JPH0322951B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a radio direction finder for measuring the arrival direction of radio waves.

[Conventional technology]

This type of radio direction finder is
A large number of omnidirectional antennas such as the 35828 are arranged at equal intervals on the circumference, and these are sequentially switched and scanned to create a received azimuth signal with azimuth components due to phase changes.This phase change is used to convert the phase components of the reference azimuth into The arrival direction of the radio wave can be measured by comparing it with a reference signal. In such a radio direction finder, if two or more radio waves are received at the same time, it will seriously interfere with direction measurement, resulting in a large error in the measured direction.

When two or more radio waves are received within the same IF band, in a direction finder using a normal quadrature demodulator, the two signals influence each other, but there is a sufficiently large strength between the two signals. Difference (more than 20dB)
If there is, it indicates the direction of arrival of the strongest radio wave. However, when there is not much difference in strength, the beat components of both signals are mixed into the azimuth signal, and in severe cases, the azimuth indicating ability is usually lost.

In order to remove this interference wave, the receiver's IF
It would be possible to make the filter narrower, but manufacturing a narrower filter is extremely difficult and at the same time makes it difficult to receive radio waves, making it impractical.
In addition, in order to measure the direction of arrival of radio waves, antenna rotation or an equivalent rotation operation, such as the above-mentioned sequential switching scan, is required, and for this reason, the measurement radio waves are subjected to phase modulation or frequency modulation due to the rotation. Since the received signal having the obtained azimuth component has a corresponding bandwidth, there are restrictions such as the inability to unnecessarily narrow the bandwidth.

Additionally, these wireless direction finders use a PLL to detect received signals to obtain direction signals.

This PLL has synchronous operation and follow-up operation.
Configure PLL when changing input frequency
The range in which the VCO can be brought into synchronization is called the capture range, and the range in which the synchronization can follow after being brought into synchronization is called the lock range.

The capture range and lock range can be set to the operating range that suits the desired purpose by selecting the circuit constants that make up the PLL, as reported in "Transistor Technology" Magazine, August 1976 Issue 90, published by CQ Publishing. ~P.97 "Basic Technology of PLL IC" etc.

[Problem to be solved by the invention]

Therefore, it is desired to provide a radio direction finder that can detect the direction of arrival of radio waves corresponding to each received signal that is received with interference due to the reception band with the above-mentioned restrictions. There are challenges.

[Means to solve the problem]

The present invention is a radio system that receives a received signal having an azimuth component due to a phase change as described above in a predetermined reception band, and measures the direction of arrival of radio waves based on the azimuth signal obtained by detection using a PLL. In a direction finder, a plurality of PLL means is provided in which a plurality of PLLs are provided in order to separate and detect received signals of interference radio waves within the above reception band, and each center frequency of the capture range of each PLL is set within the reception band. The above-mentioned problem can be solved by providing a plurality of in-band arrangement setting means for separately setting the end portions of each capture range.

〔Example〕

Hereinafter, an embodiment in which each direction signal can be obtained by detecting received signals due to two interfering radio waves will be described with reference to the drawings.

In Fig. 1, 1 is an antenna group in which vertical omnidirectional antennas are arranged at equal intervals on the circumference, and 2 is an antenna group in which the output of each vertical omnidirectional antenna is sequentially switched by a reference signal obtained from a reference signal generator 7. 3 is a receiver, and the output of the receiver 3 converts modulated components associated with communication content such as audio signals contained in received radio waves into amplitude modulated waves. In the case of a frequency modulated wave, it is removed by a limiter, and in the case of a frequency modulated wave, it is removed by cancellation removal, so that a reception output containing only the phase modulation component due to the azimuth component, for example, an IF signal output, is obtained, and this output Up to this point, it is composed of the same components as the conventional one. 4 is a detection circuit composed of three phase locked loop (hereinafter referred to as PLL) detectors 4A, 4B, and 4C.

As shown in Figure 2, the PLL used in the method of the present invention includes a phase comparator circuit (hereinafter referred to as PD), a low frequency filter (hereinafter referred to as LPF), and a voltage controlled oscillator (hereinafter referred to as VCO).
).

