JP2587880B2 - Dielectric low-pass filter - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a dielectric low-pass filter in which a coaxial dielectric resonator is combined, and more particularly, to a circuit configuration of the dielectric resonator which defines a pass area of the dielectric filter. , A dielectric low-pass filter for defining an attenuation pole.

[0002]

2. Description of the Related Art Generally, a low-pass filter having a basic configuration as shown in FIG. 5 is known. This is obtained by grounding reactances L ₁ , L _2, ... Arranged in series via capacitances C ₁ , C ₂ ,. As described above, when the frequency band of the filter is set using the reactance, due to the structure of the coil,
There is considerable variation in the stray capacitance held by the coil. This has little effect when the band frequency of the filter is low, but has a large effect on the position of the attenuation pole to be set when the frequency is high. For example, Hollow 3MHZ - when configuring pass filter, as shown in FIG. 6, L ₁
= 4 μH, L ₂ = 5 μH, C ₁ = 500 pF, C ₂ = 1
When 000pF and C ₃ = 600pF are set,
Since the stray capacitance of the coil is about 0.5 pF, for example, the influence on the capacitor C ₁ which is about one-thousandth. However, when a low pass filter of ₁ GHZ is constructed, as shown in FIG. 7, L ₁ = 0.01 μH, L _1
2 = 0.01 μH, C ₁ = ₂ pF, C ₂ = 3 pF, C ₃
= If set to 2.5 pF, typically the stray capacitance of the coil is the same as defined above, because of the order of 0.5 pF, for example, influence on the capacitor C ₁ becomes about 1/4. Therefore, when the stray capacitance greatly varies, the attenuation characteristics at a required cutoff frequency cannot be obtained unless the coils and capacitors are adjusted to a considerable width, and the adjustment is complicated and difficult.

[0003]

In order to construct a low-pass filter in a high frequency band, a coaxial dielectric resonator using a dielectric having a high dielectric constant is used in place of the coil. was suggested. The coaxial dielectric resonator,
A dielectric is filled between the inner conductor and the outer conductor, and a plurality of the conductors are arranged or arranged integrally using a common outer conductor. Unlike the coil, the structure is relatively stable. Maintains stray capacitance. But even in this case,
When a low-pass filter is formed, the variation in stray capacitance has a large effect on the capacitance. Therefore, generally, the outer conductor is used with being grounded.

[0004]

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances. In the case where the coaxial dielectric resonator is adjusted to obtain an attenuation characteristic at a required cutoff frequency, the coaxial dielectric resonator is used. By grounding the capacitance that actively includes the stray capacitance of the outer conductor of the device, the passband can be uniquely adjusted at this part, and the attenuation range is set to the resonance frequency of the dielectric resonator. It is intended to provide a body low-pass filter.

[0005]

According to the present invention, a plurality of quarter-wavelength coaxial dielectric resonators each having a dielectric filled between an inner conductor and an outer conductor are arranged. 1/4 of
The coaxial dielectric resonator of the wavelength type has the axial end of the inner conductor of one dielectric resonator and the axial end of the inner conductor of the other dielectric resonator which are connected between adjacent ones. A dielectric low-pass filter is provided, wherein the plurality of quarter-wavelength coaxial dielectric resonators are coupled in series, and each of the plurality of quarter-wave coaxial dielectric resonators is grounded via a capacitance.

[0006]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be specifically described based on the illustrated embodiments. FIGS. 1 and 2 show four coaxial dielectric resonators 1A, 1B, 1C and 1 as an example of the present invention.
A dielectric filter composed of D is shown. Here, the coaxial dielectric resonator uses a dielectric material 5 (here, a dielectric substance having a high dielectric constant ε _r = 93) between the outer conductor 3 and the inner conductor 4 in the shape of a square tube. ) And has a configuration of a known quarter-wavelength coaxial dielectric resonator that resonates at λ / 4. Here, the leads 6 extend through the inner conductors 4 of all the dielectric resonators 1A to 1D, and thus, the adjacent dielectric resonators have ends of the inner conductor connected through the leads 6. Connected
The dielectric resonators 1A to 1D are coupled in series as a whole. Each dielectric resonator 1 is mounted on a dielectric substrate 7 such as Teflon (trade name) that supports the resonator.
Electrodes 8 of required size grounded to outer conductors 3A to 1D
A, 8B, 8C, and 8D. Capacitances C ₂ , C ₃ , and C between the ground electrode plate 9 provided below the substrate 7 are provided.
₄ constitute a C _5. This equivalent circuit is shown in FIG.
In FIG. 2, C ₁ denotes a capacitance formed between an electrode plate formed on the dielectric substrate 7 adjacent to the dielectric resonator 1A and connected to the lead 6 and the ground electrode plate 9. Show.

