JPH03162159A - Digital modulating equipment - Google Patents

Abstract

PURPOSE:To use a C class amplifier as a transmitting amplifier and to easily obtain high power source efficiency by modulating a carrier by a modulating signal for always setting the transition direction of a phase to the prescribed direction. CONSTITUTION:The equipment consists of a complex modulating signal generating circuit 1, a complex carrier generating circuit 2, mixers 3A, 3B, an adder 4, an amplifier 5, and an antenna 6, the complex modulating signal generating circuit 1 is constituted of a 1-bit delayer 11, a comparator 12, a real part waveform generating circuit 13, and an imaginary part waveform generating circuit 14, and the complex carrier generating circuit 2 is constituted of a carrier oscillator 21 and a pi/2 phase shifter 22. According to this constitution, the transition direction of a phase always becomes the prescribed direction, therefore, a modulation frequency characteristic becomes a single side-band. Also, amplitude of a modulated signal always becomes constant, and a linear characteristic is not required for the amplifier. In such a way, the modulating equipment which can use a C class amplifier whose frequency and power efficiency are both high, and also, whose amplitude is constant and whose power efficiency is satisfactory is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a digital modulation system used in wireless communication such as mobile communication (satellite communication), and particularly relates to a modulation device of the BPSK modulation system.

[Conventional technology]

In general, the BPSK modulation method is not only the simplest digital modulation method, but also the most resistant to various types of interference, and is widely used in the field of wireless communications. FIG. 3 shows a modulation device that performs conventional BPSK modulation. In the figure, a data sequence from a data source is input to a mixer 33 via a waveform shaping filter 31, where it is multiplied and modulated by the output carrier of a carrier oscillator 32. The output of this mixer 33 is amplified by an amplifier 34 and radiated into space from an antenna 35. Figure 4 (A) shows a phase transition diagram of BPSK modulation by such a conventional modulation device.
Shown below. Data “O I1 is phase 0, “1” is phase π
In the transition between both phases, the modulation signal ■ changes from point (A, O) to (-A, O) on the real axis.
) or vice versa.

[Problem to be solved by the invention]

Since the BPSK modulated signal by the conventional modulation device described above is moved on the real axis, it always has an upper sideband (USB) and a lower sideband (LSB) shown in FIG. 4(A), The spectrum becomes the double-sided band modulation spectrum shown in Figure 5 (A).Since USB and LSB contain exactly the same information, for the purpose of information transmission, a signal with twice the originally required bandwidth is transmitted. However, at the same time, twice as much transmission power is required, resulting in poor frequency and power efficiency.

Moreover, as is clear from FIG. 4(A), since amplitude modulation is used in principle, the amplifier 34 must have linearity, and the power efficiency cannot be very high. Application to communications was difficult. An object of the present invention is to solve the above-mentioned conventional problems and to provide a modulation device that enables the use of a class C amplifier (nonlinear amplifier) that has high frequency and power efficiency, constant amplitude, and high power efficiency. .

[Means for Solving the Problems] The modulation device of the present invention includes a complex modulation signal generation circuit that generates a modulation signal that always rotates the phase transition of a digital signal from phase 0 to π and from π to O in a constant direction. , comprising a complex carrier generation circuit that generates sine wave and cosine wave carrier signals, and a steel conversion circuit that modulates the output of the complex carrier generation circuit by complex multiplication by the output of the complex modulation signal generation circuit, It is configured to select and output only the real part or imaginary part of the output of the modulation circuit.

In this case, the complex modulation signal generation circuit includes a 1-bit delay device that delays modulation data, a comparator that compares the delayed bits with source data, and a real part waveform generator that generates a real part waveform from the comparison result. , and an imaginary part waveform generator that generates an imaginary part waveform from the comparison result.

[Effect]

In this structure, since the phase transition direction is always constant, the modulation frequency characteristic becomes a single sideband wave, and the occupied frequency bandwidth of the radio wave is halved compared to the conventional one.

Furthermore, the amplitude of the modulated signal is always constant, and the amplifier does not require linear characteristics.

〔Example〕

Next, the present invention will be explained with reference to the drawings.

An example of the modulation device of the present invention is shown in FIG. In the figure,
1 is a complex modulation signal generation circuit that generates a complex modulation signal from modulation data, 2 is a complex carrier generation circuit that generates a complex carrier, and 3A and 3B are modulation circuits that multiply each output of each of the generation circuits 1.2. mixer, 4 is mixer 3A,
3 is an adder for adding the outputs of B, 5 is an amplifier with high power efficiency, for example, a class C amplifier, and 6 is an antenna.

The complex modulation signal generation circuit 1 is composed of a 1-bit delay device 11, a comparator 12, a real part waveform generation circuit 13, and an imaginary part waveform generation circuit l4. A modulated signal whose phase rotates in the positive (negative) direction from O to π during the bit period T of the signal, and which rotates in the same positive (negative) direction during the transition from phase π to 0 (2π). occurs.

