CN103117769A - Method for improving signal-to-noise ratio of de-spreading noises in satellite spread spectrum communication receiver, and receiver - Google Patents

Abstract

The invention relates to a method for improving signal-to-noise ratio of de-spreading noises in a satellite spread spectrum communication receiver, and a receiver. The method includes: generating QPSK (quadrature phase shift keying) baseband copied signals according to QPSK signal demodulation data, and using the QPSK baseband copied signals to counteract QPSK baseband signal components in baseband signals. Therefore, the signal-to-noise ratio of spread spectrum signals after de-spreading is increased and spread spectrum communication quality is improved. While spread spectrum gain of spread spectrum signals is unchanged, transmitting power of a spread spectrum transmitter can be lowered, the influence of spread spectrum signals on QPSK signals can be reduced, and invisibility of the spread spectrum signals can be improved. While signal-to-noise ratio of the spread spectrum signals after de-spreading is unchanged, spreading coefficient of the spread spectrum signals can be decreased, and transmission rate of a spread spectrum communication system can be increased.

Description

Improve method and the receiver of satellite spectrum-spread communication receiver despread signal signal to noise ratio

Technical field

The present invention relates to satellite communication, radio communication, spread spectrum communication, modulation /demodulation field.

Background technology

In satellite communication system shown in Figure 1, s ₁(t) be the QPSK modulation upward signal of transmitter 1 emission, s ₂(t) be the band spectrum modulation upward signal of transmitter 2 emissions.s ₁(t) and s ₂(t) take essentially identical frequency and bandwidth, but s ₂(t) amplitude degree compares s ₁(t) low many, thus s guaranteed ₂(t) to s ₁(t) impact of transmission is very little.Fig. 2 is supposition s ₁(t) Amplitude Ratio s ₂(t) power spectrum signal (the high 26dB of power) during high 20 times of amplitude.s ₁(t), s ₂(t) after the frequency translation of signal process communication satellite coverage, form QPSK modulation downstream signal r ₁(t) and band spectrum modulation downstream signal r ₂(t), r ₁(t), r ₂(t) also take essentially identical frequency and bandwidth, keep and s ₁(t), s ₂(t) identical signal amplitude relation.

QPSK modulation downstream signal r ₁Mathematic(al) representation as shown in Equation 1:

$r_1\left(t\right)=A\left\{\right[\underset{k=-\∞}{\overset{+\∞}{\mathrm{\Σ}}}{a}_{\mathrm{Ik}}{h}_1(t-{\mathrm{kT}}_1)]\cos \left({\mathrm{\ω}}_{1}t\right)+[\underset{k=-\∞}{\overset{+\∞}{\mathrm{\Σ}}}{a}_{\mathrm{Qk}}{h}_1(t-k{T}_1)\left]\sin \left({\mathrm{\ω}}_{1}t\right)\right]\}$ (formula 1)

Wherein, A is the amplitude of qpsk modulation signal, and its value is for just; a _Ik, a _QkBe respectively the data message of I road in qpsk modulation signal, Q road transmission, value is ± 1; h ₁(t-kT ₁) be the pulse shock response that transmits, its corresponding frequency response function is that rolloff-factor is α ₁The square root raised cosine function, α ₁Span between 0～1; T ₁A _IkAnd a _QkCode-element period, 1/T ₁It is the baud rate of QPSK signal; ω ₁=2 π f ₁It is the angular frequency of QPSK carrier signal.

Band spectrum modulation downstream signal r ₂Mathematic(al) representation as shown in Equation 2:

$r_2\left(t\right)=B\left\{\right[\underset{k=-\∞}{\overset{+\∞}{\mathrm{\Σ}}}{b}_{\mathrm{Ik}}\left(t\right)m_i\left(t\right)h_2(t-{\mathrm{kT}}_2)]\cos \left({\mathrm{\ω}}_{2}t\right)+[\underset{k=-\∞}{\overset{+\∞}{\mathrm{\Σ}}}{b}_{\mathrm{Qk}}\left(t\right)m_q\left(t\right)h_2(t-k{T}_2)\left]\sin \left({\mathrm{\ω}}_{2}t\right)\right\}$

(formula 2)

Wherein, B is the amplitude of modulated spread spectrum signal, and its value is always for just; b _Ik, b _QkBe respectively the data message of modulated spread spectrum signal I road, Q road transmission, value is ± 1; m _i(t), m _q(t) be the frequency expansion sequence on modulated spread spectrum signal I road, Q road, value is ± 1, its nominal rate and r ₁(t) a _IkAnd a _QkIdentical; m _i(t), m _q(t) speed is far longer than b _Ik, b _QkSpeed, m _i(t), m _q(t) and b _Ik, b _QkThe ratio of speed is called spread spectrum coefficient k(or spreading gain); h ₂(t-kT ₂) be the pulse shock response that transmits, its corresponding frequency response function is α for rolloff-factor ₂The square root raised cosine function, α ₁Span between 0～1; T ₂M _i(t), m _q(t) code-element period, 1/T ₂Its baud rate, its nominal value and T ₁Identical; ω ₂=2 π f ₂The angular frequency of signal, its nominal value and ω ₁Identical.Receiver input signal r (t) is as shown in Equation 3:

R (t)=r ₁(t)+r ₂(t)+n (t) (formula 3)

Wherein, n (t) is Gaussian noise.Receive modulated spread spectrum signal r ₂(t) during signal, the wideband qpsk modulation signal can r ₁(t) equivalence is Gaussian noise.If adopt usual manner demodulation modulated spread spectrum signal r ₂(t), the signal to noise ratio after its despreading as shown in Equation 4.

(formula 4)

Wherein, k is spread spectrum coefficient.By formula 4 as seen, in order to improve r ₂(t) signal to noise ratio after despreading can increase k, r ₂(t), perhaps reduce r ₁(t), n (t).Increase the transmission rate that k can reduce spread spectrum system; Increase r ₂(t) amplitude can affect r ₁(t) transmission quality; Determine when the receiving system noise factor, n (t) is determined value, can't arbitrarily reduce; If can find a kind of method, under the condition that does not change existing parameter, reduce r ₁(t) impact just can improve r ₂(t) signal to noise ratio after despreading.

Summary of the invention

The objective of the invention is to cover under condition in the QPSK large-signal that takies same frequency, same frequency band, improve satellite band spread receiver despread signal signal to noise ratio, improve communication spread spectrum quality.

For addressing the above problem, the invention provides a kind of by QPSK signal demodulating data generation QPSK base band reproducing signals, then use the QPSK baseband signal component in QPSK base band reproducing signals counteracting baseband signal, thereby improve the method for satellite spectrum-spread communication receiver despread signal signal to noise ratio, comprising:

One input signal splitter of receiver obtains input signal, and described input signal is divided into the equal described input signal of two-way, the described input signal in each road is QPSK modulation downstream signal, band spectrum modulation downstream signal and Gaussian noise sum, and wherein QPSK modulation downstream signal is far longer than the band spectrum modulation downstream signal;

The carrier synchronization of the local oscillator carrier wave that one local oscillator of receiver produces and QPSK modulation downstream signal, local frequency equals the carrier frequency of QPSK modulation downstream signal, and the orthogonal local oscillation signal of local oscillator output multiplies each other with every road input signal respectively and exports I road difference frequency and frequency signal and Q road difference frequency and frequency signal;

I road, Q road and frequency signal in the one QPSK Signal Matching filter of described receiver, the 2nd QPSK Signal Matching filter difference filtering described I road difference frequency and frequency signal and Q road difference frequency and frequency signal, export described I road, Q road difference frequency signal as I road, Q roadbed band signal, described I road, Q roadbed band signal are QPSK baseband signal, spread baseband signal and Gaussian noise sum, and wherein the amplitude of QPSK baseband signal is far longer than spread baseband signal;

One qpsk demodulator of described receiver is exported respectively I road, Q road QPSK demodulating data according to described I road, Q roadbed band signal;

One the 3rd QPSK matched filter of described receiver, the 4th QPSK matched filter are respectively according to described I road, QPSK demodulating data output I road, Q road, the Q road QPSK baseband signal of regenerating;

One amplitude adjusting circuit of described receiver is adjusted first, second, and third pair of QPSK base band reproducing signals of parameter output according to described I road, Q road QPSK regeneration baseband signal and first, second, and third amplitude, and with second pair of QPSK base band reproducing signals as the optimal compensation QPSK base band reproducing signals, first pair of QPSK base band reproducing signals is as overcompensation QPSK base band reproducing signals, and the 3rd pair of QPSK base band reproducing signals is as undercompensation QPSK base band reproducing signals;

One signal delay module of described receiver is fixed time-delay to described I road, Q roadbed band signal respectively, and I road, Q roadbed band signal and QPSK base band reproducing signals after time-delay are complementary in time;

After one signal cancellation module of described receiver will be delayed time respectively, I road, the rear Q roadbed band signal of time-delay subtract each other with described first, second, and third pair of QPSK base band reproducing signals respectively, export first, second, and third pair of spread baseband signal;

One signal to noise ratio module of described receiver is carried out respectively despreading to described first, second, and third pair of spread baseband signal, and calculates and export first, second, and third despread signal signal to noise ratio;

One control logic circuit of described receiver is adjusted described first, second, and third amplitude according to described first, second, and third despread signal signal to noise ratio and is adjusted parameter, and control the signal to noise ratio module and adjust first, second, and third corresponding despread signal signal to noise ratio, until being maximum and the first and second despread signal signal to noise ratios, the second despread signal signal to noise ratio equates.

Further, in said method, if QPSK signal data information is processed through error correction coding, described the 3rd QPSK matched filter, the 4th QPSK matched filter comprise according to the step of described I road, QPSK demodulating data output I road, Q road, Q road QPSK regeneration baseband signal respectively:

One channel error correcting deocder of described receiver encodes to generate I road, Q road coded data again after with described I road, Q road QPSK demodulating data error-correcting decoding again, and described the 3rd QPSK matched filter, the 4th QPSK matched filter are according to described I road, Q road coded data output I road, the Q road QPSK baseband signal of regenerating again.Due to after error-correcting decoding again coded data have the lower error rate (usually will hang down 3 above orders of magnitude) than demodulating data, have less distortion by the regeneration baseband signal of its generation.

Further, in said method, the formula of described input signal is as follows:

The formula of described input signal is as follows:

$r\left(t\right)=A\left\{\right[\underset{k=-\∞}{\overset{+\∞}{\mathrm{\Σ}}}{a}_{\mathrm{Ik}}{h}_1(t-{\mathrm{kT}}_1)]\cos \left({\mathrm{\ω}}_{1}t\right)+[\underset{k=-\∞}{\overset{+\∞}{\mathrm{\Σ}}}{a}_{\mathrm{Qk}}{h}_1(t-k{T}_1)\left]\sin \left({\mathrm{\ω}}_{1}t\right)\right]\}$

$+B\left\{\right[\underset{k=-\∞}{\overset{+\∞}{\mathrm{\Σ}}}{b}_{\mathrm{Ik}}\left(t\right)m_i\left(t\right)h_2(t-{\mathrm{kT}}_2)]\cos \left({\mathrm{\ω}}_{2}t\right)+[\underset{k=-\∞}{\overset{+\∞}{\mathrm{\Σ}}}{b}_{\mathrm{Qk}}\left(t\right)m_q\left(t\right)h_2(t-k{T}_2)\left]\sin \left({\mathrm{\ω}}_{2}t\right)\right\}$

$+n\left(t\right)$

$=r_1\left(t\right)+r_2\left(t\right)+n\left(t\right)$

Wherein, r (t) is input signal, r ₁Be QPSK modulation downstream signal, r ₂Be the band spectrum modulation downstream signal, n (t) is Gaussian noise;

r ₁Formula as follows:

$r_1\left(t\right)=A\left\{\right[\underset{k=-\∞}{\overset{+\∞}{\mathrm{\Σ}}}{a}_{\mathrm{Ik}}{h}_1(t-{\mathrm{kT}}_1)]\cos \left({\mathrm{\ω}}_{1}t\right)+[\underset{k=-\∞}{\overset{+\∞}{\mathrm{\Σ}}}{a}_{\mathrm{Qk}}{h}_1(t-k{T}_1)\left]\sin \left({\mathrm{\ω}}_{1}t\right)\right]\}$

A is the amplitude of qpsk modulation signal, and its value is for just; a _Ik, a _QkBe respectively the data message of I road in qpsk modulation signal, Q road transmission, value is ± 1; h ₁(t-kT ₁) be the pulse shock response of transmitted signal, its corresponding frequency response function is that rolloff-factor is α ₁The square root raised cosine function, α ₁Span between 0～1; T ₁A _IkAnd a _QkCode-element period, 1/T ₁It is the baud rate of QPSK signal; ω ₁=2 π f ₁Be the angular frequency of QPSK carrier signal, t is the time, and unit is second,

r ₂Formula as follows:

$r_2\left(t\right)=B\left\{\right[\underset{k=-\∞}{\overset{+\∞}{\mathrm{\Σ}}}{b}_{\mathrm{Ik}}\left(t\right)m_i\left(t\right)h_2(t-{\mathrm{kT}}_2)]\cos \left({\mathrm{\ω}}_{2}t\right)+[\underset{k=-\∞}{\overset{+\∞}{\mathrm{\Σ}}}{b}_{\mathrm{Qk}}\left(t\right)m_q\left(t\right)h_2(t-k{T}_2)\left]\sin \left({\mathrm{\ω}}_{2}t\right)\right\}$

B is the amplitude of modulated spread spectrum signal, and its value is always for just; b _Ik, b _QkBe respectively the data message of modulated spread spectrum signal I road, Q road transmission, value is ± 1; , m _i(t), m _q(t) be the frequency expansion sequence on modulated spread spectrum signal I road, Q road, value is ± 1, its nominal rate and r ₁(t) a _IkAnd a _QkIdentical; m _i(t), m _q(t) speed is far longer than b _Ik, b _QkSpeed, m _i(t), m _q(t) and b _Ik, b _QkThe ratio of speed is called spread spectrum coefficient k; h ₂(t-kT ₂) be the pulse shock response of transmitted signal, its corresponding frequency response function is α for rolloff-factor ₂The square root raised cosine function, α ₂Span between 0～1; T ₂M _i(t), m _q(t) code-element period, 1/T ₂Its baud rate, its nominal value and T ₁Identical; ω ₂=2 π f ₂The angular frequency of signal, its nominal value and ω ₁Identical.

Further, in said method, the formula of I roadbed band signal is as follows:

$x_i\left(t\right)=A^{\′}\underset{k=-\∞}{\overset{+\∞}{\mathrm{\Σ}}}{a}_{\mathrm{Ik}}{h}_1(t-{\mathrm{kT}}_1)$

$+B^{\′}\left\{\right[\underset{k=-\∞}{\overset{+\∞}{\mathrm{\Σ}}}{b}_{\mathrm{Ik}}\left(t\right)m_i\left(t\right)h_2(t-{\mathrm{kT}}_2)]\cos ({\mathrm{\ω}}_2-{\mathrm{\ω}}_{1}t)+[\underset{k=-\∞}{\overset{+\∞}{\mathrm{\Σ}}}{b}_{\mathrm{Qk}}\left(t\right)m_q\left(t\right)h_2(t-{\mathrm{kT}}_2)\left]\sin ({\mathrm{\ω}}_2-{\mathrm{\ω}}_{1}t)\right\}$

$+n_i\left(t\right)$

$=u_i\left(t\right)+v_i\left(t\right)+n_i\left(t\right)$

The formula of Q roadbed band signal is as follows:

$x_q\left(t\right)=A^{\′}\underset{k=-\∞}{\overset{+\∞}{\mathrm{\Σ}}}{a}_{\mathrm{Qk}}{h}_1(t-{\mathrm{kT}}_1)$

$+B^{\′}\left\{\right[\underset{k=-\∞}{\overset{+\∞}{\mathrm{\Σ}}}{b}_{\mathrm{Qk}}\left(t\right)m_q\left(t\right)h_2(t-{\mathrm{kT}}_2)]\cos ({\mathrm{\ω}}_2-{\mathrm{\ω}}_{1}t)+[\underset{k=-\∞}{\overset{+\∞}{\mathrm{\Σ}}}{b}_{\mathrm{Ik}}\left(t\right)m_i\left(t\right)h_2(t-{\mathrm{kT}}_2)\left]\sin ({\mathrm{\ω}}_2-{\mathrm{\ω}}_{1}t)\right\},$

$+n_q\left(t\right)$

$=u_q\left(t\right)+v_q\left(t\right)+n_q\left(t\right)$

Wherein, x _i(t) be I roadbed band signal, x _q(t) Q roadbed band signal, u _i(t), u _q(t) be respectively the base band component on QPSK signal I road, Q road, v _i(t), v _q(t) be respectively the base band component on spread-spectrum signal I road, Q road, n _i(t), n _q(t) be respectively the Gaussian noise on I road, Q road, the base band component of QPSK signal is far longer than the base band component of spread-spectrum signal, i.e. u _i(t)〉〉 v _i(t), u _q(t)〉〉 v _q(t), due to ω ₁, ω ₂Substantially equal, v _i(t), v _q(t) amplitude can slowly change, and A' is u _i(t), u _q(t) range weight, A' is directly proportional to A; B' is v _i(t), v _q(t) range weight, B' is directly proportional to B.

Further, in said method, the formula of I road, Q road QPSK regeneration baseband signal is:

$\left\{\begin{array}{c}{u^{\′}}_i\left(t\right)=A^{\′\′}\underset{k=-\∞}{\overset{+\∞}{\mathrm{\Σ}}}{a^{\′}}_{\mathrm{Ik}}{h}_1(t-{\mathrm{kT}}_1)\\ {u^{\′}}_q\left(t\right)=A^{\′\′}\underset{k=-\∞}{\overset{+\∞}{\mathrm{\Σ}}}{a^{\′}}_{\mathrm{Qk}}{h}_1(t-\mathrm{kT})\end{array}\right.$

Wherein, u' _i(t) be I road QPSK regeneration baseband signal, u ' _q(t) be Q road QPSK regeneration baseband signal, a' _IkBe I road QPSK demodulating data, a' _QkBe I road QPSK demodulating data, h ₁(t-kT ₁) be the pulse shock response of described the 3rd QPSK matched filter, the 4th QPSK matched filter, A " is u' _i(t), u ' _q(t) range weight.

Further, in said method, the formula of first, second, and third pair of QPSK base band reproducing signals is as follows:

$\left\{\begin{array}{cc}{u^{\′\′}}_{\mathrm{in}}\left(t\right)=p_n{u^{\′}}_i\left(t\right)& n=\mathrm{1,2,3}\\ {u^{\′\′}}_{\mathrm{qn}}\left(t\right)=p_n{u^{\′}}_q\left(t\right)& n=\mathrm{1,2,3}\end{array}\right.$

Wherein, u " _in(t) be respectively first, second, and third different amplitude I road QPSK base band reproducing signals, u " _qn(t) be the Q road QPSK base band reproducing signals of first, second, and third different amplitude, p ₁, p ₂, p ₃First, second, and third amplitude that is respectively is adjusted parameter, p ₁P ₂P ₃, p ₁-p ₂=p ₂-p ₃=Δ, the described control logic circuit signal to noise ratio after according to the spread-spectrum signal despreading is adjusted p ₁, p ₂, p ₃Numerical value so that second couple of QPSK base band reproducing signals u " _i2(t), u " _q2(t) approach the base band component u on QPSK signal I road, Q road most _i(t), u _q(t).

Further, in said method, the formula of described first, second, and third pair of spread baseband signal is as follows:

$\left\{\begin{array}{cc}{y}_{\mathrm{in}}\left(t\right)={x_i}^{\′}\left(t\right)-{u^{\′\′}}_{\mathrm{in}}\left(t\right)& \\ =u_i\left(t\right)+v_i\left(t\right)+n_i\left(t\right)-{u^{\′\′}}_{\mathrm{in}}\left(t\right)& n=\mathrm{1,2,3}\\ =v_i\left(t\right)+\mathrm{\Δ}{u}_{\mathrm{in}}\left(t\right)+n_i\left(t\right)& \\ & \\ y_{\mathrm{qn}}\left(t\right)={x_q}^{\′}\left(t\right)-{u^{\′\′}}_{\mathrm{qn}}\left(t\right)& \\ =u_q\left(t\right)+v_q\left(t\right)+n_q\left(t\right)-{u^{\′\′}}_{\mathrm{qn}}\left(t\right)& n=\mathrm{1,2,3}\\ =v_q\left(t\right)+\mathrm{\Δ}{u}_{\mathrm{qn}}\left(t\right)+n_q\left(t\right)& \end{array}\right.$

Wherein, y _in(t) be I road spread baseband signal, y _qn(t) be Q road spread baseband signal, Δ u _in(t)=u _i(t)-u " _in(t) be the remaining component of I road QPSK baseband signal component, Δ u _qn(t)=u _q(t)-u " _qn(t), be the remaining component of Q road QPSK baseband signal component.

Further, in said method, it is as follows that the formula of first, second, and third despread signal signal to noise ratio is calculated and exported to described signal to noise ratio module:

Wherein,

Be respectively first, second, and third despread signal signal to noise ratio, m _i(t) be I road frequency expansion sequence, m _q(t) be Q road frequency expansion sequence, spread spectrum coefficient is k, z _i1(t), z _q1(t), z _i2(t), z _q2(t) by I road spread baseband signal y _in(t), Q road spread baseband signal y _qn(t) respectively with described local frequency expansion sequence m _i(t) and m _q(t) carry out mould two and add computing generation, S _{Despreading n}Be despread signal energy, N _{Despreading n}Be the despread signal noise energy, when local I road, Q road frequency expansion sequence is synchronizeed with the input signal frequency expansion sequence, despread signal energy S _{Despreading n}Reach peak value.

Further, in said method, the control logic circuit of described receiver is adjusted described first, second, and third amplitude according to described first, second, and third despread signal signal to noise ratio and is adjusted in the step of parameter, when

The time, reduce p _nWhen

The time, increase p _nWhen

And

During for maximum, think u " _i2(t), u " _q2(t) adjust to the best, p _nNumerical value is constant.

According to another side of the present invention, a kind of receiver that improves satellite spectrum-spread communication despread signal signal to noise ratio is provided, described receiver comprises:

The input signal splitter, be used for obtaining input signal, and described input signal is divided into the equal described input signal of two-way, the described input signal in each road is QPSK modulation downstream signal, band spectrum modulation downstream signal and Gaussian noise sum, and wherein QPSK modulation downstream signal is far longer than the band spectrum modulation downstream signal;

Local oscillator, for generation of the required orthogonal local oscillation signal of demodulation, the carrier synchronization of local oscillator carrier wave and QPSK modulation downstream signal, local frequency equals the carrier frequency of QPSK modulation downstream signal, and the orthogonal local oscillation signal of local oscillator output multiplies each other with every road input signal respectively and exports I road difference frequency and frequency signal and Q road difference frequency and frequency signal;

The one QPSK Signal Matching filter, the 2nd QPSK Signal Matching filter, the I road, Q road and the frequency signal that are used for difference filtering described I road difference frequency and frequency signal and Q road difference frequency and frequency signal, export described I road, Q road difference frequency signal as I road, Q roadbed band signal, described I road, Q roadbed band signal are QPSK baseband signal, spread baseband signal and Gaussian noise sum, and wherein the amplitude of QPSK baseband signal is far longer than spread baseband signal;

Qpsk demodulator is used for exporting respectively I road, Q road QPSK demodulating data according to described I road, Q roadbed band signal;

The 3rd QPSK matched filter, the 4th QPSK matched filter are used for respectively the baseband signal of regenerating according to described I road, QPSK demodulating data output I road, Q road, Q road QPSK;

Amplitude adjusting circuit, be used for adjusting first, second, and third pair of QPSK base band reproducing signals of parameter output according to described I road Q road QPSK regeneration baseband signal with first, second, and third amplitude, and with second pair of QPSK base band reproducing signals as the optimal compensation QPSK base band reproducing signals, first pair of QPSK base band reproducing signals is as overcompensation QPSK base band reproducing signals, and the 3rd pair of QPSK base band reproducing signals is as undercompensation QPSK base band reproducing signals;

The signal delay module is used for respectively described I road, Q roadbed band signal are fixed time-delay, and I road, Q roadbed band signal and QPSK base band reproducing signals after time-delay are complementary in time;

The signal cancellation module, after being used for delaying time, I road, the rear Q roadbed band signal of time-delay subtract each other with described first, second, and third pair of QPSK base band reproducing signals respectively, export first, second, and third pair of spread baseband signal;

The signal to noise ratio module is used for described first, second, and third pair of spread baseband signal carried out respectively despreading, and calculates and export first, second, and third despread signal signal to noise ratio;

Control logic circuit, be used for adjusting described first, second, and third amplitude according to described first, second, and third despread signal signal to noise ratio and adjust parameter, and control the signal to noise ratio module and adjust first, second, and third corresponding despread signal signal to noise ratio, until being maximum and the first and second despread signal signal to noise ratios, the second despread signal signal to noise ratio equates.

Further, in above-mentioned receiver, described receiver also comprises a channel error correcting deocder, be used for and will encode to generate I road, Q road coded data again after the QPSK demodulating data error-correcting decoding of described I road, Q road again, described the 3rd QPSK matched filter, the 4th QPSK matched filter are used for according to described I road, Q road coded data output I road, the Q road QPSK baseband signal of regenerating again.

