JPH01224683A - Azimuth detecting and receiving device - Google Patents

Abstract

PURPOSE:To obtain the device which need not be uniformized in phase characteristics of a mixer and an IF amplifier, the length of a signal path, etc., by providing a switch circuit which connects the outputs of two antennas and the input of a reception system in a parallel or crossing state on the output sides of the antennas. CONSTITUTION:The arrival signal from one signal source is received by the two antennas 1a and 1b which are so arrayed as to receive the signal according to an arithmetic expression having phase shift relation and the reception system, and the azimuth of the arrival signal is found by solving the arithmetic expression from the signal phases of the two antennas with the output of the reception system. Then, the transfer switch 11 is provided on the output sides of the antennas 1a and 1b to connect the two antennas 1a and 1b and the input of two reception systems in parallel or crossing relation. Consequently, phase errors that the reception systems have cancel each other, the signal paths of the reception systems need not be equal in length, and azimuth detection which use phases is easily performed.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to an azimuth detection receiving device that attempts to detect the arrival direction of a received signal using its phase difference.

[Conventional technology]

Figure 6 shows, for example, SKOLNIK = iF
“Radar Handbook”
) This is a conventional example that takes up the case of a direction finding receiver using radar phase comparison described on pages 21 to 27, excluding the transmission system. In this figure, 1 is an antenna, 2
3 is a mixer, 3 is a local oscillator, 4 is an IF amplifier, 5 is a phase detector, and 6 is an arithmetic circuit.

Next, the operation will be explained. Two antennas 1a and 1b
are arranged in parallel at a distance of d, and both phase patterns are aligned. Since the antenna is installed so that both phases are equal when receiving radio waves from the front direction, if the signal is received from a direction that differs by the azimuth angle θ, the phase difference ψ of the antenna output will decrease. It is a well-known fact in this field that the equation can be obtained as shown in the equation.

where λ is the free space wavelength of the received signal. This relationship can be concretely explained with reference to FIG. Distance from antenna 1a to target: R1 and distance from antenna 1b to target:
R2 is considered to reach the target at a very long distance, almost in parallel, and with a flat wavefront.
- R1= R+ -sinθ ・(21R2
= R--sin θ (3). Therefore, it can be explained by the fact that the phase difference in equation (11): ψ is caused by the difference between the distances R1 and R2.

In FIG. 6, this phase difference is expressed by two series of mixers 2a.

2b, a fixed frequency local oscillation signal is injected from the local oscillator 3, mixed, and converted into an intermediate frequency signal (hereinafter referred to as an IF multiplied signal). Since the signal from the local oscillator 3 is injected into the mixers 2a and 2b in the same phase, the phase difference: ψ is maintained as it is even after the signal is converted by IF times. This can be derived and analyzed since the operating principle of the mixer is based on the multiplication effect.

Thereafter, the IF amplifiers 4a and 4b perform saturation amplification (no amplitude component is required) so that the output amplitude is constant, and the phase detector 5 performs phase detection to obtain a DC voltage proportional to the phase difference. A specific model of this phase detector 5 is a balanced diode detector described on pages 5-39 and 5-42 of the same issue, which will be explained with reference to FIG. In this diagram,
7 is the input end of the reference signal: Easin (ωt), 8 is the input end of the signal whose phase difference is to be detected: Es 5in (ωt+ψ), and 9 is the output end of the detected output signal 2Eo. These relationships are: E0=K (CO3--cos2ω is the tenth higher-order frequency component)
- (4). However, K is a constant indicating detection efficiency.

Therefore, when this is treated as a detector, the components after the second term are removed by a low-pass filter, and Eo=K − cosψ ・
...(5), and an output amplitude corresponding to the phase difference: ψ is obtained. In addition, in FIG. 8, 10a to 10d are ring diodes for detection.