Further, the complex carrier generation circuit 2 includes a carrier oscillator 2l
and a π/2 phase shifter 22, and generates sine wave and cosine wave carrier signals.

According to this precept, modulated data consists of each bit data and
The data delayed by 1 bit by the 1-bit delay device l1 is compared by the comparator l2, and then the real part waveform generation circuit 1
3. The real part is output as a complex modulated signal through the imaginary part waveform generating circuit l4. The imaginary parts are output to mixers 3A and 3B, respectively. In addition, in the complex carrier generation circuit 2, a part of the carrier signal is phase-shifted by a π/2 phase shifter 22, and a part of the carrier signal is phase-shifted by a mixer 3.
It is output to A and 3B. Then, the carrier is complex-modulated by complex multiplication of both by the mixers 3A and 3B.

The modulated signals are then added in an adder 4, amplified in an amplifier 5, and sent out from an antenna 6.

Incidentally, the states of the data, real part, and imaginary part of each modulation signal are shown in FIG.

Therefore, according to this BPSK modulation, as shown in FIG.
In this case, phase shift keying is performed at the point (A, O) when the modulated data is 0, and at the point (-A, O) when the data is 1, as in the conventional BPSK. However, when the data changes from O to l, the transition of the modulation phase rotates in the positive direction with the same amplitude, and the point (0
,A), multiplied by the bit period T, and the point (-A,O
). Similarly, when the data changes from 1 to O, the phase also changes in the positive direction with the same amplitude from point (-A, O), passes through point (0, -A), and then changes to point (A, O). Reach O).

As a result, the modulation signal always has a constant amplitude and changes only in the positive direction from phase 6. Therefore, the modulation spectrum becomes a single sideband wave (upper sideband wave) as shown in FIG. 5(B). If the phase were always rotated in the negative direction, the modulation spectrum would be a lower sideband (LSB), contrary to Fig. 5(B).
There is no fundamental difference between them.

As a result, the frequency band of this modulated signal becomes half the conventional band, and both frequency and power efficiency are improved. Furthermore, since the amplitude is constant, a nonlinear amplifier such as a class C amplifier can be used, and power efficiency can also be improved.

〔Effect of the invention〕

As explained above, in the present invention, since the carrier is modulated with a modulation signal whose phase transition direction is always set in a constant direction, the modulation frequency characteristic becomes a single sideband, and the occupied frequency bandwidth of the radio wave is The frequency usage efficiency is doubled. Therefore, the transmission power required to obtain the same C/N on the receiving side is half that of the conventional method. Moreover, since the amplitude of the modulated signal is always constant, C
class amplifiers can be used, and high power supply efficiency can be easily achieved.

Also, since the signal amplitude is constant, the receiver's AGC
A simple hard limiter suffices, which has the effect of simplifying the structure of the receiver.

[Brief explanation of the drawing]

Figure 1 is a block diagram of a modulation circuit using the BPSK modulation method of the present invention, Figure 2 is a signal waveform diagram of modulated data and its real and imaginary parts, Figure 3 is a block diagram of a conventional modulation circuit, and Figure 4 ( A
) and (B) are phase diagrams of the modulation signals of the conventional and the present invention, respectively, and FIGS. 5(A) and (B) are diagrams showing the modulation frequency bands of the conventional and the present invention, respectively. ■...Complex modulation signal generation circuit, 2...Complex carrier generation circuit, 3A, 3B...Short mixer, 4...Adder,
5... Amplifier, 6... Antenna, 1l... 1-bit delay device, 12... Comparator, 13... Real part waveform generation circuit, l4... Imaginary part waveform generation circuit, 21. ...Carrier oscillator, 22.1.π/2 phase shifter, 31..Waveform shaping filter, 32..Carrier oscillator, 33..ξ
Kisa, 34...Amplifier, 35...Antenna. 〉 Fig. 4 (A) CB) Δ Fig. 5 U f

Claims (1)

[Claims] 1. A complex modulation signal that generates a modulation signal that always rotates phase transitions from 0 to π and from π to 0 in a constant direction in a modulation device that shift-keys a digital signal to phase 0 or π. comprising a generation circuit, a complex carrier generation circuit that generates sine wave and cosine wave carrier signals, and a modulation circuit that modulates the output of the complex carrier generation circuit by complex multiplication with the output of the complex modulation signal generation circuit, A digital modulation device characterized in that it is configured to select and output only the real part or the imaginary part of the output of the modulation circuit. 2. The complex modulation signal generation circuit delays the modulation data.
A bit delayer, a comparator that compares the delayed bits with source data, a real part waveform generator that generates a real part waveform from the comparison result, and an imaginary part waveform generator that generates an imaginary part waveform from the comparison result. A digital modulation device according to claim 1, comprising: