abstract: Microwave circuits are an essential part of technology in the modern day. Everything from cell phone communications, television and radio reception, medical imaging, and radar surveillance depend on microwave circuitry. Constant efforts are being made to introduce new methods of implementing more efficient microwave circuitry while maintaining well known fabrication methods. These improvements typically focus on lower loss, smaller size, and higher operating frequencies [1-6]. This thesis will focus on the specific application of a planar orthomode transducer (OMT) in Home Direct Broadcast (DBS) Systems used in residential satellite receivers. The need for low-loss circuitry becomes increasingly important in the realm of satellite reception, as the carrier to noise levels at the receiver can be as low as 10dB [7]. Interference and loss of signal integrity can occur very easily if the receiving network is not properly designed. This thesis will investigate the design of a planar transmission media that produces ultra-low losses when compared to more conventional planar transmission media. This design, which is called Double Sided Suspended Stripline (DSSL), utilizes air as its primary propagation medium. The design will be similar to standard suspended stripline in geometry, but has signal traces on the top and bottom of the substrate. The traces are connected using plated through-hole vias. This geometry is hugely beneficial because it virtually eliminates one of the major loss mechanisms in classical microwave structures: dielectric loss. This thesis will focus mainly on empirically derived equations and performance metrics obtained through rigorous simulation. / Dissertation/Thesis / Masters Thesis Electrical Engineering 2019

Receiver systems utilising planar technologies are prevalent in telescopes observing at radio to sub-millimetre wavelengths. Receiver components using planar technologies are generally smaller, have reduced mass and are cheaper to manufacture than waveguide-based alternatives. Given that modern-day detectors are capable of reaching the fundamental photon noise limit, increases in the sensitivity of telescopes are frequently attained by increasing the total number of detectors in the receivers. The development of components utilising planar technologies facilitates the demand for large numbers of detectors, whilst minimising the size, mass and manufacturing cost of the receiver. After a review and study of existing concepts in radio to sub-mm telescopes and their receivers, this thesis develops planar components that couple the radiation from the telescope's optics onto the focal plane. Two components are developed; a W- band (75-110 GHz) planar antenna-coupled flat mesh lens designed for the receiver of a Cosmic Microwave Background (CMB) B-mode experiment, and an L-band (1- 2 GHz) horn-coupled planar orthomode transducer designed for the receiver of the FAST telescope. The first developments of a planar antenna-coupled flat mesh lens are presented. The design is driven by the requirement to mitigate beam systematics to prevent pollution of the CMB B-mode signal. In the first instance, a waveguide-coupled mesh lens is characterised. The radiation patterns of the waveguide-coupled mesh lens have -3 dB beam widths between 26 and 19 degrees, beam ellipticity <10%, and cross-polarisation.