KR100418863B1 - Phase matching method using voltage difference between signals in monopulse receiver and phase matching apparatus - Google Patents

Abstract

The present invention relates to a phase matching method and apparatus using a voltage difference of signals in a monopulse receiver, and more particularly, to a monopulse receiver which minimizes a phase error by applying a pilot signal to maximize the voltage difference of a receiver through a phase shifter. A phase matching method and apparatus using a voltage difference of signals.

Phase matching method using the voltage difference of the signals in the monopulse receiver of the present invention comprises the steps of transmitting a predetermined signal from the RF signal generator through the horn antenna; Receiving a signal transmitted from the horn antenna through a pulse antenna and separating the signal into a sum signal (hereinafter referred to as "S signal") and a difference signal (hereinafter referred to as "D signal"); Generating a pilot signal in which a ratio of the D signal to the S signal is constant at a phase matching reference plane, and determining an azimuth angle between the horn antenna and the monopulse antenna; When the pilot signal is input to the 180-degree hybrid circuit, the circuit causes the circuit to receive the S + D signal, which is the S signal + D signal, from the S and D signals transmitted through the sum channel and the difference channel, and the S signal -D Generating an SD signal which is a signal; Measuring a voltage difference between the S + D signal and the S-D signal; Adjusting the phase converter such that the voltage difference is maximized.

Description

PHASE MATCHING METHOD USING VOLTAGE DIFFERENCE BETWEEN SIGNALS IN MONOPULSE RECEIVER AND PHASE MATCHING APPARATUS}

The present invention relates to a phase matching method and apparatus using a voltage difference of signals in a monopulse receiver, and more particularly, to a monopulse receiver which minimizes a phase error by applying a pilot signal to maximize the voltage difference of a receiver through a phase shifter. A phase matching method and apparatus using a voltage difference of signals.

The conventional phase matching method uses a method of measuring and adjusting phase error using a vector network analyzer or a separate phase detection device. However, this conventional method is inefficient in terms of cost because the equipment is expensive, and in a compact and highly integrated receiver, it is difficult to access the front and rear stages of the hybrid, which is the phase matching reference plane, so that the measurement error on the phase is large and the equipment is difficult to set up. Has the disadvantage. In particular, since the measurement is performed at the front end of the hybrid, the accuracy of adjustment is low because the error occurring between the input channels of the hybrid is not compensated.

In addition, methods of increasing the ease of adjustment by placing a combiner or power divider in the path of each channel include phase errors caused by the combiner or power divider element itself and the phase error caused by the on-channel arrangement and loss of signal during normal operation. Has the disadvantage of increasing.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and an object of the present invention is to simply remove a phase error by measuring a power difference or a voltage difference of signals without a vector network analyzer or a separate phase detection device.

In addition, an object of the present invention is to improve the accuracy of the phase adjustment by enabling the compensation of the phase error even in a small and highly integrated system.

In addition, an object of the present invention is to accurately remove a phase error in a monopulse receiver and to minimize the azimuth estimation error of the monopulse receiver.

1 is a basic configuration diagram of a monopulse receiver.

FIG. 2 is an error diagram illustrating an error between channels of the monopulse receiver of FIG. 1.

3 shows the change of the monopulse slope due to the phase error.

4 is a block diagram of an apparatus for applying a pilot signal.

5 is a graph showing a sum pattern and a difference pattern of a monopulse antenna.

6 is a graph showing the relationship between the voltage difference and the phase error according to the ratio of the difference signal to the sum signal.

Phase matching method using the voltage difference of the signals in the monopulse receiver of the present invention comprises the steps of transmitting a predetermined signal from the RF signal generator through the horn antenna; Receiving a signal transmitted from the horn antenna through a pulse antenna and separating the signal into a sum signal (hereinafter referred to as "S signal") and a difference signal (hereinafter referred to as "D signal"); Generating a pilot signal in which a ratio of the D signal to the S signal is constant at a phase matching reference plane, and determining an azimuth angle between the horn antenna and the monopulse antenna; When the pilot signal is input to the 180-degree hybrid circuit, the circuit causes the circuit to receive the S + D signal, which is the S signal + D signal, from the S and D signals transmitted through the sum channel and the difference channel, and the S signal -D Generating an SD signal which is a signal; Measuring a voltage difference between the S + D signal and the S-D signal; Adjusting the phase converter such that the voltage difference is maximized.

