CN102904594A - Wireless data transmission terminal and intermediate frequency processing method thereof - Google Patents

Wireless data transmission terminal and intermediate frequency processing method thereof Download PDF

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CN102904594A
CN102904594A CN2011102152791A CN201110215279A CN102904594A CN 102904594 A CN102904594 A CN 102904594A CN 2011102152791 A CN2011102152791 A CN 2011102152791A CN 201110215279 A CN201110215279 A CN 201110215279A CN 102904594 A CN102904594 A CN 102904594A
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signal
mixing
alias
data transmission
wireless data
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李庆华
陶雄强
邢益海
闫淑辉
刘建明
李祥珍
胡炜
徐宏
祝锋
邓晓晖
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Potevio Institute of Technology Co Ltd
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Abstract

The invention provides a wireless data transmission terminal. A digital intermediate frequency structure of the wireless data transmission terminal is used for under-sampling processing of intermediate frequency signals, then a complex band-pass filter is used for completing aliasing cancellation and out-of-band rejection, and finally decimation filtering and frequency mixing are carried out. The invention further provides a digital intermediate frequency processing method. The wireless data transmission terminal and the digital intermediate frequency processing method are capable of achieving intermediate frequency signal sampling in the condition of low cost and low power consumption.

Description

A kind of Wireless Data Transmission Terminal and intermediate frequency process method thereof
Technical field
The present invention relates to wireless data transmission technology, relate in particular to a kind of Wireless Data Transmission Terminal and intermediate frequency process method thereof.
Background technology
Traditional wireless data transmission terminal (Wireless Data Transmission Terminal) mainly is used to bear long-range data collection task, usually can use pre-assigned some narrow band frequency resources (bandwidth is 25KHz) to communicate.Communication construction is as shown in Figure 1: 101 expression Wireless Data Transmission Terminals, 102 expression base stations, 103 expression control desks.
Because Wireless Data Transmission Terminal is positioned over the inclement condition area usually, therefore corresponding requirement has been proposed for the service condition of terminal, cost, power consumption etc., be usually expressed as: 1, low cost, 2, low-power consumption, 3, robustness.
The basic intermediate frequency down-conversion structure that general Wireless Data Transmission Terminal adopts in the prior art as shown in Figure 2, comprise intermediate frequency unit (IF) 201, AD conversion unit (AD) 202, frequency mixer 203, cascade integral comb filter (CIC, Cascade Integrator Comb) 204, half-band filter (HB, Half Band filter) 205, HB206, clock (Clock) 207, Direct Digital Synthesizer (DDS, Direct Digital Synthesizer) 208.Cic filter is the cascade of the cascade of simple integral device (accumulator) and comb filter (current sample is delayed time and deduct from current sample), this filter only uses time-delay and add operation, thereby is very suitable for FPGA and ASIC realizes.Half-band filter is that a kind of factor that extracts is 2 withdrawal device, it is zero that nearly half value is arranged in the impulse response of this filter, so the multiplication number of times that finishing filtering needs seldom (lacks half when designing than symmetrical FIR, lacks 3/4ths than any other FIR design multiplication number of times).
Current two if architectures that in state's net power information acquisition terminal project (TD-LTE230 project), adopt based on 455KHz, effective signal bandwidth is 22KHz, channel spacing 25KHz, adopting over-sampling mode (sample rate is 2.4 hundred ten thousand sampled point per seconds (msps)) to carry out signal processes, concrete structure as shown in Figure 3, comprise IF 301, AD 302, frequency mixer 303, CIC 304, limit for length's unit impulse response is arranged (FIR, Finite Impulse Response) filter 305, clock 306 and DDS 307.Wherein CIC 304 carries out sampling in 25: 1, and sample rate is 96,000 sampled point per seconds (ksps), and IFR 305 carries out sampling in 3: 1, and sample rate is 32ksps.
