JP2003008468A - Digital wireless unit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To solve problems of the conventional digital wireless unit that has increased number of components and required complicated level control by a control section in providing an attenuator to a pre-stage of an amplifier section in order to prevent a signal from being saturated in the amplifier section for amplifying the signal level when received signal power has a high level. SOLUTION: A switching path of an antenna switch 1 is usually connected to a receiver side at reception, but when a high level input is received, the switch 1 is switched to a transmitter side and a switch 13 switches a path of giving an output signal from a terminal (f) of a directional coupler 10 to a reception input section. Through the configuration above, even when the digital wireless unit receives a high level signal, since the attenuated power is given to the receiver side, the receiver side receives a signal with a lower level than that at the antenna terminal and can avoid saturation of the amplifier section to eliminate the need for an attenuator.

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a digital radio, and more particularly to a linear demodulation of a digital radio. 2. Description of the Related Art FIG. 2 shows an example of the configuration of a conventional digital radio, which will be described. In the figure, the transmitting side is a transmitting unit 12,
It comprises a transmitting PA 11 and a directional coupler 10, and the receiving side includes a bandpass filter 2, an attenuator 1
4, an amplifier 3, a local signal generator 4, a frequency conversion mixer 5, a reception IF unit 8, an RSSI 6, a control unit 7, and a demodulation processing unit 9. Switching between transmission and reception is performed by the antenna switch 1. At the time of transmission, the terminals a and c of the antenna switch
The transmission signal output from the transmission unit 12 is power-amplified in the transmission PA unit 11, input to the e terminal of the directional coupler 10, output from the d terminal, and passed through the antenna switch 1. Sent. In addition, the directional coupler 1
The signal input to the 0 e terminal and output from the g terminal is used for power detection and the like. At the time of reception, the terminals a and b of the antenna switch 1 are connected, and a reception signal is input to the receiving unit via the antenna switch 1. The input signal is
The signal passes through the bandpass filter 2 that limits the band, passes through the attenuator 14 that varies the amount of attenuation according to the input level, and is input to the amplifier 3 and amplified. The band-limited amplified reception signal is mixed with the signal generated by the local signal generator 4 by the frequency conversion mixer 5 and frequency-converted. The reception signal frequency-converted to the intermediate frequency is the reception signal
After band limitation and signal level amplification are performed in the F unit 8, the signal is input to the demodulation processing unit 9 and demodulated. Also, receive IF
The unit detects the received power by the RSSI 6, inputs the detected power to the control unit 7, and controls each of the receiving units. [0005] Here, the attenuator 14 is placed before the amplifier for the purpose of attenuating the signal level, because the signal may be saturated by the amplifier 3 when the received power is at a high level. The control of the attenuation of the attenuator is performed by the control unit 7 based on the power detected by the RSSI 6. In the above-described conventional digital radio, when the received signal power is at a high level, the signal level is attenuated by the attenuator 14 in order to prevent the amplification section 3 from being saturated. Therefore, it is necessary to provide the attenuator 14 before the amplifying unit 3 and there is a problem that a complicated level control for the attenuator is required from the control unit. An object of the present invention is to provide a digital wireless device capable of eliminating both the attenuator 14 and reducing both circuit components and software control processing (level control). According to the present invention, in order to achieve the above object, when the received signal power is at a high level, the path of the antenna switch 1 is changed to the transmitting side, and the directional coupling is performed. The signal combined by the device 10 is configured to be input to a receiving unit. As a result, the signal attenuated by the directional coupler 10 is input to the receiving side, and saturation in the amplifier 3 can be avoided. FIG. 1 shows an embodiment of the present invention.
And will be described. As shown in FIG. 1, the conventionally required attenuator is deleted, and the switching of the antenna switch 1 and the changeover switch 13 can be controlled according to the RSSI value. In the figure, the transmitting side is a transmitting unit 12,
The receiving side includes a bandpass filter 2, an amplifier 3, a local signal generator 4, a frequency conversion mixer 5, a receiving IF unit 8,
It comprises an SSI 6, a control unit 7, and a demodulation processing unit 9, and switching between transmission and reception is performed by the antenna switch 1. At the time of transmission, the terminals a and c of the antenna switch
The terminal and the h terminal and the j terminal of the changeover switch 13 are connected, and the transmission signal output from the transmission unit 12 is the transmission P
The power is amplified by the A unit 11, input to the e terminal of the directional coupler 10, output from the d terminal, and transmitted through the antenna switch 1. The signal input to the e terminal of the directional coupler 10 and output from the g terminal are used for power detection and the like. At the time of reception, normally, the terminals a and b of the antenna switch 1 and the terminals h and j of the changeover switch 13 are connected to each other. Is done. The input signal passes through a band-pass filter 2 that performs band limitation, and is input to an amplifier 3 and amplified. The band-limited amplified reception signal is mixed with the signal generated by the local signal generator 4 by the frequency conversion mixer 5 and frequency-converted. The reception signal frequency-converted to the intermediate frequency is subjected to band limitation and signal level amplification by the reception IF unit 8, and then is input to the demodulation processing unit 9 and demodulated. In the reception IF section,
The received power is detected by the RSSI 6, the detected power is input to the control unit 7, and each control of the receiving unit is performed. If the received signal power detected by RSSI at the time of reception is at a high level, the connection a terminal and the c terminal of the antenna switch 1 and the changeover switch 13
Switch to the h terminal and i terminal, and connect to the transmission side. The received signal is input to the transmitting side via the antenna switch 1,
The signals input from the d terminal of the directional coupler 10 are combined, output from the f terminal, and input to the receiving unit via the changeover switch 13. Since the signal input to the band-pass filter 2 of the receiving unit is attenuated by the directional coupler 10, it has the same effect as the conventional attenuator. The signal input to the receiving side is processed in the same manner as in the related art and demodulated by demodulation processing. As described above, when the received signal power is at a high level, the switching of the antenna switch 1 and the connection of the directional coupler 10 to the receiving section are performed, thereby preventing saturation. The number of attenuators can be reduced, and a complicated level control for the attenuator is not required in the control unit.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram showing an embodiment of the present invention. FIG. 2 is a block diagram showing a configuration example of a conventional digital wireless device. [Explanation of Signs] 1: Antenna switch, 2: Bandpass filter, 3:
Amplifier, 4: local signal generator, 5: frequency conversion mixer,
6: RSSI, 7: control unit, 8: reception IF unit, 9: demodulation processing unit, 10: directional coupler, 11: transmission PA, 12:
Transmission unit, 13: switch, 14: attenuator.

Claims (1)

Claims: 1. A digital radio having an antenna, a transmission unit, a reception unit, and a switching unit for selecting and connecting one of the transmission unit and the reception unit to the antenna. In the case where the received signal has a higher input level than a predetermined value at the time of reception, the switching unit is connected to the transmission unit side,
A digital radio, wherein an output signal of a directional coupler provided in the transmission unit is connected to an input terminal of a reception unit.