JP3105381B2 - QPSK modulator and QPSK demodulator - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a QPSK modulator and a QPSK mainly used for a satellite communication earth station device and the like.
The present invention relates to a K demodulator.

[0002]

FIG. 5 shows, for example, IEICE Technical Report SAT89-15.
FIG. 5 is a schematic diagram showing a configuration of a conventional QPSK modulator for inputting Pch data and Qch data shown in FIG. 5, wherein 1 is a QPSK modulator, 8 is a first local oscillator,
Is a mixer, 5 is a second local oscillator, and 7 is an intermediate frequency filter.

Next, the operation will be described. The output signal of the first local oscillator 8 is output from the QPSK modulator 1 to the QPSK modulator 1.
The PSK data and the Qch data input to the SK modulator 1 are modulated and output as a QPSK signal from the QPSK modulator. This QPSK signal is mixed with the output signal of the second local oscillator 5 in the mixer 4 and then output as a desired intermediate frequency signal through the intermediate frequency filter 7.

[0004] The output signal is a constant frequency of the first local oscillator 8, change of the intermediate frequency is done by changing the oscillation frequency of the second local oscillator 5, a synthesizer in FIG. 5 the second local oscillator 5 And Thus, by setting the output signal of the first local oscillator 8 to a fixed frequency, a modulated wave having stable modulation characteristics can be obtained.

[0005]

Since the conventional QPSK modulator is constructed as described above, it is necessary to change the intermediate frequency to change the oscillation frequency of the second local oscillator 5, and to change the oscillation frequency in minute steps. If to be variable, in order to reduce the phase noise characteristics of the carrier near the second local oscillator 5, as shown in FIG. 6, it is necessary to reduce the frequency division number of the loop constituted by synthesizer multiple loop is there.

FIG. 6 shows an example of a synthesizer having a double loop configuration, in which a main loop 10, a sub-loop 11, and a mixer 1 are provided.
2. Although it has the reference frequency source 13, it has a problem that the design is time-consuming and expensive due to its complicated configuration. Although the change of the intermediate frequency band can be dealt with by changing the oscillation frequency band of the second local oscillator 5, there is a problem that it is necessary to redesign the multi-loop synthesizer, which is troublesome.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and can realize a low phase noise near a carrier with a simple configuration without significantly deteriorating the modulation characteristics of a modulated wave. It is another object of the present invention to provide a QPSK modulator and a QPSK demodulator capable of easily changing the intermediate frequency.

[0008]

Means for Solving the Problems Q according to the invention of claim 1
In the PSK modulation device, the first local oscillator modulates the oscillation frequency.
Within the frequency range that is smaller than the intermediate frequency range
With a frequency synthesizer that is possible in fine steps
The second local oscillator is an oscillating frequency.
The frequency change is equal to the intermediate frequency variable width.
A frequency variable of the first local oscillator within a range of a number variable width.
The same as or less than the width and the fine step
Frequency thinning possible with larger frequency steps
Oscillator composed of a synthesizer
It is .

According to a second aspect of the present invention, there is provided a QPSK modulator in which a band-pass filter is inserted in an output path of the QPSK modulator.

According to a third aspect of the present invention, there is provided a QPSK demodulator, wherein the reference signal regenerator is adapted to change the oscillation frequency of the modulated signal.
Within the frequency variable width smaller than the frequency variable width,
It consists of a frequency synthesizer that is possible in steps
And the local oscillator changes the oscillation frequency when the modulated signal
Within the frequency variable width equal to the frequency variable width
The same as the frequency variable width of the reference signal regenerator, or
Frequency below and above the fine step
It consists of a frequency synthesizer that can be performed in a few steps.
It is characterized by being performed .

According to a fourth aspect of the present invention, there is provided a QPSK modulator , wherein the first local oscillator comprises a frequency synthesizer.
And the frequency system constituting the second local oscillator.
The reference frequency sources of the synthesizers are common to each other . A QPSK demodulator according to claim 5
Is a frequency synthesizer constituting the reference signal regenerator.
And a frequency synthesizer constituting the local oscillator
The reference frequency source of each
is there.

[0012]

The QPSK modulator according to claim 1 is
By configuring the first and second local oscillators with frequency synthesizers capable of changing the oscillation frequency, the frequency synthesizer of the second local oscillator can be realized with a simple single-loop configuration with a small number of divisions. The phase noise characteristic is obtained, and the intermediate frequency can be varied in the variable bandwidth of the second local oscillator in minute steps of the first local oscillator without significantly deteriorating the modulation characteristic. The case was to <br/> Utoshi change the intermediate frequency band, can be relatively easily changed so constitutes a second local oscillator with 1 double loop.

