JPH06284158A - Orthogonal phase modulator - Google Patents

Abstract

PURPOSE:To reduce modulation distortion by eliminating waveform fluctuation of a carrier due to the fluctuation of a power supply voltage or the like. CONSTITUTION:A multiplier circuit 11 receiving an input carrier S1, generating a carrier including a frequency component being a prescribed multiple of a frequency of carrier S1 to provide the carrier controls the amplitude of the carrier constant. Then the carrier is given to 1st and 2nd flip-flop circuits 4, 5 via a band pass filter 12 to generate two sets of carriers whose phases are orthogonal to each other. Modulation outputs resulting from modulating the two carriers with a signal wave are added by an adder circuit 8 and the sum is outputted as a phase modulation signal S16. Thus, phase distortion due to amplitude fluctuation or the like of the carrier is far reduced more than that of a conventional modulator by controlling the amplitude of the carrier inputted to the flip-flop circuits 4, 5 constant in this way.

Description

Detailed Description of the Invention

[0001]

[Table of Contents] The present invention will be described in the following order. Industrial Application Conventional Technology (FIGS. 4 and 5) Problem to be Solved by the Invention Means for Solving the Problem (FIGS. 1 and 2) Action (FIG. 3) Example (FIGS. 1 to 3) (1) Configuration of Quadrature Phase Modulation Circuit (FIGS. 1 and 2) (1-1) Overall Configuration (FIG. 1) (1-2) Configuration of Waveform Shaping Circuit 13 (FIG. 2) (2) Operation of Embodiment and Effects (FIG. 3) (3) Other Examples Effects of the invention

[0002]

FIELD OF THE INVENTION The present invention relates to a quadrature modulator,
For example, it is suitable for application to a modulator in a mobile communication device.

[0003]

2. Description of the Related Art Conventionally, a quadrature phase modulation circuit 1 having a structure as shown in FIG. 4 has been used for this kind of communication equipment. The quadrature phase modulation circuit 1 receives an input carrier S1 via a squaring circuit 2 and a bandpass filter (BPF) 3 in sequence, and thereby oscillates at a frequency 2f that is twice the frequency f of the input carrier S1. (FIG. 5A) shows flip-flop circuits 4 and 5 (hereinafter, FF circuits 4 and 5).
Is said to be supplied to.

Here, the bandpass filter 3 has three or more high frequency components (3f, 4f, 5f ...) Which are generated at the same time when the squaring circuit 2 generates a frequency component twice the frequency of the input carrier wave S1. ) Is removed. The FF circuits 4 and 5 are adapted to take in signals in synchronization with either the rising edge or the falling edge of the carrier wave S2, and as shown in FIGS. 5B and 5C, the phases thereof are 90 degrees. ° Different output pulses Q1 and Q2
Is output.

At this time, the FF circuits 4 and 5 output the output pulses Q1B and Q2B of opposite phase to the output pulses Q1A and Q2A at the same time as the output pulses Q1A and Q2A, and supply them to the mixers 6 and 7. Mixers 6 and 7 output pulses Q1A, Q
Quadrature-modulated four-phase modulation output S7 is generated by modulating 1B, Q2A, and Q2B with modulation signals S3 and S4, and outputting modulated waves S5 and S6, which are modulation outputs, to addition circuit 8 and adding them. is doing.

[0006]

However, in the case of an electronic device such as a mobile phone in which the power supply voltage is easily changed during use, the waveform of the carrier wave S2 output from the bandpass filter 3 due to the change in the power supply voltage is changed. If it is distorted (that is, if the amplitude becomes small or the rise time or fall time deviates back and forth), the timing of the signals taken in by the FF circuits 4 and 5 will change.

At this time, if the phase difference between the output pulses Q1A and Q2A is relatively deviated while maintaining 90 degrees, normal demodulation can be performed, but in general, this relationship is not always maintained. There is a problem that the modulation distortion occurs due to the delay or shortening of the rising timing and the falling timing.

