CN103117769B - 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 the satellite communication system shown in Fig. 1, s ₁(t) be the QPSK modulation upward signal of transmitter 1 transmitting, s ₂(t) be the band spectrum modulation upward signal of transmitter 2 transmittings.S ₁and s (t) 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) signal, after communication satellite coverage frequency translation, forms QPSK modulation downstream signal r ₁and band spectrum modulation downstream signal r (t) 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, the transmission of Q road, value is ± 1; h ₁(t-kT ₁) be the pulse shock response transmitting, its corresponding frequency response function is that rolloff-factor is α ₁square 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, the transmission of Q road, 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 _qand b (t) _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 transmitting, its corresponding frequency response function is for being α for rolloff-factor ₂square 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, wideband qpsk modulation signal can r ₁(t) be equivalent to 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.From formula 4, in order to improve r ₂(t) signal to noise ratio after despreading, can increase k, r ₂, or reduce r (t) 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; When receiving system noise factor, determine, n (t) is determined value, cannot arbitrarily reduce; If can find a kind of method, not changing under the condition of existing parameter, reduce r ₁(t) impact, just can improve r ₂(t) signal to noise ratio after despreading.

Summary of the invention

The object 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 with QPSK base band reproducing signals, offset the QPSK baseband signal component in 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, described in each road, input signal is QPSK modulation downstream signal, band spectrum modulation downstream signal and Gaussian noise sum, and wherein QPSK modulation downstream signal is far longer than 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 is multiply each other output I road difference frequency and signal and Q road difference frequency and frequently signal frequently of Yu Mei road input signal respectively;

I road, Q road and frequency signal described in the one QPSK Signal Matching filter of described receiver, the 2nd QPSK Signal Matching filter difference filtering in 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, Q road QPSK demodulating data output I 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 using 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 matched in time;

One signal cancellation module of described receiver is subtracted each other Q roadbed band signal after I road, time delay after time delay respectively respectively with described first, second, and third pair of QPSK base band reproducing signals, 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 output 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 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, Q road QPSK demodulating data output I road, Q road QPSK regeneration baseband signal respectively:

One channel error correcting deocder of described receiver will encode to generate I road, Q road coded data again after 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 than demodulating data, there is the lower error rate (conventionally will be low 3 above orders of magnitude), by the regeneration baseband signal of its generation, there is less distortion.

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 ₁for QPSK modulation downstream signal, r ₂for 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, the transmission of Q road, 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 ₁square 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, the transmission of Q road, 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 _qand b (t) _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 for being α for rolloff-factor ₂square 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' _ikfor I road QPSK demodulating data, a' _qkfor 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 ₁>p ₂>p ₃, p ₁-p ₂=p ₂-p ₃=Δ, described control logic circuit, according to the signal to noise ratio after 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, the formula of described signal to noise ratio module calculating and output first, second, and third despread signal signal to noise ratio is as follows:

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 _iand m (t) _q(t) carry out mould two and add computing generation, S _{despreading n}for despread signal energy, N _{despreading n}for despread signal noise energy, when local I road, Q road frequency expansion sequence are synchronizeed with 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 time, reduce p _n; When time, increase p _n; When 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:

Input signal splitter, be used for obtaining input signal, and described input signal is divided into the equal described input signal of two-way, described in each road, input signal is QPSK modulation downstream signal, band spectrum modulation downstream signal and Gaussian noise sum, and wherein QPSK modulation downstream signal is far longer than 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 is multiply each other output I road difference frequency and signal and Q road difference frequency and frequently signal frequently of Yu Mei road input signal respectively;

The one QPSK Signal Matching filter, the 2nd QPSK Signal Matching filter, I road, Q road and frequency signal for I road difference frequency described in difference filtering 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, 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, for respectively according to described I road, Q road QPSK demodulating data output I road, the Q road QPSK baseband signal of regenerating;

Amplitude adjusting circuit, 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 using 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;

Signal delay module, for respectively described I road, Q roadbed band signal being fixed to time delay, matches I road, Q roadbed band signal and QPSK base band reproducing signals after time delay in time;

Signal cancellation module, for Q roadbed band signal after I road, time delay after time delay is subtracted each other with described first, second, and third pair of QPSK base band reproducing signals respectively, exports first, second, and third pair of spread baseband signal;

