JP3398989B2 - PSK modulator - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is suitable for use in a transmitter of a digital communication system, and relates to a modulator which can be all-digitalized and non-adjusted by being constituted by simple hardware. Is.

[0002]

2. Description of the Related Art FIG. 9 shows a conventional PSK (Phase Shift Keyi).
ng) is a block diagram showing a configuration of a modulator. This Figure 9
1 is a shift register, 2 is a ROM, the input data is shifted by the shift register 1, and the ROM 2
And the output of the ROM 2 is read to shape the waveform of the input data. The output of the ROM 2 is converted into analog by a digital / analog (hereinafter referred to as D / A) converter 3.

When converting the output of the ROM 2 to analog,
In the D / A converter 3, in order to prevent the influence of the aperture characteristic due to the sample and hold, band limitation is applied so that the folding component is removed by the built-in low-pass filter. This shift register 1, ROM 2, and D /
The A converter 3 constitutes a waveform shaping circuit A having a band limiting function.

The output of the D / A converter 3 is output to the modulation circuit B. The modulation circuit B is composed of a multiplier 4, a local oscillator 5, and a bandpass filter 6 (hereinafter, referred to as BPF) connected to a subsequent stage of the D / A converter 3.
The multiplier 4 has a frequency fc oscillated from the local oscillator 5.
Carrier signal is input. The multiplier 4 multiplies the carrier frequency signal fc by the output signal of the D / A converter 3 to switch the phase of the carrier frequency signal fc for each data rate, and the BPS 6 generates a signal component in a desired frequency band. By passing it, BPSK
(Binary Phase Shift Keying) modulation is realized.

[0005]

The conventional PSK modulator as shown in FIG. 9 is widely used because it has a simple hardware and can be constructed at low cost.
Since it is composed of analog elements, adjustment is necessary.
Further, when it is desired to change the data transmission rate, there is a drawback that there are many places that need to be changed, such as the LPF and BPF 6 of the D / A converter 3, and QPSK (Quad
When applied to multi-phase such as rature phase shift keying), analog elements such as phase shifters and hybrids will increase,
As a result, there is a problem that the number of adjustment points also increases.

The present invention has been made in view of the above-mentioned problems, and it is possible to eliminate the need for adjustment and improve productivity, and to simplify the hardware and to reduce the IC.
An object of the present invention is to provide a modulation device that can be downsized and downsized.

[0007]

In order to achieve the above object, the present invention is a PSK modulator for PSK modulating a carrier signal of a predetermined frequency based on input data, wherein the input data has a maximum value and a minimum value. And a waveform shaping circuit that shapes the waveform to an intermediate value, and the maximum value output from the waveform shaping circuit is passed through and the minimum value is inverted for each period of a frequency twice that of the carrier signal. After inserting the intermediate value in each cycle of four times the frequency of the signal, digital / analog conversion is performed in each cycle of the carrier signal to generate a BPSK modulated wave of the carrier signal, and an output signal of this modulating means. A bandpass filter for removing the aliasing component of the carrier signal included in the above and the aliasing component associated with the waveform shaping of the waveform shaping circuit. Characterized in that it comprises a.

According to the present invention, the modulation means includes a local oscillator that generates a signal having a frequency four times as high as that of the carrier signal, and a signal output from the local oscillator is the carrier signal and twice the carrier signal. A counter for dividing the frequency of the signal into a signal of the frequency, an exclusive OR circuit for exclusive ORing the carrier signal divided by the counter and the output signal of the waveform shaping circuit, and the exclusive OR circuit. Of the carrier signal and the intermediate value are switched in a cycle of twice the frequency of the carrier signal to be output, and a digital / analog converter for digital / analog converting the output signal of the selector. . Further, according to the present invention, the modulating means further includes a digital filter inserted in the preceding stage of the digital / analog converter to change the transmission rate of the BPSK modulated wave.

