JPS6059828A - Ssb communication equipment and its receiver - Google Patents

Abstract

PURPOSE:To improve noise characteristics and to attain the use of a high efficiency transmitter by reproducing a modulation signal from phase information included in an SSB signal to limit the noise of amplitude basis. CONSTITUTION:An amplitude limit circuit 10 of the transmitter passes an output signal of a filter circuit 9 while limiting the amplitude of the signal to a prescribed value. On the other hand, an amplitude limit circuit 23 of a receiver passes an output signal of a reception circuit while limiting the amplitude of the signal to a prescribed value. Moreover, one of multiplier inputs of a product detector circuit 28 is used as an output of a mixing circuit 24 and the other is used as an output of a detector circuit 48. Moreover, a modulation circuit 45 uses a signal branched from an output signal of the circuit 28 as a modulation input signal, a local oscillating signal is used as a carrier to apply amplitude modulation, a filter circuit 47 extracts one side band signal from an output signal of the circuit 45 and the circuit 48 applies envelope detection to an output of the circuit 47.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of the Invention] The present invention relates to an ssB (single sideband) communication device suitable as a wireless communication device and a receiving device thereof.

In particular, the present invention relates to an S'S'B communication device and its receiving device that can limit amplitude and remove noise and distortion.

[Description of prior art]

In the conventional S Sj B communication system using amplitude modulation, the amplitude component is used for signal transmission. In principle, it is not possible to remove amplitude noise generated during the transmission process by passing the signal through the opposite path. Therefore, as in FM communication systems, amplitude noise cannot be excluded, and it is necessary to use an inefficient linear amplifier in the transmission circuit.

The inventors focused on the fact that the modulated signal can be regenerated and demodulated by the receiving device only from the phase information contained in the SSB signal, even if the amplitude information of the SSB signal is suppressed or not transmitted at all. [Object of the Invention] It is an object of the present invention to provide an SSB communication device that allows a receiving device to reproduce a modulated signal from phase information included in the SSB signal even if the amplitude of the SSB signal is greatly limited and transmitted. purpose. An object of the present invention is to provide an SSB communication system with good noise characteristics by limiting amplitude noise. A further object of the present invention is to provide an SSB communication method that can use a highly efficient transmitter.

[Features of the invention]

In the present invention, the detection circuit of the receiving device is constituted by a multiplication detection circuit, a signal obtained by branching the output signal of this detection circuit is used as a new modulation input, amplitude modulation is performed using a separately generated local oscillation signal as a carrier wave, and this signal is Extract the SSB signal from the modulated output,
The SS'B signal is envelope-detected and is provided to the multiplication input of the product detection circuit.

In the device of the present invention, it is desirable that the transmitting device transmits a pilot signal in addition to the modulated signal, and that the receiving device reproduces the carrier wave or performs level control based on this biloft signal.

In the present invention, the transmitting device is a normal SSB transmitting device,
Even if it is applied only to the receiving device, a corresponding effect can be obtained.

[Explanation based on examples]

FIG. 1 is a block diagram of a transmitting device of an apparatus according to an embodiment of the present invention. FIG. 2 is a block diagram of a receiving device according to an embodiment of the present invention.

In FIG. 1, an audio signal source 1 is a signal in the audio frequency band that becomes a modulation input signal, for example, a signal obtained by amplifying the output of a microbon to a necessary level, and has a frequency ω(t') that changes with time. Send a signal. This audio signal passes through a band-elimination filter 2 and is connected to one input of an adder circuit 3. This band-elimination filter 2 is, in this example, 2.2
kHz+: This is a filter that blocks 0.2 kllz. On the other hand, the pilot signal oscillation circuit 4 generates a sine wave signal of frequency ωp, in this example, 2.2kHz±0.1kHz.
It is connected to the other input of the adder circuit 3 via a bandpass filter 5 that passes Hz.

The output of the adder circuit 3 is input to the modulator circuit 7. Modulation circuit 7
The output of a local oscillation circuit 8 that generates a carrier wave frequency of frequency 00 is connected to the other input of the oscillator. The output of the modulation circuit 7 is a signal obtained by amplitude modulating the audio signal sent out by the addition circuit 3 using the carrier wave sent out from the oscillation circuit 8, and only the sideband signal on one side of the signal is filtered out by the bandpass filter 9. It is extracted and becomes an SSB signal. S of the output of the bandpass filter 9
The SB signal is transmitted from the transmitting circuit 12 through an amplitude limiting circuit IO that limits the amplitude to a predetermined value and passes it through, and further through a bandpass filter 11.