Further, in above-mentioned receiver, the formula of described input signal is as follows:

$r\left(t\right)=A\left\{\right[\underset{k=-\∞}{\overset{+\∞}{\mathrm{\Σ}}}{a}_{\mathrm{Ik}}{h}_1(t-{\mathrm{kT}}_1)]\cos \left({\mathrm{\ω}}_{1}t\right)+[\underset{k=-\∞}{\overset{+\∞}{\mathrm{\Σ}}}{a}_{\mathrm{Qk}}{h}_1(t-k{T}_1)\left]\sin \left({\mathrm{\ω}}_{1}t\right)\right]\}$

$+B\left\{\right[\underset{k=-\∞}{\overset{+\∞}{\mathrm{\Σ}}}{b}_{\mathrm{Ik}}\left(t\right)m_i\left(t\right)h_2(t-{\mathrm{kT}}_2)]\cos \left({\mathrm{\ω}}_{2}t\right)+[\underset{k=-\∞}{\overset{+\∞}{\mathrm{\Σ}}}{b}_{\mathrm{Qk}}\left(t\right)m_q\left(t\right)h_2(t-k{T}_2)\left]\sin \left({\mathrm{\ω}}_{2}t\right)\right\}$

$+n\left(t\right)$

$=r_1\left(t\right)+r_2\left(t\right)+n\left(t\right)$

Wherein, r (t) is input signal, r ₁Be QPSK modulation downstream signal, r ₂Be the band spectrum modulation downstream signal, n (t) is Gaussian noise;

r ₁Formula as follows:

$r_1\left(t\right)=A\left\{\right[\underset{k=-\∞}{\overset{+\∞}{\mathrm{\Σ}}}{a}_{\mathrm{Ik}}{h}_1(t-{\mathrm{kT}}_1)]\cos \left({\mathrm{\ω}}_{1}t\right)+[\underset{k=-\∞}{\overset{+\∞}{\mathrm{\Σ}}}{a}_{\mathrm{Qk}}{h}_1(t-k{T}_1)\left]\sin \left({\mathrm{\ω}}_{1}t\right)\right]\}$

A is the amplitude of qpsk modulation signal, and its value is for just; a _Ik, a _QkBe respectively the data message of I road in qpsk modulation signal, Q road transmission, value is ± 1; h ₁(t-kT ₁) be the pulse shock response of transmitted signal, its corresponding frequency response function is that rolloff-factor is α ₁The square root raised cosine function, α ₁Span between 0～1; T ₁A _IkAnd a _QkCode-element period, 1/T ₁It is the baud rate of QPSK signal; ω ₁=2 π f ₁Be the angular frequency of QPSK carrier signal, t is the time, and unit is second,

r ₂Formula as follows:

$r_2\left(t\right)=B\left\{\right[\underset{k=-\∞}{\overset{+\∞}{\mathrm{\Σ}}}{b}_{\mathrm{Ik}}\left(t\right)m_i\left(t\right)h_2(t-{\mathrm{kT}}_2)]\cos \left({\mathrm{\ω}}_{2}t\right)+[\underset{k=-\∞}{\overset{+\∞}{\mathrm{\Σ}}}{b}_{\mathrm{Qk}}\left(t\right)m_q\left(t\right)h_2(t-k{T}_2)\left]\sin \left({\mathrm{\ω}}_{2}t\right)\right\}$

B is the amplitude of modulated spread spectrum signal, and its value is always for just; b _Ik, b _QkBe respectively the data message of modulated spread spectrum signal I road, Q road transmission, value is ± 1; , m _i(t), m _q(t) be the frequency expansion sequence on modulated spread spectrum signal I road, Q road, value is ± 1, its nominal rate and r ₁(t) a _IkAnd a _QkIdentical; m _i(t), m _q(t) speed is far longer than b _Ik, b _QkSpeed, m _i(t), m _q(t) and b _Ik, b _QkThe ratio of speed is called spread spectrum coefficient k; h ₂(t-kT ₂) be the pulse shock response of transmitted signal, its corresponding frequency response function is α for rolloff-factor ₂The square root raised cosine function, α ₂Span between 0～1; T ₂M _i(t), m _q(t) code-element period, 1/T ₂Its baud rate, its nominal value and T ₁Identical; ω ₂=2 π f ₂The angular frequency of signal, its nominal value and ω ₁Identical.

Further, in above-mentioned receiver, the formula of described input signal is as follows:

$r\left(t\right)=A\left\{\right[\underset{k=-\∞}{\overset{+\∞}{\mathrm{\Σ}}}{a}_{\mathrm{Ik}}{h}_1(t-{\mathrm{kT}}_1)]\cos \left({\mathrm{\ω}}_{1}t\right)+[\underset{k=-\∞}{\overset{+\∞}{\mathrm{\Σ}}}{a}_{\mathrm{Qk}}{h}_1(t-k{T}_1)\left]\sin \left({\mathrm{\ω}}_{1}t\right)\right]\}$

$+B\left\{\right[\underset{k=-\∞}{\overset{+\∞}{\mathrm{\Σ}}}{b}_{\mathrm{Ik}}\left(t\right)m_i\left(t\right)h_2(t-{\mathrm{kT}}_2)]\cos \left({\mathrm{\ω}}_{2}t\right)+[\underset{k=-\∞}{\overset{+\∞}{\mathrm{\Σ}}}{b}_{\mathrm{Qk}}\left(t\right)m_q\left(t\right)h_2(t-k{T}_2)\left]\sin \left({\mathrm{\ω}}_{2}t\right)\right\}$

$+n\left(t\right)$

$=r_1\left(t\right)+r_2\left(t\right)+n\left(t\right)$

Wherein, r (t) is input signal, r ₁Be QPSK modulation downstream signal, r ₂Be the band spectrum modulation downstream signal, n (t) is Gaussian noise;

r ₁Formula as follows:

$r_1\left(t\right)=A\left\{\right[\underset{k=-\∞}{\overset{+\∞}{\mathrm{\Σ}}}{a}_{\mathrm{Ik}}{h}_1(t-{\mathrm{kT}}_1)]\cos \left({\mathrm{\ω}}_{1}t\right)+[\underset{k=-\∞}{\overset{+\∞}{\mathrm{\Σ}}}{a}_{\mathrm{Qk}}{h}_1(t-k{T}_1)\left]\sin \left({\mathrm{\ω}}_{1}t\right)\right]\}$

A is the amplitude of qpsk modulation signal, and its value is for just; a _Ik, a _QkBe respectively the data message of I road in qpsk modulation signal, Q road transmission, value is ± 1; h ₁(t-kT ₁) be the pulse shock response of transmitted signal, its corresponding frequency response function is that rolloff-factor is α ₁The square root raised cosine function, α ₁Span between 0～1; T ₁A _IkAnd a _QkCode-element period, 1/T ₁It is the baud rate of QPSK signal; ω ₁=2 π f ₁Be the angular frequency of QPSK carrier signal, t is the time, and unit is second,

r ₂Formula as follows:

$r_2\left(t\right)=B\left\{\right[\underset{k=-\∞}{\overset{+\∞}{\mathrm{\Σ}}}{b}_{\mathrm{Ik}}\left(t\right)m_i\left(t\right)h_2(t-{\mathrm{kT}}_2)]\cos \left({\mathrm{\ω}}_{2}t\right)+[\underset{k=-\∞}{\overset{+\∞}{\mathrm{\Σ}}}{b}_{\mathrm{Qk}}\left(t\right)m_q\left(t\right)h_2(t-k{T}_2)\left]\sin \left({\mathrm{\ω}}_{2}t\right)\right\}$

B is the amplitude of modulated spread spectrum signal, and its value is always for just; b _Ik, b _QkBe respectively the data message of modulated spread spectrum signal I road, Q road transmission, value is ± 1; , m _i(t), m _q(t) be the frequency expansion sequence on modulated spread spectrum signal I road, Q road, value is ± 1, its nominal rate and r ₁(t) a _IkAnd a _QkIdentical; m _i(t), m _q(t) speed is far longer than b _Ik, b _QkSpeed, m _i(t), m _q(t) and b _Ik, b _QkThe ratio of speed is called spread spectrum coefficient k; h ₂(t-kT ₂) be the pulse shock response of transmitted signal, its corresponding frequency response function is α for rolloff-factor ₂The square root raised cosine function, α ₂Span between 0～1; T ₂M _i(t), m _q(t) code-element period, 1/T ₂Its baud rate, its nominal value and T ₁Identical; ω ₂=2 π f ₂The angular frequency of signal, its nominal value and ω ₁Identical.

Further, in above-mentioned receiver, the formula of I road, Q road QPSK regeneration baseband signal is:

$\left\{\begin{array}{c}{u^{\′}}_i\left(t\right)=A^{\′\′}\underset{k=-\∞}{\overset{+\∞}{\mathrm{\Σ}}}{a^{\′}}_{\mathrm{Ik}}{h}_1(t-{\mathrm{kT}}_1)\\ {u^{\′}}_q\left(t\right)=A^{\′\′}\underset{k=-\∞}{\overset{+\∞}{\mathrm{\Σ}}}{a^{\′}}_{\mathrm{Qk}}{h}_1(t-\mathrm{kT})\end{array}\right.$

Wherein, u' _i(t) be I road QPSK regeneration baseband signal, u ' _q(t) be Q road QPSK regeneration baseband signal, a' _IkBe I road QPSK demodulating data, a' _QkBe I road QPSK demodulating data, h ₁(t-kT ₁) be the pulse shock response of described the 3rd QPSK matched filter, the 4th QPSK matched filter, A " is u' _i(t), u ' _q(t) range weight.

Further, in above-mentioned receiver, the formula of first, second, and third pair of QPSK base band reproducing signals is as follows:

$\left\{\begin{array}{cc}{u^{\′\′}}_{\mathrm{in}}\left(t\right)=p_n{u^{\′}}_i\left(t\right)& n=\mathrm{1,2,3}\\ {u^{\′\′}}_{\mathrm{qn}}\left(t\right)=p_n{u^{\′}}_q\left(t\right)& n=\mathrm{1,2,3}\end{array}\right.$

Wherein, u " _in(t) be respectively first, second, and third different amplitude I road QPSK base band reproducing signals, u " _qn(t) be the Q road QPSK base band reproducing signals of first, second, and third different amplitude, p ₁, p ₂, p ₃First, second, and third amplitude that is respectively is adjusted parameter, p ₁P ₂P ₃, p ₁-p ₂=p ₂-p ₃=Δ, the described control logic circuit signal to noise ratio after according to the spread-spectrum signal despreading is adjusted p ₁, p ₂, p ₃Numerical value so that second couple of QPSK base band reproducing signals u " _i2(t), u " _q2(t) approach the base band component u on QPSK signal I road, Q road most _i(t), u _q(t).

Further, in above-mentioned receiver, the formula of described first, second, and third pair of spread baseband signal is as follows:

$\left\{\begin{array}{cc}{y}_{\mathrm{in}}\left(t\right)={x_i}^{\′}\left(t\right)-{u^{\′\′}}_{\mathrm{in}}\left(t\right)& \\ =u_i\left(t\right)+v_i\left(t\right)+n_i\left(t\right)-{u^{\′\′}}_{\mathrm{in}}\left(t\right)& n=\mathrm{1,2,3}\\ =v_i\left(t\right)+\mathrm{\Δ}{u}_{\mathrm{in}}\left(t\right)+n_i\left(t\right)& \\ & \\ y_{\mathrm{qn}}\left(t\right)={x_q}^{\′}\left(t\right)-{u^{\′\′}}_{\mathrm{qn}}\left(t\right)& \\ =u_q\left(t\right)+v_q\left(t\right)+n_q\left(t\right)-{u^{\′\′}}_{\mathrm{qn}}\left(t\right)& n=\mathrm{1,2,3}\\ =v_q\left(t\right)+\mathrm{\Δ}{u}_{\mathrm{qn}}\left(t\right)+n_q\left(t\right)& \end{array}\right.$

Wherein, y _in(t) be I road spread baseband signal, y _qn(t) be Q road spread baseband signal, Δ u _in(t)=u _i(t)-u " _in(t) be the remaining component of I road QPSK baseband signal component, Δ u _qn(t)=u _q(t)-u " _qn(t), be the remaining component of Q road QPSK baseband signal component.

Further, in above-mentioned receiver, it is as follows that the formula of first, second, and third despread signal signal to noise ratio is calculated and exported to described signal to noise ratio module:

Wherein,

Be respectively first, second, and third despread signal signal to noise ratio, m _i(t) be I road frequency expansion sequence, m _q(t) be Q road frequency expansion sequence, spread spectrum coefficient is k, z _i1(t), z _q1(t), z _i2(t), z _q2(t) by I road spread baseband signal y _in(t), Q road spread baseband signal y _qn(t) respectively with described local frequency expansion sequence m _i(t) and m _q(t) carry out mould two and add computing generation, S _{Despreading n}Be despread signal energy, N _{Despreading n}Be the despread signal noise energy, when local I road, Q road frequency expansion sequence is synchronizeed with the input signal frequency expansion sequence, despread signal energy S _{Despreading n}Reach peak value.

Further, in above-mentioned receiver, the control logic circuit of described receiver is adjusted described first, second, and third amplitude according to described first, second, and third despread signal signal to noise ratio and is adjusted in the step of parameter, when

The time, reduce p _nWhen

The time, increase p _nWhen

And

During for maximum, think u " _i2(t), u " _q2(t) adjust to the best, p _nNumerical value is constant.

Cover under condition in the QPSK large-signal that takies same frequency, same frequency band, compare with existing routine techniques, adopt the present invention can improve satellite band spread receiver despread signal signal to noise ratio, improve communication spread spectrum quality; Require to reduce the transmitting power of spread spectrum transmitter under constant condition at the spread-spectrum signal spreading gain, reduce spread-spectrum signal to the impact of QPSK signal, improve the disguise of spread-spectrum signal; Require to reduce the spread spectrum coefficient of spread-spectrum signal under constant condition in signal to noise ratio after the spread-spectrum signal despreading, improve the transmission rate of spread spectrum communication system.

Description of drawings

Fig. 1 covers under condition in the QPSK large-signal that takies same frequency, same frequency band, spread spectrum satellite communication system schematic diagram;

Fig. 2 is qpsk modulation signal S ₁, modulated spread spectrum signal S ₂Spectrum diagram;

Fig. 3 is the method flow diagram that improves satellite spectrum-spread communication receiver despread signal signal to noise ratio of the embodiment of the present invention;

Fig. 4 is the operation of receiver schematic diagram of the embodiment of the present invention;

Fig. 5 be the embodiment of the present invention to coding again after coded message decoding, thereby improve the schematic diagram of QPSK regeneration baseband signal distortion;

Fig. 6 is the despread signal snr computation schematic diagram of the embodiment of the present invention;

Fig. 7 is that the QPSK base band component of the embodiment of the present invention is offset flow chart;

Fig. 8 adopts signal to noise ratio schematic diagram after the spread-spectrum signal despreading of existing usual manner;

Fig. 9 is signal to noise ratio schematic diagram after the spread-spectrum signal despreading of the embodiment of the present invention.

Embodiment

For above-mentioned purpose of the present invention, feature and advantage can be become apparent more, the present invention is further detailed explanation below in conjunction with the drawings and specific embodiments.