Fig. 4 shows a kind of typical implementation of intermediate frequency down-conversion structure shown in Figure 2.Wherein, intermediate frequency unit is based on 455KHz, and the clock sampling rate is 2.4 hundred ten thousand sampled point per seconds (MSPS), CIC carries out sampling in 25: 1, and sample rate is 96ksps, and two HB all carry out sampling in 2: 1, sample rate is respectively 48ksps and 24ksps, and the sample rate of final output signal also is 24ksps.
The basic process of the if architectures of above data transmission terminal all is that intermediate-freuqncy signal is carried out over-sampling (so-called over-sampling is exactly to use much larger than the frequency of Nyquist sampling frequency input signal to be sampled), and carry out mixing, extract, filtering finally reaches the purpose of obtaining baseband signal.
There are following three problems jointly in the intermediate frequency framework of prior art:
1, over-sampling can improve the precision of A/D converter, but very high to the requirement of data collection, requires sample rate more than 1Msps, usually selects 2Msps or 2.4Msps.
2, sampling rate is high, means the more multiplication of needs or other operand.Therefore too high to the Base-Band Processing Capability Requirement, usually needing to select the special digital signal to process (DSP, Digital Signal Processing) could process by settling signal.
3, filtering must guarantee that the baseband I Q signal can separate with the image signal that 2 times of IF spots form, and in other words, requires filter to possess enough isolation bandwidths.
The problems referred to above then show as in equipment form and production: 1, employed AD belongs to the middle-end grade, and cost is higher, and power consumption is higher.Larger with common low side AD (speed is at 200KSps) difference in selling prices, it is obvious that power consumption differs.2, the rising of adopting DSP will bring terminal cost and power consumption.
Summary of the invention
The invention provides a kind of Wireless Data Transmission Terminal, can under the condition of lower cost and power consumption, realize if signal sampling.
A kind of Wireless Data Transmission Terminal that the embodiment of the invention proposes, the digital-if architecture of described Wireless Data Transmission Terminal is owed sampling processing to intermediate-freuqncy signal, then adopt complex bandpass filters to finish mixed repeatedly the elimination and Out-of-band rejection, carry out again filtering extraction and mixing.
Preferably, described digital-if architecture comprises: intermediate frequency unit, AD conversion unit, clock unit, complex bandpass filters, m:1 extracting unit, frequency mixer and half-band filter;
Described AD conversion unit is for the sample frequency f that provides according to clock unit sIntermediate-freuqncy signal to intermediate frequency unit output is owed sampling, and the output sampled signal;
Described complex bandpass filters is used for the sampled signal of AD conversion unit output is carried out filtering, and exports filtered signal to the m:1 extracting unit;
The signal that the m:1 extracting unit is used for receiving carries out m/one and extracts, with the current mixing sampling rate f that extracts S_bbExport the mixing unit to;
The mixing unit is used for current mixing sampling rate f S_bbCarry out mixing, export the signal after the mixing to half-band filter;
Half-band filter carries out filtering to the signal that receives, output baseband signal f Bb
Preferably, described digital-if architecture further comprises: Surface Acoustic Wave Filter is used for receiving the intermediate-freuqncy signal from intermediate frequency unit, and exports filtered signal to AD conversion unit.
Preferably, the m value of described m:1 extracting unit is 2 or 3.
Preferably, described mixing unit is with current mixing sampling rate f S_bbCentral point frequency f with intermediate-freuqncy signal C_haliasMixing.
Preferably, described mixing unit is to current mixing sampling rate f S_bbThe mode that employing-j rotates successively realizes frequency spectrum shift.
Preferably, during the minimum of computation amount, the AD sample rate f sWith intermediate frequency center frequency f IFAnd final baseband sampling rate f BbRelation satisfy following two equatioies:
f IF＝[(α×γ±η)×M±1]×β×f bb；
f IF＝(γ±1/L)×f s；
Wherein, γ is order | f C_alias| get the natural number of minimum value, f C_aliasSatisfy following condition: f C_alias=f IF± γ * f sf s=α * f S_bb, f S_bb=β * f Bb, α, β are natural number;
f C_aliasImage frequency f C_haliasSatisfy f C_halias=f C_alias± η * f S_bb, wherein, η is for making | f C_halias| get the natural number of minimum value; f C_alias* L=± f s, wherein L is less natural number; f C_haliasWith current mixing sampling rate f S_bbRatio satisfies f C_halias* M=± f S_bb, M is natural number.
