JPH04192946A - Duplexer - Google Patents

Abstract

PURPOSE:To prevent a received signal from being inputted to a filter for transmission, to prevent a transmitted signal from being inputted to a filter for reception, to shorten the length of a line and to miniaturize the duplexer by providing a trap circuit between the filters for transmission and reception and a common terminal. CONSTITUTION:A trap circuit 3 is composed of a resonance circuit Q5, and a resonance frequency is made coincident to the central frequency of the received signal by adjusting a coil L5 and a capacitor C5. Therefore, the received signal received by a common terminal 4 is blocked by the circuit 3 and is not inputted to a filter 2 for transmission. On the other hand, a trap circuit 5 is composed of a resonance circuit Q6, and a resonance frequency is made coincident to the central frequency of the transmitted signal by adjusting a coil L6 and a capacitor C6. Therefore, the transmitted signal is blocked by the circuit 5 and is not inputted to a filter 6 for reception. Thus, there is no problem even when shortening the length of the line between the filters 2 and 6 and the common terminal 4, and the duplexer can be miniaturized.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a duplexer used in telephones and the like that perform transmission and reception.

■Rice■And± There are two types of duplexers based on their configuration: an integrated type and a separate type.

As shown in FIG. 4, the configuration of the latter separate type duplexer is that a transmitting bandpass filter 13 is provided between the input terminal 11 on the transmitting side and the common terminal 12 on the antenna side, and the input terminal on the receiving side It has a configuration in which a reception bandpass filter 15 is provided between the line between the terminal 14 and the common terminal 12, and the transmission signal inputted from the transmission side input terminal 11 passes through the transmission bandpass filter 13 and then is sent to the common terminal 12. A received signal outputted from the common terminal 12 and received at the common terminal 12 is outputted to an input terminal 14 on the receiving side after passing through a receiving band-pass filter 15. It should be noted that the above-mentioned transmitting signal and receiving signal have different frequencies, and the transmitting/receiving bandpass filters 13 and 15 have different center frequencies depending on the transmitting signal and the receiving signal. has been done.

By the way, in the conventional duplexer described above, since the bandpass filters 13 and 15 with different center frequencies are connected, the center frequency of the other bandpass filter is open. It is necessary to make the state, that is, the impedance, infinite. For this purpose, it is necessary to design the line length between the bandpass filters 13 and 15 and the common terminal 12 to be λ/4 (λ: wavelength), for example. Therefore, if the line is constructed from a stripline, the stripline line connecting the two bandpass filters 13 and 15 will be long and large in size, and it will be difficult to manufacture the line to the specified length as described above. was difficult.

Further, as the transmitting band-pass filter 13, a filter having the desired frequency characteristics shown in FIG. 5, for example, a center frequency fo of 785.8 MHz is used, and as the receiving band-pass filter 15, a filter having the desired frequency characteristics shown in FIG. 6 alone is used. Even if the desired frequency characteristics shown in FIG. 7 are used, for example, the center frequency fo is 881.5 MHz, the characteristics between the input terminal 11 on the transmitting side and the common terminal 12 deteriorate as shown in FIG. That is, the center frequency f of the attenuation characteristic A1. moves from 785.8MHz,
Furthermore, the peak value of the reflection loss B1 is also shifted. Further, the characteristics between the receiving side input terminal 14 and the common terminal 12 deteriorate as shown in FIG. That is, the center frequency f of the attenuation characteristic A2. has moved from 881°5 MHz, and the peak value of the reflection loss B2 has also moved. Therefore, the material was not durable enough to be used as a duplexer. Note that in order to make it usable, it is possible to change the characteristics of the bandpass filter so that it does not affect the characteristics when assembled in a duplexer, but in this case also the shape may become larger or It was very difficult to adjust.

The present invention has been made in view of the above circumstances, and it is possible to produce a band-pass filter that does not change much in frequency characteristics even when produced using a single band-pass filter having a desired frequency characteristic, and is small and easily produced. The purpose is to provide a duplexer that can.

i ''° The present invention outputs a transmission signal input from a transmitter from a common terminal, and when a reception signal having a different frequency from the transmission signal is received at the common terminal, the reception signal is output to the reception section. In the separate type duplexer configured to A receiving band-pass filter has a pass band defined as a frequency and provides the passed signal to the receiving section, and a first band-pass filter is provided on the output side of the transmitting band-pass filter and traps the received signal from the common terminal. It is characterized by comprising a trap circuit and a second trap circuit that is provided on the input side of the reception bandpass filter and traps the transmission signal from the transmission section.

