CN1163023A - Filter - Google Patents

Abstract

In adaptive digital filtering, first steps of adapting a filter coefficient dependent on a received data sample, and second steps of filtering by applying an adapted filter coefficient to a received data sample, are alternated so that adapted filter coefficients and modulated data samples are alternatively determined. In consequence, each adapted filter coefficient can be provided for immediate use in filtering.

Description

Filter

The present invention relates to adaptive digital filter, particularly be used in the radio receiver.

Known EC Ifeachor that traditional adaptive digital filter is for example published from Addison-Wesley Publishers company in 1993 and the article " Digital Signal Processing " of DW Jervis.The shortcoming of these filters be in being used in the data sample that modulation receives before all filter factors all be updated and store.This process need related to before filtering reads all these coefficients with these coefficient write memories with from memory.This makes sef-adapting filter relatively slow, perhaps requires other circuit to come update coefficients individually.

The present invention limits in claims, should consult these claims now.

The invention provides a kind of method of adaptive digital filtering, comprise a plurality of first steps, its each step is according to the filter factor of each self adaptation of data sample that receives; With a plurality of second steps, its each step is added to the filter factor after the self adaptation data sample of reception separately, and wherein said first and second steps are timed, and make that filter factor and the modulated data sample after the self adaptation alternately determined.Therefore, the filter factor after each self adaptation can be provided at filtering neutrality and promptly uses and need not to remain in the memory.

According to the error that a previous filtering operation obtains, each coefficient by self adaptation to use in the filtering operation next time.Each filtering operation is the data sample that receives in the back in succession.

The present invention also provides a kind of adaptive digital filter, comprise filter and self-reacting device, this self-reacting device is operated and is used for the adaptive-filtering coefficient and a coefficient after the self adaptation is provided, the filter operation is used for the adaptive-filtering coefficient is added to a data sample that receives, the operation of this filter and self-reacting device is timed, and makes that adaptive-filtering coefficient and modulated data sample are alternately provided.By this way, the clock cycle after determining of the filter factor after the self adaptation can be read into this filter.Filter factor after the self adaptation can be read and write memory by filter at preset time, so that using after a while.

The present invention also provides a receiver, and it comprises an aforesaid New Adaptive digital filter.This receiver can be used for radio or communication, especially for time division multiplexing (TDM) and/or time division multiple access (TDMA) communication.This receiver can be the base station that receives tdma communication from subscriber unit, and these subscriber units can be in the fixed location.

The invention still further relates to the method for corresponding radio reception.

The present invention preferably provides the advantage of the data throughput that has increased by simple adaptive digital filter.

Now by way of example and contrast accompanying drawing narration the preferred embodiments of the present invention, wherein:

Fig. 1 is the simple block diagram of explanation sef-adapting filter; With

Fig. 2 is the block diagram according to sef-adapting filter of the present invention.

As shown in Figure 1, sef-adapting filter 1 comprises a digital filter 2 that is connected with self-reacting device 4.Data sample D is received and is added to digital filter 2, and a filtered output signal FIR is provided _ResultDepend on as exporting FIR at filter that receive and expectation _ResultBetween the error E of difference, the previous filter factor Cn that is applied by filter 2 is corrected promptly and upgrades so that adaptive filter factor Cn ' is provided.These adaptation coefficients Cn ' is applied in any systematic error that receives with filtering in data sample D.Filter 2 is many taps (for example 8 taps) filters, and its work is to provide output FIR according to following formula _Result: ${\mathrm{FIR}}_{\mathrm{result}}=\underset{n=0}{\overset{n=7}{\mathrm{\Σ}}}{\mathrm{Cn}}^{\′}{D}_{N+n+2}$ (formula 1)

Cn ' is filter factor and the D after upgrading in the formula _N+n+2Be data sample, N is illustrated in the self adaptation of combination and first data sample in the filtering.

Filter response plural number error signal E works, and error signal E derives as follows:

E=K (FIR _ResultThe result of-expectation) (formula 2)

K is provided with the positive constant of controlling adaptive speed in the formula.

Error E is used for upgrading according to the LMS algorithm filter factor of self-reacting device 4, and concrete formula is as follows:

Cn′＝Cn-E.D ^* _N+n 0≤n≤7 (3)

D in the formula ^* _N+nBe D _N+nComplex conjugate.

Therefore the self-reacting device 4 of sef-adapting filter 1 plays a part to change filter factor so that filtering output FIR expectation and that receive _ResultConsistent.

Each coefficient of staggered permission of filtering (formula 1) and self adaptation (formula 2) operation carries out self adaptation according to the error that derives from previous filtering operation before in being used to current filtering operation.

For self adaptation and filtering operation, require initialization, substitution formula 3, the self adaptation operation becomes:

Cn '=0 couple 0≤n≤7

The device of representing sef-adapting filter 1 among Fig. 2 in more detail.A complex multiplier 6 is arranged, and it is from data storage 8 receiving data sample value D and optionally receive from the selector 14 with output signal of representing with X from the error amount of error register 10 or from the filter factor Cn of controller buffer 15.Multiplier 6 is received arithmetic and logical unit ALU, and it provides signal M to this ALU.Arithmetic and logical unit ALU provides an output signal A and execution that filtering data sample value F and the needed calculating of coefficient Cn ' are provided, and narrates as following.

