Microwave Gunn diode

We have previously defined the relative dB scale in Equation 2.11. The power in EPR is expressed in decibels (dB) attenuation (or alternatively in -dB amplification) of a maximum value. X-band microwave sources (either klystrons or Gunn diodes) have a constant output that is usually leveled off at 200 mW. This value then corresponds... 

A schematic of an ESR spectrometer is shown in Fig. 3 more detailed discussion of construction and operation of the instrument can be found in Ref. 1 and in the citations therein, as well as in the manuals accompanying the spectrometer to be used. The microwave source is a vacuum-tube Klystron or a solid-state Gunn diode, which provides... 

The lower-powered microwave signals used by communication transmitters are usually produced by solid-state devices. The Gunn diode is an example. When supplied with voltage from a well-regulated power supply these devices reliably produce a few watts of microwave signal. 

CW microwaves at 9.35 GHz are generated by a cavity-stabilized Gunn diode oscillator with an output power of 20 mW. The microwaves are then chopped at a frequency 20 Hz < < 10 kHz by a p-i-n switch... 

G. Thimp, F. Benmakroha, A. Leontakianakos and J.F. Alder, Analytical Microwave Spectrometer Employing a Gunn Diode Locked to the Rotational Absorption Line,... 

Microwaves sources include electron beams (e.g.. magnetron, klystron), semiconductors (e.g, Gunn diode, transistor) and masers (microwave amplification by stimulated emission of radiation) [88]. The depth of penetration d of microwaves into a dielectric is a function of the lo.ss factor S in the dielectric material and the frequency / of operation (or vacuum wavelength aq) [89] and is given by... 

Besides the ambiguity of fitting simulated to experimental spectra, the instrumental limits (most conventional microwave sources — klystrons, Gunn diodes, etc. — operate only a limited band width within the octave, that is, they are not tunable) of the one frequency per octave approach does not assme one of being able to obtain the requisite number of spectra to begin with. For example, it is highly problematic to record cw-ENDOR of weakly coupled " N at the X-band... 

Microwave spectroscopy uses tunable coherent sources of radiation such as microwave synthetizers, solid state oscillators (Gunn diodes) or electronic tubes (klystrons). These oscillators can be operated in their fundamental mode (up to 120 GHz) but harmonic generation is commonly realized with frequency multipliers up to 500 GHz, and has been used to reach 1 THz on occasions. Backward wave oscillators are available up to 1.2 THz in their fundamental mode. Figures 1 and 2 show typical rotational spectra recorded with this type of sources. Different techniques can be used to work in the THz region ... 

Gunn-effect oscillators (or Gunn diodes as they are frequently called, although technically, they are not diodes) in a resonant cavity can be used to make very simple low power microwave oscillators. Handheld radar speed detectors use Gunn-effect oscillators as their microwave source. 

Using the negative resistance characteristics of tunnel diodes and Gunn diodes, simple low-cost oscillators are possible that have found their way into handheld radar units and other microwave applications. 

The source of microwave radiation at Arizona State University is a set of three phase-locked Gunn oscillators (Fig. 3), which operate in the 65-140-GHz region at power levels of about 50 mW. Higher frequencies are obtained by doubling, tripling, or quadrupling the fundamental frequency in a nonlinear Schottky diode multiplier. The millimeter wave radiation is frequency modulated at 25 kHz by adjusting the reference frequency used in the lock circuit. 

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