RU2751018C1 - Coherent path of radar station with variable (switchable) intermediate frequency - Google Patents

Abstract

FIELD: radar engineering.

SUBSTANCE: invention relates to radar technology and is intended for use in radar stations for the formation of reception, transmission and processing of radio signals necessary for the operation of radar equipment. To achieve the technical result, used are a heterodyne, a reference generator, a control device and a receiving and transmitting antenna common to both paths, transmitting and receiving, and also use a variable first intermediate frequency. The coherent path of a radar station with a variable, switchable intermediate frequency contains filtering and amplification units of the first and second intermediate frequencies of the receiving path, a control device, the first frequency converter of the receiving path, the second frequency converter of the receiving path, and a modulating signal generator.

EFFECT: simplification of the construction of coherent radar and radio navigation stations.

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Description

The invention relates to radar technology and is intended for use in radar stations for the formation of reception, transmission and processing of radio signals necessary for the operation of radar equipment.

State of the art

From the prior art, technical solutions are known related to the technique of processing signals from radar stations, constructing coherent radar and radio navigation stations, namely, a coherent path of a radar station with a variable (switchable) intermediate frequency (hereinafter referred to as a coherent path of a radar).

The task to be solved is:

- simplification of the construction of coherent radar and radio navigation stations by using a local oscillator, a reference oscillator, a control device and a receiving-transmitting antenna common to both channels - transmitting and receiving, as well as using a variable first intermediate frequency.

The analysis of the state of the art made it possible to establish that analogs characterized by a set of features identical to all features of the proposed technical solution are absent, which indicates the compliance of the claimed invention with the "novelty" condition of patentability.

The results of the search for known solutions in this and related fields of technology in order to identify features that coincide with the distinctive features of the claimed device showed that they do not follow explicitly from the prior art and the known influence of the distinctive features on the claimed technical solution is not confirmed. Therefore, the claimed invention meets the “inventive step” requirement of patentability.

The claimed technical solution is industrially applicable, since it can be used in the military-industrial complex, and standard equipment and materials can be used for its implementation.

The essence of the invention lies in the fact that the coherent path of the radar Fig. 1 contains two paths - transmitting and receiving, as well as a local oscillator, a reference oscillator, a control device and a transmit-receive antenna, which are common to both paths and works as follows: external control signals are fed to the control device 11, which controls the frequency of the tunable local oscillator 12, modes of operation of the baseband shaper 17 and the shaper of the reference frequency for the ADC, as a reference signal for the tunable local oscillator 12, highly stable oscillations from a thermostated quartz oscillator 13 are used, the tunable local oscillator 12 forms a common frequency grid for the transmitting and receiving paths ( f _GET ), the generated signal from the local oscillator outputs is fed to the unit for dividing the frequency, filtering and amplifying the local oscillator signal of the receiving path 7 and the frequency dividing, filtering and amplifying the local oscillator signal of the transmitting path 14. Nodes 7 and 14 are built in the same way and perform the functions of amplifying the local oscillator frequency, dividing by two and three, the LO frequency signal divided by three ( f _GET / 3) is used as a reference signal by shapers 6 and 17, the local oscillator frequency signal divided by two ( f _GET / 2), is used as heterodyne signals ( f _{GET1 RX} = f _GET / 2 and f _{GET1 TX} = f _GET / 2) in the second frequency converters 2 and 18 of the receiving and transmitting paths. The baseband generator 17 forms at a frequency f _{PCh2 TX} probing signals with the required duration and pulse filling. The baseband shaper 17 is built on a direct synthesis frequency synthesizer, similarly, a reference frequency shaper for the ADC is built on a direct synthesis frequency synthesizer, a frequency-variable reference signal is fed to the reference frequency input of the shapers 6 and 17 ( f _GET / 3). Control device when changing the reference signal ( f _GET / 3) recalculates the coefficients so that the reference frequency for the ADC and the baseband signal ( f _{PCh2 TX} ) were constant in frequency, the amplified signal ( f _GET ) is fed to frequency multipliers 8 and 15 of the receiving and transmitting paths, in which the local oscillator frequency is multiplied by 4 (4 * f _GET ). After amplification and filtering at nodes 9 and 16, the generated signals of the first local oscillators ( f _{GET1 RX} =four* f _GET and f _{GET1 TX} =four* f _GET ) of the receiving and transmitting paths, respectively, are fed to the first frequency converters 4 and 20, from the output of the first frequency converter of the transmitting path 20 the generated signal at the radiation frequency ( f _{cT X} ) is fed to the unit for filtering and amplifying the output signal 21 for final amplification and transmission to the antenna system 10 for radiation, the received reflected signal f _{from RX} is fed to the unit of protection, filtering and amplification of the input signal 5 and then to the frequency converter (4), from the output of which the signal ( f _{PCh1 RX} ) is fed to the filtering and amplification unit of the first intermediate frequency of the receiving path (3). Further, the signal ( f _{PCh1 RX} ) is fed to the second frequency converter of the receiving path (2), from the output of which the signal ( f _{PCh2 RX} ) is fed to the filtering and amplification unit of the second intermediate frequency of the receiving path (1). Further, the signal ( f _{PCh2 RX} ) is fed to an analog-to-digital converter (ADC) for further processing in digital form.