In this example, C, CV1, and CV2 are capacitors for determining the capture range of each PLL, that is, the center frequency of the frequency range that can be synchronized.
CV1 and CV2 are variable capacitors.

PLL(A) has a wide capture range, e.g.
The circuit constants are set so that the capture range of PLL(B) and PLL(C) is narrow, for example, 200Hz.

S1 is a switch. When there is no interference, that is, at all times, it is connected to the a side and connected to the PLL (A) 4A, and when there is interference, it is connected to the b side and connected in parallel with the detection circuit PLL (A) 4A. multiple detection circuits PLL(B)4B,
Switch and select PLL(C)4C. Furthermore, the power supply +V is applied to the square wave oscillator 13 to operate it, and the oscillation output as shown in FIG.
The output of the video signal generation circuits 8 and 9 is operated so that it is connected to the a side when it is "H", and to the b side when it is "H".
Select and switch Y ₁ , Y ₂ , X ₁ , and X ₂ .

When the power supply +V applied to the square wave oscillator 13 is cut off, the control terminals Q of S2 and S3 become 0,
S2 and S3 remain connected to the a-side terminal and select video outputs Y ₁ and X ₁ .

Amplifiers 5 and 6 remove noise using appropriate filters and perform necessary amplification to obtain the azimuth signal as shown in FIG. 6C. 8 and 9 are video signal generators, which display direction lines d and d ₂ in polar coordinates on the cathode ray tube 14.
It generates a signal for drawing the image, and has a configuration as shown in FIG. When the azimuth signal C is multiplied by the standard sin and cos waves shown in Figure 6 A and B from the reference signal generator 7, the outputs shown in D and E are obtained, and only the DC components V _X and V _Y are generated. When extracted by a filter, the output is proportional to the cosine and sine values of the direction of arrival of the radio wave, respectively.
In other words, the reference signals sinωt, cosωt, and direction signal are
The product of both signals, sin(ωt+θ), is Asinωt・sin(ωt+θ)=A/2[c
osθ−cos(2ωt+θ)]……(1) Acosωt・sin(ωt+θ)=A/2[s
inθ+sin(2ωt+θ)]...(2) (A represents the amplitude), so the DC component is proportional to cosθ and sinθ, respectively, as described above.

If this output is applied to the deflection plate of the cathode ray tube 14, the bright spot will remain shifted in the direction θ. Therefore, if the outputs V _X and V _Y of the product circuits 81 and 82 in FIG.
Triangular waves whose _maximum values are proportional to _V This indicates the direction in which the radio waves arrive.

Note that the PLL detector used in this example operates as follows. Adjust the frequency knob on the receiver to bring the input frequency _i , for example, the output of an intermediate frequency amplifier, closer to the free running frequency of the VCO (voltage controlled oscillator) and enter the capture range, as shown in Figure 3. At the point where the input frequency is ω ₁ at the end of the capture range, the free-running frequency of the VCO starts and enters a synchronized state. In this process, when the input frequency ω ₁ and the free-running frequency of the VCO do not match (when they are not synchronized), the output of the PD (phase detector), that is, the error voltage Vd of the loop is 0, and the input frequency _i gradually
When the free-running frequency of the VCO approaches ₀ , the PD changes to the input frequency.
_i and its phase are compared with that of the VCO to generate an error voltage Vd for the difference in phase and frequency between the two signals. This voltage passes through an LPF (low pass filter) and is supplied to the VCO as Vd.

This control voltage Vd changes the VCO frequency in the direction of reducing the frequency difference between ₀ and the input signal, so
At the point _ω1 , the loop error voltage Vd suddenly turns to the negative side in synchronization (lock) with the input frequency. Furthermore, the error voltage Vd changes with the frequency of the VCO so that it is finally equal to the reciprocal of the VCO conversion gain K ₀ and stabilizes at ω ₁ =ω ₀ . Note that these changes occur instantaneously. The loop follows the input frequency until it reaches the lock range, that is, the upper limit frequency ω ₂ of the synchronization tracking range, and when it exceeds ω ₂ , the loop loses synchronization and the error voltage Vd becomes 0.

