JPH11308143A - Communication equipment - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the low noise amplifier of a reception circuit from being saturated. SOLUTION: A transmission circuit 17 and a reception circuit 18 are connected to an antenna 22 through a duplexer 21 and the antenna 22 is simultaneously used for the transmission of a transmission signal from the transmission circuit 18 and the reception of a reception signal to a reception circuit 11. A cancel signal generation part 15 generating a cancel signal whose phase is opposite to the transmission signal from the transmission circuit 17 is installed. The cancel signal from the cancel signal generation part 15 is synthesized with the reception signal to the reception circuit 11 in a power synthesis part 14. The transmission signal from the transmission circuit 18, which leaks to the reception signal to the reception circuit 11 through the duplexer 21, is canceled. Thus, saturation in the low noise amplification part 13 is avoided.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to transmission / transmission of information signals.
The present invention relates to a communication device that performs reception, and more particularly, to a full-duplex wireless communication device that simultaneously performs transmission and reception.

[0002]

2. Description of the Related Art In a full-duplex type wireless communication device that performs transmission and reception simultaneously, an antenna sharing device (duplexer) is often used to share one antenna for transmission / reception.

In general, a duplexer is a three-terminal element. One end is connected to an antenna, and the other two ends are connected to a transmission circuit and a reception circuit, respectively, so that one antenna is shared by both the transmission circuit and the reception circuit. To be able to

Functionally, a duplexer can be understood as two filter elements that couple between an antenna and a receiving circuit, between an antenna and a transmitting circuit, and separate between the transmitting and receiving circuits.

[0005] That is, of the signals arriving from the antenna, a filter element for limiting the signal to a signal within a desired reception band and supplying the signal to a reception circuit, and a transmission signal output from the transmission circuit to a desired transmission band for the antenna. This is an element having one filter element to be supplied.

[0006]

However, the transmission output within the transmission band supplied from the transmission circuit to the duplexer cannot be completely separated, and the reception terminals are not separated at a fixed ratio (isolation ratio). To leak.

In general, in the case of an antenna sharing device at a frequency used for a cellular phone or the like, the isolation ratio is about 40 to 50 dB, although it depends on the required bandwidth, pass loss, and the like. There are many.

The transmission level output from the transmission circuit is about 1 W (+30 dBm) at the maximum transmission level in a cellular telephone terminal or the like. For example, assuming that the transmission power is +30 dBm, assuming that the isolation ratio of the duplexer is 45 dB, the power leaked to the input terminal of the receiving circuit at this time is -15 dBm
It becomes calculation.

On the other hand, in a receiving circuit, generally, -110d
Since it is necessary to receive a weak signal of about Bm,
For the first-stage amplifier connected to the duplexer, the noise figure is the most important, so the noise figure is 1 dB to 1.5.
A low noise amplifier of about dB is used.

Therefore, the upper limit of the allowable signal level of such a low-noise amplifier is not so high. Usually, signal degradation due to the nonlinearity of the transistor is observed at about -30 dBmk to -20 dBm.

However, as described above, the leakage power level of the transmission power circulating through the duplexer is:
Since it was -15 dBm, if the upper limit level of the received signal of the low noise amplifier is set to -20 dBm, the input is calculated to be excessively large by about 5 dB.

[0012] For example, when a mobile terminal is present in the periphery of a cell, there is a possibility that the reception level becomes low and the transmission level becomes high as described above. At this time, the leaked portion of the transmission power causes a problem that the low-noise amplifier of the receiving system is saturated and the desired received signal is distorted.

Also, many code division multiple access (Code Div.
If the transmission signal is a burst signal that is turned on / off intermittently, as in the transmission system found in the ision multiple access (CDMA) system, the effect of the leakage power of the transmission power wrapping around through the duplexer is the effect of the burst signal. Since the envelope fluctuation is detected by the nonlinearity of the low-noise amplifier, it may affect the received signal as cross modulation.

In any case, the wraparound of the transmission signal via such a duplexer causes a very serious problem that the reception sensitivity is deteriorated.

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and has as its object to provide a communication apparatus that reduces deterioration of reception sensitivity when a transmission signal is routed through a duplexer. I do.

[0016]

In order to solve the above-mentioned problems, a communication apparatus according to the present invention has a transmission circuit and a reception circuit connected to an antenna via a duplexer, and transmits a transmission signal from the transmission circuit. In a communication device that simultaneously uses the antenna for transmission and reception of a reception signal to the reception circuit,
A canceling signal generating means for generating a canceling signal having a phase opposite to that of the transmitting signal from the transmitting circuit, and by adding the canceling signal from the canceling signal generating means to the received signal to the receiving circuit, through the duplexer This cancels out the transmission signal from the transmission circuit that leaks into the reception signal to the reception circuit.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a communication device according to an embodiment of the present invention will be described in detail with reference to the drawings.

