JPS6370601A - Microstrip type band stop filter - Google Patents

Abstract

PURPOSE:To miniaturize the structure, reduce the weight and easily realize a desired band stop filter by using a lumped constant capacitor so as to adopt the structure varying the coupling between a main line and a resonator freely. CONSTITUTION:Lumped constant capacitors 6a-6c are provided on resonators 2a-2c, connected to the main line 1 by conductor wires 7a-7c to couple the resonators 2a-2c with the main line 1. The capacitors 6a-6c are realized by adhering a conductor film 13 to upper and lower faces of a dielectric 12. The coupling between the main line 1 and each resonator 2 is varied by the static capacitance of each capacitor 6, a desired coupling is given between the main line 1 and each resonator 2 by selecting the thickness of the dielectric 12 and the area of the conductor film 13 properly to obtain a band stop characteristic.

Description

[Detailed Description of the Invention] (Industrial Application Field) The present invention is used in the microwave band to connect to, for example, broadcasting equipment or transmission equipment, and to remove spurious signals that cause noise and interference radio waves. This invention relates to a microstrip band-stop filter.

(Prior Art) Conventionally, a narrowband band-elimination filter is used in a microwave circuit for the purpose of suppressing spurious at frequencies close to a signal band. A band-elimination filter that has been used for this purpose is shown in Figures 7 and 8.
Hubblein bandstop filters are known. FIG. 7 shows an internal plan view, and FIG. 8 shows a front sectional view.

In FIG. 7, 1 is the main line, 2a to 2c are resonators whose electrical resonance wavelengths are approximately equal to the stopband center frequency, and 3 is a metal block for short-circuiting one end of the resonators 2 and 2c to the case 4. 5a to 5c indicate gaps formed between the main line 1 and the resonators 2a to 2c, respectively. Now, the main line 1 and the resonators 2a to 2c are coupled through capacitors with gaps 5a to 5c to obtain band rejection characteristics.

The circuit configuration in this case is shown isometrically using lumped constant elements as shown in Figure 9(a), and the correspondence between the impedance network r1 capacitor C1 inductance L and each element in Figure 7 is as follows. It is.

r is a network with the characteristic impedance of the main line transmission line. C is a capacitor that exists between each resonator and the main line due to a gap between each resonator. L is the total inductance of each resonator and the metal block that short-circuits one end of the resonator to the case 4.

Therefore, a stripline band-elimination filter is constructed as shown in FIGS. 7 and 8 so that the series resonance frequency of the inductance L and capacitor C becomes the center frequency of the band-elimination filter. In this case, three sections of band-elimination filters are connected in cascade, as shown in FIG. 9(a).

An example of the transmission loss characteristic of one section of the band-elimination filter described above is shown in FIG. 9(b), where to is the center frequency of the band-elimination filter. If the band-elimination filter is configured to have two or three sections, its transmission loss characteristic will increase to about twice or twice the loss shown in FIG. 9(b). Therefore, the number of sections of the band-elimination filter is determined so as to adapt to the required degree of suppression of spurious and the like.

(Problems to be Solved by the Invention) However, since the stripline type band-elimination filter has a three-dimensional structure, it has a disadvantage that the structure is complicated and it is difficult to reduce the size and weight. In addition, if this is made into a microstrip structure as it is, the required capacitance cannot be obtained with just the gap between the main line and the resonator.
It is impossible to realize the band blocking function.

The present invention improves this point, and aims to provide a microstrip type band-elimination filter that is simpler in structure, smaller and lighter than conventional stripline type band-elimination filters.

(Means for Solving the Problems) The present invention provides a microstrip band-stop filter comprising a main line and a resonator coupled to the main line by capacitance, wherein the resonator It is characterized by comprising a lumped constant capacitor provided above and means for connecting the lumped constant capacitor to the main line.

(Example) An example of the present invention will be described based on the drawings. 1 and 2 are diagrams showing a first embodiment of the present invention, with FIG. 1 being a plan view and FIG. 2 being a front view. Compared to the conventional device shown in FIGS. 7 and 8, the resonator 2a
The feature is that the main line 1 and the resonators 28 to 2c are coupled by providing lumped constant capacitors 6a to 6c on ~2c and connecting them to the main line 1 through conductor wires 7a to 7c. be. In FIGS. 1 and 2, reference numeral 8 indicates a dielectric substrate, and reference numeral 9 indicates a conductor ribbon for short-circuiting one end of the resonators 2a to 2c to the ground conductor 10.

