JPH05152981A - Receiver for composite modulation wave - Google Patents

Abstract

PURPOSE:To reduce deterioration of a speech quality by receiving both of an output signal of a phase detector and a receiving signal strength output, outputting a signal being proportional to its level difference, and outputting roughly independently two signals by one carrier wave. CONSTITUTION:A receiving signal 1 is applied to a limiter amplifier 2, and an RF signal of prescribed amplitude being an output signal of the limiter amplifier 2 is applied to a phase detector 3. As for an output signal 6 of this phase detector 3, a noise caused by amplitude modulation is superposed on a demodulating signal of angle modulation. On the other hand, an RSSI signal 4 being a receiving signal strength output signal outputted from the limiter amplifier 2 passes through a delaying circuit 5 for compensating a delay time by the phase detector 3, and thereafter, is allowed to branch. Subsequently, one of them, and the other are applied to a noise eliminating circuit 8, and an anti-logarithmic amplifier 9, respectively. An output signal 7 of this circuit 5 is almost the same signal as a noise caused by amplitude modulation, and by taking a level difference of the signal 6 and the signal 7 by the circuit 8, a demodulating signal 10a of amplitude modulation is obtained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a composite modulated wave receiver capable of simultaneously transmitting two signals substantially independently from each other by using one carrier mainly in the field of wireless communication.

[0002]

2. Description of the Related Art In order to realize a mobile communication system with high capacity and high quality of service, it is essential to establish a technique for transmitting a control signal during a call at high speed. For this reason,
There is a demand for a technique for transmitting two signals simultaneously and at high speed using one carrier.

A conventional method of transmitting a control signal during a call is to frequency-division-multiplex voice and control signals in a baseband. That is, this is a method of transmitting the control signal outside the lower band of the voice, but this method has the drawback that intermodulation occurs between the control signal and the voice due to the characteristics of the frequency discriminator and the transmission quality deteriorates. was there. Further, since the signal transmission is performed in an extremely narrow band outside the audio lower band, it is theoretically difficult to speed up the control signal. Therefore, there has been proposed a method of transmitting a control signal during a call using a composite modulation in which one carrier is subjected to both angle modulation and amplitude modulation (Japanese Patent Application No. 1-268152).

Here, in the receiver of the composite modulated wave,
A limiter amplifier is generally provided for demodulation of the angle modulation. Since the limiter amplifier has an AM-PM conversion function, noise due to amplitude modulation is superimposed on the demodulation signal of angle modulation. In order to avoid the influence of this noise, in the conventional composite modulation, it is general to shift the bands of the angle modulation modulation signal and the amplitude modulation modulation signal. When the receiver described in Japanese Patent Application No. 1-268152 is used, the phase noise caused by the amplitude modulation is estimated from the demodulation signal of the amplitude modulation, and the phase noise generated in the limiter amplifier is estimated using this. Since it is suppressed, it is not necessary to shift the bands of the two modulated signals.

[0005]

As described above, by using the composite modulation, the speed of the control signal during a call can be increased,
Also, there is a possibility that the deterioration of the call quality due to the transmission of the control signal during the call is reduced. However, when using a conventional composite modulated wave receiver, the bands of the angle-modulated and amplitude-modulated signals are shifted in order to avoid the influence of noise caused by the AM-PM conversion of the limiter amplifier. There was a need. In this case, the advantage of using complex modulation is lost. Further, when the receiver described in Japanese Patent Application No. 1-268152 is used, the above-mentioned problems do not exist,
The receiver has a configuration in which an AGC circuit, an AM detection circuit, a noise removal circuit, and the like are added to the FM receiver, which causes a problem of complication. An example of a receiver described in Japanese Patent Application No. 1-268152 is shown in FIG. Here, 11 is a received signal, 12 is an AGC circuit, 13 is an AM detector, 14 is a delay circuit, 15
Is a local oscillator, 16 is a mixer, 17 and 18 are limiter amplifiers, 19 is a mixer, 20 is an LPF, 21 is a frequency discriminator, 22 is an angle modulation demodulation signal, and 23 is an amplitude modulation demodulation signal.

The present invention provides a receiver of a composite modulated wave capable of realizing speeding up of a control signal during a call and reduction of call quality deterioration due to transmission of the control signal during a call.