Although the carrier wave S2 output from the bandpass filter 3 is a sine liquid, the output becomes unstable during the period when the input levels of the modulated waves S3 and S4 are constant, which easily causes jitter, and the modulated output waveform S5. And the phase difference between S6 is 9
If it is not 0 °, it may cause modulation distortion.

The present invention has been made in consideration of the above points, and it is an object of the present invention to propose a quadrature phase modulator having little phase distortion regardless of the presence or absence of waveform distortion of a carrier wave.

[0010]

In order to solve such a problem, according to the present invention, a carrier wave oscillating at a frequency that is a predetermined multiple of the frequency f of the input carrier wave S1 is generated and its amplitude is controlled to be constant. A multiplying circuit 11 for outputting
A bandpass filter 12 that extracts and outputs only a specific frequency component from the output of the multiplication circuit 11, and a first flip-flop circuit 4 that inputs the output of the bandpass filter 12 and switches the output state at the rising time of the output. , A second flip-flop circuit 5 which inputs the output of the band pass filter 12 and switches the output state at the time of the fall of the output, and the first and second flip-flop circuits 4 and 5 which output the first flip-flop circuit 4 and the second flip-flop circuit 5, respectively. The output signals Q5A, Q5B and Q6A, Q6B of
And the second output signal to the first and second signal waves S3 and S
The first and second mixing circuits 6 that output the first and second modulation outputs S14 and S15 by modulating the signals by
And 7 and the addition circuit 8 for inputting and adding the first and second modulation outputs S3 and S4 and outputting as the phase modulation signal S16.

Further, in the present invention, the multiplication circuit 11 for generating and outputting a carrier wave oscillating at a frequency that is a predetermined multiple of the frequency of the input carrier wave S1, and only a specific frequency component from the output of the multiplication circuit 11 A bandpass filter 12 for extracting and outputting, and a waveform shaping circuit for inputting the output of the bandpass filter 12, dividing the output and converting it into a carrier wave of a predetermined frequency, and then shaping and outputting the waveform of the carrier wave. 13 and the output of the waveform shaping circuit 13 are input, and the output state is switched when the output rises.
Second flip-flop circuit 4 and a second flip-flop circuit 5 for inputting the output of the waveform shaping circuit and switching the output state at the time of the fall of the output, and the first and second flip-flop circuits 4 and 5 for outputting. 1
And the second output signals Q5A, Q5B, and Q6A, Q6B, and the first and second output signals are modulated by the first and second signal waves S3 and S4. First and second output of two modulated outputs S14 and S15
Mixing circuits 6 and 7, and first and second modulation outputs S14
And S15 are input and added, and an adding circuit 8 for outputting as a phase modulation signal S16 is provided.

[0012]

By controlling the gain of the multiplication circuit 11 so that the amplitude of the carrier wave oscillated at a frequency that is a predetermined multiple of the frequency of the input carrier wave S1 is constant, the amplitude is always constant regardless of the fluctuation of the power supply voltage. Can be applied to the first and second flip-flop circuits 4 and 5. As a result, it is possible to effectively reduce fluctuations in phase distortion caused by fluctuations in rise time and fall time.

Further, the carrier wave of a specific frequency extracted by the band pass filter 12 is given to the first and second flip-flop circuits 4 and 5 through the waveform shaping circuit 13, so that the phase difference between the output waveforms is always constant. Can be controlled to
It is possible to effectively reduce the phase distortion due to the influence of jitter or the like.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS (1) Configuration of Quadrature Phase Modulation Circuit (1-1) Overall Configuration In FIG. 1, reference numeral 10 denotes a quadrature phase modulation circuit as a whole, and an input carrier S1 is inputted through a quadruple multiplication circuit 11. The frequency of the input carrier S1 is multiplied by four, and other harmonic components (f2, f8 ...) Generated at that time are removed by the band pass filter 12, and the waveform shaping circuit 13 is provided.
It is designed to be supplied to.

