CN101729041A - Method and device for realizing filter in multi-rate processing - Google Patents

Abstract

The invention discloses a method and a device for realizing filter in multi-rate processing. The method comprises the following steps of: performing polynomial decomposition of a filtering process on a branch according to an interpolating factor P in conversion factors P/Q so as to acquire an up-sampling factor Pi; performing the polynomial decomposition of the filtering process on the branch according to an extracting factor Q in the conversion factors P/Q so as to acquire a down-sampling factor Qi; combining the up-sampling factor Pi and the down-sampling factor Qi; and performing anti-aliasing/anti-image filter on the combined up-sampling factor Pi and down-sampling factor Qi after determining the number of the stages N of rate conversion. The technical scheme of the invention can place a filter process on a node with a low sampling rate so as to perform the anti-aliasing/anti-image filter at a low rate and reduce the calculated amount of a system.

Description

Filtering implementation method and device in a kind of many rate processing

Technical field

The present invention relates generally to the signal processing of communication technical field, is meant filtering implementation method and device in a kind of many rate processing especially.

Background technology

When between the chip of supporting digital interface, interconnecting, can run into the different situation of interface rate between the different chips usually, change with regard to the speed that requires logarithm word interface like this, adopt the way of interpolation-anti-mirror image/anti-aliasing filter-extraction usually.

Traditional anti-mirror image/anti-aliasing filter process adopts Kaiser THE DESIGN OF WINDOW FUNCTION method, the Kaiser window function can keep very little interior ripple of band and sharp cut-off characteristics, but exponent number is often very high, and when conversion factor was very big, it is very complicated that filter will design especially.

Two kinds of methods that reduce complexity are arranged usually, a kind of employing iir filter, another kind of employing CIC (cascade integrator comb, cascaded integrator-comb) filtering in the prior art.For the IIR filtering method, though can adopt a lot of algorithms to realize approximate linear phase, transition band is than broad, and attenuation outside a channel is not enough, and approximate linear phase still has certain damage to signal; For the CIC filtering method, though can reduce the complexity of multiplication greatly, the cic filter band attenuation is very big, often need do nonlinear compensation in the back level, and CIC filtering does not fit into the merging of anti-aliasing filter and anti-mirror image filtering.

In order to reduce overhead and group delay, need to adopt the method for multilevel interpolation/extraction usually, as shown in Figure 1.Under the very big situation of conversion factor, filtering often needs to be operated on the very high sampling rate, brings very big overhead.

Summary of the invention

The embodiment of the invention proposes filtering implementation method and the device in a kind of many rate processing, filtering can be placed on the node of low sampling rate, thereby carry out anti-aliasing/anti-mirror image filtering under low rate, and reduce the amount of calculation of system.

Technical scheme of the present invention is achieved in that

Filtering implementation method in a kind of many rate processing comprises:

According to the interpolation factor P among the conversion factor P/Q branch road is carried out the multinomial decomposition of filtering, obtain up-sampling factor Pi;

According to the extraction factor Q among the conversion factor P/Q branch road is carried out the multinomial decomposition of filtering, obtain down-sampling factor Q i;

Described up-sampling factor Pi and described down-sampling factor Q i are made up, determine to carry out anti-aliasing/anti-mirror image filtering behind the progression N of rate transition.

Preferably, the difference of described up-sampling factor Pi and described down-sampling factor Q i is less than a predetermined threshold value.

Preferably, described N is less than 4.

Preferably, describedly carry out anti-aliasing/anti-mirror image filtering and be specially:

Adopt the equal-ripple filter of restricted type to carry out anti-aliasing/anti-mirror image filtering.

Preferably, the structure expression of the equal-ripple filter of described restricted type is:

Wherein, h (n) is the discrete impulse response of filter, and H (Z) is a system responses, and N is a filter order;

Characteristic according to the equal-ripple filter of described restricted type is finished the multiplexing of anti-aliasing filter and anti-mirror image filtering.

