JPS59147501A - Band-pass filter - Google Patents

Abstract

PURPOSE:To attain circuit integration by providing a slot line on the surface on the other side of a dielectric substrate where a strip line resonator is formed and connecting the resonator by the line with crossing so as to improve the selectivity of an attenuation pole at the outside of the pass band. CONSTITUTION:A band-pass filter for a microwave band is constituted by forming plural microstrip line resonator 2 on the surface of one side of the dielectric substrate 1 and providing the slot line 3 on the rear side of the dielectric substrate 1. The plural resonators 2 are connected by the slot line 3 in crossing. The selective characteristic of a waveform (a) is obtained at a frequency where the amplitude of coupling between the strip line and the slot line 3 is equal and the phase is opposite. Further, the circuit integration of the filter is made easy by changing the degree of coupling between the resonator 2 and the slot line 3, the length of the slot line 3 and the position of the attenuation pole.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a microwave band band pass filter (BPF), and is particularly suitable for MIC implementation. The present invention relates to a BPF with a planar structure using strip lines.

Conventionally, in frequency bands up to about 100MHz.

BPFs with lumped constants are mainly used, and many polarized BPFs having attenuation poles outside the two passbands are in practical use. However, although polarized BPFs have been realized in the microwave band (frequency bands above about IGHz), they require waveguides and cavities, and have poor productivity.
I can't say the price is cheap either.

On the other hand, a stripline BPF with a planar structure using striplines is in practical use as a BPF for mass production, but this has the disadvantage that the required selectivity cannot be obtained because it has an attenuation pole. .

The object of the present invention is to be suitable for mass production. It is an object of the present invention to provide a bandpass filter for a microwave band, which has a planar structure using strip lines and has good selectivity due to attenuation poles outside the passband.

bandpass filter (for example, ParallelC
Oupled Line BPF and Interdigital B
PF, CombLine BPF, etc.), a slot line is provided on the other surface of the dielectric substrate, and a plurality of the resonators are connected by the slot line that intersects and couples with the resonators. A pass filter is obtained.

Next, as an example of the present invention, a strip line type BPF
Parallel Cou, which is commonly used as
An example using pled Microstrip Line BPF will be described.

Figure 1 shows the conventional Parallel Coupled M
In the example of the icrostripLine BPF, on the upper surface of the dielectric substrate 1, a plurality of microstrip line resonators 2 of approximately half wavelength are arranged in parallel so as to be coupled to each other.
The entire back surface of the dielectric substrate 1 is made of metal and forms a ground plane.

FIG. 2 shows an embodiment of the present invention, in which the parallel
el Coupled Microslip Lin
e The structure is such that a plurality of microstrip line resonators 2 constituting the BPF are coupled by a slot line 3 provided on the back surface of a dielectric substrate. The slot lines 3 are crossed with each other in order to be coupled to the microstrip line resonator 2. The slot line 3 is formed by removing a predetermined portion of the conductor provided on the entire back surface of the dielectric substrate 1 in the thickness direction until the dielectric substrate 1 is exposed.

If there is no coupling by the slot line 3 on the back surface, the device operates as a BPF due to the coupling between the two microstrip line resonators 2, as is well known.

According to this embodiment, when the slot line 3 is provided on the back surface, the slot line 3
This will result in coupling between the resonators 2 that intersect with .

As a result 1, in this embodiment, (1) At a frequency where the coupling amount on the IJ tube line side and the coupling amount on the slot line side are equal in amplitude and opposite in phase, 1 as shown in Fig. 3(a).
This produces an attenuation pole in the selectivity characteristic. Also.

By changing the degree of coupling between the strip line resonator 2 and the slot line 3 and the length of the slot line 3, the position of the attenuation pole can be changed.

Note that FIG. 3(b) shows the characteristics of the conventional BPF shown in FIG.

As explained above, according to the present invention, a bandpass filter for a microwave band having good selectivity due to attenuation poles outside the passband is suitable for integration into an IC.

) It can be realized with a planar structure using IJ horn lines. In addition, in the present invention, (1) Since the IJ tubular line or the slot line is used, a large number of bandpass filters can be produced inexpensively and without variation in characteristics by methods such as photoetching, and is suitable for mass production. There is also this effect.

The above description describes the present invention as a Parallel Coup'l
ed The case where the present invention is applied to LineBPF has been described, but similarly, the above embodiment describes the case where one set of strip line resonators is coupled by one slot line, but the present invention is not limited to this. Of course, this also includes a case where two or more sets of stripline resonators are coupled by a plurality of slot lines.

Remaining days below

[Brief explanation of the drawing]

Figure 1 shows the conventional Parallel Coupled L
FIG. 2 is a perspective view showing a BPF according to an embodiment of the present invention, and FIG. 3 is a diagram showing frequency-attenuation characteristics of the BPF shown in FIGS. 1 and 2. be. ■...Dielectric substrate, 2...Microstrip line resonator, 3...Slot line. Figure 1 Figure 2 Figure 3-

Claims (1)

Claims: In a bandpass filter configured with stripline resonators, a slot line is provided on the other surface of the dielectric substrate, and a slot line is provided between the plurality of resonators. A bandpass filter, characterized in that it is connected to these through the slot line that crosses and couples them.