JP3244407B2 - Phase modulation circuit - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a phase modulation circuit,
In particular, for example, the present invention relates to a phase modulation circuit used for adjusting the phase of an external reference synchronization signal input to a TBC (time base collector).

[0002]

2. Description of the Related Art In order to adjust the phase of an external synchronizing signal of this kind, it is necessary to shift the phase of a sine wave. It can be applied. That is, a sine wave having a phase difference of 90 ° is applied to each of the two double balanced modulators, and two types of voltages S and C are applied to the voltage gain control inputs of the respective double balanced modulators. When the output of the detector is added by a resistor, the phase difference between the output and the input is proportional to tan ^-1 C / S.

[0003] US Patent No. 4,868,428 [G06G 7/0 issued on September 19, 1989]
0, H03K 5/13], an accurate phase shift amount is obtained using two ROMs to generate the control voltages S and C described above.

[0004]

In the above-mentioned prior art,
There has been a problem that the memory capacity increases and the cost increases as the control voltage change accuracy increases. Therefore, a main object of the present invention is to provide a phase modulation circuit capable of controlling the amount of phase shift accurately without increasing the memory capacity.

[0005]

SUMMARY OF THE INVENTION The present invention provides an
° In a phase modulation circuit including two double balanced modulators each receiving an input signal having a different phase and control voltage applying means for applying a gain control voltage to the double balanced modulator, the control voltage applying means has a polarity Polarity indicated by data
Value data at predetermined timing
Means for adding the value indicated by the voltage value data to a predetermined time.
Comparison means for comparing with a threshold value in the timing, and the ratio of the comparison means
Update the polarity indicated by the polarity data according to the comparison result.
A phase modulation circuit including a new means .

[0006]

The control voltage applying means is, for example, a microcomputer.
The microcomputer calculates the data of the control voltages S and C based on the initial values of the control voltages S and C preset in the initial value memory. Specifically, the microcomputer calculates the data of the control voltage (S, C) by switching the sign of the voltage value according to an algorithm stored in the memory in advance so as not to exceed a predetermined maximum value and minimum value. I do. These two voltage data are converted into a control voltage signal by, for example, a D / A converter and input to the double balanced modulator.

[0007]

According to the present invention, since the control voltage (S, C) is calculated based on the initial value, only the program for the operation and the initial value data are stored in the memory. It is sufficient if there is a capacity, and the memory capacity is small. The above and other objects, features and advantages of the present invention will become more apparent from the following detailed description of embodiments with reference to the drawings.

[0008]

Referring to FIG. 1, a phase modulation circuit 10 of this embodiment includes an input terminal 12, and from this input terminal 12,
For example, a sine wave carrier of 4.4 MHz is input and supplied to one double balanced modulator 14a and 90 ° phase shifter 16. In the 90 ° phase shifter 16, the sine wave carrier inputted from the input terminal 12 is converted into a cosine wave signal having a phase difference of 90 ° and inputted to the other double balanced modulator 14b.

The microcomputer 18 has two initial value memories 26
And memories 28 and 28 which have 2
Initial value data of two different control voltages (S, C) is preset. When a control voltage output request signal is input to the microcomputer 18, the microcomputer 18 stores the control voltage (S, C) in a memory (not shown) of the microcomputer 18 based on the initial value data in the initial value memories 26 and 28. Calculate according to the algorithm. The control voltage (S, C) output from the microcomputer 18 is supplied to the D / A converters 20a and 20b
Is converted to an analog value. Then, the control voltages (S, C) are input to the voltage gain control input terminals of the double balanced modulators 14a and 14b. And register 2
Via the 2a and 22b, voltages having phases different from each other by 90 ° are combined, and a combined voltage is output from the output terminal 24.

As described above, the program for calculating the variation of the control voltage (S, C) is stored in the memory of the microcomputer 18 in advance. Referring to FIG. 2, a sine wave carrier is input from input terminal 12 and control voltage S is applied to microcomputer 18.
The processing operation of the microcomputer 18 when the output request signal is output will be described.

