Waveguide Mixer Research Articles

Low-noise millimetre-wave mixer diodes: results and evaluation of a test programme

The results of extensive measurements on metal-gallium arsenide Schottky-barrier diodes in a waveguide mixer are presented, with emphasis on cooled, low-noise operation. Aspects of diode design and manufacture are reviewed, particularly with a view to the better understanding of noise generation in the diode. It appears that previous current-transport and noise-generation models require modification.

Schottky diode receivers for operation in the 100-1000 GHz region

Increased interest in the millimetre and submillimetre wavelength regions during the past decade has stimulated the development of sensitive heterodyne receivers for a wide range of applications. The GaAs Schottky-barrier diode has received the most attention as a mixer in this wavelength range as a result of its sensitivity, reliability, mechanical stability and wide bandwidth and its ability to operate at room temperature. The concepts of receiver design and the particular problems associated with this region of the frequency spectrum are discussed. The optimization of material parameters and the device topology for low-noise operation are considered. The extension of fundamental waveguide mixers into the submillimetre region and the development of various types of quasi-optical receivers are reviewed. The development of integrated monolithic receivers in which antenna, coupling structure, mixer diode and intermediatefrequency filter network are fabricated on the GaAs surface offers the possibility of increased reliability, repeatable and improved performance, and the potential economy associated with integrated circuit technology. In addition, the possibility of monolithic receiver arrays provides the systems designer with a capability that was not previously attainable using discrete diode receivers. This newly emerging technology is reviewed and the potential impact on the 100-1000 GHz region is discussed.

Cryogenic Millimeter-Wave Receiver Using Molecular Beam Epitaxy Diodes

A millimeter-wave cryogenic receiver has been built for the 60-90-GHz frequency band using GaAs mixer diodes prepared by molecuIar beam epitaxy (MBE). The diodes are mounted in a reduced-height image rejecting waveguide mixer which is followed by a cooled parametric amplifier at 4.5-5.0 GHz. At a temperature of 18 K the receiver has a total single-sideband (SSB) system temperature of 312 K at a frequency of 81 GHz. This is the lowest system temperature ever reported for a resistive mixer receiver. The low-noise operation of the mixer is seen to be a result of 1) the short-circuiting of the noise entering the image port and 2) an MBE mixer diode with a noise temperature which is consistent with the theoretical shot noise from the junction and the thermal noise from the series resistance.

Design and Performance Analysis of an Octave Bandwidth Waveguide Mixer

A new broad-band mixer capable of operating over two full adjacent waveguide bands (18 to 26.5 GHz and 26.5 to 40 GHz) is described. Within the octave bandwidth from 20 to 40 GHz, the maximum conversion loss is 6.5 dB with a corresponding average DSB noise figure of 5.7 dB. A theoretical analysis is given to treat quantitatively the performance of the octave bandwidth waveguide mixer.

Waveguide Mixer Sum frequency Termination Considerations in an FM Communication System

In a 6-GHz FM communications system using a mixer with its diode mounted in waveguide, group delay and linearity anomalies were observed which resulted in serious degradation of intermodulation signal-to-noise performance. This paper describes the problem, presents the reasoning and the laboratory tests by which improper termination of the mixergenerated sum frequency was isolated as its source, and describes a waveguide sum frequency absorber located at the mixer to solve the problem. The necessity of giving attention to all the signals generated in a nonlinear device in waveguide is discussed in this paper and has application to all such components in FM systems.