Wave transmission lines and networks – Coupling networks – Wave filters including long line elements
Patent
1994-04-08
1995-04-11
Nelli, Raymond A.
Wave transmission lines and networks
Coupling networks
Wave filters including long line elements
333202, H01P 120
Patent
active
054062357
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The present invention relates to a high frequency device, such as a high frequency resonator, a high frequency filter, a high frequency oscillator, and a dielectric resonator, used in radio equipment or other communication equipments.
BACKGROUND OF THE INVENTION
Various types of high frequency devices have been conventionally used in wireless equipment including portable or cordless telephones, or other communication equipments.
These high frequency devices include a high frequency filter, high frequency oscillator, dielectric resonator, high frequency amplifier, or duplexer.
Hereinafter, examples of the conventional high frequency devices will be described with reference to the accompanying drawings.
PRIOR ART EXAMPLE 1
High frequency transmission line (refer to FIGS. 17A to 17C)
FIGS. 17A to 17C are diagrams showing a conventional high frequency transmission lines, in which FIG. 17A shows a microstrip line, FIG. 17B a suspended microstrip line, and FIG. 17C an inverted microstrip line. Those are used as high frequency signal transmission lines on circuit boards or as parts in delay lines.
In FIGS. 17A to 17C, reference numeral 100 denotes an outer conductor, 102 a dielectric, 103 an inner conductor, and 104 a clearance.
Conventionally, microstrip lines, shown in FIGS. 17A to 17C, have been used for the high frequency transmission lines. Among them, the microstrip line structured as shown in FIG. 17A is generally most extensively used.
This microstrip line has an inner conductor (conductor used as a signal line) 103 provided on one side of a dielectric 102, and an outer conductor (conductor normally used as GND electrode) 101 provided on the other side (side opposite the inner conductor 103) of the dielectric 102.
The reason why this microstrip line structured as described is widely used is because it is smaller and less expensive and easier to manufacture than other microwave circuits such as wave guide circuits when it is used in forming a flat high frequency circuit, for example.
However, the microstrip line mentioned above notably suffers general losses in the transmission line (e.g., radiation loss, dielectric loss, and conductor loss). In order to reduce the losses, improved products have been developed, which include the suspended microstrip line shown in FIG. 17B and the inverted microstrip line shown in FIG. 17C.
The suspended microstrip line, as depicted in FIG. 17B, has the inner conductor and dielectric suspended by a support member to provide a clearance 104 between the dielectric 102 and the outer conductor 101.
The inverted microstrip line has the inner conductor 103 provided on one side of the dielectric 102, which side faces the outer conductor 101 and provides a clearance 104 between the dielectric 102 and the outer conductor 101 as shown in FIG. 17C.
The prior-art microstrip lines have problems described in the following.
(1) In contrast to the ordinary microstrip line, the suspended microstrip line or inverted microstrip line is a transmission line with reduced loss, but it is necessary to form the inner conductor as a signal line by patterning on the dielectric and have the inner conductor overhang separated from the outer conductor which is GND conductor. Therefore, its setting is unstable and its manufacture is difficult.
(2) The suspended microstrip line and the inverted microstrip line, for the structural reason, need to have the outer conductor (GND conductor) more than a certain extent wider than the width of the inner conductor (signal line). This makes it difficult to miniaturize the line.
PRIOR ART EXAMPLE 2
High frequency filter (refer to FIGS. 18A and 18B and FIGS. 19A to 19C)
FIGS. 18A and 18B show examples of high frequency filters, and FIGS. 19A to 19C show equivalent circuits of the high frequency filter of FIGS. 18A and 18B.
In FIGS. 18A and 18B and FIGS. 19A to 19C, reference numeral 111 denotes a substrate (dielectric), 112 and 113 .lambda./4 type strip resonators, 114 a coupling capacitor, 115 throughholes, 116 GND electrodes (wide-a
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Nelli Raymond A.
TDK Corporation
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