The QPSK modulator according to the second aspect of the invention can remove unnecessary waves outside the band by inserting a band-pass filter in the output path of the QPSK modulator.

According to a third aspect of the present invention, the QPSK demodulator comprises a local oscillator and a reference signal regenerator constituted by a frequency synthesizer capable of changing the oscillation frequency.
As with the SK modulator, the phase noise characteristics can be improved with a simple circuit configuration.

A QPSK according to claim 4 or 5
The modulation device or the QPSK demodulation device uses the same frequency synthesizer or reference signal regenerator constituting the first and second local oscillators and the reference frequency source of the frequency synthesizer constituting the local oscillator. The configuration can be further simplified.

Further, the reference frequency sources of the first and second local oscillators 2 and 5 can be made common. This is specifically
Is shown in the block diagram of FIG. 4 as described below.
Thus, the reference signals of both synthesizers 5 and 9 are shared.
Means

[0017]

【Example】

Embodiment 1 FIG. Hereinafter, a first embodiment of the present invention will be described with reference to the drawings. In FIG. 1 in which the same parts as those in FIG. 5 are denoted by the same reference numerals, and redundant description is omitted, reference numeral 2 denotes a first local oscillator, which uses a synthesizer that can change the oscillation frequency in minute steps. Reference numeral 6 denotes a reference frequency oscillator for the first and second local oscillators 2 and 5.

If the required frequency of the intermediate frequency signal is 14
0 MHz ± 40 MHz / step 25 kHz. You
In other words, the variable width of the intermediate frequency is ± 40 MHz, in fine steps
Is 25 kHz. Here, assuming that the oscillation frequency of the first local oscillator 2 is 200 MHz, this oscillation frequency is 1 MHz.
Even if it is changed by about z, the modulation characteristic does not deteriorate so much.
Variable frequency width ± 500 kHz, step 25 kHz.

Therefore, the oscillation frequency of the second local oscillator 5 is set to 3
If 40MHz ± 40MHz / step 1MHz,
A desired intermediate frequency signal is obtained. In the case of this setting, the frequency division number of the synthesizer of the first local oscillator 2 is 7,980 to
8,020, the frequency division number of the synthesizer of the second local oscillator 5 is 300 to 380. Since the output signal of the first local oscillator 2 has a fixed frequency of 200 MHz in the conventional configuration, the oscillation frequency of the synthesizer of the second local oscillator 5 is 3
40MHz ± 40MHz / step 25kHz,
The frequency division number was 12,000 to 15,200.

That is, if the second local oscillator 5 of the conventional configuration is formed by a single loop, the configuration of the present embodiment improves the phase noise characteristic by reducing the frequency division number. Can be.

In order to obtain the same phase noise characteristic as that of the configuration of the present embodiment, the conventional second local oscillator takes a long time to design, and is constituted by an expensive and complicated multiplex loop to reduce the number of divisions. There is a need.

Next, the frequency of the intermediate frequency signal is set to, for example, 1
Consider a case where an attempt is made to change to 200 MHz ± 250 MHz / step 25 kHz. In the conventional configuration, the second
The oscillation frequency of the local oscillator 5 is 1000 MHz ± 250 M
Hz / step 25 kHz, and the frequency division number is 30,00
0 to 50,000. In this embodiment, the oscillation frequency of the second local oscillator 5 is 1000 MHz ± 250 MHz / step 1 MHz, and the frequency division number is 750 to 1,250. Thus, even if the frequency band of the intermediate frequency signal is changed, the frequency division number of the second local oscillator 5 becomes a relatively small value.
It can be constituted by a single loop and can easily cope with the change of the oscillation frequency.

Embodiment 2 FIG. FIG. 2 shows a second embodiment of the present invention. In the QPSK modulation apparatus shown in FIG.
The bandpass filter 3 is inserted into the output path of the modulator 1 to remove unnecessary waves outside the band.

Embodiment 3 FIG. FIG. 3 illustrates the same principle as FIG.
FIG. 3 shows an embodiment applied to an SK demodulator. In FIG. 3, reference numeral 5 denotes a local oscillator, which is a first local oscillator 5 shown in FIG.
A reference signal regenerator 9 is composed of a minute frequency synthesizer having a small step size like the first local oscillator 2 shown in FIG. Therefore, the phase noise characteristic can be improved as in the case of the QPSK modulator.