[0007]

To achieve this object, a composite modulated wave receiver of the present invention limits the amplitude of a carrier wave of an amplitude-modulated and angle-modulated composite modulated wave signal to a fixed value, and A limiter amplifier that outputs a received signal strength output signal (referred to as an RSSI signal) having a current fluctuation that is substantially proportional to the logarithm of the amplitude fluctuation of a carrier wave, and a constant amplitude RF or IF signal that is the output signal of the limiter amplifier A phase detector that outputs a signal proportional to the instantaneous phase fluctuation, and an output signal of the phase detector and the RSSI signal are received to output a signal proportional to the level difference between the two, thereby reducing the influence of amplitude modulation. It consists of a noise elimination circuit for obtaining a demodulation signal of the angle modulation of the composite modulation signal with almost no reception, and uses the RSSI signal to eliminate the phase noise generated in the limiter amplifier Pressure and is configured to allow the demodulating.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, the present invention will be described with reference to the drawings. FIG. 1 is a block circuit diagram of an embodiment of a receiver for composite modulated waves according to the present invention. The received signal 1 is applied to the limiter amplifier 2. An RF signal having a constant amplitude, which is an output signal of the limiter amplifier 2, is applied to the phase detector 3. The output signal 6 of the phase detector 3 is a demodulation signal of angle modulation with noise due to amplitude modulation superimposed thereon. On the other hand, the RSSI signal 4 output from the limiter amplifier 2 is branched after passing through the delay circuit 5 for compensating the delay time in the phase detector 3, one to the noise removing circuit 8 and the other to the antilog amplifier 9 Is applied to. The output signal of the delay circuit 5 is 7
Is a signal that is substantially the same as the noise caused by the amplitude modulation, and by obtaining the level difference between the signal 6 and the signal 7 in the noise removal circuit 8, the demodulation signal 10a of the angle modulation that is hardly affected by the amplitude modulation is obtained. Be done. Amplitude modulation demodulation signal 10b
Is obtained by passing the signal 7 through the antilog amplifier 9. The delay circuit 5 can be omitted if the delay time in the phase detector 3 is sufficiently small. Antilog amplifier 9
Can be omitted when the modulation signal for amplitude modulation is a digital signal. As the noise removing circuit 8, for example, a subtractor having a simple structure can be used.

The above contents will be described in more detail using mathematical expressions. Received signal 1 is generally expressed by the following equation.

[Equation 1] Where A (t) is the amplitude variation due to fading, φ
₁ (t) is the amplitude variation due to the amplitude modulation, and φ ₂ (t) is the phase variation due to the angle modulation.

As shown in FIG. 2, the delay time in the limiter amplifier increases in proportion to the logarithm of the input level. Therefore,
The output signal S _lim (t) of the limiter amplifier is expressed by the following equation.

[Equation 2] At this time, the phase detection output S _det (t) is expressed by the following equation.

[Equation 3] On the other hand, the RSSI signal is expressed by the following equation.

[Equation 4] By performing the operation of S _det (t) -S _RSSI (t) in the noise elimination circuit, the demodulation signal _SPD (t) of the angle modulation which is not affected by the amplitude modulation is obtained. That is,

[Number 5] the _{S PD (t) = φ 2} (t).

[0011]

As described above, by using the composite modulated wave receiver according to the present invention, it is possible to realize a system which simultaneously and independently transmits two signals by one carrier with a simple and economical structure. Further, when the receiver of the composite modulated wave according to the present invention is applied to the simultaneous transmission of the voice and the control signal during the call, the speed of the control signal during the call and the deterioration of the call quality due to the transmission of the control signal during the call can be reduced. It is feasible. The present invention has such an effect.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of the present invention.

FIG. 2 is a delay time characteristic diagram of the limiter amplifier used in the present invention.

FIG. 3 is a block diagram showing an example of a conventional receiver of a composite modulated wave.

[Explanation of symbols]

 1 Received Signal 2 Limiter Amplifier 3 Phase Detector 4 Received Signal Strength Output Signal (RSSI Signal) 5 Delay Circuit 6 Phase Detector Output Signal 7 Delay Circuit Output Signal 8 Noise Removal Circuit 9 Antilog Amplifier 10a Angle Modulation Demodulation Signal 10b Amplitude modulation demodulation signal 11 Received signal 12 AGC circuit 13 AM detector 14 Delay circuit 15 Local oscillator 16 Mixer 17,18 Limiter amplifier 19 Mixer 20 LPF 21 Frequency discriminator 22 Angle modulation demodulation signal 23 Amplitude modulation demodulation signal

Claims (1)

[Claims] 1. A composite modulation of a received signal strength output signal having a constant amplitude of a carrier of an amplitude-modulated and angle-modulated composite modulation signal and having a current fluctuation substantially proportional to the logarithm of the amplitude fluctuation of the carrier. A limiter amplifier that outputs to obtain a demodulated signal of amplitude modulation of the signal, a phase detector that receives a signal of a constant amplitude that is the output signal of the limiter amplifier, and outputs a signal proportional to the instantaneous phase fluctuation, By receiving both the output signal of the wave detector and the received signal strength output signal and outputting a signal proportional to the level difference between the two signals, the demodulation signal of the angle modulation of the composite modulation signal is hardly affected by the amplitude modulation. Receiver of a complex modulated wave with a noise elimination circuit for obtaining.