Preferably, the relation of the parameters of the sampling rate of described base band speed, AD conversion unit and plural pass filter is as shown in the table
Figure BDA0000079707670000041
The embodiment of the invention also proposes a kind of Digital IF Processing method, comprises the steps:
A, owe sampling processing to intermediate-freuqncy signal;
B, the signal that adopts complex bandpass filters to obtain owing to sample mix repeatedly to be eliminated and Out-of-band rejection;
C, the signal after step B processed carry out filtering extraction and mixing.
As can be seen from the above technical solutions, owe sampling processing to intermediate-freuqncy signal.Carry out first plural bandpass filtering, erasure signal is repeatedly mixed, then filtering extraction and mixing, thereby the baseband signal of obtaining.Intermediate-freuqncy signal and sample rate, baseband signal speed satisfy under the prerequisite of certain relation, and it is optimum that operand can reach.
Description of drawings
Fig. 1 is the arrowband radio station network structural representation of prior art;
Fig. 2 is the digital-if architecture schematic diagram of wireless universal data transmission terminal in the prior art;
Fig. 3 is the digital-if architecture schematic diagram of the Wireless Data Transmission Terminal of existing state net 230 projects;
Fig. 4 is the digital-if architecture schematic diagram of a kind of Wireless Data Transmission Terminal in the prior art;
Fig. 5 is a kind of digital-if architecture schematic diagram of the Wireless Data Transmission Terminal of embodiment of the invention proposition;
Fig. 6 is the digital-if architecture schematic diagram of the Wireless Data Transmission Terminal of state's net 230 projects of proposing of the embodiment of the invention;
Fig. 7 is the digital-if architecture schematic diagram of a kind of operand minimum of embodiment of the invention proposition;
Fig. 8 is that the intermediate-freuqncy signal of the embodiment of the invention owes sampling mixed repeatedly figure;
Fig. 9 is the complex bandpass filters design amplitude response figure of the embodiment of the invention
Figure 10 is the digital-if architecture schematic diagram of the another kind of minimum computing of the embodiment of the invention.
Embodiment
The digital-if architecture of the Wireless Data Transmission Terminal of prior art is difficult to guarantee that the centre frequency mirror image of signal separates with the zero-frequency baseband signal, and it is as follows specifically to derive:
The function that digital-if architecture realizes is from center mirror image frequency f with intermediate-freuqncy signal C_alias(frequency itself centered by the over-sampling mode) moves zero-frequency.If baseband signal is φ (t), bandwidth is f φ(this routine channel width 25Khz, single-side belt are 12.5Khz), sample frequency is f s, then the discrete signal after the AD sampling is: cos (2 π f C_alias+ φ (t)).
