JPH11112585A - Orthogonal signal generator - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide the orthogonal signal generator that generates two high frequency signals which has a phase difference by 90 degrees accurately through automatic adjustment. SOLUTION: A 1st frequency signal outputted from an oscillator 10 is distributed into two; the one is outputted as it is to a 1st output terminal 12a and the other is given to a 90 deg. phase shifter 14, where a phase difference of 90 deg. is provided to the other signal and the resulting signal is outputted to a 2nd output terminal 12b, resulting in generating two 1st frequency signals. A low frequency orthogonal signal generating means 30 outputs two 2nd frequency signals whose frequency (2nd frequency) is lower than the 1st frequency and which has a phase difference of 90 deg.. The 1st and 2nd frequency signals in pairs are mixed by 1st and 2nd balanced modulation means 32, 36 respectively and the outputs of them are given to an adder subtractor means 34, where they are summed, the sum is detected by a square detection means 38, and a filter means 40 extracts a signal having a frequency component twice the 2nd frequency from the detection output of the means 38. A control means 46 controls the 90 deg. phase shifter 14 so that the amplitude of the extracted signal is minimized.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a quadrature signal generator for generating two high frequency signals having a phase difference of exactly 90 degrees.

[0002]

2. Description of the Related Art In a digital quadrature modulator / demodulator or a phase-type SSB modulator / demodulator, two frequency signals having a high-frequency phase difference of exactly 90 degrees are used as local oscillation signals for modulation and demodulation. In need of.

A conventional quadrature signal generating apparatus for generating two frequency signals having a 90-degree phase difference branches an oscillation signal output from one oscillator into two, outputs one of the signals as it is, and outputs the other as it is. Two quadrature signals are generated by shifting the phase by 90 degrees via a phase shifter such as a differential integration circuit or an LC circuit. However, in such a differential integration circuit or an LC circuit, it is difficult to accurately set a phase difference of 90 degrees due to variations in the constants of elements constituting these circuits. In view of the above, there has been proposed a device capable of adjusting the phase shift amount of a 90-degree phase shifter.
As an example, a variable element such as a variable
The variable element is incorporated in a 0-degree phase shifter to adjust the constant of this variable element as appropriate, thereby absorbing variations in the constants of other elements. In this circuit, even if the adjustment can be performed so that the phase is accurately shifted by 90 degrees at the time of adjustment, an accurate 90-degree phase difference cannot be maintained if the element constant changes due to a change in ambient temperature or the like.

As a technique for further improving such a conventional technique, Japanese Patent Laid-Open No. 2-272910 has been proposed. This technology controls the amount of phase shift of the 90-degree phase shifter according to the phase shift angle from the 90-degree phase difference, and automatically adjusts the 90-degree phase difference with respect to variations and changes in element constants. That can be maintained.

[0005] The improved technique will be briefly described with reference to FIG. FIG. 6 is a block circuit diagram of the technique proposed in Japanese Patent Application Laid-Open No. 2-272910. In FIG. 6, the oscillator 1
The oscillation signal output from 0 is branched into two, one of which is output to the first output terminal 12a as it is, and the other is output to 90.
The phase is shifted by 90 degrees in the second output terminal 12.
b. Then, the two frequency signals output to the first output terminal 12a and the second output terminal 12b are multiplied and mixed by the mixer 16, and the output is provided to the amplifier 20 via the low-pass filter 18, and the amplified output Is integrated by the integration circuit 22 and supplied to the 90-degree phase shifter 14 as a control signal.

In such a configuration, the output signal of the mixer 16 includes a signal having an amplitude corresponding to a phase shift angle from a phase difference of 90 degrees between the two frequency signals and a signal having a frequency component twice as large as the oscillation signal. Consists of Therefore, only the signal corresponding to the deviation angle is extracted from the low-pass filter 18.
Then, by integrating the extracted signal by the integration circuit 22, a signal that is increased or decreased by a change amount corresponding to the shift angle with respect to a predetermined voltage corresponding to the integration constant is obtained. Therefore, the 90-degree phase shifter 14 is set so as to provide a 90-degree phase difference between the two frequency signals at a predetermined voltage corresponding to the integration constant. The phase shift amount of the phase shifter 14 is controlled to be slightly delayed, and to be advanced slightly when the phase shift amount shifts to the decreasing side. By performing the feedback control so that the output of the integration circuit 22 has a predetermined voltage value corresponding to the integration constant, the two frequency signals can maintain an accurate 90-degree phase difference.