As explained above, the phase-detected output contains information on the phase difference (ψ) of the arriving signal, and in turn contains information on the direction of the arriving signal, so by calculating these inversely, the direction can be determined. You can ask for it. The arithmetic circuit 6 in Fig. 6 performs this function, and the transmitting frequency is known as in a radar, or the wavelength λ in equation (1) is determined as in a narrow band receiving device. Then, you can easily calculate the direction.

[Problem to be solved by the invention]

Since the conventional direction finding receiver is configured as described above, it is necessary to accurately transmit the phase difference generated between the two antennas to the phase detector. However, it is difficult to match the phase characteristics of mixers and IF amplifiers, signal path lengths, etc., and it is even more difficult in practice to match the characteristics over a wide frequency range. .

This invention was made to solve the above-mentioned problems, and an object of the present invention is to provide a highly practical azimuth finding and receiving device that does not require matching the phase characteristics of mixers and IF amplifiers, the length of signal paths, etc. With the goal.

[Means to solve the problem]

The direction finding receiver according to the present invention is provided with a switch circuit on the output side of the antenna for connecting the outputs of the two systems of antennas and the inputs of the two systems of receiving systems in parallel or crossing each other. It is.

[Effect]

In this invention, by providing a switch circuit for connecting the outputs of the two series of antennas and the inputs of the two series of reception systems in parallel or crossing each other, the two series of reception systems after the antenna are connected. Even if a signal phase error occurs, it can be eliminated by calculation.

[Example] Hereinafter, an example of the present invention will be described with reference to the drawings. 1st
In the figure, 11 is a transfer switch that is located between the antenna and the receiving system and switches the signal paths of two systems;
2 is a band pass filter that determines the frequency band of the high frequency signal to be received; 13 is a signal splitter; 14 is a frequency measuring receiver that measures the carrier frequency of the received incoming signal; 15 is a device that controls a series of operation sequences; A CPU circuit 16 stores temporal data, and a local signal generator 16 tunes an incoming signal by varying the oscillation frequency.

The operation will be explained below.

Since the target frequency range of the incoming signal is wide, the unknown frequency is first measured and recognized.

Radio waves received by antenna 1a are transferred to transfer switch 1
The signal is transmitted from the input end 11a of No. 1 to the output end 11c along the route shown in the figure. The bandpass filters 12a and 12b are used to determine the target frequency range (the ratio of the receivable frequency bandwidth to its center frequency is 15% or more), and signals with frequency components other than this are removed. Ru. The signal passing through this is divided into signal paths by the signal splitter 13,
The frequency measurement receiving device 14 is reached.

Very accurate frequency measurements are performed here.

This accuracy directly affects the wavelength: λ (= speed of light/frequency) in Equation 11 (mentioned above) when calculating the final direction, but it is a value that can be ignored if the current practical level is used. A specific model of the frequency measurement receiving device 14 is, for example, DIFM (Digital In5tan), which is commercialized by ANAREN Co., Ltd. in the United States.
taneous Frequency Measure
ment: digital output instantaneous frequency measurement) device. This is a type of FM detection applied to a wide microwave frequency band, and an example of its performance is 1.25 MHz over a frequency range of 4 to 8 GHz.
It is possible to obtain a digitized output with a frequency resolution of .

The frequency of the arriving signal measured in this way is CPU@
The CPU circuit 15 receives the signal and recognizes that the frequency is f. When detecting the direction of an incoming signal, the CPU circuit 15 uses this as an opportunity to execute a series of operation sequences.

Before describing the operation sequence, the operation of the transfer switch 11 will be explained first.

The transfer switch 11 has four signal terminals, and signals can be input and output from any of the terminals. This will be explained in the case of handling two different signals as shown in FIG. 2. In FIG. 2(a), for example, when the control signal is in the logic signal state "0", two high-frequency signals, B
respectively to terminal a.

When input to terminal b, output appears at terminals c and d. This is tentatively called the "parallel mode" (Fig. 2), on the contrary, the control signal is "1", and in this case, the high frequency signal
Outputs of B appear at terminals d and c, respectively. This state is called "cross mode". The control signal is “0” or “1”
”, and the transfer switch 11 is assumed to be in either “parallel mode” or “cross mode”.

