JPH0897873A - Orthogonal modulator - Google Patents

Abstract

PURPOSE: To enable the automatic adjustment to be executed in phase adjustment and offset by executing closed-loop control by means of negative feedback. CONSTITUTION: The orthogonality of a modulation wave and the difference between Pch offset and Qch are detected by a logic part 10 from the conversion outputs 105 and 106 of a first frequency converter 5 and the second frequency converter 6. The logic part 10 generates negative feedback signals 10a, 10b and 10c for adjusting the phase shift quantity in a phase adjusting equipment 9 and the output levels of a first off-set adjusting equipment 3 and the second offset adjusting equipment 4 in accordance with an orthogonality deviation and offset difference. Thus, precise phase adjustment and offset adjustment can be executed by closed-loop control by negative feedback.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to phase adjustment and offset adjustment in a quadrature modulator.

[0002]

2. Description of the Related Art FIG. 2 is a block circuit diagram showing a conventional quadrature modulator. This conventional quadrature modulator includes a first digital-analog converter 1 for converting a Pch digital signal Pin into an analog signal, a second digital-analog converter 2 for converting a Qch digital signal Qin into an analog signal, The level of the output 101 of the first digital-analog converter 1 is adjusted, the level of the output of the first offset adjuster 3 that outputs the level adjustment signal 103 and the output of the second digital-analog converter 2 are adjusted, and the level is adjusted. Adjustment signal 10
A second offset adjuster 4 which outputs 4 and an oscillator 8 which has two oscillation outputs 8a and 8b and has a phase difference of 90 degrees between the first oscillation output 8a and the second oscillation output 8b, A frequency difference signal 105 representing the difference between the frequency of the output 103 of the first offset adjuster 3 and the frequency of the first oscillation output 8a.
The first frequency converter 5 for generating the
Phase adjuster 9 for adjusting the phase of b, frequency of output 109 of phase adjuster 9 and output 1 of second offset adjuster 4
The second frequency converter 6 for generating the frequency difference signal 106 representing the difference with the frequency of 04, and the first frequency difference signal 105.
And the second frequency difference signal 106 are combined and the combined signal is output as the modulated wave 107, the ROM 20 in which the data is written, and the data 102 from the ROM 20.
Is read and the phase adjuster 9, the first offset adjuster 3 and the second offset adjuster 4 are controlled. In this conventional quadrature adjuster, the control data of each adjuster corresponding to the setting of the quadrature modulator is registered in the ROM 20 in advance, and the logic unit 21 reads the data 120 corresponding to the setting of the quadrature modulator from the ROM 20. , The phase adjuster 9, the first offset adjuster 3, and the second offset adjuster 4 are controlled.

As a document of the prior art of FIG. 2, Japanese Patent Laid-Open No. 2-8
There is 6225. This prior art document describes the phase adjustment, but does not disclose the offset adjustment for correcting the level difference between Pch and Qch.

[0004]

The control data is obtained by manually adjusting the phase and offset and registering the data at that time in the ROM. However, there are individual differences among the modulators, and for all modulators Since manual adjustment is required, circuit adjustment is complicated and adjustment man-hours are required.

[0005]

In order to solve the above problems, the present invention provides the following means.

A first digital-analog converter for converting a Pch digital signal into an analog signal, a second digital-analog converter for converting a Qch digital signal into an analog signal, and the first digital-analog converter. A first offset adjuster that adjusts the output level, a second offset adjuster that adjusts the output level of the second digital-analog converter, and a first offset adjuster having first and second oscillation outputs. 90 between the oscillation output and the second oscillation output
An oscillator having a phase difference of 1 degree, and a first frequency converter that generates a first frequency difference signal representing a difference between an output frequency of the first offset adjuster and a frequency of the first oscillation output, A phase adjuster that adjusts the phase of the second oscillation output, and a second frequency difference signal that generates a second frequency difference signal that represents the difference between the frequency of the output of the phase adjuster and the frequency of the second oscillation output. A frequency converter, a synthesizer that synthesizes the first frequency difference signal and the second frequency difference signal, and outputs the synthesized signal as a modulated wave, a phase shift amount in the phase adjuster, and the first and the second In a quadrature modulator having a logic unit for controlling an output level in a second offset adjuster, the logic unit includes a quadrature of the first frequency signal and the second frequency signal and offsets of Pch and Qch. The difference between The amount of phase shift in the phase adjuster is controlled to improve the orthogonality, and the output levels of the first offset adjuster and the second offset adjuster are controlled to eliminate the offset difference. A quadrature modulator characterized in that.

