RU1840893C - Superheterodyne pulsed signal receiver with frequency search - Google Patents

Abstract

FIELD: radio engineering, communication.

SUBSTANCE: receiver has series-connected logic device, units for measuring signal carrier frequency and heterodyne frequency, heterodyne, mixer, intermediate frequency amplifier, detector, buffer register and storage device, wherein the intermediate frequency amplifier is single-channel and has filters tuned to different frequencies. The receiver also includes a filter number comparing unit connected between the output of the storage device and the input of the logic device.

EFFECT: high probability of unique automatic determination of carrier frequency.

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Description

The proposed device for automatically determining the carrier frequency value of pulse signals for a superheterodyne receiver (GHP) belongs to the field of radio engineering and can be used in radio engineering installations (for example, in radio intelligence stations).

As a rule, the carrier frequency of the received pulse signals is determined by measuring the frequency of the local oscillator of the superheterodyne receiver, which is tunable in frequency, taking into account the frequency shift of the local oscillator by the value of the intermediate frequency.

The composition of the SHP includes a device that measures the frequency of the local oscillator, and a device in which the frequency is converted into a form convenient for further use (for example, in binary code).

Since the intermediate frequency can be formed both in the direct and in the mirror channels, difficulties arise associated with determining the direction of the frequency shift of the local oscillator.

Typically, tunable filters are used in the CST to suppress reception on one of the channels (direct or mirror), which complicates the equipment. In addition, this reduces the likelihood of detecting signals (when receiving fluctuating signals) compared to receivers that receive signals through the direct and mirror channels, since in the latter the reception of each part of the range at the same search time is carried out twice as often.

The closest in technical essence is a device in which automatic measurement of the frequency of pulse signals when receiving both direct and mirror channels is performed as a result of processing all pulses received during one search cycle in frequency by adding (subtracting) the automatically generated signal of the intermediate value frequencies from the measured local oscillator frequency depending on the received channel.

полосы пропускания УПЧ 1), два детектора, и устройство анализа зеркальной частоты (анализирующее устройство), состоящее из узла формирования, буферного регистра, запоминающего устройства, узла управления, узла обработки, узел измерения частоты гетеродина и узел измерения частоты сигнала.The device contains a CST, including a local oscillator, a mixer, a PCB, two amplifiers of intermediate frequency, the frequency characteristics of which are shifted in frequency and have a different bandwidth (bandwidth $$P=\frac{\mathrm{one}}{2}$$

bandwidth UPCH 1), two detectors, and a mirror frequency analysis device (analyzing device), consisting of a forming unit, a buffer register, a storage device, a control unit, a processing unit, a local oscillator frequency measuring unit, and a signal frequency measuring unit.

The formation node includes a signal normalization circuit in terms of amplitude and duration and a coincidence circuit.

The processing unit includes an adder, a counter, a match circuit, and an analysis circuit (logical device).

If there are signals at the outputs of both IFs at the same time, a signal "1" is generated in the device for analyzing the mirror frequency; in the presence of signals at the output of only one amplifier - signal "0".

As a result of the operation of the device, sequences consisting of zeros and ones arise, and the sequence 11110000 corresponds to the mirror channel, 00001111 corresponds to the direct channel.

The logic device counts and compares the number of units in the right and left parts of the sequences and gives a signal at the first output if units prevail in the right half of the sequence, which corresponds to reception on the direct channel, and on the second output, otherwise.

In the node of measuring the frequency of the signal, the value of the intermediate frequency is added (subtracted) to the measured value of the local oscillator frequency.

The disadvantages of this device include the presence of an additional intermediate frequency amplifier and additional nodes in the device for analyzing the mirror frequency, designed to increase the noise immunity of the system, which complicates the equipment. The introduction of an additional amplifier and the adopted processing scheme requires strict coordination of the beginnings of the passbands of two amplifiers of intermediate frequency, which complicates the setup of the device.

The aim of this invention is to increase the likelihood of unambiguous automatic determination of the carrier frequency value from a sequence of selected signals received both through direct and mirror channels in one tuning cycle of a superheterodyne receiver, simplification of the device, simplification of tuning technology.

