JPH0433161B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to a high frequency filter, and more particularly to a high frequency filter having an attenuation pole in an attenuation band.

<Prior art> Conventionally, a high frequency filter using a distributed constant resonant element and having an attenuation pole A in the attenuation band as shown in FIG. 7 has coaxial resonators b1 and b2 and a capacitor b.
The high frequency filter shown in FIG. 5 is a combination of a bandpass filter B composed of elements 3 to b5 and a trap element C composed of a coaxial resonator C1 and a capacitor c2, or a coaxial resonator d1 and a capacitor d2. A trap element D configured by connecting in series and a capacitor E connected in parallel with the trap element D.
There are asymmetric traps such as the one shown in FIG.

<Problems to be solved by the invention> However, since such conventional high frequency filters use independent coaxial resonators,
The number of parts that make up the high frequency filter increases,
The disadvantage is that the manufacturing cost is high.

<Means for Solving the Problems> In order to solve these problems, the high frequency filter according to the present invention includes a dielectric block, and an outer conductor is formed on the outer peripheral surface of the dielectric block. In addition, inner conductors are formed on the inner peripheral surfaces of the plurality of through holes formed in the dielectric block, and adjacent inner conductors are connected via reactances for forming attenuation poles.

In addition, without using a single capacitor 7,
A capacitor may be realized by providing capacitor electrode films spaced apart from each other on the surface of the dielectric block 2, each connected to the connection terminals 8 ₁ and 8 ₂ . In other words, the dielectric block 2 itself is used as a dielectric for a capacitor.

<Example> Hereinafter, an example of the present invention will be described in detail with reference to the drawings. FIG. 1 is a partially cutaway perspective view of an embodiment of the present invention, and FIG. 2 is an equivalent circuit diagram thereof. The high frequency filter 1 of this embodiment includes a rectangular parallelepiped dielectric block 2 made of ceramic, and the dielectric block 2 includes a plurality of (two in this embodiment) dielectric blocks 2 as shown in FIG. Circular through holes 3 ₁ and 3 ₂ are formed, and an outer conductor 4 is formed on the outer peripheral surface of the through holes 3 1 , 3 2 . Furthermore, each through hole 3 ₁ , 3 ₂
Inner conductors 5 ₁ and 5 ₂ are respectively formed on the inner surface of the through hole, and an electrode 6 that short-circuits the outer conductor 4 and the inner conductors 5 ₁ and 5 ₂ is formed on one opening side end surface (bottom surface) of the through hole. is formed, and the other opening side end surface (top surface)
is an open end surface in which the surface of the dielectric block 2 is exposed.

In the high frequency filter 1 of this embodiment, _as shown in FIG.
Connecting terminals 8 ₁ and 8 ₂ are respectively fitted to 3 ₂ , and a capacitor 7 is connected between both connecting terminals 8 ₁ and 8 ₂ by soldering or the like. That is, the adjacent inner conductors 3 ₁ and 3 ₂ are connected via the capacitor 7 that functions as a reactance for forming an attenuation pole. Further, both connection terminals 8 ₁ and 8 ₂ are connected to the coaxial cable 1 via coupling capacitors 9 ₁ and 9 ₂ .
They are connected to the center conductors of 0 ₁ and 10 ₂ respectively. The outer conductors of the coaxial cables 10 ₁ and 10 ₂ are connected to the outer conductor 4 of the dielectric block 2, respectively.

By connecting the adjacent inner conductors 3 ₁ and 3 ₂ via the capacitor 7 in this manner, an equivalent circuit as shown in FIG. 2 is constructed. Here, in the state shown in FIG. 3, if the characteristic admittance of each resonant element in the even and odd modes is Even and Yodd, the electrical angle is θ, and the capacitance of the capacitor 7 is c,
Yodd>Yeven, and element 1 in Fig. 2
The impedance and capacitance reactance of 1 ₃ and capacitor 7 are respectively j・(2tanθ)/
(Yodd−Yeven), −j・(1/ωc). Note that the impedance of both elements 11 ₁ and 11 ₂ is j·(tanθ/Yeven).

Therefore, by appropriately selecting Yeven, Yodd, and the capacitance c of the capacitor 7, it is possible to form a trap at an arbitrary frequency position. In this embodiment, since the inner conductors 3 ₁ and 3 ₂ are connected via the capacitor 7, the attenuation peak is on the lower frequency side than the passing frequency, as shown in FIG.
It is possible to form A′.

In this way, according to the present invention, a high frequency filter having an attenuation pole in the attenuation band can be obtained using a single dielectric block 2, so the number of components constituting the high frequency filter can be reduced compared to the conventional example. This makes it possible to reduce manufacturing costs.

In the above embodiment, the capacitor 7 is used as the reactance for forming the attenuation pole, but
The present invention is not limited to this, and for example, a coil can also be used as the reactance for forming an attenuation pole. When a coil is used, its dielectric reactance is jωL, and an attenuation pole is formed on the higher frequency side than the pass frequency. L is the inductance of the coil.

<Effects of the Invention> As described above, according to the present invention, an outer conductor is formed on the outer peripheral surface of the dielectric block, and an inner conductor is formed on the inner peripheral surface of the plurality of through holes formed in the dielectric block. While forming a conductor, adjacent inner conductors are connected via a reactance to form an attenuation pole, reducing the number of parts that make up a high frequency filter with a pole in the attenuation region compared to conventional examples, reducing manufacturing costs. becomes possible.

[Brief explanation of drawings]

FIG. 1 is a partially cutaway perspective view of an embodiment of the present invention;
2 is an equivalent circuit diagram, FIG. 3 is a vertical cross-sectional view of the dielectric block shown in FIG. 1, FIG. 4 is a characteristic diagram showing the relationship between frequency and gain of the embodiment shown in FIG. 1, and FIG. 6 is a circuit diagram of a conventional example, FIG. 6 is a circuit diagram of another conventional example, and FIG. 7 is a characteristic diagram showing the relationship between frequency and gain of the conventional example. 2...Dielectric block, 3 ₁ , 3 ₂ ... Through hole, 4...
Outer conductor, 5 ₁ , 5 ₂ ...inner conductor, 7... capacitor.

Claims (1)

[Claims] 1 A dielectric block is provided, an outer conductor is formed on the outer peripheral surface of the dielectric block, and an inner conductor is formed on the inner peripheral surface of a plurality of through holes formed in the dielectric block. , a high frequency filter characterized in that adjacent inner conductors are connected via a reactance for forming an attenuation pole.