JPH0129269B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an improvement of an amplitude modulated radio direction finder using goniometer rotation.

[Conventional technology]

In a wireless direction finder, the direction signal obtained by measuring the direction of arrival of radio waves is a sine wave signal that is repeated at a predetermined period, and a predetermined phase point of this sine wave signal indicates the direction of arrival of the radio wave. Detector signals may be displayed using a propeller-shaped display image (referred to as a propeller image in this invention).
Displays are useful because they allow you to directly see moment-to-moment changes in the direction of arrival, the modulation status of the measured radio waves, the electric field status, etc.

As for such radio direction finders, literature, Showa era
No. 125 in “Radio Direction Measuring Device” published by Corona in 1932
According to Figure 96 on page 96 and its explanation, a rotating two-phase AC generator, that is, one using a resolver,
Also, according to the same document, page 129, Figure 99 and its explanation, a stationary two-phase AC generator, that is, an oscillating
It is well known that a combination circuit of phase division and phase conversion circuits is used.

Furthermore, according to Japanese Patent Publication No. 40-28819, a pulse generation mechanism for generating a reference pulse and a counting pulse is connected to a rotating mechanism for rotational modulation, and a digital azimuth value is obtained by counting azimuth points using these pulses. is disclosed. Even in this case,
If the direction-finding antenna is of a rotary type rather than rotating, modulation by two-phase alternating current is required, and for the generation of this two-phase alternating current, the above-mentioned rotating type or stationary type is used. There is.

In other words, in either case, it is necessary to first generate a single-phase AC signal and then convert it into two-phase AC using a rotating decomposer or a stationary decomposer. ing.

[Problem to be solved by the invention]

In such a direction finder, the waveform distortion and relative phase shift in each phase of the two-phase alternating current directly affect the directional accuracy of the displayed image. , it is necessary to provide complex means to prevent and correct the occurrence of such distortions and phase shifts.

For large ships and land surveillance, the antenna should be installed in a location with no radio interference nearby, such as on top of the highest mast or in a large vacant area on a plateau, and the receiving and display equipment should be placed far away from the antenna. It is installed inside the ship or indoors.

In this case, a device that combines a direction-finding antenna such as a loop antenna, a goniometer, etc. is installed as an antenna section, and the other parts, that is, the main body of the receiver, display, etc., are installed several hundred meters or more away. parts are arranged.

As a result, the transmission lines for two-phase AC become longer, and the electrical constants of the transmission lines for each phase differ, resulting in display errors due to the phase difference between each phase being out of order or the waveform being deformed. is attenuated, resulting in a signal with poor S/N, so it is necessary to limit the amount of extension, use an expensive cable with low attenuation, or install an amplifier circuit or phase adjustment/waveform adjustment circuit in the middle. It was necessary to take measures such as the high cost.

In addition, with stationary types, the electrical constants of the circuit that separates a single phase into two phases change over time, causing errors similar to those mentioned above, so it requires complicated and expensive measures to prevent or maintain this. It takes.

Furthermore, various electrical or mechanical measures have been taken to prevent or correct errors caused by the installation conditions of the direction-finding antenna, the transmission process of the direction signal and the two-phase alternating current, and the like.

There is a problem in that it is expected to provide a simple and inexpensive product that eliminates such complicated and expensive parts.

[Means to solve the problem]

The present invention provides a signal having azimuth information by amplitude modulation obtained by rotating a goniometer connected to a direction-finding antenna (hereinafter referred to as an azimuth signal), and a signal modulated with a two-phase alternating current signal (hereinafter referred to as a two-phase modulation signal). In a direction finder that indicates the direction of arrival of a radio wave by means of a signal (referred to as a signal), a measurement direction reference signal generator is used to detect and count the reference direction, which is the measurement reference for the direction of arrival, as a measurement direction reference signal. , a fixed memory circuit that stores digital values of the sine wave and cosine wave of the two-phase alternating current; a rotation reference means that rotates the reference signal generator by attaching it to the drive part that drives the rotation; Obtaining the digital value as a two-phase digital signal by operating the fixed storage circuit based on the measurement direction reference signal, and obtaining the two-phase alternating current based on the two-phase digital signal.
The above problem is solved by providing a phase alternating current generation means and a delay correction means for correcting the direction of arrival display by delaying the phase of the two-phase alternating current by delaying the measurement direction reference signal. It was designed to be obtained.