Preferably, according to the interpolation factor P among the conversion factor P/Q the multinomial decomposition that branch road carries out filtering is carried out according to following formula:

$H\left(Z\right)=\underset{p=0}{\overset{P-1}{\mathrm{\Σ}}}{H}_p\left(Z^P\right)*Z^{-(P-1-p)};$

Described H _p(Z) be the system responses of p input branch road, H (Z) is the system responses of whole prototype filter, its total P input branch road;

Wherein, $H_{P-1-k}\left(Z\right)=\underset{r=0}{\overset{R-1}{\mathrm{\Σ}}}h(r*P+k){\left(Z^P\right)}^{-r};$

Described h (r*P+k) is p-1-k the discrete impulse response on the branch road, and R is the number of the impulse sampling point on each branch road.

Preferably, according to the extraction factor Q among the conversion factor P/Q the multinomial decomposition that branch road carries out filtering is carried out according to following formula:

$H\left(Z\right)=\underset{p=0}{\overset{P-1}{\mathrm{\Σ}}}{H}_p\left(Z^P\right)*Z^{-(P-1-p)};$

Described H _p(Z) be the system responses of p output branch road, H (Z) is the system responses of whole prototype filter, its total P output branch road;

Wherein, $H_{P-1-k}\left(Z\right)=\underset{r=0}{\overset{R-1}{\mathrm{\Σ}}}h(r*P+k){\left(Z^P\right)}^{-r};$

Described h (r*P+k) is p-1-k the discrete impulse response on the branch road, and R is the number of the impulse sampling point on each branch road.

Filtering implement device in a kind of many rate processing comprises:

First resolving cell is used for according to the interpolation factor P of conversion factor P/Q branch road being carried out the multinomial decomposition of filtering, obtains up-sampling factor Pi;

Second resolving cell is used for according to the extraction factor Q of conversion factor P/Q branch road being carried out the multinomial decomposition of filtering, obtains down-sampling factor Q i;

Processing unit is used for described up-sampling factor Pi and described down-sampling factor Q i are made up, and determines the progression N of rate transition;

Anti-aliasing/anti-mirror filter, be used to carry out anti-aliasing/anti-mirror image filtering.

Preferably, the difference of described up-sampling factor Pi and described down-sampling factor Q i is less than a predetermined threshold value.

Preferably, described anti-aliasing/anti-mirror filter is the equal-ripple filter of restricted type.

Preferably, the structure expression of the equal-ripple filter of described restricted type is:

Wherein, h (n) is the discrete impulse response of filter, and H (Z) is a system responses, and N is a filter order;

The equal-ripple filter of described restricted type also is used to finish the multiplexing of anti-aliasing filter and anti-mirror image filtering.

Technical solution of the present invention is carried out the multinomial decomposition of filtering according to interpolation factor earlier, further decompose according to extracting the factor again, thereby filtering is placed on the low node of sampling rate, reduced the amount of calculation of system on the one hand, reduced requirement, reduced the influence that the finite word length effect of filter brings system sampling clock; Under low rate, carry out anti-aliasing/anti-mirror image filtering on the other hand, reduce hard-wired complexity, improve the sensitivity of system.

Further, anti-aliasing/anti-mirror filter prototype adopts the equal-ripple filter of restricted type to replace Kaiser window function of the prior art, only need fewer filter order, thereby can realize preferably with interior performance and higher attenuation outside a channel, and the equal-ripple filter characteristic according to restricted type merges design with frequency overlapped-resistable filter and anti-mirror filter, reduce the complexity of system design, reduced the memory space of amount of calculation and system.

Description of drawings

In order to be illustrated more clearly in the embodiment of the invention or technical scheme of the prior art, to do to introduce simply to the accompanying drawing of required use in embodiment or the description of the Prior Art below, apparently, accompanying drawing in describing below only is some embodiments of the present invention, for those of ordinary skills, under the prerequisite of not paying creative work, can also obtain other accompanying drawing according to these accompanying drawings.

