RU2414722C2 - Method of mirror radio location in rls ni - Google Patents

Abstract

FIELD: radio engineering.

SUBSTANCE: method of radio location in RLS NI applies linear frequency modulation of double side strip of carriers of radio-locating signal, separate reception of side strips, rejection, detection of radial speed and distance with "resolution". At the same time carriers are modulated in a mirror manner, are radiated by one and received by another pattern of directivity, one is distracted from another.

EFFECT: suppression of wide class of noises, increased lengthy borders and reduced rejection limits.

Description

The invention relates to radar technology and can be used in radar NI to determine the range of targets with "resolution" and its reference to speed based on linear frequency modulation (LFM) of the emitted signal.

The LFM of the emitted frequency opens up the possibility of determining the range to the targets in the radar NI based on the difference between the frequencies emitted and received, which occurs due to the delay in the propagation of the signal to the target and vice versa.

However, this raises a number of problems associated with the presence in the received signal, apart from the rangefinder (d / m) and Doppler frequencies, which must be separated, and if the targets are several in azimuth, then determine whether each d / m frequency belongs to a specific of several Doppler frequencies, those. solve the problem of 'resolving' targets in range with reference to speed.

The solution to these problems is also hindered by the presence of powerful interfering ground reflections in the received signals, frequency and amplitude noise of the transmitter, the need for suppression of which leads to the use of notch with a suppression ratio of 100-130 dB.

Due to the delay in the propagation of reflections and LFM carriers, the spectrum of ground reflections extends to 1-2.5 kHz or more, and the need to suppress them leads to an expansion of the notch limits, which excludes from the analysis a significant part of the possible values of Doppler and d / m frequencies of signals reflected from goals.

In a distant analogue of the claimed invention is a method of linear-frequency modulation of a double sideband of a radar signal, operating on the upper and lower sidebands of carrier waves, which receives carrier waves, separates the upper and lower sidebands of carrier waves in which there are Doppler components characterizing the range to the target, the signals of the upper and lower side bands are coherently combined to separate the Doppler component and the component characterizing the range, mix the signals of the ver it and lower sidebands to form sum output signal which is supplied to a notch filter clutter signals to isolate the desired signal and determining the radial velocity of the target (see. U.S. Patent №4388622, MKI G01S 13/34, G01S 13/58, 1981),

the task of determining the parameters of targets with a "resolution" over the range of several targets at one azimuth is not posed at all, because the analogue solves the problem of determining the parameters of a single target, the limits of the frequency notch, especially with chirp with the antenna pattern in the surface layer, are large, and interference suppression is carried out only in the notched area, which makes it impossible to realize the sensitivity of modern radar receivers outside the notch.

A closer analogue, chosen as a prototype due to the similarity of the task being performed - “resolving” the range of several targets at one azimuth with reference to radial speeds, is a method that uses linear frequency-frequency modulation of the double sideband of the radar signal, the reception and rejection of the side Separately, additionally, an unmodulated signal of the central carrier frequency is added to the radar signal, which is received separately at its carrier frequency and is rejected, the targets are divided by increasing and approaching, they determine the frequency shift of the signals relative to the carrier frequencies, calculate the half-sums of pairs of frequency signals with the opposite sign of the rangefinder frequency shift relative to each Doppler frequency shift, select the frequency pairs whose half-sums are equal to the Doppler frequency shifts, and calculate their half-difference (see. USSR No. 286 399 with MKI G01S 13/34, G01S 13/58, 1987).

The prototype of the claimed invention is characterized by a high level of noise in the receiver path, which is caused by noise in the signal of the transmitting device, reflections of local objects, especially with chirp, fluctuations in the movement of targets in space, active interference, etc., which leads to a coarsening of the receiver sensitivity, reducing / m lines, increase the limits of notch.

The technical result of the invention is the suppression of interference, an increase in d / m boundaries and a reduction in the limits of rejection by introducing for the first time radar carriers in the radar, suppressing a wide class of interference in the entire range of possible analysis frequencies.

The specified technical result is achieved by the fact that in the radar NI using linear frequency modulation of the double sideband of the carriers of the radar signal, the reception of the sidebands separately, rezektirovanie, determination of radial speed and range with "resolution",

the carriers modulate specularly, emit one and receive one radiation pattern, subtract one from the other.

