RU60272U1 - DEVICE FOR CORRECTION OF INTERCHANNEL DISCONNECTION OF RECEPTION CHANNELS IN DIGITAL HEADLIGHT - Google Patents

Abstract

A device is proposed for correcting the inter-channel mismatch of receiving channels in a digital headlamp containing a pilot divider, a digital adder, a signal processing unit, a digital headlamp including receiving channels containing a serially connected emitter, a directional coupler, and analog and digital receivers. It is characterized in that it further comprises a digital switch, a weight calculator and a noise pilot generator. The introduction of a digital switch, a weight calculator, a noise pilot generator provides: - stability of the antenna pattern, which increases the accuracy of radar coordinate measurements; - separation of the functions of the signal processing tasks, simplifying the construction of the signal processing unit, which increases its performance and simplifies the construction of a digital radar phased array.

Description

The proposed device relates to radar and can be used in radar stations (radar).

Radar systems in which the antenna pattern (BOTTOM) is formed by coherently summing the signals of the receiving channels, its parameters are largely determined by the spread of the gain of the receiving channels and phase errors, as well as the parameters of the elements of the antenna array.

The magnitude of these scatter can so distort the BOTTOM that there will be a deterioration in the directional coefficient (KND) of the antenna and the dynamic range (DD) will decrease.

The digital beamforming method allows one to compensate for the spread of gain and phase errors of channels and to avoid the need to ensure with high accuracy the identity and stability of the amplitude-phase characteristics of the receiving channels.

Correction of inter-channel mismatch is carried out during the period of “silence” of the radar (such a period of time is allotted for functional control (FC)) and the adjustment of the equipment. The adjustment of the equipment is carried out using a pilot signal, which is used as a radiation source. The signals from the reference radiation source are used for calibration and are periodically fed to the inputs of the multi-channel receiving system.

Since the scatter between the channels is of the greatest interest, one of the channels located in the center of the digital phased antenna array (CFAR) is selected as the reference (main) channel. Then the problem of minimizing the difference between the main channel and

channel selected for correction. Minimization is carried out by appropriate adjustment of the weight coefficient W, which leads to a minimum error Δ _min :

Δ _min = U _o -WU _k ,

where U _o is the voltage of the signal of the main channel;

U _to - the signal voltage of the adjustable channel.

These operations are carried out in the signal processing unit (BOS).

Known devices for the correction of inter-channel mismatch of receiving channels of the CFAR [1].

The closest in technical essence and function is a correction device for the inter-channel mismatch of receiving channels in the CFAR proposed by Barton [2], which contains a digital adder, BOS, CFAR, including an emitter, directional coupler, analog and digital receivers selected for the prototype. The structural diagram of the prototype is shown in figure 1.

Such a device has the following disadvantages:

- a continuous radio-frequency signal is used as a pilot signal, to ensure the stability of which an independent tuning system is required, which complicates the equipment, increases cost and reduces reliability;

- estimation of inter-channel mismatch errors, calculation of weighting coefficients, tuning of mismatched receiving channels are performed in the biofeedback, are additional operations and require increasing the productivity of computing tools, which leads to the complication of biofeedback.

The essence of the proposed device lies in the fact that it contains a pilot divider, digital adder, biofeedback, CFAR, including receiving channels that contain a serially connected emitter, directional coupler, analog and digital

receivers. It is characterized in that it further comprises a digital switch, a weight calculator and a noise pilot generator. The noise pilot output is connected to a pilot divider. Two outputs of the digital receiver of each receiving channel are connected to a digital switch. The outputs of the digital switch are connected to a digital adder and to a weight calculator, two outputs of which are connected to a digital adder.

An introduction to the device of a digital switch, a weight calculator, and a noise pilot signal generator provides:

- bottom stability, which increases the accuracy of radar coordinate measurements;

- separation of the functions of the signal processing tasks, simplifying the construction of the biofeedback, which increases the performance of its work and simplifies the construction of CFAR radar.

The essence of the proposed device is illustrated by the structural diagram shown in figure 2.

The proposed device comprises a CFAR 1, a digital switch 2, a weight calculator 3, a pilot signal generator 4, a pilot divider 5, a digital adder 6, a signal processing unit 7.