Fig. 1 is the conversion method schematic diagram of digital interface sampling rate in the prior art;

Fig. 2 is the schematic flow sheet of the filtering implementation method preferred embodiment in a kind of many rate processing of the present invention;

Fig. 3 is decimation filter and the multiplexing schematic diagram of interpolation filter;

Fig. 4 is the structural representation of the filtering implementation method in a kind of many rate processing of the present invention;

Fig. 5 is the structural representation of the filtering implement device preferred embodiment in a kind of many rate processing of the present invention;

Fig. 6 is a resource multiplex structural representation in the tdma system;

Fig. 7 is the performance verification result schematic diagram behind the resource multiplex in the tdma system.

Embodiment

Below in conjunction with the accompanying drawing in the embodiment of the invention, the technical scheme in the embodiment of the invention is clearly and completely described, obviously, described embodiment only is the present invention's part embodiment, rather than whole embodiment.Based on the embodiment among the present invention, those of ordinary skills belong to the scope of protection of the invention not making the every other embodiment that is obtained under the creative work prerequisite.

Filtering implementation method in many rate processing that the present invention proposes is applicable to following several situation (conversion factor of supposing sampling rate is P/Q, and wherein P and Q are relatively prime, and P is an interpolation factor, and Q is for extracting the factor):

1, the down-sampled process that only contains extraction, Q=1 at this moment;

2, the sampling process that rises that only contains interpolation, P=1 at this moment;

3, P and Q are bigger, need the conversion of N (N＞1) stage speed;

4, P and Q are smaller, only need the first-rate conversion, at this moment N=1.

At communication technical field, situation 3 is a large amount of existence, so various embodiments of the present invention are the example explanation with situation 3 all, is appreciated that technical scheme of the present invention also can realize for other kind situation.

With reference to Fig. 2, show the schematic flow sheet of the filtering implementation method preferred embodiment in a kind of many rate processing of the present invention, comprise step:

Step S210, branch road is carried out the multinomial decomposition of filtering, obtain up-sampling factor Pi according to the interpolation factor P among the conversion factor P/Q.

According to the interpolation factor P among the conversion factor P/Q the multinomial decomposition that branch road carries out filtering is carried out according to following formula:

$H\left(Z\right)=\underset{p=0}{\overset{P-1}{\mathrm{\Σ}}}{H}_p\left(Z^P\right)*Z^{-(P-1-p)};$

Described H _p(Z) be the system responses of p input branch road, H (Z) is the system responses of whole prototype filter, its total P input branch road;

Wherein, $H_{P-1-k}\left(Z\right)=\underset{r=0}{\overset{R-1}{\mathrm{\Σ}}}h(r*P+k){\left(Z^P\right)}^{-r}.$

Described h (R*P+k) is p-1-k the discrete impulse response on the branch road; R is the number of the impulse sampling point on each branch road.

Step S220, branch road is carried out the multinomial decomposition of filtering, obtain down-sampling factor Q i according to the extraction factor Q among the conversion factor P/Q.

According to the extraction factor Q among the conversion factor P/Q the multinomial decomposition that branch road carries out filtering is carried out according to following formula:

$H\left(Z\right)=\underset{p=0}{\overset{P-1}{\mathrm{\Σ}}}{H}_p\left(Z^P\right)*Z^{-(P-1-p)};$

Wherein, $H_{P-1-k}\left(Z\right)=\underset{r=0}{\overset{R-1}{\mathrm{\Σ}}}h(r*P+k){\left(Z^P\right)}^{-r}.$

What described formula was different with the formula among the step S210 is the branch road number of the P representative output in this formula, H _p(Z) system responses of p output branch road of expression, H (Z) is the system responses of whole prototype filter.Described h (r*P+k) is p-1-k the discrete impulse response on the branch road; R is the number of the impulse sampling point on each branch road.

Lift an enforcement and describe, suppose that the filter prototype is 64 rank, for (16 ↑ 13 ↓) process, filter has 16 input branch roads, and 64/16=4 discrete pulse sampled point arranged on each branch road.

