JPH05252074A - Transmitter-receiver - Google Patents

Abstract

PURPOSE:To eliminate a changeover switch circuit used to selectively connect a transmission/reception antenna to a transmission circuit or a reception circuit in the transmitter-receiver of the TDD system. CONSTITUTION:A switch circuit 42 turned on for a period of a reception slot is provided in a pre-stage of a reception circuit 20. A circulator 41 is connected between a transmission/reception antenna 34, a transmission power amplifier 15 and the switch circuit 42. A transmission signal S13 for a period of transmission slot is fed to the transmission/reception antenna 34 via the power amplifier 15 and the circulator 41. A reception signal S20 received by the transmission/ reception antenna 34 for a period of a reception slot is fed to a reception circuit 20 through the circulator 41 and the switch circuit 42.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a TDD transmission / reception device.

[0002]

2. Description of the Related Art Digital mobile phones such as telepoint systems generally employ the TDD system or TDMA / TDD system in which transmission and reception are performed at the same frequency and so-called ping-pong transmission is performed.

That is, in the case of the TDD system, for example, FIG.
As shown in, one channel (frequency) is temporally divided into a transmission slot T and a reception slot R, and these slots T and R are alternately repeated, and between these slots T and R, A guard band time Tg is provided. As an example, the transmission slot T and the reception slot R are 1 msec, and the guard band time Tg is several tens.
μ seconds. Then, the mobile phone transmits to the base station during the transmission slot T and receives from the base station during the reception slot R.

Since such transmission / reception is performed, T
The transmission circuit and the reception circuit of the DD type transmission / reception device are configured, for example, as shown in FIG.

That is, in FIG. 4, 10 is a transmitting circuit, 20 is a receiving circuit, and 31 is a system controller. The syscon 31 controls the entire operation of the transmitting / receiving device, and is composed of a microcomputer. Further, the sys-con 31 also forms various timing signals and clocks, and the signal from the sys-con 31 is supplied to each circuit (not shown).

Then, in the transmission circuit 10, the analog audio signal S10 is supplied to the transmission processing circuit 11, and processing for transmission such as A / D conversion, time base compression, addition of control data from the syscon 31 is performed, The processed digital voice signal S11 is taken out every period of the transmission slot T, this signal S11 is supplied to the modulation circuit 12 as a modulation signal, and from the modulation circuit 12 every period of the transmission slot T, the digital voice signal S11 is obtained. For example, the FSK-modulated signal S12 (carrier frequency f12 is, for example, 80 MHz)
z) is taken out.

The signal S12 is supplied to the mixer circuit 13, and the local oscillator signal S32 of the frequency f32 is transmitted from the synthesizer oscillator circuit 32 for transmitting / receiving channel setting.
Is taken out, this signal S32 is supplied to the mixer circuit 13, and the signal S12 is frequency-converted into the transmission signal S13 of the frequency f13. In this frequency conversion, f13 = f12 + f32, for example, f32 = 2.6 GHz. The frequency f32, that is, the channel is set by the synthesizer oscillation circuit 32 being controlled by the syscon 31.

Then, the transmission signal S13 is converted into the band pass filter 14 → the power amplifier 15 → the isolator 16 →
The signal is supplied to the transmission / reception antenna 34 through the signal line of the high frequency switch circuit 33 and transmitted to the base station.

The isolator 16 includes an antenna 34.
Even if the impedance of the antenna 34 changes due to the surrounding environment, the load impedance viewed from the power amplifier 15 does not change.

At this time, the switch circuit 33 is switched between the period of the transmission slot T and the period of the reception slot R by the control signal from the syscon 31, and the antenna 3
4 is used by switching to the transmitting circuit 10 and the receiving circuit 20.

Then, in the receiving circuit 20, the transmission signal S transmitted from the base station during the reception slot R is received.
20 (frequency f13) is received by the antenna 34,
This signal S20 is supplied to the first mixer circuit 23 through the signal line of the switch circuit 33 → band pass filter 21 → high frequency amplifier 22, and the local oscillation signal S32 from the oscillation circuit 32 is supplied to the first mixer circuit 23. The signal S20 is frequency-converted into the first intermediate frequency signal S23. In this case, the intermediate frequency of the signal S23 is equal to the frequency f12 of the signal S12.