Signal to noise ratio module, for described first, second, and third pair of spread baseband signal carried out respectively to despreading, and calculates and output first, second, and third despread signal signal to noise ratio;

Control logic circuit, for adjust described first, second, and third amplitude according to described first, second, and third despread signal signal to noise ratio, adjust parameter, and control 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, for will encode to generate I road, Q road coded data again after described I road, Q road QPSK demodulating data error-correcting decoding, described the 3rd QPSK matched filter, the 4th QPSK matched filter are for according to described I road, Q road coded data output I road, the Q road QPSK baseband signal of regenerating again 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 ₁for QPSK modulation downstream signal, r ₂for 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, the transmission of Q road, 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 ₁square 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, the transmission of Q road, 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 _qand b (t) _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 for being α for rolloff-factor ₂square 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 ₁for QPSK modulation downstream signal, r ₂for 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, the transmission of Q road, 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 ₁square 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, the transmission of Q road, 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 _qand b (t) _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 for being α for rolloff-factor ₂square 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' _ikfor I road QPSK demodulating data, a' _qkfor 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 ₁>p ₂>p ₃, p ₁-p ₂=p ₂-p ₃=Δ, described control logic circuit, according to the signal to noise ratio after 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, the formula of described signal to noise ratio module calculating and output first, second, and third despread signal signal to noise ratio is as follows:

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 _iand m (t) _q(t) carry out mould two and add computing generation, S _{despreading n}for despread signal energy, N _{despreading n}for despread signal noise energy, when local I road, Q road frequency expansion sequence are synchronizeed with 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 time, reduce p _n; When time, increase p _n; When and during for maximum, think u " _i2(t), u " _q2(t) adjust to the best, p _nnumerical value is constant.

In the QPSK large-signal that takies same frequency, same frequency band, cover under condition, 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; At spread-spectrum signal spreading gain, require, under constant condition, can reduce the transmitting power of spread spectrum transmitter, reduce the impact of spread-spectrum signal on QPSK signal, improve the disguise of spread-spectrum signal; After spread-spectrum signal despreading, signal to noise ratio requires, under constant condition, can reduce the spread spectrum coefficient of spread-spectrum signal, improves the transmission rate of spread spectrum communication system.

Accompanying drawing explanation

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 encoding 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, below in conjunction with the drawings and specific embodiments, the present invention is further detailed explanation.

Embodiment mono-

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 Figures 3 and 4, the basic principle of the present embodiment method is to produce QPSK base band reproducing signals by QPSK demodulating data, then with QPSK base band reproducing signals, offset the QPSK baseband signal component in baseband signal, thereby improve the Signal-to-Noise after 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, described in each road, input signal is QPSK modulation downstream signal, band spectrum modulation downstream signal and Gaussian noise sum, and wherein QPSK modulation downstream signal is far longer than 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 ₁for QPSK modulation downstream signal, r ₂for band spectrum modulation downstream signal, n (t) is Gaussian noise, according to the condition described in background technology, and modulated spread spectrum signal r ₂(t) amplitude is far smaller than qpsk modulation signal r ₁(t) amplitude (being conventionally 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, the transmission of Q road, 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 ₁square 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, the transmission of Q road, 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 _qand b (t) _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 for being α for rolloff-factor ₂square 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 is multiply each other output I road difference frequency and signal and Q road difference frequency and frequently signal frequently of Yu Mei road input signal respectively.Concrete, after the normal demodulation of qpsk modulation signal, under its carrier synchronization circuit is controlled, receiver local oscillator carrier wave is synchronizeed with QPSK signal carrier, receiver local frequency ω ₀equal to input qpsk modulation signal carrier frequency ω ₁.

Step S3, I road, Q road and frequency signal described in the one QPSK Signal Matching filter 3 of described receiver, the 2nd QPSK Signal Matching filter 4 difference filterings in 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 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, after the demodulation of QPSK signal, export I road QPSK demodulating data a' _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 transmitting with 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, Q road QPSK demodulating data output I road, Q road QPSK regeneration baseband signal u' _i(t), u' _q(t).

