Title :
Wideband reflection type MMIC attenuator with constant phase
Author :
Nam, S. ; Ashtiani, A.E. ; Oztek-Yerli, C.F. ; Robertson, I.D.
Author_Institution :
Dept. of Electron. Eng., King´´s Coll., London, UK
fDate :
1/8/1998 12:00:00 AM
Abstract :
A method for reducing the unwanted insertion phase variation in an MMIC reflection type attenuator with wide bandwidth (>20 GHz) is described. The analogue reflection type amplitude control circuit uses cold-FETs as variable resistance reflection terminations. At high frequencies, very high phase variation is unavoidable due to the parasitic voltage-dependent reactance. Instead of tuning-out the parasitic reactance of the cold-FET, a novel symmetrical control method is presented for a two-stage attenuator. The phase shift variations from each stage cancel each other by the use of `complementary´ control signals
Keywords :
field effect MMIC; waveguide attenuators; amplitude control circuit; cold-FETs; complementary control signals; constant phase; parasitic voltage-dependent reactance; phase shift variations; phase variation; reflection type MMIC attenuator; symmetrical control method; two-stage attenuator; unwanted insertion phase variation; variable resistance reflection terminations;
Journal_Title :
Electronics Letters
DOI :
10.1049/el:19980071