The signal S23 is supplied to the second mixer circuit 25 through the first intermediate frequency filter 24, and the second local oscillation circuit 26 outputs the second local oscillation signal S.
26 is supplied to the mixer circuit 25, the signal S23 is frequency-converted into a second intermediate frequency signal S25 (the intermediate frequency is, for example, 450 kHz), and this signal S25 is supplied to the demodulation circuit 28 through the second intermediate frequency filter 27 and received. The digital audio signal S28 is demodulated for each period of the slot R, the signal S28 is supplied to the reception processing circuit 29, processing for reception is performed, and the original analog audio signal S29 is extracted. The control data is also extracted from the processing circuit 29 and supplied to the syscon 31.

According to this TDD method, since the transmission signal S13 and the reception signal S20 have the same frequency f13, the base station only performs antenna diversity, and the diversity communication of the up channel and the down channel is performed. Can be realized. Further, frequencies can be continuously assigned to the upstream channel and the downstream channel without dividing the frequency band, and the frequency usage efficiency is good.

[0014]

By the way, as described above, the changeover switch circuit 33 needs to be alternately switched between the period of the transmission slot T and the period of the reception slot R. It must be done at high speed, as shown in.

Therefore, the changeover switch circuit 33 is
Generally, it is composed of a high frequency switching diode such as a fast recovery diode. That is, since the switching diode can only turn on / off the signal, the actual changeover switch circuit 33
As shown in FIG. 5, it is composed of two sets of diodes 33T and 33R, and these diodes 33T and 33R are turned on / off alternately in the period of the transmission slot T and the period of the reception slot R.

In this case, however, if the stray capacitance between the terminals of the diode 33R is large, the transmission signal S13 leaks from the transmission circuit 10 to the reception circuit 20 through the diodes 33T and 33R during the transmission slot T, and the reception signal is received. This adversely affects the circuit 20 and causes a loss in the transmission signal S13 transmitted from the antenna 34. Further, since the diode 33T is supplied with the transmission signal S13 of large power, the diode 33T must be able to withstand large power. Furthermore, if the linearity of the diode 33T is poor, the transmission signal S13 will be distorted and harmful harmonic components will be transmitted.

Therefore, the diode 33R must have a small stray capacitance, and the diode 33T is
The changeover switch circuit 33 becomes extremely expensive because it must have high withstand power and good linearity.

The present invention is intended to solve the above problems.

[0019]

Therefore, in the present invention, when the reference numerals of the respective parts correspond to the embodiments described later, one channel is time-divided into a transmission slot T and a reception slot R, In a transmitter / receiver that performs transmission and reception in a time division manner during the period of the transmission slot T and the period of the reception slot R, the reception slot R is provided in a stage before the reception circuit 20.
The switch circuit 42 that is turned on during the period of
Circulator 41 is connected between the switch circuit 42 and the switch circuit 42, the transmission signal S13 is supplied from the power amplifier 15 to the transmission / reception antenna 34 through the circulator 41 during the transmission slot T, and the transmission / reception antenna 34 during the reception slot R. The received signal S20 received by is supplied to the receiving circuit 20 through the circulator 41 and the switch circuit 42.

[0020]

The transmitting / receiving antenna 34 can be operated by the circulator 41 and the switch circuit 42 without the switching connection of the transmitting / receiving antenna 34.
0 is selectively connected.

[0021]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In FIG. 1, a circulator 41 and a switch circuit 42 are provided between a power amplifier 15 of a transmission circuit 10, a transmission / reception antenna 34, and a bandpass filter 21 of a reception circuit 20.

