JPH05175879A - Antenna multicoupler - Google Patents

Abstract

PURPOSE:To miniaturize the antenna multicoupler without degrading filter characteristic by composing the antenna multicoupler of a band pass filter composed of a surface acoustic wave filter for a filter for reception. CONSTITUTION:A transmitting signal outputted to an antenna 1 is radiated into air, a transmitting signal turning into the side of a filter 3 for reception is bypassed through a matching circuit (1/4 wavelength transmission line) 7 and a trap circuit 4 to the ground side, and the flow into the filter 3 for reception is blocked. On the other hand, a signal received by the antenna 1 is inputted through a matching circuit 5 to the filter 3 for reception without being bypassed through the matching circuit 7 and the trap circuit 4 to the ground side, and outputted from an output terminal Rx to a receiver after being limited into a prescribed band. In this case, since the filter 3 for reception is composed of the band pass filter composed of the surface acoustic wave filter, the antenna multicoupler can be miniaturized rather than the case of using the band pass filter using a conventional dielectric resonator as the filter for reception.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an antenna duplexer which is interposed between an antenna and a transceiver to limit a transmission signal and a reception signal to predetermined bands.

[0002]

2. Description of the Related Art FIG. 6 is a diagram showing an example of a circuit configuration of an antenna duplexer conventionally interposed between an antenna of a mobile communication device such as a car telephone and a transceiver.

In the antenna duplexer shown in FIG. 1, the transmission filter 10 and the reception filter 11 are band pass filters (hereinafter referred to as BPFs). In addition,
Tx is an input terminal for inputting a transmission signal from the transmitter, Rx
Is an output end for outputting a reception signal to the receiver, and ANT is an input / output end for inputting / outputting the transmission / reception signal to / from the antenna.

FIG. 7 is a diagram showing another example of the circuit configuration of a conventional antenna duplexer, in which the receiving filter 11 is a BP.
The transmission filter 10 includes a band elimination filter (hereinafter referred to as BE) in order to reduce insertion loss.
(Referred to as F).

As the BPF and BEF used in the antenna duplexer in the above high frequency region, one of the terminal shorts in which the inner peripheral surface, outer peripheral surface and one end surface of a dielectric such as a cylindrical ceramic is coated with a conductive material. A dielectric filter using a / 4 wavelength dielectric coaxial resonator is used.

[0006]

Since the conventional antenna duplexer uses the dielectric filter as the transmitting filter 10 and the receiving filter 11, it is difficult to miniaturize the antenna duplexer. That is, when the size of the dielectric coaxial resonator forming the dielectric filter is reduced, the Q (sharpness) is lowered and the insertion loss of the filter is increased. Therefore, when the antenna duplexer is composed of only the dielectric filter. However, there is a certain limit in achieving miniaturization while securing desired filter characteristics.

By the way, the transmission filter 10 of the antenna duplexer is required to have high power resistance, but the reception filter 11 does not need to have high input power resistance equivalent to that of the transmission filter 10. Therefore, it is conceivable to reduce the size of the antenna duplexer by configuring the receiving filter 10 with another filter circuit that does not use a dielectric coaxial resonator and has low withstand power.

However, when the receiving filter 11 is composed of a filter circuit having a low withstand power and is combined with the transmitting filter 10 composed of the dielectric filter, a high power transmitting signal output from the transmitting filter 10 is generated. There is another problem that the reception filter 11 is damaged and the reception filter 11 is damaged.

The present invention has been made in view of the above problems, and an object thereof is to provide an antenna duplexer which can be downsized without deteriorating the characteristics and reliability.

[0010]

In order to solve the above problems, the present invention provides an antenna duplexer which is interposed between an antenna and a transmitter / receiver to limit a transmission signal and a reception signal to a predetermined band respectively. It is provided with a receiving filter composed of a bandpass filter using waves.

It is preferable that matching circuits are provided at the input end and the output end of the receiving filter.

Further, according to the present invention, in the above antenna duplexer, a trap circuit for blocking the transmission signal is provided at an input end of the reception filter.

The trap circuit is formed of a resonance circuit having a series resonance characteristic or a parallel resonance characteristic in the transmission signal band, and when the trap circuit including the resonance circuit having a series resonance characteristic is used, preferably the trap circuit is It is preferable to interpose a matching circuit composed of a quarter wavelength transmission line between the output end of the credit filter and the input end of the trap circuit.