A communication device according to an embodiment of the present invention comprises:
As shown in FIG. 1, a transmitting circuit 11 for generating a signal to be transmitted from the communication device, and a receiving circuit 1 for generating a cancellation signal.
1, a receiving circuit 17 that processes a signal received by the communication device, and a duplexer (an antenna sharing device that is connected to the transmitting circuit 11 and the receiving circuit 17 and is an antenna sharing device for sharing the antenna 22). duplexer; DU
P) 21 and an antenna 22 for wirelessly transmitting / receiving a signal to / from this communication device.

The receiving circuit 11 includes a power combining section 14 for combining a signal from the duplexer 21 and a canceling signal from the canceling signal generating section 15, and a low noise amplifying section for amplifying the received signal from the power combining section 13 with low noise. 13 and a signal demodulation unit 12 for demodulating a signal from a radio frequency received signal.

The canceling signal generator 15 outputs a canceling signal having a phase opposite to that of the transmission signal at a variable level. In the power combining section 14 of the receiving circuit 11, the canceling signal generating section 1
5 is added to the reception signal supplied to the reception circuit 11 via the duplexer 21. As a result, the transmission signal leaked from the transmission circuit 17 via the duplexer 21 is canceled by the cancellation signal, and the saturation of the low noise amplifier 13 due to the leakage power of the transmission signal can be avoided.

The transmission circuit 17 includes a transmission signal generator 18 for generating a radio frequency transmission signal, and a power amplifier 19 for amplifying the transmission signal and supplying power to the antenna via a duplexer. .

The transmitting circuit 11 and the receiving circuit 17 are connected to an antenna 22 via a duplexer 21 which is an antenna sharing device.

Next, a signal demodulation section 40 provided in the above-described receiving circuit 11 for demodulating a received signal will be described.

As shown in FIG. 2, the signal demodulation unit 12 of the reception circuit 11 includes a first filter 31 which is a band-pass filter for passing a predetermined band of the signal input from the low noise amplification unit 13 and , A first local oscillator 33 that generates a signal of a predetermined frequency, and a first mixer 32 that mixes a signal passed through the filter 31 and a signal transmitted by the first local oscillator 33. ing.

The signal demodulation unit 12 is provided with the first mixer 3
And a variable gain amplifier 35 for amplifying the signal from the first filter with a variable gain.
And a second local oscillator 3 for generating a signal of a predetermined frequency
7 and a second mixer 3 for mixing the signal from the variable gain amplifier 35 and the signal transmitted from the second local oscillator 37.
6.

Then, the signal demodulation unit 12 converts the signal from the second mixer 36 into a third filter 38 that is a low-pass filter that passes a low-frequency band and a signal that has passed through the third filter 38. An A / D converter 29 for converting an analog signal into a digital signal, and an A / D converter 39
Demodulation processing circuit 40 for demodulating the digital signal from
It is composed of

The signal demodulation section 12 receives the received signal amplified with low noise by the low noise amplification section 13 and the received signal is filtered by a first filter 31 which is a band-pass filter. The first local oscillator 3 in the first mixer 32
The signal is mixed with a signal of a predetermined frequency oscillated in 3.

The signal from the first mixer 32 is filtered by a second filter 34 which is a band-pass filter.
Amplified with a variable gain by the variable gain amplifier 35
Is mixed with a signal of a predetermined frequency oscillated by the second local oscillator 37.

The signal mixed in the second mixer 36 is
After being filtered by a third filter 38, which is a low-pass filter, and converted into a digital signal by an A / D converter 39, the signal is demodulated by a demodulation processing circuit 40.

Next, the canceling signal generating section 15 for supplying the canceling signal to the power combining section 14 of the receiving circuit 11 will be described.

As shown in FIG. 3, the cancellation signal generator 15 includes a transmission signal generator 46 for generating a transmission signal, and an A / D converter 45 for converting an analog signal from the transmission signal generator 46 into a digital signal. And a local oscillator 43 for transmitting a signal of a predetermined frequency, and a mixer 44 for mixing the digital signal from the A / D converter 45 and the signal transmitted by the local oscillator 43.

The canceling signal generator 15 is provided with the mixer 4
A filter 42 which is a low-pass filter for passing a low-frequency band through the signal mixed at 4;
Variable amplifier 4 for amplifying the signal from the amplifier with a variable gain
And 1.

