CN1064496C

CN1064496C - Digital intermediate-frequency enlarge-releasing method and apparatus thereof

Info

Publication number: CN1064496C
Application number: CN96106469A
Authority: CN
Inventors: 周国富; 林�建; 杨文轩
Original assignee: No54 Inst Headquarters Of General Staff P L A
Current assignee: No54 Inst Headquarters Of General Staff P L A
Priority date: 1996-08-12
Filing date: 1996-08-12
Publication date: 2001-04-11
Anticipated expiration: 2016-08-12
Also published as: CN1142148A

Abstract

The present invention relates to a digital intermediate frequency de-enlarging method and an apparatus thereof. The apparatus comprises an intermediate frequency quadrature sampling device 10, a digital signal processor 20 and a clock generating device, wherein the intermediate frequency quadrature sampling device directly samples an input BPSK intermediate frequency signal; the digital signal processor de-enlarges the sampled digital signal; the clock generating device is used for generating a clock required by the intermediate frequency quadrature sampling device 10 and the digital signal processor 20. The method and the apparatus can be used for digitally de-enlarging the BPSK intermediate frequency signals in a spread spectrum communication system, a pulse compression radar system, an IFF system, etc. The apparatus has the advantages of simple structure, wide operating temperature range, high reliability, etc.

Description

Digital intermediate frequency despreading method and device

The present invention relates to a kind of digital solution expanding method and device that is used for Resistant DS Spread Spectrum System, particularly a kind of be used for intermediate frequency directly to BPSK analog signal sampling and digitlization and carry out numeral relevant/digital intermediate frequency despreading method and device that the matched filtering despreading is handled.

Extensively adopted spread spectrum technique, particularly direct sequence spread spectrum skill to obtain using widely in modern communications and the electronic system.In communication system and radar system, adopting a more class Direct Sequence Spread Spectrum Signal is bpsk signal.At present, despreading method to the BPSK spread-spectrum signal mainly contains two kinds, a kind of is the intermediate frequency analog solution expanding method that adopts surface acoustic wave (SAW) device, see document: K Doster and M.Pandit, Performance of SAW tapped delav line in an improved synchronizing circuit, IEEETrans.Commun.Vo1.COM-30, No.1, JAN.1982, pp.219-222 and document: P.W.Baier, K.Doster, and M.Pandit, A novel spread-spectrum receiver synchronization schemeusing a SAW tapped delay line.IEEE Trans.Commun.Vol.COM-30No.5,1982, pp.1037.Another kind is I, the Q orthogonal double channels digital baseband despreading method that adopts digital device, be used for digital correlation/despreading method that thick synchronous head is caught in the Position Location Reporting System (PIRS) as U.S. army, see Liu Xude chief editor " tactical communication, navigator fix and identification integrated system collected works (the 1st collection) ", the Electronic Industry Press, Beijing, in February, 1991, the 195-196 page or leaf.

In intermediate frequency analog solution expanding method, the device that is adopted mainly is SAW correlator, SAW acoustic convolver or SAW storage relevant convolver etc.Though have advantages such as little, the in light weight and processing speed of volume is fast based on the bpsk signal intermediate frequency analog solution enlarging device of SAW device, and obtained using widely, but also there is significant disadvantages in this method, not only debugging is complicated, reliability is restricted, and its performance is acted upon by temperature changes greatlyyer, is not suitable for working under rugged environment.

In the digital baseband despreading method, carry out the despreading processing owing to adopt digital device to replace analogue device, overcome the shortcoming that intermediate frequency analog solution expanding method exists at aspects such as functional reliability, temperature stabilities to a certain extent.But, make circuit structure complicated owing to adopted the quadrature frequency conversion processing; In addition, can not mate fully owing to constitute the twin-channel circuit element of I, Q (comprising frequency mixer, filter etc.), thereby can cause the imbalance of I, Q double-channel signal amplitude and phase place, cause the reduction of systematic function; Also have, in the digital baseband despreading method, still will use more analogue device, therefore, fundamentally do not solve the problem of reliability and through engineering approaches/batch process aspect.

The object of the present invention is to provide a kind of digital intermediate frequency despreading method and device, so that overcome the shortcoming that above-mentioned prior art exists, that the despreading device that is used in the Resistant DS Spread Spectrum System bpsk signal has simultaneously is simple in structure, operating temperature range is wide, use is flexible, reliability is high and advantage such as suitable batch process.

