JP2003008471A - Digital radio equipment - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide digital radio equipment adopting the time division multiplex system that avoids distortion caused in a reception system circuit section at reception of a high level input signal and mismatching caused in the reception system circuit section. SOLUTION: The digital radio equipment is provided with a transmission/ reception changeover switch 13 that switches a connection destination of a transmission reception signal to a transmission system circuit or a reception system circuit, a termination circuit changeover switch 18 that connects an input to the reception system circuit to a terminator, a level detection circuit 16 that detects a reception signal level, and a control circuit 17 that controls the switch 13 to select the transmission circuit side and controls the switch 18 to connect the input of the reception system circuit to the terminator when the reception signal level detected by the detection means is a default level or over causing distortion to the reception system circuit section.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a time division multiplexing digital radio apparatus.

[0002]

2. Description of the Related Art In a conventional time division multiplexing digital radio apparatus, as shown in Japanese Patent Laid-Open No. 8-237162 or Japanese Patent Laid-Open No. 9-130292, a receiving system circuit receives a strong input signal. To prevent distortion, when a received signal level above a certain specified value is detected, the switch that switches the connection destination of the transmitted / received signal between the transmission system circuit and the reception system circuit is switched to the transmission system circuit side, and the switch A method of using the isolation loss to attenuate the level of the received signal input to the receiving circuit side is adopted.

FIG. 2 is a block diagram showing the structure of such a conventional digital radio apparatus. In FIG. 2, 1 is an antenna for transmitting and receiving radio waves, 2 is a filter for passing a specific frequency band, 3 is a transmission / reception changeover switch, 4
Is a transmission circuit section, 5 is a reception circuit section, 6 is a level detection circuit, and 7 is a control circuit.

Next, the operation of the above conventional example will be described.
In FIG. 2, when a radio wave is received by the antenna 1, the received signal is transmitted to the transmission / reception changeover switch 3 through the filter 2 that allows a specific frequency band to pass. At the time of reception, the transmission / reception changeover switch 3 is switched to the receiving system circuit section 5 side, the received signal is transmitted to the level detection circuit 6 via the reception circuit section 5, and the level detection circuit 6 determines the received signal level.

The level detection circuit 6 has a function of detecting the intensity level of the received signal that causes distortion in the receiving system circuit as a specified value, and the intensity level of the received signal is a strong input signal exceeding the specified value. When the determination is made, the transmission / reception changeover switch 3 is changed over to the transmission system circuit section 4 side by the control signal from the control circuit 7.

When the transmission / reception changeover switch 3 is changed over to the transmission system circuit 4 side, an isolation loss occurs in the reception signal due to the transmission / reception changeover switch 3, and the reception signal level input to the reception system circuit section 5 is generated. Will be attenuated by this isolation loss. As a result, it is possible to prevent distortion when the strong input signal is received by the receiving circuit unit 5.

[0007]

However, in the above-mentioned conventional digital radio apparatus, the transmission / reception changeover switch is controlled to connect the reception signal to the transmission circuit side so as not to cause distortion when a strong input signal is received. By switching, the input of the receiving system circuit connected to the selector switch becomes an open end, the original matching state of the receiving system circuit part cannot be maintained, the desired characteristics cannot be obtained, and in the worst case, the oscillation of the amplifier There was a problem that.

The present invention solves such a problem by controlling so as not to cause distortion in the receiving system circuit section when a strong input signal is received, and solving the problem of the matching state of the receiving system circuit section. An object of the present invention is to provide a digital radio device having excellent stability without fear of oscillation of an amplifier.

[0009]

According to a first aspect of the present invention, there is provided a digital radio apparatus which switches a connection destination of a transmission / reception signal obtained from an antenna through a filter between a transmission system circuit and a reception system circuit. Switch means (transmission / reception changeover switch 13), second switch means (termination circuit changeover switch 18) for connecting the input of the reception system circuit to the terminator, and detection means (level detection circuit) for detecting the reception signal level. 16) and switching the first switch means between the transmission system circuit and the reception system circuit according to the reception signal level detected by the detection means, and the first switch means is set to the transmission system circuit side. When switched, the second switch means connects the input of the receiving system circuit to the terminator, and when the first switch means is switched to the receiving system circuit. To are those wherein the second switching means and a control means for controlling so as not to connect the input of the receiving circuit to the terminator (control circuit 17), the.

According to another aspect of the digital radio apparatus of the present invention, during the reception section time, the first signal is received by the strong input signal reception.
When the switch means switches the connection destination of the received signal to the transmission system circuit side, the second switch means connects the input of the reception system circuit to the terminator so that the input of the reception system circuit becomes an open end. It is possible to solve the problem that the original matching state cannot be maintained and the oscillation of the amplifier may occur.

