A double-sided planar transmission medium design for ultra-low loss planar orthomode transducers

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.