[0007]

SUMMARY OF THE INVENTION The above-mentioned JP-A-2-27
The prior art proposed in Japanese Patent No. 2910 is extremely excellent in that the phase difference between two frequency signals is automatically corrected so as to become 90 degrees. However, the signal corresponding to the phase shift angle from the 90-degree phase difference extracted by the low-pass filter 18 is a minute DC signal, and the amplifier 20 that amplifies the signal is a DC amplifier. Therefore,
Since the amplifier 20 generates a DC drift due to a change in ambient temperature or the like, it is difficult to obtain an output signal proportional to the input signal due to the influence of the drift. Therefore, the phase difference between the two frequency signals may deviate from the accurate 90-degree phase difference due to the influence of the DC drift of the amplifier 20. In addition, the predetermined voltage having a magnitude corresponding to the integration constant output from the integration circuit 22 when the phase difference is 90 degrees may not be kept constant due to a change in the power supply voltage or the like.

The present invention has been made in view of the above-described problems of the prior art, and reduces the effects of ambient temperature changes and fluctuations in power supply voltage. It is an object of the present invention to provide a quadrature signal generator capable of generating two frequency signals.

[0009]

In order to achieve the above object, an orthogonal signal generating apparatus according to the present invention comprises a first orthogonal signal generating two first frequency signals having a phase difference of 90 degrees at a first frequency. Generating means, second quadrature signal generating means for generating two second frequency signals having a phase difference of 90 degrees with each other at a second frequency lower than the first frequency, and separating the first and second frequency signals one by one First and second balanced modulation means for mixing, addition and subtraction means for adding or subtracting the output of the first and second balanced modulation means, detection means for detecting the output of the addition and subtraction means, and output from the detection means Filter means for extracting a signal having a frequency signal component twice as high as the second frequency, and control means for controlling the first orthogonal signal generation means so that the signal extracted by the filter means is minimized. Equipment It is configured Te.

The first quadrature signal generating means branches an oscillation signal from one oscillator into two, outputs one of the signals as it is, and outputs the other by shifting the phase by 90 degrees by a 90-degree phase shifter. The control means may be configured to control the 90-degree phase shifter.

The first frequency is set to a high frequency used as a local oscillation signal of a wireless communication device, and the second frequency is set to 90
It is also possible to configure by setting a low frequency at which the degree phase difference can be accurately set.

[0012] The detection means may be constituted by a square detection means.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to FIGS. FIG. 1 is a block circuit diagram of an embodiment of a quadrature signal generation device according to the present invention. FIG.
(A) and (b) show mixed output signals of the first and second balanced modulation means in FIG. 1, respectively. FIG. 3 shows an addition output signal of the addition / subtraction means in FIG. FIG. 4 shows an extracted output signal of the filter means in FIG. FIG.
The magnitude of the amplitude of the extracted output signal of the filter means with respect to the phase shift angle from the 90 degree phase difference is shown.

First, the configuration will be described with reference to FIG. An oscillation signal having a high-frequency first frequency output from the oscillator 10 is split into two, one of which is output to the first output terminal 12a as it is, and the other is output to the 90-degree phase shifter 14 by the nine-phase shifter 14.
The phase is shifted by 0 degrees and output to the second output terminal 12b.
The oscillator 10 and the 90-degree phase shifter 14 have a 90-degree phase difference between the first output terminal 12a and the second output terminal 12b.
First quadrature signal generation means for generating and outputting two first frequency signals is formed. The high frequency first frequency is set, for example, to the frequency of a local oscillation signal used in modulation and demodulation of a wireless communication device.

Also, two second frequency signals having a phase difference of 90 degrees at the second frequency are generated and output from the low frequency orthogonal signal generating means 30 as the second orthogonal signal generating means. This second frequency is low enough that the low-frequency quadrature signal generation means 30 can accurately set a 90-degree phase difference. In addition, compared to the high frequency signal, the low frequency signal can be easily configured as a digital circuit.
Even with a circuit configuration that is not automatically adjusted, the phase shift control can be set relatively accurately, and the phase shift control having a 90-degree phase difference can be performed.
One frequency signal can be easily obtained.

Then, one of the first frequency signals output to the first output terminal 12a and the low frequency quadrature signal generation means 30
Is multiplied by the first balanced modulation means 32 as one mixer, and the mixed output is given to the addition / subtraction means 34. Further, the other first frequency signal output to the second output terminal 12b and the other second frequency signal output from the low frequency quadrature signal generation means 30 are connected to the second balanced modulation means 3 as the other mixer.
And the mixed output is given to the addition / subtraction means 34. The adding / subtracting means 34 generates the first balanced modulation means 32
Either addition or subtraction is performed on the mixed output of the second balanced modulation means 36 and the addition or subtraction is performed, and the addition or subtraction output is provided to the square detection means 38 as detection means.

