CN102055480B - Sampling frequency conversion device - Google Patents
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Abstract
The invention provides a sampling frequency conversion device capable of converting a simulated audio signal into a digital audio signal with a target frequency. The sampling frequency conversion device comprises a trigonometric integral modulator, a first frequency-reducing filtration module, a frequency-increasing/reducing module and a third frequency-reducing filtration module, wherein the first frequency-reducing filtration module filters and reduces the frequency of the digital audio signal with a first frequency so as to generate a digital audio signal with a second frequency; the frequency-increasing/reducing module increases and reduces the frequency of the digital audio signal with the second frequency so as to generate a digital audio signal with a third frequency; and the third frequency-reducing filtration module receives the digital audio signal output by the frequency-increasing/reducing module so as to generate a digital audio signal with the target frequency. The ADC (analog to digital converter) of the device provided by the invention requires no extra quartz oscillator or phase locking return circuit to generate the sampling frequency, so the circuit area and the manufacturing cost are both efficiently lowered.
Description
Technical field
The invention relates to a kind of sampling frequency conversion equipment, refer to a kind of sampling frequency conversion equipment that is applied to an audio frequency simulation digital quantizer especially, make this audio frequency simulation digital quantizer not need to utilize quartz (controlled) oscillator or phase-locked loop to produce sampling frequency.
Background technology
Mostly use 48kHz, 44.1kHz on the present multimedia main flow audio format or these three kinds of reference frequencies of 32kHz are taken advantage of or divided by a positive integer N, as the sampling frequency of audio output signal.For instance, the sampling frequency 192kHz of high definition audio (High Definition Audio) specification is 48kHz four times (48kHz*4); The sampling frequency 8kHz of MPEG-4CELP specification is 1/4th (32kHz/4) of 32kHz.In order to support different sampling frequencies, (Analog-to-Digital Converter, ADC) operating frequency of Shi Yonging must be the integral multiple of sampling frequency to the audio frequency simulation digital quantizer.Suppose that above-mentioned sampling frequency is Fs, general common operating frequency comprises (256*Fs), (384*Fs), (512*Fs) and (768*Fs).Yet above-mentioned operating frequency is not present in the system originally.Be the audio frequency playing function in response to different sampling frequencies, in the design of audio A C, must increase crystal oscillator (crystal oscillator) or phase-locked loop (Phase Lock Loop, a PLL) circuit that can produce corresponding operating frequency.
Please refer to Fig. 1, Fig. 1 is the schematic diagram of the audio A C100 framework of prior art.Audio A C100 comprises a trigonometric integral modulator (Sigma-Delta Modulator, SDM) 110, one comb filter (comb filter), 120, one N times frequency demultiplier 130, a frequency reducing filtration module 140 and simulation picture lock loop (Analog Phase Lock Loop, APLL) 150.The operating frequency that audio A C100 produces according to APLL150 is converted to a simulated audio signal digital audio and video signals of one target sampling frequency Fs.SDM110 is used for a simulated audio signal is carried out oversampling (over-sampling), so that this simulated audio signal is converted to a digital audio and video signals.To a sample of signal often regular meeting cause crossover (aliasing) phenomenon; and cause distorted signals; for avoiding this situation; sampling frequency to this sample of signal the time must be greater than the Nyquist rate (Nyquist rate) of this signal; the twice signal frequency of this signal just; (Oversampling Rate OSR) especially must be much larger than the twice signal frequency of this simulated audio signal and SDM110 is in the oversampling rate of simulated audio signal being carried out oversampling.Thus, the quantizing noise (quantization noise) that produces to this simulated audio signal sampling the time can be evenly distributed between the higher frequency range, therefore can effectively reduce the quantizing noise in the signal frequency range.