In addition, the phase matching device using the voltage difference of the signals in the monopulse receiver of the present invention includes a horn antenna for receiving and transmitting a signal generated from the RF signal generator; A monopulse antenna which receives a signal transmitted from the horn antenna and separates the signal into a sum signal (hereinafter referred to as "S signal") and a difference signal (hereinafter referred to as "D signal"); A sum signal channel and a difference signal channel for transmitting the S and D signals, respectively; A phase converter connected to one of the channels; A 180-degree hybrid circuit which receives the output of the phase converter and the output of the other of the channels and outputs a first signal consisting of a sum signal + a difference signal and a second signal consisting of a sum signal and a difference signal; A first channel and a second channel for transmitting the first signal and the second signal, respectively; And a signal processor that measures the voltage difference between the output of the second channel at the output of the first channel.

1 is a basic configuration diagram of a monopulse receiver. A monopulse antenna (not shown) applies a signal (video signal, audio signal, etc.) including various information to the monopulse receiver of FIG. 1. The monopulse receiver separates the signal into a sum signal (hereinafter referred to as "S signal") and a difference signal (hereinafter referred to as "D signal"). The S and D signals each include a receive protector such as TR-Limiter attenuators 10a and 10b, an RF circuit such as band pass filters 11a and 11b, and low noise amplifiers 12a and 12b. Is passed through the phase converter 13a and the bi-phase converter 13b to the two inputs of the 180 degree hybrid circuit 14. The 180-degree hybrid circuit 14 receiving the S and D signals synthesizes an S + D signal, which is an S signal and a D signal, and an SD signal, which is an S signal and a D signal, respectively, and amplifiers 15a and 15b, respectively. And amplified, the IF signal from the low frequency oscillator 16 is mixed with the frequency mixers 17a and 17b and passed through the band pass filters 18a and 18b. Further, the log amplifiers 19a and 19b are passed through to apply the applied S + D signal, the voltage corresponding to the power of the SD signal (the voltage V _{S + D of the S + D} signal, and the voltage of the SD signal). (V _SD )) and output the signal to a signal processor (not shown) at the rear end of the receiver, so that the signal processor obtains a (V _SD / V _{S + D} ) signal which is a monopulse error signal. The (V _SD / V _{S + D} ) signal indicates angle information of the target.

An ideal 180 ° hybrid first input signal distributes the two output signals so that they are in phase, and the second input signal is an ultra-high frequency passive device that distributes the signals so that the two output signals have a 180 ° phase difference. However, a commercially available 180 ° hybrid circuit is modeled as a circuit that includes gain and phase imbalances for both inputs and two outputs, as in the model of 180 ° hybrid circuits included in the interchannel error model of FIG.

FIG. 2 is an error diagram illustrating the channel-to-channel error of the monopulse receiver of FIG. 1, and includes both the inter-channel gain and phase error that may occur in each part of the antenna and the receiver. The error of the antenna is phase error (without gain error) Consider only). The reason for this is that since the antenna pattern itself expresses gain for azimuth, the gain error can be said to be included in the pattern. The phase error ( ) Is a phase error between the sum signal and the difference signal output from the antenna. The error of the monopulse receiver can be divided into three parts. The monopulse receiver includes a sum, a difference channel, a 180 ° hybrid circuit, a sum + difference, and a sum-difference channel.

The error between the sum channel and the difference channel is mainly due to the inhomogeneity of the RF circuits such as the reception protectors 10a and 10b, the bandpass filters 11a and 11b, the low noise amplifiers 12a and 12b, and the like. By the gain error to G _B and the phase error to Represented by. In addition, the gain error and the phase error of the input channel in the 180-degree hybrid circuit 14, respectively, G _HI , The gain error and phase error of the output channel are G _HO , The gain error and phase error of the sum + difference channel and the sum-difference channel are represented by G _C , Represented by.

Here, the rear end of the ideal 180 ° hybrid of FIG. 2 shows that the signal of the rear end of the hybrid eventually loses phase information by the log amplifiers 19a and 19b disposed at the IF end of the receiver. It can be seen that only those occurring at the front end of can affect the performance of the monopulse.

Therefore, the component of the inter-channel phase error affecting the performance of the monpulse is On the sum and difference channels And the 180 degree hybrid circuit 14 It can be divided into three components, the total phase error before synthesis in the ideal 180-degree hybrid circuit, that is, the total phase error (Θ) in the phase matching reference plane is expressed by Equation 1 below.

3 shows the change of the monopulse slope due to the phase error, the horizontal axis represents the azimuth of the target, and the vertical axis represents the estimated azimuth extracted from the target signal applied at each azimuth. As shown in FIG. 3, the larger the phase error PE, the slower the monopulse slope, and accordingly, the larger the error of the estimated angle.

