General Electric Company

United States of America As Represented by the Secretary of the Air Force

Ying C Hwang

Young K Chen

Louis J Ragonese

John W Lunden

A novel signal scaling MESFET of a segmented dual gate design is disclosed. The MESFET, which is monolithically integrated on a semi-insulating substrate capable of localized surface modification to form active semiconductor regions using MMIC (monolithic microwave integrated circuit) techniques, has a small AC signal transfer which is adjustable in selected discrete steps. For operation in the gigahertz range, the substrate is preferably of gallium arsenide. In applying the MMIC technique, the MESFET, including segment electrodes and segment interconnections, and the electrical connections, signal paths, and passive components connected to the MESFET are formed on the substrate and defined by a photolithographic process. The technique permits reproducable feature definition and very compact minimum reactance segment interconnections, reducing deleterious parasitics and facilitating virtual unitary MESFET operation to very high frequencies. The signal scaling MESFET is an active MESFET subdivided into an n-fold plurality of selectively activated MESFET segments, each of a predetermined width, with dual gates for each segment. The AC input signal is applied to the first gates of all n segments and a DC control potential is selectively applied to the second activating gate of each of the n segments to turn current flow 'ON' or 'OFF' in selected segments. The MESFET transfer values so formed are each substantially constant in a small AC signal sense and successive values are stepped at intervals suitable for linear, trigonometric, logarithmic or arbitrary scaling functions.

Signal scaling MESFET of a segmented dual gate design

A digitally controlled wideband phase shifter is disclosed in which an input signal is resolved into two quadrature related components, the components are scaled in a stepped digital manner in proportion to the sine and cosine of the phase shifting angle, and then recombined to reconstitute a phase shifted replica of the input signal. The scalers are segmented MESFETS of a dual gate design in which each segment, has a predetermined transconductance and may be gated 'ON' or 'OFF' by a control signal to affect the overall transconductance of the scaler, and thereby the scaling factor. The phase shifter is implemented by a monolithic microwave integrated circuit technique in which the preferred substrate material is gallium arsenide, and in which all active device and circuit features are formed on the substrate by a photolithographic process. The phase shifter is adapted to scaling at stepped angles, typically 111/4 or 221/2 degrees, is broadband and is applicable to frequencies ranging from a fraction of a gigahertz to many gigahertz.

Digitally controlled wideband phase shifter

A sensitive and precise detector is described for application in determining the 'Centroid' of the video pulse of a radar return echo. A tunnel diode, connected and biased in a balanced configuration with respect to ground and selected taps on a signal delay line, is the key element of the circuit. The sum and/or difference of the tapped signals are formed in such a manner that a precise zero crossing, corresponding to the 'centroid' of the pulse, may be determined. The special characteristics of the tunnel diode are utilized to achieve additional objects, base line noise immunity, multiple echo self resetting, and high speed-precision response. The tunnel diode is positioned in relation to four (or more) input signals and ground such that with no signal on the delay line, it is biased - at a stable low-current-high-voltage state. An incoming signal causes a series of state changes designed to 'switch' the diode to a second state at the time of zero crossing, resulting in the occurrence of a voltage step which, in turn, causes the differential amplifier connected to the tunnel diode to also change state - with amplification.

Growing community of inventors

Liverpool, NY, United States of America

Ying C Hwang