Other points are the same as the conventional apparatus shown in FIGS. 7 and 8], and the same reference numerals indicate elements with the same function, respectively.

The lumped constant capacitors 6a to 6c can be realized by attaching conductive films 13 to the upper and lower surfaces of the dielectric 12, as shown in a perspective view in FIG. Since the coupling between the main line 1 and the resonators 28 to 2C changes depending on the capacitance of the lumped constant capacitors 68 to 6c, the main line 1 and resonators 2a to 2C
It is possible to provide the desired coupling between the two and obtain band rejection characteristics.

FIG. 4 is a diagram showing an application example of the embodiment of FIG. 1. As shown in FIG. 4, the upper surface conductor M13 of the lumped constant capacitor 6a is connected to a plurality of (three in FIG. 4) lands 13. ~13
Divided into sK, each land 13. ~13. If connected to the main line 1 by the conductor wires 7al to 7al, the capacitance of the lumped constant capacitor 6a can be finely adjusted by cutting the conductor wires 7a1 to 7as, which is extremely useful in practice.

Although FIG. 4 only explains the lumped constant capacitor 6a, other lumped constant capacitors can be constructed in the same way.

5 and 6 are diagrams showing a second embodiment of the present invention, with FIG. 5 being a plan view and FIG. 6 being a front view. In comparison with the first embodiment shown in FIGS. 1 and 2, the resonators 28 to 2C are resonators whose electrical resonance wavelengths are about 2% of the stop band center frequency, and the resonators provided above The lumped constant capacitors 66 to 6c are connected to the conductor ribbon 15a.
-15e, and the main line 1 and the resonator 2a=2e are coupled together.

Other points are similar to the first embodiment shown in FIGS. 1 and 2, and the same reference numerals indicate the same parts, respectively.

The microstrip type band-stop filter according to the present invention also includes:
It has a circuit configuration similar to the lumped constant circuit band-stop filter shown in FIG. 9(a) on the same side, and has transmission loss characteristics as shown in FIG. 9(b). It has a blocking function.

(Effects of the Invention) As explained above, according to the present invention, a microstrip structure is adopted in which the coupling between the υ main line and the resonator can be freely changed using a lumped constant capacitor, which is compared to the conventional stripline type. The structure can be made into a cylindrical part, making it possible to reduce the size and weight, and also easily achieve desired band rejection characteristics. The present invention has such effects.

[Brief explanation of the drawing]

1 and 2 are a plan view and a sectional view showing a first embodiment of the present invention, respectively, FIG. 3 is a perspective view of a lumped constant capacitor used in the embodiment, and FIG. 4 is a diagram showing the first embodiment. FIGS. 5 and 6 are a plan view and a sectional view showing a second embodiment of the present invention, respectively, and FIGS. 7 and 8 are main parts of a conventional device, respectively. FIG. 9(a) is an equivalent circuit diagram of a band-stop filter using lumped constant elements, and FIG. 9(b) is a diagram showing an example of its transmission loss characteristics. 1... Main line, 2a-2c... Resonator, 3... Metal block, 4... Case, 58-5C... Gap, 6&-6c... Lumped constant capacitor, 7a-7C
... Conductor wire, 8... Dielectric substrate, 9... Conductor ribbon, 10... Ground conductor, 12... Dielectric, 13
...Conductor film, 1,5 a-15c...Conductor ribbon. Agent Patent Attorney Shinsuke Honjo 1゜Figure 2 Figure 4 Figure 5 Figure 6 Figure 7 Figure 8 (a) □ f □ o. Distribution! ? Treatment □ (b) Figure 9

Claims (3)

[Claims] (1) In a microstrip band-stop filter comprising a main line and a resonator coupled to the main line by capacitance, a lumped constant capacitor provided on the resonator, and a lumped constant capacitor provided on the resonator, and a lumped constant capacitor provided on the resonator; A microstrip type band-elimination filter comprising means for connecting a capacitor and the main line. (2) A microstrip band-stop filter according to claim 1, wherein the connecting means is a conductor wire. (3) A microstrip band-stop filter according to claim 1, wherein the connecting means is a conductive ribbon.