Concrete, QPSK demodulating data a' _ikand a' _qkinput 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 _iand u' (t) _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' _ikfor I road QPSK demodulating data, a' _qkfor 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 will encode to generate I road, Q road coded data again after 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) distortion, if QPSK signal data information a _ik, a _qkthrough error correction coding, process, can be by demodulating data a' _ik, a' _qkafter error-correcting decoding, encode again, produce coded data a again " _ik, a " _qk, then incite somebody to action coded data a again " _ikand a " _qkinput 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 _iand u' (t) _q(t) (see figure 5).Due to a' _ik, a' _qkcompare a " _ik, a " _qkthere is the lower error rate (conventionally will be low 3 above orders of magnitude), by a " _ik, a " _qkthe u' producing _i(t), u' _q(t) there is 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 using 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' _iand u' (t) _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 ₁>p ₂>p ₃, p ₁-p ₂=p ₂-p ₃=Δ, described control logic circuit, according to the signal to noise ratio after 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 tunnel is during in the optimal compensation, despreading signal to noise ratio reaches maximum; Now first pair 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, in order to differentiate, whether reaches the optimal compensation.

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 matched 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) represent.

Step S8, a signal cancellation module 10 of described receiver is subtracted each other Q roadbed band signal after I road, time delay after time delay respectively respectively with described first, second, and third pair of QPSK base band reproducing signals, 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 output first, second, and third despread signal signal to noise ratio.

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

(formula 12)

As QPSK base band reproducing signals u " _in(t) and u " _qn(t) while mating with QPSK baseband signal completely, Δ u _fin(t), Δ u _qn(t) become and zero, the signal to noise ratio after spread-spectrum signal despreading is represented by formula 13:

(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 of usual manner band spread receiver despread signal suc as formula 4, 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 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 _inand Q road spread baseband signal y (t) _qn(t) respectively with the local frequency expansion sequence m on modulated spread spectrum signal I road, Q road _iand m (t) _q(t) carry out mould two and add computing generation; S _{despreading n}for despread signal energy, N _{despreading n}for despread signal noise energy; When local I road, Q road frequency expansion sequence are synchronizeed with 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, 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 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).According to formula 14, formula 15, formula 16, calculate spread baseband signal y _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}change amplitude is adjusted parameter p _nthe numerical value of (n=1,2,3) (flow process is as shown in Figure 7): when time, reduce p _n; When time, increase p _n; When 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 tunnel is during in the optimal compensation, despreading signal to noise ratio reaches maximum; Now the 1st tunnel is overcompensation, its despreading signal to noise ratio little with the second tunnel; The 3rd tunnel is undercompensation, and its despreading signal to noise ratio is also less than the second tunnel; First, second, and third despread signal signal to noise ratio forms a peak, in order to differentiate, whether reaches the optimal compensation.

Shown in Fig. 8 and Fig. 9 is qpsk modulation signal Amplitude Ratio modulated spread spectrum signal amplitude high 20 times (the high 26dB of power), and spread spectrum coefficient is 127, and snr of received signal is under 20dB condition, the simulation result of the signal to noise ratio after 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 spread-spectrum signal despreading, and the white surface area in figure in the latter half is noise, the method of visible employing the present embodiment, spread-spectrum signal signal to noise ratio has improvement more than 10dB.

In the satellite communication system shown in Fig. 1, adopt the method for the present embodiment, with the same transmission conditions of usual manner under, can improve the signal to noise ratio after spread-spectrum signal despreading, improve the transmission quality of spread spectrum communication; At spread-spectrum signal spreading gain, require, under constant condition, can reduce the transmitting power of spread spectrum transmitter, reduce the impact of spread-spectrum signal on QPSK signal, improve the disguise of spread-spectrum signal; After spread-spectrum signal despreading, signal to noise ratio requires, under constant condition, can reduce the spread spectrum coefficient of spread-spectrum signal, improves the transmission rate of spread spectrum communication system.