In the receiving apparatus shown in FIG. 2, a signal received by a receiving circuit 21 is converted into an intermediate frequency signal, amplified by an intermediate frequency amplifying circuit 22, and input to an amplitude limiting circuit 23. This amplitude limiting circuit 23 is a circuit that limits the amplitude of the received SSB signal to a predetermined amplitude and allows it to pass. Amplitude limiting circuit 2
The output of No. 3 is applied to a mixing circuit 24, where it is mixed with the carrier wave frequency sent out by the voltage controlled oscillator 26, and the carrier wave of the SSB signal is regenerated.

The output of the mixing circuit 24 is inputted via a low-pass filter 27 to a detection circuit 28 that performs amplitude detection.

The output of the detection circuit 28 is an audio frequency signal, the pilot signal frequency is removed by a band-elimination filter 30, amplified by an amplifier circuit 31, and sent to an output terminal 32. Further, a signal at a pilot frequency is extracted from the output of the detection circuit 28 by a bandpass filter 34 and applied to one input of a phase comparison circuit 35 . The other input of this phase comparator circuit 35 is given an output signal from a separately provided pilot frequency signal oscillation circuit 36. The output of the phase comparison circuit 35 is further amplified by an amplifier circuit 38 via a low-pass filter 37 and is applied to the frequency control input of the voltage controlled oscillator 26.

Further, the pilot signal output from the bandpass filter 34 is branched and input to the amplitude detection circuit 40.
The output of is given to one input of the comparator circuit 41. A reference voltage from a reference voltage generation circuit 42 is applied to the other input of the comparison circuit 41, and the output of the comparison circuit 42 is applied to the automatic gain control input of the detection circuit 28.

Here, the feature of the present invention is that the detection circuit 28 is constituted by a product detection circuit (product detection circuit), and furthermore, the input of this product detection circuit has the following amplitude information reproduction. This is where a loop circuit is constructed for. That is, the output of the detection circuit 28 is branched and applied to the modulation signal input of the modulation circuit 45. This modulation circuit 45 is supplied with a signal of frequency ωS from a local oscillation circuit 46, and the output of the detection wave circuit 2 is amplitude-modulated using the output signal of this oscillation circuit 46 as a carrier wave. Any frequency higher than the audio signal frequency can be selected as the frequency ωS. The output signal of the modulation circuit 45 is filtered by a bandpass filter 47 to extract only one sideband, and then sent to the detection circuit 45.
8 and envelope detection is performed. The output of this detection circuit 48 is supplied to one multiplication input of the detection circuit 28.

The operation of the device configured in this way will be explained.

In the transmitting device shown in Fig. 1, 2.2kllz± of the audio signal
Block the 0.2kHz signal and add 2.2kllz here
Insert a pilot signal. According to another study, blocking this band from human speech signals does not improve speech intelligibility AE.
It is expected that N will be about 1 dB or less without deterioration. This audio signal is modulated into an SsB signal, but the amplitude limiting circuit 10 limits the signal amplitude to a predetermined level. Here, the amplitude information can be limited to almost no amplitude information. This amplitude-limited SSB signal is transmitted from the transmitting circuit 12 as a wireless signal.

Expressing this mathematically, the signal Sg at the output of the band-elimination filter 2 +81 points is Sg=a (t) 8cosω(t) , ==”(11
The output of the bandpass filter 5 (the pilot signal at point b1 is 5p=
It can be expressed as cosωpt (2). Therefore, at the output point 1c) of the adder circuit 3, the signal S
is S=Sg +Sp ”' cosωpt +a' (t) ・cosω(1
)...(3) Therefore, if this is amplitude modulated at the carrier frequency ω0 and only one sideband is extracted, the output of the bandpass filter 9 (the SSB signal at point d1 is S cos ωo
t-3sin (dQ t=T7]S'cos,
It can be expressed as (ωot+φ(t))−+41. However, S is the Hilbert transform of S, and tanφ (t)=S/S. Since a signal subjected to a large amplitude limit by the amplitude limit circuit IO does not have amplitude information, the signal sent from the transmitter circuit 12 can be a signal proportional to cos (ωot+φ(t)).