Calculation of the frequency of the first local oscillators ( f _{HET1 TX} and f _{HET1 RX} ) depending on the frequency of emission (reception) for the case shown in Fig. 1, where the multiplicity between the frequencies of the local oscillators is 8, in the control device (11) is carried out according to the formula:

f _GET = ( f _C - f _IF2 ) / 0.875 (1)

where f _C is the frequency of radiation (reception);

f _IF2 - second intermediate frequency.

In the general case, when the multiplicity between the frequencies of the local oscillators has an arbitrary value, formula (1) has the following form:

f _ГЕТ1 = ( f _С - f _ПЧ2 ) * N / (N-1) (2)

where N is the multiplicity between the frequencies of the local oscillators N = f _GET1 / f _GET2 ; (3)

Calculation of the variable value of the first intermediate frequency relative to the signal frequency for the case shown in FIG. 1 is carried out according to the formula:

f _PCh1 = ( f _С –8 f _PCh2 ) / 7 (4)

In the general case, when the multiplicity between the frequencies of the local oscillators has an arbitrary value, formula (4) has the following form:

f _FC1 = ( f _С –N * f _FC2 ) / (N-1) (5)

Calculation of the necessary bandwidth of the first intermediate frequency as a function of the signal emission (reception) bandwidth for the case shown in FIG. 1 is carried out according to the formulas:

B _PCh1 = B _С / 7 (6)

B _{PCH1V IF} = f - f _PCH1N (7)

B _с = f _сВ - f _сН (8)

where: B _IF1 - the required bandwidth of the first intermediate frequency, taking into account its tuning, depending on the frequency of radiation (reception) of the signal;

B _С - frequency band of the emitted (received) signal;

f _cV - the upper value of the frequency of the emitted (received) signal;

f _cN - the lower value of the frequency of the emitted (received) signal;

f _ПЧ1В - the upper value of the first intermediate frequency, corresponding to the upper value of the frequency of the emitted (received) signal;

f _ПЧ1Н - the lower value of the first intermediate frequency corresponding to the lower value of the frequency of the emitted (received) signal;

In the general case, when the multiplicity between the frequencies of the local oscillators has an arbitrary value, formula (6) has the following form:

B _PCh1 = B _С / (N-1) (9)

From formula (9) it follows that with such a construction of the transceiver path, the passband of the first intermediate frequency is (N-1) times less than the frequency band of the emitted (received) signal. If necessary, the bandwidth of the first intermediate frequency is split into several narrow bands in accordance with FIG. 2. The control device 11 connects the corresponding narrow-band filter depending on the frequency of the emitted (received) signal.

The coherent path of the radar works as follows, the control device controls the frequency of the tunable local oscillator, the operating modes of the baseband shaper and the shaper of the reference frequency for the ADC, the tunable local oscillator forms a common frequency grid for the transmitting and receiving paths, the generated signal from the outputs of the local oscillator is fed to the frequency division and filtering unit and amplification of the local oscillator signal of the receiving path and a unit for dividing the frequency, filtering and amplifying the local oscillator signal of the transmitting path, which perform the functions of amplifying the local oscillator signal, dividing the frequency by 2 and 3, the local oscillator frequency signal divided by 3 is used as a reference signal by the shapers, the frequency signal the local oscillator divided by 2 ( f _HET / 2), is used as heterodyne signals ( f _{HET1 RX} = f _HET / 2 and f _{HET1 TX} = f _HET / 2) in the second frequency converters of the receiving and transmitting paths, the baseband shaper forms at the frequency f _{IF2 TX to the} probe signals with the required duration and pulse filling, the baseband shaper and the reference frequency shaper for the ADC are based on direct synthesis frequency synthesizers, to the input of the reference frequency of which a frequency-variable reference signal ( f _GET / 3) is fed, a control device when the reference signal changes ( f _GET / 3) recalculates the coefficients so that the reference frequency for the ADC and the base signal ( f _{IF2 TX} ) are constant in frequency, the amplified signal ( f _GET ) is fed to the frequency multipliers of the receiving and transmitting paths, in which the local oscillator frequency is multiplied by 4 (4 * f _GET ), after amplification and filtering, the generated signals of the first local oscillators ( f _{GET1 RX} = 4 * f _GET and f _{GET1 TX} = 4 * f _GET ) of the receiving and transmitting paths, respectively, are fed to the first frequency converters, from the output of the first converter frequency of the transmitting path, the generated signal at the radiation frequency ( f _{cT X} ) is fed to the filtering unit and amplification of the output signal for final amplification and transmission to the antenna system for radiation, the received reflected signal f _{from RX} is fed to the node for protection, filtering and amplification of the input signal and then to the frequency converter, from the output of which the signal ( f _{IF1 RX} ) is fed to the node filtering and amplification of the first intermediate frequency of the receiving path, then the signal ( f _{IF1 RX} ) is fed to the second frequency converter of the receiving path, from the output of which the signal ( f _{IF2 RX} ) is fed to the filtering and amplification unit of the second intermediate frequency of the receiving path, then the signal ( f _{IF2 RX} ) is fed to an analog-to-digital converter (ADC) for further processing in digital form, when the radiation frequency changes, the first intermediate frequency changes, the value of which is calculated using the above formulas and a corresponding filter is connected for narrow-band signal filtering both in the receiving and transmitting paths ...