Frequency reducing filtration module 140 is used for digital audio and video signals that N times of frequency demultiplier 130 exported frequency reducing one positive integer (for instance, frequency reducing 4 multiples) further, to produce the digital audio and video signals of target sampling frequency Fs.In general, frequency reducing filtration module 140 comprises an attenuation compensation filter (Drop compensation Filter, DCF) 141,1 the first half 142,1 the 1 times of frequency demultiplier 143 of band filter (half band filter), one the second half band filter 144 and one the 22 times of frequency demultiplier 145.Because cic filter can cause the decay of passband (passband) medium-high frequency part signal energy, so DCF141 can be used to compensate the decay of this gain.The first half band filters 142 are electrically connected at DCF141, be a low pass filter (low pass filter, LPF), be used for the digital audio and video signals that DCF141 exports is carried out filtering, to avoid signal after through the first twice frequency demultiplier 143, produce the phenomenon of signal crossover (aliasing), influence the quality of audio output signal.The one or two times of frequency demultiplier 143 is electrically connected at the first half band filters 142, is used for 2 times of digital audio and video signals frequency reducings that DCF141 is exported.The second half band filters 144 are electrically connected at the one or two times of frequency demultiplier 143, and the two or two times of frequency demultiplier 145 is electrically connected at the second half band filters 144.The operation principles of the second half band filters 144 and the two or two times of frequency demultiplier 145 and the first half band filters 142 and the one or two times of frequency demultiplier 143 are similar.Therefore, frequency reducing filtration module 140 digital audio and video signals that N times of frequency demultiplier 130 exported 4 times of frequency reducings again.
In order to support above-mentioned sampling frequency (48kHz, 44.1kHz or 32kHz), APLL150 can produce the operating frequency Fs*4N of audio A C100 according to sampling frequency Fs.According to industry common specification now, suppose that the sampling frequency Fs that audio A C100 desire produces is 44.1kHz, with the sampling frequency Fs as audio output signal, wherein N is 32, then the frequency that produces of APLL150 is 5.6448MHz (44.1kHz*4*32).Yet though APLL150 can produce corresponding sampling frequency according to different audio signals, APLL150 shared area in integrated circuit is comparatively big mutually, and therefore required cost is higher relatively.
Summary of the invention
Therefore, a purpose of the present invention is to provide a kind of sampling frequency conversion equipment that is applied to an audio frequency simulation digital quantizer.
The invention provides a kind of sampling frequency conversion equipment, be used for a simulated audio signal is converted to the digital audio and video signals of a target frequency.This sampling frequency conversion equipment comprises a trigonometric integral modulator, one first frequency reducing filtration module, a lifting frequency module and one the 3rd frequency reducing filtration module.This trigonometric integral modulator is used for according to an operating frequency this simulated audio signal being taken a sample, to produce the digital audio and video signals of a first frequency.This first frequency reducing filtration module is electrically connected at this trigonometric integral modulator, is used for receiving the digital audio and video signals of this first frequency, and the digital audio and video signals of this first frequency is carried out filtering and frequency reducing, to produce the digital audio and video signals of a second frequency.This lifting frequency module is electrically connected at this first frequency reducing filtration module, is used for the digital audio and video signals of this second frequency is carried out raising frequency and frequency reducing, to produce the digital audio and video signals of one the 3rd frequency.The 3rd frequency reducing filtration module is electrically connected at this lifting frequency module, is used for receiving the digital audio and video signals of this lifting frequency module output to produce the digital audio and video signals of target frequency.
Wherein, the lifting frequency module more comprises one second frequency reducing filtration module, when the digital audio and video signals of the 3rd frequency is 2 of a predeterminated frequency
nTimes the time, export digital audio and video signals to the three frequency reducing filtration modules of the 3rd frequency; When the digital audio and video signals of the 3rd frequency is not 2 of this predeterminated frequency
nTimes the time, the digital audio and video signals of the 3rd frequency is carried out filtering and frequency reducing, with digital audio and video signals to the three frequency reducing filtration modules that produce one the 4th frequency.Wherein n is an integer.
The invention provides the audio A C of a sampling frequency translation function, the operating frequency that can utilize system's clock pulse to produce is converted to a simulated audio signal digital audio and video signals of one target frequency.Because ADC of the present invention does not need to utilize extra quartz (controlled) oscillator or phase-locked loop to produce sampling frequency, therefore can effectively reduce circuit area and manufacturing cost.
Description of drawings
Fig. 1 is the schematic diagram of sampling frequency conversion equipment of the audio frequency simulation digital quantizer framework of prior art;
Fig. 2 A is the schematic diagram of the sampling frequency conversion equipment of explanation audio frequency simulation digital quantizer of the present invention;
Fig. 2 B is the schematic diagram of another embodiment of the sampling frequency conversion equipment of explanation audio frequency simulation digital quantizer of the present invention;
Fig. 3 is the relation table of explanation operating frequency, target frequency and first to the 5th parameter;
Fig. 4 is the relation table of first to the 5th parameter of the different operating frequency of explanation;
Fig. 5 A is the schematic diagram of the embodiment that changes according to the sampling frequency conversion equipment of Fig. 2 A;
Fig. 5 B is the schematic diagram of the embodiment that changes according to the sampling frequency conversion equipment of Fig. 2 B.