The digital phased antenna array 1 contains receiving channels 8, including an emitter 9, a directional coupler 10, an analog 11 and a digital 12 receivers.

The emitter 9 is connected to the input of the directional coupler 10, the output of which is connected to the analog receiver 11, and the second input to the pilot divider 5, the input of which is connected to the pilot signal generator 4. Two outputs (x and y) of the digital receiver 12 of each receiving channel 8 are connected to the corresponding inputs of the digital switch 2, the outputs of which are connected to the corresponding inputs of the digital adder 6 and to the inputs of the weighting calculator 3. Two outputs of the calculator

weighting factors 3 are connected to a digital adder 6, the outputs of which are connected to the signal processing unit 7.

The proposed device operates as follows.

As a noise pilot signal, it is proposed to use intrinsic noises similar to the receiving channel of the CFAR. The power of the own noise of the receiving channel is expressed by the formula:

where k is the Boltzmann constant equal to 1.38 · 10 ^-23 J / deg;

T ₀ - absolute room temperature, approximately equal to 300 ° K;

Δf is the frequency band in which noise exists;

To _w - noise figure;

To _M is the gain of the receiving power channel.

As practice has shown, noise pilot devices do not require adaptive control coverage of the correction loop.

The noise signal passes through the analog part of the receiving channel, is digitized and fed to the switch, where branching into two directions is carried out. In one direction, the signal goes directly to the adder, and in the other, through the valveing device, to the equipment for calculating the adjustment coefficients.

In the computer hardware, the weight coefficients are calculated by quadratures, the errors of the inter-channel mismatch are calculated, and the average value of the error value is calculated.

After that, the average value of the error value enters the adder, where it is summed up with the signal of the tuning channel and the resulting amount enters the biofeedback. At this point, the adjustment process ends and the operating mode of the radar sets in. Conditionally, the adjustment operation process is shown in Fig.3.

The structural diagram of the calculator weight tuning factors and errors of the inter-channel mismatch is shown in figure 4.

The work of the calculator begins in the service area with the receipt of the start of operation (HP) pulse at the input of the device. When an HP pulse arrives, a signal is generated in the device, according to which control devices that provide operation in this mode are sent to all devices.

In the first N samples in range (we take N = 16), sixteen samples of the noise pilot signal of the main channel and the channels to be tuned are recorded in random access memory.

At the same time, samples from the channels to be adjusted are fed to the calculation scheme of the normalizing factor α ₁ :

In the next 16 discrete samples, 16 recorded samples from the channels to be adjusted are read from RAM and normalized:

Next, the calculation of the complex weight tuning factors according to the formulas:

After that, the difference in each discrete between the signals of the main channel and the tuning channels is estimated:

and calculates the average value of the difference for the quadrature channels x and y:

The described operations are carried out with each channel to be corrected.

The calculated average values in the operating mode as a correction are received in each adjustable receiving channel of the CFAR.

The operation of the proposed device is shown in Fig.5.

The proposed device calculator for two channels was prokamerovat. Tests have shown positive results. It is accepted for use. As an element base, FPGA FPF10R100AQC was used.

Sources of information taken into account when preparing the application:

1. Forrest Griffiths, Pell Williams, Digital Beamforming for Bistatic Radar Receiver, Inf Conf on Antennas and Propagation, UK, 1983.

2.P. Barton, Digital Beamforming for Radar, IEE Droc, Vol. 127, Pt, No4, Aug. 1980.

Claims (1)

A device for correcting the inter-channel mismatch of receiving channels in a digital phased antenna array containing a pilot divider, a digital adder, a signal processing unit, a digital phased antenna array including receiving channels containing a serially connected emitter, a directional coupler, and analog and digital receivers in that it further comprises a digital switch, a weight calculator and a noise pilot generator, the output of which is connected chen to the input divider pilot signal, the two outputs of the digital receiver each receive lines are connected to respective inputs of a digital switch, the outputs of which are connected to respective inputs of a digital adder and to inputs of calculating weighting coefficients, and two output calculating weighting factors are connected to a digital adder.