RU2097908C1 - Device for automatic search of radio stations - Google Patents

Abstract

FIELD: radio engineering. SUBSTANCE: device has reference frequency unit 1, receiver 2, recorder 3, frequency synthesizer 4, N strip line filters 5, N threshold gates 6, first register 7, second register 8, comparison unit 9, programmable read-only memory unit 10, inverter 11, clock oscillator 12, wide-band antenna amplifier 13. This results in possibility to detect radio station when it is scanned using several fixed frequencies by means of storing states of signals in whole range of frequencies used by radio station until transmitter alters its working frequency in order to compare band after this alternation. Receiver is tuned only to frequency which contains signal in given moment. EFFECT: increased probability of detection of communication channels which use frequent alternation of operating frequencies. 5 dwg

Description

 The invention relates to radio engineering and can be used in radio dispatch monitoring points for the analysis of the signal situation in the region, for the automatic search and detection of signals from radio stations that constantly change operating frequencies.

 A device for isolating pulsed signals against the background of noise and impulse noise [1] comprising two standard pulse shapers, a delay line, a memory unit, two I elements, a radio pulse selector, an amplitude detector, a threshold element, a pulse counter, a reference pulse generator, a comparison unit .

 Also known is a device for receiving tonal frequencies [2] comprising a matching unit, a pulse shaper, a trigger pulse shaper, a clock pulse generator, two counters, two AND elements, two read-only memory blocks, two counters, an OR element, a register, and a comparison unit.

 Such analogue circuits allow you to search for radio signals, but have a low probability of detecting the desired signal with frequent changes of the operating frequency by the transmitter.

 The closest in technical essence to the claimed device (prototype) is the known device for the automatic search for radio channels [3] This device contains a block of reference frequencies, a receiver, a signal converter, a register, a driver of control signals, a demultiplexer, K additional registers, a multiplexer, an indicator, distributor, comparison unit, initial installation unit. Thanks to this scheme, the device provides a search for radio channels with a minimum level of interference. In addition, the device can search for working radio stations by measuring the energy of the received signals.

 However, the prototype device has a drawback. With frequent changes of operating frequencies by radio stations, the device does not provide the required probability of detecting a working communication channel, since the signals of different stations can have the same energy.

 The aim of the invention is to develop a device for the automatic search for radio stations, providing a higher probability of detecting communication channels and low time spent searching with frequent changes of operating frequencies by the observed radio stations.

 This goal is achieved by the fact that in the known device for the automatic search for radio stations containing a series-connected block of reference frequencies, a receiver with an antenna and a signal recorder, as well as a register and a comparison unit, a frequency synthesizer, N band-pass filters, N threshold devices, a second memory register are additionally introduced device, inverter, clock generator, broadband antenna amplifier with antenna. (N corresponds to the number of fixed frequencies used by the radio). N bandpass filters are connected to N outputs of the frequency synthesizer, broadband antenna amplifier is connected to their second inputs, and filter outputs are connected to the corresponding inputs of N threshold devices, the outputs of which are connected to the corresponding inputs of the first and second registers. The outputs of the registers are connected to the corresponding inputs of the comparison unit, the output of which is connected to a reprogrammable read-only memory (EPROM). The output of the ROM is connected to the input of the block of reference frequencies. The second output of the receiver is connected to the second input of the first register and to the input of the inverter, the output of which is connected to the second input of the second register and to the second input of the ROM. The output of the clock generator is connected to the first inputs of the first and second registers.

 The introduction of new elements makes it possible to detect the observed radio station when it is scanned by the N applied fixed frequencies by storing the signal conditions of the entire range of frequencies used by the radio station until the transmitter changes the operating frequency and compares with the state of the range after it is changed. The receiver is tuned only to the frequency at which the signal appeared at a given time.

 In FIG. 1 shows a General structural diagram of the claimed device; in FIG. 2 circuit block comparison; in FIG. 3 figure illustrating the formula (1); in FIG. 4 is a graph of the probability of detection of a radio station from the recognition time; in FIG. 5 figure explaining the principle of detection of a radio station.