Further, the detection output of the square detection means 38 is
The extracted output is supplied to a filter means 40, and the extracted output is supplied to an amplifier 42. The amplifier 42 is an AC amplifier. Then, the amplified output of the amplifier 42 is supplied to the level detecting means 44 and converted into a signal corresponding to the amplitude of the amplified output of the amplifier 42 and output. The level detecting means 44 is, for example, a rectifying / smoothing means for processing as an analog signal, and a peak-to-peak detecting means for processing as a digital signal. Then, a signal corresponding to the amplitude output from the level detecting means 44, that is, two first frequency signals having a 90-degree phase difference of the first quadrature signal generating means have magnitudes corresponding to the deviation angle from the 90-degree phase difference The control signal 46 is provided to the control means 46.

The control means 46 determines that the signal corresponding to the amplitude output from the level detection means 44 is minimized, that is, the deviation angle of the two first frequency signals from the phase difference of 90 degrees is zero. Thus, the 90-degree phase shifter 14 is controlled. Here, the control means 46 is composed of a microcomputer or the like, and slightly adjusts the phase shift of the 90-degree phase shifter 14 in either the advance direction or the delay direction, and determines whether the output of the level detection means 44 has increased or decreased, and increases it. If so, the 90-degree phase shifter 14 is phase-shifted in the opposite direction, and if it decreases, the 90-degree phase shifter 14 is phase-shifted in the same direction so that the output of the level detection means 44 is minimized. .

Next, with the above configuration, the filter means 4
From 0, two first frequency signals of the first quadrature signal generating means will be described as outputting signals having amplitudes corresponding to the phase shift angle from the phase difference of 90 degrees.

The first output terminal 12 of the first orthogonal signal generating means
The first frequency signal output to a is a · cosωt (here, 2πf1 = ω), and the second output terminal 12b
And has a deviation angle θ from the 90-degree phase difference.
The frequency signal is a · sin (ωt + θ), and the two second frequency signals of the low frequency quadrature signal generation unit 30 as the second quadrature signal generation unit are b · sinpt and b · c, respectively.
If it is ospt (here, 2πf2 = p), the mixed output of one of the first balanced modulation means 32 is expressed by Equation 1.

(Equation 1) Also, the mixed output of the other second balanced modulation means 36 is shown by Equation 2.

(Equation 2) Therefore, as shown in FIGS. 2A and 2B, the first balanced modulating means 32 and the second balanced modulating means 36
Signals of frequency components of f2 and f1 + f2 are output respectively.

When the outputs of the first balanced modulating means 32 and the second balanced modulating means 36 are added by the adding / subtracting means 34, the added output is expressed by the following equation (3).

(Equation 3) In Equation 3, if the deviation angle θ is small, cos
(Θ / 2) is almost “1”, and sin (θ / 2) is almost “0”. Therefore, the addition / subtraction means 34 outputs the signal shown in FIG.
As shown in the figure, a signal having a small amplitude corresponding to the shift angle θ of the frequency component of f1−f2 and a signal having a large amplitude of the frequency component of f1 + f2 are output. When the output of the first balanced modulation means 32 and the output of the second balanced modulation means 36 are subtracted by the addition / subtraction means 34, a signal having a large amplitude of the frequency component of f1-f2 and a signal having a small amplitude of the frequency component of f1 + f2 are obtained. can get.

Further, when the sum output of the adding / subtracting means 34 shown in Equation 3 is square-detected by the square detection means 38, the detection output is expressed by Equation 4.

(Equation 4) The first term of Equation 4 is a signal composed of a DC component and 2 (f1
+ F2), and the second term is composed of a signal consisting of a DC component and a signal consisting of 2 (f1-f2) frequency components. The third term is 2
It is composed of a signal composed of the frequency component of f1 and a signal composed of the frequency component of 2 · f2.

Therefore, the detection output of the square detection means 38 is converted into the DC component and the high frequencies 2 (f1 + f2) and 2 (f1-f).
The extracted output signal of the filter means 40 that blocks the frequency components of 2) and 2 · f1 and passes only the signal of the low-frequency frequency component of 2 · f2 is represented by Expression 5.

(Equation 5) Therefore, as shown in FIG. 4, a signal of a frequency component of 2 · f2 having a small amplitude corresponding to the shift angle θ is output from the filter means 40. Then, the deviation angle θ and this 2 ·
The amplitude of the signal of the frequency component of f2 is as shown in FIG.
As the deviation angle θ increases to 90 degrees on both the leading side and the lagging side, the amplitude of the signal of the frequency component of 2 · f2 also increases. If the shift angle θ is zero, the amplitude of the signal of the frequency component of 2 · f2 is the minimum.

Therefore, in this way, the filter means 4
By controlling the 90-degree phase shifter 14 so that the extracted output signal from 0 is minimized, the two first frequency signals output from the first output terminal 12a and the second output terminal 12b are exactly 90 degrees. It has a phase difference. With such control, variations in the constants of the elements constituting the 90-degree phase shifter 14 and changes in the constants due to changes in the ambient temperature do not affect the phase difference between the two first frequency signals.

