JP2002198857A - Radiotelephone - Google Patents

Abstract

PROBLEM TO BE SOLVED: To remove the leakage of a transmission signal into a receiver during transmitting from a radiotelephone for mobile stations to a party station being a mobile station; the radiotelephone taking different frequencies for communication with a base station and for communication with a mobile station. SOLUTION: A filter switching circuit 7 is provided for changing a filter at a front end 3 to a filter 303 for passing signals in a frequency band different from the frequency band of transmission signals during transmitting to a called mobile station, thereby greatly attenuating transmission signals leaked thereinto.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a radio for a mobile station which performs both communication with a base station and communication with a mobile station, and more particularly to the elimination of a transmission signal leaking into a receiver.

[0002]

2. Description of the Related Art Normally, in a radio system in which mobile stations communicate with each other via a base station, as shown in FIG. 4, an uplink frequency f1 from the mobile station to the base station and a downlink f1 from the base station to the mobile station. It is different from the line frequency f2. That is, different frequency bands are used for the uplink and the downlink. (For example, 400 MHz band FDMA (Freque
ncy Division Multiple Acc
ess) In digital radios, the frequency bands of the uplink and downlink are 18 MHz apart. Even in such a wireless system, since the mobile station is outside the base zone (communication area of the base station), for example, the mobile station may be in an area where line connection with the base station cannot be performed.
It is necessary to allow mobile stations to directly communicate with each other. The frequency band used when performing direct communication between mobile stations is the same frequency band as the uplink or the same frequency band as the downlink. Setting the frequency band used for direct communication between mobile stations to the same frequency band as that of the uplink corresponds to FIG. 4 in which the mobile station corresponds to two frequency bands for reception (the reception frequency of the mobile station is changed to the base station. F2 when communication is performed via mobile communication, and f1 when communication is performed between mobile stations, where f1 is equal to f2). On the other hand, making the frequency band used when performing direct communication between mobile stations the same frequency band as the downlink line means that the mobile station corresponds to two frequency bands for transmission (the transmission frequency of the mobile station is F1 when communication is performed via a mobile station, and f2 when communication is performed between mobile stations, where f1 ≠ f2).
It is the same as that.

Generally, it is easier to support two frequency bands in reception than to support two frequency bands in transmission (when two frequency bands are supported, two transmission units are required for transmission. On the other hand, one receiving unit is sufficient for reception.) Therefore, an uplink frequency band is used as a frequency for performing direct communication between mobile stations. That is, in the transmission of the mobile station, the frequency band of the uplink (frequency of the uplink: f
Using only 1), two frequency bands of uplink and downlink in reception (uplink frequency: f1, downlink frequency: f2)
Is used.

A receiver using a superheterodyne system (a receiver having a mixer that mixes an oscillation signal from a local oscillator with a reception signal and converts the frequency of the reception signal to a lower frequency) corresponds to two frequency bands. For this purpose, as shown in FIG. 2, the high-frequency front-end unit 3 is provided with two filters corresponding to the respective frequency bands, and is used by switching according to the communication partner station (mobile station or base station). ing. If one filter tries to cope with two frequency bands, it becomes impossible to sufficiently attenuate out-of-band interference waves. That is, the reception spurious characteristics deteriorate.

FIG. 2 shows a configuration of a conventional mobile station radio. In FIG. 2, a transmission signal from a transmission unit 4 is transmitted to an antenna 1 via an antenna switch 2 and then transmitted. A signal received from the antenna 1 is transmitted to the super-Herodyne receiving unit 5 (including a mixer) via the antenna switch 2, the switch 301, the filter 303 or the filter 304, and the switch 302. The switches 301 and 302 switch the transmission path of the received signal. That is, it switches between transmitting the received signal via the filter 303 and transmitting the received signal via the filter 304. The antenna switch 2 connects the antenna 1 to the transmission unit 4 at the time of transmission, and connects the antenna 1 and the reception unit 5 via the front end unit 3 at the time of reception. This connection switching is performed by the control unit 6 (usually constituted by a microcomputer or the like) in response to a request from the user of the wireless device.
This is performed by a control signal TX output from. The control signal TX switches between reception at HIGH (H) and transmission at LOW (L). (The control signal TX has negative logic.) The switches 301 and 302 of the front end unit 3 include a filter 303 that passes a signal in a frequency band used for communication with the base station and a frequency used for communication between mobile stations. The filter 304 that passes the band signal is switched. The control signal output to control these two switches 301 and 302 from the control unit 6 is DIRECT. SW. Control signal DIRECT SW is switched to the base station communication filter 303 at the time of HIGH (H), and LOW.
At the time of (L), the filter is switched to the inter-mobile station communication filter 304. (Control signal DIRECT SW is negative logic. Hereinafter, the relationship between the communication state of the mobile station and the output signal (control signal) from the control unit 6 will be described with reference to FIG. FIG.
Are the communication state of the mobile station and the output signals from the control unit 6 (the control signal TX and the control signal DIRECT). FIG. 9 is a diagram showing a relationship with the same.

