CN201928245U - Digital filtering device used in audio frequency sigma-delta analog-digital converter and analog-digital converter - Google Patents
Digital filtering device used in audio frequency sigma-delta analog-digital converter and analog-digital converter Download PDFInfo
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- CN201928245U CN201928245U CN2010206720677U CN201020672067U CN201928245U CN 201928245 U CN201928245 U CN 201928245U CN 2010206720677 U CN2010206720677 U CN 2010206720677U CN 201020672067 U CN201020672067 U CN 201020672067U CN 201928245 U CN201928245 U CN 201928245U
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Abstract
The utility model relates to a digital filtering device used in an audio frequency sigma-delta analog-digital converter, comprising a plurality of storage units, a plurality of multiplexers and a control unit, wherein the plurality of storage units are respectively arranged at different positions, filtering coefficients of the digital filtering device are respectively stored in the plurality of storage units which are respectively connected with the plurality of multiplexers, the plurality of multiplexers are used for alternatively outputting the filtering coefficients to a plurality of logic operation units under the control of the control unit, and the plurality of logic operation units are used for respectively operating the input filtering coefficients and data output by the sigma-delta analog-digital converter, and then respectively outputting the filtering coefficients and the data to a plurality of accumulators. The utility model also relates to the audio frequency sigma-delta analog-digital converter. The digital filtering device used in the audio frequency sigma-delta analog-digital converter has the following beneficial effects of reducing silicon chip area occupied by the digital filtering device, and saving the cost.
Description
Technical field
The utility model relates to Digital Signal Processing, more particularly, relates to a kind of digital filter apparatus that is used for audio frequency sigma-delta analog to digital converter.
Background technology
Typical sigma-delta ADC(is the sigma-delta analog to digital converter) comprise a sigma-delta modulator and an extraction digital filter.Fig. 1 is the structural representation of modulator.Extracting digital filter is the key component of sigma-delta ADC, its objective is from this data flow to extract Useful Information, and data rate is reduced to available level.In sigma-delta ADC, behind modulator (modulator), the gross power of the quantizing noise of data does not reduce, and just distributing has changed, and concentrates on high band by evenly distributing in entire spectrum originally, becoming.Because sigma-delta ADC has adopted the over-sample technology, sample rate is far above Nyquist (Nyquiste) frequency, therefore need carry out down-sampled (down sample) so that reduce data rate, in this process, high fdrequency component may cause aliasing (alising), signal to noise ratio is descended, therefore need to use the filtering out-of-band noise of decimation filter, reduce the generation of aliasing, make the signal after down-sampled that higher signal to noise ratio be arranged, remove unnecessary data simultaneously, reduce data rate, convenient back level is handled.
Reduce because bandwidth is output digital filter, output data rate can be lower than raw sampling rate, but still satisfies the Nyquist law.This can abandon all the other and sample and realize that this process is exactly so-called by the M factor " extraction " by keeping some sampling.The M factor is the extraction ratio, can be any integer value.When selecting to extract the factor, should make output data rate be higher than the signal bandwidth of twice.Like this, if with the frequency of fs input signal is sampled, filtered output data rate can be reduced to fs/M, and can not lose any information.
In high-performance audio frequency sigma-delta ADC, require filter in whole voiceband, to have very smooth characteristic, so that realize the high fidelity voice reproducing, and passband ripple, cut-off frequecy of passband and the stopband cut-off frequency etc. of cic filter commonly used can not be controlled arbitrarily, therefore can make troubles to design, need to use the FIR filter, carry out extraction operation after the filtering.Fig. 2 is that traditional use FIR filter adds drawing-out structure realization decimation filter block diagram, every ROM has preserved all filter coefficients among the figure, the operating frequency of accumulator is identical with the bit rate of modulator output, whenever 32 input bits of being separated by during work start an accumulator and add up, and the switching interval of data selector also is the time of 32 input bits.