Drawing reference numeral:
100 audio frequency simulation digital quantizers
200,201,500,501 sampling frequency conversion equipments
110,210 trigonometric integral modulators
120 filters
130 N times frequency demultiplier
140 frequency reducing filtration modules
150 analog pll circuits
220 first frequency reducing filtration modules
221 first upconverters
222 first filters
223 first frequency demultipliers
230 lifting frequency modules
231 second upconverters
232 second frequency demultipliers
233 low pass filters
240 second frequency reducing filtration modules
241 second filters
242 the 3rd frequency demultipliers
250 the 3rd frequency reducing filtration modules
141,251 attenuation compensation filters
142,252 the first half band filters
143 the 1 times of frequency demultipliers
144,254 the second half band filters
145 the 22 times of frequency demultipliers
253 the 4th frequency demultipliers
255 the 5th frequency demultipliers
A ~ E first ~ the 5th parameter
The Fs target frequency
The Fs2 second frequency
Fs3 the 3rd frequency
Fs4 the 4th frequency
The Fsc operating frequency
P1 first path
P2 second path
Embodiment
Please refer to Fig. 2 A, Fig. 2 A is the schematic diagram of the sampling frequency conversion equipment 200 of explanation audio A C of the present invention.Sampling frequency conversion equipment 200 comprises a trigonometric integral modulator (Sigma-Delta Modulator, SDM) 210,1 first frequency reducing filtration module 220, a lifting frequency module 230 and one the 3rd frequency reducing filtration module 250.Wherein, more comprise one second frequency reducing filtration module 240 in the lifting frequency module.Sampling frequency conversion equipment 200 utilizes SDM210 that one simulated audio signal is carried out oversampling (Over-sampling), to produce a digital audio and video signals, wherein the first frequency reducing filtration module 220, lifting frequency module 230, the second frequency reducing filtration module 240 and the 3rd frequency reducing filtration module 250 come this digital audio and video signals is carried out raising frequency and frequency reducing according to different parameters respectively, to produce the digital audio and video signals of a target frequency Fs.
SDM210 is used for a simulated audio signal is carried out oversampling, so that this simulated audio signal is converted to a digital audio and video signals.In the present embodiment, SDM210 comes to this simulated audio signal oversampling, to export the digital audio and video signals of a frequency Fsc according to the operating frequency Fsc (for instance, system's clock pulse is 24MHz, and operating frequency Fsc is 6MHz) that system's clock pulse produces.
The first frequency reducing filtration module 220 is used for the digital audio and video signals frequency reducing of frequency Fsc, to produce the digital audio and video signals of a second frequency Fs2.The first frequency reducing filtration module 220 comprises one first upconverter 221, one first filter 222 and one first frequency demultiplier 223.Before the digital audio and video signals of frequency Fsc was imported first filter 222, the first frequency reducing filtration module 220 repeated to receive this digital audio and video signals according to one first parameter A in first upconverter 221, carries out raising frequency with the digital audio and video signals to frequency Fsc.For instance, when first parameter A was 4, digital audio and video signals can repeat input first filter 222 4 times, just with 4 times of digital audio and video signals raising frequencies.After 222 pairs of these digital audio and video signals of first filter carry out filtering, first frequency demultiplier 223 according to one second B parameter with this digital audio and video signals frequency reducing, to produce the digital audio and video signals of second frequency Fs2.For instance, when first parameter A and second B parameter were respectively 2 and 125, second frequency Fs2 was Fsc*2/125.Wherein, first filter 222 can be used comb filter (comb filter), and also available general digital filter is replaced, but is not limited thereto embodiment; For instance, general digital filter can be finite impulse response (FIR) (Finite Impulse Response, FIR) or infinite impulse response (Infinite Impulse Response, IIR) filter.
The second frequency reducing filtration module 240 comprises one first path P1 and one second path P 2.Wherein, have one second filter 241 and one the 3rd frequency demultiplier, 242, the second path P 2 among the first path P1 and then directly export the digital audio and video signals of the 3rd frequency Fs3 to the 3rd frequency reducing filtration module 250.The second frequency reducing filtration module 240 is electrically connected at second frequency demultiplier 232, is used for receiving the digital audio and video signals of the 3rd frequency Fs3.
