Thesis (PhD (Electrical and Electronic Engineering))--University of Stellenbosch. / ENGLISH ABSTRACT: This dissertation presents a synthesis method for broadband high-power absorptive microwave
lters by cascading a wide stop-band wa e-iron lter with an absorptive harmonic
pad.
The classical image impedance synthesis methods for wa e-iron lters are updated to
allow for non-uniform boss patterns, which enable control over both the stop-band attenuation
and pass-band re
ection of the lter. By optimising an accurate circuit model
equivalent, computationally intensive numerical EM optimisation are avoided. The nonuniform
wa e-iron lter achieves the same electrical speci cation as similar lters in
literature, but in a smaller form factor. The prototype presented displays less than -21
dB in-band re
ection over 8.5 - 10.5 GHz, with stop-band attenuation in excess of 50 dB
over the harmonic bands 17 - 31.5 GHz and 30 dB over the 34 - 42 GHz. The prototype is
designed to handling 4 kW peak power incident in the transmitted band, and is 130 mm in
length. Minimal full-wave tuning is required post-synthesis, and good agreement is found
between synthesised and measured responses. Additionally, a completely novel oblique
wa e-iron boss pattern is proposed.
For the absorptive harmonic pad, transversal broadwall slots in rectangular waveguide,
coupling to an absorptive auxiliary guide, are investigated in the presence of standing
wave surface current distributions. An accurate circuit model description of the cascaded
structure is developed, and optimised to provide a required level of input match in the
presence of an arbitrary re
ective lter. Using numerical port parameter data of the wa eiron
lter, a harmonic pad is developed that provides -12.5 dB input re
ection match
across the band 17 - 21 GHz with up to 1 kW peak incident power handling capability,
yet is only 33 mm in length. Again, good agreement is found between synthesised and
measured responses of the cascaded structure. / AFRIKAANSE OPSOMMING: Hierdie proefskrif stel 'n sintesetegniek voor vir wyeband, ho edrywing absorberende mikrogol
lters deur 'n kaskade kombinasie van 'n verlieslose wafelyster lter met 'n wye stopband,
en 'n absorberende harmoniekdemper.
Die klassieke sintesemetodes vir wafelyster lters word aangepas om nie-uniforme tandpatrone
toe te laat, wat beheer oor beide die lter se stopband attenuasie en deurlaatband
weerkaatsing moontlik maak. Deur die optimering van 'n akkurate stroombaanmodel
van die lter kan berekeningsintensiewe numeriese EM optimering vermy word. Die nieuniforme
wafelyster lter behaal dieselfde spesi kasies as soortgelyke gepubliseerde lters,
maar is meer kompak. Die vervaardigingsprototipe handhaaf minder as -21 dB intreeweerkaatsing
oor die deurlaatband van 8.5 - 10.5 GHz, asook attenuasie van meer as 50
dB oor die stopband 17 - 31.5 GHz en 30 dB oor 34 - 42 GHz. Die prototipe is ontwerp
om 4 kW intree kruindrywing te hanteer in die deurlaatband, en is 130 mm lank.
Die metode vereis minimale verstellings tydens volgolf simulasie, en die meetresultate
stem goed ooreen met die gesintetiseerde gedrag. 'n Nuwe skuinstandpatroon word ook
voorgestel vir wafelyster lters.
Vir die harmoniekdemper word transversale bre ewandgleuwe in reghoekige gol
eier wat
koppel na 'n absorberende newegol
eier ondersoek in die teenwoordigheid van staandegolfpatrone
in oppervlakstroom. 'n Akkurate stroombaanmodel van 'n gleufkaskade word
ontwikkel, en geoptimeer om 'n vereiste intreeweerkaatsing te bewerkstellig in samewerking
met 'n arbitr^ere weerkaatsende lter. Deur gebruik te maak van poortparameterdata
van die wafelyster lter word 'n 33 mm lange hamoniekdemper ontwikkel wat 'n maksimum
intreeweerkaatsing van -12.5 dB oor die band 17 - 21 GHz handhaaf vir kruindrywingsvlakke
van tot 1 kW. Goeie ooreenstemming tussen gesintetiseerde en gemete resultate
word weereens waargeneem vir die volledige saamgestelde struktuur.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:sun/oai:scholar.sun.ac.za:10019.1/1157 |
| Date | 12 1900 |
| Creators | Stander, Tinus |
| Contributors | Meyer, P., University of Stellenbosch. Faculty of Engineering. Dept. of Electrical and Electronic Engineering., University of Stellenbosch. Faculty of Engineering. Dept. of Electrical and Electronic Engineering. |
| Publisher | Stellenbosch : University of Stellenbosch |
| Source Sets | South African National ETD Portal |
| Language | English |
| Detected Language | English |
| Type | Thesis |
| Rights | University of Stellenbosch |
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