In particular, in order to effectively suppress interference by subtracting one carrier from another, mirroring implies:

- the equality of the power of the emitted carriers, the symmetry of their frequencies, phases and modulation rates relative to the frequency of the master transmitter transmitter, as well as their radiation with a single radiation pattern;

- receiving carriers with a single radiation pattern and the identity of the amplitude-frequency characteristics of the channels of the two-channel receiver,

those. It implies specularity of both equipment and signals, which is the basis for the introduction of the term mirror radar.

In the well-known prototype (see USSR AS No. 286 399 with MKI G01S 13/34, G01S 13/58, 1987), the task of mirroring the equipment and signals is not posed.

The operation of subtraction, in order to determine the difference d / m frequencies, in the prototype is carried out after rejection, cumulative filtering, etc. - the latter, in digital form, and in the proposed method, before rejection and to filters determining the sensitivity of the receiver, in analog form, where interference is still present and when subtracted, they are suppressed in accordance with the expression for the sine difference:

where: - W / 2 - signal power from the target of each of the carriers;

- f _g , f _r , f _d - heterodyne, d / m and Doppler frequencies, respectively, and when analyzing the difference signal, we obtain:

- in the first factor W, the sum of the capacities of the carriers, i.e. radiation by two carriers without loss of radar potential;

- in the second, a half-sum of the carrier frequencies f _g + f _d , before subtracting the d / m frequency offsets f _r with different signs, the half-sum shifted by the target speed by f _d and transferred to the heterodyne f _g , with the suppression of equal frequencies and mirror interference of the earth as well as mirror d / m equal frequencies f _r , too, since their frequencies in the second factor are summed with different signs, and non-mirror noise by subtracting their equal powers with identical frequencies and phases in the receiver mirror channels;

- in the third factor, the frequency d / m f _r with the suppression of non-mirror and identical interference, as well as non-mirror Doppler frequencies.

An expression for two targets in azimuth shows the possibility of resolving them in range - the combination frequencies when subtracting will receive frequencies in the second factor that are different from the Doppler ones and are excluded in the analysis of frequencies.

The drawing shows a functional diagram of the radar NI according to the proposed method.

The signal of the highly stable master oscillator 1 is modulated in the amplitude modulator 2, which provides modulation mirroring, by the LFM signal generator 3 until the targets appear at a constant frequency. At the output of modulator 2, three frequencies appear - two side mirrored and a central one, which is cut out by filter 4, because to implement the "resolution" in range in the proposed method, it is no longer needed. After amplification in the power amplifier 5, two mirror carriers arrive at the radiating antenna 6, from one speaker of which a radiation pattern is provided for one of both carriers.

Part of the signal of the amplifier 5 by the attenuator 7 is selected for filters 8, which separate the carriers along two channels to form a local oscillator 9 and emitted carriers in the mixers 10 and after the local oscillator frequency filters 11 for the receiver.

The signals of two carriers reflected from the targets from the antenna 12 with one horn, i.e. one radiation pattern, through the waveguide filters 13, dividing the carriers into two channels, are fed to the mixers 14, where the difference in carrier frequencies is reduced to the frequency of the local oscillator 9.

After filters 15, the signals are subtracted from one another in the signal subtraction unit 16, where the power divided between the carriers equally during radiation is restored, noise and reflection of the earth, noise and the microwave amplifier, and the transmitter are suppressed in the entire frequency range of the analysis, which increases the sensitivity of the receiver and reduces the limits of notch.

The signal difference is fed to the notch filter 17, where ground reflections near the antenna are suppressed to the required 100-130 dB.

After RZHF 17, the difference signal enters the accumulation filters 18, each of which selects its carrier frequency (see expression 1, multiplication 2), corresponding to the half-sum of the carriers, shifted by the Doppler value, and “rings”, i.e. fixes a certain speed of the target.

After measuring the speed of the target at the command of the computing device, the chirp generator 3 changes its frequency according to a linear law, and the carrier frequencies at the output of the filter 4, in addition, change and mirror.

At the outputs of the filters 18 there will be the same Doppler frequencies, but already modulated in amplitude by d / m, the target frequency difference fr, by which the spectrum analyzer 19 determines the distance to the targets already with reference to speed, and. computing device 20 from its signals generates digital codes of speed and range.

Claims (1)

The method of mirror radar in the radar NR, using linear-frequency modulation of the double sideband of the carriers of the radar signal, separate reception of the sidebands, cutting, determining the radial speed and range with a "resolution", characterized in that, in order to suppress interference, increase rangefinding and lowering the limits of rejection, the carriers modulate the mirror, emit one and take one radiation pattern, subtract one from the other.