The baseband I that need to obtain, Q road signal are: cos (φ (t)), and sin (φ (t)), the design of obtaining the IQ signal is as follows:
I road obtain manner: with AD sampled signal and cos (2 π f C_alias) multiply each other, it is as follows to obtain the result:
I_mult＝cos(2πf C_alias+φ(t))×cos(2πf C_alias)
＝cos(2πf C_alias)×cos(2πf C_alias)×cos(φ(t))-sin(2πF C_alias)×cos(2πf C_alias)×sin(φ(t))＝(1+cos(4πf C_alias))/2×cos(φ(t))-sin(4πf C_alias)/2×sin(φ(t))
＝cos(φ(t))/2+[cos(4πf C_alias)×cos(φ(t))-sin(4πf C_alias)×sin(φ(t))]/2
＝cos(φ(t))/2+[cos(4πf C_alias+φ(t))]/2
Q road obtain manner: with AD sampled signal and sin (2 π f C_alias) multiply each other, it is as follows to obtain the result:
Q_mult＝cos(2πf C_alias+φ(t))×sin(2πf C_alias)
＝sin(2πf C_alias)×cos(2πf C_alias)×cos(φ(t))-sin(2πf C_alias)×sin(2πf C_alias)×sin(φ(t))＝sin(4πf C_alias)/2×cos(φ(t))-(1-cos(4πf C_alias))/2×sin(φ(t))
＝-sin(φ(t))/2+[cos(4πf C_alias)×cos(φ(t))+sin(4πf C_alias)×sin(φ(t))]/2
＝-sin(φ(t))/2+[cos(4πf C_alias-φ(t))]/2
I_mult is separated with twice image signal among the Q_mult
Can learn that from the expression formula of I_mult it is 2f by point if add low pass filter C_alias-f φ, then can accurately separate and obtain I road signal.In like manner, the Q_mult signal is being 2f through cut-off point C_alias-f φLow pass filter, can the complete Q road signal that obtains.
Owing to there is 2f C_alias-f φ＞f sSituation, this moment the signal folded situation can occur, signal enters [f by new mirror image s/ 2, f s/ 2], the centre frequency of the signal location of filtering this moment becomes | 2f C_alias-f s|, occupied bandwidth becomes: [2f C_alias-f φ-f s, 2f C_alias+ f φ-f s].If above-mentioned separation can not be successful, then must choose other sample rate and just can finish Digital Down Convert, and this be unacceptable in some cases.
The present invention proposes to adopt complex bandpass filters+frequency mapping mode to carry out the down-conversion scheme.The situation of aliasing occurs for available technology adopting DDS frequency conversion scheme in this scheme easily, and aliasing can't occur.Core concept of the present invention is:
A, owe sampling processing to intermediate-freuqncy signal;
B, the signal that adopts complex bandpass filters to obtain owing to sample mix repeatedly to be eliminated and Out-of-band rejection;
C, the signal after step B processed carry out filtering extraction and mixing.
Intermediate-freuqncy signal and sample rate, baseband signal speed satisfy under the prerequisite of certain relation, and it is optimum that operand can reach.
The present invention program's main feature comprises: 1, adopt low rate AD that intermediate-freuqncy signal is sampled.2, signal is processed simply, and operand is little.3, the mixing unit is satisfying under the certain condition and can cancel, and perhaps only has limited several values to participate in computing.
For the characteristics, the effect that make technical solution of the present invention is clearer, below by specific embodiment the present invention program is further elaborated.
The essential characteristic of the if architectures of the Wireless Data Transmission Terminal that the embodiment of the invention proposes is as follows: at first carry out the midband pass filter before the frequency conversion, state no interference signal occurs after the assurance mixing; Then carry out the signal reduce sampling frequency and extract, carry out at last the simple filtering extraction of mixing and afterbody.This scheme can effectively avoid since sample frequency and IF-FRE choose improper, the situation of the useful signal that causes and baseband signal aliasing.
The if architectures of a kind of data transmission terminal that the embodiment of the invention proposes as shown in Figure 5, comprise that IF 501, surface acoustic wave (SAW, Surface Acoustic Wave) filter 502, AD conversion unit (AD) 503, clock 504, plural number band logical (Complex Passband) have limit for length's unit impulse response filter (FIR) 505, extracting unit 506, mixing unit 507 and half-band filter 508.The effect of Surface Acoustic Wave Filter 502 is that the signal of inputting is resisted mixed repeatedly filtering.SAW increases and the elastic wave that reduces rapidly in the degree of depth that the piezoelectric substrate material surface produces and propagates and amplitude gos deep into substrate material.The basic structure of SAW filter is to make two acoustic-electrical transducers---interdigital transducer (IDT) at the substrate material burnishing surface with piezoelectric property.It adopts the planar technique of semiconductor integrated circuit, and at the certain thickness aluminium film of piezoelectric substrate surface evaporation, the mask pattern two IDT that design utilizes photoetching method to be deposited on substrate surface, respectively as input transducer and output transducer.Its operation principle is that the input transducer becomes the signal of telecommunication into acoustical signal, propagates along plane of crystal, and output transducer becomes the acoustical signal that receives signal of telecommunication output again.
