This dissertation covers a variety of topics. The two main areas of study are terrestrial circularly polarized (CP) rectenna arrays and radio frequency identification (RFID) tags. Some focus has also been given to the development of dual-frequency diplexers, and various microstrip, stripline, and coplanar stripline filters.; The CP high gain, high-efficiency rectifying antenna (rectenna) array is designed in a coplanar stripline circuit. The single element rectenna achieves 81% RF-to-DC conversion efficiency at 5.71 GHz and uses a coplanar stripline (CPS) band-reject filter (BRF) to suppress the re-radiated harmonics by more than 19 dB. At 5.61 GHz, using an array loading of 150 Ω, a 3 x 3 rectenna array produces 0.86 W of DC output power with an RF-to-DC conversion efficiency of 78% and an axial ratio of 0.25 dB for an incident circularly polarized power density of 7.6 mW/cm2.; The passive 5.8 GHz Radio Frequency Identification (RFID) backscatter tag proposed for monitoring oil drill pipe is to be inserted into the tool joint of the drill pipe in order to predict the pipe's lifetime and to provide inventory control. The tag requires a minimal incident power density of 13.5 mW/cm2 to establish a link and transmit 64-bit coded information to the interrogating reader. The tag's physical size has to be small so that it can be imbedded into the pipe without weakening the structure.; A three-port microstrip multi-frequency diplexer is designed to take 10, 12, 19, and 21 GHz into port one and to separate 10 and 19 GHz to port two and 12 and 21 GHz to port three with minimal dispersion. The insertion loss for each frequency varies from 0.4 dB to 3.4 dB, and the return loss is better than 10 dB. The isolation between channels at the four frequencies is greater than 50 dB.; A new low-loss dc-blocking parallel-cascaded bandpass filter is also presented. The filter is much easier to use and fabricate, more compact, and simpler to design than the conventional end-coupled or parallel-coupled line filters. The filter has a wide passband with a 2:1 VSWR bandwidth of around 10% and an insertion loss of 0.5 dB at 10 GHz.
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