Next, when the input frequency is slowly lowered (returned to its original value), at the point ω ₃ , the VCO frequency is in step with the input frequency and becomes synchronized, and the loop error voltage Vd suddenly turns to the positive side. The value of Vd changes with frequency and ω ₃
= ω ₀ and the loop follows the input until it reaches the lower limit frequency ω ₄ of the lock range, and once this is exceeded, the loop loses synchronization and the error voltage Vd becomes 0. In addition,
From FIG. 3, the capture range (frequency range that can be pulled into synchronization) is ω _c =ω ₃ -ω ₁ /2, and the lock range (range that follows synchronization) is 2ω _L = ω ₂ - ω ₄ .

Therefore, the free running frequency ω ₀ of the VCO and the input frequency ω _c
If it is within ωc, the loop enters synchronization and does not respond to signals above _ωc . Therefore, by reducing the capture range, it becomes possible to separate and measure two closely spaced radio waves.

In the above-mentioned apparatus, the outputs of each antenna in the antenna group 1 are sequentially switched in the antenna switch 2 and connected to the receiver 3 using a switching pulse train obtained from a reference signal. After being amplified by the receiver 3, it is added to the detection circuit 5.

When only a single current is being received, switch S1 is connected to the a side terminal, and PLL (A) uses capacitor C to set approximately the center frequency of the receiver IF output to the center frequency of the capture range. , the capture range is about the same as the IF bandwidth. When the receiver is tuned and the received output enters the capture range, the PLL (A) is pulled in and becomes synchronized. From then on, only the phase change due to the azimuth component is detected by the PD, and this detected output is obtained as the azimuth signal. Therefore, when this is amplified by the amplifiers 5 and 6, an azimuth signal C positioned by the antenna rotation is obtained.

Regarding the ability to obtain azimuth signals using PLL, please refer to Special Publication No. 58-52187 and Special Publication No. 59-25986.
It has been disclosed by et al. In addition, wide/narrow adjustment of the PLL capture range is achieved by changing the LPF band and PD output, and adjustment of the center frequency of the capture range is achieved by changing the C/R time constant for specifying the VCO oscillation frequency. It is well known that this can be done by changing the value of capacitance C or resistance R. This is multiplied by the reference signal in the video signal generation circuit 8 to extract its DC component, further modulated with a triangular wave, and the output is applied to the cathode ray tube through switch S2. can get. As mentioned above, since S1 is connected to the a side terminal, the square wave oscillator does not operate and S1
2. Since the control terminal of S3 is set to 0, it is always connected to the A side terminal and the video signal generation circuit 8
Only the outputs Y ₁ and X ₁ are applied to the cathode ray tube.

Next, if two radio waves are received in the same band and cause interference, as shown in _A and _B in Figure 4, switch S1
is connected to the contact b side, and the outputs of PLLs (B) and (C) are connected to amplifiers 5 and 6, respectively. Each starting point of VC1 and VC2 is a variable capacitor VC1 for adjusting the center frequency of the capture range of PLL(B) and PLL(C).
The center frequency of the VCO is set to be the lower limit frequency of the receiving band of the receiver 3, that is, the IF band, and the center frequency of the VCO of VC2 is set to be the upper limit frequency of the IF band.

Next, finely manipulate VC1 to raise the center frequency of the VCO as shown by the arrow in Figure 4, bringing it closer to reception frequency _A.

As mentioned above, when the frequency difference U between _A and the center frequency ₀₂ of the VCO enters the capture range, it becomes _A.
02 is pulled in, synchronized and stabilized. However, for _B , the frequency difference is larger than the capture range, so it cannot be synchronized. Therefore, PLL (B) performs a fine adjustment operation so that only the radio waves of _A can be extracted and the azimuth signal can be obtained.

Next, finely manipulate VC2 to adjust the center frequency of the VCO.
When ₀₃ is brought closer to the direction of the arrow and the frequency difference V reaches the capture range, ₀₃ C is pulled into _B and becomes stable in synchronization. However, it cannot synchronize with _A because it is out of the capture range. The two azimuth signals obtained here are amplified by amplifiers 5 and 6 and added to video signal generators 8 and 9, and as mentioned above, Y ₁ ,
Outputs proportional to the cosine and sine of two radio wave arrival directions such as X ₁ , Y ₂ , and X ₂ are obtained and applied to semiconductor switches S2 and S3.

