JPS632404A - Method for adjusting band of dielectric filter - Google Patents

Abstract

PURPOSE:To eliminate the necessity of skill for adjusting a coupling element and to improve the impact resisting force of a dielectric filter, by providing a hybrid IC circuit composed of a thick-film capacitor, thick-film resistance, and high-speed switching diode for high frequency. CONSTITUTION:Dielectric resonators 1 and 2 constitute a 1/4-wavelength coaxial resonator and a thick-film capacitor C1, thick-film resistance R1, and diode D are mounted on a hybrid IC circuit 3. Moreover, a small-signal high-speed switching diode having an extremely small interterminal capacity is used as the diode D and a reverse voltage or reverse bias voltage can be applied across the diode D through the resistance R1. Because of this reverse voltage, the equivalent capacity of the diode D can be made extremely smaller and, when the reverse voltage is changed, the equivalent capacity can be changed by about two times. In addition, when the coupling capacity value between the dielectric resonators 1 and 2 is changed, the band characteristic, especially, the band width of a BPF can be adjusted precisely and the BPF can be adjusted from the outside. Therefore, no skill is required for adjusting the coupling capacity and, since the variable element has no mechanical structure, this filter can be made stronger against impacts.

Description

[Detailed Description of the Invention] (Field of Industrial Application) The present invention is directed to a method for adjusting the bandwidth of a bandpass filter using a dielectric band coaxial resonator using a ceramic dielectric, which is used in the microwave band, etc. Since the bandwidth is adjusted by adjusting the DC voltage applied to a high-frequency high-speed switching diode with a very small capacitance to which a reverse voltage is applied, it is easy to operate, compact, and inexpensive.

(Prior Art) Conventionally, a filter (hereinafter referred to as BPF) with necessary band-pass characteristics was obtained by arranging several dielectric resonators and appropriately coupling them. M-coupling and C-coupling are used for this resonator coupling method. FIG. 3 is a circuit diagram of an example. When C coupling (static four-coupling) is used in this way, the coupling capacitance C8 of around 0.3 pF is sufficient in the microwave band.

Note that in FIG. 3, 1 and 2 are dielectric resonators.

is used, but if you want to fine-tune its capacitance value (shout out, connect multiple fixed capacitors in series or parallel (j), or connect a small variable capacitor in series or parallel with a fixed capacitor (= I was trying to connect it and make some fine adjustments.

However, as the external dimensions of the BPF and the capacitance value of the capacitor become smaller, the small variable capacitor itself becomes larger and more expensive than the BPF.

Furthermore, variable capacitors with a capacitance of 1 pF or less are hardly commercially available. Conventionally, in order to solve this problem, thick film capacitors were trimmed.
For chip capacitors, a method is used in which a plurality of chip capacitors are connected in series to obtain the required capacitance value, but changing and adjusting the capacitance of 1 pF or less is extremely troublesome.

It is also suitable for mass production (= is also suitable.) By adopting the method of the present invention, it is possible to adjust the coupling capacitance (-) without requiring any skill, and because the variable element does not have a mechanical structure, it can be expected to be resistant to impact.

(Structure and operation of the invention) FIG. 1 is an equivalent circuit showing an example of the structure of a dielectric filter embodying the present invention, and FIG. 2 is a perspective view of the filter shown in FIG.
), a top view (Bl), a perspective view (q) of the dielectric resonator, and its equivalent circuit (D). In these figures, 1 and 2 are dielectric resonant elements, and a coaxial resonator with a length of 3 AID 3 is a hybrid integrated circuit (Ic3, which includes a
, C□, and D are installed. Among these, C type is a thick film capacitor, which is made using the gap between the R1 electrode and the 1 terminal to aim for 0.3 pF. vDo is the DC voltage applied to the DC voltage application terminal, and 4 in Figure 2 (B) is "
Land for DC application, R1 is a thick film resistor, D is a diode (
There are chip and mini-mold type optics, but this diode is for high-frequency, small-signal, high-speed switching with extremely small capacitance between terminals, and a reverse voltage or reverse bias voltage (Ov ~ 15V) can be applied through the thick film resistor R1. . Due to this reverse voltage, the equivalent capacitance of D is very small, and if the reverse voltage is changed, it will change by about twice (1pF'-2pF).Also, since the thick film resistance ratio □ is high impedance,
Since the DC reverse voltage is applied to the cathode of the diode through the high resistance R1, even if the wiring for application is long, the BP
It has almost no effect on the characteristics of F.

By changing the coupling capacitance value between dielectric resonant elements using the above characteristics, it is possible to finely adjust the BPF band characteristics and the special C2 bandwidth (the rate of change in the bandwidth is the rate of change in the coupling capacitance). (corresponds to
It has the advantage that it can be adjusted from outside.

(Effects of the Invention) According to the present invention, it is possible to significantly change the coupling capacitance value of 0.5 pF or less by changing the external voltage for bias by using a bias diode together with the coupling capacitance value. It is also possible to use an inexpensive diode in place of an expensive variable capacitor for microwaves, etc.
It is also easy to make a thick film IC.

Note that the actual binding capacity must be kept at about 5% of the calculated value.

[Brief explanation of drawings]

FIG. 1 is an equivalent circuit diagram of an example of a dielectric filter embodying the present invention, and FIG. 2 is a perspective view 4 of the filter of FIG.
A perspective view of a top surface resonator and a dielectric resonator (q and its equivalent circuit CD+, Fig. 3 is a bandpass filter using a conventional C-coupled dielectric resonator C2. 1.2... Dielectric Resonator, 3...Hybrid IC circuit, 4... Land for DC voltage application (1and, terminal area).

Claims (1)

[Claims] In a dielectric bandpass filter configured by coupling a dielectric resonator with a small capacitance capacitor, the coupling capacitor is connected in series with a thick film capacitor having a set capacitance value of 1 pF or less and is reverse biased. The DC voltage for voltage is configured by a high-speed switching diode for high frequency applied through a high resistance, and the effective coupling capacitance value is adjusted by changing the reverse bias DC voltage, and the bandwidth of the dielectric bandpass filter is adjusted. A dielectric filter bandwidth adjustment method characterized by fine adjustment.