Embodiment one

For the satellite spectrum-spread communication system under same frequency, same band QPSK large-signal are covered as shown in Figure 1, the present embodiment provides a kind of method of improving satellite spectrum-spread communication receiver despread signal signal to noise ratio as shown in Fig. 3 and 4, the basic principle of the present embodiment method is to produce QPSK base band reproducing signals by the QPSK demodulating data, then with the QPSK baseband signal component in QPSK base band reproducing signals counteracting baseband signal, thereby improve the Signal-to-Noise after the spread-spectrum signal despreading, the method comprises:

Step S1, input signal splitter 1 obtains input signal, and described input signal is divided into the equal described input signal of two-way, the described input signal in each road is QPSK modulation downstream signal, band spectrum modulation downstream signal and Gaussian noise sum, and wherein QPSK modulation downstream signal is far longer than the band spectrum modulation downstream signal.

Concrete, described input signal is suc as formula 5:

$r\left(t\right)=A\left\{\right[\underset{k=-\∞}{\overset{+\∞}{\mathrm{\Σ}}}{a}_{\mathrm{Ik}}{h}_1(t-{\mathrm{kT}}_1)]\cos \left({\mathrm{\ω}}_{1}t\right)+[\underset{k=-\∞}{\overset{+\∞}{\mathrm{\Σ}}}{a}_{\mathrm{Qk}}{h}_1(t-k{T}_1)\left]\sin \left({\mathrm{\ω}}_{1}t\right)\right]\}$

$+B\left\{\right[\underset{k=-\∞}{\overset{+\∞}{\mathrm{\Σ}}}{b}_{\mathrm{Ik}}\left(t\right)m_i\left(t\right)h_2(t-{\mathrm{kT}}_2)]\cos \left({\mathrm{\ω}}_{2}t\right)+[\underset{k=-\∞}{\overset{+\∞}{\mathrm{\Σ}}}{b}_{\mathrm{Qk}}\left(t\right)m_q\left(t\right)h_2(t-k{T}_2)\left]\sin \left({\mathrm{\ω}}_{2}t\right)\right\}$

$+n\left(t\right)$

$=r_1\left(t\right)+r_2\left(t\right)+n\left(t\right)$

(formula 5)

Wherein, r (t) is input signal, r ₁Be QPSK modulation downstream signal, r ₂Be the band spectrum modulation downstream signal, n (t) is Gaussian noise, condition described according to background technology, modulated spread spectrum signal r ₂(t) amplitude is far smaller than qpsk modulation signal r ₁(t) amplitude (usually less than 1/20), modulated spread spectrum signal r ₂(t) can not affect qpsk modulation signal r ₁(t) normal demodulation.

r ₁Suc as formula 1:

$r_1\left(t\right)=A\left\{\right[\underset{k=-\∞}{\overset{+\∞}{\mathrm{\Σ}}}{a}_{\mathrm{Ik}}{h}_1(t-{\mathrm{kT}}_1)]\cos \left({\mathrm{\ω}}_{1}t\right)+[\underset{k=-\∞}{\overset{+\∞}{\mathrm{\Σ}}}{a}_{\mathrm{Qk}}{h}_1(t-k{T}_1)\left]\sin \left({\mathrm{\ω}}_{1}t\right)\right]\}$ (formula 1)

Wherein, A is the amplitude of qpsk modulation signal, and its value is for just; a _Ik, a _QkBe respectively the data message of I road in qpsk modulation signal, Q road transmission, value is ± 1; h ₁(t-kT ₁) be the pulse shock response of transmitted signal, its corresponding frequency response function is that rolloff-factor is α ₁The square root raised cosine function, α ₁Span between 0～1; T ₁A _IkAnd a _QkCode-element period, 1/T ₁It is the baud rate of QPSK signal; ω ₁=2 π f ₁Be the angular frequency of QPSK carrier signal, t is the time, and unit is second.

r ₂Suc as formula 2:

$r_2\left(t\right)=B\left\{\right[\underset{k=-\∞}{\overset{+\∞}{\mathrm{\Σ}}}{b}_{\mathrm{Ik}}\left(t\right)m_i\left(t\right)h_2(t-{\mathrm{kT}}_2)]\cos \left({\mathrm{\ω}}_{2}t\right)+[\underset{k=-\∞}{\overset{+\∞}{\mathrm{\Σ}}}{b}_{\mathrm{Qk}}\left(t\right)m_q\left(t\right)h_2(t-k{T}_2)\left]\sin \left({\mathrm{\ω}}_{2}t\right)\right\}$

(formula 2)

Wherein, B is the amplitude of modulated spread spectrum signal, and its value is always for just; b _Ik, b _QkBe respectively the data message of modulated spread spectrum signal I road, Q road transmission, value is ± 1; , m _i(t), m _q(t) be the frequency expansion sequence on modulated spread spectrum signal I road, Q road, value is ± 1, its nominal rate and r ₁(t) a _IkAnd a _QkIdentical; m _i(t), m _q(t) speed is far longer than b _Ik, b _QkSpeed, m _i(t), m _q(t) and b _Ik, b _QkThe ratio of speed is called spread spectrum coefficient k; h ₂(t-kT ₂) be the pulse shock response of transmitted signal, its corresponding frequency response function is α for rolloff-factor ₂The square root raised cosine function, α ₂Span between 0～1; T ₂M _i(t), m _q(t) code-element period, 1/T ₂Its baud rate, its nominal value and T ₁Identical; ω ₂=2 π f ₂The angular frequency of signal, its nominal value and ω ₁Identical.

Step S2, the local oscillator carrier wave that one local oscillator 2 of receiver produces and the carrier synchronization of QPSK modulation downstream signal, local frequency equals the carrier frequency of QPSK modulation downstream signal, and the orthogonal local oscillation signal of local oscillator output multiplies each other with every road input signal respectively and exports I road difference frequency and frequency signal and Q road difference frequency and frequency signal.Concrete, after the normal demodulation of qpsk modulation signal, receiver local oscillator carrier wave is synchronizeed with the QPSK signal carrier under its carrier synchronization circuit is controlled, receiver local frequency ω ₀Equal to input qpsk modulation signal carrier frequency ω ₁

Step S3, the one QPSK Signal Matching filter 3 of described receiver, the 2nd QPSK Signal Matching filter 4 be filtering described I road difference frequencies and signal and Q road difference frequency and the I road in signal, Q road and signal frequently frequently frequently respectively, exports described I road, Q road difference frequency signal as I road, Q roadbed band signal x _i(t), x _q(t), described I road, Q roadbed band signal are QPSK baseband signal, spread baseband signal and Gaussian noise sum, and wherein the amplitude of QPSK baseband signal is far longer than spread baseband signal.

Concrete, I roadbed band signal is suc as formula 6:

$x_i\left(t\right)=A^{\′}\underset{k=-\∞}{\overset{+\∞}{\mathrm{\Σ}}}{a}_{\mathrm{Ik}}{h}_1(t-{\mathrm{kT}}_1)$

$+B^{\′}\left\{\right[\underset{k=-\∞}{\overset{+\∞}{\mathrm{\Σ}}}{b}_{\mathrm{Ik}}\left(t\right)m_i\left(t\right)h_2(t-{\mathrm{kT}}_2)]\cos ({\mathrm{\ω}}_2-{\mathrm{\ω}}_{1}t)+[\underset{k=-\∞}{\overset{+\∞}{\mathrm{\Σ}}}{b}_{\mathrm{Qk}}\left(t\right)m_q\left(t\right)h_2(t-{\mathrm{kT}}_2)\left]\sin ({\mathrm{\ω}}_2-{\mathrm{\ω}}_{1}t)\right\}$

$+n_i\left(t\right)$

$=u_i\left(t\right)+v_i\left(t\right)+n_i\left(t\right)$

(formula 6)

Q roadbed band signal is suc as formula 7:

$x_q\left(t\right)=A^{\′}\underset{k=-\∞}{\overset{+\∞}{\mathrm{\Σ}}}{a}_{\mathrm{Qk}}{h}_1(t-{\mathrm{kT}}_1)$

$+B^{\′}\left\{\right[\underset{k=-\∞}{\overset{+\∞}{\mathrm{\Σ}}}{b}_{\mathrm{Qk}}\left(t\right)m_q\left(t\right)h_2(t-{\mathrm{kT}}_2)]\cos ({\mathrm{\ω}}_2-{\mathrm{\ω}}_{1}t)+[\underset{k=-\∞}{\overset{+\∞}{\mathrm{\Σ}}}{b}_{\mathrm{Ik}}\left(t\right)m_i\left(t\right)h_2(t-{\mathrm{kT}}_2)\left]\sin ({\mathrm{\ω}}_2-{\mathrm{\ω}}_{1}t)\right\},$

$+n_q\left(t\right)$

$=u_q\left(t\right)+v_q\left(t\right)+n_q\left(t\right)$

(formula 7)

Wherein, x _i(t) be I roadbed band signal, x _q(t) Q roadbed band signal, u _i(t), u _q(t) be respectively the base band component on QPSK signal I road, Q road, v _i(t), v _q(t) be respectively the base band component on spread-spectrum signal I road, Q road, n _i(t), n _q(t) be respectively the Gaussian noise on I road, Q road, the base band component of QPSK signal is far longer than the base band component of spread-spectrum signal, i.e. u _i(t)〉〉 v _i(t), u _q(t)〉〉 v _q(t), due to ω ₁, ω ₂Substantially equal, v _i(t), v _q(t) amplitude can slowly change, and A' is u _i(t), u _q(t) range weight, A' is directly proportional to A; B' is v _i(t), v _q(t) range weight, B' is directly proportional to B.

Step S4, a qpsk demodulator 5 of described receiver is exported respectively I road, Q road QPSK demodulating data a' according to described I road, Q roadbed band signal _Ik,, a' _Qk

Concrete, export I road QPSK demodulating data a' after the demodulation of QPSK signal _IkWith Q road QPSK demodulating data a' _Qk, value is ± 1; Except a small amount of error code, most a' _IkAnd a' _QkThe data message a that transmits with the QPSK signal _IkAnd a _QkIdentical.

Step S5, one the 3rd QPSK matched filter 6 of described receiver, the 4th QPSK matched filter 7 are respectively according to described I road, QPSK demodulating data output I road, Q road, Q road QPSK regeneration baseband signal u' _i(t), u' _q(t).

Concrete, QPSK demodulating data a' _IkAnd a' _QkThe input pulse impulse response is h respectively ₁(t-kT) the 3rd QPSK matched filter, the 4th QPSK matched filter produce I road, Q road QPSK regeneration baseband signal u' as 8 formulas _i(t) and u' _q(t).

$\left\{\begin{array}{c}{u^{\′}}_i\left(t\right)=A^{\′\′}\underset{k=-\∞}{\overset{+\∞}{\mathrm{\Σ}}}{a^{\′}}_{\mathrm{Ik}}{h}_1(t-{\mathrm{kT}}_1)\\ {u^{\′}}_q\left(t\right)=A^{\′\′}\underset{k=-\∞}{\overset{+\∞}{\mathrm{\Σ}}}{a^{\′}}_{\mathrm{Qk}}{h}_1(t-\mathrm{kT})\end{array}\right.$ (formula 8)

Wherein, u' _i(t) be I road QPSK regeneration baseband signal, u ' _q(t) be Q road QPSK regeneration baseband signal, a' _IkBe I road QPSK demodulating data, a' _QkBe I road QPSK demodulating data, h ₁(t-kT ₁) be the pulse shock response of described the 3rd QPSK matched filter, the 4th QPSK matched filter, A " is u' _i(t), u ' _q(t) range weight.

If QPSK signal data information is processed through error correction coding, step S5 comprises:

One channel error correcting deocder 13 of described receiver encodes to generate I road, Q road coded data again after with described I road, Q road QPSK demodulating data error-correcting decoding again, and described the 3rd QPSK matched filter, the 4th QPSK matched filter are according to described I road, Q road coded data output I road, the Q road QPSK baseband signal of regenerating again.

Concrete, in order to reduce QPSK demodulating data a' _Ik, a' _QkError code causes regeneration baseband signal u' _i(t), u' _q(t) if distortion is QPSK signal data information a _Ik, a _QkProcess through error correction coding, can be with demodulating data a' _Ik, a' _QkEncode again after error-correcting decoding, produce coded data a again " _Ik, a " _Qk, then incite somebody to action coded data a again " _IkAnd a " _QkThe input pulse impulse response is h respectively ₁(t-kT ₁) matched filter, produce the QPSK demodulating data regeneration baseband signal u' suc as formula 9 _i(t) and u' _q(t) (see figure 5).Due to a' _Ik, a' _QkCompare a " _Ik, a " _QkHas the lower error rate (usually will hang down 3 above orders of magnitude), by a " _Ik, a " _QkThe u' that produces _i(t), u' _q(t) has less distortion.

$\left\{\begin{array}{c}{u^{\′}}_i\left(t\right)=A^{\′\′}\underset{k=-\∞}{\overset{+\∞}{\mathrm{\Σ}}}{a^{\′}}_{\mathrm{Ik}}{h}_1(t-\mathrm{kT})\\ {u^{\′}}_q\left(t\right)=A^{\′\′}\underset{k=-\∞}{\overset{+\∞}{\mathrm{\Σ}}}{a^{\′}}_{\mathrm{qk}}{h}_1(t-\mathrm{kT})\end{array}\right.$ (formula 9)

Step S6, one amplitude adjusting circuit 8 of described receiver is adjusted first, second, and third pair of QPSK base band reproducing signals of parameter output according to described I road, Q road QPSK regeneration baseband signal and first, second, and third amplitude, and with second pair of QPSK base band reproducing signals as the optimal compensation QPSK base band reproducing signals, first pair of QPSK base band reproducing signals is as overcompensation QPSK base band reproducing signals, and the 3rd pair of QPSK base band reproducing signals is as undercompensation QPSK base band reproducing signals.

