RU2533198C1 - Method of controlling radar station resolution - Google Patents

Abstract

FIELD: physics, navigation.

SUBSTANCE: invention can be used in radar stations for controlling resolution thereof. The present method is based on generating a continuous frequency-modulated signal, emitting said signal in space, receiving a reflected signal and conversion thereof to an intermediate frequency using a homodyne method. For wide variation of the resolution of a radar station, modulation of the generated signal is repeated in each operating cycle, wherein the cycle duration is determined from the given range of the radar station and the given resolution. The given resolution is then used to determine the corresponding time of the end of emission, and the reflected signal is received in the time remaining until the end of the operating cycle, wherein the received reflected signal and the generated frequency-modulated signal are converted to an intermediate frequency using a homodyne method. The value of the intermediate frequency is proportional to the distance to the reflector.

EFFECT: variation of resolution of a radar station in a wide range.

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Description

The invention relates to radar and can be used in radar stations to control their resolution. Currently known methods of achieving high resolution in range in radar stations. These methods are based on the use of probing signals with a wide frequency spectrum, which requires a wide bandwidth in the receiving channel of the radar and is associated with an increase in the harmful effect of external noise and internal noise of the receiving channel on the achievable radar characteristics.

At the same time, there are known methods for constructing continuous-wave radars, the receiving channels of which are built on the principle of the so-called homodyne reception, when a continuous transmitter signal is used as the heterodyne voltage in the receiver. This allows you to narrow the bandwidth of the receiving channel compared to the spectrum width of the probing signal, reduce noise and noise, and reduce the sampling frequency of the ADC in digital processing circuits.

The well-known "Method of resolving range targets by a radar station and a pulsed radar station with pulse compression and signal recovery" (RU 2296345 C2, IPC G01S 13/42, published March 27, 2007). It consists in the fact that the transmitting antenna of the station emits complex probing signals with in-pulse frequency modulation or phase shift keying generated by the transmitter The receiving antenna of the station receives the reflected signals, in the receiving path for each pulse repetition period the received signals are filtered in -consistent filter detector in a decision of detection signals produced in the calculator and determination of distance to the target. Moreover, to detect at each pulse repetition period signal in addition to a matched filtering is performed after pulse compression filter reducing signal recovery.

Closest to the technical nature of the proposed method is the "Method and system for radar measurement of speeds and coordinates of objects (options)" (RU 2255352 C2 publ. 02.10.2005, IPC G01S 13/42), which includes radiation or radiation periodically modulated in frequency of the probing signal, receiving signals reflected from objects, multiplying the emitted and received signals, amplification obtained as a result of multiplying the homodyne signal. Next, linear and analog-to-digital transformations of the homodyne signal form an intermediate frequency signal in the form of a sequence of digital fragments of a given duration, form the main two-dimensional matrix of basic signals, each of which simulates the expected homodyne signal, the column numbers of the matrix of basic signals correspond to a set of average expected range values, and the numbers strings - the set of average expected values of the speed of reflecting objects, calculate the sequence of basic matrixes of values cross-correlation functions of the matrix of basic signals and each of the fragments of the intermediate frequency signal, detect objects by identifying the elements of the matrix of cross-correlation functions of any fragment whose values exceed a predetermined threshold level, and determine the range and speed of the detected objects by the numbers of the column and row of the detected elements, respectively.

The disadvantage of such methods is the unavoidable effect of a spurious signal that seeps directly from the transmitting channel to the input of the receiving one. The options associated with the use of automatic compensation schemes for this penetrating signal to acceptable levels are complex, they are unstable and critical, especially in medium and long range radars. The situation does not save the transition to the use of separate antennas for reception and transmission, since the isolation between the nearby transmitting and receiving antennas is insufficient and depends on the re-reflections of the emitted signal on objects surrounding the antenna. Therefore, homodyne reception methods are used in short-range radars, for example, in automobile collision avoidance radars and police radars, in which the level of radiation and, accordingly, the level of continuous leaking signal is very low.

The technical result of the invention is to eliminate the disadvantages of continuous radar, which uses the homodyne method of receiving reflected signals, in the wide range of possible to change the resolution of the radar by choosing the optimal ratio between the duration of the probe radiation and the interval of reception of reflected signals.

The essence of the proposed method for controlling the magnitude of the resolution of a radar station is that it is based on the generation of a continuously modulated frequency signal, emitting this signal into space, receiving the reflected signal and converting it to an intermediate frequency using the homodyne method.

New in the proposed technical solution is the repetition of the modulation of the generated signal in each cycle of the radar station, and the cycle duration is determined by the given radar range and the specified resolution, then the corresponding end time of the radiation is determined by the given resolution, and the reflected signal is received in the remaining until the end of the clock cycle, time, and the received reflected signal and the generated modulated frequency signal are converted to intermediate frequency homodyne method. The value of the intermediate frequency is proportional to the distance to the reflector.

Figure 1 shows a functional diagram that implements the claimed method of controlling the magnitude of the resolution of the radar station.