Further, in the trap circuit composed of a resonance circuit having parallel resonance characteristics, a series circuit of a capacitor and a quarter-wave coaxial resonator is interposed between the output end of the transmission filter and the input end of the reception filter. It is better to have a different configuration.

[0015]

According to the first aspect of the present invention, since the receiving filter is constituted by the bandpass filter using surface acoustic waves, the filter circuit constituting the antenna duplexer becomes small.

According to the second aspect of the invention, the transmission loss of the input / output signal at the input / output end of the reception filter is reduced by the matching circuit.

According to the third aspect of the present invention, the transmission signal is prevented from sneaking into the bandpass filter using the surface acoustic wave by the trap circuit, and the reception filter is prevented from being damaged by the sneaking of the transmission signal. To be done.

According to the present invention, the trap circuit resonates in series at the frequency of the transmission signal band, the transmission signal is bypassed by the trap circuit, and the inflow to the reception filter is blocked.

According to the invention of claim 5, 1 /
Impedance matching between the output end of the transmission signal circuit and the trap circuit is achieved by the four-wavelength transmission line, and the transmission signal is efficiently transmitted to the trap circuit. This improves the efficiency of blocking the transmission signal by the trap circuit.

According to the sixth aspect of the present invention, the trap circuit resonates in parallel at the frequency of the transmission signal band, and the input impedance to the reception filter increases, which causes the transmission signal to be transmitted to the reception filter. Inflow is blocked.

According to the invention of claim 7, 1 /
The four-wavelength coaxial resonator has a parallel resonance point in the transmission signal band,
The input impedance to the receiving filter becomes very large. This prevents the transmission signal from flowing into the reception filter.

[0022]

1 is a diagram showing a circuit configuration of an antenna duplexer according to the present invention. In the figure, Tx is an input terminal for inputting a transmission signal, Rx is an output terminal for outputting a reception signal, and ANT is an input / output common terminal for inputting / outputting the transmission signal and the reception signal. The input terminal Tx and the output terminal Rx are respectively connected to a transmitter or a transmission circuit, a receiver or a reception circuit (not shown), and the input / output common terminal ANT.
Is connected to the antenna 1.

Reference numeral 2 is a transmission filter for limiting the band of the transmission signal input from the input terminal Tx to a predetermined band, for example, a dielectric coaxial resonator B shown in FIG.
It is composed of EF.

FIG. 2 shows a quarter-wave dielectric coaxial resonator θi.
And a capacitor Ci in series circuit Si (i = 1 to 3),
For example, it is a BEF having a three-stage configuration in which the transmission lines D1 and D2 having a quarter wavelength, which are strip lines, are vertically connected.

The number of connection stages of the series circuit can be set appropriately depending on the filter characteristics. Further, the transmission lines D1 and D2 may be replaced with a π-type LC equivalent circuit.

Returning to FIG. 1, reference numeral 3 is a reception filter for limiting the band of the reception signal received by the antenna 1 to a predetermined band and removing unnecessary signals, and is a BPF composed of a well-known surface acoustic wave filter. It is composed of.

Reference numeral 4 denotes a trap circuit for removing the transmission signal output from the transmission filter 2, which prevents the transmission signal from sneaking into the BPF 3. The trap circuit 4 is composed of a series circuit of a capacitor Ct and a quarter-wave dielectric coaxial resonator θt, and includes a receiving filter 3
It is provided between the input end a of the and the ground.

The trap circuit 4 is equivalently replaced by the series circuit of the LC parallel circuit of the coil Lo and the capacitor Co and the capacitor Ct shown in FIG. 3, and the series resonance frequency is set to the transmission frequency. ing. At the series resonance point, the impedance of the trap circuit 4 becomes very small, the transmission signal output from the transmission filter 2 is bypassed to the ground side through the trap circuit 4, and the reception filter 3 in the subsequent stage receives it. It doesn't flow.

The dielectric coaxial resonator θt may be replaced by the LC parallel circuit including a capacitor Co and a coil Lo.