Concrete, QPSK regeneration baseband signal u' _i(t) and u' _q(t) through amplitude adjusting circuit, form copying of three pairs of QPSK baseband signals, first, second, and third pair of QPSK base band reproducing signals is suc as formula 10.

$\left\{\begin{array}{cc}{u^{\′\′}}_{\mathrm{in}}\left(t\right)=p_n{u^{\′}}_i\left(t\right)& n=\mathrm{1,2,3}\\ {u^{\′\′}}_{\mathrm{qn}}\left(t\right)=p_n{u^{\′}}_q\left(t\right)& n=\mathrm{1,2,3}\end{array}\right.$ (formula 10)

Wherein, wherein, u " _in(t) be respectively first, second, and third different amplitude I road QPSK base band reproducing signals, u " _qn(t) be the Q road QPSK base band reproducing signals of first, second, and third different amplitude, p ₁, p ₂, p ₃First, second, and third amplitude that is respectively is adjusted parameter, p ₁P ₂P ₃, p ₁-p ₂=p ₂-p ₃=Δ, the described control logic circuit signal to noise ratio after according to the spread-spectrum signal despreading is adjusted p ₁, p ₂, p ₃Numerical value so that second couple of QPSK base band reproducing signals u " _i2(t), u " _q2(t) approach the base band component u on QPSK signal I road, Q road most _i(t), u _q(t), when the second the tunnel was in the optimal compensation, the despreading signal to noise ratio reached maximum; First pair of this moment be for overcompensation, its despreading signal to noise ratio little with second pair; Third Road is undercompensation, and its despreading signal to noise ratio is also less than second pair; First, second, and third pair of despread signal signal to noise ratio forms a peak, whether reaches the optimal compensation in order to differentiate.

Step S7, a signal delay module 9 of described receiver is fixed time-delay to described I road, Q roadbed band signal respectively, and I road, Q roadbed band signal and QPSK base band reproducing signals after time-delay are complementary in time.

Concrete, in order to compensate u " _i1(t)～u " _i3(t), u " _q1(t)～u " _q3(t) form required time delay, I road, Q roadbed band signal x _i(t), x _q(t) must be through corresponding constant time lag, after time-delay, signal is with x' _i(t), x' _q(t) expression.

Step S8, after a signal cancellation module 10 of described receiver will be delayed time respectively, I road, the rear Q roadbed band signal of time-delay subtract each other with described first, second, and third pair of QPSK base band reproducing signals respectively, export first, second, and third pair of spread baseband signal.

Concrete, x' _i(t) respectively with u " _i1(t), u " _i2(t), u " _i3(t) subtract each other x' _i(t) u in _i(t) composition is cancelled, and produces three I road band spectrum modulation baseband signal y _i1(t), y _i2(t), y _i3(t); x' _q(t) respectively with u " _q1(t), u " _q2(t), u " _q3(t) subtract each other x' _q(t) u in _q(t) composition is cancelled, and produces three Q road band spectrum modulation baseband signal y _q1(t), y _q2(t), y _q3(t).Described first, second, and third pair of spread baseband signal is suc as formula 11.

$\left\{\begin{array}{cc}{y}_{\mathrm{in}}\left(t\right)={x_i}^{\′}\left(t\right)-{u^{\′\′}}_{\mathrm{in}}\left(t\right)& \\ =u_i\left(t\right)+v_i\left(t\right)+n_i\left(t\right)-{u^{\′\′}}_{\mathrm{in}}\left(t\right)& n=\mathrm{1,2,3}\\ =v_i\left(t\right)+\mathrm{\Δ}{u}_{\mathrm{in}}\left(t\right)+n_i\left(t\right)& \\ & \\ y_{\mathrm{qn}}\left(t\right)={x_q}^{\′}\left(t\right)-{u^{\′\′}}_{\mathrm{qn}}\left(t\right)& \\ =u_q\left(t\right)+v_q\left(t\right)+n_q\left(t\right)-{u^{\′\′}}_{\mathrm{qn}}\left(t\right)& n=\mathrm{1,2,3}\\ =v_q\left(t\right)+\mathrm{\Δ}{u}_{\mathrm{qn}}\left(t\right)+n_q\left(t\right)& \end{array}\right.$ (formula 11)

Wherein, y _in(t) be I road spread baseband signal, y _qn(t) be Q road spread baseband signal, Δ u _in(t)=u _i(t)-u " _in(t) be the remaining component of I road QPSK baseband signal component, Δ u _qn(t)=u _q(t)-u " _qn(t), be the remaining component of Q road QPSK baseband signal component.

Step S9,11 pairs of described first, second, and third pair of spread baseband signal of a signal to noise ratio module of described receiver are carried out respectively despreading, and calculate and export first, second, and third despread signal signal to noise ratio.

Concrete, the signal to noise ratio after first, second, and third pair of quadrature spread baseband signal carried out respectively despreading and calculated despreading, if spread spectrum coefficient is k, the signal to noise ratio after the spread-spectrum signal despreading is represented by formula 12:

(formula 12)

As QPSK base band reproducing signals u " _in(t) and u " _qnWhen (t) complete and QPSK baseband signal is mated, Δ u _fin(t), Δ u _qn(t) become and zero, the signal to noise ratio after the spread-spectrum signal despreading is by formula 13 expressions:

(formula 13)

Wherein, [kv (t)] ²=[kv _i(t)] ²+ [kv _q(t)] ²The signal energy after despreading, [n (t)] ²=[n _i(t)] ²+ [n _q(t)] ²It is the noise energy after despreading.Compare with the signal to noise ratio suc as formula 4 usual manner band spread receiver despread signal, the despread signal signal to noise ratio that the present embodiment obtains improves significantly.

Concrete, described first, second, and third despread signal signal to noise ratio by suc as formula 14, formula 15, formula 16 calculate.

(formula 14)

(formula 15)

(formula 16)

Wherein, Be first, second, and third despread signal signal to noise ratio, y _in(t), y _qn(t) be the band spectrum modulation baseband signal, m _i(t) be I road frequency expansion sequence, m _q(t) be Q road frequency expansion sequence, k is spread spectrum coefficient; As shown in Figure 6, z _i1(t), z _q1(t), z _i2(t), z _q2(t) by I road spread baseband signal y _in(t) and Q road spread baseband signal y _qn(t) respectively with the local frequency expansion sequence m on modulated spread spectrum signal I road, Q road _i(t) and m _q(t) carry out mould two and add the computing generation; S _{Despreading n}Be despread signal energy, N _{Despreading n}Be the despread signal noise energy; When local I road, Q road frequency expansion sequence is synchronizeed with the input signal frequency expansion sequence, despread signal energy S _DespreadingReach peak value; N with formula 16 estimations _DespreadingIn comprised Δ u _i(t), Δ u _q(t), v _i(t), v _q(t), n _i(t), n _q(t) component is due to common v _i(t), v _q(t) component is much smaller than n _i(t), n _q(t) component, v _i(t), v _q(t) impact can be ignored.

Step S10, one control logic circuit 12 of described receiver is adjusted described first, second, and third amplitude according to described first, second, and third despread signal signal to noise ratio and is adjusted parameter, and control the signal to noise ratio module and adjust first, second, and third corresponding despread signal signal to noise ratio, until being maximum and the first and second despread signal signal to noise ratios, the second despread signal signal to noise ratio equates.

Concrete, baseband signal x' after time-delay _i(t), x' _q(t) with QPSK base band reproducing signals u " _in(t), u " _qn(t) (n=1,2,3) subtracts each other x' _i(t), x' _q(t) the QPSK base band component in reduces, and produces first, second, and third couple of spread baseband signal y _in(t), y _qn(t) (n=1,2,3).Calculate spread baseband signal y according to formula 14, formula 15, formula 16 _in(t), y _qn(t) signal to noise ratio (S/N) after (n=1,2,3) despreading _{Despreading n}(n=1,2,3).According to (S/N) _{Despreading n}The change amplitude is adjusted parameter p _nThe numerical value of (n=1,2,3) (flow process is as shown in Figure 7): when

The time, reduce p _nWhen

The time, increase p _nWhen And

During for maximum, think u " _i2(t), u " _q2(t) adjust to the best, p _nNumerical value is constant.By continuous adjustment p _n, finally make x' _i(t), x' _q(t) the QPSK base band component in is cancelled, thereby obtains maximum despread signal signal to noise ratio (S/N) _{Despreading 2}When the second the tunnel was in the optimal compensation, the despreading signal to noise ratio reached maximum; Be overcompensation this moment the 1 tunnel, and its despreading signal to noise ratio is little of the second the tunnel; The 3 the tunnel is undercompensation, and its despreading signal to noise ratio is also less than the second the tunnel; First, second, and third despread signal signal to noise ratio forms a peak, whether reaches the optimal compensation in order to differentiate.

Fig. 8 and shown in Figure 9 be qpsk modulation signal Amplitude Ratio modulated spread spectrum signal amplitude high 20 times (the high 26dB of power), spread spectrum coefficient is 127, snr of received signal is under the 20dB condition, the simulation result of the signal to noise ratio after the spread-spectrum signal despreading; Wherein Fig. 8 adopts signal to noise ratio after the spread-spectrum signal despreading of usual manner, and Fig. 9 adopts signal to noise ratio after spread-spectrum signal despreading of the present invention; In Fig. 8 and Fig. 9, transverse axis is the time, the longitudinal axis is power (unit is dB), and the white line in figure in the first half is power after the spread-spectrum signal despreading, and the white surface area in figure in the latter half is noise, as seen adopt the method for the present embodiment, the spread-spectrum signal signal to noise ratio has the above improvement of 10dB.

Adopt the method for the present embodiment in satellite communication system shown in Figure 1, with the same transmission conditions of usual manner under, can improve the signal to noise ratio after the spread-spectrum signal despreading, improve the transmission quality of spread spectrum communication; Require to reduce the transmitting power of spread spectrum transmitter under constant condition at the spread-spectrum signal spreading gain, reduce spread-spectrum signal to the impact of QPSK signal, improve the disguise of spread-spectrum signal; Require to reduce the spread spectrum coefficient of spread-spectrum signal under constant condition in signal to noise ratio after the spread-spectrum signal despreading, improve the transmission rate of spread spectrum communication system.

Embodiment two

As shown in Figure 4, the receiver that the present invention also provides another kind to improve satellite spectrum-spread communication despread signal signal to noise ratio, described receiver comprise input signal splitter 1, local oscillator 2, a QPSK Signal Matching filter 3, the 2nd QPSK Signal Matching filter 4, qpsk demodulator 5, the 3rd QPSK matched filter 6, the 4th QPSK matched filter 7, amplitude adjusting circuit 8, signal delay module 9, signal cancellation module 10, signal to noise ratio module 11 and control logic circuit 12.

Input signal splitter 1 is used for obtaining input signal, and described input signal is divided into the equal described input signal of two-way, the described input signal in each road is QPSK modulation downstream signal, band spectrum modulation downstream signal and Gaussian noise sum, and wherein QPSK modulation downstream signal is far longer than the band spectrum modulation downstream signal.

Concrete, described input signal is suc as formula 5:

$r\left(t\right)=A\left\{\right[\underset{k=-\∞}{\overset{+\∞}{\mathrm{\Σ}}}{a}_{\mathrm{Ik}}{h}_1(t-{\mathrm{kT}}_1)]\cos \left({\mathrm{\ω}}_{1}t\right)+[\underset{k=-\∞}{\overset{+\∞}{\mathrm{\Σ}}}{a}_{\mathrm{Qk}}{h}_1(t-k{T}_1)\left]\sin \left({\mathrm{\ω}}_{1}t\right)\right]\}$

$+B\left\{\right[\underset{k=-\∞}{\overset{+\∞}{\mathrm{\Σ}}}{b}_{\mathrm{Ik}}\left(t\right)m_i\left(t\right)h_2(t-{\mathrm{kT}}_2)]\cos \left({\mathrm{\ω}}_{2}t\right)+[\underset{k=-\∞}{\overset{+\∞}{\mathrm{\Σ}}}{b}_{\mathrm{Qk}}\left(t\right)m_q\left(t\right)h_2(t-k{T}_2)\left]\sin \left({\mathrm{\ω}}_{2}t\right)\right\}$

$+n\left(t\right)$

$=r_1\left(t\right)+r_2\left(t\right)+n\left(t\right)$

(formula 5)

Wherein, r (t) is input signal, r ₁Be QPSK modulation downstream signal, r ₂Be the band spectrum modulation downstream signal, n (t) is Gaussian noise, condition described according to background technology, modulated spread spectrum signal r ₂(t) amplitude is far smaller than qpsk modulation signal r ₁(t) amplitude (usually less than 1/20), modulated spread spectrum signal r ₂(t) can not affect qpsk modulation signal r ₁(t) normal demodulation.

r ₁Suc as formula 1:

$r_1\left(t\right)=A\left\{\right[\underset{k=-\∞}{\overset{+\∞}{\mathrm{\Σ}}}{a}_{\mathrm{Ik}}{h}_1(t-{\mathrm{kT}}_1)]\cos \left({\mathrm{\ω}}_{1}t\right)+[\underset{k=-\∞}{\overset{+\∞}{\mathrm{\Σ}}}{a}_{\mathrm{Qk}}{h}_1(t-k{T}_1)\left]\sin \left({\mathrm{\ω}}_{1}t\right)\right]\}$ (formula 1)