Step S230, described up-sampling factor Pi and described down-sampling factor Q i are made up, determine to carry out anti-aliasing/anti-mirror image filtering behind the progression N of rate transition.

With an instantiation above step being carried out an explanation, is example with P/Q=384/325, and the exponent number that obtains three grades of transversal filter prototypes is respectively: 48,24,18 rank, global design is: (16 ↑ 13 ↓) → (6 ↑ 5 ↓) → (3 ↑ 5 ↓).Pi is exactly 16/6/3, and Qi is 13/5/5.

In specific embodiment of the present invention, following principle is pressed in decomposition and combination:

1, in the rate transition process of each grade, up-sampling factor Pi and down-sampling factor Q i are approaching as far as possible, and promptly the difference of up-sampling factor Pi and described down-sampling factor Q i is less than a predetermined threshold value, to obtain Design of Filter more efficiently.

2, conversion factor should be according to the principle of successively decreasing one by one.

3, rate transition progression N is not too many, preferably less than 4.

In a preferred version, the principle that described step S210 and step S220 will follow is that the difference of the up-sampling factor Pi that obtains after decomposing and described down-sampling factor Q i is less than a predetermined threshold value, thereby guarantee in the rate transition process of each grade, up-sampling factor Pi and down-sampling factor Q i are approaching as far as possible, to obtain Design of Filter efficiently, described predetermined threshold value can design according to the actual requirements, and the present invention does not limit this.

Further, described definite rate transition progression N is not too big, and preferably N is less than 4.

Wherein, adopt the equal-ripple filter of restricted type to carry out anti-aliasing/anti-mirror image filtering.

Determine that the filter prototype adopts the equal-ripple filter of restricted type, has the factor of three considerations: ripple in (1) band, the non-linear behaviour in the decision band; (2) attenuation outside a channel, decision is to the mirror image interference and face the ability of being with interference eliminated; (3) filter order, the performance of decision transition band, in order to realize multinomial efficiently filter structure, exponent number should be the multiple (perhaps as far as possible approaching the multiple of interpolation factor) of the interpolation factor of this grade transducer.

The structure expression of the equal-ripple filter of described restricted type is:

$H\left(Z\right)={\mathrm{\Σ}}_{n=0}^{N-1}h\left(n\right)*Z^{-n};$

Wherein, h (n) is the discrete impulse response of filter, and H (Z) is a system responses, and N is a filter order.

Characteristic according to the equal-ripple filter of described restricted type is finished the multiplexing of anti-aliasing filter and anti-mirror image filtering.The equal-ripple filter that is the restricted type of described structure expression representative both can carry out anti-aliasing filter, can carry out anti-mirror image filtering again, anti-aliasing filter and anti-mirror image filtering person are merged in the equal-ripple filter of described restricted type and finish, thereby can reduce the complexity of system design, reduce the memory space of amount of calculation and system.The equal-ripple filter of the restricted type after anti-aliasing filter and anti-mirror image filtering are multiplexing as shown in Figure 3, wherein W represents the filter cut-off angular frequency, the filter cut-off angular frequency W after multiplexing _nEqual decimation filter (frequency overlapped-resistable filter) cut-off angular frequency W _DecimAnd interpolation filter (anti-mirror filter) cut-off angular frequency W _InterpMinimum value.

With reference to Fig. 4, be the structural representation of the filtering implementation method in a kind of many rate processing of the present invention.

Further, at TDMA (Time Division Multiple Address, time division multiple access) in the system, filtering that can multiplexing high-efficiency, the transfer process of transmission channel is the inverse process of receive path, and the difference factor that becomes that extracts factor Q i and difference factor Pi correspondence is got final product with the extraction factor.