The objective of the invention is by adopting digital intermediate frequency despreading method as described below and device to realize.

A kind of digital intermediate frequency despreading method may further comprise the steps:

A. the BPSK analog intermediate frequency signal to input directly carries out quadrature sampling of medium frequency signal, obtains I, the output of Q binary channels quadrature digital signal, and wherein sample rate satisfies following simultaneous equations: In the formula, f ₀Be bpsk signal IF-FRE, f ₁Be the spreading code bit rate, M and N are positive integer.

B. when M is even number, I, the Q binary channels quadrature digital signal that is obtained by step a directly carried out digital correlation/matched filtering, asks mould and cross the Threshold detection processing, obtain bpsk signal digital intermediate frequency despreading output; When M is odd number, to alternately change the polarity of digital signal in I that step a obtains, each passage of Q binary channels earlier, and then carry out digital correlation/matched filtering, ask mould and cross Threshold detection and handle, obtain bpsk signal digital intermediate frequency despreading output.

A kind of digital intermediate frequency despreading device of realizing as stated above comprises:

A. quadrature sampling of medium frequency signal device, it is input as the BPSK analog intermediate frequency signal, is output as I, Q two-channel digital signal, and it also has a clock control end on the output terminal of clock that is connected to clock-generating device.

B. digital signal processing device, its two inputs are received respectively on the I of described quadrature sampling of medium frequency signal device, the Q two-channel digital signal output part, are output as required bpsk signal digital intermediate frequency despreading output; It also comprises a clock control end on another output terminal of clock that is connected to clock-generating device.

C. clock-generating device that is used to produce quadrature sampling of medium frequency signal device and the required clock of digital signal processing device, its output terminals A and B receive the clock control end of quadrature sampling of medium frequency signal device and digital signal processing device respectively.

Utilize the present invention, the digital intermediate frequency despreading device that is used for the despreading of Resistant DS Spread Spectrum System bpsk signal that adopts analogue device such as A/D converter and field programmable gate array digital devices such as (FPGA) to realize, have simple in structure, operating temperature range is wide, use is flexible and the reliability advantages of higher.The method of the invention and device can be used in the direct sequence spread spectrum communication system despreading to bpsk signal, matched filtering in the biphase coding pulse compression radar and the digital correlation/matched filter processing in the identification of friend or foe, IFF etc.

Below in conjunction with drawings and Examples the present invention is done and to describe in further detail:

Fig. 1 is the overall plan block diagram of device of the present invention.

Fig. 2 is first kind of embodiment of device of the present invention.

Fig. 3 is second kind of embodiment of device of the present invention.

Fig. 4 is the third embodiment of device of the present invention.

Fig. 5 is the 4th kind of embodiment of device of the present invention.

Fig. 6 is the waveform schematic diagram that is used to illustrate first kind of embodiment of the method for the invention.

Fig. 1 is the overall plan block diagram of device of the present invention.As shown in Figure 1, the BPSK analog intermediate frequency signal Si of input produces I, the output of Q two-channel digital signal after quadrature sampling of medium frequency signal device 10 carries out direct intermediate frequency (IF) Sampling and digitlization; I, Q two-channel digital signal by 10 outputs of quadrature sampling of medium frequency signal device are sent to digital signal processing device 20 and handle, produce required digital intermediate frequency despreading output So, clock-generating device 30 produces the required clock signal of quadrature sampling of medium frequency signal devices 10 and digital signal processing device 20.

Embodiment 1

Fig. 2 is first kind of embodiment of device of the present invention, is suitable for comprising the situation of signal phase shifting equipment 11 and M=even number.As shown in Figure 2, quadrature sampling of medium frequency signal device 10 is made up of a signal phase shifting equipment 11 and two A/D converting means 13 and 14.The BPSK analog intermediate frequency signal Si of input produces I, the Q double-channel signal that phase place differs 90 degree each other after 11 phase shifts of signal phase shifting equipment, this two paths of signals is sent to two A/

D converters

13 and 14 respectively and samples and digitlization.A/

D converter

13 and 14 sample rate satisfy following simultaneous equations: In the formula, f ₀Be bpsk signal IF-FRE, f ₁Be the spreading code bit rate, M and N are positive integer;

Such as, if f ₀=10MHz, spreading code bit rate f ₁=5 MHz, N=2, then f _S=10MHz, M=2.

