Novel Hardware Systems and Signal Processing Techniques for Propagation Measurement in IoT, Microwave and mmWave Channels

Wireless communication systems rely on the radio channel. The characteristics of each channel define the limiting performance of the communications system, and so must be understood. This requires accurate measurement equipment to sound the channel in representative scenarios. Channel Sounders are themselves radio systems, thus benefitting from advances in RF engineering and signal processing.
This thesis by publication encompasses six novel, relevant, published works: contributing three portable channel sounders with field test results, and three RF systems applicable in sounders.
High performance, portable sounders for VHF / UHF and 28 GHz are created and subsequently used in novel use cases to elicit new channel propagation models. The VHF / UHF sounder had a measurement floor of -130 dBm. In suburban settings, it showed channel reflection delays did not exceed 1 μs over 4 km. The 28 GHz sounder had a path loss measurement capability of 139 dB, and over 1km identified that near-ground, line-of-sight, path losses approximate free space.
Predicting the RF performance and power efficiency of downconversion mixers is vital in system design. A novel technique to predict the relationship between DC bias and local oscillator power is identified and related to RF mixer gain and linearity. The techniques predict conversion gain within 2.5 dB of measured PCB results at 26 GHz.
Three new works contribute to Time Modulated Arrays (TMAs). Cancellation of a non-steerable beam is the contribution of one work: achieving measured array gains within 1 dB of theory at 5.8 GHz. A receiving TMA is also created, uncovering a novel technique to combine TMA beam steering and subsampling– named the Subsampling TMA (STMA), with measured array gain within circa 2 dB of prediction. Finally, a 5.8 GHz channel sounder using a transmitting TMA is introduced - using a new signal processing approach enabling concurrent, time aligned, angle of departure channel measurements. The sounder measurement floor was -120 dBm.