Because every ROM has preserved whole filter coefficients, and the filter effect in order to obtain, the filter coefficient bit wide is all bigger, so the capacity of ROM is often very big.With the filter of audio frequency sigma-delta ADC for, typical exponent number is 1024, the filter coefficient bit wide is 20bit, the capacity of so every blocking filter coefficients R OM is 1024*20bit, i.e. 20k bit, and the total capacity of 32 ROM is the 640k bit so, taken a large amount of silicon area, production cost is very high.
In order to satisfy high performance requirements, the exponent number of FIR filter is very large, for example the passband ripple of the filter of audio frequency sigma-delta ADC requires less than ± 0.001dB, satisfy such needs that require and use the FIR filter on 1024 rank, may need to consume a large amount of resources, take very big silicon area, cause product cost too high, influence competitiveness.
The utility model content
The technical problems to be solved in the utility model is, at the above-mentioned bigger defective of silicon area that takies of prior art, provides a kind of less a kind of digital filter apparatus that is used for audio frequency sigma-delta analog to digital converter of silicon area that takies.
The technical scheme that its technical problem that solves the utility model adopts is: construct a kind of digital filter apparatus that is used for audio frequency sigma-delta analog to digital converter, comprising: a plurality of memory cell, a plurality of Port Multiplier, control unit, a plurality of arithmetic logic unit and a plurality of accumulator; Wherein, described a plurality of memory cell are arranged on diverse location respectively, and described a plurality of memory cell store the filter factor of described digital filter respectively, and described a plurality of memory cell are connected with described a plurality of Port Multipliers respectively; Described a plurality of Port Multiplier is selected the described filter factor of an output respectively to described a plurality of arithmetic logic unit under the control of described control unit, output to described a plurality of accumulator respectively behind the data operation that described a plurality of arithmetic logic unit are exported the filter factor and the described sigma-delta analog to digital converter of input respectively.
At the digital filter apparatus that is used for audio frequency sigma-delta analog to digital converter described in the utility model, the output of described a plurality of memory cell is connected respectively to described each Port Multiplier input.
At the digital filter apparatus that is used for audio frequency sigma-delta analog to digital converter described in the utility model, described number of accumulators is the down-sampled rate of described digital filter exponent number divided by described digital filter.
At the digital filter apparatus that is used for audio frequency sigma-delta analog to digital converter described in the utility model, described Port Multiplier quantity is the down-sampled rate of digital filter exponent number divided by digital filter, described memory cell is the ROM piece that is distributed in diverse location, and the degree of depth of described each ROM piece equals down-sampled rate.
At the digital filter apparatus that is used for audio frequency sigma-delta analog to digital converter described in the utility model, described Port Multiplier and described arithmetic logic unit are corresponding one by one, and described arithmetic logic unit is and door.
At the digital filter apparatus that is used for audio frequency sigma-delta analog to digital converter described in the utility model, described control unit comprises the address production electric circuit of the memory address that is used to write down the filter factor that produces described bit correspondence by the frequency divider of the bit number of described modulator input, according to described bit number and controls the Port Multiplier control unit that described a plurality of Port Multiplier is selected the filter factor of output according to described address.
At the digital filter apparatus that is used for audio frequency sigma-delta analog to digital converter described in the utility model, also comprise being connected between described digital filter output and the described a plurality of accumulator output, connecting the selector switch between described digital filter output and the described a plurality of accumulator output successively.
At the digital filter apparatus that is used for audio frequency sigma-delta analog to digital converter described in the utility model, described selector switch begins to connect the output of described a plurality of accumulators and the output of described digital filter behind the described modulator output bit number identical with described digital filter exponent number; And behind the described modulator output bit number identical, jump to the output of next accumulator with the described ROM degree of depth.