The L-type LC circuits 5 and 6 provided at the input and output ends of the BPF 3 are matching circuits of the receiving filter (surface acoustic wave filter) 3. In the reception band, the matching circuit 5 and the reception filter 3 and the ¼ described later.
The matching circuit 6 performs impedance matching with the wavelength transmission line, and the matching circuit 6 receives the reception filter 3 in the reception band.
And impedance matching with a receiver (not shown). These matching circuits 5 and 6 reduce transmission loss between the antenna 1 and the receiving filter 3 and between the receiving filter 3 and the receiver.

Further, 7 is a matching circuit of the transmission filter 2 and the trap circuit 4, and is constituted by a transmission line of 1/4 wavelength composed of, for example, a microstrip line. In the transmission line 7, the impedance at the tip a on the side of the trap circuit 4 is transformed to a low impedance (≈0) in the transmission band, and is matched with the impedance at the time of series resonance of the trap circuit 4. As a result, the transmission line 7 allows the reception filter 3
Most of the transmission signal transmitted to the side is bypassed to the ground side via the trap circuit 4, and the reception filter 3
Transmission to the side is blocked.

In the above structure, the transmission signal input from the input terminal Tx has the unnecessary frequency removed by the transmission filter 2, and a part of the transmission signal wraps around to the reception filter 3 side.
The rest is output to the antenna 1.

The transmission signal output to the antenna 1 is radiated into the air, and the transmission signal sneaking into the receiving filter 3 side passes through the matching circuit (1/4 wavelength transmission line) 7 and the trap circuit 4. And is bypassed to the ground side, and the inflow to the reception filter 3 is blocked.

On the other hand, the reception signal received by the antenna 1 is input to the reception filter 3 through the matching circuit 5 without being bypassed to the ground side by the matching circuit 7 and the trap circuit 4, and a predetermined signal is received. After being limited to the band, the signal is output from the output terminal Rx to the receiver.

As described above, since the receiving filter 3 is composed of the BPF composed of the surface acoustic wave filter, the antenna is more commonly used as the receiving filter 3 than the conventional BPF using the dielectric resonator θ. The size of the container can be reduced.

The transmission filter 2 is a dielectric resonator θ.
Since the reception filter 3 is composed of a surface acoustic wave filter BPF, the size of the antenna duplexer can be reduced without deteriorating the characteristics of both the transmission filter 2 and the reception filter 3. Can be planned.

Since the matching circuits 5 and 6 are provided at the input and output ends of the receiving filter 3 which is a surface acoustic wave filter, the received signal can be transmitted to the receiver with a small transmission loss.

Further, since the trap circuit 4 composed of a resonance circuit having a series resonance characteristic is provided at the input end a of the reception filter 3, the trap circuit 4 prevents the transmission signal from sneaking into the reception filter 3. Therefore, the reception filter 3 is not damaged by the high power transmission signal.

Further, when the trap circuit 4 is provided, 1 is provided between the output end of the transmission filter 2 and the trap circuit 4.
Since the matching circuit 7 formed of a / 4 wavelength transmission line is interposed, the transmission signal is efficiently bypassed to the ground side via the trap circuit 4, and the efficiency of blocking the transmission signal from the reception filter 3 is improved.

FIG. 4 is a diagram showing the circuit configuration of another embodiment of the antenna duplexer according to the present invention. In the above embodiment, the resonance circuit having the series resonance characteristic is used as the trap circuit, but in the present embodiment, the resonance circuit having the parallel resonance characteristic is used as the trap circuit.

In the antenna duplexer shown in the figure, instead of the trap circuit 4 and the matching circuit 7 of FIG. 1, a trap circuit 4'is inserted in series in the signal line.

Like the trap circuit 4, the trap circuit 4'is formed of a series circuit of a capacitor Ct 'and a quarter wavelength dielectric coaxial resonator .theta.t', and the resonance point of the dielectric coaxial resonator .theta.t '. (Parallel resonance frequency) is set in the transmission frequency band. In the transmission frequency band, the impedance of the trap circuit 4'is ∞, and the inflow of the transmission signal to the receiving filter 3 side is blocked.

It should be noted that the dielectric coaxial resonator θt ′ may be replaced by the LC parallel circuit including a capacitor Co and a coil Lo.

FIG. 5 is a schematic diagram showing the pass characteristic of the trap circuit 4 '. The series circuit of the capacitor Ct ′ and the dielectric coaxial resonator θt ′ serves as a trap on the high frequency side as shown by the passage characteristic A in FIG. On the other hand, the capacitor C
When t ′ is replaced with a coil, it becomes a trap on the low frequency side as in the passage characteristic B of FIG.