The quadruple multiplication circuit 11 receives an amplitude adjustment signal S11 from the outside, and controls the gain so that the quadruple multiplication carrier S12 has a constant amplitude regardless of the fluctuation of the power supply voltage. The waveform shaping circuit 13 has a sine wave-shaped quadruple carrier S12 controlled to have a constant amplitude in this manner.
Waveform is shaped into a rectangular wave and divided into halves to remove the influence of waveform distortion, and the quadruple carrier wave S12
The carrier wave S13 rising or falling at constant intervals is always output regardless of the presence or absence of waveform distortion.

The flip-flop circuits 4 and 5 can always output rectangular outputs Q5A and Q6A whose phases are different from each other by 90 ° to the mixers 6 and 7 by fetching data at the rising and falling timings of the carrier wave S13. . As a result, the rectangular outputs Q5B and Q6B, which are output from the flip-flop circuits 4 and 5 and are 180 ° out of phase with the rectangular outputs Q5A and Q6A, can also be out of phase with each other by 90 °.

As a result, from the mixers 6 and 7 to the adder circuit 8
The phases of the modulated waves S14 and S15 output to each other are orthogonal to each other, and the adder circuit 8 can always output the four-phase modulated output S15 having no phase fluctuation regardless of the fluctuation of the power supply voltage or the like.

(1-2) Configuration of Waveform Shaping Circuit 13 The waveform shaping circuit 13 supplies the 4 × carrier wave S12 input from the bandpass filter 12 to the 1/2 divider circuit 15 via the buffer amplifier 14 and the 4 × carrier wave. By taking in a signal at the rising timing of S12, the frequency is divided in half with respect to the quadruple carrier wave S12, and a divided output S12A is output.

Here, the exclusive NOR circuit 16 is
The frequency-divided output S12A is delayed by a quarter cycle by passing through the delay circuit 17 and the frequency-divided output S12A is input, and the inverted output of the exclusive OR of each input signal is output as the carrier wave S13. To do. The delay circuit 17 is formed by cascade connection of odd-numbered stages of inverters.

At this time, the duty ratio of the carrier S13 is
The quadruple carrier wave S12 is always constant regardless of the variation of the duty ratio. That is, the pulse width of the period in which the waveform rises in one cycle of the quadruple carrier wave S12 is T1, T2, T1, T3 ...
As shown in FIG. 3A, the image is distorted due to the modulation.

However, since the period of one cycle is constant regardless of the presence or absence of waveform distortion, the frequency division output S12A (see FIG. 3).
(B) shows an output waveform with a duty ratio of 50%. Since the phase of the frequency-divided output S12A and its delayed output (FIG. 3 (C)) is always different by 1/4 cycle, the waveform of the carrier wave S13 which is the output obtained by inverting the exclusive OR is shown in FIG. 3 (D). Thus, the waveform has a duty ratio of 50%.

That is, the output waveform of the exclusive NOR circuit 16 is always a constant waveform regardless of the presence or absence of waveform distortion, and its duty ratio is 50%. As a result, the timing for starting and stopping the carrier wave S13 is 9
The 0 ° phase will be different.

(2) Operation and Effect of Embodiment The modulation operation of the quadrature phase modulation circuit 10 having the above-mentioned configuration will be described. The quadrature modulation circuit 10 has an input carrier wave S
When 1 is input, it is supplied to the waveform shaping circuit 13 through the quadrupling circuit 11 and the bandpass filter 12, and the quadrupling carrier S12 having a frequency multiplied by 4 with respect to the frequency of the input carrier S1.

At this time, 4 output from the quadruple multiplication circuit 11
Since the amplitude of the multiplied carrier S12 is kept constant regardless of the fluctuation of the power supply voltage by the automatic adjustment by the gain adjustment signal S11, the phase shift caused by the fluctuation of the power supply voltage as in the conventional case is removed at this stage.

