JPH1127174A - Radio transmitter-receiver - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain high isolation between transmitting and receiving parts. SOLUTION: This radio equipment comprises a receiving part 12 which is switched and connected to a transmitting and receiving antenna 10 through an antenna switch circuit 11 and a transmitting part 13. In such cases, 1st and 2nd band pass filters 121 and 123 of the part 12 vary a center frequency through control voltage, the center frequency of the filters 121 and 123 is shifted outside a use band by adding control voltage to the filters 121 and 123 when the part 13 is operated, and intra-pass band of the filters 121 and 123 is made a steep attenuation characteristic.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a radio device having a transmission / reception function, and more particularly to a transmission / reception radio device requiring high isolation between transmission / reception units.

[0002]

2. Description of the Related Art Conventionally, in a radio having a transmission / reception function, an antenna switching circuit disclosed in Japanese Utility Model Laid-Open No. 5-23639 is known as means for obtaining high isolation between transmission / reception units. Hereinafter, a conventional antenna switching circuit will be described with reference to FIG.

In FIG. 2, an antenna switching circuit includes a diode RC2 connected from a transmission signal terminal TX to an antenna ANT in a forward direction, a diode RC2 connected from a reception signal terminal RX to an antenna ANT in a forward direction, a transmission control terminal T8, and a transmission control terminal T8. An inductance element L1 connected to the signal terminal TX;
An inductance element L2 connected between the reception control terminal R8 and the reception signal terminal RX; an inductance element L3 connected between the reception signal terminal RX and the diode RC2;
3, a capacitor C is connected between the connection point 3 and the ground, and a control voltage supplied from the transmission control terminal T8 to the diode RC1;
By controlling the control voltage supplied from the reception control terminal R8 to the diode RC2, high isolation is obtained between the transmitting and receiving units.

[0004]

However, in the above-described conventional antenna switching circuit, there is a problem that sufficient isolation cannot be obtained with a configuration in which a diode is controlled by a control voltage.

An object of the present invention is to solve the above-mentioned conventional problems, and to provide a radio transceiver capable of obtaining high isolation between the transceivers.

[0006]

In order to solve the above-mentioned problems, a transmission / reception radio apparatus according to the present invention comprises a band-pass filter of a reception section whose center frequency can be varied by a control voltage, and a band-pass filter is provided when the transmission section is operated. By applying a control voltage to the pass filter, the center frequency of the band pass filter is shifted out of the used band.

According to the present invention, high isolation can be obtained between the transmitting and receiving units.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The invention according to claim 1 of the present invention is a transceiver radio having a reception unit and a transmission unit which are switched and connected to a transmission / reception antenna via an antenna switching circuit, wherein the reception unit is A band-pass filter that passes only a reception frequency of a predetermined band from a reception signal received through the antenna switching circuit, wherein the band-pass filter is configured to be able to change a center frequency by a control voltage, and the transmission unit operates. Sometimes, by applying a control voltage to the band-pass filter, the center frequency of the band-pass filter is shifted out of the used band, whereby the pass band of the band-pass filter has a steep attenuation characteristic, and It can be completely isolated from the transmission frequency of the transmission unit and has high isolation between the transmission and reception of the receiving radio. Has the effect of ® emission is obtained.

Hereinafter, an embodiment of the present invention will be described with reference to FIG.
This will be described with reference to FIG. FIG. 1 is a block diagram showing a configuration of a main part of a transceiver transceiver according to an embodiment of the present invention. The transceiver transceiver is used in a mobile wireless system such as a cordless telephone.

In FIG. 1, reference numeral 10 denotes a transmitting / receiving antenna, and 11 denotes an antenna switching circuit for switching and connecting the antenna 10 to a receiving unit 12 or a transmitting unit 13 having a different frequency band. Is supplied to the receiving unit 12 through the antenna switching circuit 11,
A transmission signal from the transmission unit 13 is supplied to the antenna 10 through the antenna switching circuit 11.

The receiving section 12 includes a first band-pass filter (hereinafter, referred to as a first BP) that passes only a reception frequency in a predetermined band from a reception signal received through the antenna switching circuit 11.
F) 121, a high-frequency amplifier circuit 122 for amplifying the received signal passing through the first BPF 121, and a second band-pass filter (hereinafter, referred to as a second BPF) for passing a signal in a predetermined band of the signal amplified by the high-frequency amplifier circuit 122. And a first intermediate frequency conversion unit 124 that mixes the output signal passed through the second BPF 123 and the local oscillation signal from the first local oscillator 124A with a mixer 124B and converts the mixed signal into a first intermediate frequency. Then, the output signal of the first intermediate frequency conversion unit 124 is 455 which is normally adopted.
The signal is output to a signal processing unit (not shown) via a second intermediate frequency conversion unit in the kHz band, a detection circuit (both not shown), and the like.

The first BPF 121 and the second BP
F123 has a flat and low-loss characteristic in a pass band in order to remove image frequency interference, and has a steep attenuation characteristic outside the pass band. In addition to these characteristics, F123 is controlled by a control voltage. It has a trekking characteristic that can change the frequency. Thereby, when the transmitting unit 13 operates, the control frequency is applied to the first BPF 121 and the second BPF 123, so that the center frequencies of the first BPF 121 and the second BPF 123 are shifted out of the pass band.

In the transceiver configured as described above, when the transmitting unit 13 operates, a control voltage is applied to the first BPF 121 and the second BPF 123 so that the center frequencies of the first BPF 121 and the second BPF 123 are out of the pass band. Shift to Thereby, the first BPF
Since the inside of the pass band of the 121 and the second BPF 123 has a steep attenuation characteristic, the receiving section 12 can be completely isolated from the transmission frequency of the transmitting section 13, and accordingly, a high isolation effect between the transmitting and receiving radios can be achieved. Can be obtained.

In addition, even when the circuit units after the first intermediate frequency conversion unit 124 of the reception unit 12 are used during transmission, the first intermediate frequency conversion unit 124 is not affected by the transmission unit 13.
Subsequent operations become possible. Further, by shifting the center frequency of the first BPF 121 to outside the pass band so as to have a sharp attenuation characteristic in the pass band, it is possible to exhibit the effect of preventing the high-frequency amplifier circuit 122 from being broken during transmission.

[0015]

As described above, according to the present invention, a band-pass filter capable of varying a center frequency by a control voltage is provided in a receiving unit of a transmitting / receiving radio, and the center frequency of the band-pass filter is used during operation of the transmitting unit. By shifting outward, there is an effect that high isolation can be obtained between transmission and reception.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of a main part of a transceiver transceiver according to an embodiment of the present invention.

FIG. 2 is a configuration diagram of a conventional antenna switching circuit.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Antenna 11 Antenna switching circuit 12 Receiving part 13 Transmitting part 121 1st BPF 122 High frequency amplifier circuit 123 2nd BPF 124 1st intermediate frequency conversion part 124A 1st local oscillator 124B Mixer

Claims (1)

[Claims] 1. A transmission / reception radio having a reception unit and a transmission unit which are connected to a transmission / reception antenna via an antenna switching circuit, wherein the reception unit transmits a predetermined band from a reception signal received through the antenna switching circuit. A band-pass filter that allows only a reception frequency to pass therethrough, wherein the band-pass filter is configured such that a center frequency can be varied by a control voltage, and the band-pass filter is configured to apply a control voltage to the band-pass filter when the transmission unit operates. A transmission / reception radio device, wherein a center frequency of a pass filter is shifted out of a used band.