JPS6240810A - Transmission/reception branching filter - Google Patents

Abstract

PURPOSE:To input a transmitting signal of a large power without using a capacitor having a large dielectric strength performance, by providing a band-stop filter and a BPF on a transmitting signal path and a receiving signal path, respectively. CONSTITUTION:A transmitting signal passes through a band-stop filter 1 which is tuned to a receiving signal frequency, and it is outputted from a common terminal ANT. On the other hand, a receiving signal which has been inputted to the terminal ANT passes through a BPF 2 which is tuned to the receiving signal frequency and outputted. Accordingly, even in case of inputting a transmitting signal of a large power to a terminal TX, a voltage which is generated in both terminals of a capacitor C1 is small enough, therefore, a transmission/ reception branching filter can be constituted by using a small-sized C1 whose dielectric strength performance is low.

Description

Detailed Description of the Invention (Industrial Application Field) The present invention separates transmitted and received signals from each other by using different signal frequencies for transmission and reception (hereinafter referred to as transmission and reception). For example, the present invention relates to a duplexer for transmitting and receiving signals (hereinafter referred to as a transmitting/receiving duplexer) used in a shared transmitting/receiving antenna, and particularly to a transmitting/receiving duplexer for use with large power transmission signals.

(Prior Art) Conventionally, this type of transmitter/receiver duplexer has a transmission signal input terminal TX (hereinafter simply input terminal T), as shown in the circuit shown in FIG.
X and -5), the common terminal ANT (hereinafter simply referred to as common terminal ANT) that simultaneously outputs the transmit signal and inputs the receive signal
A bandpass filter 11 tuned to the transmission signal frequency is arranged in the transmission signal path leading to the common terminal AN.
T to output terminal RX of the received signal (hereinafter simply referred to as output terminal R)
A bandpass r-wave generator 12 tuned to the received signal frequency is disposed on the received signal path leading to the received signal (referred to as X).

In FIG. 2, the multiplied signal input to the input terminal TX passes through the bandpass filter 11 and is output from the common terminal ANT. For this 0 transmission signal, the bandpass filter 12 tuned to the reception signal frequency exhibits an open characteristic, so the transmission signal is not output to the output terminal T (X, but is output from the common terminal ANT). On the other hand, the received signal input to the common terminal ANT passes through the band pass filter 12 and is output from the output terminal source. shows an open characteristic, so the received signal is not output to the input terminal TX, but is entirely output from the output terminal RX.

Here, as shown in FIG. 2, the bandpass filter 11 is generally equivalently represented by a series resonant circuit of an inductor L2 and a capacitor C2, and the voltage generated at both terminals of the capacitor C2 is bandpass filter 11. It is known that the resonance frequency of the filter 11 is QL times the passing signal voltage.

Here, QL is a value determined from the passband frequency width of the bandpass P-wave device 11, and generally takes a value of 10 to 100.

Therefore, the capacitor C2 must have a withstand voltage performance of 10 to 100 times the transmission signal voltage inputted to the input terminal 'T'XK.

(Problem to be Solved by the Invention) However, since the capacitor C2 with high withstand voltage performance is large in size, the input terminal TXr is not suitable for transmitting and receiving signals in a transmitter/receiver duplexer that inputs a high power transmission signal. There was a drawback that the size of the corrugator became very large.

Therefore, an object of the present invention is to provide a small transmitting/receiving/receiving duplexer that can input a high power transmission signal without using the capacitor C2 having high withstand voltage performance.

(Means for Solving the Problem) The transmitter/receiver duplexer according to the present invention is provided with a band-elimination filter tuned to the reception signal frequency in the transmission signal path from the input terminal TX to the common terminal ANT, and The main receiving signal path from the common terminal ANT to the output terminal RX is provided with a bandpass filter tuned to the receiving signal frequency.

(Example) The present invention will be described with reference to the drawings.

FIG. 1 is an equivalent circuit diagram of a transmitting/receiving duplexer showing an embodiment of the present invention.

In FIG. 1, a transmission signal input to an input terminal TX passes through a band-elimination filter 1 and is output from a common terminal ANT. Here, the band-elimination F4 wave filter is tuned to the frequency of the received signal, and exhibits short-circuit characteristics for the transmission signal with a different frequency, so the transmitted T-G signal is not attenuated and is filtered through the band-elimination filter. Pass through vessel 1. Furthermore, since the bandpass filter 2 is tuned to the reception (3 signal frequency) and exhibits an open characteristic for a transmission signal having a frequency different from this, the transmission signal is not output to the output terminal RX. figure,
All are output from the common terminal ANT. On the other hand, the received signal inputted to the common terminal A'NTV'c passes through a bandpass filter 2 tuned to the frequency of the received signal, and is output from the output terminal RX. Here, the band-elimination P-wave device 1 is tuned to the received signal frequency and exhibits openness to the received signal, so the received signal is not output to the input terminal Tx,
All are output from the output terminal R'X.

By the way, as shown in FIG. 1, the band-elimination filter 1 is generally equivalently represented by a parallel resonant circuit including an inductor L1 and a capacitor C1. Here, there is almost no voltage generated across both terminals of the capacitor C1 due to the transmission signal input to the input terminal TX because the band-elimination filter 1 is not tuned to the transmission signal frequency.

That is, even when a high-power transmission signal is input to the input terminal TX, the voltage generated across both terminals of the capacitor C1 is sufficiently small, and therefore a small capacitor C with low withstand voltage performance is used.
1 can be used to configure a transmitter/receiver duplexer.

In the above explanation, in order to make the explanation easier to understand, a transmission/reception duplexer using a lumped constant inductor L1 and a capacitor CI is shown as an example, but a distributed constant inductor L1 and a capacitor CI are used as an example. It is clear from the theory of electric circuits that similar results can be obtained with a transmitting/receiving duplexer using the following.

(Effects of the Invention) As described above, according to the present invention, even in a transmitter/receiver/demultiplexer that inputs a high-power transmission signal, the capacitor C1 with low withstand voltage performance is used to transmit, receive, and demultiplex signals. The present invention has the effect of making the transmitter/receiver duplexer smaller because it has the function of separating the transmitting signal and the receiving signal as in the conventional case.

[Brief explanation of drawings]

FIG. 1 is an equivalent circuit diagram showing an embodiment of a transmitting/receiving duplexer according to the present invention, and FIG. 2 is an equivalent circuit diagram showing a conventional transmitting/receiving duplexer. TX...transmission signal input terminal, RX...reception signal output terminal, ANT...common terminal for simultaneously outputting the transmission signal and inputting the reception signal, LL, L2...inductor,
CLC2...capacitor, 2. IIF 12...
Band-pass filter, 1...band-rejection filter. Agent Patent Attorney Shinsuke Honjo Figure 1

Claims (1)

[Claims] The transmitter has an input terminal for a transmission signal, an output terminal for a reception signal having a frequency different from that of the transmission signal, and a common terminal for simultaneously outputting the transmission signal and inputting the reception signal, and having a frequency different from that of the transmission signal. In a transmitting/receiving duplexer that separates the transmitting signal and the receiving signal by utilizing the fact that the frequencies of the receiving signals are different from each other, the frequency of the receiving signal is tuned to the receiving signal between the input terminal and the common terminal. A transmitter/receiver/demultiplexer characterized in that a band-elimination filter is provided, and a band-pass filter tuned to the received signal frequency is provided between the output terminal and the common terminal.