The transmission signal generated by the transmission signal generation circuit 46 is converted into a digital signal by a D / A converter 45 and mixed with a signal of a predetermined frequency oscillated by a local oscillator 43 by a mixer 44. Is done.

The signal from the mixer 44 is a filter 42 which is a low-pass filter that passes a low band of this signal.
, Is amplified by a variable gain amplifier 41 at a variable gain, and is output as a cancellation signal.

Next, the transmission signal generator 18 provided in the transmission circuit 17 for generating a transmission signal will be described.

As shown in FIG. 4, a transmission signal generation section 18 of the transmission circuit 17 includes a transmission signal generation circuit 46 for generating a transmission signal, and a conversion of the transmission signal from the transmission signal generation section 46 from an analog signal to a digital signal. A D / A converter 45 for performing
First local oscillator 55 for transmitting a signal of a predetermined frequency
And a first mixer 54 that mixes the digital signal from the D / A converter 45 and the signal transmitted by the first local oscillator 55.

The transmission signal amplifier 18 includes a variable gain amplifier 57 that amplifies the signal mixed by the first mixer 54 with a variable gain, and a second local oscillator that generates a signal of a predetermined frequency. Mixer 53, a second mixer 52 that mixes the signal amplified by variable gain amplifier 57 and the signal transmitted by second local oscillator 53, and a predetermined one of signals from second mixer 52. And a filter 51, which is a band-pass filter that passes the band of FIG.

Here, the canceling signal generator shown in FIG. 3 and the D / A converter 45 and the transmission signal generator 56 of the transmission signal generator shown in FIG. 4 are shown separately for convenience. It is configured as a common circuit.

The transmission signal generated by the transmission signal generation circuit 46 is converted into a digital signal by the D / A converter 45 and oscillated by the first local oscillator 55 by the first mixer 54. The signal is mixed with a signal of a predetermined frequency and further amplified by a variable gain amplifier 57 with a variable gain.

The signal amplified by the variable gain amplifier 57 is mixed by a second mixer with a signal of a predetermined frequency oscillated by a second local oscillator 53, and mixed by the second mixer 52. The signal thus filtered is filtered by a filter 51, which is a band-pass filter that passes a predetermined band of the signal, and then output.

As described above, with respect to a communication device in which the transmission circuit 11 and the reception circuit 17 are connected to the antenna 22 via the duplexer 21, the transmission circuit 17 generates a radio frequency transmission signal. And a power amplifier 19 for amplifying the transmission signal and supplying power to the antenna 22 through the duplexer 21.
A low-noise amplifier 13 for amplifying the received signal with low noise;
A signal demodulation unit that is provided after the low-noise amplification unit and demodulates a signal from a received signal of a radio frequency, a first input terminal connected to the duplexer output, and a second input terminal; The power combiner 14 adds the power supplied to the first and second input terminals and outputs the sum to the low-noise amplifying unit. In addition, the output level is variable in the opposite phase of the transmission signal. Cancellation signal generator 1 for generating a certain signal
5 to supply a canceling signal output from the canceling signal generating unit 15 to a second input terminal of the power combining unit 14, so that the output of the transmitting circuit 17 is output to the receiving circuit via the duplexer 21. By canceling the power leaking to the input of the input 11, the saturation of the low noise amplifier 13 due to the leak power of the transmission signal is avoided.

Next, a communication device according to a second embodiment of the present invention will be described with reference to FIG. Here, a communication device according to the second embodiment will be described.
The following description focuses on differences from the communication device according to the first embodiment.

In the second embodiment, the canceling signal generating section 15 for generating the canceling signal is provided at a stage preceding the power amplifying section 19 of the transmission circuit 17 and converts a part of the input signal to the power amplifying section 19. A directional coupler 63 to be taken out, and a phase inversion circuit 65 for inverting the phase of the signal from the directional coupler 63
And a band-pass filter for passing a signal of a predetermined band out of the signals whose phases have been inverted by the phase inverting circuit 65, and a filter 66 for outputting the signal passed through this filter as a cancellation signal. ing.

In the second embodiment, the receiving circuit 11 has a directional coupler 61 provided before the low-noise amplifying unit 13 and coupling a canceling signal to a signal received from the duplexer 21. doing.

The other parts are the same as those in the first embodiment, and the description is omitted.

