Wideband Balun design for the pyramidal sinuous antenna

Johnston, Michael (2019-04)

Thesis (MEng)--Stellenbosch University, 2019.

Thesis

ENGLISH ABSTRACT: This thesis presents the design of wideband baluns for integration with the pyramidal sinuous antenna. Two different realizations of the Marchand balun are studied, namely a planar coupled-line balun and a rectangular coaxial balun. The planar balun implementation makes use of ground plane apertures to enhance the coupling coeficient of the coupled-line sections, so that higher bandwidths can be achieved compared to standard implementations. It is designed to be able to accommodate a single or dual-linearly polarized sinuous antenna. The designed prototype displays a bandwidth ratio of 3:1 with a 50-300 single-ended to differential impedance transformation. The simulated return loss is better than 10 dB, and the simulated insertion loss is better than 0.84 dB. The amplitude balance is better than ±0.2 dB across most of the band, and the phase balance is better than ±2° across half the band. The performance of the manufactured prototype is shown to be consistent with simulated predictions. The coaxial implementation makes use of a shunted resonate line to provide frequency independent unbalanced current cancellation, and is able to achieve a bandwidth ratio of about 5:1 with a 50-300 singled-ended to differential impedance transformation. The return loss of the final coaxial design is better than 10 dB with an insertion loss better than 0.91 dB. The amplitude balance is better than ±0.2 dB and the phase balance is better than ±1.5° across the entire band. The performance of the manufactured prototype did not agree with simulated predictions and therefore a short follow-up study is conducted explaining the differing results. Performance of the prototype baluns is further veri ed through simulated integration with the single-linearly polarized pyramidal sinuous antenna. Both balun implementations integrate with the antenna in a straightforward manner with relatively small re ections. Reasonably symmetric radiation patterns are achieved for the planar integration with some variation in the reported gain at broadside. Symmetric radiation patterns are also achieved across the band for the coaxial integration, but better consistency is reported for the gain at broadside.

AFRIKAANSE OPSOMMING: Hierdie tesis ondersoek die ontwerp van breëband baluns vir integrasie met die piramidale sinuous antenna. Twee verskillende realiserings van die Marchand balun word bestudeer, naamlik `n planêre gekoppelde lyn balun en `n reghoekige koaksiale balun. Die implementering van die planêre balun maak gebruik van slote op die grondvlak om die koppeling koësiënt van die gekoppelde lyn seksies te versterk. Hoër bandwydtes kan met hierdie implementering bereik word, in vergelyking met standaard implementerings. Dit word ontwerp om `n enkel of duale-liniére gepolariseerde sinuous antenna te akkommodeer. Die ontwerpte prototipe toon `n bandwydte ratio van 3:1 met `n enkel-einde tot differensiële impedansie transformasie van 50-300 . Die gesimuleerde terugkeer verlies is beter as 10 dB, en die gesimuleerde invoer verlies is beter as 0.84 dB. Die amplitude balans is beter as ±0.2 dB oor die meerderheid van die band, en die fase balans is beter as ±2° oor die helfte van die band. Daar word getoon dat die effektiwiteit van die vervaardigde prototipe konsekwent is met gesimuleerde voorspellings. Die koaksiale implementering maak gebruik van `n afgetakte resonante lyn om frekwensieonafhanklike kansellasie van ongebalanseerde stroom te verseker. Die implementering kan ook `n bandwydte ratio van omtrent 5:1 bereik met `n 50-300 enkel-einde tot differensile impedansie transformasie. Die terugkeer verlies van die finale koaksiale ontwerp is beter as 10 dB met `n invoer verlies wat beter is as 0.91 dB. Die amplitude balans is beter as ±0.2 dB en die fase balans is beter as ±1.5° oor die totale bandwydte. Die effektiwiteit van die vervaardigde prototipe het nie ooreengestem met die gesimuleerde voorspellings nie en om hierdie rede word `n kort opvolgstudie onderneem om die verskil in resultate te ondersoek. Die e ektiwiteit van die prototipe baluns word verder geveri eer deur gesimuleerde integrasie met die enkel-lini^ere gepolariseerde piramidale sinuous antenna. Beide balun implementerings integreer met die antenna op `n eenvoudige wyse met relatief min re- eksie. Redelike simmetriese stralingspatrone word bereik met die plan^ere integrasie met `n mate van variasie in die gerapporteerde verhoging in die vertikale as. Simmetriese stralingspatrone word ook bereik regoor die band vir die koaksiale integrasie, maar groter konsekwentheid word rapporteer vir die verhoging in die vertikale as.

Please refer to this item in SUNScholar by using the following persistent URL: http://hdl.handle.net/10019.1/106015
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