The sum signal and the difference signal applied to the ideal 180 ° hybrid in the phase match reference plane of FIG. 2 are represented by Equation 2 below.

The output signal synthesized at an ideal 180 ° hybrid is represented by the following equation (3).

In summary, Equation 3 is expressed as Equation 4 below.

Through the amplifiers 15a, 15b, the frequency mixers 17a, 17b, the band pass filters 18a, 18b, and each of the signals input to the log amplifiers 19a, 19b, It is expressed as Equation 5 below.

When Equation 5 is converted into electric power, it is expressed as Equation 6 below.

I / O relationship between log amplifiers 19a and 19b having a slope of 25 mV / dB and a transfer characteristic that changes the input power P _in from -80 dBm to 0 dBm into an output voltage V _out of 0-2 V. Is shown in Equation 7 below.

Therefore, the voltages of the output signals passing through the log amplifiers 19a and 19b are expressed by Equation 8 below.

The voltage difference between channels is shown in Equation 9 below.

The first term of Equation 9 represents the gain difference between channels existing at the rear end of the ideal hybrid circuit and is a function of the ratio of θ, S signal and D signal.

Therefore, if the gain difference between the channels after the hybrid circuit is obtained and the ratio of the S signal and the D signal applied to the hybrid circuit is known, the phase error θ at the phase match reference plane can be obtained.

4 is a block diagram of an apparatus for applying a pilot signal. In front of the receiver of Fig. 1, an RF signal generator 41, an horn antenna 42, and a monopulse antenna 43 are additionally provided, and the oscilloscope measures the voltage difference between the output voltages of the log amplifiers 50a and 50b. Observation can be made through (51). The pilot signal is a test signal for forming a specific ratio of the S signal and the D signal in the phase matching surface of the receiver. The pilot signal measures the gain error between the antenna pattern and the channel of the receiver, and then measures the azimuth angle between the monopulse antenna and the horn antenna. May be applied to the receiver. When a pilot signal is applied to the receiver, the signals received by the 180 degree hybrid circuit 46 are synthesized.

Θ at the phase match reference plane Considering that the adjustment to 0 ° is a concept of the phase adjustment of the system, the voltage difference between the channels for the phase error according to the ratio of the S signal and the D signal is shown in FIG.

5 is a graph showing the relationship between the voltage difference and the phase error according to the ratio of the D signal to the S signal. The vertical axis represents the voltage difference of the signal which is the final output of the receiver, and the horizontal axis represents the phase error [theta], and shows the correlation when the ratio of the S signal / D signal is 1 dB, 2 dB, 3 dB, 4 dB and 5 dB. It can be seen that the smaller the phase error θ, the larger the voltage difference of the signal which is the receiver final output, and the closer the phase error θ to 90 °, the smaller the voltage difference. Also, the smaller the ratio of the D signal to the S signal is, the larger the slope of the curves increases, so that the change in the voltage difference with respect to the phase error [theta] becomes larger. Causes a more sensitive voltage difference change.

The phase error between the sum channel and the difference channel changes the monopulse slope, which increases the estimation error for the azimuth angle and the angular tracking error, greatly reducing the receiver's performance. Therefore, a phase shifter 45 capable of compensating for phase error between channels should be arranged in one channel (sum channel or difference channel), as shown in FIG.

As a result, in order for the signal of the same magnitude to be applied to the two inputs of the phase matching plane, the gain between channels of the antenna consisting of the sum pattern and the difference pattern (described in FIG. 6 below) and the phase matching plane existing in the receiver Error is measured and the azimuth angle of FIG. It is important to set the azimuth angle of the horn antenna by calculating

Using the measured values of the actually implemented system, the pattern of the monopulse antenna is shown in FIG. 6. Line I is the pattern of the sum signal measured at the output of the antenna, line II is the pattern of the difference signal measured at the output of the antenna, and line (III) is the pattern of the difference signal measured at the phase matching plane. Indicates. That is, in the graph, the vertical axis represents the relative magnitude of the sum signal and the difference signal applied to the receiver at any azimuth angle when the signal is emitted to the monopulse antenna using the horn antenna, and the horizontal axis is the horn antenna and the monopulse antenna. Azimuth angle between ).

The measurement values for the aforementioned channel error are shown in Table 1 below.

