RU2821006C1 - Quadrature phase direction finder using signal from output of one of antennae as heterodyne - Google Patents

Abstract

FIELD: physics.

SUBSTANCE: quadrature phase direction finder is intended for detection and high-precision measurement of bearing of radiating objects. To obtain the first quadrature, the output of the first antenna through the first low-noise amplifier is connected to the heterodyne (HET) inputs of first group 1…N-1 of balance mixers, to obtain a second quadrature, the output of the first antenna is connected through the first low-noise amplifier and the phase shifter to the HET inputs of second group 1…N-1 of balance mixers, outputs of two groups of balanced mixers 1…N-1 are connected via electronic switches with two inputs of analogue-to-digital converters of microcontroller.

EFFECT: enabling direction-finding of radio signal sources in a wide frequency band without readjustment of the device and use of significant computational resources.

1 cl, 5 dwg

Description

The quadrature phase direction finder is designed for detection and high-precision measurement of the bearing of emitting objects and can be used in radar tasks, in security systems, and in search operations of the Ministry of Emergency Situations.

Known devices for phase direction finding of emitting objects, for example, RF patent No. 2208808, publ. 07/20/2003, for the invention “Omnidirectional direction finder” and USSR copyright certificate No. 1190748, publ. 09/20/1999, for the invention “Phase direction finder”.

The closest device to the claimed one is a phase direction finder, RF patent No. 2365931, publ. 08/27/2009. The known phase direction finder contains a first receiving antenna, a first receiver, a mixer connected in series, the second input of which is connected to the output of the local oscillator, an intermediate frequency amplifier, a first multiplier, a first bandpass filter, a delay line, a second phase detector, the second input of which is connected to the output of the first bandpass filter , a 90-degree phase shifter, a first phase detector, the second input of which is connected to the second output of the reference oscillator, and an indicator, a sequentially connected reference oscillator, a pulse generator, an electronic switch, n inputs of which are connected to n outputs of receiving antennas located in a circle of radius d with the possibility of their electronic rotation around the first receiving antenna located in the center of the circle, and the second receiver, the output of which is connected to the second input of the first multiplier, the second multiplier, the second bandpass filter and the third phase detector, the second input of which is connected in series to the output of the first bandpass filter. the third output of the reference generator, and the output is connected to the second input of the indicator; at each switching, two of n receiving antennas are simultaneously used, located at the ends of the diameter of the circle along which they are installed, ensuring a doubling of the relative size of the measuring base, while to the second output The electronic switch is connected in series to a third receiver, a third multiplier, the second input of which is connected to the output of the intermediate frequency amplifier, and a third bandpass filter, the output of which is connected to the second input of the second multiplier.

The disadvantage of this device is that to obtain an intermediate frequency, a local oscillator with a reference oscillator is used, which does not allow signals of the same frequency to be obtained at the input of the mixers. It is not clear from the description of the known device how the output signals are processed to determine the bearing.

This drawback is eliminated in the claimed invention “Quadrature phase direction finder”.

The technical challenge of the proposed quadrature phase direction finder is the ability to find direction of radio signal sources in a wide frequency band without rebuilding the device and using significant computing resources.

The stated problem in the inventive quadrature phase direction finder containing N broadband antennas, N broadband low-noise amplifiers (LNA), two groups of N-1 output balanced mixers, a phase shifter, two electronic switches connecting the outputs of N-1 balanced mixers with the inputs of analog-to-digital converters microcontroller, and the outputs of antennas 2...N through LNA 2...N are connected to radio frequency (RF) inputs of both groups of balanced mixers 1...N-1, is solved due to the fact that to obtain the first quadrature, the output of antenna 1 through LNA 1 is connected to heterodyne ( GET) inputs of the first group 1...N-1 balanced mixers, to obtain the second quadrature, the output of antenna 1 through LNA 1 and a phase shifter is connected to the GET inputs of the second group 1...N-1 balanced mixers, the outputs of two groups of balanced mixers 1...N-1 are connected through electronic switches with two inputs of analog-to-digital converters of the microcontroller.

The essence of the proposed technical solution is illustrated in Fig. 1-5. In FIG. Figure 1 shows a functional diagram of a quadrature phase direction finder. The named direction finder (Fig. 1) contains N broadband antennas, N broadband low-noise amplifiers LNA, two groups of N-1 output balanced mixers (CM 1 ... CM N-1), a 90-degree phase shifter (PF at 90), two electronic switches (Switch 1 and Switch 2), connecting the outputs of N-1 balanced mixers with the inputs of analog-to-digital converters of the microcontroller ADC1 and ADC2. In this case, the outputs of the antennas 2...N through the LNA 2...N are connected to radio frequency (RF) inputs (RF inputs are not indicated in Fig. 1) of both groups of balanced mixers 1...N-1. To obtain the first quadrature, the output of antenna 1 through the LNA 1 is connected to the heterodyne (GET) inputs (GET inputs are not indicated in Fig. 1) of the first group 1...N-1 of balanced mixers (CM 1...CM N-1), to obtain the second quadrature the output of antenna 1 through LNA 1 and the phase shifter is connected to the GET inputs of the second group 1…N-1 balanced mixers (CM 1…CM N-1), the outputs of two groups of balanced mixers 1…N-1 are connected through electronic switches (Switch 1 and Switch 2) with two inputs of analog-to-digital converters (ADC1 and AT2) of the microcontroller.

