JPH03216002A - Branching filter - Google Patents

Abstract

PURPOSE:To arrange each filter freely decentralizingly and to utilize space in a case effectively by constituting a low frequency area of a low pass filter and a high frequency area of a high pass filter and the low pass filter. CONSTITUTION:The low frequency area is covered by the low pass filter 10. The high frequency area consists of two rejection filters 26, a dielectric waveguide type high pass filter 12 and a board type low pass filter 14, and the low pass filter 14 has a higher cut-off frequency than that of the high pass filter 12. Thus, the signal of a transmission frequency Tx is outputted to an antenna ANT but cut off at the high frequency area and the signal of a reception frequency Rx inputted from the antenna ANT is cut off at the low frequency area but passes through the high frequency area and is fetched in an equipment. Thus, the branching filter arranged freely decentralizingly in the equipment is realized.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a duplexer used in the microwave band, etc., and more specifically, it uses a low-pass filter for the low frequency range, and a high-pass filter and a low-pass filter for the high frequency range. This relates to a duplexer composed of The duplexer of the present invention is useful, for example, as an antenna duplexer for microwave mobile radio equipment.

[Prior Art] For example, in a mobile radio device that uses a simultaneous transmission and reception system, different frequencies are used for transmission and reception. Therefore, a duplexer is used to share one antenna for transmission and reception.

Conventional antenna duplexers use coaxial λ corresponding to the transmission frequency.
．． A dielectric bandpass filter consisting of a /4 resonator and a coaxial λ. It has a configuration in which it is combined with a dielectric bandpass filter consisting of a /4 resonator and housed in a single case. [Problems to be Solved by the Invention] However, the configuration in which two dielectric bandpass filters are assembled in a single case is difficult to manufacture because a high degree of dimensional accuracy is required between each dielectric filter and the case. ＜The disadvantage is that it is difficult to incorporate into equipment because it requires a large and concentrated installation space within the radio device housing.

An object of the present invention is to eliminate the drawbacks of the prior art as described above and to provide a duplexer that can be freely distributed within a device.

[Means for Solving the Problems] FIG. 1 shows a schematic configuration of the present invention that can achieve the above object. The low frequency range is a low pass filter 10 that blocks signals of the other party's frequency, and the high frequency range is a high pass filter 12 and the high pass filter 1 that blocks signals of the other party's frequency.
The low-pass filter l4 has a cut-off frequency higher than the cut-off frequency of No. 2. Therefore, the high pass filter 12
and the low-pass filter 14 substantially constitute a hand-pass filter. Here, we assume an antenna duplexer in which the low frequency band is the transmitting side Tx and the high frequency band is the receiving side Rx.

To improve the characteristics, it is better to combine a rejection filter with a low-pass filter in the low frequency range, and also combine a rejection filter with a high-pass filter in the high frequency range, as shown in Figure 3. .

[Operation] The filter characteristics obtained by such an antenna duplexer are shown in FIG. The low-pass filter 10 in the low frequency range has a characteristic of passing the transmission frequency Tx but blocking the reception frequency Rx. On the other hand, the high-pass filter 12 in the high frequency range has a characteristic of passing the receiving frequency Rx but blocking the transmitting frequency band Tx.

The high frequency range low-pass filter 14 has a reception frequency Rx
It provides attenuation in the higher frequency range and blocks unnecessary signals. This allows the transmitting and receiving antennas to be shared.

In particular, if you combine a low-pass filter and a rejection filter on the low-frequency side, or a high-pass filter and a rejection filter on the high-frequency side, the characteristics shown in each block in Figure 3 will appear on the passband side. The attenuation characteristics become steeper and good demultiplexing characteristics can be obtained.

Embodiment] FIG. 4 is an explanatory diagram showing an embodiment of the present invention, and is an example applied to an antenna duplexer for simultaneous transmission and reception. The low frequency range is composed of low frequency /l/910, and the signal at the transmission frequency Tx is output through the antenna ANT. This low-pass filter 10 has four terminals in which a coil 22 is arranged within a cylindrical dielectric body 20, a plurality of inductances are connected in series, and a plurality of capacitors 24 are connected between the interconnection points of each coil 22. This is an LC circuit network with low bus characteristics.

The high frequency band side consists of two rejection filters 26, a dielectric waveguide type high pass filter 12, and a substrate type low pass filter 14. The high-pass filter I2 is formed by forming a conductive film on almost the entire surface of a dielectric block, forming a waveguide with a cutoff region corresponding to the cross-sectional shape of the dielectric block, and providing input/output coupling parts at both ends of the waveguide. It is something that The low-pass finhole 14 has a structure in which three front electrodes are provided on the front surface of the substrate, a ground electrode is provided on the entire back surface, and the front electrodes are connected with lead wires.

These low-pass filters 1 (1, high-pass filters 12
, low-pass filter 14 are each given characteristics as shown in FIG. Therefore, the signal at the transmitting frequency Tx is output to the antenna NT but is blocked in the high frequency range, and the signal at the receiving frequency Rx input from the antenna ANT is blocked in the low frequency range but passes through the high frequency range and enters the device. be taken in. In this way, one antenna is shared by transmission and reception using different frequencies.

Note that, in principle, the low-pass filter and high-pass filter are not limited to those having the structure of the above-described embodiments, and any structure may be used as long as it has a predetermined characteristic in a predetermined band. The rejection filter is for steepening the attenuation in the pass band, and is desirable because the repulsion characteristics can be improved by adding it, but it may be omitted depending on the required characteristics.

[Effects of the Invention] As described above, the present invention is a duplexer in which the low frequency range is composed of a low pass filter, and the high frequency range is composed of a high pass filter and a low pass filter, so each filter can be freely distributed and arranged. Therefore, they can be incorporated into the radio device's housing by using a corner or distributing them above and below the printed circuit board, making it possible to effectively use the space inside the case and contributing to the miniaturization of the radio device. . Also, unlike the case where a conventional dielectric bandpass filter is housed in a case, it does not require high dimensional accuracy and is easier to manufacture, and the degree of freedom in design and manufacture is increased.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram showing the basic configuration of a duplexer according to the present invention,
FIG. 2 is a filter characteristic diagram thereof, FIG. 3 is an explanatory diagram showing another example of the duplexer according to the present invention, and FIG. 4 is an explanatory diagram showing one embodiment of the present invention. 10...Low pass filter, 12...High pass filter, 14...Low pass filter.

Claims (2)

[Claims] 1. The low frequency range is a low-pass filter that blocks signals of the other party's frequency, and the high frequency range is a demultiplexer consisting of a high-pass filter that blocks signals of the other party's frequency, and a low-pass filter that has a cutoff frequency higher than the cutoff frequency of the high-pass filter. vessel. 2. 2. The duplexer according to claim 1, wherein the low frequency range is comprised of a low pass filter and a rejection filter, and the high frequency range is comprised of a high pass filter, a rejection filter, and a low pass filter.