The present invention is also a PSK modulator for PSK modulating a carrier signal of a predetermined frequency based on first and second input data, wherein the first input data is converted into a maximum value, a minimum value and an intermediate value. A first waveform shaping circuit for shaping the waveform, a second waveform shaping circuit for shaping the second input data into a maximum value, a minimum value and an intermediate value, and a local oscillator for generating a signal having a frequency four times that of the carrier signal. A first modulating means for modulating the output signal of the local oscillator with the output of the first waveform shaping circuit to generate a BPSK modulated wave; and a signal obtained by phase-shifting the output signal of the local oscillator by 90 degrees. Second modulation means for modulating with the output of the two waveform shaping circuit to generate a BPSK modulated wave, and an output signal of the first modulation means are selected for each first select signal having a frequency twice that of the carrier signal. , The first selector for outputting the in-phase component of the carrier signal and the output signal of the second modulating means are selected for each second select signal having a frequency twice that of the carrier signal and inverting the first select signal. A second selector for outputting the quadrature component of the carrier signal,
An adder for adding the output of the first selector and the output of the second selector, a digital / analog converter for digital / analog converting the output signal of the adder, and an output signal of the digital / analog converter are included. A bandpass filter for removing the aliasing component of the carrier signal is provided.

[0010]

According to the present invention, by inputting the data input to the waveform shaping circuit, the waveform is shaped into the maximum value, the minimum value, and the intermediate value. The PSK modulated wave of the carrier signal is generated by passing through at every cycle of twice the frequency, inverting the minimum value, inserting an intermediate value at every cycle of the frequency of four times the carrier signal, and then performing digital / analog conversion. At the same time, the PSK modulated wave is input to the bandpass filter to remove the aliasing component of the carrier frequency and the aliasing component of the waveform shaping circuit. This allows for no adjustment,
The productivity can be improved, the hardware can be simplified, and the IC and the size can be reduced.

[0011]

Embodiments of the present invention will be described below with reference to the drawings. 1 is a block diagram showing the configuration of a BPSK modulator according to a first embodiment of the present invention. In FIG. 1, the same parts as those of the conventional example shown in FIG.

The waveform shaping circuit A includes a shift register 1 and an RO.
M2 and the input data are shift register 1
Then, the waveform of the input data is shaped by reading the output of the ROM 2 after sequentially shifting and inputting it to the ROM 2. The modulation circuit C is composed of a gate 7, a counter 8, a local oscillator 9, and a D / A converter 10 which are connected to the latter stage of the ROM 2. The maximum value, the minimum value, and the intermediate value (DC component) are output from the waveform shaping circuit A, and the output of the waveform shaping circuit A is input to the gate 7 of the modulation circuit C.

The gate 7 is, for example, 2 as shown in FIG.
It is composed of an exclusive OR circuit 7a for input and a selector 7b. The output of the ROM 2 of the waveform shaping circuit A is inputted to the first input terminal of the exclusive OR circuit 7a, and the second input terminal thereof is inputted. , The frequency f output from the counter 8 shown in FIG.
The carrier signal of c is input.

The counter 8 will be described below.
The counter 8 counts a signal having a frequency 4fc which is four times as high as the carrier signal output from the local oscillator 9 and divides it into a carrier signal having a frequency fc and a signal having a frequency 2fc which is twice the frequency. The carrier signal of fc is output to the second input terminal of the exclusive OR circuit 7a as described above, and the signal of frequency 2fc is the selector 7b of FIG.
Is output as a trigger signal.

The output of the exclusive OR circuit 7a is applied to the first input terminal of the selector 7b, and the intermediate value output from the ROM 2 of the waveform shaping circuit A is applied to the second input terminal of the selector 7b. Is added. And this selector 7
In b, the output of the exclusive OR circuit 7a and the intermediate value are switched and selected by the select signal of the frequency 2fc output from the counter 8 and output to the D / A converter 10. A signal of frequency 4fc oscillated from the local oscillator 9 is input to the D / A converter 10, and each time the output signal is input, the output of the selector 7b is sample-held and analog-converted.

The output of the D / A converter 10 is input to the BPF 6. The BPF 6 is a folding component of the input data waveform-shaped by the waveform shaping circuit A shown in the frequency 3fc portion of FIG. 5C, and fc-2f _B and fc of FIG. 5C.
Band control is performed in order to remove the aliasing component included in the carrier signal after the analog conversion by the D / A converter 10 shown in the + 2f _B portion. In the PSK modulation device of this embodiment shown in FIG. 1, the modulation circuit C can be constituted by a digital element, and no adjustment is required.

Next, the operation will be described with reference to FIGS. The waveforms in FIGS. 5A to 5E show the waveforms of signals appearing at points a to e in FIG. 1, respectively. First, the data shown in FIG. 5A is input to the shift register 1 of the waveform shaping circuit A, where it is shifted and then R
When input to the OM2 and data is read from the ROM2, the waveform is shaped into the waveform shown in FIG. ROM2
Output signal is a data string after waveform shaping determined by a certain filter characteristic, and the data pattern is determined by the number of stages of the shift register 1. Therefore, as shown in FIG.
The output signal of M2 has a maximum value (MAX) and a minimum value (MI
N) and an intermediate value (DC free component) exist respectively.
The output signal of the ROM 2 is supplied to the gate 7, that is, as shown in FIG.
Is input to the first input terminal of the exclusive OR circuit 7a.