The essence of the invention is also illustrated by the diagrams shown in Figs. 1, 2. Fig. 1 shows a functional diagram of a coherent radar path, consisting of the following units:

1- node of filtering and amplification of the second intermediate frequency of the receiving path f _IF2 ,

2 - the second frequency converter of the receiving path,

3 - unit of filtering and amplification of the first intermediate frequency of the receiving path f _IF1 ,

4 - the first frequency converter of the receiving path,

5- node of protection, filtering and amplification of the input signal,

6 - shaper of the reference frequency for the ADC (analog-to-digital converter),

7 - node for dividing frequency, filtering and amplifying the local oscillator signal of the receiving path,

8 - unit for multiplying the frequency of the local oscillator of the receiving path by four,

9 - unit of filtering and amplification of the quadruple frequency of the local oscillator of the receiving path,

10 - antenna system,

11 - control device,

12 - tunable local oscillator,

13 - reference frequency generator,

14 - node for dividing the frequency, filtering and amplifying the local oscillator signal of the transmitting path,

15 - node for multiplying the frequency of the local oscillator of the transmitting path by four,

16 - unit for filtering and amplification of the quadruple frequency of the local oscillator of the transmitting path, 17 - shaper of the modulating signal (chirp, PCM, etc.),

18 - the second frequency converter of the transmitting path,

19 - unit of filtering and amplification of the first intermediate frequency of the transmitting path ( f _IF1 ),

20 - the first frequency converter of the transmitting path,

21 - unit for filtering and amplifying the output signal.

FIG. 2 shows the filtering circuit of the first intermediate frequency, using two switches (1 and 2) of the corresponding frequency range and a set of narrow-band filters that overlap the necessary bandwidth of the first intermediate frequency, connecting the corresponding filter (1, 2 ... N), the center frequency of which is calculated according to the formula (4) depending on the frequency of emission (reception) of the signal.

Claims (1)

A coherent path of a radar station with a variable, switchable intermediate frequency, containing in the receiving path a first intermediate frequency converter, a first filtering and intermediate frequency amplification unit, a second frequency converter and a second filtering and intermediate frequency amplification unit, and in the transmission path, a modulating shaper connected in series signal, the first intermediate frequency converter, the first intermediate frequency filtering and amplification unit, the second intermediate frequency converter and the second intermediate frequency filtering and amplifying unit, the output of which is connected to the input of the antenna system, the output of which is connected to the input through the input signal protection, filtering and amplification unit the first converter of the intermediate frequency of the receiving path, as well as a control device and a reference frequency generator, characterized in that a tunable local oscillator is introduced, one output of which is connected to the transmission a circuit with a series-connected unit for dividing the frequency, filtering and amplifying the local oscillator signal, a unit for multiplying the local oscillator frequency by four, the output of which is connected to the heterodyne input of the second intermediate frequency converter, the second and third outputs of the frequency division, filtering and amplifying the local oscillator signal are connected to the heterodyne inputs the baseband signal former and the first intermediate frequency converter, the second output of the tunable local oscillator is connected in the receiving path with a series-connected unit for dividing the frequency, filtering and amplifying the local oscillator signal, a unit for multiplying the local oscillator frequency by four and a filtering and amplifying unit for a quadruple local oscillator frequency, the output of which is connected to the local oscillator the input of the first converter of the intermediate frequency, and the second and third outputs of the unit for dividing the frequency, filtering and amplifying the local oscillator signal of the receiving path are connected to the heterodyne inputs of the second converter of the intermediate frequency you and the shaper of the reference frequency for the analog-to-digital converter (ADC), while the control device is configured to control the frequency of the tunable local oscillator, the operating modes of the baseband shaper and the shaper of the reference frequency for the ADC, a thermostatted crystal oscillator is used as a reference oscillator for the tunable local oscillator, the tunable local oscillator is configured to form a common frequency grid for the transmitting and receiving paths, the baseband shaper and the reference frequency shaper for the ADC are based on direct synthesis frequency synthesizers.

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