Wave transmission lines and networks – Plural channel systems – Having branched circuits
Patent
1996-11-19
1998-11-24
Gensler, Paul
Wave transmission lines and networks
Plural channel systems
Having branched circuits
333238, H01P 518
Patent
active
058413286
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to a directional coupler for electromagnetically coupling a signal input primary line with an auxiliary line. More specifically, the present invention pertains to a directional coupler having conductors provided on a layer of a dielectric material to thereby provide paired lines to be coupled.
BACKGROUND ART
The U.S. Pat. No. 5,329,263 issued on Jul. 12, 1994 to Kazuaki Minami discloses a directional coupler having a dielectric substrate provided on one side surface with a conductive grounding electrode which extends throughout the surface and on the other side surface with paired signal transmitting coupling lines of a conductive material. These lines are formed on the surface of the substrate by parallelly extending portions, each of the parallelly extending portions of the coupling lines having opposite ends provided with leads which extends perpendicularly to the parallelly extending portions.
One of the coupling lines is connected through the lead at one end thereof with an input port and through the lead at the other end with an output port. The other coupling line is connected through the lead at one end with a second output port and through the lead at the other end with an isolation port. The coupling lines and the leads are connected together through a deposition of a conductive metal such as gold.
In this type of coupler, the isolation port is connected normally to the ground. As a signal is applied to the input port of the one coupling line, a corresponding signal is produced at the output of the one coupling line. A signal is also produced through electromagnetic coupling between the paired coupling lines at the second output port of the other coupling line. When an input signal is applied to the output port of the one coupling line an output is produced at the input port of the one coupling line, and at the same time an output is produced at the second output port of the other coupling line with a level which is different from the level when the input signal is applied to the input port. The difference in the signal level at the second output port of the other coupling line between the occasion when the input signal is applied to the input port of the one coupling line and the occasion when the input signal is applied to the output port is defined as the directionality or isolation of the coupler.
It has been recognized that the coupler shows a large directionality in response to an input signal wherein the length of the parallelly extending coupling lines is equal to 1/4 of the wavelength. It is noted further that the coupling power of the coupler is dependent on the distance between the coupling lines whereby a tight coupling is produced with a small distance whereas a weak coupling is produced with a large distance. In the coupler of the type disclosed by the aforementioned U.S. patent, the coupling lines are formed on a surface of the dielectric substrate. It should however be noted that the coupling lines may be embedded in the body of the dielectric body. In that case, the effective line wavelength is decreased to .lambda./4 .epsilon..sub.r, where .epsilon..sub.r designates a specific dielectric constant and .lambda. the wavelength of the input signal. Thus, the coupler size can be decreased by using a material of higher specific dielectric constant. It should therefore be understood that a dielectric material of an appropriate specific dielectric constant may be used for decreasing the size of a directional coupler.
In the case where a dielectric body is of a laminated structure wherein a plurality of dielectric layers are laid one over the other, the coupling lines can be provided between adjacent dielectric layers. In this structure, the paired coupling lines may be arranged on the opposite sides of a dielectric layer.
In a directional coupler having coupling lines embedded in a dielectric body as described, the dielectric layers are generally formed of a material of a high dielectric constant. However, using a dielectric material of
REFERENCES:
patent: 3723914 (1973-03-01), Cappucci
patent: 3999150 (1976-12-01), Caragliano et al.
patent: 5329263 (1994-07-01), Minami
patent: 5359304 (1994-10-01), Fujiki
patent: 5369379 (1994-11-01), Fujiki
Gensler Paul
TDK Corporation
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