Gunn diodes

Optoelectronic components produced by CVD include semiconductor lasers, light-emitting diodes (LED), photodetectors, photovoltaic cells, imaging tubes, laser diodes, optical waveguides, Impact diodes, Gunn diodes, mixer diodes, varactors, photocathodes, and HEMT (high electron mobility transistor). Major applications are listed in Table 15.1.El... 

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... 

E. Alekseev and D. Pavlidis. GaN-Based Gunn Diodes Their Frequency and Power Performance and Experimental Considerations www.eecs.umich.edu. 

This chapter focuses on the properties of deep states in wide band-gap III-V semiconductors. Deep states are important in semiconductors in general and very often determine the recombination properties. Wide band-gap III-V compounds are now commonly used for many important optoelectronic devices (for example, lasers, light-emitting diodes, and Gunn diodes), and are being suggested for additional interesting applications (for example, solar cells). In view of the importance of such work there are a number of earlier... 

Rapid raster-scanned CW imaging systems have also been developed. In one such implementation, a 0.2 THz Gunn diode source and Schottky diode detector [93] could raster-scan an object at a 512 pixels per second acquisition rate. The advantages of pulsed THz TDS compared to CW imaging is that broad spectral information (0.1-3 THz) can... 

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... 

Landauer studied the behavior of a bistable system consisting of a tunnel diode and focused his attention on the activation jump between the two states resulting from thermal fluctuations. Later, Matsuno ° analyzed the power spectrum of the noise affecting the electric conductivity of a Gunn diode. Diode oscillations were proven to be accompanied by modulation of both amplitude and frequency. The noise spectrum was shown to exhibit typical 1// characteristics, and fluctuations were found to appear in the region close to the critical threshold with an increasing relaxation time as the threshold was approached. This behavior is largely reminiscent of that ex-... 

In 1973, Kawakubo et al. did a more detailed investigation on the behavior of a Gunn diode. They proved that the distribution of the fluctuations near threshold is broadened and deviates from the Gaussian type. The non-Gaussian distribution near threshold comes from an emergence of nonlinearity which is due to the enhancement of fluctuations associated with the instability of the system. 

A Gunn diode agaio was used to study the low-frequency spectrum. In this frequency domain a critical region was detected where the system alternates between oscillatory and nonoscillatory behavior with a random time period. 

We shall develop the theory necessary to understand quasioptics, but before that, it will be useful to consider factors that influence the choice of spectrometer components such as the magnet, the source, and the detector. In Section II we will give a brief review of the performance and characteristics of homodyne detectors. In our discussion of sources, we will discuss vacuum oscillators, such as the reflex klystron and backward wave oscillator, and solid-state sources, such as the Gunn diode. We will also discuss useful criteria for selecting a magnet. 

The Cornell spectrometer is based on a phase-locked, CW, Gunn diode that has an output power of 3 mW at 250 GHz. The phase-lock circuitry is shown schematically in Lynch et al. (1988) and we will not comment on it further, except to note that the phase noise is — 90 dBc at an offset of 100 kHz. The source is rugged, reliable, and very easy to use in practice. 

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. 

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