When the digital audio and video signals of the 3rd frequency Fs3 be a predeterminated frequency Fd (for instance, predeterminated frequency Fd is 48kHz) (2-n) times the time, the second frequency reducing filtration module 240 is directly exported the digital audio and video signals of the 3rd frequency Fs3 via second path P 2, and wherein n is integer.When the digital audio and video signals of the 3rd frequency Fs3 was not predeterminated frequency Fd (2-n) times, the second frequency reducing filtration module 240 was sent to second filter 241 via the first path P1 with the digital audio and video signals of the 3rd frequency Fs3.After 241 pairs of these digital audio and video signals of second filter carried out filtering, the 3rd frequency demultiplier 242 came this digital audio and video signals frequency reducing according to one the 5th parameter E, to produce the digital audio and video signals of one the 4th frequency Fs4.
For instance, suppose that quadruple fixedly falls in the 3rd frequency reducing module 250, when target frequency is 12KHz, 24KHz, 48KHz, 96KHz or 192KHz equifrequent, the digital audio and video signals of the 3rd frequency Fs3 is 48KHz, 96KHz, 192KHz, 384KHz or 768KHz, the 3rd frequency Fs3 be predeterminated frequency (48kHz) (2-0,2-1,2-2,23 or 24) doubly, the second frequency reducing filtration module 240 is directly exported the digital audio and video signals of the 3rd frequency Fs3 via second path P 2; When the digital audio and video signals of the 3rd frequency Fs3 is 832KHz, 1.323MHz, 1.664MHz, 2.646MHz, 3.328MHz, 5.292MHz, 6.656MHz, 10.584MHz, 13.312MHz or 21.168MHz equifrequent, since the 3rd frequency Fs3 be not predeterminated frequency (48kHz) (2-n) doubly, so the second frequency reducing filtration module 240 is sent to second filter 241 via the first path P1 with the digital audio and video signals of the 3rd frequency Fs3.After 241 pairs of these digital audio and video signals of second filter carried out filtering, the 3rd frequency demultiplier 242 came this digital audio and video signals frequency reducing according to the 5th parameter E, to produce the digital audio and video signals of one the 4th frequency Fs4.Wherein, also available comb filter or general digital filter (as above-mentioned FIR or iir filter) replacement of second filter 241.
The 3rd frequency reducing filtration module 250 is electrically connected at this second frequency reducing filtration module 240.The 3rd frequency reducing filtration module 250 comprises an attenuation compensation filter (Drop compensation Filter, DCF) 251,1 the first half band filter (half-band filter) 252,1 the 4th frequency demultiplier 253, one the second half band filter 254 and one the 5th frequency demultiplier 255.The 3rd frequency reducing filtration module 250 can be to because second filter compensates the decay that the radio-frequency head branch of this digital audio and video signals causes.In addition, the 3rd frequency Fs3 that the 3rd frequency reducing filtration module 250 is also exported the second frequency reducing filtration module 240 simultaneously or the further frequency reducing of digital audio and video signals of the 4th frequency Fs4 produce the digital audio and video signals of target frequency Fs at last.In present embodiment, the 4th frequency demultiplier 253 and the 5th frequency demultiplier 255 carry out two times of frequency reducings respectively, so four times of the digital audio and video signals frequency reducings of the 3rd frequency Fs3 that the 3rd frequency reducing filtration module 250 is exported the second frequency reducing filtration module or the 4th frequency Fs4.The frequency reducing multiple of the 4th frequency demultiplier 253 and the 5th frequency demultiplier 255 only is that present embodiment is used, and the user can change the frequency reducing multiple of the 4th frequency demultiplier 253 or the 5th frequency demultiplier 255 according to actual demand.
Moreover the sampling frequency conversion equipment 200 of the audio A C shown in Fig. 2 A only is the embodiments of the invention schematic diagram.Those skilled in the art are when doing different modifications or variation according to this.Please refer to Fig. 2 B, Fig. 2 B is the schematic diagram of the sampling frequency conversion equipment 210 of explanation audio A C of the present invention.Sampling frequency conversion equipment 201 sampling frequency conversion equipment 200 in Fig. 2 A, its different part is that the second frequency reducing filtration module 240 can be combined into a path with two original paths in the lifting frequency module 230, select second filter 241 to be the filter of an adjustable integral coefficient by hardware, the usage factor adjustment makes second filter 241 can become an all-pass filter or a low pass filter.
