JPS63267001A - Polar filter - Google Patents

Abstract

PURPOSE:To attain a small sized and low-cost filter by using at least four resonator components each formed by connecting a capacitor to both open ends of a rectangular or circular pattern of a microstrip line or a TEM mode transmission line whose both ends are opened. CONSTITUTION:Two open ends of a rectangular shaped conductor of a TEM transmission line such as a strip line whose ends are opened in rectangular ring resonators 105-108 are connected respectively by a capacitor. Inter-stage couplings k12, k23, k34 required for realizing the filter are obtained by applying parallel spatial coupling to the resonators 105 and 106, 106 and 107, and 107 and 108 respectively and a coupling k41 is obtained by applying spatial parallel coupling to the resonators 105 and 108 to make the filter polar. Through the existence of the coupling k41 in this way, the filter characteristic has an attenuation pole at the blocking region. Thus, the polar forming of the filter is easily realized without any special additional circuit and the small sized and low-cost filter is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a polarized filter used in high frequency circuits of wireless communication equipment, measuring devices, etc. in high frequency bands above the U I-IF band.

Conventional technology A bandpass filter in a high frequency band is an essential device for high frequency circuits, and many filter structures have been put into practical use, but in order to obtain steep attenuation characteristics with a small number of stages, a polar filter is required. Optimal.

As shown in Japanese Utility Model Publication No. 60-7525, a polarized filter that uses a TEM mode transmission line such as a strip line has resonances that are not adjacent to each other among a plurality of resonators (three or more) that constitute the filter. By coupling the devices together, an attenuation pole is created in the stopband, and auxiliary circuit elements such as strip lines are used to realize this coupling circuit.

Problems to be Solved by the Invention As mentioned above, a polarized filter is a bandpass filter that has a sharp attenuation characteristic with a small number of stages, but when a TEM transmission line type resonator is used, it is necessary to attach These problems include the need for a circuit, the complicated structure of the filter, the large size of the filter, and the complicated and time-consuming adjustment.

In view of the above prior art, the present invention has a simple configuration, miniaturization,
The present invention provides a polarized filter that is cost-reduced.

Means for Solving the Problems The present invention uses at least four resonant elements formed by connecting both open ends of a rectangular or circular pattern made of a microstrip line or a TEM mode transmission line with capacitors connected at both ends. It is something.

According to the above configuration, the present invention provides inter-stage coupling by spatially distributed coupling between the adjacent resonant elements to provide bandpass filter characteristics, and also provides spatially distributed coupling between the resonant elements that are not adjacent to each other. This causes coupling to occur in the filter to have an attenuation pole in the stopband of the filter.

Example First, the basic concept of the present invention will be explained.

Regarding the design of filters using split ring resonators, see Sayo and Makimoto, “Strip line split ring resonators.
``Multi-stage bandpass f-wave device using a ring resonator'' (Proceedings of the 70th Anniversary National Conference of the Institute of Electronics, Information and Communication Engineers (1986) Lecture Proceedings 3-247). The resonator and its coupling circuit will be explained using FIGS. 5 and 6.

In FIG. 5(a), 51 is a rectangular TEM transmission line conductor such as a strip line with an open end, and its two open ends are connected through a capacitor 52. It is known that a resonator having such a structure can be miniaturized and has features such as low loss because there is no high-frequency short-circuit point.

On the other hand, Fig. 5(b) shows the rectangular conductor in Fig. 5(a) made into a circular shape, and the electrical characteristics are exactly the same as those in Fig. 5(a), but the coupling circuit design is Since the degree of freedom increases, the structure becomes easy to realize a polarized filter. 6th
The figure shows the configuration of a coupling circuit for a split IJ resonator. FIG. 6(a) shows two resonators 61
(R,), 62 (R1) are arranged in the same direction and connected spatially in parallel to obtain the degree of connection kl! This is what you are getting. FIG. 6(b) shows two resonators 63 (R1) and 64 (
R,) are placed back to back and connected in parallel to obtain the degree of bonding.

In this way, since coupling is possible using a portion of the transmission line constituting the resonator, the degree of freedom in designing the coupling circuit increases and the configuration of the polarized filter becomes easy.