 The claimed device, a structural diagram of which is shown in FIG. 1, consists of a block of reference frequencies 1, receiver 2, registrar 3, frequency synthesizer 4, N bandpass filters 5, N-threshold devices 6, first register 7, second register 8, comparison unit 9, reprogrammable read-only memory (EPROM) 10 , inverter 11, a clock generator 12, a broadband antenna amplifier (SHAU) 13.

 The output of the reference frequency unit 1 is connected to the input of the receiver 2. The output 2.1 of the receiver 2 is connected to the input of the recorder 3. N outputs 4.1 4.n of the frequency synthesizer 4 are connected to the corresponding inputs 5.1.1 5.n.1 N bandpass filters 5.1 5.n. The outputs of N bandpass filters 5.1 5.n are connected to the corresponding inputs of N threshold devices 8.1 8.n, the outputs of which are connected to the corresponding inputs of 7.3.1 7.3.n of register 7 and inputs 8.3.1 - 8.3.n of register 8. The output of ШАУ 13 is connected with inputs 5.1.2 5.n.2 filters 5.1 - 5.n. The output of the clock generator 12 is connected to the input 7.1 of the register 7 and to the input 8.1 of the register 8. The output of the receiver 2.2 is connected to the input 7.2 of the register 7 and to the input of the inverter 11. The output of the inverter 11 is connected to the input 8.2 of the register 8 and to the input 10.2 of the ROM 10. Outputs registers 7 and 8 are n-bit and are connected by n-bit buses with the input 9.1 of the comparison unit 9, the output of the register 7 and the input 9.2 of the comparison unit 9, the output of the register 8. The output of the comparison unit 9 - the output of the register 8. The output of the comparison unit 9 is n-bit and connected by an n-bit bus to input 10.1 of the ROM 10. The output of the ROM is k-bit and connected k- Operating capacity bus to the input reference frequency unit 1.

 The reference frequency block 1 and receiver 2 are similar to those in the channel search device (ed. St. USSR N 1515373, class H 04 B 1/10, 1989). In addition, as a block of reference frequencies and a receiver, you can use the P-399A Katran, a commercially available radio receiver, where these blocks are technically implemented. As the recorder 3, any terminal equipment for recording a signal is applicable depending on the type of modulation and coding of the received signal. For example, to receive frequency telegraphy signals, we use the "BUK-D" demodulator with a teletype of the "RTA-7M" type. As a frequency synthesizer 4, any commercially available frequency synthesizer can be used that provides the generation of N oscillations with frequencies corresponding to the operating range of the observed radio stations. You can also use N crystal oscillators of the required frequencies. As band-pass filters 5, you can use any band-pass filters with a bandwidth corresponding to the spectrum band occupied by the observed radio station, for example, constructed according to the algorithms described in the book (Digital filters and signal processing devices on integrated circuits. Edited by V.F. Vysotsky , M. Radio and Communications, 1984). As an SHAU 13, any commercially available broadband antenna amplifier is applicable depending on the observed frequency range. So for a range of decameter waves you can use commercially available ShAU "Lily of the valley", "Acacia". Registers 7 and 8 parallel registers with a control input for recording permission can be implemented on the chips of the series 133, 134, 155, 555, 176, 561, 531, 533, 564. The ROM 10 can be implemented on the chips of the series 556, 573. The inverter 11 can be implemented on microcircuits of the series 133, 134, 155, 555, 176, 561, 531, 533. As a clock generator 12, any quartz square-wave generator of the required frequency can be used. As threshold devices 6, decisive circuits of commercially available receivers can be used.

 Comparison unit 9 may be implemented according to the circuit shown in FIG. 2. In particular, the circuit includes N logic elements OR NOT 91.1 91.n, N logic elements AND 92.1 92.n, N logic elements AND 93.1 93.n.