Further, the waveform shaping circuit 13 has a quadruple carrier wave S.
4 depending on the rising timing of the waveform in 12
By dividing the frequency of the multiplied carrier S12 by half, it is possible to eliminate the influence of the variation in the timing of the falling edge of the waveform of the multiplied carrier S12.

As a result, the phases of the rectangular outputs Q5A, Q6A, Q5B and Q6B which are the outputs of the FF circuits 4 and 5 which operate at the rising and falling timings of the carrier wave S13 are deviated from each other by 90 °.

The rectangular outputs Q5A and Q6A are given by

[Equation 1]

[Equation 2] And the signal waves input to the mixers 6 and 7 are

[Equation 3]

[Equation 4] Then, the four-phase modulation output S7 output from the adding circuit 8
Is

[Equation 5] X (t) in.

As described above, the adder circuit 8 becomes a signal obtained by modulating a carrier wave having the same angular frequency (± ω0) with the signal wave Ψ (t) and having no phase distortion. The phase output S7 can be output.

According to the above configuration, the frequency of the input carrier S1 is once multiplied by 4 and converted into the 4 multiplied carrier S12, and then the 4 multiplied carrier S12 is divided into halves and the waveform-shaped signal is generated. By supplying the carrier wave S13 to the FF circuits 4 and 5, it is possible to eliminate the influence of fluctuations in the rising and falling times of the waveform that occur when the input carrier wave S1 is modulated to the quadruple carrier wave S12 in the quadrupling circuit 11. It is possible to effectively prevent the phase distortion.

(3) Other Embodiments In the above embodiment, the 1/2 divider circuit 15 is
The case where the output obtained by dividing the quadrupled carrier wave by half is obtained by detecting the rising edge of the carrier wave S13 has been described, but the present invention is not limited to this, and the quadruple carrier wave S12 is detected by detecting the trailing edge. May be divided by half.

In the above embodiment, the delay circuit 1
Although the case where 7 is configured by connecting odd-numbered stages of inverters in cascade has been described, the present invention is not limited to this, and other delay elements may be used.

Further, in the above-mentioned embodiment, the case where the frequency of the input carrier wave is once multiplied by 4 and then divided by half is described, but the present invention is not limited to this, and the frequency of the input carrier wave is 8 times. It can also be applied when doubling or more.

Further, in the above-described embodiment, the case where the amplitude of the quadruple carrier wave S12 is controlled to a constant amplitude by giving the gain adjustment signal S11 to the quadruple multiplier circuit 11 has been described, but the present invention is not limited to this. The amplitude of the output signal may be controlled to be constant by giving the gain adjustment signal S11 to the buffer circuit 14 in the waveform shaping circuit 13.

Further, in the above embodiment, the carrier wave S
The case where the amplitude of 12 is controlled to be constant, the waveform is shaped, and the carrier wave S13 after the waveform shaping is applied to the first and second flip-flop circuits 4 and 5 has been described, but the present invention is not limited to this. It suffices to control the amplitude of S13 to be constant, and vice versa.

Further, in the above-mentioned embodiment, the case where the quadrature phase modulation circuit 10 is used in the mobile phone has been described, but the present invention is not limited to this, and is also used in the high frequency modulator in other electronic equipment. Widely applicable.

[0036]

As described above, according to the present invention, by controlling the amplitude of the carrier wave output in the multiplication circuit for multiplying the frequency of the input carrier wave by a predetermined value and outputting the same, the carrier wave caused by the fluctuation of the power supply voltage is controlled. The phase shift can be eliminated, and the modulation distortion can be further reduced compared to the conventional case. Further, as described above, according to the present invention, by connecting the waveform shaping circuit between the bandpass filter circuit and the first and second flip-flop circuits, the phase shift of the carrier can be eliminated, and the modulation distortion can be eliminated. It can be further reduced compared to the conventional case.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of a quadrature modulator according to the present invention.