In this case, for example, as shown in FIG. 2, in the circulator 41, the signal input to the port 3 is output to the port 3 output to the port 3 with respect to the signals accessed to the ports 1 to 3. The signal input to is not output to port 1 The signal input to port 2 is the output to port 1 The signal input to port 2 is not the output to port 3 The signal input to port 1 Has the property that the signal input to port 1 and output to port 3 is not output to port 2. Then, the output of the amplifier 15 is connected to the port 3, the antenna 34 is connected to the port 2,
The port 1 is connected to the input end of the bandpass filter 21 through the switch circuit 42.

The switch circuit 42 is composed of, for example, a switching diode, and is turned on only during the reception slot R.

According to such a configuration, the transmission slot T
During the period, the transmission signal S13 from the amplifier 15 is supplied to the antenna 34 through the port 3 and the port 2 of the circulator 41 and transmitted to the base station.

During the reception slot R, the reception signal S20 from the antenna 34 is supplied to the switch circuit 42 through the ports 2 and 1 of the circulator 41, and during the reception slot R, the switch signal S20 is switched. Since the circuit 42 is on, the received signal S20 from port 1
Is supplied to the receiving circuit 20 through the switch circuit 42.

In this way, the transmission / reception antenna 34 includes the circulator 41 and the switch circuit 42, and the transmission circuit 1
0 and the receiving circuit 20 are selectively connected.

[0027]

According to the present invention, even if the transmission signal S13 from the port 3 leaks to the port 1, the switch circuit 42 is connected to the port 1 and the switch circuit 42 is connected to the transmission slot. Since it is off during the period T, the influence of the transmission signal S13 on the receiving circuit 20 is sufficiently small. Further, since the loss when the transmission signal S13 passes through the circulator 41 and is supplied to the antenna 34 is small, the transmission efficiency is good.

Further, during the reception slot R, most of the reception signal S20 from the antenna 34 is supplied to the reception circuit 20 through the circulator 41 and the switch circuit 42, and the loss is very small.

The level of the transmission signal S13 that must be blocked by the switch circuit 42 during the transmission slot T and the level of the reception signal S20 that the switch circuit 42 must pass during the reception slot R. Are sufficiently small, the capacity of the switch circuit 42 can be small. Moreover, since the switch circuit 42 may be a single-pole / single-throw switch circuit that only turns signals on and off, the number of elements can be reduced.

Further, the transmission signal S13 is the circulator 4
When passing 1, the distortion is hardly generated, so that no harmful harmonic component is transmitted. Further, even if the impedance of the antenna 34 changes due to the environment around the antenna 34, this is blocked by the circulator 41 and the load impedance seen from the power amplifier 15 does not change, so the isolator 1 in FIG.
6 can be omitted. Furthermore, the higher the frequency f13 of the transmitted and received signals S13, S20, the more diode 3
Since the circulator 41 is less expensive than 3T and 33R, it is particularly advantageous in the case of the above example.

[Brief description of drawings]

FIG. 1 is a system diagram showing an example of the present invention.

FIG. 2 is a diagram for explaining an essential part of the present invention.

FIG. 3 is a diagram for explaining transmission / reception slots.

FIG. 4 is a system diagram showing a conventional example.

FIG. 5 is a diagram for explaining a main part of a conventional example.

[Explanation of symbols]

 10 transmitter circuit 12 modulator circuit 13 mixer circuit 15 power amplifier 20 receiver circuit 23 first mixer circuit 25 second mixer circuit 28 demodulator circuit 31 system controller 32 synthesizer oscillator circuit 34 transmit / receive antenna 41 circulator 42 switch circuit

Claims (1)

[Claims] 1. A channel comprises a transmission slot,
In a transmitter / receiver that is time-divided into a reception slot and performs transmission and reception in a time-division manner during the transmission slot period and the reception slot period, a switch circuit that is turned on during the reception slot period before the reception circuit. A circulator is connected between the transmission / reception antenna, the power amplifier for transmission, and the switch circuit, and the transmission signal is supplied from the power amplifier to the transmission / reception antenna through the circulator during the transmission slot period. The receiving / transmitting device is configured to supply the receiving signal received by the transmitting / receiving antenna to the receiving circuit through the circulator and the switch circuit during the receiving slot.