JPH04347901A - Band stop filter and its stop band adjusting method - Google Patents

Abstract

PURPOSE:To provide the structure and the stop band adjusting method for a band stop filter where a high airtightness is kept and the stop band frequency can be adjusted. CONSTITUTION:An oscillating circuit is mounted on an alumina substrate 21, and this mounting part is sufficiently hermetically sealed in a metal lid 22. The end part of a micro strip line 11 constituting the band stop filter is extended out of a vessel, and a terminating resistance 13 is formed on the substrate 21 on the outside of the vessel by a thick or thin film. The terminating resistance 13 exposed out of the vessel is trimmed by a laser or the like and has partial materials vaporized to change its resistance value.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a band rejection filter in a high frequency circuit device constructed using a dielectric resonator and a method for adjusting the rejection band thereof.

0002

2. Description of the Related Art Conventionally, a band rejection filter using this type of dielectric resonator has a structure shown in FIG. The dielectric resonator 1 shown in FIG.
It is electromagnetically coupled to the microstrip line 3 formed above and acts as a band rejection filter. This band-stop filter is housed in a grounded shield case 4 shown in FIG. 4B, and its stop band is adjusted by screws 5 set to the same potential as the shield case 4. That is, by rotating the screw 5 and changing the distance between the screw 5 and the dielectric resonator 1, the resonant frequency is finely adjusted. This band-elimination filter is represented by the equivalent circuit shown in FIG. 3(c), and is equivalently represented as a parallel resonant circuit of a resistor R, an inductance L, and a capacitor C. After the fine adjustment is made, the screws 5 are fixed with nuts to maintain airtightness inside the shield case 4, and the tops of the screws 5 are further covered with resin to seal the shield case 4.

[0003] Such band rejection filters are supplied as filters themselves, and also as oscillation circuits constructed by combining semiconductor elements such as FETs (field effect transistors) and bipolar transistors with this filter. is also supplied.

0004

However, in the conventional bandpass element filter described above, the screw 5 for adjusting the stop band is sealed as described above to maintain airtightness within the shield case 4; Such a sealing structure has poor moisture resistance. This has led to deterioration of the wiring and semiconductor elements within the shield case 4.

[0005] In order to eliminate such drawbacks, a structure has been considered in which a lid without adjustment screws is bonded onto the substrate 2 and the band rejection filter is sealed. Such a sealing structure provides high airtightness and eliminates problems such as deterioration of the element. However, after the lid is bonded to the substrate 2, it becomes impossible to adjust the stop band. Therefore, the error in the stopband frequency is 1
When accuracy on the order of MHz is required, the manufacturing yield of band-stop filters has been reduced.

The present invention has been made to solve these problems, and provides a structure of a band-stop filter that can adjust the stop band frequency while maintaining high airtightness, and a stop band of the band-stop filter. The purpose is to provide an adjustment method.

[0007]

[Means for Solving the Problems] The present invention provides a band-stop filter configured using a dielectric resonator that electromagnetically couples to a microstrip line in a hermetically sealed container. A terminating resistor connected to one end of the strip line is provided outside the container, and the resistance value of the terminating resistor is adjusted to adjust the stopband frequency of the band-elimination filter.

[0008] Also, a band-stop filter configured using a dielectric resonator that is electromagnetically coupled to a microstrip line, a container for storing the band-stop filter in an airtight manner, and a microstrip line. and a terminating resistor provided outside the container and connected to one end of the container.

[0009]

[Operation] The resonant frequency of the band rejection filter provided inside the hermetically sealed container changes as the resistance value of the terminating resistor provided outside the container changes.

0010

Embodiment FIG. 2 is a circuit diagram of a high frequency oscillation circuit constructed using a band rejection filter according to an embodiment of the present invention.

A microstrip line 11 is connected to the gate of the FET Q1, and a dielectric resonator 12 is electromagnetically coupled to the microstrip line 11. The microstrip line 11 and the dielectric resonator 12 constitute a band rejection filter, and the other end of the microstrip line 11 is connected to a first terminating resistor 13 whose one end is grounded. Also, FET
The source of Q1 is grounded, and the drain is connected to a matching circuit (Output Matc) that matches the output impedance.
h) Connected to 14. Furthermore, a second terminating resistor 15 is connected to the output end of the matching circuit 14.

FIG. 1 is a perspective view showing an oscillation circuit having the above-mentioned circuit configuration housed in a container. Alumina substrate 21
The oscillation circuit shown in FIG. 2 is mounted on the top, and a metal lid 22 is bonded to the substrate 21 to cover this mounting portion. This adhesion is performed using a sealing metal 23, and the inside of the metal lid 22 is sufficiently hermetically sealed. Further, the end portion of the microstrip line 11 constituting the band rejection filter is extended outside the container, and the terminating resistor 13 is formed as a thick film or a thin film on the substrate 21 outside the container. This terminating resistor 13 is connected to the ground pattern 2
It is grounded by 4.