Modulated data sample F feeds back to register 16, and this register 16 is received selector 18.The other input port of selector 18 is received register 20, is used to keep filter factor C.The output port of selector 18 is received arithmetic and logical unit ALU, and the output of arithmetic and logical unit ALU is received coefficient memory 12 and selector 14 through controller buffer 15, and this ALU transmits updated filter coefficients C ' to these two.Selector 18 provides signal Y to arithmetic and logical unit ALU.

The operating sequence of being undertaken by sef-adapting filter 1 shown in the table 1, explain each operation of data storage 8, coefficient memory 12, multiplier 6, ALU and selector 14 and 18 in each time step of whole self adaptation and filtering operation, and the data value in the circuit.

As shown in table 1, in time step 1, the first data sample D _N+0Offer multiplier 6 with error value E.Because multiplier three class pipeline (pipeline) after 3 time steps, occurs in time step 4, multiplier 6 work provide E.D ^* _N+0Output signal M.At time step 3, C ₀Read in C register 20 from coefficient memory 12, it is available becoming ALU by selector 18 in time step 4.Arithmetic and logical unit ALU action provides C in time step 4 ₀-E.D ^* _N+0Output A.This is fed to C ₀' arrive multiplier 6 to coefficient memory 12 and by selector 14.Finished the self adaptation of first filter factor like this.

Still at time step 4, D _N+2Offer multiplier 6 from data storage 8.In time step 7, multiplier 6 work provide C after 3 time steps ₀', D _N+2Output M.ALU does not do to change and will export M and be sent to F register 16, finishes the modulation of first data sample in filtering.

The top sequence of operation is wherein for n=0 situation, C _n' and C _n' .D _N+n+2From E, D _N, Cn and D _N+n+2Calculate, these sequences of operation repeat for n=1 to 7 (comprising 7), are respectively in time step 3,5,7,9,11,13 and 15 beginnings.But for these sequences, the work of ALU is changed to and produces F+Cn ' .D during filtering (data-modulated) stage (in time step 9,11,13,15,17,19 and 21) _N+n+2A as a result, make like this this result comprise all previous modulated data and, desired suc as formula 1.

These repeating sequences are interlocked jointly, make this multiplier and ALU alternately operate the coefficient Cn ' and the modulated data sample value of renewal, by this way to guarantee the providing coefficient of renewal to need not to be written to for using immediately and read from memory subsequently.

Table 1

Claims (13)

1. an adaptive digital filtering method comprises a plurality of first steps, and its each data sample according to reception comes the adaptive-filtering coefficient; With a plurality of second steps, its each carry out filtering for the data sample that receives by applying an adaptive filter factor, wherein said each first and second step are timed, so that alternately determine described adaptive-filtering coefficient and modulated data sample.

2. according to the method for the adaptive digital filtering of claim 1, wherein each described second step is that the data sample that receives in the back is continuously carried out.

3. according to the method for the adaptive digital filtering of claim 1 or 2, wherein provide each adaptive-filtering coefficient to come in filtering, to use immediately and do not remain in the memory.

4. according to the method for the adaptive digital filtering of any claim of front, wherein said these coefficients according to the error that from previous filtering operation, obtains by self adaptation to be used for next filtering operation.

5. according to the method for the adaptive digital filtering of any claim of front, wherein following formula is satisfied in filtering: ${\mathrm{FIR}}_{\mathrm{result}}=\underset{n=0}{\overset{n=7}{\mathrm{\Σ}}}C{n}^{\′}{D}_{N+n+2}$

Cn ' is a updated filter coefficients in the formula, and D _N+n+2Be data sample, N is illustrated in the self adaptation of combination and first data sample in the filtering.

6. according to the method for the adaptive digital filtering of the claim 5 that is subordinated to claim 4, wherein error E is derived as follows:

E=K (FIR _ResultThe result of-expectation)

K is provided with a positive constant controlling adaptive speed in the formula, and error E is used for upgrading filter factor according to following formula:

Cn′＝Cn-E.D ^* _N+n 0≤n≤7

D in the formula ^* _N+nBe D _N+nComplex conjugate.

7. adaptive digital filter, comprise filter and self-reacting device, this self-reacting device operation provides an adaptation coefficient with the adaptive filtering coefficient, this filter operation provides an adaptive-filtering coefficient to the data sample that receives, the operation of this filter and self-reacting device is timed, and making alternately provides described adaptive-filtering coefficient and modulated data sample.

8. according to the adaptive digital filter of claim 7, comprise providing each adaptive-filtering coefficient to be used in device in the filtering immediately.

9. adaptive digital filter according to Claim 8, wherein the adaptive-filtering coefficient is determining that a back clock cycle is read into this filter.

10. according to the adaptive digital filter of any claim of claim 7 to 9, wherein go into a memory for using subsequently by described filter read and write at a preset time adaptive-filtering coefficient.

11. according to the adaptive digital filter of any claim of claim 7 to 10, wherein this self-reacting device operation is so that come described these coefficients of self adaptation to be used for next filtering operation according to the error that obtains from last filtering operation.

12. one kind is used for radio or receiver in communication, comprises the adaptive digital filter according to any claim of claim 7 to 11.

13. the method for radio or communications reception comprises the method according to the adaptive digital filtering of any claim of 1 to 4.