JPH08154067A - Transmitter/receiver for time division two-way communication - Google Patents

Abstract

PURPOSE: To avoid the interference of an intermediate frequency(IF) step from a transmission system to a reception system at the transmission/reception time of a TDD transmitter/receiver. CONSTITUTION: This device is provided with a second local oscillator 8 and a reception IF mixer 9 in addition to a first local oscillator 5 for applying a first local oscillation frequency to the reception mixer of the reception system and a transmission mixer 6 of the transmission system to which a transmission/ reception sharing antenna 1 is connected while being switched by a switcher 2. A control part 11 controls first and second local oscillation frequencies at the time of reception and transmission so that the frequencies of a reception IF signal (a) and a transmission IF signal (b) can be made different.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a time division multiple access (TDMA: Ti) used as a digital multiplex communication system.
The present invention relates to a transmitter / receiver used in a me Division Multiple Access) system, and more particularly, to a transmitter / receiver for time division duplex (TDD: Time Division Duplex), which is also called ping-pong transmission and performs transmission and reception using the same frequency in a time division manner. Is. In this system, effective use of frequency and multiple connection are possible, so effective use of lines is achieved.

[0002]

2. Description of the Related Art A TDD transceiver used in a TDMA system is a transceiver for performing transmission and reception alternately in time division using the same frequency. This is very compatible with effective use of frequencies. As a specific example, in the second-generation cordless telephone, the master unit (CS) transmits 4 slots,
The mobile phone (PS) has four slots for reception, one slot for transmission, and one slot for reception, so that ping-pong transmission can be performed.

[0003]

In this TDD communication system, transmission and reception are performed at the same frequency. Therefore, in the transmitter and receiver, the intermediate frequencies of the transmission system and the reception system are equal, so that the interference from the transmission system to the reception system during reception. Occurs, and stable reception data cannot be obtained.

An object of the present invention is to provide a transceiver for time division two-way communication (TDD), which can eliminate the interference between the transmitting and receiving systems in the conventional TDD transceiver and can perform stable communication. .

In the TDD transceiver according to the present invention, a transmission / reception common antenna for transmitting / receiving the same frequency transmission / reception is switched and connected to a reception system and a transmission system by a switch, and the reception mixer of the reception system and the transmission mixer of the transmission / reception system are connected to each other. A first local oscillator that gives a local oscillation frequency of 1, a demodulation circuit that demodulates a predetermined reception IF signal output from the reception mixer, and a quadrature that gives a transmission IF signal modulated by a quadrature modulation wave to the transmission mixer. In a transceiver for time-division two-way communication including a modulator, a second local oscillator that outputs a second local oscillation frequency lower than the frequency of the first local oscillator, and the output from the reception mixer. Receive IF
An IF mixer that mixes a signal and a second local oscillation frequency from the second local oscillator to output the predetermined reception IF signal; and an oscillation frequency of the first local oscillator during transmission and reception. By controlling the oscillation frequency of the second local oscillator given to the IF mixer and the quadrature modulator, the frequency of the reception IF signal output from the reception mixer and the frequency of the transmission IF signal output from the quadrature modulator are controlled. It is characterized in that it is provided with a control unit for making them different.

[0006]

According to the present invention, the same intermediate frequency is not used for the transmission system and the reception system, but different intermediate frequencies are generated at the time of transmission and at the time of reception by using the second local oscillator, and the local oscillation frequency is transmitted. At times, it works in combination with different intermediate frequencies during reception to obtain the required radio frequency signal.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a block diagram of essential parts of a transceiver according to an embodiment of the present invention. In the figure, 1 is a transmission / reception shared antenna, 2 is a transmission / reception switch, 3 is a reception system low noise amplifier (LNA: Low Noise Amplifier), 4 is a reception mixer,
5 is a first local oscillator, 6 is a transmission mixer, 7 is a transmission amplifier, 8 is a second local oscillator, 9 is an IF mixer, 10
Is a quadrature modulator, and 11 is a controller. The first and second local oscillators 5 and 8 have a phase synchronization (PLL) configuration using a voltage controlled oscillator (VCO), and the oscillation frequency can be controlled by the control voltage from the control unit 11.