According to the present invention, the trap circuit provided between the transmitting bandpass filter and the common terminal can prevent the received signal from entering the transmitting bandpass filter, and also prevent the receiving signal from entering the transmitting bandpass filter. A trap circuit provided between the line between the pass filter and the common terminal can prevent the transmission signal from entering the reception bandpass filter.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be specifically described below with reference to the drawings. 1st
The figure is a block diagram showing a duplexer according to the present invention. This duplexer has an input terminal 1 that inputs a transmission signal from a transmitter (not shown), a transmission bandpass filter 2 that inputs the signal from the input terminal 1, and a card that passes the transmission signal that has passed through the transmission bandpass filter 2. Circuit 3 and
Outputs the transmission signal that has passed through the trap circuit 3 to an antenna etc.
Also, a common terminal 4 for receiving signals transmitted from the outside,
A troubleshooting circuit 5 that passes the received signal to the common terminal 4
, a reception bandpass filter 6 for inputting the received signal that has passed through the trap circuit 5, and an input terminal 7 for inputting the signal from the reception bandpass filter 6 and applying it to a receiver (not shown).

The transmission bandpass filter 2 is for removing unnecessary signal components of the transmission signal from the transmitter, and includes a resonant circuit Q1 consisting of a coil L1 and a capacitor C1,
Capacitors CI' and C2 are connected to each side of the coupled resonant circuit Q2 consisting of a coil L2 and a capacitor C2.
', and both ends of the capacitor C12 are connected with capacitors CI' and C2' in between. The center frequency of the passband of this transmitting bandpass filter 2 is determined by the coils Ll, L2 and the capacitor CI.

By adjusting the value such as 02, it is matched to the center frequency of the transmission signal from the transmitter, for example, 785.8.
It is set to MHz. Therefore, the transmission signal from the transmitter is applied to the common terminal 4 via the trap circuit 3 after unnecessary signal components are removed by the transmission bandpass filter 2 .

The trap circuit 3 is provided to prevent the received signal received at the common terminal 4 from entering the transmitting bandpass filter 2, and as shown in the figure, the trap circuit 3 is provided with a coil L5 and a capacitor C5.
A resonant circuit Q5 consisting of the following is used. The resonance frequency of this trap circuit 3 is between the coil L5 and the capacitor C5.
By adjusting the value of , it is possible to match the center frequency of the received signal, which is, for example, 881.5 MHz. Therefore,
The transmission signal that has passed through the transmission bandpass filter 2 passes through the trap circuit 3 as it is, is applied to the common terminal 4, and is transmitted from an antenna or the like. On the other hand, the reception signal received at the common terminal 4 is blocked by the trap circuit 3 and is not input to the transmission bandpass filter 2.

One trap circuit 5 is provided to prevent the transmission signal from the transmitter from entering the receiving bandpass filter 6, and as shown in the figure, a resonant circuit Q6 consisting of a coil L6 and a capacitor C6 is used. ing. The resonance frequency of the trap circuit 5 is made to match the center frequency of the transmission signal, which is, for example, 785.8 MHz by adjusting the values of the coil L6 and capacitor C6. Therefore, the reception signal received at the common terminal 4 passes through the trap circuit 5 as it is and is applied to the reception bandpass filter 6. On the other hand, the transmission signal that passes through the transmission bandpass filter 2 and is applied to the common terminal 4 is blocked by the trap circuit 5 and is not input to the reception bandpass filter 6.

The reception bandpass filter 6 is for removing unnecessary signal components of the reception signal input to the common terminal 4, and is a resonant circuit Q3 consisting of a coil L3 and a capacitor C3.
and a resonant circuit Q4 consisting of a coil L4 and a capacitor C4.
It has a structure in which capacitors C3' and C4' are provided on both sides of the coupled circuit, and both ends of capacitor C34 are connected with capacitors C3' and C4' in between.