The first quadrature signal generating means is not limited to a configuration in which one of the branched oscillation signals is phase-shifted by the 90-degree phase shifter 14. For example, each of the branched oscillation signals may be individually converted. A configuration in which the phases are shifted by 45 degrees in opposite directions to each other via a 45-degree phase shifter may be employed. In this case, the control means 46 may control one of the 45-degree phase shifters. The first balanced modulation means 32 and the second balanced modulation means 36 as mixers are those in which the first and second frequency signals as mixed inputs do not appear in the mixed output. Therefore, the first output as the mixed input is
If a mixer in which both the first and second frequency signals appear is used, and a filter means for blocking the first and second frequency signals is provided at a subsequent stage, an output signal similar to that of the balanced modulation means will be obtained as a result. Therefore, the first of the present invention
Needless to say, the balanced modulation means 32 and the second balanced modulation means 36 also include a circuit configuration which performs the same operation by combining the mixer and the filter means.

[0026]

As is apparent from the above description, the quadrature signal generating apparatus of the present invention has the following special effects.

In the quadrature signal generation device according to the first aspect, the first quadrature signal generation means is configured to minimize the signal corresponding to the phase shift angle from the 90 degree phase difference output from the filter means. By controlling, two first frequency signals having a phase difference of 90 degrees can be obtained. Moreover, even if there are variations in the constants of the elements constituting the circuit, changes in the constants due to changes in the ambient temperature, and fluctuations in the power supply voltage, the effects can be reduced. Therefore, it is possible to obtain two first frequency signals having an accurate and highly accurate 90-degree phase difference.

Further, in the quadrature signal generator according to the second aspect, the first quadrature signal generation means is constituted by one oscillator and a 90-degree phase shifter capable of adjusting the phase shift angle. ,
Its configuration is as simple as the conventional one, and there is no frequency difference between the two 90 degree phase difference signals output.

In the quadrature signal generator according to the third aspect, the second frequency signal mixed with the first frequency signal can be accurately converted even in a circuit configuration that does not require automatic adjustment of the phase difference by 90 degrees. Since the first frequency signal is adjusted based on an accurate 90-degree phase difference of the low-frequency signal, the first frequency signal is a high-frequency signal as a local oscillation signal used for modulation and demodulation of a wireless communication device. Even if there is, a phase difference of 90 degrees can be accurately set.

Further, in the quadrature signal generation device according to the fourth aspect, since the square detection means is used as the detection means, a signal having a small amplitude corresponding to the phase shift angle can be reliably detected.

[Brief description of the drawings]

FIG. 1 is a block circuit diagram of an embodiment of a quadrature signal generation device according to the present invention.

2 (a) and 2 (b) show mixed output signals of the first and second balanced modulation means in FIG. 1, respectively.

FIG. 3 shows an addition output signal of the addition / subtraction means in FIG. 1;

FIG. 4 shows an extracted output signal of the filter means in FIG.

FIG. 5 shows the magnitude of the amplitude of the extracted output signal of the filter means with respect to the phase shift angle from the 90 ° phase difference.

FIG. 6 is a block circuit diagram of a technique proposed in Japanese Patent Application Laid-Open No. 2-272910.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Oscillator 12a 1st output terminal 12b 2nd output terminal 14 90 degree phase shifter 30 Low frequency quadrature signal generation means 32 1st balance modulation means 34 Addition / subtraction means 36 2nd balance modulation means 38 Square detection means 40 Filter means 46 Control means

Claims (4)

[Claims] A first quadrature signal generating means for generating two first frequency signals having a phase difference of 90 degrees from each other at a first frequency;
To generate two second frequency signals having a phase difference of two degrees
Orthogonal signal generation means, first and second balanced modulation means for mixing the first and second frequency signals one by one, and addition / subtraction means for adding or subtracting the output of the first and second balanced modulation means, Detecting means for detecting the output of the adding / subtracting means, filtering means for extracting a signal having a frequency component twice as large as the second frequency from the output of the detecting means, and the magnitude of the signal extracted by the filtering means Control means for controlling the first orthogonal signal generation means so as to minimize the orthogonal signal generation means. 2. The quadrature signal generation device according to claim 1, wherein said first quadrature signal generation means splits an oscillation signal from one oscillator into two, and outputs one of them as it is,
A quadrature signal generation device, wherein the other is shifted by 90 degrees by a 90-degree phase shifter and output, and the control means controls the 90-degree phase shifter. 3. The quadrature signal generation device according to claim 1, wherein the first frequency is set to a high frequency used as a local oscillation signal of a wireless communication device, and the second frequency is set to a value that can accurately set a phase difference of 90 degrees. A quadrature signal generation device characterized by being set to a frequency. 4. The orthogonal signal generation device according to claim 1, wherein said detection means is constituted by a square detection means.