A significant advantage of this solution is the possibility of direction finding of radio signal sources in a wide frequency band without rebuilding the device and using significant computing resources. This is achieved by the fact that to obtain the first quadrature, the output of antenna 1 through LNA 1 is connected to the heterodyne (GET) inputs of the first group of 1..N-1 balanced mixers, to obtain the second quadrature, the output of antenna 1 through LNA 1 and the phase shifter is connected to the GET inputs of the second groups 1..N-1 of balanced mixers, the outputs of two groups of balanced mixers 1..N-1 are connected through electronic switches with two inputs of analog-to-digital converters of the microcontroller. As a result, the signals at the local oscillator and RF inputs have the same frequency even when the frequency of the input signals changes. To ensure the possibility of direction finding, the type of signals at the output of the mixers must be similar for different frequencies and signal levels at the inputs.

In order to check this situation, a prototype of a quadrature phase direction finder board (Fig. 1) with two antennas was made. When N=2 (number of antennas), switches at the output of balanced mixers are not required. Please note that all components of the development board are exclusively Russian-made.

The change in the phase difference at the input of antenna 2 relative to the base antenna 1 was achieved by using delay lines, which were cable inserts of different lengths; the magnitude of the phase change was measured with a phase meter.

An analysis of the similarity of the amplitude-phase characteristics of the quadrature phase direction finder at different frequencies of the input signal was carried out and was studied for both quadratures.

In FIG. Figure 2 shows the amplitude-phase characteristic of a quadrature phase direction finder, made according to the functional diagram (Fig. 1) at N = 2, for the first quadrature at frequencies of 1.2 and 1.3 GHz and power -25 dBm (triangular markers indicate frequency 1.2 GHz, square markers indicate frequency 1.3 GHz).

In FIG. Figure 3 shows the amplitude-phase characteristic of a quadrature phase direction finder, made according to the functional diagram (Fig. 1) at N = 2, for the second quadrature at frequencies of 1.2 and 1.3 GHz and power -25 dBm (triangular markers indicate frequency 1.2 GHz, square markers indicate frequency 1.3 GHz).

As can be seen from FIG. 2, 3, the quadrature shapes depending on the phase difference at the antenna inputs for different frequencies are similar. A phase shift occurs when the frequency of the input signal changes.

An analysis of the similarity of the amplitude-phase characteristics was carried out at different input signal powers at the same frequency for two quadratures.

In FIG. Figure 4 shows the amplitude-phase characteristic of the first quadrature of the phase direction finder, made according to the functional diagram (Fig. 1) at N=2 for a frequency of 1.1 GHz with an input signal power of -25 dBm and -28 dbm.

In FIG. Figure 5 shows the amplitude-phase characteristic of the second quadrature of the phase direction finder, made according to the functional diagram (Fig. 1) at N=2 for a frequency of 1.1 GHz with an input signal power of -25 dBm and -28 dbm.

As can be seen from FIG. 4, 5 the quadrature shapes depending on the signal power at the antenna inputs are similar. Has scaling of the amplitude-frequency response when changing the input signal power.

Thus, we have shown that it is possible to find direction of radio signal sources in a wide frequency band without adjusting the direction finder. This is achieved by ensuring that the signals at the local oscillator inputs and the RF inputs of the mixers always have the same frequency. The amplitude-phase characteristic of the receiver retains its similarity when the frequency and power of the input signal changes, and the joint analysis of two quadratures in the microcontroller makes it possible to unambiguously determine the direction of the radio emission source.

Claims (1)

Quadrature phase direction finder containing N broadband antennas, N broadband low-noise amplifiers (LNA), two groups of N-1 output balanced mixers, a phase shifter, two electronic switches connecting the outputs of two groups of N-1 balanced mixers with the inputs of analog-to-digital converters of the microcontroller , and a microcontroller in which the outputs of antennas 2...N through LNA 2...N are connected to radio frequency (RF) inputs of both groups of balanced mixers 1...N-1, characterized in that to obtain the first quadrature the output of antenna 1 through LNA 1 is connected to heterodyne (GET) inputs of the first group 1...N-1 balanced mixers, to obtain the second quadrature, the output of antenna 1 through LNA 1 and a phase shifter is connected to the GET inputs of the second group 1...N-1 balanced mixers, outputs of two groups of balanced mixers 1...N-1 connected via electronic switches to two inputs of analog-to-digital converters of the microcontroller.