FIG. 3 is an equivalent circuit diagram of a band rejection filter constituted by the microstrip line 11 and the dielectric resonator 12 mounted in the lid 22. The band-stop filter connects a microstrip line 1 to a parallel resonant circuit consisting of a resistor R, an inductance L, and a capacitor C.
This is equivalent to a circuit configuration in which 1a and 11b are connected in series. Here, the resistance value of the resistor R is equivalent to 625 [Ω], the induction component of the inductance L is equivalent to 5.2 [pH], and the capacitance of the capacitor C is equivalent to 43 [pF]. Further, the film thickness of each microstrip line 11a, 11b is 10 [μm], the line width is 635 [μm], the line length of the microstrip line 11a is 2.68 [mm], and the line length of the microstrip line 11b. is equivalently expressed as 6 [mm]. The resistance value Z0 of the terminating resistor 13 is normally set to 50Ω, but in this embodiment, it is set to 200[Ω].

In such a configuration, the terminating resistor 13 exposed outside the container is trimmed with a laser or the like, and the terminating resistor 1
A part of the material of 3 is vaporized to change the resistance value of the terminal resistor 13. The relationship between the stopband frequency of the band-stop filter and the S-parameter S11, which is the input reflection coefficient of the FET Q1, as the resistance value of the terminating resistor 13 changes is shown in the graph of FIG. The horizontal axis of the graph represents the stopband frequency [GHz], and the vertical axis represents the S11 parameter [dB]. curve 31
, 32, 33, and 34, the resistance values of the terminating resistor 13 are 200 [Ω], 100 [Ω], 50 [Ω], and 25 [Ω], respectively.
] shows the characteristics in the case of When the resistance value of the terminating resistor 13 is 200 [Ω], the center point A of the stopband frequency is 10.6471 [GHz] from the curve 31,
In the case of 100 [Ω], the center point B of the stopband frequency is 10.645 [GHz] from the curve 32. Also, 5
In the case of 0 [Ω], the center point C of the stopband frequency is 10.6434 [GHz] from the curve 33, and in the case of 25 [Ω], the center point D of the stopband frequency is 10.6434 [GHz] from the curve 34.
．． It becomes 6417 [GHz].

Based on the relationship shown in the graph of FIG. 4, the termination resistor 13 is trimmed to satisfy the oscillation frequency conditions required for the oscillation circuit, and the stopband of the bandstop filter is appropriately adjusted. In this example, trimming is performed until the resistance value of the terminating resistor 13 becomes 25 [Ω], the stopband center frequency is set to 10.6417 [GHz], and the parameter S11
was set to -1.4249 [dB]. After adjustment, each pattern on the substrate 21 formed outside the lid 22 is molded with resin to protect the exposed circuit elements.

According to this embodiment, the oscillation circuit using the band-elimination filter is sufficiently hermetically sealed within the lid 22. Moreover, by trimming the termination resistor 13 located outside the lid 22, it becomes possible to adjust the stopband frequency of the bandstop filter in a state where these are sealed.

FIGS. 5(a), 5(b), and 5(c) are diagrams showing other configuration examples of high frequency oscillation circuits constructed using band rejection filters. In each figure, 11a to 11c are microstrip lines, 12a to 12c are dielectric resonators, and 13a to 13c are terminal resistors. In the oscillation circuits having these configurations, the oscillation circuits are sealed with a lid, and the terminating resistors 13a to 13c are provided outside the container and trimmed, thereby achieving the same effects as in the above embodiments.

[0018]

As explained above, according to the present invention, the resonance frequency of the band rejection filter provided inside the hermetically sealed container changes depending on the resistance value change of the terminating resistor provided outside the container. It changes accordingly.

Therefore, it has become possible to provide a structure of a band-stop filter and a method for adjusting the stop band of the band-stop filter, which can adjust the stop band frequency while maintaining high airtightness.

[Brief explanation of drawings]

FIG. 1 is a perspective view showing the structure of a high frequency oscillation circuit device using a band rejection filter according to an embodiment of the present invention.

FIG. 2 is a circuit diagram showing the configuration of an oscillation circuit installed in the device shown in FIG. 1.

FIG. 3 is an equivalent circuit diagram of a band-stop filter according to this embodiment configured using a dielectric resonator.

FIG. 4 is a graph showing how the relationship between the stopband frequency and parameter S11 of the bandstop filter according to the present embodiment is affected by changes in the resistance value of the terminating resistor.

FIG. 5 is a circuit diagram showing another configuration example of the high frequency oscillation circuit.

FIG. 6 is a diagram showing the configuration of a conventional band rejection filter.

[Explanation of symbols]

11...Microstrip line 12...Dielectric resonator 13...Terminal resistor 21...Alumina substrate 22...Metal lid 23...Metal for sealing 24...Grand pattern

Claims (2)

[Claims] 1. A band rejection filter configured using a dielectric resonator that electromagnetically couples to a microstrip line is provided in a hermetically sealed container, and is connected to one end of the microstrip line. A method for adjusting a stop band of a band-elimination filter, characterized in that a termination resistor is provided outside the container, and a resistance value of the termination resistor is adjusted to adjust a stop-band frequency of the band-elimination filter. 2. A band-elimination filter configured using a dielectric resonator electromagnetically coupled to a microstrip line, a container for storing the band-elimination filter in an airtight manner, and the microstrip. A band rejection filter configured to include a terminating resistor provided outside the container and connected to one end of the line.