RU2161863C2 - Device for monitoring of operation of radio stations with pseudorandom retuning of operating frequency - Google Patents

Abstract

FIELD: radio engineering, applicable for detection of going on the air of radio stations with pseudorandom retuning of operating frequency, their direction finding and determination of the spectrum of used frequencies. SUBSTANCE: masking signals coming from other directions are eliminated, detection of weak short-time signals with pseudorandom retuning of operating frequency, measurement and record of the values of their frequencies are facilitated. EFFECT: detection of weak short-time signals in loaded frequency against the background of a great number of high-power masking interferences. 4 dwg

Description

 The invention relates to the field of radio engineering and can be used to detect the broadcasting of radio stations with pseudo-random tuning of the operating frequency (PREF), their direction finding and determining the grid of frequencies used.

 Currently, a large number of imported radio stations capable of working in the mode of changing operating frequencies are available for sale. So, for example, the FT-2500M radio station of YAESU firm can scan on 30 preset frequencies in the range of 130-175 MHz. In negotiations, one word can be transmitted on one frequency, and the next on another. With an unknown ensemble of scanning frequencies, monitoring the operation of such radio stations is significantly complicated even when using a panoramic receiver with visual indication.

 Indeed, it is necessary to establish the ownership of a short-term signal of a given radio station and evaluate its frequency, which is difficult in busy frequency ranges with weak useful signals and a large number of masking signals.

 To select signals in the direction of arrival, panoramic receivers are equipped with direction-finding antennas. Known devices that provide direction finding either to the maximum amplitude of the signal, or to a minimum (Belavin OV Fundamentals of radio navigation. Publishing house 2 nd - M: Sov. Radio, 1977, p. 98-110).

 A significant reduction in the number of masking signals can be achieved with direction finding to the maximum by narrowing the antenna pattern. However, obtaining narrow radiation patterns in the ranges of relatively low frequencies is difficult. With a minimum direction finding (with a cardioid radiation pattern), a significant reduction in the number of masking signals cannot be achieved.

 Closest to the proposed device is a device for automatically selecting the receiving channel ("Foreign Radio Electronics", M .: "Sov. Radio", 1979, N 3, p. 44, Fig. 5), adopted as a prototype.

 A generalized functional diagram of the prototype device is shown in FIG. 1.

Designations:
1, 2 - respectively, the first and second receiving antennas;
3, 4 - respectively, the first and second radio paths;
5 - local oscillator;
6 - the first switch;
7 ¹ , 7 ² - amplitude detectors;
8 is a comparison diagram (threshold block);
9 - the second switch.

 In the prototype device, the first inputs of both radio paths are connected respectively to the first and second receiving antennas, the second outputs of both radio paths are connected to the local oscillator output, and the outputs of both radio paths are connected to the first and second inputs of the first and second switches, respectively, with the first and second outputs of the first switch through amplitude detectors are connected to the corresponding inputs of the comparison circuit (threshold block), the output of which is connected to the third input of the second switch, the output of which is the output device home.

 The operation of the prototype device is as follows.

 Signals of different intensities from the outputs of the antennas arrive at the inputs of the corresponding radio paths, the tuning frequency of which is determined by the frequency of the local oscillator. In radio paths, amplification, frequency selection and transfer of input signals to an intermediate frequency are carried out. From the outputs of the radio paths, the signals through the switch 6 are alternately supplied to the corresponding amplitude detectors, the voltage at the outputs of which are proportional to the intensities of the output signals of the antennas. The comparison circuit (threshold block) controls the second switch, which passes the larger of the signals from the outputs of the radio paths to the output.

 The prototype device, in principle, allows the selection of signals in the direction of arrival, however, it has the disadvantage that it does not allow to detect weak signals from the frequency hopping frequency and evaluate the frequencies of their elements. To eliminate this drawback, a radiation pattern control unit, a series-connected frequency meter and a memory unit, as well as first and second amplitude detectors, are introduced into the device containing the first antenna and the first radio path, as well as the second antenna, the second radio path, threshold block and switch, division circuit, indicator and serially connected stop pulse generator, sawtooth generator and voltage controlled generator, the output of which is connected to volt the first inputs of the first and second radio paths, the second receiving antenna through the radiation pattern control unit connected to the first input of the second radio path, the output of which through the second amplitude detector is connected to the second input of the division circuit and the third input of the switch, to the fourth input of which, as well as to the second the outputs of the stop pulse generator are connected to the inputs of the memory unit and the frequency meter, the second output of the first radio path is connected to the first input of the frequency meter, and the first output of the first radio path through rvy amplitude detector connected to the second input switch and the first input circuit dividing the output of which is connected to the first input of the switch and through the threshold unit with input of the stop pulse, the ramp voltage generator output is connected to the first input of the indicator, the second input of which is connected to the output switch.

