RU1840950C - Receiving device - Google Patents

Abstract

FIELD: physics, navigation.

SUBSTANCE: invention relates to radar engineering. The result is achieved due to that the receiving device includes series-connected intermediate frequency amplifier with a limiter, a first amplitude detector, a comparator and a coincidence unit, as well as a unit for estimating the centre of gravity of signals, connected between the output of the first amplitude detector and the second input of the coincidence unit. The device also includes, connected in series between the input of the device and the inverting input of the coincidence unit, a second amplitude detector, an amplitude-time quantiser, a detector for detecting the beginning and end of pulses, a counter and a digital comparator.

EFFECT: high sensitivity and noise-immunity.

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Description

The present invention relates to the field of radar. It can be used in pulsed radar detection to highlight the echo signals of the circuits under the influence of pulsed and noise interference.

A device for amplitude-frequency selection of echo signals [1], consisting of series-connected broadband amplifier, amplitude limiter and matched with the band of echo signals of the amplifier (SHOW scheme).

Such a device provides protection only from impulse noise, the duration of which is much shorter than the duration of the echo signals.

It is also known a device for temporary pulse selection [1], which contains a series-connected delay line, a differentiating cascade and a limiter. The signal at the output of the device appears only if the duration of the received pulses is equal to the delay time in the line.

However, such a temporary selection device is effective only for rectangular pulses with short edges and an amplitude greater than the average noise level in the receiver. Therefore, the passband of the receiving device preceding the temporary selection device and the delay line should be several times wider than the optimal one. This leads to a decrease in the sensitivity of the receiving device, and also increases the complexity of manufacturing a delay line, especially with pulse durations of tens of microseconds or more.

Of the known devices, the closest in technical essence to the claimed invention is a receiving device [2], containing a series-connected broadband amplifier of intermediate frequency, an amplitude detector, a comparator, a broadband delay line for the duration of the pulse signal and the coincidence circuit, as well as a circuit for estimating the center of gravity of the pulse signals the input of which is connected to the output of the amplitude detector, and the outputs of the center of gravity estimation circuit and the comparator are connected to the corresponding inputs of the circuits s matches.

Such a device, while protecting against impulse noise, has the following disadvantages:

1. The inconsistency of the passband of the broadband amplifier of the intermediate frequency with the frequency spectrum of the pulse signal leads to a decrease in the sensitivity of the receiving device.

2. Lack of protection against extended (ie duration longer than a pulse signal) interference.

3. The use of a broadband delay line for the duration of the signal.

The purpose of the invention is to increase the sensitivity and noise immunity of the receiving device of pulsed signals against the background of pulsed and noise interference, which differ from the signals in duration.

This goal is achieved by the fact that in a receiving device containing a first amplitude detector, a comparator, a matching circuit, as well as a circuit for fixing the center of gravity of the pulse signals, the input of which is connected to the output of the first amplitude detector, and the output is connected to the corresponding input of the matching circuit, are introduced an intermediate frequency amplifier with a limiter, the passband of which is consistent with the frequency band of the pulse signal, the input of the intermediate frequency amplifier is connected to the input of device, and the output is connected to the input of the first amplitude detector, as well as a second amplitude detector, an amplitude-time quantizer, a start and end pulse detector, a counter and a digital comparator, the input of the second amplitude detector is connected to the input of an intermediate frequency amplifier with a limiter, and the output of the digital comparator is connected to the corresponding input of the matching circuit.

The inclusion of an intermediate frequency amplifier with a limiter in the receiver, made according to the SHO scheme, allows, firstly, to carry out a coordinated filtering of pulsed signals and to provide the highest possible sensitivity, and secondly, to suppress pulsed noise if their duration is much shorter than the signal duration, due to the amplitude limit in a wide (compared to the signal band) frequency band and the subsequent frequency limit in a narrow-band filter matched with the signal.

The connection of a second amplitude detector, an amplitude-time quantizer, a start and end detector of pulses, a counter and a digital comparator, which together constitute a digital pulse selector, in parallel with the main receiving channel, makes it possible to carry out protection against impulse noise without affecting the sensitivity of the receiving device and use Broadband delay line for signal duration.

The electrical functional diagram of the inventive receiving device is shown in the drawing.

Parallel to the main receiving channel, which contains an intermediate frequency amplifier 1 with a limiter, a first amplitude detector 2, a comparator 3, a center of gravity estimation circuit 4, and a coincidence circuit 5, a digital duration selector is included, consisting of a second amplitude detector 6 connected in series, an amplitude-time converter 7, a detector 8 of the beginning and end of pulses, a counter 9 and a digital comparator 10.

The digital selector operates as follows.

The radio frequency voltage supplied to the input of the device is detected by the second amplitude detector 6, and the envelope of this voltage in the time-amplitude quantizer 7 is converted into a sequence of standard video pulses (ie, video pulses with an amplitude equal to the logic level “1”). The specified sequence is fed to the input of the detector 8 of the beginning and end of the pulses, operating by the static criterion K / M-N "0" in a row [3]. When the start detection criterion is met, the detector 8 generates a sequence of standard pulses and feeds them to counter 9 to count their number L. At the end of the end detection criterion, the binary code of the number L is read from counter 9 to comparator 10, and counter 9 is set to zero. In the comparator 10, the number L is compared by the code inequality with the constant values (A + 1) and (A-1), where the number A is the integer part of the ratio Tc / Td, and Tc and Td are the duration of the pulse signal and the repetition period of standard pulses, respectively .

In case the condition is satisfied

$$0<L<A-\mathrm{one}\text{v L}>\text{A}+\text{one}\text{, (one)}$$

a standard pulse is supplied to the inverted input of the coincidence circuit 5, to which the output of the comparator 10 is connected. This pulse prevents the occurrence at the output of circuit 5 of coincidence, which is the output of the receiving device, logical "1" even if there are logical "1" on the other two inputs from the outputs of circuit 4 and comparator 3.

Condition (1) is not satisfied in two cases: if the duration of the radio pulse at the input of the receiving device is close to the value of Tс (i.e., the condition A-1≤L≤A + 1 is true), or if the pulse is not detected by the digital selector (L = 0 )

The first of these cases corresponds to the detection of a pulse signal, both in the signal receiving channel and in the digital selector.

The second case is typical when receiving weak signals with a duration close to Tc. Since the sensitivity of the digital selector due to the lack of matching in the band of the received frequencies is lower than in the reception channel, signal detection in this case may not occur in the selector, which, however, does not affect reception of pulsed noise, since they usually have a large amplitude.

Thus, the failure of condition (1) indicates the absence of powerful pulsed noise at the input of the receiving device, which differs from the pulse signal in duration.

The suppression of pulsed interference of MTD duration and shorter is carried out by an intermediate frequency amplifier 1 with a limiter made according to the SHOW scheme. The coordination of the bandwidth of the amplifier 1 with the spectrum of the signal allows to increase the sensitivity of the proposed receiving device in comparison with the prototype.

The use of static criteria in the detector 8 of the beginning and end of pulses makes it possible to protect against intermittent pulsed noise generated by the combined action of pulsed and noise interference on the receiving device.

Increasing the sensitivity and noise immunity of the receiving device when using it, for example, in a pulsed radar, can significantly increase its throughput or obtain an economic effect by reducing the volume and complexity of the equipment.

The proposed receiving device can also be used in pulse-code communication lines to increase noise immunity and their range.

Information sources

1. Bobnev M.P. etc. Protection against interference. M., "Soviet Radio", 1976.

2. Likharev V.A. Digital methods and devices in radar. M., "Soviet Radio", 1973.

3. Klyuev N.F. Discrete action detection. M., "Soviet Radio", 1963.

Claims (1)

A receiving device comprising a series-connected intermediate frequency amplifier with a limiter, a first amplitude detector, a comparator and a coincidence unit, as well as a signal center of gravity estimation unit connected between the output of the first amplitude detector and another input of the coincidence unit, characterized in that, in order to increase the sensitivity and noise immunity, introduced in series connected between the input of the device and the inverse input of the coincidence unit is a second amplitude detector, amplitude-time quantum detector, pulse start and end detector, counter and digital comparator.

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