Embodiment bis-

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 comprises 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 for obtaining input signal, and described input signal is divided into the equal described input signal of two-way, described in each road, input signal is QPSK modulation downstream signal, band spectrum modulation downstream signal and Gaussian noise sum, and wherein QPSK modulation downstream signal is far longer than 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 ₁for QPSK modulation downstream signal, r ₂for band spectrum modulation downstream signal, n (t) is Gaussian noise, according to the condition described in background technology, and modulated spread spectrum signal r ₂(t) amplitude is far smaller than qpsk modulation signal r ₁(t) amplitude (being conventionally 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, the transmission of Q road, 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 ₁square 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, the transmission of Q road, 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 _qand b (t) _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 for being α for rolloff-factor ₂square 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 is multiply each other output I road difference frequency and signal and Q road difference frequency and frequently signal frequently of Yu Mei road input signal respectively.Concrete, after the normal demodulation of qpsk modulation signal, under its carrier synchronization circuit is controlled, receiver local oscillator carrier wave is synchronizeed with QPSK signal carrier, 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, for I road, Q road and the frequency signal of I road difference frequency described in difference filtering 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 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 for exporting respectively I road, Q road QPSK demodulating data a' according to described I road, Q roadbed band signal _ik,, a' _qk.

Concrete, after the demodulation of QPSK signal, export I road QPSK demodulating data a' _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 transmitting with QPSK signal _ikand a _qkidentical.

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

Concrete, QPSK demodulating data a' _ikand a' _qkinput 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 _iand u' (t) _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' _ikfor I road QPSK demodulating data, a' _qkfor 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 also comprises that a channel error correcting deocder 13 is for encoding to generate I road, Q road coded data again after described I road, Q road QPSK demodulating data error-correcting decoding 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) distortion, if QPSK signal data information a _ik, a _qkthrough error correction coding, process, can be by demodulating data a' _ik, a' _qkafter error-correcting decoding, encode again, produce coded data a again " _ik, a " _qk, then incite somebody to action coded data a again " _ikand a " _qkinput 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 _iand u' (t) _q(t) (see figure 5).Due to a' _ik, a' _qkcompare a " _ik, a " _qkthere is the lower error rate (conventionally will be low 3 above orders of magnitude), by a " _ik, a " _qkthe u' producing _i(t), u' _q(t) there is 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 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 using 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' _iand u' (t) _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 ₁>p ₂>p ₃, p ₁-p ₂=p ₂-p ₃=Δ, described control logic circuit, according to the signal to noise ratio after 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 tunnel is during in the optimal compensation, despreading signal to noise ratio reaches maximum; Now first pair 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, in order to differentiate, whether reaches the optimal compensation.

Signal delay module 9, for respectively described I road, Q roadbed band signal being fixed to time delay, matches I road, Q roadbed band signal and QPSK base band reproducing signals after time delay 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) represent.

Signal cancellation module 10, for Q roadbed band signal after I road, time delay after time delay is subtracted each other with described first, second, and third pair of QPSK base band reproducing signals respectively, is exported 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 for described first, second, and third pair of spread baseband signal carried out respectively to despreading, and calculating and output first, second, and third despread signal signal to noise ratio.

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

(formula 12)

As QPSK base band reproducing signals u " _in(t) and u " _qn(t) while mating with QPSK baseband signal completely, Δ u _in(t), Δ u _qn(t) become and zero, the signal to noise ratio after spread-spectrum signal despreading is represented by formula 13:

(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 of usual manner band spread receiver despread signal suc as formula 4,

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 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 _inand Q road spread baseband signal y (t) _qn(t) respectively with the local frequency expansion sequence m on modulated spread spectrum signal I road, Q road _iand m (t) _q(t) carry out mould two and add computing generation; S _{despreading n}for despread signal energy, N _{despreading n}for despread signal noise energy; When local I road, Q road frequency expansion sequence are synchronizeed with 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, 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 adjusted parameter for adjust described first, second, and third amplitude according to described first, second, and third despread signal signal to noise ratio, and control 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).According to formula 14, formula 15, formula 16, calculate spread baseband signal y _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}change amplitude is adjusted parameter p _nthe numerical value of (n=1,2,3) (flow process is as shown in Figure 7): when time, reduce p _n; When time, increase p _n; When 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 tunnel is during in the optimal compensation, despreading signal to noise ratio reaches maximum; Now the 1st tunnel is overcompensation, its despreading signal to noise ratio little with the second tunnel; The 3rd tunnel is undercompensation, and its despreading signal to noise ratio is also less than the second tunnel; First, second, and third despread signal signal to noise ratio forms a peak, in order to differentiate, whether reaches the optimal compensation.