In this state, that is, when a signal from the base station is being received, no transmission signal is output from the transmission section 4 and the filter operated by the front end section 3 is a base station communication filter (filter 303). )It has become.

In this state, that is, when a signal is being transmitted to the base station, a transmission signal is output from the transmission unit 4 to the antenna 1 and a filter operated by the front end unit 3 is a base station communication filter (filter). 303).

In the state, that is, when the other station is also receiving a signal from the other station at the mobile station, no transmission signal is output from the transmitting section 4 and the filter operated by the front end section 3 is a mobile station. Communication filter (filter 304)
It has become.

In the state, that is, when the other station is also transmitting a signal to the other station by the mobile station, a transmission signal is output from the transmitting section 4 to the antenna 1 and the filter operated by the front end section 3 is operated. Denotes a mobile station communication filter (filter 304).

[0010]

In the above-mentioned prior art,
When the mobile station radio is in the state shown in FIG. 5 and the partner station is also transmitting a signal to the partner station at the mobile station, as shown below, the message "Mixer or front end unit The problem that the amplifier is easily broken and "noise of unnecessary frequency is transmitted."

In the state shown in FIG. 5, the filter in the front end section is a filter for mobile station communication (a filter that passes a signal in a frequency band used for communication between mobile stations),
That is, in FIG. 2, a filter that passes a signal in the same frequency band as the transmission frequency band from the transmission unit 4 is selected. As a result, a transmission signal leaks from the transmission unit to the reception unit via the antenna switch 2. The level of this leakage is a level attenuated by about 20 dB with respect to the transmission signal transmitted from the antenna.

Therefore, a very high-level signal (a signal attenuated by about 20 dB with respect to a transmission signal transmitted from an antenna) is input to a mixer which is a component of a superheterodyne mobile station radio. Will be
The following two problems occur. The aim is to eliminate these problems.

A signal input to an amplifier in a mixer or a front end section is easily broken due to a high level.

The mixer outputs not only a normal intermediate frequency signal but also secondary and tertiary distortions of the mixer, and the levels of the secondary and tertiary distortions are increased and radiated to the transmitting unit. The unnecessary frequency noise is generated in the transmitting section 4 and this noise is output from the antenna as transmission spurious (unwanted radio wave transmitted at a frequency outside the band).

[0015]

SUMMARY OF THE INVENTION In order to eliminate the above-mentioned problems, the present invention is controlled by a control unit, and when a partner station is also a mobile station and is transmitting to the partner station, a transmission signal is transmitted. A filter for passing a signal in a frequency band different from the frequency band is provided with a filter switching circuit connected to the receiving unit. As a result, the transmission signal leaked from the transmission unit via the antenna switch is attenuated by the filter that passes a signal in a frequency band different from that of the transmission signal. Due to this attenuation, the level of the transmission signal input to the amplifier in the mixer or the front-end section is greatly attenuated, so that "the amplifier in the mixer or the front-end section is easily broken." Noise is transmitted. "

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A mobile station radio according to an embodiment of the present invention will be described below with reference to FIG. FIG.
FIG. 3 is a block diagram illustrating a configuration of a mobile station radio device of the present embodiment. In FIG. 1, a transmission signal from a transmission unit 4 is transmitted to an antenna 1 via an antenna switch 2 and then transmitted. A reception signal from the antenna 1 is transmitted to the super-Herodyne receiving unit 5 (including a mixer) via the antenna switch 2, the switch 301, the filter 303 or the filter 304, and the switch 302. The switches 301 and 302 switch the transmission path of the received signal. That is, it switches between transmitting the received signal via the filter 303 and transmitting the received signal via the filter 304. The antenna switch 2 connects the antenna 1 and the transmission unit 4 at the time of transmission, and connects the antenna 1 and the reception unit 5 via the front end unit 3 at the time of reception.
This connection switching is performed by a control signal output from the control unit 6 (usually configured by a microcomputer or the like) in response to a request from the user of the wireless device. This control signal is referred to as an antenna switching signal TX. This antenna switching signal TX
Is switched to reception at HIGH (H) and transmission at LOW (L). (The antenna switching signal TX has negative logic.) The switches 301 and 302 of the front end unit 3 are used for a filter 303 that passes a signal in a frequency band used for communication with the base station and a communication between mobile stations. The filter and the filter 304 that pass a signal in the frequency band are switched. Switching between the filter 303 and the filter 304 is performed by a control signal output from the filter switching circuit 7. This control signal is transmitted to the front end switching signal DIRECT. SW. Front end switching signal DIRECT SW
Is switched to the base station communication filter 303 when HIGH (H) and to the mobile station communication filter 3 when LOW (L).
Switch to 04. (Front end switching signal DIR
ECT SW is negative logic. The filter switching circuit 7 receives the front end filter switching signal DIRECT and the antenna switching signal TX output from the control unit 6, and receives the front end switching signal D.
IRECT SW is output.