Functional diagram of the proposed device is presented in FIG. 2, where indicated:
1 - the first receiving antenna with a circular radiation pattern;
2 - the second receiving antenna with a cardioid radiation pattern;
3 - radiation pattern control unit;
4 - memory block;
5 - frequency counter;
6 ¹ , 6 ² - the first and second radio paths;
7 ¹ , 7 ² - the first and second amplitude detectors;
8 - voltage controlled oscillator;
9 - sawtooth voltage generator;
10 - stop pulse shaper;
11 - threshold block;
12 is a division diagram;
13 - switch;
14 - indicator.

 The operation of the proposed device is as follows.

A voltage controlled oscillator 8, under the action of a sawtooth control voltage from a sawtooth voltage generator 9, generates a reference signal with a ramp frequency. At the outputs of the radio paths, input signals from the corresponding frequency range are sequentially allocated in time. After amplitude detection, these signals are amplified in the indicator and fed to the vertically deflecting plates of the cathode ray tube (indicator), to the horizontally deflecting plates of which a sweep voltage is supplied from the output of the sawtooth voltage generator 9. As a result, a spectral density picture in the corresponding frequency range. Due to the fact that the same linearly frequency-modulated signal from the output of the voltage-controlled generator 8 is supplied to the reference inputs of the first 6 ¹ and second 6 ² radio paths, the same input signal is observed at the outputs of both radio paths at any time. The amplitude of the signal at the output of the first radio path does not depend on the direction of arrival of the input signal due to the circular appearance of the radiation pattern of the first antenna 1 (Fig. 3, 1). The second antenna 2 has a cardioid radiation pattern (Fig. 3, 2), the rotation of which is carried out by the control unit 3. The envelopes of the spectra of the input signals from the outputs of the amplitude detectors 7 are fed to the inputs of the division circuit 12 and switch 13. The switch 13 is used to connect to the input of the indicator 14 one of the signals: s radiopathes outputs 6 ^1, 6 ² and the output from the dividing circuit 12. to the selection signal arrival direction by using a cardioid polar pattern control unit 3 of the antenna 2 is rotated to align the zero th dip from the signal arrival direction (FIG. 3). The amplitude of the signals from this direction at the output of the second radio path 6 ² is close to zero, therefore, at the output of the division circuit 12, which divides the amplitude of the signal from the output of the first radio path 6 ¹ by the amplitude of the signal from the output of the second radio path 6 ² , at this moment the voltage will be maximum.

 It should be emphasized that the magnitude of the ratio does not depend on the field strength of the signals at the receiving site. The moment of maximizing the ratio is fixed by indicator 14. The threshold value is set so that the threshold block 11 is triggered only by signals coming from the zero direction.

 When the threshold block 11 is activated, the driver 10 generates a pulse that stops the sawtooth voltage generator 9, starts the frequency counter 5, allows the signal to pass to the indicator 14 and writes to the memory unit 4. During the duration of this pulse, the frequency meter measures the signal frequency, which is recorded in the memory unit 4 .

 Thus, masking signals coming from other directions are eliminated, and it becomes possible to detect weak short-term signals with frequency hopping, measure and record the values of their frequencies.

 The control unit of the rotating cardioid radiation pattern 3 can be performed according to Fig. 9.10 on p. 131 in the book of Fradkin A.Z. Antenna feeder devices. M .: "Communication", 1977.

 The division circuit of two analog signals 12 can be performed by including a multiplier in the feedback circuit of the amplifier (see the book by Alekseenko et al. The use of precision analog microcircuits, 2nd ed., Moscow: Radio and Communication, 1985, p. 113, 114).

 The switch 13 may be configured as shown in FIG. 4.

Claims (1)

 A device for monitoring radio stations with pseudo-random tuning of the operating frequency, comprising a first antenna and a first radio path connected in series, as well as a second antenna, a second radio path, a threshold unit and a switch, characterized in that a radiation pattern control unit, a frequency meter and a memory unit connected in series, are inserted, and also the first and second amplitude detectors, a division circuit, an indicator and a serially connected stop pulse generator, a sawtooth voltage generator and a generator a voltage-controlled oscillator, the output of which is connected to the second inputs of the first and second radio paths, while the second receiving antenna is connected through the radiation pattern control unit to the first input of the second radio path, the output of which is connected through the second amplitude detector to the second input of the division circuit and the third input of the switch, to the fourth input of which, as well as to the second inputs of the memory unit and the frequency meter, the output of the stop pulse former is connected, the second output of the first radio path is connected to the first the frequency counter input, and the first output of the first radio path through the first amplitude detector is connected to the second input of the switch and the first input of the division circuit, the output of which is connected to the first input of the switch and through the threshold block with the input of the stop pulse generator, and the output of the sawtooth generator connected to the first input of the indicator whose second input is connected to the output of the switch.

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