The center frequency of the passband of this reception bandpass filter 6 is the coil L3. By adjusting the values of L4 and capacitors C3 and C4, the center frequency of the received signal input to the common terminal 4 is matched, for example, 881.5.
It is set to MHz.

Therefore, an externally received signal input to the common terminal 4 has unnecessary signal components removed by the receiving bandpass filter 6, and is output to an external receiver (not shown).

FIG. 2 is a diagram showing the frequency characteristics between the input terminal 1 on the transmitting side and the common terminal 4 in the duplexer configured as described above, and FIG. 3 shows the frequency characteristics between the input terminal 7 and the common terminal 4 on the receiving side. It is a figure which shows the frequency characteristic between. As can be understood from these two figures, in the duplexer according to the present invention, the transmitting band-pass filter 2 and the receiving band-pass filter 6 have center frequencies of 785.8 MHz and 881 MHz.
5 MHz and connect them as described above to form a duplexer, the frequency characteristics between the input terminal 1 on the transmitting side and the common terminal 4 will be good. That is, in FIG. 2, the attenuation characteristic A3 is 785.8 MHz and the center frequency f. and does not change, and the reflection loss B3
Since the peak value of is also present in the same frequency range, it is possible to satisfactorily attenuate the reflected waves. Further, in FIG. 3, the attenuation characteristic A4 is 881.5 MHz and the center frequency f. does not change, and the peak value of the reflection loss B4 also exists in the same frequency range, so the reflected wave can be satisfactorily attenuated.

Therefore, in the duplexer according to the present invention configured as described above, the received signal does not enter the transmission bandpass filter 2 at the trap circuit 3 provided between the transmission bandpass filter 2 and the common terminal 4. can be prevented,
In addition, since the transmission signal can be prevented from entering the reception bandpass filter 6 by the playing card circuit 5 provided between the line between the reception bandpass filter 6 and the common terminal 4, the transmission signal can be prevented from entering the reception bandpass filter 6. These three components can be arranged without being affected by the line length with the terminal 4, so even if a strip line is used for the line, it can be short and compact, and there is no need to pay close attention to the line length. It can be easily produced.

Although resonators are used in the trap circuits 3 and 5 in the above embodiment, the present invention is not limited to this, and other circuit configurations may be used.

As detailed above, according to the present invention, the trap circuit provided between the transmission bandpass filter and the common terminal can prevent the received signal from entering the transmission bandpass filter. In addition, the trap circuit installed between the receiving bandpass filter and the common terminal can prevent the transmitting signal from entering the receiving bandpass filter, so there is no problem even if the line length is shortened. Not only can it be miniaturized, it can also be manufactured easily since it does not require a specified line length, and it can also be manufactured by itself using a bandpass filter with the desired frequency characteristics. This has the excellent effect that the frequency characteristics do not change much and it is easy to design.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing a duplexer according to the present invention,
Figure 2 is a frequency characteristic diagram of the bandpass filter on the transmitting side.
Figure 3 is a frequency characteristic diagram of the bandpass filter on the receiving side.
Figure 4 is a configuration diagram of a conventional duplexer, Figures 5 and 6
The figure is a frequency characteristic diagram of a single bandpass filter used in the duplexer, and FIGS. 7 and 8 are frequency characteristic diagrams of the bandpass filter when incorporated in the duplexer. ■... Input terminal on the transmitting side, 2... Band pass filter for transmitting, 3, 5... Trap circuit, 4... Common terminal, 6... Band pass filter for receiving, 7... Receiving side input terminal. Patent applicant Murata Manufacturing Co., Ltd. Figure 4

Claims (1)

[Claims] (1) A separate type configured to output a transmission signal input from a transmitter from a common terminal, and when a reception signal having a different frequency from the transmission signal is received at the common terminal, output the received signal to the reception section. The duplexer includes a transmission bandpass filter having a passband with a center frequency centered around the frequency of the transmitted signal, and a transmitting bandpass filter for providing the passed signal to a common terminal, and a passband having a center frequency centered around the frequency of the received signal. and a reception bandpass filter for supplying the passed signal to the reception section; a first trap circuit provided on the output side of the transmission bandpass filter for trapping the reception signal from the common terminal; and a reception band. A duplexer comprising: a second trap circuit provided on the input side of a pass filter to trap a transmission signal from a transmission section.