High power, low frequency, electronically adjustable attenuator
AssigneeRCA Corporation
InventorAlfred Schwarzmann
Life of this patent
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Abstract
An attenuator for high-power, low frequency RF signals including two .pi.-section low-pass filters is well matched to the transmission line characteristic impedance. Each of the four loss branches of the attenuator includes a power resistor and a PIN diode. The attenuator is made electronically variable by controlling the dc bias across the PIN diodes, which respond to increased voltage by exhibiting lowered resistance. At any setting of the dc bias, only a fraction of the attenuated RF power is dissipated by the diodes. When the bias voltage is tuned for high attenuation, virtually all of the power is dissipated by the power resistors.
Claims3
An apparatus for attenuating a high-power radio frequency (RF) signal comprising:
- two low-pass filters in cascade combination, each of said filters having at least one low frequency pass element as its series branch and at least one high frequency pass element as its shunt branch, said combination having an input terminal for applying said RF signal and an output terminal;
- at least two loss elements connected respectively in parallel with each of said shunt branches, each of said loss elements comprising fixed resistance means of the high-power dissipation type in series with current-dependent resistance means responding to increased current flow therethrough to exhibit lowered resistance;
- and
- means for applying substantially equal dc bias currents through said loss elements to thereby provide loss paths for said RF signal in which the power losses are proportional to said dc bias currents.
Dependencies are inferred from the claim text.