 The first inputs 91.1.1 91.n.1 of the elements OR-NOT 91.1 91.n are the n-bit input 9.1 of the comparison unit 9. The second inputs of the elements OR-NOT 91.1 - 91. n are closed to the housing. The first inputs 92.1.1 92.n.1 of the elements AND 92.1 92.n are the n-bit input 9.2 of the comparison unit 9. The second inputs of the elements AND 92.1 92.n are supplied with a supply voltage. The outputs of the elements OR NOT 91.1 91.n are connected to the corresponding inputs 93.1.1 93.n.1 of the logical elements AND 93.1 93. n. The outputs of the elements AND 92.1 92.n are connected to the corresponding inputs 93.1.2 93.n.2 of the logic elements AND 93.1 93.n. The outputs of the elements And 93.1 93.n are the n-bit output of the block comparison 9.

 The logical elements OR-NOT and AND can be implemented on the chips of the series 133, 134, 155, 555, 176, 561, 531, 533, 564.

 The claimed device operates as follows.

The block of reference frequencies 1 provides the formation of highly stable oscillations for receiving signals at fixed frequencies. The reference block input is digital, k-bit. At this input, code combinations of fixed frequencies of the output of the EEPROM are received 10. Highly stable oscillations come from the output of the block of reference frequencies to ensure reception at fixed frequencies. Highly stable oscillations corresponding to the ith fixed frequency are applied to the control input of receiver 2. Receiver 2 provides reception of signals at fixed frequencies. From output 2.1, the received signal goes to the registrar, where it is registered. To track the signal situation at the frequencies used by the radio station, N bandpass filters 5 are introduced into the device with a band corresponding to the band occupied by the radio transmission spectrum. Each filter is tuned to the ith fixed frequency using a frequency synthesizer 4, which produces N highly stable oscillations of the required frequencies. The broadband signal from the entire observed frequency range, amplified by the SHAU 13, is fed to the inputs of the filters 5, which allocate the required fixed frequency bands. A threshold device is connected to the output of each filter. Threshold devices 6 measure the levels of signals emitted by the filters, and in the case of the presence of a signal P _sig. > P _threshold. produce unit levels or, in the absence of it, P _sig. <P _threshold. , zero levels. Single and zero levels from the outputs of threshold devices are supplied in parallel to the information inputs of registers 7 and 8. Receiver 2 measures the level of the received signal. If there is a signal at the input of the receiver, P _sig. > P _threshold. , the receiver at output 2.2 (the output of the decision circuit) produces a single level, which is fed to the write enable input of the first register 7, which records the signal states of the range according to the sequence of clock pulses generated by the clock generator 13. The clock frequency F _t is selected from the required recognition time of the observed signal and is fed to the clock inputs 7.1 and 8.1 of registers 7 and 8. The input enable recording 8.2 of the second register 8 enters through the inverter 11 a zero level, prohibiting the recording of information in register 8. If the signal at the input of receiver 2 disappears, the receiver at output 2.2 generates a zero level that prohibits writing to the first register 7. At the N outputs of register 7, information about the signal situation at the time of the clock pulse remains before turning the transmitter off i-th fixed frequency. The input 8.2 of register 8 receives a single level that allows recording, and the state of the signal situation at the time of the first clock pulse after the disappearance of the observed signal is formed at the N outputs of register 8. From the N-bit outputs of both registers, information about the signal situation before and after the disappearance of the observed signal at the input of the receiver in parallel via N-bit buses is supplied to the corresponding inputs of the comparison unit 9. The output of the comparison unit 9 is also N-bit and connected by an N-bit bus with N-bit address input of the EEPROM 10. The number of address inputs of the EEPROM is 10 N and is selected depending on the number of fixed frequencies used by the radio station. Comparison unit 9 produces a unit level at that i-th output, where the zero state of the i-th output of register 7 corresponds to the single state of the i-th output of register 8. At the other outputs of the comparison unit 9, there are zero levels. EPROM 10 is programmed in such a way that each address corresponding to the ith output of the comparison unit 9 corresponds to a fixed frequency code. EEPROM output 10 K-bit depending on the length of the fixed-frequency combination. Upon receipt from the comparison unit 9 of a unit level by any i-th category of an N-bit output to the address input of the ROM 10 and if there is a single level at the read permission input 10.2, the ROM 10 which comes from the inverter 11, the ROM 10 generates a fixed frequency code , which in parallel via the K-bit bus enters the input of the block of reference frequencies 1, thereby tuning the receiver to the desired fixed frequency. If a signal is not detected, the process will repeat with the next clock cycle. When a signal is detected at the output 2.2 of the receiver 2, a unit level is formed that will allow writing to the first register 7, and a zero level from the output of the inverter 11 will prohibit writing to the second register 8 and reading of the ROM 10.

