David C Helms

US Patent:

49471368, Aug 7, 1990

Filed:

Sep 18, 1989

Appl. No.:

7/408678

Inventors:

David R. Helms - Liverpool NY

Assignee:

General Electric Company - Syracuse NY

International Classification:

H03F 360

US Classification:

330 54

Abstract:

The invention relates to a variable gain distributed amplifier for use at microwave frequencies, and fabricated in a monolithic microwave integrated circuit format. In the amplifier, the attenuation is varied, based upon digital control of a dual gate segmented FET. The amplifier has a nearly flat insertion phase and amplitude response, and an insertion phase response that varies only slightly between gain settings. The amplifier employs segmented dual gate field effect transistors as the gain elements, having their signal input and signal output electrodes which provide shunt capacities (C. sub. G1S, C. sub. DS) interconnected with serial inductances to form separate low pass transmission lines having relatively high cut-off frequencies. The amplifier has means to insure stability and uses Chebyshef equal ripple techniques to linearize the amplitude and insertion phase response.

US Patent:

54914507, Feb 13, 1996

Filed:

Jun 1, 1993

Appl. No.:

8/069869

Inventors:

David R. Helms - Liverpool NY
Michael J. Fithian - Liverpool NY

Assignee:

Martin Marietta Corporation - Syracuse NY

International Classification:

H03F 134

US Classification:

330277

Abstract:

A low power consumption amplifier that is essentially insensitive to the process used to fabricate the active devices of the amplifier employs feedback to minimize variations in electrical characteristics of the devices. For weight-sensitive microwave applications, a high electron mobility transistor (HEMT) or a pseudomorphic high electron mobility transistor (PHEMT) may be selected as an active device for each stage of the amplifier. HEMTs and PHEMTs typically exhibit greater device gain than do MESFETs, especially at the upper portion of X-band and above, so that a HEMT- or PHEMT-based stage of an amplifier where additional overall gain is required, can be achieved without significantly adversely affecting power consumption demands, and attendant electrical energy storage/generation requirements while achieving and/or maintaining an overall flat gain characteristic of the amplifier.

US Patent:

50498410, Sep 17, 1991

Filed:

Jul 11, 1990

Appl. No.:

7/551067

Inventors:

Paul D. Cooper - Baldwinsville NY
Paul A. Bourdelais - Liverpool NY
Anthony W. Jacomb-Hood - North Syracuse NY
John A. Windyka - Liverpool NY
David R. Helms - Liverpool NY
Ronald J. Naster - Liverpool NY

Assignee:

General Electric Company - Syracuse NY

International Classification:

H03H 1124

US Classification:

333 81R

Abstract:

An electronically reconfigurable digital pad attenuator is disclosed using selectively controlled segmented field effect transistors in a passive, non-gain state as the principal impedance elements. The attenuator may be fabricated in the monolithic microwave integrated circuit (MMIC) format with a segmented gate field effect transistor being connected in each of the separate branches of a Pi pad, Tee pad, or Bridged Tee pad attenuator configuration. The individual FET segments are maintained in a high admittance "ON" state or a low admittance "OFF" state in accordance with the binary control potentials applied to the gate of each segment, the principal electrodes being maintained at a zero potential difference. The attenuation then becomes a function of the binary gate potentials applied to each segment and assumes one of a set of well-defined discrete values. The attenuator consumes minimum power, provides attenuation steps that are independent of GaAs MMIC fabrication process tolerances, i. e.