JP2004194097A - Full duplex radio equipment - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent the S/N of a reception signal from being deteriorated caused by the reflected signal of a transmission signal on an antenna. <P>SOLUTION: A transmission signal P<SB>T</SB>from a variable BPF (BandPass Filter) 4 is supplied to the antenna 2 through a circulator 5 and is transmitted as a radio wave. Part of the transmission signal P<SB>T</SB>is reflected at the antenna 2 due to the impedance mismatching of the antenna 2 and is coupled as the reflected signal P<SB>TR</SB>to a receiver 7 side through the circulator 5. Now, part of the transmission signal P<SB>T</SB>is distributed to a variable attenuation circuit 8 side through a distributor 10. The variable attenuation circuit 8 adjusts the transmission signal P<SB>T</SB>to a level approximately equal to the reflected signal P<SB>TR</SB>. A variable phase circuit 9 adjusts the phase of the transmission signal P<SB>T</SB>to approximately 180° to generate a correction signal P<SB>C</SB>. The correction signal P<SB>C</SB>is supplied to an addition circuit 11 to add the correction signal P<SB>C</SB>to the output signal (the reception signal) of the circulator 5 directed to the receiver side 7. Thus, the reflected signal P<SB>TR</SB>in the output signal is sufficiently canceled by the correction signal P<SB>C</SB>. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a full-duplex radio transmitting and receiving with a common antenna.
[0002]
[Prior art]
The full-duplex radio is provided with a transmitter / receiver, enables transmission / reception using one antenna, and performs bidirectional communication. That is, as shown in FIG. 4, when two full-duplex radios 1a and 1b are viewed, when one full-duplex radio 1a transmits the radio wave of the transmission signal from the antenna 2a, the other full-duplex radio 1a 1b receives this with its antenna 2b, and when the full-duplex radio 1b transmits the radio wave of the transmission signal from the antenna 2b, the full-duplex radio 1a receives this with its antenna 2b. Thereby, bidirectional communication can be performed between these full-duplex wireless devices 1a and 1b.
[0003]
FIG. 5 is a block diagram showing a conventional example of such a full-duplex radio, wherein 1 is a full-duplex radio, 2 is an antenna, 3 is a transmitter, 4 is a variable BPF (bandpass filter), and 5 is A circulator, 6 is a variable BPF, and 7 is a receiver.
[0004]
As shown in FIG. 5, the full-duplex radio 1 (corresponding to the full-duplex radio 1a in FIG. 4) includes a transmitter 3 and a receiver 7, and the transmission from the transmitter 3 is performed by the antenna 2. Signal transmission and reception by the receiver 7 can be performed. The transmitter 3 outputs a transmission signal (unmodulated continuous signal or modulated signal) P _T having a transmission frequency f _T. The transmission signal P _T is processed by a variable BPF4 center frequency f _T, is coupled to the antenna 2 through the circulator 5, it is radiated as radio waves from the antenna 4. Further, other radio wave transmitted from the (equivalent to full-duplex radio 1b in FIG. 4) is received from the antenna 2, the received signal P _R of receiver frequency f _R in the receiver 7 side by the circulator 5 Coupled. As a result, the received signal PR from the circulator 5 is processed by the variable BPF ₆ having the center frequency f _R , supplied to the receiver 7, and subjected to various processes such as demodulation (for example, see Patent Document 1).
[0005]
Here, in the transmitter 1, since the transmission signal _PT is generated by the frequency synthesizing unit (not shown), phase noise is generated near the transmission signal _PT , and this is the transmission signal output from the transmitter 3. Included in _PT . The variable BPF 4 attenuates such phase noise, and its center frequency and passband are adjusted so that such attenuation is sufficiently performed. The variable BPF 6 is for attenuating a noise component in the vicinity of the band of the received signal P _R , and its center frequency and pass band are adjusted so that such attenuation is sufficiently performed.
[0006]
[Patent Document 1]
JP-A-2000-115016
[0007]
[Problems to be solved by the invention]
By the way, in the full-duplex radio 1 shown in FIG. 5, if the impedance matching of the antenna 2 is not sufficient, a part of the transmission signal _PT is reflected by the antenna 2, and a reflected signal _PTR is generated. The reflected signal P _TR is coupled to the receiver 7 by the circulator 5 and goes around the receiver 7. Therefore, when performing the received from the transmission and other radio transmission signal P _T from the transmitter 3 at the same time, the transmission signal P _T from the antenna 2 to the reception signal P _R is supplied to a receiver 7 one The reflection signal P _{TR of the} section is mixed at a constant level.
[0008]
Here, when the reception from other radios relatively close distance, since the level of the received signal P _R is very high compared to the level of the reflected signal P _TR, but not with each other problems, away in the case of reception from a distance of another radio, to say that the level of the reflected signal P _TR is low, because the received signal P _R the level from the other radio is low, the receiver 7, the It is affected by the reflected signal _PTR . In particular, if the level of the reflected signal P _TR is higher than the level of the received signal P _R is an amplifier in the receiver 7 is affected by the reflected signal P _TR, saturated in a state where the received signal P _R is not sufficiently amplified This causes the S / N to deteriorate.