Next, the operation sequence of the apparatus shown in FIG. 1 will be described.

The incoming signals received by the antennas 1a and lb are transferred to
The switch 11 is reached. Whether the switch 11 is initially in the "parallel mode" as shown by the solid line in FIG. 1 or in the "crossing mode" as shown by the broken line in the figure,
Either option may be used (however, in this embodiment, a case will be explained in which the case starts from the parallel mode); anyway, the signal appearing at the terminal 11C passes through the band pass filter 12a, and the signal splitter 13
and is guided to the frequency measurement receiving device 14. At the beginning of the operation sequence, the purpose is to recognize the presence or absence of an incoming signal and measure its carrier frequency, and this purpose is achieved when the CPU circuit 15 receives the output of the 0 frequency measurement receiver 14, which does not perform direction finding. As a result, when the CPU circuit 15 executes direction finding, as the next operation, the local oscillator 1
6 to tune to the measured frequency, and the incoming signal can be taken into the receiving system after mixers 2a and 2b.

Then, in the same manner as in the conventional circuit, if there is an incoming signal, the output from the phase detector 5 is sent to the CPU circuit 15.
5 is its phase data: ψ.

- memorize at - time. Next, the CPU circuit 15 sends a control signal "1" to the transfer switch 11 to set the "crossing mode".
Instruct to switch to. Then, the connection of the transfer switch 11 becomes as shown by the broken line in FIG. 1, and the signal from the antenna 1a is guided to the terminal lid of the transfer switch, and the signal from the antenna 1b is guided to the terminal 11c.

Similarly to the above, if there is an incoming signal, the output from the phase detector 5 is sent to the CPU circuit 15, and the CPU circuit 15 temporarily stores the phase data: ψ1 at that time.

Here, phase data: ψ. Analyze the meaning of and ψ. In FIG. 7, the antenna 1a is located at a distance R1 from the target.
Let the phase of the signal received at the antenna 1b be ψ, and at the same time the phase of the signal received by the antenna 1b via the distance R2 be ψ, and (1
Direction found from equation 1: If θ is ψ = ψ1 - ψ5, °, ゛λ, 4 (wavelength) = - (C is the speed of light) ... (7)
It is. The practical problem here is that the antennas 1a, l
It is difficult to physically and electrically align the phase characteristics of the receiving system from b to the phase detector 5 over a wide frequency band. Assuming that the phase characteristics are the same from the antennas la and lb to the output terminals 11C and lid of the transfer switch 11, and the phases generated by the receiving system after the antenna are ψ□ and ψ□, respectively, the temporarily stored phase data :ψ. , ψ1 is ψ. =ψ, +ψ□−ψ1−ψ□ ... (8) ψ
,=ψゎ+ψ□−ψ, −ψ□ (91), and the following equation holds true.

In other words, the uneven phases of the receiving system: ψ□, ψ□ are canceled out, and only the phase difference information received by the antenna can be extracted. Therefore, in the CPU circuit 15, the phase data: ψ
. , ψ1 to calculate the phase difference ψ, which is then sent to the calculation circuit 6 to calculate the azimuth θ.

A flowchart of these operational sequences is shown in FIG.

In such a direction finding receiver, even if a phase error occurs between the two series of signals in the reception system after the antenna, this can be canceled by calculation, so the phase characteristics of the mixer and IF amplifier, the length of the signal path, etc. There is no need to arrange them. In addition, we have provided a means to detect the incoming frequency and perform a series of operations based on this information, making it easy to find the direction using phase even when the frequency spans a wide band or is unknown. I can do it.

