JPS63233388A - Angle signal offset correcting circuit - Google Patents

Abstract

PURPOSE:To decrease an offset voltage necessary for an accurate radar instrument by digitally counting the positive and negative periods of angle signals with respect to a reference voltage and adding the voltage of a difference in a direction wherein a difference between the positive and negative periods becomes zero. CONSTITUTION:A comparison circuit 1 compares an angle signal 16 and a reference voltage 20 with each other and outputs a rectangular wave voltage 11. The voltage 11 takes a high voltage level for a period wherein the voltage of the angle signal 16 is higher than the reference voltage 20 and a low voltage level for a period wherein the voltage of the angle signal 16 is lower than the reference voltage 20. A counter circuit 3 digitally counts the periods wherein the voltage 11 from the circuit 1 is at high and low levels by clock signals 12 from an oscillator 2 and feeds a result to a difference detecting circuit 4. The circuit 4 detects a time difference between high and low voltage level periods and, when the time difference is large, feeds positive or negative correcting data 14 to a D/A converter 5. The converter 5 converts the correcting data 14 to an analog correcting voltage 15. An adding circuit 6 adds the correcting voltage 15 to an angle signal 10 and outputs the angle signal 16 wherein the offset of the signal 10 is corrected.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a circuit that is used in a radar device and corrects an offset voltage in a sine wave signal or a cosine wave signal representing an angle such as an azimuth angle of an antenna.

(Prior Art) Conventionally, an angle signal used in a radar device is a signal representing the azimuth angle of an antenna. The angle signal expresses the azimuth using analog voltages with sine and cosine waveforms. The radar indicating device directly uses the voltages of the sine waveform and cosine waveform as angle information for PPI display, and provides radar information using the PPI method. Since the angle signals of the radar device are used in this way, the sine wave and cosine wave voltage signals are one of the important factors determining the distance accuracy and angular accuracy of the PPI display on the indicating device. Therefore, high-performance operational amplifiers are used to transmit this angle signal, and consideration is given to minimizing offsets due to changes in temperature and transmission impedance.

(Problem to be solved by the invention) As mentioned above, in an angle signal, the voltage value directly represents the angle, so the voltage value of the angle signal must be transmitted correctly. Conventionally, the voltage value has an offset. Expensive parts were used in the transmission circuit to prevent this from occurring. However, even with an expensive circuit configuration, it is still impossible to completely eliminate the offset of the angle signal due to fluctuations in temperature and transmission impedance.

If the angle signal is offset, the PPI display of the pointing device will be off-center, resulting in errors in direction and distance.

Conventional angle signal transmission systems depend on the stabilization of circuit characteristics as described above, so there is a limit to the reduction of offset voltage, and it is not possible to reduce the offset voltage sufficiently to the extent required for high-precision radar equipment. Ta.

(Means for Solving the Problems) Means provided by the present invention to solve the above-mentioned problems is to input a first angle signal representing an angle using a voltage of a sine wave or a cosine wave, and An angle signal offset correction circuit that outputs a second angle signal with a reduced offset voltage of the angle signal, the circuit compares the voltage of the first or second angle signal with a reference voltage, and calculates the voltage of the angle signal by comparing the voltage of the first or second angle signal with a reference voltage. Outputs a rectangular wave voltage in which a high voltage level period and a low voltage level period correspond to a first period in which the voltage of the angle signal is higher than the reference voltage and a second period in which the voltage of the angle signal is lower than the reference voltage, respectively. a comparison circuit; a clock oscillator that generates a clock signal; a counter that counts the high voltage level period and the low voltage level period using the clock signal; and a counter that counts the high voltage level period and the low voltage level period based on the output of the counter. A difference detection circuit that detects the time difference from the period and outputs the difference time as a digital signal, a D/A converter that converts the difference time signal into an analog voltage, and an output of this D/A converter. and an addition circuit that adds the analog voltage and the first angle signal and outputs the result as the second angle signal.

(Example) Next, the present invention will be explained with reference to the drawings.

FIG. 1 is a block diagram of one embodiment of the present invention, and FIG. 2 is a block diagram of an embodiment of the present invention.
It is a figure which shows the large output waveform of the comparison circuit in a figure. The comparison circuit 1 compares the angle signal 16 and the reference voltage 20,
A rectangular wave voltage 11 is output. The rectangular wave voltage 11 is at a high voltage level during a period T1 when the voltage of the angle signal 16 is higher than the reference voltage 20, and is at a low voltage level during a period T2 when the voltage of the angle signal 16 is lower than the reference voltage 20. Counter circuit 3
uses the clock signal 12 from the oscillator 2 to digitally count the high voltage level period T1 and low voltage level period T2 of the rectangular wave voltage 11 from the comparison circuit 1, and sends the result to the difference detection circuit 4. The difference detection circuit 4 detects the time difference between the period T1 and the period T2, and if the period T1 is longer, negative correction data of the difference is provided, and if the period T2 is longer,
Positive correction data for the difference is generated and sent to the D/A converter 5. The D/A converter 5 converts this digital correction data 14 into an analog correction voltage 15. The adder circuit 6 adds an analog correction voltage 15 to the angle signal 10 and outputs an angle signal 16 in which the offset of the angle signal 10 is corrected.

The input and output signals of the comparator circuit 1 will be explained in detail with reference to FIG. The sine wave angle signal 1″0 is slightly offset in the pressure direction. Therefore, in the rectangular wave voltage 11 output from the comparator circuit 1, the high voltage level period T1 is longer than the low voltage level period T2. This time difference Tl-72 is detected and the correction voltage 15 is added to the angle signal 10.If T1 and T2 are the same time, the time difference will be O and the correction voltage will be O. In this way, the offset correction circuit of this embodiment operates so that the offset voltage of the angle signal is corrected in the direction in which the difference between T1 and T2 becomes zero.

(Effects of the Invention) As explained above, the present invention digitally counts the positive time and negative time with respect to the reference voltage of the angle signal, and increases the difference in the direction in which the difference between the positive and negative times becomes 0. Add the voltage to the angle signal. Therefore, the circuit of the present invention can correct offsets due to temperature and impedance in the transmission of angle signals with a relatively inexpensive circuit configuration and with digitally determined accuracy.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of one embodiment of the present invention, and FIG. 2 is a block diagram of an embodiment of the present invention.
FIG. 3 is a diagram showing input and output waveforms of the comparator circuit in the illustrated embodiment. DESCRIPTION OF SYMBOLS 1... Comparison circuit, 2... Oscillator, 3... Counter circuit, 4... Difference detection circuit, 5... D/A converter,
6...Addition circuit. Figure 1 Figure 2

Claims (1)

[Claims] Angle signal offset correction that inputs a first angle signal representing an angle using a sine wave or cosine wave voltage, and outputs a second angle signal with a reduced offset voltage of the first angle signal. The circuit compares the voltage of the first or second angle signal with a reference voltage, and includes a first period in which the voltage of the angle signal is higher than the reference voltage and a second period in which the voltage of the angle signal is lower than the reference voltage. a comparator circuit that outputs a rectangular wave voltage in which a high voltage level period and a low voltage level period correspond to the period 2; a clock oscillator that generates a clock signal; a counter that counts the low voltage level period; and a difference detection circuit that receives the output of the counter, detects a time difference between the high voltage level period and the low voltage level period, and outputs the difference time as a digital signal. , a D/A converter that converts the time difference signal into an analog voltage, and the analog voltage output from the D/A converter and the first
An angle signal offset correction circuit, comprising: an addition circuit that adds the angle signals of 1 and 2 and outputs the resultant as the second angle signal.