JPS6031401B2 - Interdigital bandpass filter - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an interdigital band pass wave generator which is provided with a capacitive indirect coupling circuit and whose attenuation castle is polarized.

An example of the structure of a conventional guided M-type interdigital band wave device is shown in FIGS. 1A and 1B.

Here, 1 to 6 are resonant elements arranged in a row in a 6-stage configuration, 7 is an outer box (shield) of a band-pass wave device, To and Tn+,
are the input and output transformers, respectively. In this interdigital type band castle passing wave device, the passage castle has a Wagner characteristic or a Chebyshev characteristic, and the attenuation castle has a non-polar type. That is, the transmission characteristic is as shown in FIG. 2, and the rise characteristic of the attenuation castle is gradual.

In addition, the example in Figure 1 shows a 6-stage (therefore 6th order) interdigital type wave device that passes through the band castle, but if you try to make the rise characteristic (damping castle characteristic) steeper, the band castle It is necessary to increase the order (ie, the number of stages) of the waveform passing through. However, as the number of orders of the waves passing through Obijo increases,
'11 There were disadvantages such as increased insertion loss and difficulty in making fine adjustments as the size increased. In addition, some conventional techniques use probes as capacitive coupling parts to polarize the attenuation castle, but with this coupling method it is not possible to obtain minute capacitive coupling values; As a result, there were drawbacks such as difficulty in obtaining a large amount of attenuation (for example, 8 MB or more) in the attenuation frequency band.

SUMMARY OF THE INVENTION In view of the above-mentioned points, it is an object of the present invention to provide a compact interdigital band pass filter which has improved filtering characteristics and facilitates adjustment. In order to achieve such an object, the present invention includes a plurality of resonant elements arranged so that the installation polarity is sequentially reversed, and a main coupling circuit of the resonant elements by dividing the plurality of resonant elements into predetermined spatial regions. and a positioning plate that partitions the inside of the electromagnetic shielding cone so as to form an electromagnetic shield, and the 4n (n=1, 2, 3...) resonant elements are separated from each other so as to form a loose electric field coupling between the pair of resonant elements. A capacitive indirect coupling hole is provided in the partition plate.

Hereinafter, the present invention will be explained in detail based on Examples.

Figures 3A and 3B illustrate one embodiment of the invention.

Here, 11 to 16 are resonant elements similar to those shown in FIG. 1, To and Tn are also input transformers and output transformers similar to those shown in FIG. 1, and 17 is resonant elements 11 and 12 arranged in a row.
, 13 and a partition plate arranged between 16, 15, 14,
Reference numeral 18 designates a circular coupling hole for realizing a loose electric field coupling described later between the resonant elements 11 and 16, and 19 designates an outer box (an electromagnetic shield cliff). In addition, the resonant elements 11, 12, 12
13, 13 and 14, 14 and 15, and 15 and 16, a capacitive indirect coupling circuit is formed between the resonant elements 11 and 16 via a circular coupling hole 18.

Generally, it is well known that polarization can be achieved by using a coupling probe, a coupling plate, or the like as a capacitive coupling circuit between the resonant element 11 and the resonant element 16.

However, when a coupling probe or a coupling plate is used, the coupling becomes too dense in high frequency bands, and the required amount of attenuation may not be obtained. Therefore, in this embodiment, the circular capacitive coupling hole 1
By using 8, it is possible to make the electric field coupling sparse. Next, the function of the capacitive coupling hole 18 described above will be explained.

It is generally known that circular coupling holes act as magnetic coupling elements and not as capacitive coupling elements.

On the other hand, in the interdigital type wave transmitter shown in FIGS. 3A and 3B, an electric field distribution as shown in FIG. 4 occurs between the resonant elements 11 and 16. At this time, the electric field distribution between the resonant elements 11 and 12 and the resonant element 15
The amount of electric field distribution between and 16 will be approximately equal. and,
Between the resonant element 11 and the resonant element 16 shown in FIG.
The directions of the leakage electric field vectors k match. Therefore, the resonance elements 11 and 16 are coupled by the leakage electric field Eck, resulting in capacitive coupling (loose electric field coupling). Since the coupling mode between adjacent resonant elements is capacitive coupling, the phase difference is 900 degrees.

