JP2511981B2 - High frequency filter - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high frequency filter which is used in various high frequency devices and equipment and which uses a ring resonator in a frequency band higher than the UHF band.

Conventional Technology It is known that a split ring resonator with a structure in which one transmission line is arranged in a loop and both ends of which are connected by a capacitor exhibits good characteristics in the frequency band above the UH band.

Regarding the filter using this resonator, Patent No. 134872
No. 2 or No. 1007337 describes an electronic tuning filter using a suspended strip line, and FIG. 4 shows an example of a three-stage bandpass filter (BPF) with a fixed center frequency.

In FIG. 4, 11, 12, 13 are frequency tuning capacitors 11a to 13a.
Split ring resonators having the following, 14 and 15 are input / output coupling capacitors, and 41 and 42 are input and output terminals. As can be seen from Fig. 4, the split ring resonators 11 to 13 do not need to be grounded at high frequency, and
Since the connection between 11 and 13 can be easily realized by parallel connection,
When applied to a filter, the structure is extremely simple and the characteristics are good.

Problems to be Solved by the Invention As described above, a filter using a split ring resonator has good characteristics, but has a drawback that it has a large shape.

The present invention has been made in view of recent demands for downsizing of devices.
The object is to reduce the size of the device using the split ring resonator without impairing the good characteristics of the device.

Means for Solving the Problems In the present invention, ring resonators formed by connecting capacitors to both open ends of a loop-shaped transmission line are arranged so as to be parallel-coupled to each other, and an input or output terminal for a high frequency signal is provided as described above. The above object is achieved by providing the loop resonator inside the transmission line.

Action The action of the present invention having the above configuration is as follows.

That is, since the transmission line of the split ring resonator uses a strip line, it does not require a large thickness in a device such as a circuit or a filter, and therefore, it is necessary to reduce the area of the circuit for downsizing. Therefore,
The present invention is intended to miniaturize the circuit by providing an input / output circuit for a high frequency signal in a portion surrounded by a ring or a loop of the resonator.

Example One example of the present invention will be described below.

FIG. 1 is a plan view of a high frequency filter (three-stage BPF) according to the first embodiment of the present invention. In FIG. 1, 1
1, 12 and 13 are split ring resonators having capacitors 11a to 13a for frequency tuning, 14 and 15 are capacitors for input / output coupling, 16 and 17 are input and output terminals, specifically, coaxial connectors or It is a pin terminal.

As described above, by providing the input and output terminals substantially in the center of the inside of the loop of the split ring resonators 11 to 13, it is possible to realize a compact housing.

FIG. 2 is a plan view of a high frequency filter according to the second embodiment of the present invention. 2 is different from the first embodiment in FIG. 1 in that the coupling capacitors 14 and 15 used for input and output in FIG. 1 are replaced with magnetic coupling loops 21 and 22, respectively. The coupling loops 21 and 22 can also be arranged inside the resonators 11 and 13, and the input / output terminals 16 and 17 can also be provided at the inner substantially central portions of the ring resonators 11 to 13 as in the first embodiment. .

In the above first and second embodiments, the number of BPFs is three and the ring resonator has a square loop shape. However, the number of steps may be any number, and the loop shape may be circular.
Needless to say, it may be rectangular.

 Next, a third embodiment of the present invention will be described.

3 (A) and 3 (B) are a plan view and a side sectional view of a ring resonator which is a main part of a high frequency filter according to a third embodiment of the present invention.

In FIG. 3, reference numeral 31 is a ring resonator having a splitting body, 32 is a coaxial connector, 33 is a central conductor of the coaxial connector 32, and 34 is a metal conductor (which serves as a casing of the device) on which the coaxial connector 32 is mounted. .

According to the above configuration, the ring resonator 31 has the function of a notch filter, but it is possible to have a structure in which the ring resonator 31 and the coaxial connector 32 are coaxially integrated with each other.

As described above, according to the present invention, the ring resonators formed by connecting capacitors to both open ends of the loop-shaped transmission line are arranged so as to be parallel-coupled to each other, and the input or output terminals for high-frequency signals are arranged. By providing the loop resonator inside the transmission line, the filter using the ring resonator can be miniaturized with a simple structure, and its industrial value is extremely large.

[Brief description of drawings]

1 and 2 are plan views of the high-frequency filter according to the first and second embodiments of the present invention, and FIGS. 3A and 3B are schematic views of the high-frequency filter according to the third embodiment of the present invention. FIG. 4 is a plan view and a side sectional view of a ring resonator as a part, and FIG. 4 is a plan view of a conventional high frequency filter. 11 to 13 …… Ring resonator, 14, 15 …… Capacitor, 16,
17 …… Input / output terminals, 21, 22 …… Magnetic field coupling loop.

Claims (1)

(57) [Claims] 1. A ring resonator formed by connecting a capacitance to both open ends of a loop-shaped transmission line is arranged so as to be coupled in parallel with each other, and an input or output terminal for a high frequency signal is provided to the transmission line of the ring resonator. A high-frequency filter characterized by being provided inside the.