[0009]
At this time, if the transmission frequency f _T and the reception frequency f _R are sufficiently separated from each other, and if the pass bands of the variable BPF 4 on the transmitting side and the variable BPF 6 on the receiving side are detuned so as not to partially overlap, the reflected signal P _TR is removed at a variable BPF6 the receiving side, the passage of the influence of the reflected signal P _TR as described above does not occur, when the detuning is not sufficient, that is, a variable BPF6 receiving and variable BPF4 the sender If the band overlap even partially, particularly in the case of reception from other radio far distance, the influence of the reflected signal P _TR is S / N of the receiver the received signal will be degraded.
[0010]
SUMMARY OF THE INVENTION It is an object of the present invention to provide a full-duplex radio capable of solving such a problem and preventing deterioration of the S / N of a received signal due to a reflected signal of a transmitted signal from an antenna.
[0011]
[Means for Solving the Problems]
To achieve the above object, the present invention provides a transmitter for generating a transmission signal in a first frequency band, a first band-pass filter for filtering a transmission signal, and a second band-pass filter for filtering a reception signal. A filter, a receiver to which a reception signal from the second band-pass filter is supplied, a transmission signal from the first band-pass filter to an antenna, and a reception signal received by the antenna to a second signal. A full-duplex wireless device including a circulator for coupling to a band-pass filter, wherein the distributor divides a transmission signal output from a first band-pass filter, and adjusts a level of the distribution signal from the distributor. Attenuating circuit, a phase circuit that adjusts the phase of the distribution signal from the distributor, and a distribution signal whose level is adjusted by the attenuation circuit and whose phase is adjusted by the phase circuit. As the signal is obtained by providing an adding circuit for supplying adds the received signals to a second band pass filter from the circulator.
[0012]
Then, the attenuation circuit makes the level of the distribution signal substantially equal to the level of a part of the reflection signal of the transmission signal reflected by the antenna, and the phase circuit shifts the phase of the distribution signal by almost 180 °, thus: The reflected signal from the antenna is canceled by the addition circuit by the distribution signal whose level is adjusted by the attenuation circuit and the phase is adjusted by the phase circuit.
[0013]
Further, the attenuator can adjust the amount of attenuation, and the phase circuit can adjust the amount of phase.
[0014]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a block diagram showing an embodiment of a full-duplex radio according to the present invention, wherein 8 is a variable attenuation circuit, 9 is a variable phase circuit, 10 is a distributor, 11 is an addition circuit, and FIG. Corresponding parts are denoted by the same reference numerals, and redundant description will be omitted.
[0015]
In FIG. 1, a transmission signal _PT output from a variable BPF 4 is supplied to a circulator 8 via a distributor 10. In the distributor 10, a part of the transmission signal _PT is converted to a distribution signal _PT '. And distributed to the variable attenuation circuit 8. In the variable attenuating circuit 8, the attenuation is adjusted so that the level of the distribution signal P _T ′ is reflected by the antenna 2 and becomes substantially equal to the level of the reflection signal P _TR output from the circulator 5 to the receiver 7 side. The distribution signal P _T ′ whose level has been adjusted by the variable attenuating circuit 8 is supplied to the variable phase circuit 9 and its phase is adjusted. In the variable phase circuit 9, the amount of phase is set such that the phase of the distribution signal _PT ′ is substantially 180 ° relative to the phase of the reflection signal _PTR output from the circulator 5 to the receiver 7. .
[0016]
In this way, the variable attenuation circuit 8 and the variable phase circuit 9, the distributed signals P _T 'level, are phase adjusted, the correction signal P _C of reversed phase relationships are obtained in almost equal level as the reflected signal P _TR . The correction signal P _C is supplied to the adding circuit 11, it is added to the reflected signal P _TR from the circulator 5.
[0017]
Figure 2 is a diagram showing the level and phase relationship between the transmit signal P _T and the reflected signal P _TR and the correction signal P _C in schematic manner, as illustrated, it transmits the signal P _T and substantially in phase of the reflected signal P _TR to the correction signal P _C level is substantially equal phase are approximately 180 ° out, thereby, the adding circuit 11, so that the reflected signal P _RT is canceled substantially by the correction signal P _C.
[0018]
Therefore, even if reflection of the transmitted signal due to impedance mismatching in the antenna 2, with the reflected signal P _TR synthesis circuit 11, the correction signal P _C, will be almost removed, it is fed to the receiver 7 because so that the reflected signal P _TR is mostly removed from the received signal P _R, S / N of the receiver 7 is significantly improved.
[0019]
FIG. 3 is a frequency spectrum diagram showing a comparison between the received signal P _R supplied to the receiver 7 in the conventional example shown in FIG. 5 and the received signal P _R supplied to the receiver 7 in this embodiment. there, here, a case where the received signal P _R is low. Note that P _TR ′ is an input signal of the variable BPF 6, and signals corresponding to FIG.
