Marvin Cohn

Harmonic Mixing with an Anti-Parallel Diode Pair

An analytical and experimental investigation of the properties of an antiparallel diode pair is presented. Such a configuration has the following unique and advantageous characteristics as a harmonic mixer: 1) reduced conversion loss by suppressing fundamental mixing products; 2) lower noise figure through suppression of local oscillator noise sidebands; 3) suppression of direct video detection; 4) inherent self protection against large peak inverse voltage burnout. These results are obtained without the use of either filters or balanced circuits employing hybrid junctions.

A 10 Watt Broadband FET Combiner/Amplifier

The development of a 10W MIC combiner/amplifier which combines the powers of 12 FET elemental amplifiers over a 24%, 1 dB band is described. The combining efficiency is greater than 90 percent. The design of both the radial combiner and the elemental amplifiers is described. Extension of the combiner design to operation over an octave will be discussed.

94 GHz subharmonically pumped MMIC mixer

A 94-GHz subharmonically pumped antiparallel diode pair MMIC (monolithic microwave integrated circuit) mixer with a short-circuit sum frequency termination is described. Advantages of the mixer configuration include (1) reduced conversion loss, (2) elimination of the need for an area-consuming hybrid junction while retaining the separation of local oscillator (LO), RF, and intermediate frequency ports, (3) inherent LO noise sideband suppression, and (4) very small size and cost.<<ETX>>

Class B Operation of Microwave FETs for Array Module Applications

In addition to the well known class B advantages of high eta /sub PA/ and self turn on for pulsed operation, it is shown herein that class B FET amplifiers have several other important features including: 1) Significantly reduced power dissipation 2) A dynamic range of typically 8-10 dB over which gain is constant and power added efficiency is >30%. 3) Phase behavior (static and dynamic) is comparable to that observed with similar FETs operated class A. 4) Absence of erratic phase behavior during pulse turn-on and turn-off. These features make class B operation of power FETs very attractive for phased array module applications.

A GaAs monolithic array of impedance matched antenna/detector pixels for a 94 GHz imaging system

The design, fabrication, and performance of a 4*4 pixel array of monolithic GaAs 94-GHz detector circuits is described. This large chip is developed to be a tile for much larger arrays consisting of thousands of pixels for 94-GHz imaging. Each pixel is a slot antenna on one face coupled through the GaAs to a microstrip circuit containing a Schottky-barrier diode on the opposite face. The microstrip circuit provides an optimum impedance match between the diode and the slot antenna so that no additional tuning to free space is required. The diode is fabricated using a selective ion implantation process optimized for uniformity, repeatability, and yield, and has zero-bias capacitance and series resistance, respectively, of 14 fF and 15 Omega . Process control is essential, because variations in diode parameters can mismatch and detune the circuit. With the diode optimally forward-biased for square-law operation and a video bandwidth of 1 MHz, the tangential signal sensitivity (TSS) peaked in the 92-96-GHz range and was always better than -50 dBm at 94 GHz.<<ETX>>

High Efficiency One, Two, and Four Watt Class B FET Power Amplifiers

A family of X-band amplifier utilizing the higher efficiency of class B operation has been designed and fabricated. This paper describes the circuitry and performance of 1 watt single-ended, 2 watt push-pull, and 4 watt dual push-pull amplifiers having typical power-added efficiencies of 45%, 40%, and 35%, respectively, in a 1 GHz bandwidth, with associated gains of 5.8 dB, 5.4 dB, and 5.0 dB . Additional data is given for fifteen each of the 1 watt and 2 watt units to show the consistency of their performance.

A Study of Optimal Matching Circuit Topologies for Broadband Monolithic Power Amplifiers

A large signal amplifier design technique for broadband monolithic amplifiers has been expanded to include studies of the optimal output circuit topology from the standpoint of large and small signal gain variations and stability.

A millimeter wave retrodirective transponder for collision/obstacle avoidance and navigation/location

A small, low power drain and low cost transponder are described, which have numerous automotive applications. The principle of operation of the retrodirective transponder (RDT) is based on the Van Atta array which has the ability to take an incident RF wave and re-radiate it back in the direction from which it cam, i.e., retrodirectively. While passing through the RDTs integral monolithic GaAs modulators, the RF wave can be modulated by information that is thereby automatically transmitted back to the interrogator. The operation of the modulatable Van Atta array is illustrated.

Octave Bandwidth High Speed Limiter with Uniform Suppression Characteristics

The performance of several octave-bandwidth diode clipper/limiters having uniform suppression characteristics over the 2.0 to 4.0 GHz octave is discussed. Suppression over the band is 4.0 dB or greater for a structure using Silicon diodes and 3.5 dB or greater for a similar structure using GaAs diodes.

Annular Resonant Slots in Dielectric-Filled Circular Waveguide

Measurements were made to determine the properties of thin annular resonant slots in polystyrene-filled circular waveguide, in which the TE/sub 11/ mode is propagating. Data on the variation of susceptance of these slots as a function of frequency through the X-band region is presented in graphic form. Quantitative information relating the resonant frequency and Q of these slots to their geometry is presented. An empirical expression was found relating the Q of these slots to their gap size.