JPH02309280A - Correcting circuit of offset of angular signal - Google Patents

Abstract

PURPOSE:To keep down temperature in transmission of an angular signal and offset in a transmission impedance by counting digitally a time of plus and a time of minus in relation to a reference voltage of the angular signal and by adding a voltage of a difference to the angular signal in the direction wherein the difference between the time of plus and that of minus is 0. CONSTITUTION:When an offset correction amount is addition circuits 2a and 2b is zero, two comparison circuits 1a and 1b compare angular signal inputs (sine wave and cosine wave) with a reference voltage and output rectangular wave signals respectively. These two rectangular wave signals are subjected to an exclusive OR gate by an EX-OR gate circuit 3 and inputted to a counter circuit 4. A differential detecting circuit 5 operates so as to send correction data to the addition circuit 2 of the sine wave through a D/A converter 6. According to this constitution, an angular signal offset correction circuit always operates so as to output a corrected angular signal.

Description

Detailed Description of the Invention [Field of Industrial Application] The present invention relates to an angle signal offset correction circuit, and in particular to an angle signal offset correction circuit for correcting the offset of a sine wave signal and a cosine wave signal representing an angle such as an antenna azimuth angle in a radar device. This invention relates to an offset correction circuit.

[Conventional technology]

Conventionally, an angle signal representing the antenna azimuth of a radar device expresses the azimuth using an analog voltage having a sine waveform and a cosine waveform. The radar indicating device directly uses these sine waveform and cosine waveform voltages as angular change information expressed in PPI, and provides radar information based on the PPI method. These sine and cosine angular signals therefore correspond to the distance nJ degrees and angle efl of the PPI display on the radar indicator.
K is one of the important factors that determine lv degree. For this reason, a high-performance operational amplifier is used to transmit the angle signal, and consideration is given to minimizing offsets due to changes in temperature and transmission impedance.

[Problem to be solved by the invention]

In the conventional angle signal transmission system described above, the analog voltage value directly transmits the voltage value as the angle information of the radar indicating device, so expensive parts are used in the transmission circuit, and even with an expensive circuit configuration, temperature and It is impossible to completely eliminate the offset of the angle signal due to variations in transmission impedance, so it is impossible to eliminate the occurrence of offset in the angle signal, which has the disadvantage of causing a difference in the direction and distance on the PPI display. be.

SUMMARY OF THE INVENTION An object of the present invention is to provide an angle signal offset correction circuit having a simple configuration that eliminates the above-mentioned drawbacks and greatly suppresses offsets due to temperature and transmission impedance during angle signal transmission.

(Means for Solving the 8 Problems) The circuit of the present invention is an angle signal offset correction circuit that expresses the azimuth signal of the antenna of a radar device as a sine wave signal and a cosine wave signal component and corrects the offset amount in the nine angle signals. , two comparison circuits that compare the sine wave signal and the cosine wave signal with a reference voltage and output a rectangular wave signal whose rising and falling points are zero crossing points that transition to positive and negative regions; and the two comparing circuits. Exclusive logic that calculates the exclusive OR of two rectangular wave signals outputted by the sine wave signal and outputs a rectangular wave signal that repeats a high level period and a low level period determined by the zero cross points of the sine wave signal and the cosine wave signal. sum circuit and
a counter circuit that measures the time lengths of the high level period and low level period of the rectangular wave signal output from the exclusive OR circuit; and a counter circuit that receives the output of the counter circuit and the output of the two comparison circuits; a difference detection circuit that detects the time length difference between the output high level period and the low level period as an offset amount and outputs it as a digital signal; a D/A converter that converts the output of the difference detection circuit into an analog signal;
and two adder circuits that add the output of the /A converter to the sine wave signal and the cosine wave signal to correct the offset amount.

〔Example〕

The invention will now be described with reference to one drawing.

FIG. 1 is a block diagram showing the configuration of an embodiment of the angle signal offset correction circuit of the present invention, FIG. 2 is a main waveform diagram of the embodiment of FIG. 1 when an angle signal including an offset is input, and FIG. The figure is a main waveform diagram of the embodiment of FIG. 1 during offset correction.

The angle signal offset correction circuit of the embodiment shown in FIG. 1 compares the sine wave and cosine wave angle signal inputs with a reference voltage, and outputs a rectangular wave signal whose rising and falling points are the zero crossing points. Circuits 1a, lb and two comparison circuits 1al
EX-OR gate 3 of an exclusive OR circuit which calculates the exclusive OR of two rectangular wave signals outputted by lb and outputs a rectangular wave signal that repeats a high level period and a low level period;
a counter circuit 4 that measures the time length of a high level period and a low level period of a rectangular wave signal outputted from the X-OR gate 3;
Output of counter circuit 4 and two comparison circuits 1 a * 1
A difference detection circuit 5 receives the output of the counter circuit 4, detects the time length difference between the high level period and the low level period outputted by the counter circuit 4 as an offset amount, and outputs it as a digital signal, and converts the output of the difference detection circuit 5 into an analog signal. D/A converter 6
and two adder circuits 2a and 2b that add the output of the D/A converter 6 to the sine wave and cosine wave angle signal inputs to correct offset f.

Next, regarding the operation of the embodiment shown in FIG. 1, a will be explained.

In FIG. 1, two comparison circuits 1a and 1b compare the angle signal input (sine wave and cosine wave) with the reference voltage when the offset correction amount in adder circuits 2a and 2b, which will be described later, is zero. Outputs a square wave signal. These two rectangular wave signals are subjected to an exclusive OR gate by an EX-OR gate circuit 3 and input to a counter circuit 4. Referring to FIG. 2 below, the comparison circuits 1a, 1b
*The operations of the counter circuit 4 and the difference detection circuit 5 will be explained.

