| With the modern increase in the need of wireless applications such as GPS, WLAN, SAR, LMDS, Bluetooth, and PCS, the RF (radio frequency) bands are getting to be congested. Accordingly, higher frequency bands are being explored. At RF frequencies power combining is achieved by transmission line (TL) circuitry to feed and combine the power from an array of solid-state devices. In this thesis a novel coplanar waveguide (CPW) based two dimensional slab beam quasi-optical power combiner to operate at 30 GHz is developed. As the name implies the power is being combined in a slab instead of TL circuitry, and hence eliminate all the losses and complexities associated with the TL-based power combiners. The new power combiner integrates several passive and active components.; First, a new class of CPW-fed slot launchers to excite a directed dominant transverse magnetic surface wave (TM 0) in the grounded slab guiding structure is investigated. The developed launcher configurations include director-based launchers, reflector-based launchers, and finally a combination of both reflector and director-based configurations.; The active devices need to be integrated with a new antenna and to fit with the CPW technology used. This means special considerations in terms of stability and compactness in the design have to be taken care of. Thus a new technique to achieve all-band unconditional stability for the MESFET transistor is presented. This eliminates any possibility of pushing the transistor into oscillations, from DC until the transistor cutoff frequency, under any probable variation in the transistor loads (antennas in this case) which could result in loss of power at frequencies other than the design frequency. This newly introduced feedback network also extends the range of operation of the active device over what is presently available without affecting the achievable gain, and hence provides a considerable improvement on previous work.; The final step is to direct the power from the dielectric slab into radiated beam waves. For this a new dielectric grating millimeter leaky wave antenna is investigated and implemented. While dielectric grating structures have been used in integrated optics, this is the first implementation of this type of antenna at millimeter-wave frequencies. (Abstract shortened by UMI.)... |