A/D converter 13 and the 14 two-channel digital signals that produce, be sent to one (certainly by field programmable gate array (FPGA) device, also can adopt other universal or special device) digital correlation/matched filtering of constituting, ask mould and cross thresholding checkout gear 22, this device 22 at first is correlated with respectively/matched filter processing to the two-channel digital signal of input, obtain the mould (asking mould) of I, Q two paths of signals then in order simply to adopt approximation method, at last, through comparing, produce final required digital intermediate frequency despreading output So with a detection threshold.In Fig. 2, clock signal A and the B that clock-generating device 30 produces is sent to A/

D converter

13,14 and digital correlation/matched filtering respectively, asks mould and crosses thresholding checkout gear 22 clock signals as them.

Embodiment 2

Fig. 3 is second kind of embodiment of device of the present invention, is suitable for comprising the situation of signal phase shifting equipment 11 and M=odd number.Compare with Fig. 2 of embodiment 1, Fig. 3 just A/

D converter

13 and 14 with digital correlation/matched filtering, ask between mould and the mistake thresholding checkout gear 22 and increased a reversal device 21, other parts are just the same.The effect of reversal device 21 is that A/D converter 13 and the I of 14 outputs, the polarity of Q double-channel signal are changed, and promptly alternately changes the polarity of I, each channel signal of Q binary channels, to obtain correct result; And then the result deliver to the back digital correlation/matched filtering, ask mould and cross thresholding checkout gear 22 and handle, obtain required digital intermediate frequency despread signal So.This embodiment is suitable for the situation of M=odd number, as the situation of M=3.Such as, if f ₀=15MHz, bit rate f ₁=5MHz, N=2, then f _S=10MHz, M=3.

Embodiment 3

Fig. 4 is the third embodiment of device of the present invention, is suitable for comprising the situation of clock phase shifting equipment 12 and M=even number.It is the same with embodiment illustrated in fig. 21 scheme basically, and it just replaces the phase shift of the phase shift of signal being used instead to clock in quadrature sampling of medium frequency signal device 10, that is, increased a clock phase shifting equipment 12 and reduced by a signal phase shifting equipment 11.As shown in Figure 3, quadrature sampling of medium frequency signal device 10 is made up of a clock phase shifting equipment 12 and two A/D converting means 13 and 14.The BPSK analog intermediate frequency signal Si of input directly is sent to two A/

D converters

13 and 14 and is sampled and digitlization.A/

D converter

13 and 14 sample rate are chosen by embodiment 1 same method.A/D converter 13 and the 14 two-channel digital signals that produce also are sent to the back by embodiment 1 same method and handle.

In Fig. 4, clock phase shifting equipment 12 receives the clock signal that produces from clock-generating device 30 output terminals A, produce the two-way clock signal (0 degree and 90 degree) that phase place differs 90 degree each other after 12 phase shifts of clock phase shifting equipment, this two-way clock signal is sent to the clock signal of the input end of clock of A/

D converter

13 and 14 as the A/D converter respectively.Phase phasic difference 90 degree described here are relative bpsk signal IF-FRE.

Embodiment 4

Fig. 5 is the 4th a kind of embodiment of device of the present invention, is suitable for comprising the situation of clock phase shifting equipment 12 and M=odd number.Compare with Fig. 4 of embodiment 3, Fig. 5 just A/

D converter

13 and 14 with digital correlation/matched filtering, ask between mould and the mistake thresholding checkout gear 22 and increased a reversal device 21, other parts are just the same.Among the effect of reversal device 21 and the embodiment 2 is the same.

Embodiment 5

Fig. 6 has provided the waveform schematic diagram of first kind of scheme of explanation the method for the invention, is suitable for input signal Si is carried out the situation of phase shift.In this scheme, the method that realizes quadrature sampling of medium frequency signal is, at first the BPSK analog intermediate frequency signal to input carries out phase shift, produce phase place and differ the 90 binary channels orthogonal simulation signal outputs of spending (phase phasic difference 90 degree described here are the bpsk signal IF-FRE for input) each other, utilize two A/D converters of same clock signal control simultaneously the binary channels analog intermediate frequency signal that produces through phase shift to be sampled and digitlization then, produce I, the output of Q binary channels quadrature digital signal.The sample rate of A/D converter satisfies following simultaneous equations: In the formula, f ₀Be bpsk signal IF-FRE, f ₁Be the spreading code bit rate, M and N are positive integer.

