Monitoring and control of evanescent-mode cavity filters

With the ever increasing demand on wireless technologies, communication devices are being overloaded with a variety of wireless standards. In order to achieve better performance, and better spectrum efficiency, many modern and evolving standards operate over several bands in the frequency spectrum.Such multi-band operation makes designing RF front-ends a challenging task. Conventional solutions, such as placing RF switches between antennas and a bank of filters, are not scalable since switches degrade RF performance, and the large number of filters (~ 10s in today\u27s mobile phones) can consume larger area. As a result, there have been significant research efforts recently on designing high-performance tunable and adaptable RF front-ends, especially for RF filters, since they can affect the performance of the whole system. Amongst several tunable technologies, evanescent-mode cavity filters have shown feasible advantages compared to competing technologies in terms of tuning range, quality factor (Q), and power consumption. Those advantages inspired many novel implementations for highly adaptive RF front-ends. Evanescent-mode cavity filters, however, have few limitations that affect their reliability and long-term use. The objective of this dissertation is to present solutions and mitigation techniques for those limitations to further advance the feasibility of evanescent-mode cavity filters. First, a vibration mitigation technique is presented. Since evanescent-mode cavity filters are sensitive to mechanical perturbation, the presented technique senses the vibration, and then modifies a tuning signal such that it counteracts the effect from vibration. Measurements show that the effect of vibrations, in terms of sidebands, is suppressed by 24-26 dB. Then, two monitoring and control techniques are introduced and experimentally validated. Both of which can operate with spectrum-aware capabilities. The presented systems read the frequency of the filter, and compensates the tuning signal such that the frequency is tuned to, and maintained at, the target operating frequency. The monitoring and control systems are applied to a variety of filter setups. The systems also show the capability of locating a jammer in the spectrum and suppressing it in real time by up to 45 dB. A tuning resolution 0.05% is achieved. Lastly, a variable-output high-voltage charge pump is presented. This novel modified Dickson charge pump can provide the required tuning voltage for the evanescent-mode cavity filters from a low voltage source, with minimum cost, area, and power overhead. The output voltage is virtually continuous, while it is controlled from a digital input for easier input