Wherein, A is the amplitude of qpsk modulation signal, and its value is for just; a _Ik, a _QkBe respectively the data message of I road in qpsk modulation signal, Q road transmission, value is ± 1; h ₁(t-kT ₁) be the pulse shock response of transmitted signal, its corresponding frequency response function is that rolloff-factor is α ₁The square root raised cosine function, α ₁Span between 0～1; T ₁A _IkAnd a _QkCode-element period, 1/T ₁It is the baud rate of QPSK signal; ω ₁=2 π f ₁Be the angular frequency of QPSK carrier signal, t is the time, and unit is second.

r ₂Suc as formula 2:

$r_2\left(t\right)=B\left\{\right[\underset{k=-\∞}{\overset{+\∞}{\mathrm{\Σ}}}{b}_{\mathrm{Ik}}\left(t\right)m_i\left(t\right)h_2(t-{\mathrm{kT}}_2)]\cos \left({\mathrm{\ω}}_{2}t\right)+[\underset{k=-\∞}{\overset{+\∞}{\mathrm{\Σ}}}{b}_{\mathrm{Qk}}\left(t\right)m_q\left(t\right)h_2(t-k{T}_2)\left]\sin \left({\mathrm{\ω}}_{2}t\right)\right\}$

(formula 2)

Wherein, B is the amplitude of modulated spread spectrum signal, and its value is always for just; b _Ik, b _QkBe respectively the data message of modulated spread spectrum signal I road, Q road transmission, value is ± 1; , m _i(t), m _q(t) be the frequency expansion sequence on modulated spread spectrum signal I road, Q road, value is ± 1, its nominal rate and r ₁(t) a _IkAnd a _QkIdentical; m _i(t), m _q(t) speed is far longer than b _Ik, b _QkSpeed, m _i(t), m _q(t) and b _Ik, b _QkThe ratio of speed is called spread spectrum coefficient k; h ₂(t-kT ₂) be the pulse shock response of transmitted signal, its corresponding frequency response function is α for rolloff-factor ₂The square root raised cosine function, α ₂Span between 0～1; T ₂M _i(t), m _q(t) code-element period, 1/T ₂Its baud rate, its nominal value and T ₁Identical; ω ₂=2 π f ₂The angular frequency of signal, its nominal value and ω ₁Identical.

Local oscillator 2 is for generation of the required orthogonal local oscillation signal of demodulation, the carrier synchronization of local oscillator carrier wave and QPSK modulation downstream signal, local frequency equals the carrier frequency of QPSK modulation downstream signal, and the orthogonal local oscillation signal of local oscillator output multiplies each other with every road input signal respectively and exports I road difference frequency and frequency signal and Q road difference frequency and frequency signal.Concrete, after the normal demodulation of qpsk modulation signal, receiver local oscillator carrier wave is synchronizeed with the QPSK signal carrier under its carrier synchronization circuit is controlled, receiver local frequency ω ₀Equal to input qpsk modulation signal carrier frequency ω ₁

The one QPSK Signal Matching filter 3, the 2nd QPSK Signal Matching filter 4, be used for filtering described I road difference frequency respectively and signal and Q road difference frequency and I road, Q road and the signal frequently of signal frequently frequently, export described I road, Q road difference frequency signal as I road, Q roadbed band signal x _i(t), x _q(t), described I road, Q roadbed band signal are QPSK baseband signal, spread baseband signal and Gaussian noise sum, and wherein the amplitude of QPSK baseband signal is far longer than spread baseband signal.

Concrete, I roadbed band signal is suc as formula 6:

$x_i\left(t\right)=A^{\′}\underset{k=-\∞}{\overset{+\∞}{\mathrm{\Σ}}}{a}_{\mathrm{Ik}}{h}_1(t-{\mathrm{kT}}_1)$

$+B^{\′}\left\{\right[\underset{k=-\∞}{\overset{+\∞}{\mathrm{\Σ}}}{b}_{\mathrm{Ik}}\left(t\right)m_i\left(t\right)h_2(t-{\mathrm{kT}}_2)]\cos ({\mathrm{\ω}}_2-{\mathrm{\ω}}_{1}t)+[\underset{k=-\∞}{\overset{+\∞}{\mathrm{\Σ}}}{b}_{\mathrm{Qk}}\left(t\right)m_q\left(t\right)h_2(t-{\mathrm{kT}}_2)\left]\sin ({\mathrm{\ω}}_2-{\mathrm{\ω}}_{1}t)\right\}$

$+n_i\left(t\right)$

$=u_i\left(t\right)+v_i\left(t\right)+n_i\left(t\right)$

(formula 6)

Q roadbed band signal is suc as formula 7:

$x_q\left(t\right)=A^{\′}\underset{k=-\∞}{\overset{+\∞}{\mathrm{\Σ}}}{a}_{\mathrm{Qk}}{h}_1(t-{\mathrm{kT}}_1)$

$+B^{\′}\left\{\right[\underset{k=-\∞}{\overset{+\∞}{\mathrm{\Σ}}}{b}_{\mathrm{Qk}}\left(t\right)m_q\left(t\right)h_2(t-{\mathrm{kT}}_2)]\cos ({\mathrm{\ω}}_2-{\mathrm{\ω}}_{1}t)+[\underset{k=-\∞}{\overset{+\∞}{\mathrm{\Σ}}}{b}_{\mathrm{Ik}}\left(t\right)m_i\left(t\right)h_2(t-{\mathrm{kT}}_2)\left]\sin ({\mathrm{\ω}}_2-{\mathrm{\ω}}_{1}t)\right\}$

$+n_q\left(t\right)$

$=u_q\left(t\right)+v_q\left(t\right)+n_q\left(t\right)$

(formula 7)

Wherein, x _i(t) be I roadbed band signal, x _q(t) Q roadbed band signal, u _i(t), u _q(t) be respectively the base band component on QPSK signal I road, Q road, v _i(t), v _q(t) be respectively the base band component on spread-spectrum signal I road, Q road, n _i(t), n _q(t) be respectively the Gaussian noise on I road, Q road, the base band component of QPSK signal is far longer than the base band component of spread-spectrum signal, i.e. u _i(t)〉〉 v _i(t), u _q(t)〉〉 v _q(t), due to ω ₁, ω ₂Substantially equal, v _i(t), v _q(t) amplitude can slowly change, and A' is u _i(t), u _q(t) range weight, A' is directly proportional to A; B' is v _i(t), v _q(t) range weight, B' is directly proportional to B.

Qpsk demodulator 5 is used for exporting respectively I road, Q road QPSK demodulating data a' according to described I road, Q roadbed band signal _Ik,, a' _Qk

Concrete, export I road QPSK demodulating data a' after the demodulation of QPSK signal _IkWith Q road QPSK demodulating data a' _Qk, value is ± 1; Except a small amount of error code, most a' _IkAnd a' _QkThe data message a that transmits with the QPSK signal _IkAnd a _QkIdentical.

The 3rd QPSK matched filter 6, the 4th QPSK matched filter 7 are used for respectively according to described I road, QPSK demodulating data output I road, Q road, Q road QPSK regeneration baseband signal u' _i(t), u' _q(t).

Concrete, QPSK demodulating data a' _IkAnd a' _QkThe input pulse impulse response is h respectively ₁(t-kT) the 3rd QPSK matched filter, the 4th QPSK matched filter produce I road, Q road QPSK regeneration baseband signal u' as 8 formulas _i(t) and u' _q(t).

$\left\{\begin{array}{c}{u^{\′}}_i\left(t\right)=A^{\′\′}\underset{k=-\∞}{\overset{+\∞}{\mathrm{\Σ}}}{a^{\′}}_{\mathrm{Ik}}{h}_1(t-{\mathrm{kT}}_1)\\ {u^{\′}}_q\left(t\right)=A^{\′\′}\underset{k=-\∞}{\overset{+\∞}{\mathrm{\Σ}}}{a^{\′}}_{\mathrm{Qk}}{h}_1(t-\mathrm{kT})\end{array}\right.$ (formula 8)

Wherein, u' _i(t) be I road QPSK regeneration baseband signal, u ' _q(t) be Q road QPSK regeneration baseband signal, a' _IkBe I road QPSK demodulating data, a' _QkBe I road QPSK demodulating data, h ₁(t-kT ₁) be the pulse shock response of described the 3rd QPSK matched filter 6, the 4th QPSK matched filter 7, A " is u' _i(t), u ' _q(t) range weight.

If QPSK signal data information is processed through error correction coding, described receiver comprises that also a channel error correcting deocder 13 is used for encoding to generate I road, Q road coded data again after the QPSK demodulating data error-correcting decoding of described I road, Q road again, and described the 3rd QPSK matched filter 6, the 4th QPSK matched filter 7 are according to described I road, Q road coded data output I road, the Q road QPSK baseband signal of regenerating again.

Concrete, in order to reduce QPSK demodulating data a' _Ik, a' _QkError code causes regeneration baseband signal u' _i(t), u' _q(t) if distortion is QPSK signal data information a _Ik, a _QkProcess through error correction coding, can be with demodulating data a' _Ik, a' _QkEncode again after error-correcting decoding, produce coded data a again " _Ik, a " _Qk, then incite somebody to action coded data a again " _IkAnd a " _QkThe input pulse impulse response is h respectively ₁(t-kT ₁) matched filter, produce the QPSK demodulating data regeneration baseband signal u' suc as formula 9 _i(t) and u' _q(t) (see figure 5).Due to a' _Ik, a' _QkCompare a " _Ik, a " _QkHas the lower error rate (usually will hang down 3 above orders of magnitude), by a " _Ik, a " _QkThe u' that produces _i(t), u' _q(t) has less distortion.

$\left\{\begin{array}{c}{u^{\′}}_i\left(t\right)=A^{\′\′}\underset{k=-\∞}{\overset{+\∞}{\mathrm{\Σ}}}{a^{\′\′}}_{\mathrm{Ik}}{h}_1(t-\mathrm{kT})\\ {u^{\′}}_q\left(t\right)=A^{\′\′}\underset{k=-\∞}{\overset{+\∞}{\mathrm{\Σ}}}{a^{\′\′}}_{\mathrm{qk}}{h}_1(t-\mathrm{kT})\end{array}\right.$ (formula 9)

Amplitude adjusting circuit 8 is used for adjusting first, second, and third pair of QPSK base band reproducing signals of parameter output according to described I road Q road QPSK regeneration baseband signal with first, second, and third amplitude, and with second pair of QPSK base band reproducing signals as the optimal compensation QPSK base band reproducing signals, first pair of QPSK base band reproducing signals is as overcompensation QPSK base band reproducing signals, and the 3rd pair of QPSK base band reproducing signals is as undercompensation QPSK base band reproducing signals.

Concrete, QPSK regeneration baseband signal u' _i(t) and u' _q(t) through amplitude adjusting circuit, form copying of three pairs of QPSK baseband signals, first, second, and third pair of QPSK base band reproducing signals is suc as formula 10.

$\left\{\begin{array}{cc}{u^{\′\′}}_{\mathrm{in}}\left(t\right)=p_n{u^{\′}}_i\left(t\right)& n=\mathrm{1,2,3}\\ {u^{\′\′}}_{\mathrm{qn}}\left(t\right)=p_n{u^{\′}}_q\left(t\right)& n=\mathrm{1,2,3}\end{array}\right.$ (formula 10)

Wherein, wherein, u " _in(t) be respectively first, second, and third different amplitude I road QPSK base band reproducing signals, u " _qn(t) be the Q road QPSK base band reproducing signals of first, second, and third different amplitude, p ₁, p ₂, p ₃First, second, and third amplitude that is respectively is adjusted parameter, p ₁P ₂P ₃, p ₁-p ₂=p ₂-p ₃=Δ, the described control logic circuit signal to noise ratio after according to the spread-spectrum signal despreading is adjusted p ₁, p ₂, p ₃Numerical value so that second couple of QPSK base band reproducing signals u " _i2(t), u " _q2(t) approach the base band component u on QPSK signal I road, Q road most _i(t), u _q(t), when the second the tunnel was in the optimal compensation, the despreading signal to noise ratio reached maximum; First pair of this moment be for overcompensation, its despreading signal to noise ratio little with second pair; Third Road is undercompensation, and its despreading signal to noise ratio is also less than second pair; First, second, and third pair of despread signal signal to noise ratio forms a peak, whether reaches the optimal compensation in order to differentiate.

Signal delay module 9 is used for respectively described I road, Q roadbed band signal are fixed time-delay, and I road, Q roadbed band signal and QPSK base band reproducing signals after time-delay are complementary in time.

Concrete, in order to compensate u " _i1(t)～u " _i3(t), u " _q1(t)～u " _q3(t) form required time delay, I road, Q roadbed band signal x _i(t), x _q(t) must be through corresponding constant time lag, after time-delay, signal is with x' _i(t), x' _q(t) expression.

After signal cancellation module 10 is used for delaying time, I road, the rear Q roadbed band signal of time-delay subtract each other with described first, second, and third pair of QPSK base band reproducing signals respectively, export first, second, and third pair of spread baseband signal.

Concrete, x' _i(t) respectively with u " _i1(t), u " _i2(t), u " _i3(t) subtract each other x' _i(t) u in _i(t) composition is cancelled, and produces three I road band spectrum modulation baseband signal y _i1(t), y _i2(t), y _i3(t); x' _q(t) respectively with u " _q1(t), u " _q2(t), u " _q3(t) subtract each other x' _q(t) u in _q(t) composition is cancelled, and produces three Q road band spectrum modulation baseband signal y _q1(t), y _q2(t), y _q3(t).Described first, second, and third pair of spread baseband signal is suc as formula 11.