[0020]
5, in the conventional example shown in FIG. 5, the pass band of the variable BPF 6 is adjusted so that the reflected signal P _TR from the antenna 2 is not supplied to the receiver 7, and the reflected signal P _TR is sufficiently adjusted by the variable BPF 6. To attenuate. However, if the reception frequency f _R of the transmission frequency f _T and the received signal P _R of the transmission signal P _T is close, to the received signal P _R is supplied to a receiver 7, it requires a certain frequency band For this reason, as shown in the figure, the variable BPF 6 cannot be set to a pass band that sufficiently attenuates the reflection signal P _TR , and the receiver 7 includes a large amount of the reflection signal P _TR. received signal P _R will be supplied it. For this reason, the S / N of the receiver 7 is significantly deteriorated. Further, in order to more effectively attenuate the reflection signal P _TR , a high-performance BPF, that is, an expensive and large-sized BPF must be used as the variable BPF 6.
[0021]
In contrast, in this embodiment, since the reflected signals P _TR by the addition circuit 11 is sufficiently removed by the correction signal P _C, the reflected signal P _ER 'is also very mixed into the received signal P _R is supplied to the variable BPF6 Therefore, the received signal P _R supplied to the receiver 7 is also a mixture of the sufficiently suppressed reflected signal P _TR . As a result, the S / N of the receiver 7 is greatly improved, and the restriction on the setting of the pass band of the variable BPF 6 is eased. Therefore, the variable BPF 6 does not require an expensive and large BPF.
[0022]
The fine adjustment of the amount of attenuation in the variable attenuation circuit 8 and the amount of phase in the variable phase circuit 9 are performed, for example, in an adjustment process of a manufactured full-duplex radio.
[0023]
In the above embodiment, the level of the distribution signal _PT ′ distributed by the distributor 10 is first adjusted by the variable attenuation circuit 8, and then the phase is shifted by approximately 180 ° by the variable phase circuit 9. Conversely, the phase of the distribution signal PT ′ may be shifted by about 180 ° by the variable phase circuit 9 and then the level may be adjusted by the variable attenuation circuit 8.
[0024]
Furthermore, even when the reception frequency f _R of the transmission frequency f _T and the received signal P _R of the transmission signal P _T is consistent, the present invention is applicable.
[0025]
【The invention's effect】
As described above, according to the present invention, since the reflected signal reflected from the antenna and mixed into the receiver can be greatly suppressed, even if the transmission frequency and the reception frequency are close to each other. The reflection signal can be effectively prevented from being mixed into the reception signal, and the S / N of the receiver is greatly improved. In addition, since an inexpensive and small BPF can be used as the variable BPF, the size, weight, and cost of the full-duplex radio can be reduced.
[Brief description of the drawings]
FIG. 1 is a configuration diagram illustrating an embodiment of a full-duplex wireless device according to the present invention.
2 is a diagram schematically illustrating the level and phase relationship between the transmit signal P _T and the reflected signal P _TR and the correction signal P _C of the embodiment shown in FIG.
FIG. 3 is a frequency spectrum diagram showing a comparison between a received signal supplied to the conventional full-duplex receiver and a received signal supplied to the full-duplex receiver shown in FIG. 1;
FIG. 4 is a diagram for explaining communication by a full-duplex wireless device.
FIG. 5 is a configuration diagram illustrating a conventional example of a full-duplex wireless device.
[Explanation of symbols]
1 Full-duplex radio 2 Antenna 3 Transmitter 4 Variable BPF
5 Circulator 6 Variable BPF
7 receiver 8 variable attenuation circuit 9 variable phase circuit 10 distributor 11 adder

Claims (3)

A transmitter for generating a transmission signal of a first frequency band, a first bandpass filter for filtering the transmission signal, a second bandpass filter for filtering a reception signal, and a second bandpass filter. And a receiver to which the received signal is supplied, and coupling the transmitted signal from the first band-pass filter to an antenna, and coupling the received signal received by the antenna to the second band-pass filter. In a full-duplex radio equipped with a circulator for coupling,
A distributor that distributes the transmission signal output from the first band-pass filter;
An attenuation circuit for adjusting a level of a distribution signal from the distributor;
A phase circuit for adjusting the phase of the distribution signal from the distributor;
An adding circuit that adds the distribution signal, the level of which is adjusted by the attenuating circuit and the phase of which is adjusted by the phase circuit, to a reception signal from the circulator as a correction signal and supplies the signal to the second band-pass filter And a full-duplex radio. In claim 1,
The attenuation circuit makes the level of the distribution signal substantially equal to the level of a part of the transmission signal reflected by the antenna, and
The phase circuit shifts the phase of the distribution signal by approximately 180 °,
A full-duplex radio, wherein the adder circuit cancels the reflected signal from the antenna. In claim 2,
A full-duplex radio, wherein the attenuator can adjust the amount of attenuation, and the phase circuit can adjust the amount of phase.

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