A digital radio apparatus according to claim 2 of the present invention is the digital radio apparatus according to claim 1,
When the received signal level detected by the detecting means exceeds a level that causes distortion in the receiving system circuit,
By the control means, the first switch means switches the connection destination of the transmission / reception signal from the reception system circuit to the transmission system circuit,
The second switch means controls the input of the receiving system circuit so as to be connected to the terminator.

According to another aspect of the digital radio apparatus of the present invention, when the level of the received signal detected by the detecting means exceeds a level that causes distortion in the receiving system circuit,
By performing the switching operation by the first switch means and the second switch means according to claim 1, it is possible to maintain stable reception characteristics without causing distortion in the reception system circuit even when a strong input signal is received. it can.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing the configuration of a digital radio apparatus according to an embodiment of the present invention.

In FIG. 1, 11 is an antenna for transmitting and receiving radio waves, 12 is a filter for passing a specific frequency band,
13 is a transmission / reception changeover switch, 14 is a transmission system circuit section, 15 is a reception system circuit section, 16 is a level detection circuit, 17
Is a control circuit, 18 is a termination circuit changeover switch, and 19 is a termination circuit.

Next, the operation of the above embodiment will be described.
In FIG. 1, when a radio wave is received by the antenna 11, the received signal is transmitted to the transmission / reception changeover switch 13 through the filter 12 that allows a specific frequency band to pass. During the reception section time, the transmission / reception changeover switch 13 is changed over to the reception system circuit section 15 side, the termination circuit changeover switch 18 is opened, and the termination circuit 19 is not connected to the input of the reception circuit. The received signal is received by the receiving circuit unit 15.
Is transmitted to the level detection circuit 16 and the level detection circuit 16 determines the received signal level.

The level detection circuit 16 has a function of detecting a strength level of a reception signal which causes distortion in a reception system circuit as a specified value, and the strength level of the reception signal is a strong input signal exceeding the specified value. If determined, the transmission / reception changeover switch 13 is changed over to the transmission system circuit section 14 side by the control signal from the control circuit 17, and the termination circuit changeover switch 18 is closed to connect the termination circuit 19 to the input of the reception circuit. To be done.

When the transmission / reception changeover switch 13 is changed over to the transmission system circuit 14 side, an isolation loss occurs in the reception signal due to the transmission / reception changeover switch 13, and the reception signal level input to the reception system circuit section 15 is generated. Will be attenuated by this isolation loss.

Further, when the terminal changeover switch 18 is closed, the input of the receiving system circuit section 15 which is opened by the switching of the transmission / reception changeover switch 13 is the terminal circuit 19.
Terminated by. As a result, distortion of the receiving system circuit section 15 at the time of receiving a strong input signal can be prevented, and the input of the receiving system circuit section can maintain the original matching state, and stable reception characteristics can be obtained without oscillation of the amplifier. Obtainable.

[0019]

As described above, according to the present invention,
In a time division multiplexing digital radio device, when a received signal with an intensity level higher than a certain specified value is input, the transmission / reception changeover switch, which is switched to the receiving circuit side during the normal reception interval time, is set to the transmitting system circuit side. By switching to, and connecting the termination circuit to the receiving circuit side, the effect that the input of the receiving system circuit section maintains the original matching state and stable receiving characteristics can be obtained without oscillation of the amplifier Have.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of a digital wireless device according to an embodiment of the present invention.

FIG. 2 is a block diagram showing a configuration of a conventional digital wireless device.

[Explanation of symbols]

1, 11 antenna 2, 12 filters 3, 13 Transmit / receive switch 4, 14 Transmission system circuit 5,15 Receiver circuit 6, 16 level detection circuit 7,17 Control circuit 18 Termination circuit changeover switch 19 Termination circuit

Claims (2)

[Claims] 1. A first switch means for switching a connection destination of a transmission / reception signal between a transmission system circuit and a reception system circuit; a second switch means for connecting an input of the reception system circuit to a terminator; A reception signal detected by the detection means for detecting a reception signal level in the transmission / reception signal; and a control means for controlling the first switch means and the second switch means. The first switch means is switched between the transmission system circuit and the reception system circuit according to the level, and when the first switch means is switched to the transmission system circuit, the second switch means is used for the reception system circuit. The input of the system circuit is connected to the terminator, and when the first switch means is switched to the receiving system circuit, the second switch means does not connect the input of the receiving system circuit to the terminator. Digital radio apparatus and controls so. 2. The control means switches the connection destination of the transmission / reception signal from the reception system circuit to the transmission system circuit when the level of the reception signal detected by the detection means exceeds a level that causes distortion in the reception system circuit. 2. The digital radio apparatus according to claim 1, wherein the first switch means is controlled as described above, and the second switch means is controlled so as to connect the input of the reception system circuit to a terminator.