Wave transmission lines and networks – Plural channel systems – Having branched circuits
Patent
1998-04-27
1999-11-16
Gensler, Paul
Wave transmission lines and networks
Plural channel systems
Having branched circuits
333 33, 333260, H01P 508
Patent
active
059865199
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
This invention relates to a coaxial cable transition to a planar substrate arrangement, such as a coaxial cable to microstrip arrangement.
Coaxial cable is widely employed in system configuration, where microwave and radio signals are processed. A typical use of a coaxial to planar substrate transition is in a mobile communications network base station where receive and transmit electronics are connected to a triplate or layered antenna by way of a coaxial cable. One form of triplate antenna comprises a microstrip feed network printed on a dielectric film or substrate which provides the feed probes or patches which extend into or are arranged within radiating apertures defined through the outermost groundplane of the triplate antenna. In such an arrangement, the central conductor of a coaxial cable is soldered directly to the microstrip circuit of the antenna. The axis of the central conductor can either be in-line or orthogonal with respect to the substrate and the earthed sheath is connected to the groundplanes of the antenna. Alternatively, the microstrip array may be formed upon a printed circuit board manufactured from a substance such as PTFE. U.S. Pat. No. 4,918,458 (Ford Aerospace) describes such an antenna arrangement which is fed by way of a coaxial supply cable. GB-A-2007919 (Raytheon) also provides an antenna arrangement which is fed by way of a coaxial supply cable.
These types of configuration, while easy to manufacture can suffer from the generation of passive intermodulation products. Power handling capabilities can be limited since high losses will result from the isolating distances necessary from the coaxial transition section to any power dividers such as Wilkinson couplers. Further problems arise in the use of the dielectrics having high temperature capabilities necessary in order to allow solder connections to be made. Coupled lines can be present in order to provide a d.c. block in cases such as active antennas.
In the design of mechanical connections with microwave conductors, extreme care needs to be exercised for critical applications requiring high linearity, for example, cellular radiocommunications and satellite communications. In the case where components are welded or soldered, attention needs to be paid to the electrical conductor's surface; irregularities and imperfect metal to metal contacts lead to electrical non-linearities. This introduces passive intermodulation, in which deleterious, spurious signals are generated and, generally, these effects vary with frequency, contact pressure, age and other factors.
An object of the invention is to provide an improved coaxial cable to microstripline connection with high mean or peak power handling and very low passive intermodulation product generation.
SUMMARY OF THE INVENTION
In accordance with one aspect of the invention, there is provided an arrangement for transferring high frequency microwave signals between a cable and a microstrip printed circuit on a dielectric substrate, the arrangement comprising: a coaxial cable, a dielectric substrate carrying a first microstrip printed circuit and an intermediate dielectric substrate carrying a second printed circuit; wherein an inner conductor of the coaxial cable is connected to the second printed circuit of the intermediate dielectric substrate and the outer conductor of the coaxial cable is connected to a ground plane associated with said dielectric substrate; and wherein the printed circuit on the intermediate dielectric is operable to reactively couple all the signals from the coaxial cable to the first printed circuit on said dielectric substrate through the printed circuit of the intermediate dielectric substrate.
The intermediate dielectric substrate can carry a metallized surface acting as a ground plane and to which the ground of the coaxial cable is connected, which ground plane can reactively couple with said ground plane associated with said dielectric substrate.
The inner conductor of the coaxial cable port can be connected to a first n
REFERENCES:
patent: 5073761 (1991-12-01), Waterman et al.
patent: 5309122 (1994-05-01), Cox et al.
patent: 5394119 (1995-02-01), Pleva et al.
patent: 5757246 (1998-05-01), Johnson
Kellett Colin John
Smith Adrian
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