When the digital audio and video signals of the 3rd frequency Fs3 be a predeterminated frequency Fd (for instance, predeterminated frequency Fd is 48kHz) (2-n) times the time, second filter 241 is all-pass filter by coefficient adjustment, and the 5th parameter E of the 3rd frequency demultiplier 242 is made as 1, make it not carry out filtering and frequency reducing to the digital audio and video signals of the 3rd frequency Fs3, directly export the digital audio and video signals of the 3rd frequency Fs3, wherein n is integer.When the digital audio and video signals of the 3rd frequency Fs3 is not predeterminated frequency Fd (2-n) times, second filter 241 is low pass filter by coefficient adjustment, after 241 pairs of these digital audio and video signals of second filter carry out filtering, the 3rd frequency demultiplier 242 comes this digital audio and video signals frequency reducing according to one the 5th parameter E, to produce the digital audio and video signals of one the 4th frequency Fs4.
In an embodiment of the present invention, first to the 5th parameter A, B, C, D and E calculate resultant according to the target frequency Fs of operating frequency Fsc and setting in advance.Different target frequency Fs and the combination of operating frequency Fsc can produce different first to the 5th parameter A, B, C, D and E.Please refer to simultaneously with reference to figure 2A and Fig. 3.Fig. 3 is the relation table of explanation operating frequency Fsc, target frequency Fs and first to the 5th parameter A, B, C, D and E.Below will utilize the sampling frequency conversion equipment 200 of the audio A C among Fig. 2 A and the relation table of Fig. 3 that the operating frequency Fsc (just not needing extra oscillator or phase-locked loop) how audio A C200 according to the present invention utilizes system's clock pulse to produce is described, simulated audio signal will be converted to the digital audio and video signals of target frequency Fs.Suppose that operating frequency Fsc, target frequency Fs and predeterminated frequency Fd are respectively 6MHz, 64kHZ and 48kHz, first to the 5th parameter A, B, C, D and E are respectively (1,8,71,8,26).SDM210 at first comes simulated audio signal is carried out oversampling according to operating frequency Fsc (6MHz), with the digital audio output signal of output services frequency Fsc (6MHz).Because first parameter A is 1, so the digital audio output signal can transfer to first filter 222 under the situation that does not change (Fsc*1=Fsc).After 222 pairs of these digital audio output signal filtering of first filter, first frequency demultiplier 223 according to second B parameter with 8 times of the digital audio and video signals frequency reducings of operating frequency Fsc (6MHz), with the digital audio and video signals of generation second frequency Fs2, and second frequency Fs2 is 750kHz (6MHz/8=750kHz).Then, second upconverter 231 is according to the digital audio and video signals raising frequency of the 3rd parameters C with second frequency Fs2 (750kHz), then second frequency demultiplier 232 according to the 4th parameter D with this digital audio and video signals frequency reducing, to produce the digital audio and video signals of the 3rd frequency Fs3.Therefore, the 3rd frequency Fs3 is 6656.25kHz (750kHz*71/8=6656.25kHz).Because the digital audio and video signals of the 3rd frequency Fs3 is not 2 of this predeterminated frequency Fd (48kHz)
nDoubly, the second frequency reducing filtration module 240 switches on the first path P1.After 241 pairs of these digital audio output signal filtering of second filter, the 3rd frequency demultiplier 242 with 26 times of the digital audio and video signals frequency reducings of the 3rd frequency Fs3, and produces the digital audio and video signals of the 4th frequency Fs4 according to the 5th parameter E according to this; And the 4th frequency Fs4 is 256kHz (6656.25kHz/26=256kHz).At last, the 3rd frequency reducing filtration module 250 is with four times of the digital audio and video signals frequency reducings of the 4th frequency Fs4, to produce the digital audio and video signals of target frequency Fs (256kHz/4=64kHz).
It is noted that, under the combination of same target frequency Fs and operating frequency Fsc, still may produce first to the 5th parameter A, B, C, D and the E of various combination.For instance, please continue with reference to figure 3, when operating frequency Fsc and target frequency Fs were set at 6MHz and 192kHz respectively, first parameter A can be 16,8 or 4.When first parameter A is 16, when the digital audio and video signals of frequency Fsc is imported first filter 222, can 16 times of first raising frequencies and become 96MHz.Under the existing systems framework, adopt the higher operating frequency of 96MHz in the first frequency reducing module 220, will promote the cost of this circuit design; Also not necessarily there is work time pulse so at a high speed in the system.Therefore the user can to select first parameter A be 8 or 4 to reduce the operating frequency of the first frequency reducing module 220, and the 3rd parameters C also is adjusted into 2 or 4 accordingly.This adjusts the quality that does not influence in output Fs digital audio.