$\left\{\begin{array}{cc}{y}_{\mathrm{in}}\left(t\right)={x_i}^{\′}\left(t\right)-{u^{\′\′}}_{\mathrm{in}}\left(t\right)& \\ =u_i\left(t\right)+v_i\left(t\right)+n_i\left(t\right)-{u^{\′\′}}_{\mathrm{in}}\left(t\right)& n=\mathrm{1,2,3}\\ =v_i\left(t\right)+\mathrm{\Δ}{u}_{\mathrm{in}}\left(t\right)+n_i\left(t\right)& \\ & \\ y_{\mathrm{qn}}\left(t\right)={x_q}^{\′}\left(t\right)-{u^{\′\′}}_{\mathrm{qn}}\left(t\right)& \\ =u_q\left(t\right)+v_q\left(t\right)+n_q\left(t\right)-{u^{\′\′}}_{\mathrm{qn}}\left(t\right)& n=\mathrm{1,2,3}\\ =v_q\left(t\right)+\mathrm{\Δ}{u}_{\mathrm{qn}}\left(t\right)+n_q\left(t\right)& \end{array}\right.$ (formula 11)

Wherein, y _in(t) be I road spread baseband signal, y _qn(t) be Q road spread baseband signal, Δ u _in(t)=u _i(t)-u " _in(t) be the remaining component of I road QPSK baseband signal component, Δ u _qn(t)=u _q(t)-u " _qn(t), be the remaining component of Q road QPSK baseband signal component.

Signal to noise ratio module 11 is used for described first, second, and third pair of spread baseband signal carried out respectively despreading, and calculates and export first, second, and third despread signal signal to noise ratio.

Concrete, the signal to noise ratio after first, second, and third pair of quadrature spread baseband signal carried out respectively despreading and calculated despreading, if spread spectrum coefficient is k, the signal to noise ratio after the spread-spectrum signal despreading is represented by formula 12:

(formula 12)

As QPSK base band reproducing signals u " _in(t) and u " _qnWhen (t) complete and QPSK baseband signal is mated, Δ u _in(t), Δ u _qn(t) become and zero, the signal to noise ratio after the spread-spectrum signal despreading is by formula 13 expressions:

(formula 13)

Wherein, [kv (t)] ²=[kv _i(t)] ²+ [kv _q(t)] ²The signal energy after despreading, [n (t)] ²=[n _i(t)] ²+ [n _q(t)] ²It is the noise energy after despreading.Compare with the signal to noise ratio suc as formula 4 usual manner band spread receiver despread signal,

The despread signal signal to noise ratio that the present embodiment obtains improves significantly.

Concrete, described first, second, and third despread signal signal to noise ratio by suc as formula 14, formula 15, formula 16 calculate.

(formula 14)

(formula 15)

(formula 16)

Wherein,

Be first, second, and third despread signal signal to noise ratio, y _in(t), y _qn(t) be the band spectrum modulation baseband signal, m _i(t) be I road frequency expansion sequence, m _q(t) be Q road frequency expansion sequence, k is spread spectrum coefficient; As shown in Figure 6, z _i1(t), z _q1(t), z _i2(t), z _q2(t) by I road spread baseband signal y _in(t) and Q road spread baseband signal y _qn(t) respectively with the local frequency expansion sequence m on modulated spread spectrum signal I road, Q road _i(t) and m _q(t) carry out mould two and add the computing generation; S _{Despreading n}Be despread signal energy, N _{Despreading n}Be the despread signal noise energy; When local I road, Q road frequency expansion sequence is synchronizeed with the input signal frequency expansion sequence, despread signal energy S _DespreadingReach peak value; N with formula 16 estimations _DespreadingIn comprised Δ u _i(t), Δ u _q(t), v _i(t), v _q(t), n _i(t), n _q(t) component is due to common v _i(t), v _q(t) component is much smaller than n _i(t), n _q(t) component, v _i(t), v _q(t) impact can be ignored.

Control logic circuit 12 is used for adjusting described first, second, and third amplitude according to described first, second, and third despread signal signal to noise ratio and adjusts parameter, and control the signal to noise ratio module and adjust first, second, and third corresponding despread signal signal to noise ratio, until being maximum and the first and second despread signal signal to noise ratios, the second despread signal signal to noise ratio equates.

Concrete, baseband signal x' after time-delay _i(t), x' _q(t) with QPSK base band reproducing signals u " _in(t), u " _qn(t) (n=1,2,3) subtracts each other x' _i(t), x' _q(t) the QPSK base band component in reduces, and produces first, second, and third couple of spread baseband signal y _in(t), y _qn(t) (n=1,2,3).Calculate spread baseband signal y according to formula 14, formula 15, formula 16 _in(t), y _qn(t) signal to noise ratio (S/N) after (n=1,2,3) despreading _{Despreading n}(n=1,2,3).According to (S/N) _{Despreading n}The change amplitude is adjusted parameter p _nThe numerical value of (n=1,2,3) (flow process is as shown in Figure 7): when

The time, reduce p _nWhen

The time, increase p _nWhen

And During for maximum, think u " _i2(t), u " _q2(t) adjust to the best, p _nNumerical value is constant.By continuous adjustment p _n, finally make x' _i(t), x' _q(t) the QPSK base band component in is cancelled, thereby obtains maximum despread signal signal to noise ratio (S/N) _{Despreading 2}When the second the tunnel was in the optimal compensation, the despreading signal to noise ratio reached maximum; Be overcompensation this moment the 1 tunnel, and its despreading signal to noise ratio is little of the second the tunnel; The 3 the tunnel is undercompensation, and its despreading signal to noise ratio is also less than the second the tunnel; First, second, and third despread signal signal to noise ratio forms a peak, whether reaches the optimal compensation in order to differentiate.

Fig. 8 and shown in Figure 9 be qpsk modulation signal Amplitude Ratio modulated spread spectrum signal amplitude high 20 times (the high 26dB of power), spread spectrum coefficient is 127, snr of received signal is under the 20dB condition, the simulation result of the signal to noise ratio after the spread-spectrum signal despreading; Wherein Fig. 8 adopts signal to noise ratio after the spread-spectrum signal despreading of usual manner, and Fig. 9 adopts signal to noise ratio after spread-spectrum signal despreading of the present invention; In Fig. 8 and Fig. 9, transverse axis is the time, the longitudinal axis is power (unit is dB), and the white line in figure in the first half is power after the spread-spectrum signal despreading, and the white surface area in figure in the latter half is noise, as seen adopt the method for the present embodiment, the spread-spectrum signal signal to noise ratio has the above improvement of 10dB.

Adopt the method for the present embodiment in satellite communication system shown in Figure 1, with the same transmission conditions of usual manner under, can improve the signal to noise ratio after the spread-spectrum signal despreading, improve the transmission quality of spread spectrum communication; Require to reduce the transmitting power of spread spectrum transmitter under constant condition at the spread-spectrum signal spreading gain, reduce spread-spectrum signal to the impact of QPSK signal, improve the disguise of spread-spectrum signal; Require to reduce the spread spectrum coefficient of spread-spectrum signal under constant condition in signal to noise ratio after the spread-spectrum signal despreading, improve the transmission rate of spread spectrum communication system.

The professional can also further recognize, unit and the algorithm steps of each example of describing in conjunction with embodiment disclosed herein, can realize with electronic hardware, computer software or combination both, for the interchangeability of hardware and software clearly is described, composition and the step of each example described in general manner according to function in the above description.These functions are carried out with hardware or software mode actually, depend on application-specific and the design constraint of technical scheme.The professional and technical personnel can specifically should be used for realizing described function with distinct methods to each, but this realization should not thought and exceeds scope of the present invention.

Obviously, those skilled in the art can carry out various changes and modification and not break away from the spirit and scope of the present invention invention.Like this, if within of the present invention these were revised and modification belongs to the scope of claim of the present invention and equivalent technologies thereof, the present invention also was intended to comprise these change and modification.

Claims (10)

1. a method of improving satellite spectrum-spread communication receiver despread signal signal to noise ratio, is characterized in that, comprising:

One input signal splitter of receiver obtains input signal, and described input signal is divided into the equal described input signal of two-way, the described input signal in each road is QPSK modulation downstream signal, band spectrum modulation downstream signal and Gaussian noise sum, and wherein QPSK modulation downstream signal is far longer than the band spectrum modulation downstream signal;

The carrier synchronization of the local oscillator carrier wave that one local oscillator of receiver produces and QPSK modulation downstream signal, local frequency equals the carrier frequency of QPSK modulation downstream signal, and the orthogonal local oscillation signal of local oscillator output multiplies each other with every road input signal respectively and exports I road difference frequency and frequency signal and Q road difference frequency and frequency signal;

I road, Q road and frequency signal in the one QPSK Signal Matching filter of described receiver, the 2nd QPSK Signal Matching filter difference filtering described I road difference frequency and frequency signal and Q road difference frequency and frequency signal, export described I road, Q road difference frequency signal as I road, Q roadbed band signal, described I road, Q roadbed band signal are QPSK baseband signal, spread baseband signal and Gaussian noise sum, and wherein the amplitude of QPSK baseband signal is far longer than spread baseband signal;

One qpsk demodulator of described receiver is exported respectively I road, Q road QPSK demodulating data according to described I road, Q roadbed band signal;

One the 3rd QPSK matched filter of described receiver, the 4th QPSK matched filter are respectively according to described I road, QPSK demodulating data output I road, Q road, the Q road QPSK baseband signal of regenerating;

One amplitude adjusting circuit of described receiver is adjusted first, second, and third pair of QPSK base band reproducing signals of parameter output according to described I road, Q road QPSK regeneration baseband signal and first, second, and third amplitude, and with second pair of QPSK base band reproducing signals as the optimal compensation QPSK base band reproducing signals, first pair of QPSK base band reproducing signals is as overcompensation QPSK base band reproducing signals, and the 3rd pair of QPSK base band reproducing signals is as undercompensation QPSK base band reproducing signals;

One signal delay module of described receiver is fixed time-delay to described I road, Q roadbed band signal respectively, and I road, Q roadbed band signal and QPSK base band reproducing signals after time-delay are complementary in time;

After one signal cancellation module of described receiver will be delayed time respectively, I road, the rear Q roadbed band signal of time-delay subtract each other with described first, second, and third pair of QPSK base band reproducing signals respectively, export first, second, and third pair of spread baseband signal;

One signal to noise ratio module of described receiver is carried out respectively despreading to described first, second, and third pair of spread baseband signal, and calculates and export first, second, and third despread signal signal to noise ratio;

One control logic circuit of described receiver is adjusted described first, second, and third amplitude according to described first, second, and third despread signal signal to noise ratio and is adjusted parameter, and control the signal to noise ratio module and adjust first, second, and third corresponding despread signal signal to noise ratio, until being maximum and the first and second despread signal signal to noise ratios, the second despread signal signal to noise ratio equates.

2. the method for improving satellite spectrum-spread communication receiver despread signal signal to noise ratio as claimed in claim 1, it is characterized in that, if QPSK signal data information is processed through error correction coding, described the 3rd QPSK matched filter, the 4th QPSK matched filter comprise according to the step of described I road, QPSK demodulating data output I road, Q road, Q road QPSK regeneration baseband signal respectively:

One channel error correcting deocder of described receiver encodes to generate I road, Q road coded data again after with described I road, Q road QPSK demodulating data error-correcting decoding again, and described the 3rd QPSK matched filter, the 4th QPSK matched filter are according to described I road, Q road coded data output I road, the Q road QPSK baseband signal of regenerating again.

3. the method for improving satellite spectrum-spread communication receiver despread signal signal to noise ratio as claimed in claim 1, is characterized in that, the formula of described input signal is as follows:

$r\left(t\right)=A\left\{\right[\underset{k=-\∞}{\overset{+\∞}{\mathrm{\Σ}}}{a}_{\mathrm{Ik}}{h}_1(t-{\mathrm{kT}}_1)]\cos \left({\mathrm{\ω}}_{1}t\right)+[\underset{k=-\∞}{\overset{+\∞}{\mathrm{\Σ}}}{a}_{\mathrm{Qk}}{h}_1(t-k{T}_1)\left]\sin \left({\mathrm{\ω}}_{1}t\right)\right]\}$

$+B\left\{\right[\underset{k=-\∞}{\overset{+\∞}{\mathrm{\Σ}}}{b}_{\mathrm{Ik}}\left(t\right)m_i\left(t\right)h_2(t-{\mathrm{kT}}_2)]\cos \left({\mathrm{\ω}}_{2}t\right)+[\underset{k=-\∞}{\overset{+\∞}{\mathrm{\Σ}}}{b}_{\mathrm{Qk}}\left(t\right)m_q\left(t\right)h_2(t-k{T}_2)\left]\sin \left({\mathrm{\ω}}_{2}t\right)\right\}$

$+n\left(t\right)$

$=r_1\left(t\right)+r_2\left(t\right)+n\left(t\right)$

Wherein, r (t) is input signal, r ₁Be QPSK modulation downstream signal, r ₂Be the band spectrum modulation downstream signal, n (t) is Gaussian noise;

r ₁Formula as follows:

$r_1\left(t\right)=A\left\{\right[\underset{k=-\∞}{\overset{+\∞}{\mathrm{\Σ}}}{a}_{\mathrm{Ik}}{h}_1(t-{\mathrm{kT}}_1)]\cos \left({\mathrm{\ω}}_{1}t\right)+[\underset{k=-\∞}{\overset{+\∞}{\mathrm{\Σ}}}{a}_{\mathrm{Qk}}{h}_1(t-k{T}_1)\left]\sin \left({\mathrm{\ω}}_{1}t\right)\right]\}$