Item Measures Gain error between sum and difference channels (G _B ) -2.0 dB Gain error (G _HI ) between input channels in a 180-degree hybrid circuit +0.5 dB Gain Error (G _HO + G _C ) _Behind Ideal 180-Degree Hybrid Circuit +2.5 dB

The channel-to-channel gain error (G _B -G _HI ) from the input terminal of the receiver to the phase matching plane is -2.5 dB, and this value is smaller than the gain of the sum channel by 2.5 dB compared with the gain of the sum channel. Even if the same signal is applied to the signal, the magnitude of the D signal is reduced by 2.5 dB compared to the S signal due to the gain error between the channels.

In FIG. 6, point A is the case where the magnitude of the S signal and the D signal at the input terminal of the receiver are the same, and point B is the case where the magnitude of the S signal and the D signal are the same in the phase matching plane. Thus, the azimuth angle of FIG. ) Is about 3.6 °, which is the horizontal coordinate of the point B, in which the S and D signals of approximately the same magnitude are measured in the phase matching plane of the receiver.

As shown in FIG. 4, the RF signal generator is set to a frequency to be matched, and the voltage difference between the signal of V _{S + D which} is the final output of the receiver and the signal of V _SD using the oscilloscope 51 is set. By adjusting the phase shifter 45 until Equation 9 becomes the largest value in the positive direction, an adjustment point having a phase error θ of 0 ° can be found. At this time, the gain error (G _HO + G _C ) at the rear end of the ideal 180-degree hybrid circuit measured in Table 1 is included in the voltage difference as shown in Equation 9, but in the adjustment method for finding the maximum value, it is expressed as a constant value. Therefore, the accuracy of the adjustment is not affected.

According to the present invention, it is necessary to remove the phase imbalance from the antenna to the receiver, and simply eliminate the phase error by measuring the power difference or voltage difference of the IF stage without a vector network analyzer or a separate phase detection device. It can work.

In addition, the present invention can be applied to a radar system that is not only cost-effective but also compact and highly integrated such that it is impossible to access a hybrid, and can compensate for phase errors occurring in the device itself that synthesizes a signal such as 180 ° hybrid. Therefore, the accuracy of phase adjustment can be improved. Therefore, the present invention has the effect of accurately eliminating the phase error occurring in the two-channel monopulse system and eventually minimizing the azimuth estimation error of the monopulse system.

Claims (9)

Transmitting a predetermined signal from an RF signal generator through a horn antenna; Separating the signal transmitted from the horn antenna into a sum signal (hereinafter referred to as "S signal") and a difference signal (hereinafter referred to as "D signal") through a monopulse antenna; Generating a pilot signal in which a ratio of the D signal to the S signal is constant at a phase matching reference plane, and determining an azimuth angle between the horn antenna and the monopulse antenna; When the pilot signal is input to the 180-degree hybrid circuit, the circuit causes the circuit to receive the S + D signal, which is the S signal + D signal, from the S and D signals transmitted through the sum channel and the difference channel, and the S signal -D Generating an SD signal which is a signal; Measuring a voltage difference between the S + D signal and the S-D signal; And adjusting the phase shifter to maximize the voltage difference. The method of claim 1, wherein the phase shifter is connected to one of the sum channel or the difference channel. The method of claim 1, wherein the method comprises generating the S + D and SD signals, wherein the S + D and SD signals comprise a first channel and a second channel, each consisting of an amplifier, a frequency mixer, and a bandpass filter. Phase matching method using the voltage difference of the signals in the monopulse receiver further comprising the step of transmitting through. 4. The voltage difference of signals in a monopulse receiver according to claim 1 or 3, wherein the method further comprises passing a log amplifier to convert the power of the S + D and SD signals into voltage. Phase matching method using The phase matching method of claim 1, wherein the pilot signal has a ratio of the D signal to the S signal in a range of −5 dB to +5 dB. The method of claim 1, wherein the phase matching reference plane is determined to include a gain error and a phase error between channels of an input portion of the 180 degree hybrid circuit. A horn antenna for receiving and transmitting a predetermined signal from an RF signal generator; A monopulse antenna for separating the signal transmitted from the horn antenna into a sum signal and a difference signal; A sum signal channel and a difference signal channel for transmitting the sum signal and the difference signal, respectively; A phase converter connected to one of the channels; A 180-degree hybrid circuit which receives the output of the phase converter and the output of the other of the channels and outputs a first signal consisting of a sum signal + a difference signal and a second signal consisting of a sum signal and a difference signal; A first channel and a second channel for transmitting the first signal and the second signal, respectively; And a signal processor for measuring a voltage difference between the output of the second channel at the output of the first channel. 8. The phase matching device of claim 7, wherein the first channel and the second channel each include a log amplifier. 8. The phase matching device of claim 7, wherein the signal processor is an oscilloscope.