In the second embodiment, the communication apparatus uses a directional coupler 63 as a power coupler in a stage preceding the power amplifying section 19 of the transmission circuit 17, and the phase of the power extracted by the phase inversion circuit 65. Are inverted, and unnecessary frequency components are removed by a filter 66, and then supplied to the power combining unit 14 of the receiving circuit 11 as a canceling signal.
In this case, the order of the filter 66 and the phase inverting circuit is arbitrary and may be reversed.

Note that, instead of the phase inverting circuit 65 constituting the canceling signal generating section 15, a variable gain circuit capable of varying the gain can be used.

As described above, in the second embodiment, the directional coupler 63, which is a power coupler for extracting a part of the input in the power amplifier 19 of the transmission circuit 17, is provided. A canceling signal generator for inverting the phase of the transmission signal of the frequency by an inverting amplifier circuit 65 and for canceling an unnecessary frequency component by a band-pass filter 66 as a canceling signal;
1 is provided with a directional coupler 61 for combining a cancellation signal with a reception signal.

Next, a communication device according to a third embodiment of the present invention will be described with reference to FIG. Here, a communication device according to the third embodiment will be described.
The following description focuses on differences from the communication device according to the first and second embodiments.

In the third embodiment, the canceling signal generating section 15 for generating the canceling signal is provided at the subsequent stage of the power amplifying section 19 of the transmitting circuit 17, and the transmitting signal output from the power amplifying section 19 to the duplexer 21 is provided. A directional coupler 63 for extracting a part of the signal, a phase inverting circuit 65 for inverting the phase of the signal from the directional coupler 63, and a predetermined band in the signal whose phase has been inverted by the phase inverting circuit 65 Is a bandpass filter that passes the signal of
66 that outputs a signal that has passed through as a cancellation signal
And

In the second embodiment, the receiving circuit 11 has a directional coupler 61 provided before the low-noise amplifying unit 13 and coupling a canceling signal to a signal received from the duplexer 21. doing.

The other parts are the same as those in the first embodiment, and the description is omitted. Further, in the third embodiment, the directional coupler is a power amplifier 1
9 is the same as the second embodiment described above except that it is provided at the subsequent stage.

In the third embodiment, the communication apparatus uses a directional coupler 63 as a power coupler after the power amplification section 19 of the transmission circuit 17, and the phase of the power extracted by the phase inversion circuit 65. Are inverted, and unnecessary frequency components are removed by a filter 66, and then supplied to the power combining unit 14 of the receiving circuit 11 as a canceling signal.
In this case, the order of the filter 66 and the phase inverting circuit is arbitrary and may be reversed.

Note that, instead of the phase inverting circuit 65 constituting the canceling signal generator 15, a gain variable circuit capable of varying the gain can be used.

In the third embodiment, power is extracted from the output of the power amplifier 19 of the transmission circuit 17 using the directional coupler 63, and a cancellation signal is extracted in the same manner as in the second embodiment. is there.

As compared with the second embodiment, the third embodiment
Since the canceling signal in the embodiment of the present invention is extracted at the subsequent stage of the power amplifier circuit 19, the canceling signal has a stronger correlation with the transmission signal leaking to the receiving circuit 11 via the duplexer 21 and is suitable as the canceling signal. ing.

However, in the third embodiment,
The output signal level is higher than that of the second embodiment,
At the same time, since the noise level is high, it is necessary to more sufficiently remove the noise component in the reception band. Otherwise, it will greatly affect the reception sensitivity.

In each of the second embodiment and the third embodiment, the duplexer is output at a constant level by extracting a signal from the output signal level at a fixed ratio using, for example, a directional coupler. It can be synthesized at a certain ratio with the components leaking via the helium.

Alternatively, by adjusting the level of the component extracted by the directional coupler with a variable gain amplifier, the level may be adjusted to a level at which the components are efficiently canceled.

According to the configuration using such a coupler,
It is not necessary to separately provide a circuit or a digital signal processing system for separately producing a cancellation signal, and it is relatively easy to obtain a cancellation signal that is well correlated with the transmission signal.

As described above, in the third embodiment, the directional coupler 63, which is a power coupler for taking out a part of the output of the power amplifier 19 of the transmission circuit 17, is provided. A phase inverting circuit 65 for inverting the phase of the transmission signal of the frequency, and a cancellation signal generating unit for canceling an unnecessary frequency component by a bandpass filter 66 to cancel the signal;
1 includes a directional coupler 61 for adding a cancellation signal to a received signal.

Next, a communication apparatus according to a fourth embodiment of the present invention will be described with reference to FIG.

In the communication device according to the fourth embodiment, a transmission signal level detecting section 71 for detecting the level of the transmission signal output from the transmission device 18 is provided.

