Analysis and design of conical transmission line power combiners

[摘要] This dissertation presents a technique for the design of N-way conical line power combiners,which offers significant advantages over existing axially symmetric combining techniques.A full analytical study of conical transmission lines is done, and evaluated results are presented.These include a proof of the cutoff frequency equation, and plots of the field patterns, of higherorder modes which are unavailable in literature.A coaxial fed conical line combiner for 10 inputs is proposed, designed and evaluated. Thedesign technique relies on the uniform transmission line characteristics of the conical lines toeliminate the need for complex full wave optimisation, typically needed in the design of the morecommonly used radial line combiners. Circuit models are instead employed to achieve a widematched bandwidth by using optimised stepped impedance coaxial lines to feed the combiningstructure. The prototype developed at X-band displays more than an octave bandwidth witha return loss of better than -14.5 dB. Using tapered line matching sections increases the powerhandling capability of the combiner by eliminating sharp edges, and allows for tolerance insensitivemanufacture of the structure by widening conductor spacings. Such a 10-way prototypeis developed at X-band which displays a -18.7 dB return loss bandwidth of 47% with very lowlosses.A study is done to determine the limitations on the design of general N-way combiners, andthe results are incorporated into the design technique. The full process is demonstrated bythe design and simulation of a 30-way combiner at Ku-band which displays a simulated -20 dBreturn loss bandwidth of 34%.The design technique is simple to execute and requires very little full wave analysis. Resultsobtained with the manufactured combiners are better than those of any previously publishedaxially symmetric combiners.

[发布机构] Stellenbosch University