Next, the receiving device will be explained. In FIG. 2, the signal received by the receiving circuit 21 is converted into an intermediate frequency signal, and the intermediate frequency amplifying circuit 22 amplifies the signal to a desired level. The amplitude of the output is limited to a predetermined value by the amplitude limiting circuit 23, and becomes a signal that does not contain amplitude noise and amplitude information. This signal is sent to the demodulating mixing circuit U with a frequency of ω
The carrier wave frequency of 0 is reproduced to become an amplitude-modulated signal, which is passed through the low-pass filter 27, and a detected output of an audio frequency signal is obtained by the detection circuit side. The output of the detection circuit 4 is filtered by a band-elimination filter 30 to remove the pilot frequency, is amplified by an audio frequency amplification circuit 31, and is sent out from an output terminal 32.

Here, the pilot frequency signal is separated by a bandpass filter 34, its output is phase-compared with the output of a self-contained pilot frequency oscillation circuit 3G in a comparator circuit 35, and the comparison error output is sent to a low-pass filter 37 and an amplifier circuit. 38, it becomes the control signal of the voltage controlled oscillator.

That is, the carrier frequency reproduced by the mixing circuit 24 is
The pilot frequency (2.2 kHz in this example) is automatically controlled to a frequency that accurately reproduces it.

On the other hand, the level of the pilot signal is detected by the detection circuit 40 from the output of the bandpass filter 34.1. Automatic gain control is performed on the detection circuit side so that the level becomes a constant value.

To explain the operation of demodulating an audio signal, which is a feature of the present invention, the audio frequency signal obtained at the output of the detection circuit 28 is branched, is newly amplitude-modulated by the conversion circuit @ 45, and is further amplitude-modulated by the amplitude modulation circuit 45. The SSB signal is extracted from the output of. This SSB signal is subjected to envelope detection by the detection circuit 48 and is connected and supplied to the multiplication input of the product detection circuit 28 .

This is because the signal (f) that has passed through the amplitude limiting circuit side is a signal that does not have amplitude information, so the output signal (gl) of the low-pass filter 27 obtained by regenerating the carrier wave does not have amplitude information. This signal contains only phase information.The circuit for reproducing amplitude information from this signal is this loop circuit.

That is, the signal at point (f) that has passed through the amplitude limiting circuit is a signal proportional to the signal cos (ωot+φ(t)) sent out from the transmitter. In a normal state where the voltage controlled oscillator 26 correctly oscillates at frequency ω0, the bandpass filter 2
Since the output of 7 becomes a baseband signal, the prepared signal becomes a signal proportional to CO3φ(1).

Here, cosφ(t)=S/i〒';: 2 -...-(61
Therefore, 5=F7)F cosφ(1) (7). Assuming that the output of the detection circuit 28 (signal at point h1 is S, the output frequency ωS of the local oscillation circuit 46 causes SSB
When the signal is generated, the signal at the output (1) point of the bandpass filter 47 becomes a signal proportional to S cosω5t-3sinωst . The envelope component of this signal is 5 to 7
Since the signal is proportional to F, the product detection circuit 28 has 1g1
Send out the product of the signal at point and the signal at point (1), and the signal at point (h) is S″″F' + g' cosφ(1) ・・・・・・(
7), and it can be seen that the assumption that the signal at the output fh1 point of the detection circuit 28 is S is correct. That is, amplitude information is reproduced from the phase component of the SSB signal whose amplitude information has been limited by the product detection circuit 28.

In the above example, the transmitting device transmits a pilot signal, and the receiving device's carrier wave regeneration is synchronized with this Bi-Japanese-Soviet 1-signal. The present invention can be practiced even if Furthermore, the frequency of the pilot signal does not need to be within the audio frequency band.

In the above example, the amplitude limiting circuit was explained as limiting to a level that does not include amplitude information, but in practice, it is limited to a level that can sufficiently suppress amplitude noise. It is better to leave amplitude information.

The present invention can be implemented only in a receiving device. In other words, the transmitting device can transmit a normal SSB signal without amplitude limitation, and the Australian communication device can receive the signal with amplitude limitation applied to remove amplitude noise.

〔Effect of the invention〕

As described above, according to the present invention, even if the amplitude information of the SSB signal is limited, the receiving device can reproduce the modulated signal. According to the present invention, the signal reproduced by the receiving device is, in principle, a signal without distortion, and the original sound can be reproduced. According to the present invention, even in the SSB communication system, it is possible to apply amplitude limitation to a transmission signal to remove amplitude noise, or to use a high-efficiency amplifier in a transmitter.