The utility model also relates to a kind of audio frequency sigma-delta analog to digital converter, described audio frequency sigma-delta analog to digital converter comprises digital filter apparatus, described digital filter apparatus is above-mentioned digital filter apparatus, and it comprises a plurality of memory cell, a plurality of Port Multiplier, a plurality of control unit, arithmetic logic unit and a plurality of accumulator; Wherein, described a plurality of memory cell are arranged on diverse location respectively, and described a plurality of memory cell store the filter factor of described digital filter respectively, and described a plurality of memory cell are connected with described a plurality of Port Multipliers respectively; Described a plurality of Port Multiplier is selected the described filter factor of an output respectively to described a plurality of arithmetic logic unit under the control of described control unit, output to described a plurality of accumulator respectively behind the data operation that described a plurality of arithmetic logic unit are exported the filter factor and the described sigma-delta analog to digital converter of input respectively.
Implement the digital filter apparatus that is used for audio frequency sigma-delta analog to digital converter of the present utility model, has following beneficial effect: owing in digital filter apparatus, use memory cell separately to store filter factor, and use control unit to make appropriate defeated filter factor appear on the arithmetic logic unit, so, do not need each memory cell all to store all filter factors, but as long as all memory cell can be stored whole filter factors, this not only makes the shared silicon area of memory cell dwindle, also make the area of each memory cell dwindle, so, under the situation that guarantees the digital filter apparatus operate as normal, significantly reduced its shared silicon area, provided cost savings.
Description of drawings
Fig. 1 is the principle schematic of modulator in the sigma-delta analog to digital converter;
Fig. 2 is a digital filter theory diagram in the sigma-delta analog to digital converter;
Fig. 3 is that the utility model is used for the digital filter apparatus of audio frequency sigma-delta analog to digital converter and the theory diagram of analog to digital converter embodiment digital filter.
Embodiment
Below in conjunction with accompanying drawing the utility model embodiment is described further.
As shown in Figure 3, be used for the digital filter apparatus embodiment of audio frequency sigma-delta analog to digital converter at the utility model, this digital filter apparatus comprises a plurality of memory cell, a plurality of Port Multiplier, control unit, a plurality of arithmetic logic unit and a plurality of accumulator; Wherein, a plurality of memory cell are arranged on diverse location respectively, and usually, digital filter is provided with in the integrated circuit, and these positions are the diverse locations in the digital filter apparatus, promptly finish the diverse location of the integrated circuit of digital filter apparatus function; A plurality of memory cell store the filter factor of this digital filter respectively, that is to say, the filter factor in all memory cell is added up and just constituted a complete filter factor; A plurality of memory cell are connected with a plurality of Port Multipliers respectively, and the output of a plurality of memory cell is connected respectively to each Port Multiplier input, and each Port Multiplier all is connected with the output of all said memory cells; A plurality of Port Multipliers are selected its filter factor that receives of output respectively to a plurality of arithmetic logic unit under the control of control unit, a Port Multiplier outputs to an arithmetic logic unit; Output to a plurality of accumulators respectively after data (dateout of the modulator of the just above-mentioned analog to digital converter) computing that a plurality of arithmetic logic unit are exported the filter factor and the described sigma-delta analog to digital converter of input respectively, equally, a logic conversion unit also is only to output to an accumulator.In a word, above-mentioned Port Multiplier and arithmetic logic unit are corresponding one by one; And arithmetic logic unit for according to a plurality of inputs are arranged with door.
In the present embodiment, number of accumulators is the down-sampled rate of digital filter exponent number divided by digital filter; In addition, said memory cells is for being distributed in the ROM piece of diverse location in the digital filter apparatus (integrated circuit), and the degree of depth of each ROM piece is 32, promptly equals above-mentioned down-sampled rate.
In the present embodiment, control unit comprises the address production electric circuit of the memory address that is used to write down the filter factor that produces described bit correspondence by the frequency divider of the bit number of described modulator input, according to described bit number and controls the Port Multiplier control unit that described a plurality of Port Multiplier is selected the filter factor of output according to described address.