On the other hand, the local oscillator 9 outputs a signal having a frequency 4fc which is four times the frequency fc of the carrier signal, and the signal having the frequency 4fc is output from the counter 8 and D /
It is output to the A converter 10. The counter 8 counts the signal of the frequency 4fc and outputs the frequency-divided signal of the frequency fc and the signal of the frequency 2fc. The frequency-divided signal of the frequency fc is output to the second input terminal of the exclusive OR circuit 7a. Add. As a result, the exclusive OR circuit 7a causes the frequency fc
An exclusive OR of the frequency-divided signal and the output signal of the ROM 2 is calculated and output to the first input terminal of the selector 7b.

On the other hand, the frequency-divided signal of frequency 2fc from the counter 8 is input to the selector 7b as a trigger signal, and in the selector 7b, the frequency-divided signal of frequency 2fc is used.
The output of the exclusive OR circuit 7a and the DC free component output from the ROM 2, that is, the intermediate value shown in FIG. 3 are selected. Therefore, as shown in FIG. 4, the signal output from the selector 7b is a signal in which the maximum value and the minimum value in the output signal of the ROM 2 are inverted for each frequency 2fc that is twice the frequency fc of the carrier signal. That is, in the exclusive OR circuit 7a of the gate 7, by performing X1 / X (-1) on the output signal of the ROM 2, the carrier signal of the frequency fc is PS by the output signal of the waveform shaping circuit A.
K-modulate.

Further, the output of the gate 7, and thus the output of the selector 7b is input to the D / A converter 10 and converted into an analog signal. In order to reduce the influence of the aperture characteristic due to the sample hold of the D / A conversion in the D / A converter 10, the selection state of the selector 7b is switched by the signal of the frequency 4fc output from the local oscillator 9, and the intermediate state from the selector 7b is changed. By outputting a value and inserting it into the output of the exclusive OR circuit 7a for each cycle of the frequency 4fc, a BPSK modulated wave of the carrier frequency fc is generated at the output end of the D / A converter 10. Figure 5
(C) shows the BPSK modulated wave generated at the output end of the D / A converter 10.

The output signal of the D / A converter 10 is B
It is output to PF6. The BPF 6 has a frequency characteristic as shown in FIG. 5 (d). With this frequency characteristic,
The aliasing component of the carrier signal of the frequency fc existing in the waveform after D / A conversion by the D / A converter 10,
Band limitation is performed to remove the aliasing component due to the waveform shaping of the waveform shaping circuit A. As a result, the aliasing component of the carrier signal in the D / A converter 10
The aliasing component of the waveform shaping circuit A is removed, and a BPSK modulated signal as shown in FIG. 5E is obtained at the output end of the BPF 6.

As described above, according to the PSK modulator of this embodiment, the data input is shaped by the waveform shaping circuit A, and the maximum value output from the waveform shaping circuit is doubled by the modulating circuit C as compared with the carrier signal. After passing through for each frequency and inverting the minimum value, analog conversion is performed by the D / A converter 10, and an intermediate value is inserted at every frequency cycle of four times the frequency of the carrier signal to perform BPSK modulation of the frequency of the carrier signal. Since the waves are obtained, it is possible to digitize the modulation means B portion, and therefore, it is possible to make adjustments at the time of production and improve productivity, and at the same time, it is possible to make IC, so that the device is small in size. It becomes possible.

FIG. 6 shows a BPSK according to the second embodiment of the present invention.
FIG. 3 is a block diagram showing a configuration of a modulator, in which a digital filter 11 is inserted in a front stage of a D / A converter 10,
It is a variable transmission rate modulator. 6, the same parts as those in the embodiment of FIG. 1 are designated by the same reference numerals,
Duplicated description of the configuration will be avoided, and parts different from FIG. 1 will be mainly described. In the BPSK modulator of FIG. 6, the waveform shaping circuit A is composed of a register and a ROM as in the embodiment of FIG. 1, and the modulation circuit D is different from the modulation circuit C of FIG. A digital filter 11 is inserted in the preceding stage of the A converter 10, and further,
The modulation section 12 of the modulation circuit D is composed of the gate 7 and the counter 8 shown in FIG.