Now, an angle signal (sine wave) and an angle signal (cosine wave) that are shifted by 90 degrees from each other are input to the comparator circuits Ja and IbK, and the angle signal (sine wave) is offset for some reason, so It is assumed that the positive and negative regions are input asymmetrically with respect to the reference voltage.

The comparator circuit 1a outputs a rectangular wave signal of the specific power of the comparator circuit 1a, which is formed by using a zero loss void as a rising and falling tie/g by comparison with a reference voltage. On the other hand, the comparison circuit 1b outputs the comparison circuit 1b.

The EX-OR gate circuit 3 performs an exclusive OR of the output of the comparator circuit 1a and the output of the comparator circuit 1b, and finally sets the zero cross points of the two angle signal inputs as rising and falling points.
Generates the X-OR gate circuit 3 output.

The color/return circuit 4 operates during the high level period of the rectangular wave signal as the output of the EX-OR gate circuit 3, that is, Tl and T in FIG.
2 periods and low level periods, i.e. T3, T in FIG.
The time length of each of the four periods is digitally determined by a clock signal, and the result is sent to the difference detection circuit 5. The difference detection circuit 5 also receives rectangular wave signals from the two comparison circuits 1a + 1b, and the counter circuit 4
The timing of T1 to T4 of the rectangular wave signal from is recognized. The difference detection circuit 5 includes TI, T2, and T3.

The time difference between the periods T4 is detected according to the following conditions, and correction data for the difference is sent to the A/A converter 6.

The D/A converter 6 converts this digital correction data into analog correction pressure, and outputs it as an offset correction lid to the two adder circuits 2 according to the following conditions.

The adder circuit 2 adds the analog correction voltage and the angle signal input, and outputs a correct angle signal output.

Below is KT 1. T2, T3, T417) Conditions for detecting the time ryJ difference and conditions for outputting correction data will be explained.

(Condition 1) When (T1+T2)>(T3+T4): (TI+T
2) - (T3+T4) negative correction data is sent to the sine wave addition circuit 2 via the A/A converter 6.

If (T1+T2)<(T3+T4): ('l+T
2) - (T3+T4) is the positive correction data/A
It is sent to the sine wave addition circuit 2 via the converter 6.

(Condition 2) If (TI+74)>(T2+T3): (TI+T
4) Send negative correction data of -(T2+T3) to the cosine wave addition circuit 2 via the D/A converter 6.

If (TI+T4)<(T2+T3): (T1+T
4) Send the positive correction data of -(T2+T3) to the cosine wave addition circuit 2 via the D/A converter 6.

In particular, if the above conditions 1 and 2 are performed,
It operates so that the offset of angle i is corrected in the direction of making the time difference between the respective conditions zero.

FIG. 2 shows the input/output waveforms of the comparison circuits 1a and 1b and the input waveform of the difference detection circuit 50 when an offset angle signal (sine wave) is inputted (indicated by a solid line). In this case, the counter value T1. of the EX-OR circuit 3 output which is the difference detection circuit 50 input. T2゜T3. The condition for T4 is (T
Due to the rounding such that 1+T2)>(T3+T4) and the conditional operation described above, the difference detection circuit 5 calculates (TI+T2) −
The negative correction data (T3+T4) is operated to be sent to the sine wave addition circuit 2 via the A/A converter 6. As a result, negative correction data is added to the sine wave input shown by the solid line in FIG. 2, and the sine wave output shown by the broken line is output. By such operation, the present angle signal offset correction circuit always operates so as to output the corrected angle signal of TI=T2=T3=T4 shown in FIG.

〔Effect 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 converts the difference voltage into the angle signal in the direction where the difference between the positive and negative times becomes 0. By adding , it is possible to correct offsets caused by temperature and transmission impedance in the transmission of angle signals with a digitally determined precision using a relatively inexpensive circuit configuration.

[Brief explanation of drawings]

FIG. 1 is a block diagram of an embodiment of the angle signal offset correction circuit of the present invention, FIG. 2 is a main waveform diagram when an angle signal including an offset is input in the embodiment of FIG. 1, and FIG. FIG. 6 is a diagram of main waveforms during offset correction in the embodiment. la, lb...comparison circuit, 2a, 2b...
...Addition circuit, 3...EX-OR gate circuit, 4
. . . Counter circuit, 5 . . . Difference detection circuit, 6 . . . D/A converter. Agent: Patent Attorney Susumu Uchihara

Claims (1)

[Scope of Claims] An angular signal offset correction circuit that corrects an offset amount in an angular signal in which an azimuth signal of an antenna of a radar device is expressed as a sine wave signal and a cosine signal component, the sine wave signal and the cosine wave signal being used as a reference. Two comparator circuits that output rectangular wave signals whose rising and falling points are zero crossing points that transition to positive and negative regions when compared with voltage, and exclusive use of the two rectangular wave signals output by the two comparator circuits. an exclusive OR circuit that performs a logical sum and outputs a rectangular wave signal that repeats a high level period and a low level period determined by zero crossing points of the sine wave signal and the cosine wave signal; a counter circuit that measures a timetable of high-level periods and low-level periods of a rectangular wave signal to be output; a difference detection circuit that detects a time length difference between level periods as an offset amount and outputs it as a digital signal; a D/A converter that converts the output of the difference detection circuit into an analog signal; and a D/A converter that converts the output of the D/A converter to the An angle signal offset correction circuit comprising: two adding circuits that add to a sine wave signal and a cosine wave signal to correct an offset amount.