Since the switch S1 is connected to the b-side terminal, the power supply +V is applied to the rectangular wave oscillator 13, and it is in operation. Accordingly, the semiconductor switches S2 and S3 apply signals as shown in FIG. Although FIG. 7 only describes the video signal outputs Y ₁ and Y ₂ , the same switching can be performed for X ₁ and X ₂ as well.

Therefore, since the direction signals of the two radio waves _A and _B are switched and displayed alternately at high speed, a dotted unidirectional bright line indicating the direction is obtained as shown in the figure. Note that by varying the period and duty ratio of the rectangular wave oscillator 13, it is possible to display the signal using a dashed-dotted line, or to display a solid unidirectional bright line alternately every other period.

In this way, by installing a detector consisting of two PLL(B) and PLL(C), the free-running frequency of the VCO of one PLL(B) is gradually increased from the low one, and the free-running frequency of the VCO of the other PLL(C) is increased gradually. It is possible to separate and extract two adjacent radio waves by gradually lowering them from the higher one and synchronizing them with the radio waves closer to each other.

Note that the capture range ω _c is given by Kv, the DC gain of the LPF time constant τ loop. Since it can be expressed as, increasing the LPF time constant τ,
By adjusting the direct current gain of the loop to a small value, the range can be narrowed, and two radio waves that are very close to each other can be separated and the direction can be measured.

As mentioned above, with ordinary quadrature detectors, it is difficult to simultaneously measure both radio waves because the desired signal is affected by the adjacent channel signal until it reaches 20 dB or less. According to the embodiment of the present invention, even when two radio waves are received at the same time, two PLL detectors are used to separate them and measure them instantly.
The direction in which each radio wave arrives can be displayed on a cathode ray tube.

[Modified implementation of the invention]

This invention can be implemented in the following modifications.

(1) In the case of detecting only a relatively narrow specific frequency range, the detection circuit 4 is connected to PLL(B)4B,
Only PLL (C) 4C is used, switch S1 is removed, and only these two outputs are used.

(2) Using the outputs of the amplifiers 5 and 6 and the reference signal generator 7, the respective directions are displayed on separate direction indicators, for example, two digital direction value displays.

(3) Switches 4 and 5 similar to the switches 2 and 3 and the square wave oscillator 13 and a square wave oscillator 15 are provided between the video signal generator 9 and the switch S3 as shown in FIG. By configuring the rectangular wave period of PLL(B) 4B to be equal to or higher than the signal period of the video signal generator 8, and configuring the rectangular wave period of the rectangular wave oscillator 15 to be a fraction thereof, the PLL(B) 4B
The direction signal on the side is a solid display line, and the PLL(C)
The azimuth signal on the 4C side is displayed as a dashed display line, making it easy to distinguish between the two direction display lines.

(4) The same effect can be obtained by changing the free running frequencies of PLL(B) 4B and PLL(C) 4C using variable resistors instead of capacitors VC1 and VC2.

(5) The capacitors VC1 and VC2 are each composed of a capacitance diode and a variable voltage power supply, and this variable voltage power supply is a combination of a D/A converter and a counter that provides input to this, and one counter is an up counter. , the other being a down counter, giving a count pulse to each counter through a gate, each gate being opened by a switch interlocking with switch S1,
Based on the output obtained by comparing the rectified integral value level of each output of PLL (B) 4B and PLL (C) 4C with a fixed value,
The locking operation by fine adjustment of capacitors VC1 and VC2 is automatically operated by closing each gate.

〔Effect of the invention〕

According to this invention, as described above, a plurality of PLLs are provided in order to separate and detect received signals of interference radio waves within the reception band, and each center frequency of the capture range of each PLL is set within the reception band. In addition, the ends of each capture range are set separately, so even if there is radio wave interference, each received signal within the reception band will be routed to multiple separate PLLs. Since the wave is detected by
Features include the fact that it can be provided by a simple and inexpensive device that includes multiple PLLs that can detect the azimuth signal corresponding to each received signal separately by each PLL, and adds a configuration that sets the operation to predetermined conditions. There is.