In this if architectures, AD conversion unit 503 is for the sample frequency f that provides according to clock unit sIntermediate-freuqncy signal to intermediate frequency unit output is owed sampling, and the output sampled signal.The logical FIR 505 of plural number band carries out plural bandpass filtering, then carries out the m:1 extraction by extracting unit 506 and obtains current mixing sampling rate f S_bb, the current mixing sampling rate f that mixing unit 507 obtains extraction S_bbWith limited sampling signal f C_haliasCarry out mixing, carry out filtering by half-band filter 508 at last, realize intermediate-freuqncy signal f IFTo baseband signal f BbConversion.Wherein, f C_alias=ω=f IF-nf s
The baseband filter sample frequency is f s, passband is [f φ, f φ], the passband value can be [12.5k, 12.5k] in the present embodiment, rejection zone is set according to actual conditions, is set as 16khz in this example.
Set multiple coefficient of rotary, twiddle factor is: Rot_f c=2f C_alias/ f sThe coefficient of baseband filter is multiplied each other successively
Figure BDA0000079707670000081
The coefficient numbering of (n) expression filter wherein increases progressively successively take 0 as substrate, and increment is 1.The coefficient of baseband filter after multiplying each other through multiple coefficient of rotary is desired band pass filter.After input signal carries out complex filter, this signal is carried out frequency spectrum shift, move to be embodied as each point (complex signal) is rotated
Figure BDA0000079707670000082
F wherein C_haliasF C_aliasMirror image on current sampling frequency, f C_haliasSatisfy f C_halias=f C_alias± η * f S_bb, wherein η is for making | f C_halias| get the natural number of minimum value, carry out rate-matched according to the situation of sample rate and base band speed.
Fig. 6 shows state's net 230 digital-if architecture that the embodiment of the invention provides, comprise IF 601, AD602, clock 603, plural Hilbert FIR (Complex Hilbert HIR) 604,2:1 extracting unit 605, frequency mixer 606, sampling DDS607, HB 608.Wherein, the centre frequency of the intermediate-freuqncy signal that IF601 receives is 454KHz or 456KHz, and the sample frequency of clock 603 is 128ksps, and plural Hilbert HIR604 is passband 25k filter.Compare with Fig. 5, omitted AD SAW filter before.
The digital-if architecture of a kind of operand minimum that the embodiment of the invention proposes as shown in Figure 7, comprise that sample rate is IF701, the AD702 of 450KHz, the clock 703 that sample rate is 120ksps, plural Hilbert FIR704,3:1 extracting unit 705, frequency mixer 706, and the HB707 of 2:1 extraction.The special character of this embodiment is that the mode that frequency mixer 706 directly rotates successively to IQ the data-j realizes frequency spectrum shift, has saved various basic operations, only needs simple imaginary part real part exchange to get final product.
The present invention finishes the actual signal analog domain to the conversion of numeric field by owing sample mode, so two schemes medium-frequency transformation design main points are as follows:
Owing sample mode when employing is that the signal of 455KHz frequency is with f to centre frequency sWhen sample rate was sampled, the signal of 455KHz will be at [n*f s, (n+1) * f s] the interior image signal that forms, wherein
Figure BDA0000079707670000091
Concrete condition can owe sampling mixed repeatedly figure referring to intermediate-freuqncy signal shown in Figure 8.
Because intermediate-freuqncy signal before entering the AD sampling, is understood a simulation of cascade Surface Acoustic Wave Filter (SAW Filter) usually, pass band width is 25KHz, so when owing to sample, do not have the signal aliasing situation.Owing to adopt the 128KSps sampling, can learn that according to upper figure the mirror image center frequency point of actual signal in [64k, 64k] scope is ω=f IF-4f s=-57khz.Therefore only need to carry out mixing according to center frequency point-57KHz, can finish obtaining of quadrature IQ signal.