Embodiment 4 FIG. FIG. 4 is a block diagram in the case where the reference signal of the reference signal regenerator 9 and the local oscillator 5 are shared, and only one oscillator 6 as a reference frequency source is required, and the configuration can be further simplified. .

[0026]

As described above, according to the first aspect of the present invention,
Since the first local oscillator is constituted by a frequency synthesizer having a small step size, there is an effect that a QPSK modulator having a good phase noise characteristic can be obtained with a simple circuit configuration.

According to the second aspect of the present invention, QPSK
Since the band-pass filter is inserted in the output path of the modulator, there is an effect that unnecessary waves outside the band can be removed.

According to the third aspect of the present invention, since the reference signal regenerator is constituted by a frequency synthesizer having a small step size, QPSK having a good phase noise characteristic with a simple circuit configuration.
There is an effect that a demodulator can be obtained.

According to the fourth aspect of the present invention, the frequency synthesizer constituting the first and second local oscillators of the QPSK modulator or the reference signal regenerator of the QPSK demodulator and the frequency synthesizer constituting the local oscillator are provided. Since the common reference frequency source is used, the circuit configuration can be further simplified.

[Brief description of the drawings]

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

FIG. 2 is a block diagram of a QPSK modulation apparatus according to Embodiment 2 of the present invention.

FIG. 3 is a block diagram of a QPSK demodulator according to Embodiment 3 of the present invention.

FIG. 4 is a block diagram of a QPSK modulator according to a fourth embodiment of the present invention.

FIG. 5 is a block diagram showing a conventional QPSK modulation device.

FIG. 6 is a block diagram of a conventional synthesizer.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 QPSK modulator 2 1st local oscillator 3 Band pass filter 4 Mixer 5 2nd local oscillator 6 Reference frequency oscillator 7 Intermediate signal filter 9 Reference signal regenerator

Claims (5)

(57) [Claims] 1. A QPSK modulator capable of changing a frequency of an intermediate frequency signal by a predetermined intermediate frequency variable width in a predetermined fine step, comprising: a first local oscillator; and an output signal of the first local oscillator. A QPSK modulator that modulates with a baseband signal and outputs the modulated wave signal;
A QPSK modulation apparatus comprising: a second local oscillator; and a mixer that mixes an output signal of the QPSK modulator and an output signal of the second local oscillator to generate the intermediate frequency signal, wherein the first local oscillator includes: An oscillator configured with a frequency synthesizer that is capable of changing the oscillation frequency within the frequency variable range smaller than the intermediate frequency variable range and capable of performing the fine step, wherein the second local oscillator has a change in the oscillation frequency. Within a range of the frequency variable width equal to the intermediate frequency variable width,
A QPSK modulation apparatus, comprising: a frequency synthesizer that is equal to or less than a frequency variable width of the first local oscillator and is configured by a frequency synthesizer capable of performing a frequency step larger than the fine step. 2. The Q according to claim 1, wherein a band-pass filter is inserted in an output path of said QPSK modulator.
PSK modulator. 3. A QPSK demodulator to which a modulated signal whose frequency can be changed by a predetermined modulated signal frequency variable width in a predetermined fine step is input, comprising: a local oscillator; said modulated signal; and said local oscillator. A mixer for generating an intermediate frequency signal by mixing the output signals of the above, a reference signal regenerator for generating a synchronization detection reference signal, and a synchronous detector for synchronously detecting the intermediate frequency signal based on the synchronization detection reference signal In the QPSK demodulator including: wherein the reference signal regenerator has a change in oscillation frequency within a frequency variable range smaller than the modulated signal frequency variable range,
The local oscillator is configured to include a frequency synthesizer that is capable of being performed in the fine step, wherein the change of the oscillation frequency is within a frequency variable width equal to the modulated signal frequency variable width. A QPSK demodulator, comprising: a frequency synthesizer that is equal to or less than the frequency variable width and is capable of performing a frequency step larger than the fine step. 4. A frequency constituting the first local oscillator.
A number synthesizer and the second local oscillator.
The reference frequency sources of the frequency synthesizers
2. The QPSK converter according to claim 1, wherein the QPSK converter is common.
Control device. 5. A frequency constituting the reference signal regenerator.
Frequency synthesizer and the frequency comprising the local oscillator
The reference frequency sources of several synthesizers are
4. The QPSK demodulation device according to claim 3, wherein
Place.