FIG. 4 shows the configuration of the filter switching control circuit 7.
FIG. 6 shows the relationship between the input signal and the output signal to the filter switching control circuit 7, and FIG. 7 shows the relationship between the communication state of the mobile station radio of this embodiment and the input / output signals to the filter switching control circuit 7. Show.

In this state, that is, when a signal from the base station is being received, no transmission signal is output from the transmitting section 4 and the filter operated by the front end section 3 is a base station communication filter (filter 303). )It has become.

In this state, that is, when a signal is being transmitted to the base station, a transmission signal is output from the transmission unit 4 to the antenna 1, and a filter operated by the front end unit 3 is a base station communication filter (filter). 303).

In the state, that is, when the partner station is also receiving signals from the partner station at the mobile station, no transmission signal is output from the transmitting unit 4 and the filter operated by the front end unit 3 is a mobile station. Communication filter (filter 304)
It has become.

In the state, that is, when the other station is also transmitting a signal to the other station by the mobile station, a transmission signal is output from the transmitting section 4 to the antenna 1 and the filter operated by the front end section 3 is operated. Denotes a base station communication filter (filter 303). From FIG. 4, the frequency of the transmission signal is f1, and the frequency of the signal passing through the base station communication filter (filter 303) is f2. (F1 ≠ f2) Therefore, even if the transmission signal leaks into the front end unit 3, it can be attenuated by the base station communication filter (filter 303). As a result, the "mixer and front end 3
The amplifier inside is easily broken. It is possible to eliminate the problem that "noise of an unnecessary frequency is transmitted."

[0022]

According to the present invention, the mixer and the amplifier inside the front end unit are destroyed due to leakage of a transmission signal during a call between mobile stations, and unnecessary transmission spurious (unnecessary radio wave transmitted at a frequency outside the band). The mobile station wireless device can be provided in which the occurrence of the noise is suppressed.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of a mobile station radio according to an embodiment of the present invention.

FIG. 2 is a block diagram showing a configuration of a mobile station radio as an example of the related art.

FIG. 3 is a circuit diagram showing a configuration of a filter switching circuit.

FIG. 4 is a block diagram showing a communication state of a mobile station radio in the radio system.

FIG. 5 is a diagram showing a relationship between a communication state of a conventional mobile station radio and an output signal from a control station.

FIG. 6 is a diagram illustrating a relationship between an input signal and an output signal to a filter switching circuit.

FIG. 7 is a diagram illustrating a relationship between a communication state of the mobile station radio device according to the present embodiment and input / output signals to a filter switching circuit.

[Explanation of symbols]

1: Antenna 2: Antenna switch 3: Front end unit 4: Transmitter unit 5: Receiver unit 6: Control unit 7: Filter switching circuit 10: Inverting circuit 11: Logic circuit 301: Switch 302: Switch 303: Filter for base station communication 304: Filter for communication between mobile stations

Claims (1)

[Claims] 1. A transmitting unit, a switching unit connected to a preceding stage of the transmitting unit for switching a transmitting / receiving operation, a control unit for controlling the switching unit, and a receiving unit of a predetermined frequency provided at a succeeding stage of the switching unit and passing therethrough. A first filter for outputting a reception signal in the same frequency band as the transmission signal, and a second filter for outputting a reception signal in a frequency band different from the transmission signal. A wireless device having a filter switching unit that is controlled by the control unit and selects a filter that allows the reception signal to pass therethrough, selects a second filter when in a transmission state, and selects the second filter from the transmission unit via the switching unit. A wireless device configured to attenuate the transmission signal leaked into a front end unit.