〔Example〕

Examples will be described below with reference to figures. FIG. 1 shows a block diagram of the present invention, which includes a motor 3 that drives an RF goniometer search coil 2 that extracts azimuth information from a loop antenna 1, a reference signal generator 4 that detects the 0° direction, and a clock signal generator 5 that detects the 0° direction. This output is added to the counter 7 to count 360 degrees with the 0 degree direction as the base point, and the fixed memory circuit 8
make it work. A sine wave and a cosine wave are stored in the fixed storage circuit 8, and a sine wave signal and a cosine wave signal of digital values synchronized with the rotation of the RF goniometer search coil 2 appear in the output.

These signals are passed through D/A converters 9 and 10 respectively to generate analog sine and cosine waves, that is, two-phase alternating current. Therefore, these sine and cosine waves are signals corresponding to the rotation angle of the RF goniometer search coil 2. becomes. On the other hand, the output azimuth signal of the RF goniometer search coil 2 is applied to the receiver 11, amplified and detected, and then applied to the modulator 13 together with the output of the video carrier wave generator 12 to modulate the video carrier wave. The modulated video carrier wave is sent to the D/A converter 9 mentioned above.
As shown in the figure, along with the sine wave and cosine wave which are the outputs of CRT 16, the sine wave and cosine wave are applied to the balanced modulators 14 and 5, respectively, and the output excites the deflection plate of the CRT 16, so that the orientation can be obtained as a propeller-shaped image. . Further, the counter 7 is counted by the clock signal and reset by the reference signal.
By delaying the position of this reference signal by the delay circuit 6, shifting the reset timing of the counter 7, and changing the phase of the two-phase alternating current,
The azimuth angle of the propeller image of the CRT 16 can be changed by the amount of this phase. This amount of delay is controlled by a delay controller 17.

〔Effect of the invention〕

According to the present invention, as described above, the sine wave and cosine wave stored in the fixed storage circuit are simultaneously read out based on the reference signal whose reference direction has been detected to obtain the two-phase AC signal. In addition, it is possible to eliminate direction display errors caused by phase differences and waveform distortions caused by differences in the electrical constants of the transmission lines of each phase of two-phase AC, and the transmission lines can be simple and inexpensive cables, and can also be used with telephone lines. It also becomes possible to perform ultra-long distance transmission without error.

In addition, even if a direction display error occurs due to a difference between the direction information obtained from the goniometer side and the two-phase AC generation side and the transmission path, the reference signal that detects the reference direction is only delayed. It has the advantage of being able to provide correction with a simple and inexpensive configuration.

[Brief explanation of drawings]

FIG. 1 shows a block diagram of the invention. DESCRIPTION OF SYMBOLS 1...Loop antenna, 2...RF goniometer search coil, 3...Motor, 4...Reference pulse generator, 5...Clock pulse generator, 6...Delay circuit,
7...Counter, 8...Fixed memory circuit, 9...D/A converter, 10...D/A converter, 11...Receiver, 12
...Video carrier generator, 13...Modulator, 14...Balanced modulator, 15...Balanced modulator, 16...CRT, 17
...delay controller.

Claims (1)

[Claims] 1. A signal having azimuth information by amplitude modulation obtained by rotating a goniometer connected to a direction-finding antenna (hereinafter referred to as the azimuth signal) and a modulated signal with a two-phase AC signal (hereinafter referred to as the azimuth signal). In a direction finder that displays the direction of arrival of radio waves using a two-phase modulated signal (referred to as a two-phase modulated signal), a direction reference signal outputs a signal for detecting and counting a reference direction that is a measurement reference for the direction of arrival as a measurement direction reference signal. a generator; b a fixed storage circuit that stores digital values of the sine wave and cosine wave of the two-phase alternating current; and c a rotation reference that rotates by attaching the measurement direction reference signal generator to the drive part that drives the rotation. means for obtaining the digital value as a two-phase digital signal by operating the fixed storage circuit based on the measurement direction reference signal, and obtaining the two-phase alternating current based on the two-phase digital signal; An apparatus characterized by comprising: a phase alternating current generating means; and e a delay correcting means for correcting the display of the direction of arrival by delaying the phase of the two-phase alternating current by delaying the measurement direction reference signal. .