Regarding the operating ranges of synchronization pull-in using the capture range and tracking using the lock range, as explained in the above example, each received signal that appears within the reception band is within the capture range of each PLL. Based on the above-mentioned conventional technology, the circuit constants constituting each PLL can be appropriately selected so that the detection can be performed separately.
No need to explain.

[Brief explanation of the drawing]

The drawings show embodiments; FIG. 1 is a block configuration example of the present invention, FIG. 2 is a configuration diagram of a PLL, and FIG. 3 is a block configuration example of the present invention.
An explanation diagram of PLL operation, Figure 4 is an explanation diagram of interference waves,
FIG. 5 is a block diagram of the video signal generation circuit, FIGS. 6 and 7 are waveform diagrams of the main parts, and FIG. 8 is a modified block diagram of the display section. 1: Antenna group, 2: Antenna switcher, 3: Receiver, 4: Detector, 5, 6: Amplifier, 7: Reference signal generator, 8, 9: Video signal generator, 10, 1
1: Deflection amplifier, 13, 15: Square wave oscillator, 1
4: Braun tube, S1: Switch, S2, S3,
S4, S5: semiconductor switch, C: capacitor,
CV1, CV2: Variable capacitor, 81, 82, 8
3: Product circuit, 85: Triangular wave generator.

Claims (1)

[Claims] 1. A received signal having an azimuth component due to a phase change is received in a predetermined reception band, and a PLL
A radio direction finder (hereinafter referred to as a device) that measures the direction of arrival of radio waves based on a direction signal obtained by detecting the waves, the device comprising: a) separating the received signal of interfering radio waves within the receiving band; a plurality of PLL means for providing a plurality of said PLLs for performing wave detection; b) setting each center frequency of the capture range of each said PLL to be dispersed within said reception band, and setting the center frequencies of the capture ranges of each said PLL at the ends of each capture range; and a plurality of in-band placement setting means for separately setting. 2. The device according to claim 1, comprising: a) the plurality of PLLs configured by two PLLs;
means; b. The center frequency of one of the two PLLs is set to the lower limit frequency of the reception band, and the center frequency of the other PLL is set to the upper limit frequency of the reception band within the band. A device characterized by comprising a plurality of arrangement setting means. 3. Receive a received signal with an azimuth component due to a phase change using a predetermined reception band, and
A radio direction finder (hereinafter referred to as a device) that measures the direction of arrival of radio waves based on a direction signal obtained by detecting the waves, the device comprising: a) separating the received signal of interfering radio waves within the receiving band; a first PLL means for providing a plurality of said PLLs with narrow capture ranges in order to perform wave detection; b) distributing each center frequency of the capture range of each of said PLLs by said first PLL means within said reception band; c) a unit with a wide capture range for performing the detection on the received signal within the reception band; a second PLL means for providing one of the PLLs; d setting each center frequency of the capture range of the PLL by the second PLL means near the center frequency of the reception band; an in-band single placement setting means for setting approximately the bandwidth; e. selection for always selecting the detection by the second PLL means and selecting the detection by the first PLL means when there is the received signal of interfering radio waves; An apparatus characterized by comprising means. 4. Receive a received signal with an azimuth component due to a phase change using a predetermined reception band, and
A radio direction finder (hereinafter referred to as a device) that measures the direction of arrival of radio waves based on a direction signal obtained by detecting the waves, the device comprising: a) separating the received signal of interfering radio waves within the receiving band; a plurality of PLL means for providing a plurality of said PLLs for performing wave detection; b) setting each center frequency of the capture range of each said PLL to be dispersed within said reception band, and setting the center frequencies of the capture ranges of each said PLL at the ends of each capture range; c. each signal obtained by sequentially selecting at predetermined intervals each signal based on each of the azimuth signals obtained by detection by each of the PLLs of the plurality of PLL means; An apparatus comprising: a plurality of direction display means for displaying the plurality of directions of arrival on the display by applying a signal to one display.