Therefore, when the transmission band is higher than the reception band, the trap circuit 4'consisting of a series circuit of the capacitor Ct 'and the dielectric coaxial resonator θt' is used, and when the transmission band is lower than the reception band. A trap circuit 4'comprising a series circuit of a coil and a dielectric coaxial resonator .theta.t 'is used for the.

In this embodiment, since the matching circuit 7 composed of a transmission line of 1/4 wavelength is not required, there is an advantage that the structure is simple. Further, since the frequency band to be blocked is determined by the resonance frequency of the dielectric coaxial resonator θt ′, there is an advantage that the trap frequency is stabilized without being affected by variations in the capacitor Ct ′ and temperature changes.

[0047]

As described above, according to the present invention,
Since the receiving filter is composed of a bandpass filter including a surface acoustic wave filter, it is possible to reduce the size of the antenna duplexer without deteriorating the filter characteristics.

Further, since the matching circuit is provided at each of the input end and the output end of the reception filter, the reception signal can be transmitted with a small transmission loss.

Further, since the trap circuit for blocking the transmission signal is provided at the input end of the reception filter, the reception filter is not damaged by the sneak of the transmission signal, and the reliability can be improved.

Further, since the trap circuit is composed of the resonance circuit having the series resonance characteristic or the parallel resonance characteristic in the transmission signal band, it is possible to effectively prevent the transmission signal from flowing into the reception filter.

In the case where the trap circuit is composed of the resonance circuit having the series resonance characteristic, since the matching circuit composed of the quarter wavelength transmission line is interposed between the trap circuit and the output end of the transmission filter, the transmission signal is By bypassing to the ground side through the matching circuit and the trap circuit, the effect of the trap circuit is improved.

[Brief description of drawings]

FIG. 1 is a diagram showing a circuit configuration of an antenna duplexer according to the present invention.

FIG. 2 is a diagram showing an example of a circuit configuration of BEF.

FIG. 3 is a diagram showing an equivalent circuit of a trap circuit.

FIG. 4 is a diagram showing a circuit configuration of another embodiment of the antenna duplexer according to the present invention.

FIG. 5 is a diagram showing a pass characteristic of a trap circuit.

FIG. 6 is a diagram showing a configuration example of a conventional antenna duplexer.

FIG. 7 is a diagram showing another configuration example of a conventional antenna duplexer.

[Explanation of symbols]

 1 Antenna 2 Transmission Filter 3 Reception Filter 4, 4'Trap Circuit 5, 6, 7 Matching Circuit C1 to C3, Ct, Ct ', Co Capacitor D1, D2 1/4 Wavelength Transmission Line θ1 to θ3, θt, θt ′ Dielectric coaxial resonator Tx input terminal Rx output terminal ANT Input / output shared terminal

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Yasuo Yamada 2 26-10 Tenjin Tenjin, Nagaokakyo City, Kyoto Murata Manufacturing Co., Ltd.

Claims (7)

[Claims] 1. An antenna duplexer interposed between an antenna and a transmitter / receiver for limiting a transmission signal and a reception signal to predetermined bands, respectively, comprising a reception filter composed of a bandpass filter using surface acoustic waves. An antenna duplexer characterized by. 2. The antenna duplexer according to claim 1, wherein a matching circuit is provided at each of an input end and an output end of the reception filter. 3. The antenna duplexer according to claim 1, wherein a trap circuit for blocking the transmission signal is provided at an input end of the reception filter. 4. The antenna duplexer according to claim 3, wherein the trap circuit is composed of a resonance circuit having a series resonance characteristic in the transmission signal band. 5. The antenna duplexer according to claim 4, wherein a matching circuit composed of a quarter wavelength transmission line is interposed between the output end of the transmission filter and the input end of the trap circuit. Shared device. 6. The antenna duplexer according to claim 3, wherein the trap circuit is composed of a resonance circuit having a parallel resonance characteristic in the transmission signal band. 7. The antenna duplexer according to claim 6, wherein the trap circuit includes a series circuit of a capacitor and a quarter-wave coaxial resonator between an output end of the transmission filter and an input end of the reception filter. An antenna duplexer characterized by being interposed.