Please refer to Fig. 4.Fig. 4 is the relation table of first to the 5th parameter A, B, C, D and the E of the different operating frequency Fsc of explanation.Audio A C200 of the present invention also can be used for different operating frequency Fsc, as 1.5MHz, 3MHz, 6MHz, 12MHz or 24MHz.Be respectively 12MHz, 96kHZ and 48kHz is example with operating frequency Fsc, target frequency Fs and predeterminated frequency Fd, first to the 5th parameter A, B, C, D and E are respectively (4 or 2,125,1 or 2,1,1).SDM210 at first comes simulated audio signal is carried out oversampling according to operating frequency Fsc (12MHz), with the digital audio output signal of output services frequency Fsc (12MHz).Because first parameter A is 4 or 2, therefore first upconverter 221 is according to the digital audio and video signals raising frequency four times (Fsc*4=48MHz) or two times (Fsc*2=24MHz) of first parameter A with operating frequency Fsc (12MHz).As previously mentioned, the first frequency reducing module 220 adopts higher operating frequency, will promote the cost of this circuit design, and also not necessarily has work time pulse so at a high speed in the system.Therefore, selecting first parameter A is 2 can reduce the operating frequency that first parameter A is 4: first frequency reducing modules 220, and meaning i.e. the 3rd parameters C also is adjusted into 2 accordingly.The digital audio output signal can transfer to first filter 222 under the situation of raising frequency two times (Fsc*2=24MHz).After 222 pairs of these digital audio output signal filtering of first filter, first frequency demultiplier 223 according to second B parameter with 125 times of the digital audio and video signals frequency reducings of operating frequency Fsc (24MHz), with the digital audio and video signals of generation second frequency Fs2, and second frequency Fs2 is 192kHz (24MHz/125=192kHz).Then, second upconverter 231 is according to the digital audio and video signals raising frequency of the 3rd parameters C with second frequency Fs2 (192kHz), then second frequency demultiplier 232 according to the 4th parameter D with this digital audio and video signals frequency reducing, to produce the digital audio and video signals of the 3rd frequency Fs3.Therefore, the 3rd frequency Fs3 is 384kHz (192kHz*2/1=384kHz).Because the digital audio and video signals of the 3rd frequency Fs3 be this predeterminated frequency Fd (48kHz) (23) times, the second frequency reducing filtration module 240 switches on second path P 2, directly to export the digital audio and video signals of the 3rd frequency Fs3 via second path P 2.At last, the 3rd frequency reducing filtration module 250 is with four times of the digital audio and video signals frequency reducings of the 3rd frequency Fs3, to produce the digital audio and video signals of target frequency Fs (384kHz/4=96kHz).
Moreover the sampling frequency conversion equipment 200 shown in Fig. 2 A and Fig. 2 B only is the embodiments of the invention schematic diagram with sampling frequency conversion equipment 201.Those skilled in the art are when doing different modifications or variation according to this.Please refer to Fig. 5 A and Fig. 5 B, wherein, Fig. 5 A is the schematic diagram of the embodiment that changes according to the sampling frequency conversion equipment 200 of Fig. 2 A.The sampling frequency conversion equipment of sampling frequency conversion equipment in Fig. 2 A, its different part is that lifting frequency module 230 can comprise a low pass filter (Low Pass Filter in addition, LPF) 233, be electrically connected between second upconverter 231 and second frequency demultiplier 232, be used for carrying out between raising frequency and the frequency reducing this digital audio and video signals being carried out the filtering of image signal at the digital audio and video signals of this second frequency Fs2.In like manner, please refer to Fig. 5 B, Fig. 5 B is the schematic diagram of the embodiment that changes according to the sampling frequency conversion equipment 201 of Fig. 2 B.The sampling frequency conversion equipment 201 of sampling frequency conversion equipment 501 in Fig. 2 B, its different part is that lifting frequency module 230 can comprise a low pass filter (Low Pass Filter in addition, LPF) 233, be electrically connected between second upconverter 231 and second frequency demultiplier 232, be used for carrying out between raising frequency and the frequency reducing this digital audio and video signals being carried out the filtering of image signal at the digital audio and video signals of this second frequency Fs2.