First, in step S1, processing number i
Is given (i = 1), and the control voltage S
And the initial value (S, *) of the positive / negative slope * of the control voltage S =
(0, +) is set. Then, in step S3, it is determined whether the control voltage S exceeds a maximum value (for example, 128). If it exceeds the maximum value, that is, if it is point a shown in FIG. 4, in step S5, a minus sign is added to the slope * of the control voltage S, and the positive and negative of the slope * of the control voltage S are changed. Conversely set. When the control voltage S does not exceed the maximum value, it is determined in step S7 whether the control voltage S is smaller than a minimum value (for example, -128).

If it is smaller than the minimum value, step S
In step 9, similarly to step S5, a minus sign is added to the slope * of the control voltage S, and the polarity of the slope of the voltage S is set to the opposite (point b in FIG. 4). If the control voltage S is larger than the minimum value, in step S11, 1 is added to the process number i, and 2 is added to the control voltage S, and the processing operations after step S3 are repeated. If the slope * of the control voltage S is negative, 2 is subtracted from the control voltage S in step S11.

Referring to FIG. 3, similarly, the processing operation of microcomputer 18 when a control voltage C output request signal is output to microcomputer 18 will be described. Step S
Similarly to 1, in step S13, the process number i, the control voltage C, and the initial value (i, C, *) = (1, 128, −) at the slope * of the control voltage C are set. Subsequently, in step S15, it is determined whether the control voltage C is smaller than a minimum value (for example, -128). If smaller than the minimum value, in step S17,
The polarity of the slope * of the control voltage C is changed by adding a minus sign to the slope * of the control voltage C. That is, FIG.
As shown at point d, when the control voltage C is determined to be smaller than the minimum value, the control voltage C that monotonically decreases has the opposite polarity of the slope *, and the control voltage C monotonically increases from point d. Switch to.

If it is determined that the control voltage C is higher than the minimum value, it is determined in step S19 whether the control voltage C is higher than the maximum value (for example, 128). If it is larger than the maximum value, in step S21,
As in step S17, the polarity of the slope * of the control voltage C is switched in reverse (point e in FIG. 4). If it is smaller than the maximum value, in step S23, the process number i is set to 1
However, 2 is added to (or subtracted from) the control voltage C, and the processing operations after step S15 are repeated.

Therefore, as shown in the graph of FIG.
The microcomputer 18 outputs 8-bit digital values of two broken line control voltages S and C. in this way,
Since the microcomputer 18 is configured to calculate the change amounts of the control voltages S and C according to the algorithm shown in FIGS. 2 and 3, a program for calculating the control voltages S and C and an initial It is only necessary to store the value data, and the memory capacity is small. Further, the memory capacity does not increase with the improvement of the change accuracy.

[Brief description of the drawings]

FIG. 1 is a block diagram showing one embodiment of the present invention.

FIG. 2 is a flowchart showing a processing operation of the microcomputer of FIG. 1 for calculating a change amount of a control voltage S;

FIG. 3 is a flowchart showing a processing operation for calculating a change amount of a control voltage C in the microcomputer of the embodiment in FIG. 1;

FIG. 4 is a graph showing control voltages S and C calculated in the embodiment of FIG. 1;

[Explanation of symbols]

 Reference Signs List 10: phase modulators 14a, 14b: double balanced modulator 16: 90 ° phase shifter 18: microcomputer 26, 28: initial value memory

Claims (1)

(57) [Claims] 1. A phase modulation circuit comprising: two double balanced modulators each receiving input signals having a phase difference of 90 ° from each other; and control voltage applying means for applying a gain control voltage to each of the double balanced modulators. The control voltage applying means has a polarity indicated by polarity data
Numerical values are stored at predetermined timings as voltage value data of the gain control voltage.
Addition means for adding the value indicated by the voltage value data to the
Comparing means for comparing with a threshold value at a constant timing, and the ratio
The polarity indicated by the polarity data according to the comparison result of the comparing means.
A phase modulation circuit comprising a polarity updating means for updating .