[Brief explanation of drawings]

FIG. 1 is a block configuration diagram of a transmitting device of an apparatus according to an embodiment of the present invention. FIG. 2 is a block diagram of the receiving unit of the apparatus according to the embodiment of the present invention. 1...Audio signal source, 2...Band rejection filter, 3...
・Addition circuit, 4...Pilot signal oscillation circuit, 5...
- Bandpass filter, 7... Modulation circuit, 8... Carrier frequency oscillation circuit, 9... Bandpass filter, 10... Amplitude limiting circuit, 11... Bandpass filter, 12... Transmission circuit, 21...Reception circuit, 22...Intermediate frequency amplification circuit,
23... Amplitude limiting circuit, 24... Mixing circuit, 26.
...Voltage controlled oscillator that generates carrier frequency, 27...
・Band filter for selecting the baseband, 28... Product detection circuit for reproducing the audio frequency signal, 30... Band rejection filter for removing the pilot signal, 31... Amplifying circuit for the audio frequency signal, 32...Audio signal output terminal, 3
4... Bandpass filter for selecting the pilot signal, 35.
...Phase comparison circuit, 36...Oscillation circuit that oscillates the pilot signal frequency, 37...Low pass filter, 38...
Amplification circuit for amplifying error signal, 40... Amplitude detection circuit, 41... Level comparison circuit, 42... Reference voltage generation circuit, 45... Amplitude modulation circuit, 46... Generates carrier frequency. Local oscillation circuit, 47... Bandpass filter for extracting the SSB signal, 48... Envelope detection circuit. Patent applicant Naotaka Ide, patent attorney representing Nippon Telegraph and Telephone Public Corporation

Claims (1)

[Claims] (11) The transmitter includes a first modulation circuit that performs amplitude modulation on a carrier wave using a signal in the input audio frequency band as a modulation signal, and a sideband signal on one side from the output signal of this modulation circuit. The receiving device includes a first filtering circuit that extracts a first filtering circuit, and a transmitting circuit that transmits an output signal of the first filtering circuit. In an SSB communication device comprising a mixing circuit that regenerates a carrier wave of a received sideband signal on one side, and a first detection circuit that amplitude-detects the output signal of this mixing circuit, the transmitting device includes the above-mentioned. The receiving device includes a first amplitude limiting circuit that limits the amplitude of the output signal of the first filtering circuit to a predetermined value and passes the signal. and a second amplitude limiting circuit that allows the signal to pass through, and the first detection circuit is constituted by a multiplication detection circuit that uses the output of the mixing circuit as one multiplication input, and the output signal of the multiplication detection circuit therein is a second modulation circuit that performs amplitude modulation using the branched signal as a modulation input signal and a local oscillation signal as a carrier wave; and a second filter that extracts a sideband signal on one side from the output signal of the second modulation circuit. circuit, and a second detection circuit that performs envelope detection of the output of the second filtering circuit, and is configured to apply the output of the second detection circuit to the other multiplication input of the product detection circuit. S characterized by
SB communication device. (2) The audio signal input to the transmitting device includes a pilot signal that serves as a frequency reference, and the mixing circuit of the receiving device controls the frequency of the carrier wave to be reproduced in synchronization with the pilot signal extracted from the received signal. An S'SB communication device according to claim (1). (3) The SSB according to claim (2), wherein the receiving device includes an automatic gain control circuit that automatically controls the reception level so that the reception level of the pilot signal is constant.
Communication device. (4) The SSB according to claim (1), wherein the first amplitude limiting circuit and the second amplitude limiting circuit are circuits that limit the passing level to such an extent that almost all amplitude information is suppressed. Communication device. (5) In an SSB receiving device comprising a mixing circuit that regenerates the carrier wave of the received sideband signal, and a first detection circuit that amplitude-detects the output signal of this mixing circuit, the received The first detection circuit includes an amplitude limiting circuit that limits the amplitude of the sideband signal on one side to a predetermined value and passes the signal, and the first detection circuit includes a multiplication detection circuit that uses the output of the mixing circuit as one multiplication input. The output signal of this multiplication detection circuit is divided into a modulation circuit that uses a branched signal as a modulation input and performs amplitude modulation using a local oscillation signal as a carrier wave, and a sideband signal on one side from the output signal of this modulation circuit. a filtering circuit for extracting the number, and a second detection circuit for envelope detection of the output of the filtering circuit, and configured to apply the output of the second detection circuit to the other multiplication input of the product detection circuit. S characterized by being
S'B receiving device.