This goal is achieved in that in this device for automatically determining the carrier frequency of pulse signals for a superheterodyne receiver containing a storage device, to the inputs of which a buffer register and a control unit are connected, the second input of the latter is connected to a processing circuit including a logic device and having two outputs, the values of the carrier frequency of the signal connected to the measurement node, which, in turn, is connected to the local oscillator oscilloscope in the processing circuit to the input of the logic device A node has been connected for comparing the filter numbers of the UHF filters of the superheterodyne receiver through which the CGS signals are received, and the sequence of the signal passing through the filters determines the reception channel (decreasing when receiving through the direct channel, increasing - when receiving via the mirror channel).

Figure 1 shows a block diagram of the proposed device.

Detailed description

The proposed device for automatically determining the carrier frequency value of pulse signals for a superheterodyne receiver (SHP) containing a local oscillator (1), a mixer (2), an intermediate frequency preamplifier (PCA) (3), an intermediate frequency amplifier (OPC) (4), a detector ( 5), the local oscillator frequency measuring unit (6) and the signal carrier frequency measuring unit (7), consists of a buffer register (8), a memory device (9), a control unit (10), a processing circuit (11) with two outputs, including series-connected node comp Nia IF filters EGR room (12) and a logic device (13).

When searching for signals in a given range, the local oscillator frequency changes according to a sawtooth law. In the presence of pulse signals in the tuning range of the local oscillator (1), signals appear at the output of the amplifier (4). The bandwidth of the IF (4) is 50 MHz and is filtered into 5 bands of 10 MHz each (to increase the resolution on the carrier frequency). Each range is assigned a number (feature).

At the input of the buffer register (8), a pulse sequence of signals (packets) is received, one of the characteristics of which is the range number assigned to each signal.

The number of pulses in a packet depends on the ratio of the local oscillation tuning speed and on the pulse repetition rate.

In the proposed device, this ratio is chosen such that at the output of the drive (4), at least three pulses are received during the forward stroke of the saw, along which the frequency of the local oscillator is tuned.

As a result of the operation of the CGP circuit, information on the sequence of signals from the radar with the corresponding numbers (signs) of the filters will be recorded in the storage device (9). When receiving on a direct channel, the sequence of signs has the form 5, 4, 3, 2, 1; when received via the mirror channel - 1, 2, 3, 4, 5.

In the node for comparing the filter numbers of the UPCH SGP filters (12) of the processing circuit (11), the received sequence is analyzed. If the sequence is decreasing (5, 4, 3, 2, 1), then a signal is generated in the logic device (13), which is issued on the first output to the signal carrier frequency measurement node (7) and indicates reception on the forward channel ; if the sequence is increasing (1, 2, 3, 4, 5), then a signal is generated in the logic device (13), which is issued at the second output and indicates reception through the mirror channel.

In the node for measuring the carrier frequency of the signal (7) according to the signals from the outputs 1 and 2 of the processing circuit (11), the value of the intermediate frequency of the signal is respectively added or subtracted to the value of the local oscillator frequency generated in the node for measuring the frequency of the local oscillator (6).

Using the proposed device can increase the likelihood of detection by determining the exact value of the carrier frequency of the pulse sequence, as it reduces the analysis time of the received signals.

The simulation results showed that under equal conditions for receiving signals, the probability of detection when working with the proposed device is 0.38, and when working with the prototype device - 0.23.

Reducing the number of device blocks increases the reliability of the system and, in addition, leads to a decrease in the economic cost of the product.

Claims (1)

Frequency-search superheterodyne receiver of pulse signals, comprising a logic device connected in series, units for measuring the carrier frequency of the signal and the local oscillator frequency, a local oscillator, a mixer, an intermediate frequency amplifier, a detector, a buffer register and a storage device, characterized in that, in order to increase the probability of correct determine the value of the carrier frequency when receiving both direct and mirror channels, in it the intermediate frequency amplifier is single-channel with tuned as different frequencies in filters and filters entered comparing unit numbers, connected between the output and the input of the memory logical device.

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