Shown in Fig. 8 and Fig. 9 is qpsk modulation signal Amplitude Ratio modulated spread spectrum signal amplitude high 20 times (the high 26dB of power), and spread spectrum coefficient is 127, and snr of received signal is under 20dB condition, the simulation result of the signal to noise ratio after 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 spread-spectrum signal despreading, and the white surface area in figure in the latter half is noise, the method of visible employing the present embodiment, spread-spectrum signal signal to noise ratio has improvement more than 10dB.

In the satellite communication system shown in Fig. 1, adopt the method for the present embodiment, with the same transmission conditions of usual manner under, can improve the signal to noise ratio after spread-spectrum signal despreading, improve the transmission quality of spread spectrum communication; At spread-spectrum signal spreading gain, require, under constant condition, can reduce the transmitting power of spread spectrum transmitter, reduce the impact of spread-spectrum signal on QPSK signal, improve the disguise of spread-spectrum signal; After spread-spectrum signal despreading, signal to noise ratio requires, under constant condition, can reduce the spread spectrum coefficient of spread-spectrum signal, improves the transmission rate of spread spectrum communication system.

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 the combination of the two, for the interchangeability of hardware and software is clearly described, composition and the step of each example described according to function in the above description in general manner.These functions are carried out with hardware or software mode actually, depend on application-specific and the design constraint of technical scheme.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 depart from the spirit and scope of the present invention invention.Like this, if within of the present invention these are revised and modification belongs to the scope of the claims in the present invention and equivalent technologies thereof, the present invention is also 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 input signal that two-way is equal, described in each road, input signal is QPSK modulation downstream signal, band spectrum modulation downstream signal and Gaussian noise sum, and wherein QPSK modulation downstream signal is greater than 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 is multiply each other output I road difference frequency and signal and Q road difference frequency and frequently signal frequently of Yu Mei road input signal respectively;

I road, Q road and frequency signal described in the one QPSK Signal Matching filter of described receiver, the 2nd QPSK Signal Matching filter difference filtering in 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 greater 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, Q road QPSK demodulating data output I 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 using 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 matched in time;

One signal cancellation module of described receiver is subtracted each other Q roadbed band signal after I road, time delay after time delay respectively respectively with described first, second, and third pair of QPSK base band reproducing signals, 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 output 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 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, Q road QPSK demodulating data output I road, Q road QPSK regeneration baseband signal respectively:

One channel error correcting deocder of described receiver will encode to generate I road, Q road coded data again after 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:

$\begin{array}{c}r\left(t\right)=A\left\{\right[\underset{k=-\∞}{\overset{+\∞}{\mathrm{\Σ}}}{a}_{\mathrm{Ik}}{h}_1(t-{\mathrm{kT}}_1)]\cos \left({\mathrm{\ω}}_{1}t\right)+[\underset{k=-\∞}{\overset{+\∞}{\mathrm{\Σ}}}{a}_{\mathrm{Qk}}{h}_1(t-{\mathrm{kT}}_1)\left]\sin \left({\mathrm{\ω}}_{1}t\right)\right\}\\ +B\left\{\right[\underset{k=-\∞}{\overset{+\∞}{\mathrm{\Σ}}}{b}_{\mathrm{Ik}}\left(t\right)m_i\left(t\right)h_2(t-{\mathrm{kT}}_2)]\cos \left({\mathrm{\ω}}_{2}t\right)+[\underset{k=-\∞}{\overset{+\∞}{\mathrm{\Σ}}}{b}_{\mathrm{Qk}}\left(t\right)m_q\left(t\right)h_2(t-{\mathrm{kT}}_2)\left]\sin \left({\mathrm{\ω}}_{2}t\right)\right\}\\ +n\left(t\right)\\ =r_1\left(t\right)+r_2\left(t\right)+n\left(t\right)\end{array}$

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

R ₁formula as follows:

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

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, the transmission of Q road, 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 ₁square 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:

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

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, the transmission of Q road, 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 greater than b _ik, b _qkspeed, m _i(t), m _qand b (t) _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 for being α for rolloff-factor ₂square 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:

$\begin{array}{c}{x}_i\left(t\right)=A^{\′}\underset{k=-\∞}{\overset{+\∞}{\mathrm{\Σ}}}{a}_{\mathrm{Ik}}{h}_1(t-{\mathrm{kT}}_1)\\ +B^{\′}\left\{\right[\underset{k=-\∞}{\overset{+\∞}{\mathrm{\Σ}}}{b}_{\mathrm{Ik}}\left(t\right)m_i\left(t\right)h_2(t-{\mathrm{kT}}_2)]\cos ({\mathrm{\ω}}_2-{\mathrm{\ω}}_{1}t)+[\underset{k=-\∞}{\overset{+\∞}{\mathrm{\Σ}}}{b}_{\mathrm{Qk}}\left(t\right)m_q\left(t\right)h_2(t-{\mathrm{kT}}_2)\left]\sin ({\mathrm{\ω}}_2-{\mathrm{\ω}}_{1}t)\right\}\\ +n_i\left(t\right)\\ =u_i\left(t\right)+v_i\left(t\right)+n_i\left(t\right)\end{array}$

The formula of Q roadbed band signal is as follows:

$\begin{array}{c}{x}_q\left(t\right)=A^{\′}\underset{k=-\∞}{\overset{+\∞}{\mathrm{\Σ}}}{a}_{\mathrm{Qk}}{h}_1(t-{\mathrm{kT}}_1)\\ +B^{\′}\left\{\right[\underset{k=-\∞}{\overset{+\∞}{\mathrm{\Σ}}}{b}_{\mathrm{Qk}}\left(t\right)m_q\left(t\right)h_2(t-{\mathrm{kT}}_2)]\cos ({\mathrm{\ω}}_2-{\mathrm{\ω}}_{1}t)+[\underset{k=-\∞}{\overset{+\∞}{\mathrm{\Σ}}}{b}_{\mathrm{Ik}}\left(t\right)m_i\left(t\right)h_2(t-{\mathrm{kT}}_2)\left]\sin ({\mathrm{\ω}}_2-{\mathrm{\ω}}_{1}t)\right\}\\ +n_q\left(t\right)\\ =u_q\left(t\right)+v_q\left(t\right)+n_q\left(t\right)\end{array},$

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 greater 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 ₂equate 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 ' _ikfor I road QPSK demodulating data, a ' _qkfor 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 ₁>p ₂>p ₃, p ₁-p ₂=p ₂-p ₃=Δ, described control logic circuit, according to the signal to noise ratio after 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:

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

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, the formula of described signal to noise ratio module calculating and output first, second, and third despread signal signal to noise ratio is as follows:

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 _iand m (t) _q(t) carry out mould two and add computing generation, S _{despreading n}for despread signal energy, N _{despreading n}for despread signal noise energy, when local I road, Q road frequency expansion sequence are synchronizeed with 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 time, reduce p _n; When time, increase p _n; When 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:

Input signal splitter, be used for obtaining input signal, and described input signal is divided into the input signal that two-way is equal, described in each road, input signal is QPSK modulation downstream signal, band spectrum modulation downstream signal and Gaussian noise sum, and wherein QPSK modulation downstream signal is greater than 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 is multiply each other output I road difference frequency and signal and Q road difference frequency and frequently signal frequently of Yu Mei road input signal respectively;

The one QPSK Signal Matching filter, the 2nd QPSK Signal Matching filter, I road, Q road and frequency signal for I road difference frequency described in difference filtering 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 greater than spread baseband signal;

Qpsk demodulator, 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, for respectively according to described I road, Q road QPSK demodulating data output I road, the Q road QPSK baseband signal of regenerating;

Amplitude adjusting circuit, 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 using 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;

Signal delay module, for respectively described I road, Q roadbed band signal being fixed to time delay, matches I road, Q roadbed band signal and QPSK base band reproducing signals after time delay in time;

Signal cancellation module, for Q roadbed band signal after I road, time delay after time delay is subtracted each other with described first, second, and third pair of QPSK base band reproducing signals respectively, exports first, second, and third pair of spread baseband signal;

Signal to noise ratio module, for described first, second, and third pair of spread baseband signal carried out respectively to despreading, and calculates and output first, second, and third despread signal signal to noise ratio;

Control logic circuit, for adjust described first, second, and third amplitude according to described first, second, and third despread signal signal to noise ratio, adjust parameter, and control 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.