In the prior art, the sampling frequency when though the APLL150 of the sampling frequency conversion equipment 100 of audio A C can produce corresponding analog/digital conversion according to different audio signals, but an APLL needs the individual logic lock of 500*400 (20k) approximately under the technology of 0.16 micron of general integrated circuit.Under the condition of not having impairment digital audio output quality, the sampling frequency conversion equipment 200 of audio A C of the present invention utilizes a lifting frequency module 230 and one second frequency reducing filtration module 240, and need not use APLL150.Lifting frequency module 230 required logic locks are about 0.3k, and the required logic lock of second filter is about 2K, so the sampling frequency conversion equipment of audio A C of the present invention only need about 2.3k logic lock.Compared to prior art, the sampling frequency conversion equipment of audio A C of the present invention can be saved about 17.7k logic lock, just saves about 88% logic lock number.Therefore, the sampling frequency conversion equipment 200 of audio A C of the present invention takies less circuit area, can effectively reduce cost.
In sum, the invention provides the audio A C of a sampling frequency translation function, the operating frequency that can utilize system's clock pulse to produce is converted to a simulated audio signal digital audio and video signals of one target frequency.Because ADC of the present invention does not need to utilize extra quartz (controlled) oscillator or phase-locked loop to produce sampling frequency, therefore can effectively reduce circuit area and manufacturing cost.
The above only is preferred embodiment of the present invention, and all equalizations of doing according to claim of the present invention change and modify, and all should belong to covering scope of the present invention.
Claims (9)
1. a sampling frequency conversion equipment is applied to an audio frequency simulation digital quantizer, is used for a simulated audio signal is converted to the digital audio and video signals of a target frequency, it is characterized in that described sampling frequency conversion equipment comprises:
One trigonometric integral modulator is used for according to an operating frequency described simulated audio signal being taken a sample, to produce the digital audio and video signals of a first frequency;
One first frequency reducing filtration module, be electrically connected at described trigonometric integral modulator, be used for receiving the digital audio and video signals of described first frequency, and the digital audio and video signals of described first frequency is carried out raising frequency, filtering and frequency reducing, to produce the digital audio and video signals of a second frequency;
One lifting frequency module is electrically connected at the described first frequency reducing filtration module, is used for the digital audio and video signals of described second frequency is carried out raising frequency and frequency reducing, to produce the digital audio and video signals of one the 3rd frequency, when described the 3rd frequency is 2 of predeterminated frequency
nTimes the time, export the digital audio and video signals of described the 3rd frequency; When described the 3rd frequency is not 2 of described predeterminated frequency
nTimes the time, the digital audio and video signals of described the 3rd frequency is carried out filtering and frequency reducing, wherein n is an integer; And
One the 3rd frequency reducing filtration module is electrically connected at described lifting frequency module, be used for to the digital audio and video signals that described lifting frequency module is exported compensate, filtering, frequency reducing, filtering and frequency reducing more again, to export the digital audio and video signals of described target frequency.
2. sampling frequency conversion equipment as claimed in claim 1 is characterized in that, the described first frequency reducing filtration module comprises:
One first upconverter is electrically connected at described trigonometric integral modulator, is used for described digital audio and video signals is carried out raising frequency;
One first filter is used for receiving the described digital audio and video signals behind the raising frequency, and described digital audio and video signals is carried out filtering; And
One first frequency demultiplier is electrically connected at described first filter, is used for the described digital audio and video signals behind the raising frequency is carried out frequency reducing, to produce the digital audio and video signals of a second frequency.
3. sampling frequency conversion equipment as claimed in claim 2 is characterized in that, described first filter is comb type, finite impulse response (FIR) or infinite impulse response filter.
4. sampling frequency conversion equipment as claimed in claim 1 is characterized in that, described lifting frequency module comprises:
One second upconverter is electrically connected at the described first frequency reducing filtration module, is used for the digital audio and video signals of described second frequency is carried out raising frequency;
One second frequency demultiplier is electrically connected at described second upconverter, is used for described digital audio and video signals is carried out frequency reducing, to produce the digital audio and video signals of described the 3rd frequency; And
One second frequency reducing filtration module is electrically connected at described second frequency demultiplier, and whether the digital audio and video signals that receives the digital audio and video signals of the 3rd frequency and differentiate described the 3rd frequency is 2 of a predeterminated frequency
nDoubly, wherein working as described the 3rd frequency is 2 of described predeterminated frequency
nTimes the time, the digital audio and video signals of directly exporting described the 3rd frequency is to described the 3rd frequency reducing filtration module; When described the 3rd frequency is not 2 of described predeterminated frequency
nTimes the time, the digital audio and video signals of described the 3rd frequency is carried out filtering and frequency reducing, export described the 3rd frequency reducing filtration module to the digital audio and video signals that produces one the 4th frequency, wherein n is an integer.