The logic unit outputs a signal representing the orthogonality of the first and second frequency difference signals to the phase adjuster as a phase control signal, and detects the signal from the first and second frequency difference signals. The quadrature modulator according to the above, wherein a signal representing a difference in offset between Pch and Qch is output to the first and second offset adjusters as an offset control signal.

[0008]

In the present invention, due to the above configuration, Pch and Qc
The orthogonality and offset difference of the frequency difference signal of h are controlled in a closed loop by negative feedback.

[0009]

1 is a block circuit diagram showing the configuration of an embodiment of the present invention. In this quadrature modulator, the Pch digital signal Pin and the Qch digital signal Qin are converted into analog signals 101 and 102 by the first digital-analog converter 1 and the second digital-analog converter 2.
The level is adjusted by the offset adjusters 3 and 4. Two oscillation outputs 8a, 8 with a phase difference of 90 degrees are output from the oscillator 8.
There is b. One of them 8b is via a phase adjuster 9. The first frequency converter 5 and the second frequency converter 6 calculate the frequency difference signal between the outputs 103 and 104 of the offset adjusters 3 and 4 and the above-mentioned oscillation outputs 8a and 8b.
05 and 106 are output. The frequency difference signal 105 output from the first frequency converter 5 and the frequency difference signal 106 output from the second frequency converter 6 are combined by the combiner 7 to obtain a modulated wave output 107. Further, the frequency difference signal 105 and the frequency difference signal 106 are input to the logic unit 10.

The logic unit 10 uses the Pch frequency difference signal 105.
Between Qch and the frequency difference signal 106 of Qch and Pch
And the difference in Qch offset is detected. Logic part 10
Is the phase control signal 10 when there is a deviation in orthogonality.
The amount of phase shift in the phase adjuster 9 is adjusted by c, and the signal 1
Correct the orthogonality of 05 and 106. Pch and Qch
If there is a difference in offset between the two, the output levels of the first offset adjuster 3 and the second offset adjuster 4 are adjusted by the offset control signals 10a and 10b to correct the offset between Pch and Qch.

[0011]

As described above, according to the present invention, the following effects can be obtained.

Since the phase and offset control has been closed loop control by negative feedback instead of the conventional open loop control, accurate phase adjustment and offset adjustment are possible.

ROM is prepared by manually adjusting the data.
Since it is not necessary to write in, the adjustment man-hour can be reduced.

[Brief description of drawings]

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

FIG. 2 is a block circuit diagram showing a conventional example.

[Explanation of symbols]

 1 1st digital-analog converter 2 2nd digital-analog converter 3 1st offset adjuster 4 2nd offset adjuster 5 1st frequency converter 6 2nd frequency converter 7 Combiner 8 Oscillator 9 Phase adjuster 10,21 Logic part 20 ROM

Claims (2)

[Claims] 1. A first digital-analog converter for converting a Pch digital signal into an analog signal, a second digital-analog converter for converting a Qch digital signal into an analog signal, and the first digital-analog conversion. A first offset adjuster for adjusting the level of the output of the converter, a second offset adjuster for adjusting the level of the output of the second digital-to-analog converter, and a first and a second oscillation output. An oscillator having a phase difference of 90 degrees between the first oscillation output and the second oscillation output, and a first representing the difference between the output frequency of the first offset adjuster and the frequency of the first oscillation output. A first frequency converter that generates the frequency difference signal of ## EQU1 ##, a phase adjuster that adjusts the phase of the second oscillation output, and a frequency of the output of the phase adjuster and a frequency of the second oscillation output. Show the difference A second frequency converter that generates a second frequency difference signal; a combiner that combines the first frequency difference signal and the second frequency difference signal and outputs the combined signal as a modulated wave; In a quadrature modulator having a phase shift amount in a phase adjuster and a logic unit for controlling an output level in the first and second offset adjusters, the logic unit includes the first frequency signal and the second frequency signal. The orthogonality with the frequency signal and the difference between the offsets of Pch and Qch are detected, the phase shift amount in the phase adjuster is controlled in the direction in which the orthogonality is improved, and the offset difference is eliminated. A quadrature modulator, which controls output levels of a first offset adjuster and a second offset adjuster. 2. The logic unit outputs a signal representing orthogonality of the first and second frequency difference signals to the phase adjuster as a phase control signal, and outputs the signal from the first and second frequency difference signals. The quadrature modulator according to claim 1, wherein a signal representing the detected difference between the Pch and Qch offsets is output to the first and second offset adjusters as an offset control signal.