The canceling signal generator 15 generates a canceling signal when the level of the output signal detected by the transmission signal level detector 71 exceeds a predetermined reference value.

That is, in the fourth embodiment, the transmission signal level detection section 71 detects the level of the transmission signal, and only when the level of the transmission signal is detected to be higher than a certain level, The canceling signal generator 15 generates the canceling signal and supplies the signal to the power combiner 14 of the receiving circuit 11.

In the fourth embodiment, if the transmission level is lower than a certain level, the canceling signal generator 15 does not operate, so that power can be saved.

As described above, the fourth embodiment includes the transmission signal level detection section 71 for detecting the level of the transmission signal, and the cancellation signal generation section 15 includes the transmission signal level detection section 71.
A cancel signal is generated when the level of the transmission signal detected at the transmission level is equal to or higher than a predetermined reference value.

As described above, the present invention provides a CDMA
A communication device that avoids the problem that a low-noise amplifier in a receiving circuit is saturated by a transmission signal leaking through a duplexer, which is a problem in a full-duplex communication system used in a cellular system or the like. is there.

The present invention is characterized in that, at the preceding stage of the low-noise amplifier, a cancellation signal of an opposite layer which is correlated with a transmission signal is mixed.

[0070]

As described above, according to the present invention, the wraparound component of a transmission signal passing through a duplexer is added to the wraparound component of the transmission signal passing through a duplexer, thereby canceling the wraparound component of the transmission signal passing through the duplexer. Input components exceeding the signal allowable level of the low noise amplifier can be removed.

Further, according to the present invention, the sensitivity is degraded due to the saturation of the low-noise amplifier. As a result, if the number of terminals accommodated per base station is affected, a large loss occurs in the cellular system. The present invention is one means for solving such a problem on the terminal side.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating a configuration of a first embodiment of a communication device.

FIG. 2 is a block diagram illustrating a configuration of a signal demodulation unit.

FIG. 3 is a block diagram illustrating a configuration of a cancellation signal generation unit.

FIG. 4 is a block diagram illustrating a configuration of a transmission signal generator.

FIG. 5 is a block diagram illustrating a configuration of a communication apparatus according to a second embodiment;

FIG. 6 is a block diagram illustrating a configuration of a third embodiment of the communication device.

FIG. 7 is a block diagram showing a configuration of a fourth embodiment of the communication device.

[Explanation of symbols]

Reference Signs List 11 receiver, 15 cancellation signal generator, 17 transmission circuit, 21 duplexer, 22 antenna

Claims (7)

[Claims] A communication device in which a transmitting circuit and a receiving circuit are connected to an antenna via a duplexer, and the antenna is used simultaneously for transmitting a transmitting signal from the transmitting circuit and receiving a receiving signal to the receiving circuit. A canceling signal generating means for generating a canceling signal having a phase opposite to that of the transmitting signal from the transmitting circuit, and adding the canceling signal from the canceling signal generating means to the received signal to the receiving circuit, thereby enabling the duplexer A communication device for canceling a transmission signal from the transmission circuit leaking to a reception signal to the reception circuit via the transmission circuit. 2. The transmission circuit includes: a transmission signal generation unit that generates a transmission signal of a radio frequency; and amplifies a signal from the transmission signal generation unit to reduce power supplied to the antenna via the duplexer. The communication device according to claim 1, further comprising a power amplifying unit that supplies the power. 3. The canceling signal generating means: coupling means for extracting a part of the input to the power amplifying means; phase inverting means for inverting the phase of the signal obtained by the coupling means; 3. The communication device according to claim 2, further comprising a filter that passes a signal of a predetermined band out of the signals from the means and outputs the signal as a cancellation signal. 4. A transmission signal level detecting means for detecting a level of a transmission signal from a transmission circuit, wherein the canceling signal generation means determines that the level of the transmission signal detected by the transmission signal level detection means is a predetermined level. 2. A cancellation signal is generated when a reference value is exceeded.
The communication device as described. 5. The receiving circuit according to claim 1, wherein the receiving circuit includes a coupling unit that couples a cancellation signal from the cancellation signal generation unit to a reception signal to the low noise amplifier circuit.
The communication device as described. 6. The receiving circuit according to claim 1, further comprising: a low-noise amplifier for amplifying the received signal with low noise; and signal demodulating means for demodulating the signal amplified by the low-noise amplifying means. 2. The communication device according to 1. 7. The communication device according to claim 6, wherein the receiving circuit has a coupling unit that couples the cancellation signal to a signal from the duplexer to the low noise amplification unit.