FIG. 2 is a block diagram for explaining a waveform shaping circuit.

FIG. 3 is a signal waveform diagram for explaining the operation.

FIG. 4 is a block diagram for explaining a conventional quadrature phase modulator.

FIG. 5 is a signal waveform diagram for explaining the principle of quadrature phase modulation.

[Explanation of symbols]

1, 10 ... Quadrature phase modulation circuit, 2 ... Square circuit, 3,
12 ... band pass filter, 4, 5 ... flip-flop circuit, 6, 7 ... mixer, 8 ... addition circuit, 11 ...
... 4 multiplication circuit, 13 ... waveform shaping circuit, 14 ... buffer amplifier, 15 ... 1/2 frequency divider circuit, 17 ... delay circuit.

Claims (6)

[Claims] 1. A multiplication circuit for generating a carrier wave oscillating at a frequency that is a predetermined multiple of the frequency of the input carrier wave, and controlling and outputting the carrier wave at a constant amplitude, and a specific frequency from the output of the multiplier circuit. A bandpass filter that extracts and outputs only the component, and a first flip-flop circuit that inputs the output of the bandpass filter and switches the output state at the rising time of the output, and inputs the output of the bandpass filter, A second flip-flop circuit that switches the output state at the time of the fall of the output, and the first and second output signals output from the first and second flip-flop circuits are input to the first and second flip-flop circuits.
A first and a second mixing circuit for outputting a first and a second modulated output by modulating the output signal of 1 with a first and a second signal wave, and the first and the second modulated outputs. A quadrature phase modulator comprising: an addition circuit that inputs, adds, and outputs as a phase modulation signal. 2. A multiplier circuit for generating and outputting a carrier wave that oscillates at a frequency that is a predetermined multiple of the frequency of the input carrier wave, and a band for extracting and outputting only a specific frequency component from the output of the multiplier circuit. The pass filter and the output of the band pass filter are input, the output is frequency-divided and converted into a carrier of a predetermined frequency, and then the waveform of the carrier is shaped and output. A first flip-flop circuit that inputs an output and switches the output state at the rising time of the output; and a second flip-flop circuit that inputs the output of the waveform shaping circuit and switches the output state at the falling time of the output. The first and second output signals output from the first and second flip-flop circuits are input, and the first and second output signals are input.
A first and a second mixing circuit for outputting a first and a second modulated output by modulating the output signal of 1 with a first and a second signal wave, and the first and the second modulated outputs. A quadrature phase modulator comprising: an addition circuit that inputs, adds, and outputs as a phase modulation signal. 3. The multiplication circuit generates and outputs a carrier wave that oscillates at a frequency four times as high as the frequency of the input carrier wave, and the waveform shaping circuit divides the output of the band pass filter by two. 3. The quadrature phase modulation according to claim 2, wherein a carrier wave oscillating at a frequency twice as high as the frequency of the input carrier wave is output to the first and second flip-flop circuits by dividing the frequency by 1. vessel. 4. The multiplication circuit generates and outputs a carrier wave that oscillates at a frequency four times the frequency of the input carrier wave, and the waveform shaping circuit inputs a buffer that receives the output of the band pass filter. An input stage, a frequency dividing means for dividing the output of the buffer input stage into halves, and outputting a carrier wave oscillating at a frequency twice as high as the frequency of the input carrier wave as a divided output; 3. The quadrature phase modulation according to claim 2, further comprising: a delay output obtained by delaying the frequency output for a predetermined time and an exclusive OR of the frequency division output and outputting an inverted output of the logical OR. vessel. 5. The quadrature phase modulator according to claim 4, wherein the buffer input stage controls the output amplitude of the bandpass filter to be constant and outputs the carrier wave to the frequency dividing means. 6. The waveform shaping circuit obtains, in the logic stage, an exclusive OR of an output obtained by delaying the divided output by a quarter cycle and the divided output. The quadrature phase modulator according to.