mm-Wave Waveguide Traveling-Wave Power Combiner Design Using an Equivalent Circuit Model

Abstract

The waveguide traveling-wave power combiner (WTWPC) falls into the category of asymmetrical non-isolated power combiners, and, therefore, the active load modulation occurring within the combiner was investigated. Proper manipulation of active load modulation gave rise to a two-step design method for the combiner. The first step formulated the specifications of the combiner in terms of active load impedance at its input ports, which determined the objective scattering parameters of the combiner, as well as the desired coherent excitation signals. The second step established a versatile equivalent circuit model to provide a mapping relation between the scattering parameters and the physical dimensions of the combiner. The proposed equivalent circuit method not only offered a close-to-reality description of the existing type of traveling-wave power combiners but also broke new ground for combiner variants that accommodate the more general driving amplifiers. A Q-band quasi-planar traveling-wave waveguide spatial combined amplifier was built to demonstrate the proposed method. The measured P −1dB bandwidth of the prototype was 6 GHz (33-39 GHz). INDEX TERMS Equivalent circuit, load modulation, traveling wave, mm-wave power amplifier, rectangular waveguide, waveguide probe, waveguide iris window.

3D Smith Chart Constant Quality Factor Semi-Circles Contours for Positive and Negative Resistance Circuits

“…the  r axis. We consider that the distance between two constant Q-circles is given by the distance between their intersections with  i axis (7), then the distance between two consecutives circles is given in Table I. Fig.…”

“…The Smith chart [1][2], which, was invented by Philip Hagar Smith in 1939, has survived the passing of years, becoming an icon of microwave engineering [3]. It is still being used in the design and measurement stage of various radio frequency or microwave range devices [4][5][6][7], for plotting a variety of frequency dependent parameters. Constant quality factor (Q) representations on the Smith chart are a visual way to determine the quality factor of various passive microwave circuits, being mostly known in the microwave frequency range community [8][9][10][11][12][13][14][15][16][17].…”

Efficient waveguide power combiners at mm‐wave frequencies

“…More compact combiners have been proposed [6][7][8], based on parallel or series combination, but their operation is restricted by factors such as impedance variation with number of elements, narrow bandwidth and limited impedance transformation. Waveguidebased power combiners were presented in [9][10][11][12][13][14][15][16]. An important advantage of this type of structures, with respect to Wilkinson or transformer based combiners, is that the insertion losses do not increase with the number of feeds, thus resulting in efficient power combiners if a large number of PAs is needed to meet the required output power.…”