 The comparison unit 9 operates as follows.

 The first inputs 91.1.1 91.N.1 N of the OR-NOT 91.1 91.N logic elements receive zero and single levels from the outputs of the first register 7. The second inputs of the OR-NOT elements are closed to the case. Since the desired signal, when the transmitter changes the operating frequency, can appear only at a free (unoccupied) fixed frequency, it is first necessary to determine all the zero states of the outputs of register 7. At the outputs of N elements, the unit level will NOT appear only where the first input goes to zero level from the output of the register 7. From the outputs of the elements OR NOT, the zero and unit levels go to the corresponding first inputs 93.1.1 93.N.1 N of the logical elements AND 93.1 - 93.N. The first inputs 92.1.1 92.N.1 N of the logic elements AND 92.1 92.N receive zero and single levels from the outputs of the second register 8. The second inputs of the elements And are supplied with a supply voltage. From the outputs of the AND elements, the unit and zero levels corresponding to the states of the outputs of the second register 8 (the state of the range after the transmitter changes the operating frequency) go to the second inputs 93.1.2 93. N 2 N logic elements AND 93.1 93.N. The I-th logical element And 93.i produces a unit level only when two unit levels arrive at its inputs, i.e. in the case when, when the observed transmitter changes the operating frequency at a previously unoccupied frequency, a signal appears at a given point in time.

 Justification of the positive effect of the proposed device is as follows.

 An indicator of the effectiveness of systems for automatic monitoring of signal-to-noise conditions is the probability of detecting signals when searching for a new operating frequency (communication channel) of the observed radio station, if as a result of the interference complex the transmitter is often forced to change the operating frequencies to achieve the required communication quality.

 The task is to achieve the maximum probability of signal detection with minimal time spent on analysis.

 The receiver tuning rate when searching for the desired signal is limited and the tuning period for N fixed frequencies may be longer than the duration of the received signals. In this case, the time of existence of the signal at certain frequencies will not always coincide with the time of viewing the corresponding portion of the viewing band by the receiver. Therefore, the signals will be detected with a certain probability, depending on the speed of analysis and the duration of the signal emitted at the i-th fixed frequency.

When the transmitter is tuned to N fixed frequencies, the probability of detecting this transmitter will correspond to the probability of the time-frequency coincidence of the receiver tuning frequency with the current frequency of the desired signal. If we assume that the channel polling duration is constant t _c const, then the tuning period for N fixed frequencies will be equal to:
TN • t _c ,
where t _{c is the} time during which the i-th fixed frequency is polled;
N is the number of fixed frequencies (Fig. 3).

The receiver tuning speed within the entire search range will be equal to:
γ = Φ _o / T = Φ _o Nt _c ,
where Φ _{o is the} band occupied by N frequencies.

где Δt_o время регистрации сигнала, необходимое для его обнаружения;
Δf полоса частот передачи;
τ_c const длительность сигнала, излучаемого на каждой фиксируемой частоте.To assess the probability of a frequency-time coincidence of the tuning frequency of the receiver with the current operating frequency of the transmitter, we use the relation (1):

where Δt _o the signal registration time required for its detection;
Δf transmission frequency band;
τ _c const is the duration of the signal emitted at each fixed frequency.

