JPS5821845B2 - Yuukiyokugatataiikitsuukalohaki - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a bandpass filter for extremely high frequency waves having an attenuation pole in the stopband of its attenuation characteristics.

Conventionally, only non-polar linear phase bandpass filters have been designed in which the stop band attenuation characteristic increases monotonically.

However, IEEE Transactions on
Microwave Theory and Technics Mchichi Volume 128, /166. June 1970 Issue 29
Pages 0-301 (IEEE Transactions
On Microwave Theory and T
echniques Vol MTT-18, yi6.
6, June 1970), or IEE Transactions on Mitalowave Theory and Tetanitas Mcheechee Volume 18, /I66
．． June 1970 issue, pages 308-313 (IEEE T
transactions On Microwave
The e-ory and Techniques V
ol MTT-18, 46, June 1970), it is clear that theoretically there are two types: a non-polar type and a polar type having an attenuation pole in the stop band.

In a linear phase bandpass filter, for example, as shown in FIG. 1, rectangular waveguides 1a and 1b are arranged with one side in contact with each other. Body resonators 1.2, 3, 4 and 1'.

2', 3', 4' are formed in sequence, and these resonators 1, 2, 3, 4 and 1', 2', 3', 4
' are coupling elements 5, 6, 7, 8 and 9, 10, 1 respectively
A coupling path (hereinafter referred to as the main coupling path) in which 1° 12 are sequentially valved and coupled, and cavity resonators 2, 2' and 3° 3' and 4, 4' are connected to coupling elements 13, 14, 15, respectively. It has a connection path (hereinafter referred to as an additional connection path 30) which connects through the connection path.

Now, let's talk about the design method of a conventional linear phase bandpass filter: In the case of a non-polar type, if the main coupling path is inductive coupling, all additional coupling paths are inductive coupling,
Coupling elements 5, 6, 7, 8, 9 as shown in FIG.
, 10, 11, and 12 are inductive round bars, respectively, and the coupling elements 13, 14, 15 are inductive coupling holes 13, 14.
, 15.

Theoretically, in the case of a polar type, if the main coupling path is inductive coupling, the first few additional coupling paths, including the one between cavity resonators 1.1 in Figure 1, are capacitive coupling. , the remaining additional coupling paths must be inductive.

Therefore, conventionally, by eliminating the first few capacitive coupling paths that cause the polarized attenuation characteristic, that is, by connecting them with conductive plates so as not to cause any coupling, it is possible to eliminate the originally polarized type. It can be said that it was used as a non-polar type.

In other words, the filter shown in Fig. 1 is theoretically a polar type, and when there is only one capacitive additional coupling path, the capacitive additional coupling path should connect between the first stage resonators 1 and 1'. was blocked, making it a non-polar linear phase bandpass filter.

The reason for doing this is that there was no suitable additional coupling element to provide capacitive additional coupling, and that even if the circuit was made non-polar by the operation described above, it would not disturb the matching conditions of the circuit too much. .

Therefore, if an effective capacitive additive coupling element is available, a polarized linear phase bandpass filter can be realized.

The need for such capacitive additional coupling elements is not limited to polarized linear phase bandpass filters.

Figure 2 shows IEE Transactions on Microwave Theory and Tetanics.
Mchichi vol. 14, /I66. June 1966 issue 29
Pages 5-296 (IEEE Transactions
On Microwave Theory aI] II
Techniques VolMTT-14, 46, J
This is an equivalent circuit of a polarized bandpass filter shown in 1966).

In the same figure, cavity resonators 1 and 2°3 are tuned respectively.
．． 4 is sequentially connected to the inductive coupling element 12. 23. 34 to form a main coupling path.

According to this document, for example, a maximum amplitude flat bandpass filter is formed with only the main coupling path, and in that state, a capacitive additional coupling element 14 is installed between the cavity resonators 1 and 4' to block the filter. produces an attenuation pole in the region.

Figure 2 shows a four-stage resonator, but in the case of an even number of stages of four or more stages, a capacitive additional coupling element is installed between the first and last stage of the filter to achieve polarized attenuation characteristics. obtain.

In order to distinguish this polarized bandpass filter from a polarized linear phase bandpass filter, it is tentatively named a general polarized bandpass filter.

In designing this film-type polarized bandpass filter, an effective capacitive additional coupling element is also required.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a polarized linear-phase bandpass filter and a membrane-type polarized bandpass filter equipped with a suitably effective capacitive additive coupling element for producing an attenuation pole in the stopband. It's about doing.

The present invention provides n cascade-connected cavity resonators 11.2, 3.
. . . n, and n cascaded cavity resonators 1' in which two adjacent ones are similarly coupled to each other by an inductive coupling element.
t2'$3't...n' are provided, and the cavity resonator 1
and between 1st stage, 2nd and 2'... (k-1) and (k-1
) are capacitively coupled by open-ended type 1 LC resonators.

In these open-ended LC resonators, an inductive coupling hole is formed in the common wall between the resonators to be coupled to each other, and one end of a conductor rod is connected and inserted into this coupling hole to form an LC resonator. Selected for the capacitive region of resonance characteristics.

Further, between the cavity resonators, . . . (n-1) and (n-1)', n and n' are coupled to each other through inductive coupling holes, respectively.

Alternatively, the cavities 1 and 1' at one end of the two cascade-connected cavity resonators are capacitively coupled by the open-ended LC1 resonator, and the cavities n and n' at the other end are capacitively coupled. They are bound at the inductive binding hole, and the intermediate portion between them is left unbound.