With 1024 taps, down-sampled rate is 32 to be example, supposes that the speed of modulator output bit is 1.536MHz, and the filter output speed is 48KHz, coefficients R OM can be decided to be 32, the number of accumulator also is 32, and this moment, the degree of depth of every ROM was 32, may further comprise the steps during work:
1) frequency divider is since 1 counting, and frequency is identical with the output bit rate of modulator, and the count cycle is 32
2) output of frequency divider is as the address of coefficients R OM, therefore exported 1 o'clock at frequency divider, 32 ROM outputs be respectively coefficient 1,33,65 ..., 961,993
3) Port Multiplier is selected required coefficient, and with the filter input bit with
4) with result is input to accumulator and adds up
5) behind 1024 bits of modulator input, from 0 first filtering of the output result of output branch
6) behind later 32 bits of every input, successively from output branch 1, output branch 2 ... output filtering result
In the present embodiment, the last output of digital filter apparatus realizes by a selector switch, it is connected between digital filter output and a plurality of accumulator output, and successively between number of ports character filter output and a plurality of accumulator output, make the output of connected accumulator appear on the output of above-mentioned digital filter, as the output of digital filter; This selector switch begins to connect the output of a plurality of accumulators and the output of digital filter behind the signal of the said modulator output bit number identical with the digital filter exponent number; And behind the signal of the modulator output bit number identical, jump to the output of next accumulator with the described ROM degree of depth.
By top description, learn that described digital filter apparatus comprises Port Multiplier, accumulator, coefficients R OM, frequency divider and other control logics (being control unit).When its filtering, from ROM, read filter coefficient, utilize Port Multiplier to choose corresponding filter coefficient, filter coefficient and input bit and (logical operation) add up to the result with operation, read accumulation result and export as filter.
In fact, be that 32 extraction digital filter is an example with 1024 rank, down-sampled rate in the present embodiment, the speed of supposing modulator output bit is 3.072MHz, the filter output speed is 48KHz, coefficients R OM gets 32 and (can choose flexibly in principle, as long as assurance can be read 32 filter coefficients, adjacent filter coefficient numbering is separated by 32) at every turn, the number of accumulator also is 32 (number of accumulator must equal filter order divided by down-sampled rate), and this moment, the degree of depth of every ROM was 32.So the capacity of every ROM is the 32*20 bit, total capacity is the 32*20*32 bit, just the bit number summation of all filter coefficients.
Preserve the many parts of problems (taking bigger silicon area) that complete coefficient causes for avoiding existing design, present embodiment is split as a plurality of sublists to a complete table of filter coefficients, and be kept among the different ROM, adopt Port Multiplier selecting filter coefficient during use, so the resource that whole digital filter apparatus takies reduces greatly.
Present embodiment also relates to a kind of audio frequency sigma-delta analog to digital converter, and this audio frequency sigma-delta analog to digital converter comprises digital filter apparatus, and described digital filter apparatus is the digital filter apparatus defined in the present embodiment.Usually, one or more described audio frequency sigma-delta analog to digital converters are with an independently form appearance of integrated circuit.
The above embodiment has only expressed several execution mode of the present utility model, and it describes comparatively concrete and detailed, but can not therefore be interpreted as the restriction to the utility model claim.Should be pointed out that for the person of ordinary skill of the art under the prerequisite that does not break away from the utility model design, can also make some distortion and improvement, these all belong to protection range of the present utility model.Therefore, the protection range of the utility model patent should be as the criterion with claims.
