JPS6035311Y2 - Transmission/reception duplexer - Google Patents

Description

[Detailed Description of the Invention] This invention relates to a transmitting/receiving duplexer for separating transmitting waves and receiving waves in a transmitting/receiving antenna shared system in which transmitting waves and receiving waves are shared by one antenna.

A conventional transmitter/receiver duplexer used in a mobile communication device that uses simultaneous wave transmission and reception in the VHF band and UHF band has the configuration shown in FIG.

A transmitter 15 is connected to a terminal 12 of the Y-shaped curator 11 via a transmission bandpass filter 13 and an isolator 14.

A transmitting/receiving antenna 17 is connected to a terminal 16 adjacent to the terminal 12 of the circulator 11 in the forward direction, and a receiver 21 is connected to the other terminal 18 via a receiving bandpass filter 19.
was connected.

In this conventional transmitting and receiving duplexer, the transmitting and receiving antenna 17
If the impedance matching is insufficient, all of the reflected power due to the mismatch will go around to the receiver side 18, so that the apparent reverse coupling attenuation of the Y-shaped curator 11 will be significantly degraded.

Therefore, in order to prevent the reception band components of the sideband noise generated by the transmitter 15 from reaching the receiver 21, it is necessary to increase the number of stages of the transmission bandpass filter 13.

Furthermore, in order to prevent the transmitted wave itself from going around to the receiver 21, it was necessary to increase the number of stages of the reception bandpass filter 19.

Having multiple stages of these filters 13, 19 in this manner has the disadvantage of increasing volume and cost.

In order to eliminate these drawbacks, this invention has a Y-shaped structure.
Instead of a curator, a directional filter tuned to the receiving band is used to improve the deterioration of the coupling attenuation between transmitting and receiving due to the impedance mismatch of the transmitting and receiving antenna, and to reduce the burden on the bandpass filters of transmitters and receivers. The purpose of the present invention is to provide a transmitting/receiving duplexer.

Figure 2 shows an example of a transmitter/receiver duplexer based on this invention.
Parts corresponding to those in the figure are given the same reference numerals.

In this invention, a directional filter 22 tuned to the reception band fr of the receiver 21 is provided.

The directional filter 22 has first to fourth ports 23 to 26, and a curve 27 is shown in FIG. 3 between the first and second ports 23 and 24 and between the third and fourth ports 25 and 26.
A specific band f, as shown as .

shows the bandpass filter characteristics.

between the first and fourth ports 23 and 26, and between the second and third ports
Ports 24 and 25 each have a specific band f as shown by curve 28 in FIG.

shows the band-stop filter characteristics.

Further, between the first and third ports 23 and 25, and between the second and fourth ports 24 and 26, the curve 29 in FIG.
It exhibits large coupling attenuation characteristics as shown in .

This directional filter 22 is tuned to receive band f, that is, f.

=f, selected. Various types of directional filter 22 can be used as long as they have the characteristics shown in FIG.
In FIG. 2, the input/output lines 32 and 33 on opposite sides of a rectangular ring-shaped conductor 31 are connected to each other in the case of a strip line.

Both ends of the input/output lines 32 and 33 are respectively ports,
The length of the ring-shaped conductor 31 determines the tuning frequency of the filter.

A transmitter 15 is connected to the first port 23 through a transmission bandpass filter 13 and an isolator 14 .

A non-reflection terminator 34 is connected to the second port 24, and a receiver 2 is connected to the third port 25 through a reception bandpass filter 19.
1 is connected to the fourth port 26, and a transmitting/receiving antenna 17 is connected to the fourth port 26.
is connected.

According to the configuration shown in FIG. 2, the transmitted wave of the transmitter 15 has the resonant frequency f of the directional filter 22.

Since it is detuned from = fr, the band rejection filter characteristic 2
The signal is supplied to the transmitting/receiving antenna 17 with almost no loss caused by the transmitting/receiving signal.

Further, since the received wave received by the transmitting/receiving antenna 17 is tuned to the directional filter 22, it is supplied to the receiver 21 with almost no loss according to the bandpass filter characteristic 27.

On the other hand, among the sideband noise generated in the transmitter 15, the noise component falling in the reception band 21 reaches the port 24 due to the bandpass filter characteristic 27 between the ports 23 and 24, and then
It is absorbed by the non-reflection terminator 34, and on the other hand, the loopback to the receiver 21 through the antenna 17 side is attenuated by the band rejection filter characteristic 28 between the ports 23 and 26, and does not reach the receiver 21.

The part of the transmitted reflected wave that returns to the port 23 due to the impedance mismatch of the transmitting and receiving antenna 17 is the isolator 14.
On the other hand, it is attenuated by the band-pass filter characteristic 27 between the ports 26 and 25, and almost never reaches the receiver 21 side.

Furthermore, regarding image spurious which is a problem in the case of a super-hetero gain receiver, since the demultiplexer 22 itself has reception bandpass filter characteristics 27, image waves detuned by twice the intermediate frequency can be received. It is sufficiently attenuated before going around to the aircraft 21 side.

Note that the isolator 14 is not necessarily required for this transmission/reception division operation.

As explained above, according to the transmitter/receiver duplexer of this invention,
By using a directional filter, even if the impedance matching of the transmitting/receiving antenna is insufficient, both sideband noise and the transmitted wave will hardly go around to the receiver side, so the coupling attenuation between the transmitting and receiving duplexer itself will be reduced. The amount of attenuation does not deteriorate and a very large amount of attenuation can be obtained.

Furthermore, interference waves outside the band can be sufficiently attenuated by the filter characteristics of the duplexer itself.

Therefore transmit and receive bandpass filters 13 and 19
It has the advantage of significantly reducing the burden on
A passband filter that occupies a large area in a mobile device in an F-band mobile communication system can be made smaller.

[Brief explanation of the drawing]

Figure 1 is a block diagram showing a conventional transmission/reception duplexer, Figure 2 is a block diagram showing an embodiment of the transmission/reception duplexer according to this invention, and Figure 3 is a transmission characteristic curve of the directional filter shown in Figure 2. It is a diagram. 13... Transmission band pass filter, 14...
...Isolator, 15...Transmitter, 17...
...... Transmission and reception antenna, 19... Reception band pass filter, 21... Receiver, 22...
... Directional filter, 23 to 26... First to fourth ports, 34... Terminating terminal.

Claims (1)

[Scope of utility model registration request] It has 1st to 4th ports, and between the 1st and 2nd ports and between the 3rd and 4th ports each exhibits bandpass filtering characteristics in a specific frequency band, and between the 1st and 4th ports, and between the 3rd and 4th ports. A directional filter exhibiting band-stop filtering characteristics in the specific frequency band is provided between the second and third ports, a transmitter is connected to the first port through a transmission band-pass filter, and a transmitter is connected to the first port through a transmission band-pass filter. A non-reflection terminator is connected to the port, a receiver is connected to the third port through a reception bandpass filter, a transmitting/receiving antenna is connected to the fourth port, and the specific frequency band is the receiving band of the receiver. A transmitting/receiving duplexer in which the characteristics of the directional filter are selected so that the following characteristics are obtained.