Oscilirajuće antene s jednim i više aktivnih elemenata : doktorska disertacija - Bonefačić, Davor; Bartolić, Juraj (Zagreb : D. Bonefačić ; Fakultet elektrotehnike i računarstva, 2000)
U radu su predložene i pokusima ispitane dvije nove izvedbe oscilirajućih antena. Kod prve su izvedbe tranzistorski oscilator s negativnim otporom i linijski transformator impedancije ugrađeni u pravokutni otvor unutar pravokutne patch-antene. Primjena linijskog transformatora impedancije, spojenog između oscilatora i antene, omogućila je postizanje odgovarajuće prilagodbe impedancije za početak oscilacija i stabilan rad oscilirajuće antene. Izmjerena je promjena frekvencije i zračene snage s naponom napajanja. Promjena frekvencije bila je vrlo linearna. Izmjereni dijagrami zračenja osnovne polarizacije u ravninama E i H bili su simetrični. U obje su ravnine izmjerene niske razine križne polarizacije. U cijelom području ugađanja frekvencije spektar je bio čist, a rad antene bio je stabilan. Dvije ovakve antene združene su u antenski niz u ravninama E i H. Za oba je niza postignuto simetrično zakretanje snopa ugađanjem napona napajanja oscilirajućih antena. Postignuta je visoka djelotvornost prostornog slaganja snage. Kod druge je predložene izvedbe protutaktni oscilator ugrađen u pravokutni otvor unutar pravokutne patch-antene. Prilagodba impedancije između oscilatora i antene ostvarena je odabirom izmjera pravokutnog otvora. Antena je pobuđena u dvije simetrične točke na osi simetrije uzduž rezonantne izmjere. Primjenom protutaktnog oscilatora s dva tranzistora povećana je zračena snaga antene. Predložen je i ispitan način potiskivanja neželjenih modova rada oscilirajuće antene. Izmjerena promjena frekvencije s naponom napajanja bila je linearna. U cijelom području ugađanja frekvencije spektar je bio čist, a rad oscilirajuće antene bio je stabilan. Izmjereni dijagrami zračenja osnovne polarizacije u ravninama E i H nisu bili narušeni preinakama u patchanteni i sklopom oscilatora. U obje su ravnine simetričnom pobudom antene i simetričnom izvedbom protutaktnog oscilatora postignute niske razine križne polarizacije. Ova je oscilirajuća antena združena u niz od dva elementa u ravnini H te u nizove od dva, tri i četiri elementa u ravnini E. Za sva je četiri niza postignut stabilan rad i simetrično zakretanje glavnog snopa zračenja ugađanjem napona napajanja oscilirajućih antena. Svi su nizovi imali čist spektar i pokazali su vrlo dobru djelotvornost slaganja snage Na osnovi provedene teorijske analize, proračuna i mjerenja utvrđeno je da su kod obje predložene izvedbe oscilirajućih antena zadržane male izmjere i da osobine zračenja nisu narušene preinakama u elementima zračenja i sklopovima oscilatora.
Ključne riječi:
antena, aktivna antena, aktivna integrirana antena, oscilator, protutaktni oscilator, prostorni oscilator, antenski niz, aktivni niz, prostorno slaganje snage, zakretanje snopa zračenja
In this work, two novel oscillating antennas were proposed and experimentally tested. The first oscillating antenna was realized by integrating a negative resistance transistor oscillator and a line impedance transformer inside a rectangular opening in a rectangular patch antenna. The line impedance transformer, connected between the oscillator and the patch, allowed suitable impedance matching for oscillation start-up and stable operation of the oscillating antenna. The changes of the operating frequency and of the radiated power with dc bias voltage were measured. The change of the operating frequency was very linear. The measured co-polarization radiation patterns in E and H planes were symmetrical. The measured cross-polarization levels in both planes were low. This oscillating antenna showed clean spectrum and stable operation in the whole bias voltage tuning range. Two of these antennas were integrated in arrays in E and H planes. Symmetrical beam scanning was obtained for both arrays by adjusting the dc bias voltages of the oscillating antennas. The obtained efficiency of spatial power combining was high. The second oscillating antenna was constructed by embedding a pushpull oscillator inside a rectangular opening in a rectangular patch antenna. Suitable impedance matching between the oscillator and the patch was achieved by choosing the dimensions of the rectangular opening. The patch antenna was excited in two symmetrical points on the line of symmetry along the resonant dimension. By using the push-pull oscillators with two transistors the power, radiated by the antenna, was increased. A method for suppressing undesired operating modes of the oscillating antenna was proposed and experimentally verified. The measured change of the operating frequency with bias voltage was linear. In the whole bias voltage tuning range the antenna showed clean spectrum and stable operation. The measured co-polarization radiation patterns in E and H planes were not affected by the modifications in the patch and by the oscillator circuit. Symmetrical antenna excitation and symmetrical design of the push-pull oscillator resulted in low cross-polarization levels in both planes. This antenna was integrated in a two-element array in H plane and in two-, three-, and four-element arrays in E plane. All four arrays showed stable operation and symmetrical beam scanning was obtained by adjusting the bias voltages of the oscillating antennas. All arrays had clean spectrum and showed very good efficiency of spatial power combining. The theoretical analysis, calculated and measured results confirmed that both proposed oscillating antennas maintained small dimensions and that their radiation properties were not affected by the modifications of the patch antennas and by the oscillator circuits.
Key words:
antenna, active antenna, active integrated antenna, oscillator, push-pull oscillator, spatial oscillator, antenna array, active array, spatial power combining, beam scanning
Bibliografija str. 195-215.