Therefore, the modulator 12 outputs a signal after waveform shaping, in which an intermediate value is inserted for each cycle of the signal of frequency 4fc oscillated from the local oscillator 9. The output of the modulation circuit 12 is input to the digital filter 11,
The output of the digital filter 11 is the D / A converter 10
Entered in. The digital filter 11 and D / A
A signal of frequency 4fc from the local oscillator 9 is applied to each converter 10. Digital filter 11
Then, every time a signal of frequency 4fc from the local oscillator 9 is input, the aliasing component accompanying the waveform shaping of the waveform shaping circuit A is removed.

Further, in the D / A converter 10, the signal after waveform shaping from which the folding component output from the digital filter 11 is removed is converted into analog, and in the analog filter 13 in the subsequent stage, the analog conversion by the D / A converter 10 is performed. The aliasing component included in the 3 fc portion of the subsequent carrier signal is removed.

In the configuration of FIG. 6, since the filter characteristic of the digital filter 11 can be easily changed by the signal from the outside, the transmission speed of the signal output from the modulator 12 can be changed, and therefore, A PSK modulator of variable transmission rate can be realized without changing the hardware including the analog filter 13.

FIG. 7 shows a QPSK according to the third embodiment of the present invention.
It is a block diagram which shows the structure of a modulator. Q in this figure
In the PSK modulator, the first input data is introduced into the first waveform shaping circuit Aa which is the same as the waveform shaping circuit A shown in FIG. 1 and the waveform is shaped. 9 carrier frequency 4fc carrier signal
SK-modulates the BPSK-modulated signal into the first selector 14a.
I am trying to type in.

Similarly, the second input data is input to the second waveform shaping circuit Ab which is the same as the first waveform shaping circuit Aa to shape the waveform, and the second waveform which is the same as the first BPSK modulation circuit Ea.
The output signal of the waveform shaping circuit Ab is input to the BPSK modulation circuit Eb, and the 90 ° phase-shifted carrier signal of the frequency 4fc from the local oscillator 9 is BPSK modulated by the second BPSK modulation circuit Eb, and the second selector is selected. It outputs to 14b.

The first selector 14a is supplied with a first select signal 15a having a frequency 2fc which is twice as high as the carrier signal having a frequency fc, and the second selector 14b is supplied with the first select signal 15a having the frequency 2fc. To the second select signal 15 with a frequency of 2fc and a phase difference of 180 degrees.
b is input. The first selector 14a selects a signal component in phase with the carrier signal fc shown in FIG. 8A from the output signal of the first BPSK modulation circuit Ea according to the first select signal 15a and outputs it to the adder 16. . Similarly, the second selector 14b outputs the second select signal 15b.
As a result, the output signal of the second BPSK modulation circuit Eb outputs a signal of an orthogonal component to the carrier signal fc and outputs it to the adder 16, as shown in FIG. 8B. That is, the output signal of the first selector 14a and the output signal of the second selector 14b are 90 degrees out of phase with each other, as is apparent from FIGS. 8 (a) and 8 (b).

The adder 16 adds the output signal of the first selector 14a and the output signal of the second selector 14b,
The signal is sent to the D / A converter 10, where it is D / A converted, an analog signal is output, and the aliasing component of the carrier signal is removed by the BPF 6.

In the embodiment of FIG. 7, the in-phase component of the output of the first BPSK modulation circuit Ea and the quadrature component of the output of the second BPSK modulation circuit Eb are added, D / A converted and QP.
Since the SK modulation signal is obtained, twice as much information can be sent in the same band as in the BPSK modulation. Further, if this QPSK modulator is composed of analog elements, a phase shifter and a hybrid are required, but in the embodiment shown in FIG.
All of them can be composed of digital elements, adjustment can be eliminated and productivity can be improved, and the hardware can be simplified. Note that, also in the embodiment of FIG. 7, D
If a digital filter is inserted in the preceding stage of the / A converter 10, the transmission speed can be freely changed.

[0032]

As described above, according to the present invention, the waveform of the input data is shaped by the waveform shaping circuit, and the maximum value of the output signal of the waveform shaping circuit is passed through in every cycle of the frequency twice that of the carrier signal. At the same time, the minimum value of the output signal of the waveform shaping circuit is inverted for each cycle of twice the frequency of the carrier signal, and further, the intermediate value of the output signal of the waveform shaping circuit for each cycle of four times the frequency of the carrier signal. After inserting
By performing A / A conversion and generating a PSK modulated wave of the carrier signal, the entire circuit can be digitized, adjustment can be eliminated during production, and productivity can be improved.
Also, with the all-digitalization, the hardware can be simplified, and the size and the IC can be reduced.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of a BPSK modulator according to a first embodiment of the present invention.

