G.P. Monahan

Demonstration of an oscillating quasi-optical slab power combiner

Power combining in a hybrid dielectric slab beam waveguide resonator using a MESFET oscillator array is reported for the first time. Four MESFET oscillators lock via quasi-optical modes to produce a signal at 7.4 GHz with a 3 dB linewidth of less than 3 kHz.<<ETX>>

Full-wave analysis of quasi-optical structures

A full-wave moment method implementation, using a combination of spatial and spectral domains, is developed for the analysis of quasi-optical systems. An electric field dyadic Greens function, including resonant and nonresonant terms corresponding to coupling from modal and nonmodal fields, is employed in a Galerkin routine. The dyadic Greens function is derived by separately considering paraxial and nonparaxial fields and is much easier to develop than a mixed, scalar and vector, potential Greens function. The driving point impedance of several antenna elements in a quasi-optical open cavity resonator and a 3/spl times/3 grid in free space are computed and compared with measurements.

A dielectric slab waveguide with four planar power amplifiers

A hybrid dielectric slab beam waveguide with four MESFET amplifiers employing quasi-optical power combining is reported for the first time. Up to 10 dB power gain is obtained at 7.4 GHz. Measurements for power gain, amplifier gain, insertion loss and transverse power distribution are presented. The fabrication technique employed is suitable for planar MMIC circuits.<<ETX>>

Impedance matrix of an antenna array in a quasi-optical resonator

The power from numerous millimeter-wave solid-state sources can be efficiently combined using quasi-optical techniques. One technique is to place an array of active radiating sources within a quasi-optical resonator. The driving point impedance of each antenna is strongly affected by the presence of all other active antennas as well as by the mode structure and Q of the resonator. The impedance matrix for an array of antennas radiating into a plano-concave open resonator is determined here through use of the Lorentz integral. The resulting expressions include the effect of diffraction loss and are valid for arbitrary reflector spacing, source frequency, array location and geometry. The result can be used for impedance matching of each active source to its antenna, facilitating design of an efficient power combining system. Simulations using the impedance matrix in conjunction with an antenna impedance model are compared with two-port measurements. >

A dyadic Green's function for the plano-concave quasi-optical resonator

An approximate dyadic Greens function is derived for a quasi-optical resonator. The Greens function is comprised of resonant and nonresonant terms corresponding to coupling of the modal and nonmodal resonator fields. The effect of losses due to diffraction, finite reflector conductivity and radiation are included. Experimental one- and two-port measurements of antennas in an X-band cavity compare favorably with theoretical predictions.<<ETX>>

Experimental investigation of a quasi-optical slab resonator

A quasi-optical slab resonator for TE modes was experimentally characterized to demonstrate a planar technology for quasi-optical devices. Predicted and measured frequencies of resonance of the TE slab modes and electric field profiles are in close agreement.<<ETX>>

Use of the moment method and dyadic Green's functions in the analysis of quasi-optical structures

A moment method using a dyadic Greens function is developed for the analysis of quasi-optical systems. The dyadic Greens function used has separate terms for the paraxial and non-paraxial fields and is much easier to develop than a mixed potential Greens function. The method is applied to the analysis of antenna elements in a quasi-optical resonator.<<ETX>>

Circuit level modeling of quasioptical power combining open cavities

A multiport circuit level model is developed for an open-cavity, quasioptical power combiner. The model is developed using Hermite-Gaussian beam model theory, the Lorentz reciprocity theorem, and the determination of diffraction losses. Measurements were made using an electrically short inverted L antenna. One-port and two-port measurements were made for specified modes for the q=35 family and found to compare very well with simulated results.<<ETX>>