In detail design of filter amplitude response figure as shown in Figure 9, after input signal is carried out complex filter, signal formation standard I Q signal, this moment, signal still be bandpass signal, but signal is pure at this moment, does not have the signal aliasing problem.Owing to adopt the method for complex filter not have aliasing, the method computation reduction that therefore filtering and extraction can be merged.
Work as sample rate, IF-FRE, base band frequency satisfy when necessarily concerning, can greatly simplified operation.Core point is as follows:
1, because Rot_f c=2f C_alias/ f s, the baseband filter coefficient will according to
Figure BDA0000079707670000092
Mode multiplies each other.If f C_aliasBe f s1/8,1/4,3/8, then coefficient of rotary is j nForm or
Figure BDA0000079707670000093
Form, operand is minimum.This principle can be summarized as f C_alias* L=± f s, L is less natural number, then simplified operation significantly.
2, owing to final mixing need to be taken advantage of each filtered complex sequences
Figure BDA0000079707670000101
If current center frequency point frequency f C_halias(f C_aliasImage frequency) with current mixing sampling rate f S_bbRatio satisfies f C_halias* M=± f S_bb, M is less natural numerical value, then can significantly reduce operand.When M=2, then sequence becomes-j n, do not have operand.
3, because f C_aliasSatisfy following condition: f C_alias=f IF± γ * f s, wherein γ is order | f C_alias| get the natural number of minimum value.And f s=α * f S_bb, f S_bb=β * f Bb, α, β are natural number, f BbBe base band speed.f C_haliasSatisfy f C_halias=f C_alias± η * f S_bb, wherein η is for making | f C_halias| get the natural number of minimum value.
Therefore, the intermediate frequency center frequency f of selection IF, the AD sample rate f s, base band speed f Bb(f s=α * β * f Bb, α, β are natural number) and according to above-mentioned multiple relation (M=2, L=4), can the operand minimum.The minimum relation of the mixing operand of deriving at present is as follows:
f IF＝[(α×γ±η)×M±1]×β×f bb；
And the complex filter operand is minimum, also need satisfy following condition:
f IF＝(γ±1/L)×f s。
A kind of optimal situation as shown in figure 10, wherein:
Base band speed f Bb=20k, sample rate f s=120k, centre frequency f IF=450k.
Therefore, f C_alias=-30k, and Rot_f c=-1/2, f C_halias=-30+40=10k.Because f C_halias* 2=f Bb, so the mixing operand is reduced to-the j computing.
α in this example=3, β=2, M=2, L=4, and γ=4, η=1.
Table 1 has been listed several particular sample rates and frequency conversion realization parameter that the present invention recommends, specifically is listed as follows:
Table 1
Key point of the present invention is: adopt and to owe sample mode and carry out Digital Down Convert, and adopt and extract after the first filtering and the structure of mixing.
Advantage of the present invention is: 1, the sample rate of AD required obviously to descend.The requirement of the operand of 2, signal being processed also obviously descends.3, can adopting cheaply, mixed signal MCU (single-chip microcomputer) realizes the signal processing.4, there is not the mixed repeatedly problem of the signalling mirror picture that may exist after the mixing of conventional digital intermediate frequency.
The above only is preferred embodiment of the present invention, and is in order to limit the present invention, within the spirit and principles in the present invention not all, any modification of making, is equal to replacement, improvement etc., all should be included within the scope of protection of the invention.

Claims (9)

1. Wireless Data Transmission Terminal, it is characterized in that, the digital-if architecture of described Wireless Data Transmission Terminal is owed sampling processing to intermediate-freuqncy signal, and the signal that then adopts complex bandpass filters to obtain owing to sample mixes repeatedly to be eliminated and the Out-of-band rejection processing, carries out filtering extraction and mixing again.