FIG. 2 is a circuit diagram showing a configuration of a gate portion of the modulation circuit shown in FIG.

FIG. 3 is a waveform diagram of an output signal of the waveform shaping circuit shown in FIG.

FIG. 4 is an explanatory diagram illustrating a through operation and an inversion operation of an output signal of the waveform shaping circuit using the gate shown in FIG.

5 (a) to FIG. 5 (e) are respectively a in FIG.
It is a waveform diagram which shows the waveform of the signal which appears at the point-e point.

FIG. 6 is a block diagram showing a configuration of a BPSK modulator according to a second embodiment of the present invention.

FIG. 7 is a block diagram showing a configuration of a QPSK modulator according to a third embodiment of the present invention.

8 is a waveform diagram of an output signal of the selector shown in FIG.

FIG. 9 is a block diagram showing a configuration of a conventional PSK modulator.

[Explanation of symbols]

1 shift register 2 ROM 6 BPF (band pass filter) 7 gates 7a Exclusive OR circuit 7b, 14a, 14b selector 8 counter 9 Local oscillator 10 D / A converter 11 Digital filter 12 Modulator 13 Analog filter A, Aa, Ab waveform shaping circuit C, D modulation circuit Ea, Eb BPSK modulation circuit

Claims (4)

(57) [Claims] 1. A PSK modulator for PSK modulating a carrier signal of a predetermined frequency based on input data, comprising: a waveform shaping circuit for shaping the input data into a maximum value, a minimum value and an intermediate value, and the carrier signal. The maximum value output from the waveform shaping circuit is passed through and the minimum value is inverted for each cycle of a frequency twice the frequency of the carrier signal.
Included in the output signal of the modulation means, which inserts the intermediate value for each cycle of double frequency, and then performs digital / analog conversion for each cycle of the carrier signal to generate a BPSK modulated wave of the carrier signal. A PSK modulation apparatus comprising: a bandpass filter that removes the aliasing component of the carrier signal and the aliasing component associated with the waveform shaping of the waveform shaping circuit. 2. The modulation means is configured to output 4 of the carrier signal.
A local oscillator that generates a signal having a double frequency, a counter that divides the signal output from the local oscillator into the carrier signal and a signal that has a frequency twice the carrier signal, and the frequency divided by the counter. An exclusive OR circuit that takes an exclusive OR of the carrier signal and the output signal of the waveform shaping circuit, and the output of the exclusive OR circuit and the intermediate value at a cycle of twice the frequency of the carrier signal. 2. The PSK modulator according to claim 1, comprising a selector for switching and outputting, and a digital / analog converter for digital / analog converting an output signal of the selector. 3. The PSK modulator according to claim 1, wherein the modulating means further comprises a digital filter inserted before the digital / analog converter to change the transmission rate of the BPSK modulated wave. 4. A PSK modulator for PSK modulating a carrier signal of a predetermined frequency based on first and second input data, wherein the first input data is waveform shaped into a maximum value, a minimum value and an intermediate value. 1 waveform shaping circuit, a second waveform shaping circuit for shaping the second input data into a maximum value, a minimum value and an intermediate value, a local oscillator for generating a signal having a frequency four times as high as the carrier signal, and this local First modulating means for modulating the output signal of the oscillator with the output of the first waveform shaping circuit to generate a BPSK modulated wave, and a signal obtained by phase-shifting the output signal of the local oscillator by 90 degrees, the second waveform shaping circuit. Of the carrier signal and a second modulator that modulates with the output of the first modulator to generate a BPSK modulated wave.
A first selector that selects each of the first select signals having a double frequency and outputs the in-phase component of the carrier signal, and an output signal of the second modulating means has a frequency that is double the frequency of the carrier signal. Second inversion of select signal
A second selector that selects each select signal and outputs the quadrature component of the carrier signal, an adder that adds the output of the first selector and the output of the second selector, and an output signal of the adder A PSK modulator comprising: a digital / analog converter for digital / analog conversion; and a bandpass filter for removing aliasing components of the carrier signal included in the output signal of the digital / analog converter.