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

FIG. 1 is a plan view of a polarized filter in a first embodiment of the present invention. In FIG. 1, 101.degree. 102 are input and output terminals, 103. 104 is a coupling capacitor, and 105 to 108 are rectangular ring resonators, which are made of microstrip or strip line. Resonators 105 and 106, 100 and 107
．． 107 and 108 are spatially coupled in parallel to each other to achieve the interstage coupling degree k I! ,
k n , k 34 is obtained. Furthermore, in order to polarize this filter, a resonator 105. 108 are spatially connected in parallel to obtain a degree of connection of 41. In this way, by adding 41 to the degree of connectivity, points 23 and 2 in Figure 2
4, this filter attenuation characteristic has an attenuation pole in the stop band. In addition, in the same figure, the broken line 21
is the characteristic when there is no polarization, that is, when 41 does not exist, and the solid line 22 is the characteristic when it is polarized.

When a ring-shaped resonator is used in this way, it is not necessary to use a special circuit for polarization, and a polarized filter can be easily realized. The attenuation pole can be easily adjusted by adjusting the coupling pressure 41, that is, by changing the spatial positions of the resonators 105 and 108 (the spacing between the parallel coupling parts).

FIG. 3 shows a second embodiment of the invention. In FIG. 3, 101. 102 is an input and output terminal; 103;
104 is a coupling capacitor, and 301 to 306 are circular split ring type resonators. In this embodiment, a gap capacitor using an open end of a line is used as a resonator capacitor. The coupling as a filter is the resonator 301
and 302. 302 and 303° 303 and 304. 30
4 and 305. 305 and 306, each with a degree of coupling k +! , k n , k 34 ,
Obtain k 45 and k u. On the other hand, the coupling of the polarized drums is performed by the resonators 301 and 306, and 302 and 305, respectively, to obtain the coupling degree kllkls.

As described above, the circular split ring type resonator 30
1 to 306, it is difficult to achieve a filter with a wide pass band because the coupling between the resonators cannot be established compared to a rectangular resonator, but it is difficult to realize a filter with a wide passband, but it is possible to achieve a polarized filter because the degree of freedom in realizing coupling is high. has features that make it easy to design.

FIG. 4 shows a third embodiment of the invention. In FIG. 3, 101. 102 is an input and output terminal; 103;
104 is an input/output coupling capacitor, and 401 to 405 are circular split ring type resonators.

Although FIGS. 1 and 3 show an embodiment in which the number of resonators is an even number, using circular ring-shaped resonators 401 to 405 makes it easier to design the coupling circuit. As shown in the figure, it is easy to polarize filters in odd number stages (three or more).

Effects of the Invention As described above, according to the present invention, polarization of a filter can be easily realized without using a special additional circuit, and miniaturization and cost reduction can be expected, and the engineering value thereof is extremely large.

[Brief explanation of the drawing]

1 is a plan view of a polarized filter according to a first embodiment of the present invention, FIG. 2 is a characteristic diagram showing the frequency response of the same polarized filter, and FIGS. 3 and 4 are a plan view of a polarized filter according to a first embodiment of the present invention. ．． A plan view of a polarized filter in the third embodiment, and FIGS. 5 and 6 are plan views of a split ring type resonator illustrating the concept of the present invention. 101, 102...input and output terminals, 103
．． 104...Coupling capacitor, 106-108.
301~306°401~405...Split ring type resonator. Name of agent: Patent attorney Satoshi Nakao and one other personjI1
Figure 2: Mashinshiki 3: Figure 4/l) 1! Figure 5 j86

Claims (4)

[Claims] (1) Microstrip line or T with both ends open
A plurality of resonant elements formed by connecting both open ends of a rectangular or circular pattern made of an EM mode transmission line with a capacitor are used, and interstage coupling is provided between adjacent resonant elements by spatially distributed coupling. What is claimed is: 1. A polarized filter characterized in that the resonant elements that are not adjacent to each other have a spatially distributed coupling between the resonant elements and have an attenuation pole in the stop band of the filter. (2) Consisting of 2n (where n is an integer greater than or equal to 2) resonant elements, the interstage coupling of the resonant elements that realizes band-pass filter characteristics is between j and j+1 (where j=1 to 2n-1). )
The coupling of the resonant element k is performed, and the polarized coupling is k
2. The polarized filter according to claim 1, which utilizes coupling between the 2n+1-k (k=1 to n-1)th resonant elements. (3) Consisting of (2n+1) (where n is an integer greater than or equal to 2) resonant elements, the interstage coupling of the resonant elements that realizes band-pass filter characteristics is the j and j+1 (j=1 to 2n)th The polarized coupling is performed using the resonant element k and 2n+.
2. The polarized filter according to claim 1, which utilizes coupling between 1-k (k=1 to n) resonant elements. (4) The polarized filter according to claim 1, wherein the coupling circuit of the filter using a rectangular split-hung resonator is realized by parallel coupling lines between resonant elements.