Therefore, if we look at the main coupling circuit, there are four resonant elements 12, 13, 14 between the resonant element 11 and the resonant element 16.
, 15, the phase difference between them is 900×5=
900×4900=900.

In addition, by forming indirect capacitive coupling using the circular coupling hole 18 (see FIG. 4), the resonant element 11 and the resonant element 1
6 is in reverse phase.

Therefore, the phase will be 90 degrees different (at the resonant frequency) from the signal (power) that has propagated through the main coupling circuit, but its amplitude will have little effect as the main coupling > indirect coupling near the resonance frequency. I never receive it.

On the other hand, as for the phase characteristics of each resonant circuit, it is well known that the phase changes continuously as the frequency decreases from the resonant frequency. In addition, since the phase constant of the indirect coupling circuit has no relation to frequency, the respective powers cancel each other out at a point where the phase difference is 1800 degrees (90 degrees of phase difference compared to the resonant frequency), and a pole is generated. become. At this time, in order to obtain a steep filter characteristic and a large amount of attenuation at the same time, it is necessary to reduce the amount of power of the negative phase signal leaking through the indirect coupling circuit. To this end, we need to determine the amplitude value at a frequency whose phase differs by 90° from the resonant frequency (a very small value in a band-pass wave transmitter with steep characteristics and large attenuation), and the It is necessary to make the obtained signal amplitude value (power) approximately equal. In this embodiment, a six-stage band-passing transducer has been described, but the present invention can be applied to cases where the number of stages (order) is increased or decreased.

For example, when configuring a wave device that passes through one disguised obi castle,
It is possible to provide indirect capacitive coupling via four or eight resonant elements. The attenuation range of the conventional interdigital band pass wave device had a damping characteristic as shown in Fig. 2, and had the disadvantage of exhibiting a gradual attenuation characteristic, but according to the present invention, the attenuation range as shown in Fig. 5 As shown in A and B, steep attenuation characteristics can be obtained by polarizing the attenuation castle.

Here, FIG. 5A shows a single pole case in which resonant elements 11 and 16 are capacitively coupled, and FIG. 5B shows a loop between resonant elements 12 and 15 in addition to such capacitive coupling. The case of a double pole with a connection is shown. As explained above, according to the interdigital type wave device passing through the band of the present invention, it is possible to realize a wave device passing through the band with a steep rise characteristic (attenuation characteristic). Since there is no need to increase the number of stages of resonant elements as in the above, the device does not become larger and adjustment does not become difficult.

In this way, the interdigital wave transmitter of the present invention can be used in radio equipment to remove unnecessary waves, and can also be applied to antenna duplexers, etc., to provide a duplexer with large inter-terminal coupling attenuation and low insertion loss. It is possible to obtain special effects such as being able to realize the following.

[Brief explanation of drawings]

FIGS. 1A and 1B are a plan view and a sectional view showing an example of the structure of a corrugator that passes through an interdigital type belt of a subordinate, and FIGS.
The figure is a characteristic curve diagram showing an example of general transmission characteristics of the bandpass filter shown in Figures 1A and B, and Figures 3A and B are diagrams showing the configuration of the interdigital bandpass filter of the present invention. A plan view and a sectional view showing one embodiment, FIG. 4 is a diagram for explaining the coupling state of the resonant element shown in FIG. 3A, and FIGS. 5A and B show the transmission characteristics obtained by the present invention. It is a characteristic curve diagram showing two examples. 1-6, 11-16... Resonance element, 7, 19.
...Outer box (shield), 17...Partition plate, 18...Circular coupling hole, 19...Outer box (shield), To... ...input transformer, TM,
...Output transformer, Eck...Leakage electric field. Figure 1 Figure 3 Figure 2 Figure 4 Figure 5

Claims (1)

[Claims] 1. A plurality of resonant elements arranged so that the installation polarity is sequentially reversed, and a partition that divides the plurality of resonant elements into predetermined spatial regions to form a main coupling circuit of the resonant elements within the electromagnetic shielding case. board, 4n pieces (n=1,
2, 3...), wherein the interdigital type band-pass filter is characterized in that a capacitive indirect coupling hole is provided in the partition plate so as to create a loose electric field coupling between a pair of the resonant elements with the resonant elements separated from each other. .