AN AUTOMATIC IMPEDANCE MATCHER.
Interim rept. no. 1,
ELECTROMAGNETIC RESEARCH CORP WASHINGTON D C
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An automatic impedance matcher has been designed to electronically tune a re-entry slot antenna to compensate for the detuning caused by the formation of the plasma sheath around the vehicle. The impedance matcher utilizes a phase-sensitive detection circuit which determines the magnitude and phase of the standing wave on the transmis sion line feeding the antenna. The output of this detector controls the voltage across a ferroelectric element whose capacitance is a function of this applied voltage. Two ferroelectric elements are used in the matcher, one in the antenna slot and one across the transmission line feeding the antenna. With this combination a VSWR of 30 or more can be adjusted electronically within milliseconds to a VSWR of 2 or less. Author