Так как Δf/γ t_c время просмотра элементарного участка диапазона (время опроса канала)

Если принять, что время просмотра элементарного участка диапазона равно времени, необходимому для распознавания сигнала

Очевидно, что P_совп 0, при τ_c/Δt_р ≅ 1 и P_совп 1, если τ_c/Δt_р > N+1 Также очевидно, что вероятность частотно-временного совпадения будет выше при уменьшении времени распознавания. График зависимости P_совп P(Δt_р) приведен на (фиг. 4, график 1).Given that: Φ _o = γ • Nt _c

Since Δf / γ t _{c is the} time of viewing the elementary part of the range (channel polling time)

If we assume that the viewing time of an elementary part of the range is equal to the time required for signal recognition

Obviously, P _coincides 0, for τ _c / Δt _p ≅ 1 and P _coincides 1 if τ _c / Δt _p > N + 1. It is also obvious that the probability of time-frequency coincidence will be higher with decreasing recognition time. The graph of P _coincides P (Δt _p ) is shown in (Fig. 4, graph 1).

 It is possible to increase the probability of detection by reducing the analysis time of an elementary part of the range, which is impossible due to the limited time required for recording the signal. Therefore, the only way is to reduce the number of analyzed elementary sections of the range, which is achieved by the proposed device by storing the state of the signal situation of the entire range of frequencies used at the time the transmitter changes the operating frequency and compares with the state of the range after it is changed. The receiver is tuned only to the frequency at which the signal appeared at a given time.

 The principle of determining the desired frequency is shown in FIG. 5, where graph 1 shows the state of the frequency range before the transmitter changes the operating frequency; on chart 2, the state of the frequency range at the time of changing the operating frequency; on chart 3, the state of the frequency range after changing the operating frequency; in graph 4, the frequency of tuning the receiver.

It can be seen from the figure that the transmitter, initially operating at the frequency F _m , tuned to the frequency F ₂ , which will be the desired working frequency, since at the other frequencies there is no signal and there is no need to view them or there is a signal that was present before the change in the observed operating frequency transmitter, therefore belonging to an unobservable radio station.

From the foregoing, we can conclude that in the process of searching for a radio station when changing its operating frequency, there is no need to spend time on tuning the receiver for all N fixed frequencies used by it, but it is enough to analyze one frequency that is turned on again. Then the probability of detection can be written as:
P _coinc = τ _c / Δt _p -1,
which for a fixed time of signal recognition depends only on the time of emission of the signal at a fixed frequency. The dependence of the detection probability on the recognition time is shown in (Fig. 4, graph 2), which shows that when the analysis time is reduced from T to Δt _p , the detection probability is increased from 0.3 to 0.99 for typical operating conditions, which confirms a significant the positive effect of the implementation of the proposed device.

Claims (1)

 An automatic search station for radio stations containing a reference frequency unit connected to the control input of the receiver with an antenna and a signal recorder, as well as a first register and a comparison unit, characterized in that a frequency synthesizer, N bandpass filters, N threshold devices, a second register, reprogrammable, are additionally introduced a storage device, an inverter, a clock generator, a broadband antenna amplifier and an antenna connected to it, and N bandpass filters are connected to the N outputs of the frequency synthesizer, the second inputs of which a broadband antenna amplifier is connected, and the outputs of the bandpass filters are connected to the corresponding inputs of N threshold devices, the outputs of which are connected to the corresponding inputs of the first and second registers, the outputs of which are connected to the corresponding inputs of the comparison unit, the output of which is connected to a reprogrammable memory device, the output of which connected to the input of the block of reference frequencies, in addition, the second output of the receiver is connected to the second input of the first register and the input of the inverter, the output otorrhea connected to the second input of the second register and a second input of the reprogrammable memory device and to the first inputs of the first and second output registers connected to the clock generator.

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