In the above embodiment, the frequency measuring receiver 14 is capable of measuring frequencies over a very wide band equivalent to the bandwidth of the bandpass filter 12, but this can also be achieved even with a somewhat narrow band. It is possible. FIG. 4 shows an example in which the IF frequency bandwidth is moderately narrowed, and this IF bandwidth is determined by the IF band filter 17. If the lower limit of this IF frequency is f IL + the upper limit is flM, then this f IL""' f I) If the frequency within I is known, the CPU circuit 15 instructs the local oscillator 16 to tune to the frequency; f. The receiving frequency; fM can be found from the relationship. In other words, if we consider the case where the frequency of the local oscillator 16 is always set lower than the reception frequency (rto<rH), the IF frequency measured by the frequency measurement receiver 18 with a medium frequency bandwidth is f+ (f+t≦fl≦ f+H
), the receiving frequency: fH is determined by the following formula.

fH=fL, +f, ...α
ω In this method, the frequency measurement receiving device can be made inexpensive, but instead, only the signal passing through the narrow IF band filter can be confirmed, making it impossible to monitor the entire frequency band. In addition, the sequence is not such that the incoming frequency is recognized at the beginning of the operation and then the phase is detected, but they are executed simultaneously.

FIG. 5 is an even more extreme example, in which the frequency measurement receiver is eliminated. If the IF frequency bandwidth can be made narrow enough, f+@f+t (gf IN)...
Since it is a subwoofer, the frequency measurement function can be omitted. Specifically, the azimuth accuracy is affected by the error of f, 4 in equation (6), but if this is within an allowable range, there is an advantage that it can be greatly simplified as shown in the system shown in FIG. Therefore, the IF band filter 19 in FIG. 5 has a narrow band pass characteristic (
The ratio between the receivable frequency bandwidth and its center frequency is 15
% or less) is different from the previous example.

In addition, although the above embodiment describes the case where radio waves are received by an antenna, if there is a device that can convert sound waves or ultrasonic waves into electrical signals using a microphone or an acoustic sensor, the same effect as in the above embodiment can be obtained. play.

Furthermore, in the above embodiment, the antenna and the receiving system are configured with two systems, but the antenna and the receiving system are configured with three or more systems.
It is also possible to configure the antenna and the receiving system to be selected in a matrix using receiving systems of more than one series (in this case, as in the above embodiment, the "parallel mode" and the "crossing mode" are This can be done by treating it as a comparison result and executing it multiple times.

〔Effect of the invention〕

As described above, according to the direction finding receiver according to the present invention, the outputs of the two systems of antennas and the inputs of the two systems of reception systems are connected to the output side of the antenna in parallel or in a manner that they cross each other. Since the switch circuit is provided, phase errors occurring in the receiving system can be canceled out, and the signal paths in the receiving system do not necessarily have to be of equal length, which has the effect of simplifying azimuth detection using phase.

[Brief explanation of the drawing]

Fig. 1 is a block diagram showing a direction finding receiver according to an embodiment of the present invention, Fig. 2 is a diagram illustrating switching between the output of the antenna and the human power of the receiving system, and Fig. 3 is its operation sequence. Figures 4 and 5 showing flowcharts of
The figures are block diagrams showing direction finding receivers according to other embodiments of the present invention, FIG. 6 is a block diagram showing a conventional direction finding receiver, and FIG. 7 shows the relationship between incoming radio waves to two series of antennas. The figure shown in FIG. 8 is a diagram showing the configuration of a typical phase detector. 1 is an antenna, 5 is a phase detector, 6 is an arithmetic circuit, 11 is a transfer switch, 14 is a frequency measurement receiver, 1
6 is a local oscillator. In addition, in the figures, the same reference numerals indicate the same or equivalent parts.

Claims (1)

[Claims] (1) An incoming signal from one signal source is received by a receiving system and two series of antennas arranged so that the phase relationship can be received according to the formula, and the output of the receiving system is based on the signal phase of the two series according to the formula above. In the direction finding/receiving device for calculating the direction of the incoming signal, the device is provided on the output side of the antenna, and the output of the two systems of antennas and the input of the two systems of receiving systems are connected in parallel or crossing each other. A direction finding/receiving device characterized by comprising a switch circuit for connection.