Continuously-variable monolithic rf and microwave analog delay lines

Abstract

The use of one or more multi-gate (e.g., dual-gate) FETs are employed in an RF or microwave delay line. The carrier drift velocity in each multi-gate FET is controlled in accordance with the variable magnitude of a delay-control voltage applied between its drain and source, thereby controlling the time delay experienced by an RF or microwave signal traveling between spaced first and second gates of a multi-gate FET. The gates of a plurality of multi-gate FETs may be serially-coupled through amplifying circuits to produce a delay chain in which the total delay is the sum of the delays of all the multi-gate FETs in the chain. A single delay-control voltage, which can be continuously variable, may be used to control the total delay provided by all multi-gate FETs in the chain. Alternatively, a separate delay-control voltage, which can be independently continuously variable, may be used for independently controlling the delay provided by each individual multi-gate FET in the chain. RF and microwave analog delay lines are useful in such apparatus as difference-in-time-of-arrival direction finders and transversal filters, by way of example.