5. sampling frequency conversion equipment as claimed in claim 4, it is characterized in that, the described second frequency reducing filtration module comprises: one first path and one second path, wherein said first path has one second filter, be used for receiving the digital audio and video signals of described the 3rd frequency, and one the 3rd frequency demultiplier, be electrically connected at described second filter, be used for described digital audio and video signals is carried out frequency reducing to produce the digital audio and video signals of one the 4th frequency; Wherein said second path then directly exports the digital signal of the 3rd frequency to described the 3rd frequency reducing filtration module.
6. sampling frequency conversion equipment as claimed in claim 4 is characterized in that, the described second frequency reducing filtration module comprises:
One second filter is used for receiving the digital audio and video signals of described the 3rd frequency, and according to a coefficient settings so that described digital audio and video signals is carried out filtering; And
One the 3rd frequency demultiplier is electrically connected at described second filter, sets so that described digital audio and video signals is carried out frequency reducing according to a parameter;
Wherein working as described the 3rd frequency is 2 of described predeterminated frequency
nTimes the time, adjusting described coefficient is all-pass filter with described second filter configuration, and set described parameter be 1 make described the 3rd frequency demultiplier directly the digital audio and video signals of described the 3rd frequency of output to described the 3rd frequency reducing filtration module; When described the 3rd frequency is not 2 of described predeterminated frequency
nTimes the time, adjusting described coefficient is that low pass filter carries out filtering with described second filter configuration, and set described parameter and make described the 3rd frequency demultiplier to the digital audio and video signals frequency reducing of described the 3rd frequency of filtering, export described the 3rd frequency reducing filtration module to the digital audio and video signals that produces one the 4th frequency.
7. sampling frequency conversion equipment as claimed in claim 4, it is characterized in that, described lifting frequency module comprises a low pass filter in addition, be electrically connected between described second upconverter and described second frequency demultiplier, be used for after the digital audio and video signals of described second frequency carries out raising frequency, described digital audio and video signals being carried out filtering.
8. sampling frequency conversion equipment as claimed in claim 2 is characterized in that, described first upconverter repeats to receive the digital audio and video signals of described first frequency according to one first parameter, makes the digital audio and video signals raising frequency of described first frequency.
9. sampling frequency conversion equipment as claimed in claim 4 is characterized in that, described the 3rd frequency reducing filtration module comprises:
One attenuation compensation filter is electrically connected at the described second frequency reducing filtration module, is used for compensating the digital audio and video signals that the described first frequency reducing filtration module and described lifting frequency module are exported;
One the first half band filter is electrically connected at described attenuation compensation filter, is used for described digital audio and video signals is carried out filtering;
One the 4th frequency demultiplier is electrically connected at described the first half band filters, is used for described digital audio and video signals is carried out frequency reducing;
One the second half band filter is electrically connected at described the 4th frequency demultiplier, is used for described digital audio output signal is carried out filtering; And
One the 5th frequency demultiplier is electrically connected at described the second half band filters, is used for described digital audio and video signals is carried out frequency reducing, sends out digital audio and video signals to produce described target frequency.
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| CN 200910209422 CN102055480B (en) | 2009-10-30 | 2009-10-30 | Sampling frequency conversion device |
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| CN 200910209422 CN102055480B (en) | 2009-10-30 | 2009-10-30 | Sampling frequency conversion device |
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| CN102055480B true CN102055480B (en) | 2013-08-21 |
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| Publication number | Priority date | Publication date | Assignee | Title |
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| CN1402544A (en) * | 2001-08-14 | 2003-03-12 | 瑞昱半导体股份有限公司 | Digital image sampling frequency exchange device and method |
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| Publication number | Priority date | Publication date | Assignee | Title |
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| CN1402544A (en) * | 2001-08-14 | 2003-03-12 | 瑞昱半导体股份有限公司 | Digital image sampling frequency exchange device and method |
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