| dc.description.abstract | In this study, we focus on ALMA (Atacama Large Millimeter/Submillimeter Array) Band-1 receiver front-end passive circuit design. First block of receiver is circular horn antenna, the second block is the orthomode transducer which could split the radio signal into two orthogonal signal, third block is bandpass filter which could block the lower side mirror signal, the fourth block is absorptive bandstop filter which could solve LO-to-RF leakage signal problem, and the final block is mixer which could down convert RF signal to intermediate frequency.
First, carrying on the past studies, we select trisection as our bandpass filter main structure. This structure could provide a transmission zero to enhance selectivity in lower side and has advantage of small cell size. We could fabricate on GaAs process to improve system integration.
Second, we select couple line as main structure of bandstop filter and introduce proper resistance which could absorb the reflection signal in stopband effectively to achieve absorptive stopband. We fabricate this circuit in GaAs process.
Eventually, we could provide more refined and more accurate process than before with improvement of fabrication technique so that we could use smooth curve line to design our Double-Ridge Junction, 90-degree Bend-plane and Power Combiner of OMT. In this study, we provide a proper design process to design OMT application for Q-band and select metal Al as our fabrication material finally.
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