A is the amplitude of qpsk modulation signal, and its value is for just; a _Ik, a _QkBe respectively the data message of I road in qpsk modulation signal, Q road transmission, value is ± 1; h ₁(t-kT ₁) be the pulse shock response of transmitted signal, its corresponding frequency response function is that rolloff-factor is α ₁The square root raised cosine function, α ₁Span between 0～1; T ₁A _IkAnd a _QkCode-element period, 1/T ₁It is the baud rate of QPSK signal; ω ₁=2 π f ₁Be the angular frequency of QPSK carrier signal, t is the time, and unit is second,

r ₂Formula as follows:

$r_2\left(t\right)=B\left\{\right[\underset{k=-\∞}{\overset{+\∞}{\mathrm{\Σ}}}{b}_{\mathrm{Ik}}\left(t\right)m_i\left(t\right)h_2(t-{\mathrm{kT}}_2)]\cos \left({\mathrm{\ω}}_{2}t\right)+[\underset{k=-\∞}{\overset{+\∞}{\mathrm{\Σ}}}{b}_{\mathrm{Qk}}\left(t\right)m_q\left(t\right)h_2(t-k{T}_2)\left]\sin \left({\mathrm{\ω}}_{2}t\right)\right\}$

B is the amplitude of modulated spread spectrum signal, and its value is always for just; b _Ik, b _QkBe respectively the data message of modulated spread spectrum signal I road, Q road transmission, value is ± 1; , m _i(t), m _q(t) be the frequency expansion sequence on modulated spread spectrum signal I road, Q road, value is ± 1, its nominal rate and r ₁(t) a _IkAnd a _QkIdentical; m _i(t), m _q(t) speed is far longer than b _Ik, b _QkSpeed, m _i(t), m _q(t) and b _Ik, b _QkThe ratio of speed is called spread spectrum coefficient k; h ₂(t-kT ₂) be the pulse shock response of transmitted signal, its corresponding frequency response function is α for rolloff-factor ₂The square root raised cosine function, α ₂Span between 0～1; T ₂M _i(t), m _q(t) code-element period, 1/T ₂Its baud rate, its nominal value and T ₁Identical; ω ₂=2 π f ₂The angular frequency of signal, its nominal value and ω ₁Identical.

4. the method for improving satellite spectrum-spread communication receiver despread signal signal to noise ratio as claimed in claim 3, is characterized in that, the formula of I roadbed band signal is as follows:

$x_i\left(t\right)=A^{\′}\underset{k=-\∞}{\overset{+\∞}{\mathrm{\Σ}}}{a}_{\mathrm{Ik}}{h}_1(t-{\mathrm{kT}}_1)$

$+B^{\′}\left\{\right[\underset{k=-\∞}{\overset{+\∞}{\mathrm{\Σ}}}{b}_{\mathrm{Ik}}\left(t\right)m_i\left(t\right)h_2(t-{\mathrm{kT}}_2)]\cos ({\mathrm{\ω}}_2-{\mathrm{\ω}}_{1}t)+[\underset{k=-\∞}{\overset{+\∞}{\mathrm{\Σ}}}{b}_{\mathrm{Qk}}\left(t\right)m_q\left(t\right)h_2(t-{\mathrm{kT}}_2)\left]\sin ({\mathrm{\ω}}_2-{\mathrm{\ω}}_{1}t)\right\}$

$+n_i\left(t\right)$

$=u_i\left(t\right)+v_i\left(t\right)+n_i\left(t\right)$

The formula of Q roadbed band signal is as follows:

$x_q\left(t\right)=A^{\′}\underset{k=-\∞}{\overset{+\∞}{\mathrm{\Σ}}}{a}_{\mathrm{Qk}}{h}_1(t-{\mathrm{kT}}_1)$

$+B^{\′}\left\{\right[\underset{k=-\∞}{\overset{+\∞}{\mathrm{\Σ}}}{b}_{\mathrm{Qk}}\left(t\right)m_q\left(t\right)h_2(t-{\mathrm{kT}}_2)]\cos ({\mathrm{\ω}}_2-{\mathrm{\ω}}_{1}t)+[\underset{k=-\∞}{\overset{+\∞}{\mathrm{\Σ}}}{b}_{\mathrm{Ik}}\left(t\right)m_i\left(t\right)h_2(t-{\mathrm{kT}}_2)\left]\sin ({\mathrm{\ω}}_2-{\mathrm{\ω}}_{1}t)\right\},$

$+n_q\left(t\right)$

$=u_q\left(t\right)+v_q\left(t\right)+n_q\left(t\right)$

Wherein, x _i(t) be I roadbed band signal, x _q(t) Q roadbed band signal, u _i(t), u _q(t) be respectively the base band component on QPSK signal I road, Q road, v _i(t), v _q(t) be respectively the base band component on spread-spectrum signal I road, Q road, n _i(t), n _q(t) be respectively the Gaussian noise on I road, Q road, the base band component of QPSK signal is far longer than the base band component of spread-spectrum signal, i.e. u _i(t)〉〉 v _i(t), u _q(t)〉〉 v _q(t), due to ω ₁, ω ₂Substantially equal, v _i(t), v _q(t) amplitude can slowly change, and A' is u _i(t), u _q(t) range weight, A' is directly proportional to A; B' is v _i(t), v _q(t) range weight, B' is directly proportional to B.

5. the method for improving satellite spectrum-spread communication receiver despread signal signal to noise ratio as claimed in claim 4, is characterized in that, the formula of I road, Q road QPSK regeneration baseband signal is:

$\left\{\begin{array}{c}{u^{\′}}_i\left(t\right)=A^{\′\′}\underset{k=-\∞}{\overset{+\∞}{\mathrm{\Σ}}}{a^{\′}}_{\mathrm{Ik}}{h}_1(t-{\mathrm{kT}}_1)\\ {u^{\′}}_q\left(t\right)=A^{\′\′}\underset{k=-\∞}{\overset{+\∞}{\mathrm{\Σ}}}{a^{\′}}_{\mathrm{Qk}}{h}_1(t-\mathrm{kT})\end{array}\right.$

Wherein, u' _i(t) be I road QPSK regeneration baseband signal, u ' _q(t) be Q road QPSK regeneration baseband signal, a' _IkBe I road QPSK demodulating data, a' _QkBe I road QPSK demodulating data, h ₁(t-kT ₁) be the pulse shock response of described the 3rd QPSK matched filter, the 4th QPSK matched filter, A " is u' _i(t), u ' _q(t) range weight.

6. the method for improving satellite spectrum-spread communication receiver despread signal signal to noise ratio as claimed in claim 5, is characterized in that, the formula of first, second, and third pair of QPSK base band reproducing signals is as follows:

$\left\{\begin{array}{cc}{u^{\′\′}}_{\mathrm{in}}\left(t\right)=p_n{u^{\′}}_i\left(t\right)& n=\mathrm{1,2,3}\\ {u^{\′\′}}_{\mathrm{qn}}\left(t\right)=p_n{u^{\′}}_q\left(t\right)& n=\mathrm{1,2,3}\end{array}\right.$

Wherein, u " _in(t) be respectively first, second, and third different amplitude I road QPSK base band reproducing signals, u " _qn(t) be the Q road QPSK base band reproducing signals of first, second, and third different amplitude, p ₁, p ₂, p ₃First, second, and third amplitude that is respectively is adjusted parameter, p ₁P ₂P ₃, p ₁-p ₂=p ₂-p ₃=Δ, the described control logic circuit signal to noise ratio after according to the spread-spectrum signal despreading is adjusted p ₁, p ₂, p ₃Numerical value so that second couple of QPSK base band reproducing signals u " _i2(t), u " _q2(t) approach the base band component u on QPSK signal I road, Q road most _i(t), u _q(t).

7. the method for improving satellite spectrum-spread communication receiver despread signal signal to noise ratio as claimed in claim 6, is characterized in that, the formula of described first, second, and third pair of spread baseband signal is as follows:

$\left\{\begin{array}{cc}{y}_{\mathrm{in}}\left(t\right)={x_i}^{\′}\left(t\right)-{u^{\′\′}}_{\mathrm{in}}\left(t\right)& \\ =u_i\left(t\right)+v_i\left(t\right)+n_i\left(t\right)-{u^{\′\′}}_{\mathrm{in}}\left(t\right)& n=\mathrm{1,2,3}\\ =v_i\left(t\right)+\mathrm{\Δ}{u}_{\mathrm{in}}\left(t\right)+n_i\left(t\right)& \\ & \\ y_{\mathrm{qn}}\left(t\right)={x_q}^{\′}\left(t\right)-{u^{\′\′}}_{\mathrm{qn}}\left(t\right)& \\ =u_q\left(t\right)+v_q\left(t\right)+n_q\left(t\right)-{u^{\′\′}}_{\mathrm{qn}}\left(t\right)& n=\mathrm{1,2,3}\\ =v_q\left(t\right)+\mathrm{\Δ}{u}_{\mathrm{qn}}\left(t\right)+n_q\left(t\right)& \end{array}\right.$

Wherein, y _in(t) be I road spread baseband signal, y _qn(t) be Q road spread baseband signal, Δ u _in(t)=u _i(t)-u " _in(t) be the remaining component of I road QPSK baseband signal component, Δ u _qn(t)=u _q(t)-u " _qn(t), be the remaining component of Q road QPSK baseband signal component.

8. the method for improving satellite spectrum-spread communication receiver despread signal signal to noise ratio as claimed in claim 7, is characterized in that, it is as follows that the formula of first, second, and third despread signal signal to noise ratio is calculated and exported to described signal to noise ratio module:

Wherein, Be respectively first, second, and third despread signal signal to noise ratio, m _i(t) be I road frequency expansion sequence, m _q(t) be Q road frequency expansion sequence, spread spectrum coefficient is k, z _i1(t), z _q1(t), z _i2(t), z _q2(t) by I road spread baseband signal y _in(t), Q road spread baseband signal y _qn(t) respectively with described local frequency expansion sequence m _i(t) and m _q(t) carry out mould two and add computing generation, S _{Despreading n}Be despread signal energy, N _{Despreading n}Be the despread signal noise energy, when local I road, Q road frequency expansion sequence is synchronizeed with the input signal frequency expansion sequence, despread signal energy S _{Despreading n}Reach peak value.

9. the method for improving satellite spectrum-spread communication receiver despread signal signal to noise ratio as claimed in claim 8, it is characterized in that, the control logic circuit of described receiver is adjusted described first, second, and third amplitude according to described first, second, and third despread signal signal to noise ratio and is adjusted in the step of parameter, when

The time, reduce p _nWhen The time, increase p _nWhen

And

During for maximum, think u " _i2(t), u " _q2(t) adjust to the best, p _nNumerical value is constant.

10. a receiver that improves satellite spectrum-spread communication despread signal signal to noise ratio, is characterized in that, described receiver comprises:

The input signal splitter, be used for obtaining input signal, and described input signal is divided into the equal described input signal of two-way, the described input signal in each road is QPSK modulation downstream signal, band spectrum modulation downstream signal and Gaussian noise sum, and wherein QPSK modulation downstream signal is far longer than the band spectrum modulation downstream signal;

Local oscillator, for generation of the required orthogonal local oscillation signal of demodulation, the carrier synchronization of local oscillator carrier wave and QPSK modulation downstream signal, local frequency equals the carrier frequency of QPSK modulation downstream signal, and the orthogonal local oscillation signal of local oscillator output multiplies each other with every road input signal respectively and exports I road difference frequency and frequency signal and Q road difference frequency and frequency signal;

The one QPSK Signal Matching filter, the 2nd QPSK Signal Matching filter, the I road, Q road and the frequency signal that are used for difference filtering described I road difference frequency and frequency signal and Q road difference frequency and frequency signal, export described I road, Q road difference frequency signal as I road, Q roadbed band signal, described I road, Q roadbed band signal are QPSK baseband signal, spread baseband signal and Gaussian noise sum, and wherein the amplitude of QPSK baseband signal is far longer than spread baseband signal;

Qpsk demodulator is used for exporting respectively I road, Q road QPSK demodulating data according to described I road, Q roadbed band signal;

The 3rd QPSK matched filter, the 4th QPSK matched filter are used for respectively the baseband signal of regenerating according to described I road, QPSK demodulating data output I road, Q road, Q road QPSK;

Amplitude adjusting circuit, be used for adjusting first, second, and third pair of QPSK base band reproducing signals of parameter output according to described I road Q road QPSK regeneration baseband signal with first, second, and third amplitude, and with second pair of QPSK base band reproducing signals as the optimal compensation QPSK base band reproducing signals, first pair of QPSK base band reproducing signals is as overcompensation QPSK base band reproducing signals, and the 3rd pair of QPSK base band reproducing signals is as undercompensation QPSK base band reproducing signals;

The signal delay module is used for respectively described I road, Q roadbed band signal are fixed time-delay, and I road, Q roadbed band signal and QPSK base band reproducing signals after time-delay are complementary in time;

The signal cancellation module, after being used for delaying time, I road, the rear Q roadbed band signal of time-delay subtract each other with described first, second, and third pair of QPSK base band reproducing signals respectively, export first, second, and third pair of spread baseband signal;

The signal to noise ratio module is used for described first, second, and third pair of spread baseband signal carried out respectively despreading, and calculates and export first, second, and third despread signal signal to noise ratio;

Control logic circuit, be used for adjusting described first, second, and third amplitude according to described first, second, and third despread signal signal to noise ratio and adjust parameter, and control the signal to noise ratio module and adjust first, second, and third corresponding despread signal signal to noise ratio, until being maximum and the first and second despread signal signal to noise ratios, the second despread signal signal to noise ratio equates.

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