For clear, only provided single pass waveform schematic diagram among Fig. 6.

Among Fig. 6 (a) 41 expression BPSK baseband signal, spreading code bit rate f ₁=5MHz; Fig. 6 (b) expression when M be even number, the BPSK analog intermediate frequency signal 42 and the sampled clock signal 43 of a certain passage during M=2 here, wherein, IF-FRE f ₀=10MHz, sample rate f _S=10MHz, corresponding N=2; Fig. 6 (c) is the digital signal 44 after BPSK intermediate-freuqncy signal 42 shown in Fig. 6 (b) is sampled.As can be seen, because sample rate f _SEqual spreading code bit rate f ₁Integral multiple, and be IF-FRE f ₀Approximate number, therefore, sampled signal 44 can correctly reflect the phase place (identical with baseband signal 41 among Fig. 6 (a) by the envelope of the represented sampled signal of dotted line) of BPSK intermediate-freuqncy signal 42, therefore, by digital correlation/matched filtering, ask mould and cross and can correctly realize the despreading function after Threshold detection is handled.

For clear, supposed the extreme point of sample point among Fig. 6 (b) in the input sinusoidal signal, in fact, because phase of input signals is unknown, so the position of sampled point also is at random.In order to reduce digital intermediate frequency despreading output error rate, need to adopt I, Q binary channels to handle, change detecting Effect on Performance to eliminate the input signal initial phase.For eliminate the code element envelope undesirable cause to the despreading Effect on Performance, in each spreading code code element, should take a sample two or more.From imitate/taking the viewpoint of ratio, a kind of reasonable scheme is sampling 2 points in each code element, promptly gets N=2.

Fig. 6 (b) and the described waveform of Fig. 6 (c) be when M be even number, the situation during M=2 here, when M is not an even number, but odd number during as M=3, need alternately change the polarity of sampled signal, just can obtain correct sampled signal phase place.Fig. 6 (d)～(f) signal has provided waveform in this case.Wherein Fig. 6 (d) represents the BPSK analog intermediate frequency signal 45 and the sampled clock signal 46 of a certain passage when M=3, here, and IF-FRE f ₀=15MHz, sample rate f _S=10MHz, N=2; Fig. 6 (e) is a resulting digital signal 47 after BPSK analog intermediate frequency signal 45 shown in Fig. 6 (d) is sampled, and Fig. 6 (f) is for alternately changing the required sampled signal 48 that obtains after the polarity to digital signal 47 among Fig. 6 (e).As can be seen, it can correctly reflect the phase place (identical with baseband signal 41 among Fig. 6 (a) by the envelope of the represented sampled signal of dotted line) of BPSK analog intermediate frequency signal 45, therefore, by digital correlation/matched filtering, ask mould and cross and can correctly realize the despreading function after Threshold detection is handled.

Embodiment 6

The second kind of scheme that realizes the method for the invention is in intermediate frequency quadrature adopts, to use the phase shift to signal in the phase shift replacement embodiment 5 described first methods of clock.In this scheme, the method that realizes quadrature sampling of medium frequency signal is, at first clock signal is carried out phase shift, produce the two-way clock signal (phase phasic difference 90 degree described here are the bpsk signal IF-FRE for input) that phase place differs 90 degree each other, utilize these two clock signals to control two A/D converters respectively then and simultaneously the BPSK analog intermediate frequency signal of input is sampled and digitlization, produce I, the output of Q binary channels quadrature digital signal.Other parts are identical with the method for embodiment 5.

