SU370732A1 - PAT: - Google Patents

Description

one

The invention relates to a pseudo-noise signal search device based on a delay and can be used in radio systems whose modulating signal changes according to the pseudo-random sequence law.

Known devices for searching for a pseudo-random signal by delay, containing a collector, whose inputs are connected respectively to the device input and to the output of the reference generator, and the output is connected via a threshold circuit to the control input of a switch connected between the output of the additional generator and the reference generator, and the reference output the generator through the decoder-driver and the prohibition circuit is connected to the second control input of the switch, and the second input of the prohibition circuit is connected to the output have a long search time.

The purpose of the invention is to create such a search engine CBS, which will significantly reduce the average search time.

This is achieved by performing a preliminary coarse search. In the proposed device, the average search time can be reduced by decreasing the number of resolution elements to be correlated in the first search stage, for which

increase the width of the main peak of the autocorrelation function of the signal.

The drawing shows the block diagram of the proposed device search SRP but the delay.

The device contains; reference generator 1; discriminator 2 additional generator 3; switch 4; decoder-shaper 5; scheme 6 of the ban; 7 bottom filter

frequencies; correl tor 8; threshold scheme 9.

The device works in two rela “1m; Coarse search and accurate search.

In the coarse search mode, the signal at the output of the threshold circuit 9 is absent, and the switch 4 is in the state where the signal from the output of the inhibitor circuit 6 is input to the on-off generator. The state of the switch 4 is determined by the presence or absence of voltage at the output of the threshold circuit 9. If there is no voltage at the output of the threshold circuit 9, then the switch 4 connects the output of the inhibit circuit 6 to the input of the reference generator /; if the voltage is present, then through the switch 4 the output of the auxiliary generator 3 is connected to the input of the on / off generator. From the decoder-former 5 pulses, pulses with a period equal to the SRP period and a pre-selected duration arrive at the input of circuit 6;

where Go is the period of the clock frequency of the additional generator 3. The pulses at the output of the decoder-generator 5 do not transmit to the output of the prohibition circuit 6 those clock pulses from the output of the additional generator 3 that overlap in time with the pulses at the output of the decoder-generator 5. As a result, a coarse search to the input of the reference generator / part of the clock pulses is not applied, which leads to a shift of the reference sequence relative to the PTo received at the time, where P a- | To is an integer from dividing lu by Go. Input sequence that passes through the low pass filter 7. At the time of the coincidence of the time position and the received memory bandwidth, the output of the correlator 8 is voltage, repeated, its shape is the envelope of the mutual correlation function between the received memory bandwidth and the reference band that passed through the low pass filter 7. The width of this function is determined by the bandwidth of the lowpass filter and the larger, the smaller the filter band 7.

By choosing the filter width, you can determine in advance the number of resolution elements analyzed in the coarse search mode. This number is

P. ,

where G is the PSP period;

Tft is the voltage correlation time at the output of the correlator 8.

When voltage is detected at the output of the correlator 8 and the threshold circuit 9, the switch 4 switches off the output of the inhibit circuit 6 from the generator / reference SRP input and switches the output of the additional generator 3 to the input of this generator. The follower correlator ring, which includes the reference generator / , the discriminator 2 and the additional generator 3, closes and the device switches to the exact search mode.

In the exact additional search mode, due to the inequality of the clock frequencies, the baseline bandwidth slip relative to the received bandwidth and the correlation control of the baseline bandwidth and received bandwidth is observed using a known tracking correlator. At some point in time, the system goes into synchronism and the search process ends.

The search time in the device in the absence of noise is the sum of the search time at the first stage and the search time at the second stage. This time is

Gponska - 7n + Gp (t + / OT ".

Who

Where

 - to- t -, A - -,

%about

H is the signal accumulation time.

Subject invention

The device for searching for a pseudo-random signal by delay, containing a correlator whose inputs are connected respectively to the input of the device and to the output of the reference generator, and the output through the threshold circuit is connected

with the control input of the switch connected between the output of the additional generator and the input of the reference generator, the output of the reference generator through the decoder-driver and the inhibitor circuit is connected to the second control input of the switch, and the second input of the inhibitor circuit is connected to the output of the additional generator differing in that, in order to reduce the search time, a discriminator is switched on between the input of the device and the additional generator, the reference input of which is connected to the reference generator, and between the reference m generator and correlator included lowpass filter.