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US 4,255,714 AGranted
GaAs Dual-gate FET frequency discriminator
AssigneeRCA Corporation
InventorArye Rosen
Life of this patent
Estimating the term…
Abstract
A microwave frequency discriminator comprising a dual-gate field effect transistor (FET) amplifier, bias circuits and a detector. The FET is biased to produce an output RF signal within a predetermined frequency bandwidth in response to an input RF signal. A limiter provides a substantially constant power level of the input RF signal to the FET. A detector biasing circuit is used to match electronically the output impedance of the FET to the input impedance of the detector. At such impedance conditions a dc output voltage of the detector varies substantially linearly throughout the frequency bandwidth as a function of the frequency of the input RF signal, approximating the characteristic of a frequency discriminator.
Claims10
A microwave frequency discriminator for input RF microwave frequency signals of substantially constant power level comprising:
- a transistor amplifier including a dual-gate field effect transistor having first and second control gate electrodes and input and output electrodes;
- means coupled to said first control gate electrode and said input and output electrodes for separately biasing said electrodes at predetermined bias voltages that produce in response to said input RF signal at said first control gate electrode an output RF signal at said output electrode having a predetermined frequency versus gain roll-off characteristic over a predetermined frequency band;
- means coupled to said second control gate electrode for biasing said second control gate electrode at a predetermined bias voltage in relation to the biasing of said first control gate electrode and said input and output electrodes that produces said output RF signal with a more linear frequency versus gain roll-off characteristic over said predetermined frequency band;
- said first-mentioned biasing means including means coupled to said first control gate electrode for controlling the input impedance of said transistor and means coupled to said output electrode for controlling the output impedance of said transistor, said second-mentioned biasing means including means coupled to said second control gate electrode for further controlling the output impedance of said transistor;
- detector means responsive to said output RF signal for producing a dc signal proportional to the amplitude of said output RF signal;
- and
- detector biasing means coupled to said detector means responsive to a predetermined bias voltage for controlling the input impedance of said detector means so as to provide matching with the output impedance of said transistor;
- whereby at said conditions of matched impedances said dc signal varies substantially linearly as a function of the frequency of said input RF signal.
5 more elements
A microwave frequency discriminator comprising:
- signal limiting means responsive to an input RF signal of varying power level for generating an RF signal of substantially constant power level;
- a transistor amplifier including a dual-gate field effect transistor having first and second control gate electrodes and input and output electrodes;
- means coupled to said limiting means for applying said RF signal of substantially constant power level to said first control gate electrode, means coupled to said first control gate electrode and said input and output electrodes for separately biasing these electrodes at predetermined bias voltages that produce in response to said RF signal of substantially constant power level at said first control gate electrode an output RF signal at said output electrode having a predetermined frequency versus gain roll-off characteristic over a predetermined frequency band;
- means coupled to said second control gate electrode for biasing said second control gate electrode at a predetermined bias voltage in relation to the biasing of said first control gate electrode and said output electrode that produces said output RF signal with a more linear frequency versus gain roll-off characteristic over said predetermined frequency band;
- said first-mentioned biasing means including means coupled to said first control gate electrode for controlling the input impedance of said transistor and means coupled to said output electrode for controlling the output impedance of said transistor, said second-mentioned biasing means including means coupled to said second control gate electrode for further controlling the ouput impedance of said transistor;
- detector means responsive to said output RF signal for producing a dc signal proportional to the amplitude of said output RF signal;
- and
- detector biasing means coupled to said detector means responsive to a predetermined bias voltage for controlling the input impedance of said detector means so as to provide matching with the output impedance of said transistor,
- whereby at said conditions of matched impedances said dc signal varies substantially linearly as a function of the frequency of said input RF signal.
6 more elements
Dependencies are inferred from the claim text.