Claims

1, a kind of digital intermediate frequency despreading method may further comprise the steps:

A. the BPSK analog intermediate frequency signal to input directly carries out quadrature sampling of medium frequency signal, obtains I, the output of Q binary channels quadrature digital signal, and wherein sample rate satisfies following simultaneous equations: In the formula, f ₀Be bpsk signal IF-FRE, f ₁Be the spreading code bit rate, M and N are positive integer;

2, digital intermediate frequency despreading method as claimed in claim 1, it is characterized in that, described quadrature sampling of medium frequency signal is realized by following method: the BPSK analog intermediate frequency signal to input carries out phase shift, produce phase place and differ the 90 binary channels quadrature BPSK analog signal outputs of spending each other, utilize same clock signal simultaneously the binary channels analog intermediate frequency signal that produces through phase shift to be sampled and digitlization then, produce I, the output of Q binary channels quadrature digital signal as the clock of two A/D converters.

3, digital intermediate frequency despreading method as claimed in claim 1, it is characterized in that, described quadrature sampling of medium frequency signal can also be realized by following method: clock signal is carried out phase shift, produce the two-way clock signal that phase place differs 90 degree each other, phase phasic difference 90 degree described here are the bpsk signal IF-FRE for input; Utilize these two clock signals simultaneously the BPSK analog intermediate frequency signal of input to be sampled and digitlization as the clock of two A/D converters respectively then, produce I, the output of Q binary channels quadrature digital signal.

4, digital intermediate frequency despreading method as claimed in claim 1 is characterized in that, the value of described N is that N is more than or equal to 2.

5, a kind of digital intermediate frequency despreading device of realizing as stated above comprises:

A. a quadrature sampling of medium frequency signal device [10], it is input as BPSK analog intermediate frequency signal Si, is output as I, Q two-channel digital signal, and it also has a clock control end on the output terminal of clock A who is connected to clock-generating device [30];

B. a digital signal processing device [20], its two inputs are received respectively on the I of described quadrature sampling of medium frequency signal device [10], the Q two-channel digital signal output part, are output as required bpsk signal digital intermediate frequency despreading output So; It also comprises a clock control end on another output terminal of clock B that is connected to clock-generating device [30];

C. clock-generating device [30] that is used to produce quadrature sampling of medium frequency signal device [10] and the required clock of digital signal processing device [20], its output terminals A and B receive the clock control end of quadrature sampling of medium frequency signal device [10] and digital signal processing device [20] respectively.

6, digital intermediate frequency despreading device as claimed in claim 6 is characterized in that, described quadrature sampling of medium frequency signal device [10] can be made up of following part:

A. a signal phase shifting equipment [11], it is input as BPSK intermediate frequency analog input signal Si, is output as I, the Q binary channels intermediate frequency quadrature analog signal of phase phasic difference 90 degree;

B. two A/D converting means [13] and [14], its input joins with I, the Q binary channels quadrature digital signal output of signal phase shifting equipment [11] respectively, be output as I, Q two-channel digital signal, controlling of sampling is connected on the output terminal of clock A of clock-generating device [30].

7, digital intermediate frequency despreading device as claimed in claim 6 is characterized in that, described quadrature sampling of medium frequency signal device [10] also can be made up of following part:

A. a clock phase shifting equipment [12], its input connects on the input end of clock A of clock-generating device [30], be output as the two-way clock output of phase phasic difference 90 degree, phase phasic difference 90 degree described here are the IF-FRE for the BPSK analog intermediate frequency signal Si of input;

B. two A/D converting means [13] and [14], its input is the BPSK analog intermediate frequency signal of input and counts Si, is output as I, Q binary channels quadrature digital signal, and the controlling of sampling end is connected to respectively in the two-way clock output that clock phase shifting equipment [12] produced.

8, digital intermediate frequency despreading device as claimed in claim 6, it is characterized in that, described digital signal processing device [20] is a digital correlation/matched filtering, asks mould and cross thresholding checkout gear [22], two input connects respectively in two outputs of quadrature sampling of medium frequency signal device [10], produces a required digital intermediate frequency despreading output So; Its input end of clock is connected on the output B of clock-generating device [30].

9, digital intermediate frequency despreading device as claimed in claim 6 is characterized in that, described digital signal processing device [20] is made up of following part:

A. a reversal device [21], two input connect respectively on the I, the output of Q binary channels of quadrature sampling of medium frequency signal device [10], and produce I, the output of Q binary channels;

B. digital correlation/matched filtering, ask mould and cross thresholding checkout gear [22], two input connects respectively in two outputs of reversal device [21], produces a required digital intermediate frequency despreading and exports So; Its input end of clock is connected on the output B of clock-generating device [30].