2

a) the dependence of the frequency f _gene (t) of the generated signal on time;

b) - plot of the generated voltage U _gene (t);

c) - shows the filling frequency of the emitted pulse;

g) - shows the plot of the emitted pulses;

d) - shows the time dependence of the frequency of the reflected signal f _CR and the local oscillator signal f _get .

f) - shows the dependence of the frequency of the signal in the IFA from time to time;

A functional diagram that implements the claimed method of controlling the magnitude of the resolution of the radar station consists of a master frequency modulator 1, an intermediate frequency amplifier (UPC) 2, a key 3, an antenna 4, a mixer 5.

The processes explaining the proposed method can be conveniently represented in three interconnected stages: the stage of generation of a continuously continuous frequency-modulated signal by the generator 1, the stage of its emission over time T ₁ and, thus, the actual stage of emission of the pulse sounding signal by antenna 4. The radiation stage ends with opening the key. This is followed by the step of receiving the reflected signal, in which the antenna 4, mixer 5, and OPC 2 are involved. The temporal characteristics corresponding to these steps are shown in Fig. 2 (a-d).

The generation stage corresponds to the generation of a continuous signal in time, in which the frequency varies linearly within certain limits during the time interval (cycle) 0 ... T. The value of T is determined based on the given range of the radar and the specified resolution ΔR according to the formulas

, $${\text{ Т}}_{\text{1}}=\frac{с}{2к\Delta R}$$

$$T=\frac{2R_{m\mathrm{but}\mathrm{to}\mathrm{from}}}{c}+T_{\mathrm{one}}$$

, $${\text{T}}_{\text{one}}=\frac{\mathrm{from}}{2\mathrm{to}\Delta R}$$

where c is the speed of light, k is the steepness of the frequency modulation

Upon reaching time T, the linear frequency modulation process is repeated. In radiation mode, apart from generator 1, the key K in its closed state and antenna 4 also participate. At time T ₁ (T ₁ <T), the key K opens, as a result of which a probe pulse with a duration of T ₁ and a frequency deviation f ' _{max is} emitted into the LFM - f _min The process of pulsed radiation is shown in figv,

, где R_ц - расстояние до отражателя. На этапе приема отраженных сигналов от отражателя, удаленного на расстояние R_ц от РЛС, приемная антенна будет принимать сигналы того же вида, что и на этапе излучения фиг.2в, г, но с запаздыванием во времени на величину $$t_3=\frac{2R_{ц}}{с}$$

. Отраженные сигналы начинают поступать на первый вход смесителя 5 в момент времени Т₁, в то время как на второй вход смесителя 5 поступает сигнал непрерывно работающего ЛЧМ генератора 1 в качестве сигнала гетеродина.The step of receiving the reflected signals begins at time T ₁ . The reflected signals received by the antenna 4 are fed to the first input of the mixer 5, while the signal of the continuously working LFM generator 1 is received as the local oscillator signal at the second input of the mixer 5. The received signals are identical in structure to the emitted probe pulses, but have time delays equal $$t_{}$$$${}_3=2\frac{R_c}{\mathrm{from}}$$

where R _c - the distance to the reflector. At the stage of receiving reflected signals from the reflector, remote at a distance R _c from the radar, the receiving antenna will receive signals of the same type as at the radiation stage of FIGS. 2c, d, but with a time delay of $${\mathrm{<figure-callout\; id="3"\; label="t"\; filenames="00000007.png"\; state="\{\{state\}\}">t</figure-callout>}}_3=\frac{2R_c}{\mathrm{from}}$$

. The reflected signals begin to arrive at the first input of the mixer 5 at time T ₁ , while the second input of the mixer 5 receives a signal from a continuously working LFM generator 1 as a local oscillator signal.

On 2E shows the time dependence of the reflected signal _pr frequency f and the signal f LO _het. At the output of the mixer 5 with the help of the amplifier 2, a signal of the difference (intermediate) frequency, called the homodyne frequency, is allocated, the value of which is proportional to the distance to the reflector.

до R_мах множества отражателей на выходе УПЧ появится множество радиоимпульсов одинаковой длительности с разными, но постоянными частотами заполнения. Разделение этих импульсов, которое обеспечивает техника спектрального анализа сигналов, определяет разрешающую способность РЛС по дальности, которая оказывается обратно пропорциональной величине Т₁. Поэтому в предлагаемом способе управление величиной разрешающей способности производят изменением длительности зондирующего импульса.If there is a range of $$\frac{\mathrm{from}{T}_{\mathrm{one}}}{2}$$

up to R _{max of a} plurality of reflectors, a number of radio pulses of the same duration with different but constant filling frequencies will appear at the output of the amplifier. The separation of these pulses, which is provided by the technique of spectral analysis of signals, determines the radar resolution in range, which turns out to be inversely proportional to the value of T ₁ . Therefore, in the proposed method, the resolution value is controlled by changing the duration of the probe pulse.

Claims (1)

A method of controlling the magnitude of the resolution of a radar station, based on the generation of a continuous frequency-modulated signal, radiation into the space of this signal, receiving the reflected signal and converting it to an intermediate frequency, characterized in that the frequency modulation of the generated signal is repeated in each cycle of the radar station, the tact duration is limited by a given radar range and a given resolution, then by a specified resolution with individuality define its corresponding radiation closure time, and reception of the reflected signal to produce the remainder of closure cycle operation time, and the received reflected signal and generated signal is modulated in frequency is converted to an intermediate frequency homodyne method.

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