Multiplexing structure as shown in Figure 6, for receive path, conversion factors at different levels reduce successively, and for transmission channel, conversion factors at different levels increase successively, by checking, can guarantee to follow the performance of receive path unanimity, verify the result as shown in Figure 7

Technical solution of the present invention is carried out the multinomial decomposition of filtering according to interpolation factor earlier, further decompose according to extracting the factor again, thereby filtering is placed on the low node of sampling rate, reduced the amount of calculation of system on the one hand, reduced requirement, reduced the influence that the finite word length effect of filter brings system sampling clock; Under low rate, carry out anti-aliasing/anti-mirror image filtering on the other hand, reduce hard-wired complexity, improve the sensitivity of system.

Further, anti-aliasing/anti-mirror filter prototype adopts the equal-ripple filter of restricted type to replace Kaiser window function of the prior art, only need fewer filter order, thereby can realize preferably with interior performance and higher attenuation outside a channel, and the equal-ripple filter characteristic according to restricted type merges design with frequency overlapped-resistable filter and anti-mirror filter, reduce the complexity of system design, reduced the memory space of amount of calculation and system.

With reference to Fig. 5, show the structural representation of the filtering implement device preferred embodiment in a kind of many rate processing of the present invention.Described filtering implement device comprises: first resolving cell, second resolving cell, processing unit and anti-aliasing/anti-mirror filter.

Described first resolving cell is used for according to the interpolation factor P of conversion factor P/Q branch road being carried out the multinomial decomposition of filtering, obtains up-sampling factor Pi.

Described second resolving cell is used for according to the extraction factor Q of conversion factor P/Q branch road being carried out the multinomial decomposition of filtering, obtains down-sampling factor Q i.

Described processing unit is used for described up-sampling factor Pi and described down-sampling factor Q i are made up, and determines the progression N of rate transition.

Described anti-aliasing/anti-mirror filter, be used to carry out anti-aliasing/anti-mirror image filtering.

Wherein, described anti-aliasing/anti-mirror filter is the equal-ripple filter of restricted type.

The structure expression of the equal-ripple filter of described restricted type is:

$H\left(Z\right)={\mathrm{\Σ}}_{n=0}^{N-1}h\left(n\right)*Z^{-n};$

Wherein, h (n) is the discrete impulse response of filter, and H (Z) is a system responses, and N is a filter order.

The equal-ripple filter of described restricted type also is used to finish the multiplexing of anti-aliasing filter and anti-mirror image filtering.

Described device embodiment is corresponding with described method embodiment, and therefore, the course of work of the work of described device and each part and operation principle are described in detail in method embodiment shown in Figure 2, gets final product with reference to the description of relevant portion.

One of ordinary skill in the art will appreciate that, realize that all or part of step in the foregoing description method is to instruct relevant hardware to finish by program, described program can be stored in the computer read/write memory medium, this program is when carrying out, comprise step as above-mentioned method embodiment, described storage medium, as: magnetic disc, CD, read-only storage memory body (Read-Only Memory, ROM) or at random store memory body (Random Access Memory, RAM) etc.In each method embodiment of the present invention; the sequence number of described each step can not be used to limit the sequencing of each step; for those of ordinary skills, under the prerequisite of not paying creative work, the priority of each step is changed also within protection scope of the present invention.

The above only is preferred embodiment of the present invention, and is in order to restriction the present invention, within the spirit and principles in the present invention not all, any modification of being done, is equal to replacement, improvement etc., all should be included within protection scope of the present invention.

Claims (11)

1. the filtering implementation method in the rate processing more than a kind is characterized in that, comprising:

According to the interpolation factor P among the conversion factor P/Q branch road is carried out the multinomial decomposition of filtering, obtain up-sampling factor Pi;

According to the extraction factor Q among the conversion factor P/Q branch road is carried out the multinomial decomposition of filtering, obtain down-sampling factor Q i;

Described up-sampling factor Pi and described down-sampling factor Q i are made up, determine to carry out anti-aliasing/anti-mirror image filtering behind the progression N of rate transition.