FIG. 4 shows a polarized linear phase bandpass filter according to the present invention, and parts in FIG. 4 that correspond to those in FIG. 1 are given the same reference numerals.

In this embodiment, an open-ended LC resonator 30 is provided as a capacitive coupling element between the resonators 1 and 1'.

As shown in FIG.
8 is formed, and a conductor rod 19 extends from the center of one end in the vertical direction (electric field direction) toward the other end.

If the length e of the conductor rod 19 is zero, the cavity resonators 1 and 1' in FIG. By increasing the length of , the electric field component is excited, forming an open-ended LC resonator.

Therefore, the length r of the cavity resonators 1 and 1' is sufficiently short,
If the resonant frequency of the open-ended LC resonator 30 is in a frequency range that is very high compared to the center frequency of the bandpass filter, inductive additive coupling will occur, but the length of e will be increased to If the resonant frequency of the open type LC resonator 30 is in a very low frequency band exceeding the center frequency of the bandpass filter, capacitive additive coupling is achieved.

The present invention realizes a polarized linear phase bandpass filter by capacitive addition coupling using the capacitive region of the open-ended LC resonator 30.

Further, in FIG. 4, the electrical length φ and θk (k=1 to 4) indicate locations where additional coupling holes are provided, and have values determined by circuit synthesis.

According to the capacitive additional coupling element, which is a feature of the present invention, it is possible to intensively couple φ to a predetermined location determined by θ.

If a capacitive window, which is generally used as a capacitive coupling element, is used as a capacitive addition coupling element, it is necessary to provide an elongated coupling hole 20 in the tube axis direction as shown in FIG. Inductive round rods 5, 6, 9, 10 for coupling with adjacent resonators in the tube axis direction of each resonator 1, 1' including the coupling hole 20, which prevents capacitive additional coupling from being concentrated at a predetermined location. This causes problems such as the amount of additional coupling being distorted due to the higher-order modes excited by this, resulting in the disadvantage that design and adjustment are extremely difficult.

On the other hand, according to the present invention, at least the resonator 1-1'
Since the resonator 30 is provided in the center of the resonator 1-1' in the tube axis direction, the resonator 30 is separated from the other resonators 2°2, and therefore the coupling characteristics of the resonator 30 are changed. However, the characteristics of the other resonators 2-2' do not change.

This provides the advantage of easy design and adjustment.

゛ Fig. 7 shows an example of the characteristics of the polarized linear phase bandpass filter according to the present invention, where curve 16 is the attenuation characteristic and curve 17 is the attenuation characteristic.
is the delay characteristic, with frequencies f and f on both sides of the stopband
A pole centered at pt p2 occurs, and the cutoff frequency becomes sharp.

In Fig. 4, the capacitive additional coupling element formed by the resonator 30 and the inductive coupling hole 15 between the cavity resonators 4 and 4' are left as they are, and the other inductive coupling holes 13 and 14 are blocked by a conductor plate. However, if no coupling is made, this becomes an example of the configuration of a general polarized bandpass filter in which six resonant circuits are inserted between resonant circuits 1 and 4 at both ends in the equivalent circuit shown in Figure 2. .

Although the above description has been made using a rectangular waveguide cavity type as an example, the present invention is not limited to a rectangular waveguide cavity resonator, and any cavity resonator that forms an inductive coupling may be used.

Further, the inductive round bar may be any other type as long as it is an inductive/coupling element.

If a mechanism is provided that can vary the length of the conductor rod 5 in FIG. 5, the amount of capacitive additional coupling can be varied, and the frequency 'PI, fP2 at which the attenuation pole shown in FIG. 7 occurs is set relative to the center frequency. Since the frequency selectivity can be finely adjusted, it is very easy to satisfy electrical short circuits.

As explained above, the present invention makes it easy to realize polarized linear and phase bandpass filters and membrane-type polarized bandpass filters.

When designing a filter, for example, when a bandpass filter with extremely high frequency selectivity is required, the only effective method for a non-polar type is to increase the number of stages, which results in an increase in passband insertion loss.
Add.

However, according to the polarized bandpass filter according to the present invention, the number of stages required to obtain the required frequency selectivity may be reduced, and loss can be reduced.

Furthermore, filter design and manufacture become easier, which is of great practical benefit.

[Brief explanation of the drawing]

Figure 1 is a perspective view of a conventional linear phase bandpass filter, Figure 2 is an equivalent circuit diagram of a general polarized bandpass filter, and Figure 3 is the characteristic of the filter shown in Figure 1. 4 is a perspective view of a polarized linear phase bandpass filter according to the present invention, FIG. 5 is an enlarged view of the capacitive additional coupling part in FIG. 4, and FIG. 6 is a capacitive coupling element as an additional coupling element. FIG. 7 is a perspective view of the vicinity of the additional joint in the case where a magnetic window is used, and FIG. 7 is a characteristic curve diagram of the filter of FIG. 4. 1.2, 3, 4, 1', 2', 3', 4': Cavity resonator, 5, 6, 7, 8, 9, 10, 11, 12: Inductive round bar, 13, 14, 15: Inductive coupling hole, 30: Open-ended LC resonator.

Claims (1)

[Scope of Claims] 1 person n (n is a positive integer of 3 or more) cascade-connected cavity resonators 1, 2, 3, . ...n. B. n cascaded cavity resonators 1' in which two adjacent ones are coupled to each other by an inductive coupling element. 2', 3', . An open-ended LC resonator in which a conductor rod is inserted into an inductive coupling hole provided approximately at the center of the cavity resonators 1 and 1' to capacitively couple the cavity resonators 1 and 1'; A polarized bandpass filter.