Claims (9)
1. a digital filter apparatus that is used for audio frequency sigma-delta analog to digital converter is characterized in that, comprising: a plurality of memory cell, a plurality of Port Multiplier, control unit, a plurality of arithmetic logic unit and a plurality of accumulator; Wherein, described a plurality of memory cell are arranged on diverse location respectively, and described a plurality of memory cell store the filter factor of described digital filter respectively, and described a plurality of memory cell are connected with described a plurality of Port Multipliers respectively; Described a plurality of Port Multiplier is selected the described filter factor of an output respectively to described a plurality of arithmetic logic unit under the control of described control unit, output to described a plurality of accumulator respectively behind the data operation that described a plurality of arithmetic logic unit are exported the filter factor and the described sigma-delta analog to digital converter of input respectively.
2. the digital filter apparatus that is used for audio frequency sigma-delta analog to digital converter according to claim 1 is characterized in that, the output of described a plurality of memory cell is connected respectively to described each Port Multiplier input.
3. the digital filter apparatus that is used for audio frequency sigma-delta analog to digital converter according to claim 2 is characterized in that, described number of accumulators is the down-sampled rate of described digital filter exponent number divided by described digital filter.
4. the digital filter apparatus that is used for audio frequency sigma-delta analog to digital converter according to claim 3, it is characterized in that, described Port Multiplier quantity is the down-sampled rate of digital filter exponent number divided by digital filter, described memory cell is the ROM piece that is distributed in diverse location, and the degree of depth of described each ROM piece equals down-sampled rate.
5. the digital filter apparatus that is used for audio frequency sigma-delta analog to digital converter according to claim 4 is characterized in that, described Port Multiplier and described arithmetic logic unit are corresponding one by one, and described arithmetic logic unit is and door.
6. the digital filter apparatus that is used for audio frequency sigma-delta analog to digital converter according to claim 5, it is characterized in that described control unit comprises the address production electric circuit of the memory address that is used to write down the filter factor that produces described bit correspondence by the frequency divider of the bit number of described modulator input, according to described bit number and controls the Port Multiplier control unit that described a plurality of Port Multiplier is selected the filter factor of output according to described address.
7. according to any described digital filter apparatus that is used for audio frequency sigma-delta analog to digital converter of claim 1-6, it is characterized in that, also comprise being connected between described digital filter output and the described a plurality of accumulator output, connecting the selector switch between described digital filter output and the described a plurality of accumulator output successively.
8. the digital filter apparatus that is used for audio frequency sigma-delta analog to digital converter according to claim 7, it is characterized in that described selector switch begins to connect the output of described a plurality of accumulators and the output of described digital filter behind the described modulator output bit number identical with described digital filter exponent number; And behind the described modulator output bit number identical, jump to the output of next accumulator with the described ROM degree of depth.
9. an audio frequency sigma-delta analog to digital converter comprises digital filter apparatus, it is characterized in that, described digital filter apparatus is a digital filter apparatus as claimed in claim 8.
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| CN2010206720677U CN201928245U (en) | 2010-12-21 | 2010-12-21 | Digital filtering device used in audio frequency sigma-delta analog-digital converter and analog-digital converter |
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Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN105099395A (en) * | 2014-05-19 | 2015-11-25 | 深圳市欧克蓝科技有限公司 | Configurable digital filter device |
| CN110620565A (en) * | 2019-08-09 | 2019-12-27 | 西人马帝言(北京)科技有限公司 | Digital extraction filter |
| CN113098515A (en) * | 2020-01-08 | 2021-07-09 | 炬芯科技股份有限公司 | Analog-to-digital conversion system and audio equipment |
-
2010
- 2010-12-21 CN CN2010206720677U patent/CN201928245U/en not_active Expired - Fee Related
Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN105099395A (en) * | 2014-05-19 | 2015-11-25 | 深圳市欧克蓝科技有限公司 | Configurable digital filter device |
| CN110620565A (en) * | 2019-08-09 | 2019-12-27 | 西人马帝言(北京)科技有限公司 | Digital extraction filter |
| CN113098515A (en) * | 2020-01-08 | 2021-07-09 | 炬芯科技股份有限公司 | Analog-to-digital conversion system and audio equipment |
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