conductive electrode extending between one of said resonator holes and a vertical axis of an isolation structure.

31. The dielectric filter of Claim 30 further comprising a conductive plate coupling one end of the isolation structure to the ground electrode.

32. The dielectric filter of Claim 30 further comprising a conductive ground plate extending onto the top surface of the ceramic block and coupled to the ground electrode.

33. The dielectric filter of Claim 30 further comprising a conductive resonator plate on the top surface of the ceramic block surrounding the end of each resonator hole.

34. The dielectric filter of Claim 30 further comprising the conductive electrode extending between each of said resonator holes and the vertical axis of each isolation structure.

35. An integrated dielectric filter comprising: a dielectric ceramic block having a plurality of resonant holes extending from a top exterior surface of the block to a bottom exterior surface of the block; a conductive resonator plate on the top surface of the ceramic block surrounding the end of each resonator hole electrodes on interior surfaces of the resonant holes: a ground electrode on all exterior surfaces of the block except for portions of the top exterior surface and areas surrounding the input/output pads; at least one isolation structure coupled to said ground electrode; input/output electrodes coupled to the ceramic block; a conductive electrode on the top surface of the ceramic block coupled to at least one input/output pad and extending between one of said resonator holes and the at least one of said isolation structure.

36. The dielectric filter of Claim 35 further comprising a conductive plate on the top surface of the ceramic block coupling one end of the isolation structure to the ground electrode.

37. The dielectric filter of Claim 35 further comprising a conductive ground plate extending onto the top surface of the ceramic block and coupled to the ground electrode.

38. The dielectric filter of Claim 35 further comprising the input/output electrodes mounted on the side of the ceramic block.

39. The dielectric filter of Claim 35 further comprising the conductive electrode extending between each of said resonator holes and each isolation structure.

40. The dielectric filter of Claim 39 further comprising a conductive ground plate extending onto the top surface of the ceramic block and coupled to the ground electrode.

41. The dielectric filter of Claim 39 further comprising the input/output electrodes mounted on the side of the ceramic block.

42. The dielectric filter of Claim 39 further comprising the conductive electrode coupled to both input/output pads on the ceramic block.

43. The dielectric filter of Claim 39 further comprising the conductive electrode extending between one of said resonator holes and a vertical axis of an isolation structure.

44. The dielectric filter of Claim 39 further comprising the conductive electrode extending between each of said resonator holes and the vertical axis of each isolation structure.