2. described Wireless Data Transmission Terminal according to claim 1 is characterized in that described digital-if architecture comprises: intermediate frequency unit, AD conversion unit, clock unit, complex bandpass filters, m:1 extracting unit, frequency mixer and half-band filter;
Described AD conversion unit is for the sample frequency f that provides according to clock unit sIntermediate-freuqncy signal to intermediate frequency unit output is owed sampling, and the output sampled signal;
Described complex bandpass filters is used for the sampled signal of AD conversion unit output is carried out filtering, and exports filtered signal to the m:1 extracting unit;
The signal that the m:1 extracting unit is used for receiving carries out m/one and extracts, with the current mixing sampling rate f that extracts S_bbExport the mixing unit to;
The mixing unit is used for current mixing sampling rate f S_bbCarry out mixing, export the signal after the mixing to half-band filter;
Half-band filter carries out filtering to the signal that receives, output baseband signal f Bb
3. Wireless Data Transmission Terminal according to claim 2 is characterized in that, described digital-if architecture further comprises: Surface Acoustic Wave Filter is used for receiving the intermediate-freuqncy signal from intermediate frequency unit, and exports filtered signal to AD conversion unit.
4. Wireless Data Transmission Terminal according to claim 2 is characterized in that, the m value of described m:1 extracting unit is 2 or 3.
5. Wireless Data Transmission Terminal according to claim 2 is characterized in that, described mixing unit is with current mixing sampling rate f S_bbWith signal f C_haliasMixing, wherein f C_haliasF C_aliasMirror image on current sampling frequency, f C_haliasSatisfy f C_halias=f C_alias± η * f S_bb
6. Wireless Data Transmission Terminal according to claim 2 is characterized in that, described mixing unit is to current mixing sampling rate f S_bbThe mode that employing-j rotates successively realizes frequency spectrum shift.
7. Wireless Data Transmission Terminal according to claim 6 is characterized in that, during the minimum of computation amount, and the AD sample rate f sWith intermediate frequency center frequency f IFAnd final baseband sampling rate f BbRelation satisfy following two equatioies:
f IF＝[(α×γ±η)×M±1]×β×f bb；
f IF＝(γ±1/L)×f s；
Wherein, γ is order | f C_alias| get the natural number of minimum value, f C_aliasSatisfy following condition: f C_alias=f IF± γ * f sf s=α * f S_bb, f S_bb=β * f Bb, α, β are natural number;
f C_aliasImage frequency f C_haliasSatisfy f C_halias=f C_alias± η * f S_bb, wherein η is for making | f C_halias| get the natural number of minimum value; f C_alias* L=± f s, wherein L is less natural number; f C_haliasWith current mixing sampling rate f S_bbRatio satisfies f C_halias* M=± f S_bb, M is natural number.
8. according to claim 1 to 6 each described Wireless Data Transmission Terminals, it is characterized in that the relation of the sampling rate of described base band speed, AD conversion unit and the parameters of plural pass filter is as shown in the table
Figure FDA0000079707660000021
Figure FDA0000079707660000031
。
9. a Digital IF Processing method is characterized in that, comprises the steps:
A, owe sampling processing to intermediate-freuqncy signal;
B, the signal that adopts complex bandpass filters to obtain owing to sample mix repeatedly to be eliminated and the Out-of-band rejection processing;
C, the signal after step B processed carry out filtering extraction and mixing.
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CN104853442A (en) * 2014-02-18 2015-08-19 普天信息技术有限公司 Wireless resource rapid scheduling method and system and access equipment
CN107276638A (en) * 2017-05-27 2017-10-20 南京航空航天大学 SAW reader receives link structure and its method of work based on direct lack sampling digital quadrature demodulation scheme
CN108548958A (en) * 2018-03-30 2018-09-18 南京国睿安泰信科技股份有限公司 A kind of rapid frequency-sweeping system and method for spectrum detector
CN111917428A (en) * 2020-07-21 2020-11-10 湖南拉盖尔电子科技有限公司 Digital intermediate frequency signal rapid baseband and down-sampling method
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