JPH05110301A - Choke circuit - Google Patents

Abstract

PURPOSE:To simply and easily realize a choke circuit improving the isolation at an RF band. CONSTITUTION:A film resistor 4 is formed to a lower face or an upper face of a microstrip line 2 and an open stub 3 in the choke circuit in which the microstrip line 2 with a high impedance whose length is lambda/4 at an RF band and the open stub 3 made of a microstrip line whose length is lambda/4 are arranged on a dielectric board 5 in combination.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a choke circuit in a communication device, and more particularly to a choke circuit suitable for blocking DC and low frequency RF band signals.

[0002]

2. Description of the Related Art Conventional MIC (Microwave Integrated C
As shown in FIG. 3, the choke circuit in the ircuit) includes a high impedance strip line having a length of λ / 4 of an RF signal and an open stub formed by a strip line having a stub length of λ / 4. There is a configuration in which the above is combined and is drawn out from the RF transmission line.

[0003]

In this conventional choke circuit, a circuit constituted by combining a high impedance strip line 2 and a strip line open stub 3 is directly drawn from the RF transmission line 1, and the choke circuit is used. A DC or low frequency circuit is connected to the other side of the circuit. Therefore, depending on the conditions such as the load of the direct current or low frequency circuit part, the direct current or low frequency circuit part itself or a circuit in which the low frequency circuit and a part of the choke circuit are combined is a resonator in the RF frequency band. May act as. Therefore, if the choke circuit does not have sufficient isolation with respect to the RF frequency, it affects the RF transmission line that is DC-connected through the choke circuit and deteriorates various characteristics such as frequency characteristics. There is a problem that it may cause.

The present invention has been made in view of the above problems, and provides a choke circuit which improves isolation in the RF band and which can be easily obtained with a simple circuit configuration. With the goal.

[0005]

In order to achieve the above object, the present invention according to claim 1 provides a λ of RF band on a dielectric substrate.
In a choke circuit in which a / 4 length high impedance microstrip line and a λ / 4 length open stub formed by the microstrip line are arranged in combination, a film resistor is arranged on the dielectric substrate. The microstrip line and the open stub are arranged on the membrane resistor. The present invention according to claim 2 combines a high impedance microstrip line of RF band λ / 4 length and a λ / 4 length open stub formed by the microstrip line on a dielectric substrate. In the arranged choke circuit, the upper surface of the microstrip line and the open stub is covered with a film resistor.

[0006]

According to the choke circuit having the above-described structure, the direct current and low frequency circuit section itself or the circuit in which the low frequency circuit and a part of the choke circuit are combined resonates in the RF frequency band depending on conditions such as load. In addition to the isolation of the RF band by the choke circuit in the strip line, the blocking effect of the propagation of the RF band by the film resistor, and the isolation effect by absorption are added when it acts as a container.
Improve isolation.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, the present invention will be described with reference to the drawings. FIG. 1A shows a choke circuit according to the first embodiment of the present invention. In this embodiment, a high impedance microstrip line 2 having a length of λ / 4 of an RF signal and a low impedance open stub 3 formed of a microstrip line and having a stub length of λ / 4 are combined. The circuit is directly drawn from the RF transmission line 1 and led to the low frequency circuit section. The circuit (microstrip line 2 and open stub 3) is arranged on the film resistor 5 provided on the dielectric substrate 4. Further, FIG. 1B is a cross-sectional view taken along the line AA ′ of FIG. 1A, in which the conductor pattern of the microstrip line 5 is arranged on the film resistor 5 provided on the dielectric substrate 4. The structure is shown.

FIG. 2A shows a choke circuit according to the second embodiment of the present invention. In this embodiment, the film resistor 5 is coated on the upper portion of the circuit (microstrip line 2 and open stub 3) that is directly drawn from the RF transmission line 1 and guided to the low frequency circuit section. In addition, FIG.
FIG. 6A is a cross-sectional view taken along the line AA ′ of FIG. 7A, and shows a structure in which a conductor pattern of the microstrip line 2 is provided on the dielectric substrate 4 and the film resistor 5 is further coated on the conductor pattern. .. As the film resistor 5, various film-shaped resistors can be used.

According to the choke circuit having such a configuration, depending on the load condition of the direct current and low frequency circuit section connected to the other side of the choke circuit, the low frequency circuit section itself or the circuit section and the choke circuit are In the case where a part acts as a resonator in the RF band, in addition to the isolation in the RF band obtained only by the choke circuit, the film resistor causes RF due to resonance on the low frequency circuit side.
Since the band propagation is blocked and absorbed, the isolation from the low frequency circuit section side can be further increased, and the influence on the RF transmission line can be reduced.

[0010]

According to the present invention having the above-mentioned structure, it is possible to obtain a choke circuit having improved isolation in the RF band, and further, this circuit can be simply constructed and easily realized. Have.

[Brief description of drawings]

FIG. 1A shows a first embodiment of a choke circuit of the present invention, and FIG. 1B shows a sectional view taken along the line AA ′ of FIG.

FIG. 2A shows a second embodiment of the choke circuit of the present invention, and FIG. 2B shows a sectional view taken along the line AA ′ of FIG.

FIG. 3 shows an example of a conventional choke circuit.

[Explanation of symbols]

 1 ... RF transmission line 2 ... Microstrip line 3 ... Open stub 4 ... Dielectric substrate 5 ... Membrane resistor

Claims (2)

[Claims] 1. A choke circuit in which a high impedance microstrip line having a λ / 4 length in an RF band and a λ / 4 length open stub formed by the microstrip line are arranged in combination on a dielectric substrate, A choke circuit, wherein a film resistor is arranged on the dielectric substrate, and the microstrip line and an open stub are arranged on the film resistor. 2. A choke circuit in which a high impedance microstrip line having a λ / 4 length in an RF band and a λ / 4 length open stub formed by the microstrip line are arranged in combination on a dielectric substrate, A choke circuit in which a film resistor is coated on the upper surfaces of the microstrip line and the open stub.