In such a configuration, the frequency of the attenuation pole of the dielectric filter is determined by the resonance frequency of the dielectric resonator, and the frequency from the cutoff frequency to the attenuation pole and the depth thereof are determined by the impedance formed by the resonator. It is set by the dance and the capacitance that constitutes the circuit (see FIG. 3). Here, the circuit configuration of FIG. 4 is simulated by a computer, and each element has a capacitance C _1.
= _2.5 pF, C ₂ = 4 pF, C ₃ = 3 pF, C ₄ = 4
pF, C ₅ = 2.5 pF, impedance Z ₀ = 10 OHM of a coaxial dielectric resonator STL having a configuration according to the present invention (the outer conductor is grounded via a capacitance), and its resonance frequency F ₀ = 900 MHZ It is.

In the low-pass filter thus configured, the capacitance can be adjusted in a form including the stray capacitance held by the outer conductor 3 of the coaxial dielectric resonator. Therefore, the adjustment of the attenuation characteristic is extremely easy. In the above configuration, the magnitude of the capacitance used is larger than the value conventionally used, so that it is strong and stable against factors such as stray capacitance and is lower than the impedance of the conventional filter. Impey
Each stage can be composed by dance.

FIG. 8 shows a circuit configuration (1 MHZ filter) showing one specific example of the present invention and its filter characteristics. FIG. 9 shows the same circuit configuration and a capacitance of 1000. Circuit configuration showing a specific example that is 1 / (1
GHZ filter) and its filter characteristics.

FIGS. 10 and 11 show circuit configurations (1 MHZ and 1 GHZ) for realizing a filter having a pole.
) And their filter characteristics.

[0011]

The present invention has been described in detail above, and the coaxial dielectric resonator has a resonance frequency in a required frequency range.
In addition, since the outer conductor is grounded via a required capacitance so as to determine the pass area of the dielectric filter using the resonance frequency as an attenuation value, the coaxial dielectric resonator is used as a low-pass filter. At this time, it is possible to easily set the cutoff frequency in the set resonance frequency band, adjust the attenuation characteristics, and the like.

[Brief description of the drawings]

FIG. 1 is a perspective view illustrating an embodiment of the present invention.

FIG. 2 is an equivalent circuit diagram of the embodiment.

FIG. 3 is an attenuation characteristic diagram of the embodiment.

FIG. 4 is a configuration diagram of each element set in a computer to obtain the characteristic diagram.

FIG. 5 is a circuit configuration diagram for explaining a conventional example.

FIG. 6 is a circuit configuration diagram of a conventional example.

FIG. 7 is a circuit configuration diagram of a conventional example.

FIG. 8 is an equivalent circuit diagram and a filter characteristic diagram of one embodiment of the present invention.

FIG. 9 is an equivalent circuit diagram and a filter characteristic diagram of another specific example of the present invention.

FIG. 10 is an equivalent circuit diagram and a filter characteristic diagram of another specific example of the present invention.

FIG. 11 is an equivalent circuit diagram and a filter characteristic diagram of still another specific example of the present invention.

[Explanation of symbols]

 1, 1A, 1B resonator 3 outer conductor 4 inner conductor 5 dielectric material 6 lead 7 substrate 8A, 8B electrode

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Shotaro Hayashi 5 of 1978 Kogushi, Ube City, Ube City, Yamaguchi Prefecture Ube Industries, Ltd. Ube Research Laboratories (56) References 57-133103 (JP, U)

Claims (1)

(57) [Claims] A plurality of quarter-wavelength coaxial dielectric resonators each having a dielectric filled between an inner conductor and an outer conductor are arranged, and the plurality of quarter-wavelength coaxial dielectric resonators are arranged. The axial ends of the inner conductor of one dielectric resonator and the axial ends of the inner conductor of the other dielectric resonator are connected between adjacent ones and are connected in series as a whole. Wherein each of the plurality of quarter-wavelength coaxial dielectric resonators is grounded via a capacitance.