JPH031851B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a simultaneous transmitting/receiving communication device that uses a local oscillator as a channel oscillator.

2. Description of the Related Art Conventionally, a communication device for simultaneous transmission and reception, such as a wireless telephone, has generally been configured as shown in FIG.

That is, the oscillation output of the transmission channel oscillator OSC is modulated by the output of the audio signal circuit AF, and is transmitted from the antenna ANT at the transmission frequency _T via the amplifier AMP and the antenna duplexer AD. shared device
The received signal with frequency _R input to receiver RX via AD is mixed with signal _T generated by local oscillator LO of receiver RX in mixer MIX, and the frequency _R of the received signal is mixed through intermediate frequency filter IF. Extract the low-frequency intermediate frequency _I and use it as a frequency-specific valve DISC.
The audio signal is converted into an audio signal via the .

At this time, in order to facilitate the design of the antenna duplexer AD, it is often configured to satisfy | _T − _R |= _I . In this case, the oscillation frequency of the local oscillator LO is the same _T as that of the channel oscillator OSC, so if a single oscillator can be used for both, it is effective in reducing the cost of the communication device.

However, if both the oscillators OSC and LO are simply made common, the transmitted signals modulated by the modulation signal of the audio signal circuit AF will be directly demodulated by the receiver RX, and this will be obtained as a sidetone. The problem was that I wasn't feeling very well.

The present invention was made in order to solve the above-mentioned problem in a communication device using a simultaneous transmitting and receiving method. Cancel the modulated signal component contained in the demodulated output by matching the phase and level of this with the modulated signal, or if the receiver is of a double or more superheterodyne system, a second or subsequent one. The modulation signal component contained in the output of the first mixer is canceled at the intermediate frequency conversion stage in the receiver by imparting a modulation function using the modulation signal subjected to a required phase shift to the local oscillator of the receiver, or The receiver's local oscillator is configured to cancel the modulated signal component contained in the modulated output of the channel oscillator before inputting it to the receiver's first mixer by means of the modulated signal, which is a phase-inverted modulation signal, and the transmitter's channel oscillator. The purpose of the present invention is to provide a simultaneous transmitting/receiving communication device that can be used in common.

Hereinafter, the present invention will be explained in detail with reference to embodiments shown in the drawings.

FIG. 2 is a block diagram showing an embodiment of a communication device according to the present invention.

In this figure, the output of the transmitting channel oscillator OSC modulated by the output signal _S1 of the audio signal circuit AF is input to the mixer of the receiver RX (not shown), and the output is outputted by an IF filter or the like. A demodulated signal containing a modulated signal component S ₂ delayed by a certain phase angle is obtained.

On the other hand, the output signal _S1 of the audio signal circuit AF is sent to _S3 via the phase shifter PS and the level adjustment circuit VOL.
Convert to a signal. Thereafter, both signals S ₂ and S ₃ are input to a subtracter SUB to cancel the modulated signal component S ₂ in the receiver RX output.

FIG. 3 is a diagram showing the waveforms of the modulated signal components S ₁ , S ₂ and S _3. If the output signal S ₁ of the audio signal circuit AF is a sine wave, S 2 is a waveform of the modulated signal components S 1 , S ₂ and S 3. Since the phase is delayed by an angle within RX, the modulation signal S ₁ is delayed only by the phase shifter PS, the level is adjusted by the level adjustment circuit VOL, and S ₂ and S ₃ are canceled by the subtraction circuit SUB. be able to.

Alternatively, the modulated signal S ₁ may be phase-shifted by +π to become the signal S ₃ , and this and the modulated signal component S ₂ in the receiver RX output may be canceled by the adder ADD.

In addition, the phase shifter PS and level adjustment circuit
VOL connects both or one of them to the receiver RX and the subtractor or adder SUB or ADD.
It may be inserted between.

The communication system according to the present invention exhibits exactly the same function even if it is modified as described below.

FIG. 4 is a block diagram showing a modified embodiment of the communication device according to the present invention.

That is, if the receiver RX is of the double super-heterodyne type, the channel oscillator
The OSC is used as the first local oscillator LO ₁ of the first mixer MIX ₁ constituting the receiver RX, and its modulated output signal _T and received input signal _R are transmitted to the first mixer MIX 1.
After mixing with MIX ₁ , pass through the first intermediate frequency filter.
Extract the signal _I as IF ₁ output and send it to the second mixer
Input to MIX ₂ .

On the other hand, a level adjustment circuit VOL and a phase shifter are used to adjust the modulation signal so that its level and phase are the same modulation degree as the modulation signal component in the output _I of the first intermediate filter _{IF 1} and the opposite phase of the modulation phase of the output I. The output of the second local oscillator LO ₂ is modulated by the PS.

The second local oscillator is then modulated as described above.
The output of LO ₂ and the signal _I are connected to the second mixer.
The signal may be input to MIX ₂ to mix both signals, and the output thereof may be input to the frequency discriminator DISC via an amplifier IF ₂ including a second intermediate frequency filter.

In the case of the above configuration, it would be convenient to use an inexpensive voltage controlled crystal oscillator VCXO as the second local oscillator _LO2 .

Furthermore, if the channel oscillator OSC is of the phase modulation type, it goes without saying that the second local oscillator _LO2 is also of the phase modulation type.