2. the filtering implementation method in many rate processing according to claim 1 is characterized in that, the difference of described up-sampling factor Pi and described down-sampling factor Q i is less than a predetermined threshold value.

3. the filtering implementation method in many rate processing according to claim 1 is characterized in that described N is less than 4.

4. according to the desirable filtering implementation method that requires in 1 to 3 each described many rate processing, it is characterized in that, describedly carry out anti-aliasing/anti-mirror image filtering and be specially:

Adopt the equal-ripple filter of restricted type to carry out anti-aliasing/anti-mirror image filtering.

5. the filtering implementation method in many rate processing according to claim 4 is characterized in that, the structure expression of the equal-ripple filter of described restricted type is:

Wherein, h (n) is the discrete impulse response of filter, and H (Z) is a system responses, and N is a filter order;

Characteristic according to the equal-ripple filter of described restricted type is finished the multiplexing of anti-aliasing filter and anti-mirror image filtering.

6. the filtering implementation method in many rate processing according to claim 5 is characterized in that, according to the interpolation factor P among the conversion factor P/Q the multinomial decomposition that branch road carries out filtering is carried out according to following formula:

$H\left(Z\right)=\underset{p=0}{\overset{P-1}{\mathrm{\Σ}}}{H}_p\left(Z^P\right)*Z^{-{(P-1-p)}_{;}}$

Described H _p(Z) be the system responses of p input branch road, H (Z) is the system responses of whole prototype filter, its total P input branch road;

Wherein, $H_{P-1-k}\left(Z\right)=\underset{r=0}{\overset{R-1}{\mathrm{\Σ}}}h(r*P+k){\left(Z^P\right)}^{-r};$

Described h (r*P+k) is p-1-k the discrete impulse response on the branch road, and R is the number of the impulse sampling point on each branch road.

7. the filtering implementation method in many rate processing according to claim 5 is characterized in that, according to the extraction factor Q among the conversion factor P/Q the multinomial decomposition that branch road carries out filtering is carried out according to following formula:

$H\left(Z\right)=\underset{p=0}{\overset{P-1}{\mathrm{\Σ}}}{H}_p\left(Z^P\right)*Z^{-{(P-1-p)}_{;}}$

Described H _p(Z) be the system responses of p output branch road, H (Z) is the system responses of whole prototype filter, its total P output branch road;

Wherein, $H_{P-1-k}\left(Z\right)=\underset{r=0}{\overset{R-1}{\mathrm{\Σ}}}h(r*P+k){\left(Z^P\right)}^{-r};$

Described h (r*P+k) is p-1-k the discrete impulse response on the branch road, and R is the number of the impulse sampling point on each branch road.

8. the filtering implement device in the rate processing more than a kind is characterized in that, comprising:

First resolving cell is used for according to the interpolation factor P of conversion factor P/Q branch road being carried out the multinomial decomposition of filtering, obtains up-sampling factor Pi;

Second resolving cell is used for according to the extraction factor Q of conversion factor P/Q branch road being carried out the multinomial decomposition of filtering, obtains down-sampling factor Q i;

Processing unit is used for described up-sampling factor Pi and described down-sampling factor Q i are made up, and determines the progression N of rate transition;

Anti-aliasing/anti-mirror filter, be used to carry out anti-aliasing/anti-mirror image filtering.

9. the filtering implement device in many rate processing according to claim 8 is characterized in that, the difference of described up-sampling factor Pi and described down-sampling factor Q i is less than a predetermined threshold value.

10. according to Claim 8 or the filtering implement device in 9 described many rate processing, it is characterized in that, described anti-aliasing/anti-mirror filter is the equal-ripple filter of restricted type.

11. the filtering implement device in many rate processing according to claim 9 is characterized in that, the structure expression of the equal-ripple filter of described restricted type is:

Wherein, h (n) is the discrete impulse response of filter, and H (Z) is a system responses, and N is a filter order;

The equal-ripple filter of described restricted type also is used to finish the multiplexing of anti-aliasing filter and anti-mirror image filtering.

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