JPH0548304A - Band pass filter - Google Patents

Abstract

PURPOSE:To realize the band pass filter in which miniaturization and suppression of a harmonic are attained by using side ends of resonators for input and output and inter-stage coupling and arranging the resonators in straight line. CONSTITUTION:Each of inter-stage resonators 11, 12, 13 is formed to be parallelogrammic or triangular as shown in the figure to couple the interstage resonators by using side ends of the resonators, and in order to arrange them in a straight line, the arrangement of the resonators is devised. A high frequency signal inputted to an input coupling line 14 is coupled sequentially with a 1st stage resonator, a 2nd stage resonator and a 3rd stage resonator by the distribution coupling including electric field and magnetic field coupling, and an output signal with a desired characteristic is obtained form an output coupling line 15. Sufficient coupling is obtained in comparison with the electric field coupling at the end of the lines because the inter-stage coupling adopts the distribution coupling using the resonator side ends, and the band pass filter having a broad band and steep characteristic is realized. Since the shape of the resonators differs from a uniform line, the harmonic passing frequency is controlled to suppress integral multiple frequencies with respect to the fundamental frequency.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a strip and microstrip line bandpass filter suitable for use in the microwave and millimeter wave bands.

[0002]

2. Description of the Related Art Strip and microstrip line filters used in microwave and millimeter wave integrated circuits are composed of open-ended resonant lines because of the fact that a high frequency ground point is not necessary and there is little fluctuation in resonance frequency. Often. Many of these filters use a uniform line as a resonator and use electromagnetic field coupling at the line end or electric field coupling at the line end as the coupling between the input / output and the resonator for ease of design.

The conventional strip and microstrip bandpass filters will be described below.

FIG. 3 shows a conventional bandpass filter utilizing the coupling of the line side ends. In FIG.
Reference numerals 1, 2 and 3 denote uniform line type interstage resonators, and 4 and 5 denote input / output coupled lines utilizing electromagnetic field coupling due to parallel coupling of line side ends.

The operation of the band pass filter configured as described above will be described below. The high-frequency signal input from the input coupling line 4 is coupled to the first-stage resonator 1, the second-stage resonator 2, and the third-stage resonator 3 by distributed coupling at the line side ends, and the desired high-frequency signal is output from the output coupling line 5. A signal with characteristics can be obtained.

FIG. 4 shows a conventional bandpass filter using the coupling of line ends. In FIG.
6, 7 and 8 are uniform line type interstage resonators, and 9 and 10 are
An input / output coupled line using electric field coupling at the end of the line is shown.

The operation of the bandpass filter configured as described above will be described below. The high frequency signal input from the input coupling line 9 is reduced to 1 by the electric field coupling at the line ends.
A signal having desired characteristics can be obtained from the output coupling line 10 by coupling with the stage resonator 6, the second stage resonator 7, and the third stage resonator 8.

[0008]

However, in the case of the above-mentioned conventional structure, a filter utilizing parallel coupling of line side ends cannot be arranged linearly because of the structure, and it is necessary to have a planar spread. However, the shape becomes large. Further, when the line end coupling is used, the arrangement becomes a straight line, so that there is a drawback that the length becomes long. Furthermore, since it is difficult to achieve sufficient coupling by line end coupling, it is difficult to realize a bandpass filter having wideband characteristics.

When these band-pass filters are used as output filters of nonlinear circuits such as oscillators and amplifiers, since a uniform line resonator is used as a resonator, a pass band occurs even at an integral multiple of the desired frequency. .. Therefore, in order to suppress the higher harmonics, there is a drawback that it is necessary to devise a method such as using it in combination with another filter.

The present invention solves the above problems of the prior art, and an object of the present invention is to provide a band pass filter which is small in size and which can control harmonics. ..

[0011]

In order to achieve this object, the band-pass filter of the present invention has an input / output coupling line and an interstage resonator arranged in a straight line, and sufficient inter-resonator coupling can be obtained. In order to achieve parallel coupling using the resonator side ends, a parallelogram or triangular shape resonator is adopted as its constituent element, and the arrangement is devised to achieve the above object. Is.

