TERAHERTZ MIXERS BASED ON THE MACH-ZEHNDER INTERFEROMETER

Abstract

The general principles of operation and the advantages of using a Mach-Zehnder interferometer as a mixer of superheterodyne receiver in the terahertz range are considered. The sensitivity of existing terahertz receivers is significantly lower than the infrared and radio ranges. The solution of a large number of important tasks, such as radio astronomic observations, high-temperature plasma diagnostics, the study of the Earth's atmosphere, radar, etc, is largely connected with the research of the radiation of the terahertz range. In the next, the centimeter range, the best by far is the receiver of the direct amplification transistor, and in the infrared range, quantum photodetectors and bolometers based on doped semiconductors have record characteristics. In the short-wave part of the millimeter range, the losses in the path of SHF significantcly contribute to the noise performance of the receiver, and therefore, the development of devices for the addition of the power of the signal and local oscillator. This fact is paid considerable attention. However, at frequencies above 1 THz their noise temperature rises sharply. Mixers based on Schottky barrier diodes operate in terahertz bands, but their sensitivity is often insufficient for practical applications, and the required great power oscillator in the short end of this range is difficult to implement even in the laboratory. Thus, the problem of practical implementation of sensitive and wideband receivers in the terahertz range is inextricably linked to the search for new alternative frequency conversion mechanisms. One of perspective directions in this area is the use of interferometric systems. In this paper, the operation of the Mach – Zehnder interferometer perfomed on the basis of a rectangular metal dielectric waveguide is studied. It is shown that unlike conventional balanced circuits, the efficiency of which depends upon the identity of the two mixer diodes, in this case, the high degree of local oscillators noise suppression is achieved at using only one mixer diode, whereby the noise factor of a radio receiver has a relatively low value. Such an approach, particularly in the terahertz range, is more promising and independent.