Although the double super-heterodyne system has been described as an embodiment, the communication device of the present invention can also be applied to a receiver equipped with a larger number of intermediate frequency stages, and in that case, the second local oscillator The modulated signal components contained in the output signals from the first intermediate frequency stage onwards may be canceled using the subsequent modulated output signals of the local oscillators.

FIG. 5 is a block diagram showing a modified embodiment of the communication device according to the present invention. Both of the above two embodiments use a signal containing a modulated signal component as an input signal to the first mixer of the receiver. In contrast, in this embodiment, the modulated signal component is removed in advance from the signal input to the first mixer.

That is, the modulated output signal, which is the output of the transmitter OSC, is input to the modulation circuit MOD.

On the other hand, the level of the modulation signal is adjusted by the level adjustment circuit VOL so that the modulation degree of the modulation circuit MOD becomes equal to the modulation degree of the modulated signal output from the channel oscillator OSC, and then the inverting amplifier R.
The phase is inverted via the AMP and the output thereof is input to the modulation circuit MOD.

In the modulation circuit MOD, the modulation signal component contained in the channel oscillator OSC output is canceled by the phase-inverted modulation signal, so if the output carrier wave is input to the first mixer of the receiver RX, good.

At this time, the phase difference between the modulated input signal to the channel oscillator OSC and the modulated output signal to the modulation circuit MOD is extremely small and can be virtually ignored, so a phase shifter is unnecessary, which is advantageous in terms of circuit simplification.

Of course, it is obvious that a phase shifter having an equivalent function may be used in place of the inverting amplifier R.AMP.

Incidentally, the modulation circuit MOD may have a configuration as shown in FIG.

That is, the channel oscillator VOSC output, which has been set to an appropriate frequency by the first frequency divider (1/N) ₁ , is output by the voltage controlled oscillator VCO, the second frequency divider (1/N) ₂ , and the phase comparator COMP. The phase comparator COMP serves as a reference signal for a closed-loop phase synchronization system consisting of
, the level is adjusted by the level adjustment circuit VOL, and the phase is inverted by the inverting amplifier R・AMP.
_N ) The modulated signal component contained in the output of the voltage controlled oscillator VCO is canceled and a carrier wave from which the modulated signal component is removed is obtained as the output of the voltage controlled oscillator VCO.

Here, if the modulator of the channel oscillator OSC is a frequency modulation type and the modulation signal circuit AF is equipped with a pre-emphasis circuit, the modulated signal which is the output of the channel oscillator OSC is phase modulated, so the modulation circuit MOD is frequency modulated. Must be a modulator, while the channel oscillator
If the OSC modulator is a phase modulation type, the modulation signal circuit AF does not have a pre-emphasis circuit, so the modulation circuit MOD should also be a phase modulator, but it goes without saying that it should be a frequency modulator with a pre-emphasis circuit added. .

In the three embodiments described above, only the method of removing sidetones from the receiver output has been described, but there are cases in which a person who uses this type of communication device requires low-level sidetone transmission. There is.

In order to meet such requests, the above-mentioned Figure 2,
The adjustment may be made by changing one or more of the level, phase, and modulation degree of the modulated signal component to be canceled in FIGS. 4 and 5 to disrupt the balance of the cancellation.

Since the present invention is configured and operates as described above, it is possible to save the expensive high-stability oscillator in a simultaneous transmitting/receiving communication device, and it is therefore extremely effective in reducing the cost. .

[Brief explanation of the drawing]

Fig. 1 is a block diagram showing the basic configuration of a conventional simultaneous transmitting/receiving communication device, Fig. 2 is a block diagram showing an embodiment of a communication device according to the present invention, and Fig. 3 shows the phase relationship of the modulation/demodulation signal. The chart diagram, FIGS. 4 and 5 are block diagrams showing modified embodiments of the communication device according to the present invention, and FIG. 6 is a block diagram showing an embodiment of the modulation circuit shown in FIG. 5. OSC...Transmission channel oscillator, RX...Receiver, _S1 ...Modulation signal, _S2 ...Modulation signal component in demodulation signal, PS...Phase shifter, VOL...Level adjustment circuit, SUB or ADD... ...subtractor (adder),
LO ₂ ...Second local oscillator, R・AMP...Inverting amplifier, MOD...Modulation circuit.

Claims (1)

[Scope of Claims] 1. A channel oscillator output of a transmitter modulated by an audio signal or the like and a phase-inverted signal of the modulated signal, which has been adjusted to a required level, are input to a modulation circuit and outputted from the channel oscillator. The local oscillator of the receiver is removed by using the output of the modulation circuit, which cancels the modulated signal component contained therein, as the output of the local oscillator of the receiver. Simultaneous transmitting and receiving communication device shared with power. 2 The modulation circuit inputs the first frequency divider output and the second frequency divider output to a phase comparator, inputs the phase comparator output to a voltage controlled oscillator, and outputs the output from the second frequency divider. A phase lock loop modulation circuit configured to provide feedback to a frequency divider,
The channel oscillator output of the transmitter is input to the first frequency divider, and the phase inverted signal of the modulation signal is input to the voltage controlled oscillator, and the output of the voltage controlled oscillator is used as the local oscillator output of the receiver. A simultaneous transmitting/receiving communication device in which a local oscillator of a receiver and a channel oscillator of a transmitter are used in common as claimed in claim 1.