During the receive slot, the radio frequency received is
By the local oscillation frequency from the first local oscillator 5,
The reception mixer 4 down-converts the first reception IF signal a. The first reception IF signal a is further down-converted by the second local oscillation frequency from the second local oscillator 8, and the second reception IF signal (10.7M
Hz) to the demodulation circuit and the received data is demodulated. At this time, the first and second local oscillators 5 and 8
The frequency of is controlled by the control unit 11.

In the transmission slot, the second local oscillator 8
A second local oscillating frequency different from that at the time of reception is output from and is modulated by the quadrature modulation wave (I / Q) input to the quadrature modulator 10, and becomes a transmission IF signal b. The transmission IF signal b is up-converted by the transmission mixer 6 to a first local oscillation frequency different from that at the time of reception from the first local oscillator 5, and converted into a radio frequency. Also at this time, the control unit 11 controls the frequencies of the two local oscillators.

FIG. 2 is an explanatory view of the operation of the present invention, and is an explanatory view of a frequency relationship in which the oscillation frequencies of the first local oscillator 5 and the second local oscillator 8 during transmission and reception are controlled by the control unit 11. . Taking the second generation cordless telephone system as an example, the radio frequency is 1895.15MHz-
In the band of 1917.95 MHz, the channel spacing is 300.
kHz and 77ch. Radio frequency 189 for explanation
It is set to 5.15 MHz. When receiving the radio frequency of 1895.15 MHz, the first local oscillator 5 receives 1805.1.
Controlled to output a local oscillation frequency of MHz,
The second local oscillator 8 is controlled to output the second local oscillation frequency of 79.35 MHz. By this operation, the frequency of the first reception IF signal a is 90.05 MH
z, and the frequency of the second received IF signal is 10.
It becomes 7MHz.

Next, in order to transmit the radio frequency of 1895.15 MHz, the first local oscillator 5 is 1806.6.
The second local oscillator 8 is controlled to output the first local oscillation frequency of MHz, and the second local oscillator 8 outputs the second local oscillation frequency of 88.55 MHz.
It is controlled to output the local oscillation frequency of. Then, the second local oscillation frequency is applied to the quadrature modulator 10. By this operation, the frequency of the transmission IF signal b is 88.
55MHz, radio frequency required 1895.15M
It becomes Hz.

[0012]

The output frequencies of the first and second local oscillators are controlled to be different at the time of transmission and at the time of reception, whereby the transmission IF signal b and the reception IF signal a are controlled.
Since the frequencies can be made different, accurate communication is possible without interfering with each other at the intermediate frequency stage during transmission and reception. Further, since only one second local oscillator needs to be added, the device can be downsized and power can be saved.

[Brief description of drawings]

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

FIG. 2 is an operation explanatory diagram of the present invention.

[Explanation of symbols]

 1 Antenna 2 Switcher 3 Low Noise Amplifier 4 Reception Mixer 5 First Local Oscillator 6 Transmission Mixer 7 Transmission Amplifier 8 Second Local Oscillator 9 IF Mixer 10 Quadrature Modulator 11 Control Unit

Claims (1)

[Claims] 1. A transmission / reception shared antenna for transmitting / receiving the same frequency transmission / reception is switched and connected to a reception system and a transmission system by a switch, and a first local oscillation frequency is applied to a reception mixer of the reception system and a transmission mixer of the transmission / reception system. A first local oscillator for providing, a demodulation circuit for demodulating a predetermined reception IF signal output from the reception mixer, and a quadrature modulator for providing the transmission IF signal modulated by the quadrature modulation wave to the transmission mixer are provided. In a transceiver for time-division bidirectional communication, a second local oscillator that outputs a second local oscillation frequency lower than the frequency of the first local oscillator, a reception IF signal output from the reception mixer, and the Second
An IF mixer that mixes with a second local oscillation frequency from the local oscillator and outputs the predetermined reception IF signal; and an oscillation frequency of the first local oscillator and the IF mixer when transmitting and receiving. A control unit for controlling the oscillation frequency of the second local oscillator given to the quadrature modulator to make the frequency of the reception IF signal output from the reception mixer different from the frequency of the transmission IF signal output from the quadrature modulator; A transmitter / receiver for time-division two-way communication characterized by including.