[0012]

In the band-pass filter having the structure of the present invention, the resonator structure is formed in the shape of a parallelogram or a triangle, whereby the linear arrangement and pattern of the resonator can be reduced.
In addition, since the coupling between the input and output and the resonator is parallel coupling utilizing the side surface of the resonator, sufficient coupling can be achieved and the band can be widened.

Further, by forming the resonator structure into a shape different from that of the uniform line, the spurious resonance frequency can be controlled, and a bandpass filter excellent in suppressing harmonics of an integral multiple is realized.

[0014]

(Embodiment 1) A first embodiment of the present invention will be described below with reference to the drawings.

In FIG. 1, reference numerals 11, 12 and 13 represent parallelogrammic interstage resonators, and 14 and 15 represent input / output coupling lines. Input / output and interstage coupling are distributed coupling using the resonator side end.

The operation of the band pass filter configured as described above will be described below.

The high-frequency signal input from the input coupling line 14 is coupled to the first-stage resonator, the second-stage resonator and the third-stage resonator by distributed coupling accompanied by electric and magnetic field coupling, and is output from the output coupling line 15. , An output signal having desired characteristics can be obtained. The filter has a linear shape and is smaller than the conventional type. In addition, interstage coupling is distributed coupling using the side edges of the resonator, so sufficient coupling can be obtained compared to electric field coupling at the line ends, and a bandpass filter with a wide band and steep characteristics can be realized. ..

In the uniform line resonator, the higher-order resonance frequency occurs at an integer multiple of the fundamental frequency, but in the parallelogram resonator of this embodiment, the higher-order resonance frequency occurs at a frequency lower than the integral multiple of the fundamental frequency. Cause Therefore, even when the filter structure is used, the pass band of the higher-order frequency occurs at a frequency deviated from an integral multiple of the fundamental frequency. Such a characteristic is a desirable characteristic for a bandpass filter used in the output stage of a non-linear circuit that needs to suppress harmonics.

(Second Embodiment) A second embodiment of the present invention will be described below with reference to the drawings.

In FIG. 2, reference numerals 16, 17 and 18 denote interstage resonators having a triangular structure, and 19 and 20 denote input / output coupling lines.

The operation of the bandpass filter configured as described above will be described below.

A high-frequency signal input from the input coupling line 19 is coupled to the first-stage resonator 16, the second-stage resonator 17, and the third-stage resonator 18 by distributed coupling accompanied by electric and magnetic field coupling, and output coupling. An output signal having a desired characteristic is obtained from the line 20. Similar to the first embodiment, the shape is linear and miniaturized. Since interstage coupling is distributed coupling, sufficient coupling can be obtained, and a bandpass filter having a wide band and steep characteristics can be realized.

Even the resonator having the triangular structure of the present embodiment causes high-order resonance at a frequency lower than an integral multiple of the fundamental frequency.
Therefore, even when the filter structure is used, the pass band of the higher-order frequency occurs at a frequency deviated from an integral multiple of the fundamental frequency.

In this embodiment, the number of filter stages is three, but the number of filter stages is not limited to three.

[0025]

As described above, according to the present invention, a parallelogram or triangular structure is adopted as a resonator which is a constituent element of a filter, and a linear arrangement and pattern miniaturization are achieved by devising the arrangement. It is also possible to realize a bandpass filter having excellent performance in terms of wide band and control of high-order passband frequencies.

[Brief description of drawings]

FIG. 1 is a plan view of a bandpass filter according to a first embodiment of the present invention.

FIG. 2 is a plan view of a bandpass filter according to a second embodiment of the present invention.

FIG. 3 is a plan view of a conventional bandpass filter using coupling on the line side end.

FIG. 4 is a plan view of a conventional bandpass filter using line end coupling.

[Explanation of symbols]

 11, 12, 13, 16, 17, 18 Interstage resonator 14, 15, 19, 20 Input / output coupling line

Claims (3)

[Claims] 1. A resonator comprising a plurality of open-ended type strips and a plurality of microstrip line resonators, the resonators are linearly arranged, and input / output and inter-resonator coupling are realized by parallel coupling using side edges of the resonators. A bandpass filter characterized in that 2. The band pass filter according to claim 1, wherein a resonator having a parallelogram structure is used as the resonator. 3. The bandpass filter according to claim 1, wherein a resonator having a triangular structure is used.