Compact multi-layer microstrip Rotman lens design using coupling slots to support millimetre wave devices

Millimetre wave technology is now considered as a key component for the next generation (5G) of cellular networks since they offer higher data rates and broader bandwidth compared to the current technology. However, since communication in this frequency band suffers higher propagation loss and atmospheric absorption (approximate to 12dB/km), the use of highly directional antennas plays an important role in order to compensate for these losses. Therefore, it is necessary to design beamforming networks that are not only able to support these antennas but also offer practical and compact solutions to be placed in any modern transceiver system. Rotman lenses have long been used as analogue beamforming networks to support linear array antennas for electronic scanning. Their broad bandwidth and planar structure make them ideal for these types of applications. However, their overall dimensions can be prohibitively large, especially for systems requiring large scan angles. In this study, the authors propose a new compact configuration that reduces the overall dimensions of the conventional Rotman lens by as much as 50% without degrading its performance.