Performance Enhancement of RF/Microwave Devices Using Filter Synthesis Techniques
Ricardo E. Lovato · Journal of International Crisis and Risk Communication Research · 2021
This dissertation shows that filter synthesis techniques can be used to design and enhance the performance of several discrete components of the RF front-end. Throughout this work, a block diagram of a typical receiver is used to illustrate each component separately. Four main areas are covered: (1) filter/antenna integration, (2) frequency-tunable filter/antenna integration with control of the bandwidth characteristics, (3) antenna arrays designed based on integrated cavity resonators, and (4) novel low-loss phase shifters using band-pass and band-stop filters. The filter/antenna designed using two cavity resonators with a slot antenna in the second cavity. The slot antenna excites two modes in the slot cavity, creating a third-order filtering response while preserving the radiating characteristics. A transmission zero can be arbitrarily placed below or above the passband. Tunable integrated filter/antennas are demonstrated with two coupling configurations that provide design control of the bandwidth performance over the tuning range. The first is a single-layer third-order tunable filter/antenna with increasing fractional bandwidth. The second is a double-layer vertically-integrated third-order tunable filter/antenna that provides constant absolute bandwidth over the tuning range. This design accounts for the frequency-dependent behavior of the antenna radiation Q. The filtering array is designed in substrate integrated waveguide technology and consists of 5 coupled cavities with a 6th-order filtering function. The antenna array is formed with a linear arrangement of four slot antennas in the final cavities which excite two modes in the radiating cavity. A new class of phase shifter based on a bandpass filter with reconfigurable transmission zeros is presented in this work. By using tunable resonators that are extracted from the main signal path, a transmission phase shift is obtained with minimal effect on the insertion loss from the tuning elements. The culmination of this work is a continuously tunable phase shifter designed based on a band-stop filter. A full 360-degree phase range can be continuously tuned while keeping the insertion loss below 2 dB and this is confirmed by designing a beamforming antenna array based on these phase shifters.