Pulsed 5-GW resonance relativistic BWT for a decimeter wavelength range

The results of numerical modeling and experimental investigation of a high-power, resonance relativistic backward wave tube are presented. By using the working TM₀₁ mode reflections from the ends of the electrodynamic system, optimum conditions for the electron beam interaction with both the (−1)st harmonic of the backward electromagnetic wave and the main harmonic of the concurrent wave are achieved. A single mode generation with 5 GW output power and a 30% efficiency was obtained in experiments at a frequency of 3.6 GHz. The working frequency can be controlled within 15% (at the half maximum power level) by changing the slow-wave structure period at the constant electron beam parameters.     

A method to measure the aperture field and experimentally determinethe near-field phase center of a horn antenna

A method whereby the aperture field distribution of a horn antenna can be measured is proposed. The method is based on the measurement of the scattered field of a small conducting sphere in the aperture. The position of the phase center of the aperture field is calculated using the measured phase distribution of the field in the aperture via a simple type of convolution. In principle, the method is suited to determine the field distribution of other types of apertures illuminated by an electromagnetic field     

Characteristics of an acoustooptical spectrometer for remote atmospheric sounding in the millimeter wavelength range

We consider the main characteristics and application features of an acoustooptical spectrometer with a 500 MHz bandwidth employed in a ground setup for remote measurements of the atmospheric ozone emission band with a central frequency of 142.175 GHz. The results of determination of the instrument parameters and the examples of atmospheric ozone spectra are presented.     

A quasi-optical phase shifter based on an active grating for the 8-mm wavelength range

A new quasi-optical phase shifter for the 8-mm wavelength range, which allows the phase of electromagnetic radiation in a wave beam to be controlled, is described. The phase shifter operation is based on the phenomenon of wave phase variation upon reflection from an active grating that is formed by the layers of plasma in channels of a dielectric plate arranged above a flat metal mirror. It is shown that the phase of the reflected wave can be effectively controlled by changing the grating-mirror distance and the gas pressure in the channels. The experimental data are compared to the results of numerical calculations.     

Electric field meter with dipole antenna in an alternating nonuniform electric field

Translated from Izmeritel'naya Tekhnika, No. 11, pp. 55–59, November, 1992.     

Axial irradiance distribution throughout the whole space behind an annular aperture

In many photonics and fiber-optics applications, the irradiance distribution in the very near field (z/D < 0.25) behind a circular or annular aperture is of interest. We present the results of detailed calculations of the irradiance distribution throughout the entire space behind an annular aperture. Included as a special case of the annular aperture is the circular aperture and the opaque circular disk. A log-log plot over many orders of magnitude in axial distance provides particular insight. The behavior throughout the Fresnel and Fraunhofer region is well known; however, we pay particular attention to the behavior in the near field. A variety of subtle effects in the near field are presented and discussed.     

Working attenuation standards in the decimeter and centimeter wave range based on fixed coaxial attenuators

The main measurement error components of fixed coaxial attenuators were investigated. Numerical values of the mismatch, random, and flange errors were obtained. The resultant error can be reduced to 0.01 dB/10 dB at frequencies below 12 GHz. Translated from Izmeritel'naya Tekhnika, No. 10, pp. 42–44, October, 1999.     

Simple method for antireflection coating ZnSe in the 20 microm wavelength range

We present a simple, inexpensive, and effective method of applying antireflection coatings to zinc selenide windows designed to operate in the thermal infrared wavelength region.     

Electric field meter with a dipole antenna in an elliptically polarized electric field

A model of an electric field meter with a dipole antenna is analyzed. The model takes into account the fact that the meter incorporates other elements with a conducting surface in addition to the dipole antenna, viz.: a matching device, a signal cable, and a voltmeter. Alternative forms of the measurement equation are obtained, which differ in the error associated with the currents induced by the measured electric field on the braid of the signal cable and on the casing of the voltmeter. It is shown that this error can be eliminated partially or completely by performing additional measurements with the dipole antenna in different positions.Translated from Izmeritel'naya Tekhnika, No. 2, pp. 45–48, February, 1994.     

A diffraction trap for neutrons in the Ångström wavelength range

The penetration depth of thermal neutrons (λ∼1 Å) upon the Bragg backscattering in a bent crystal is estimated. It is demonstrated that neutrons incident onto the crystal at an angle close to the edge of the Bragg reflection curve can be accumulated inside and then (after 1–100 μs) ejected from the crystal.     

Foamy-dielectric lens transmission lines for millimeter and submillimeter wavelength range

The principles of the construction of transmission lines based on lenses made of a material with a nearly unity refractive index (foamy-dielectric lens transmission line, FDLTL) are formulated. The transmission characteristics of two FDLTL variants for 3-mm wavelength band have been studied. It is shown that FDLTLs possess low damping and feature wave propagation in a single-mode regime.     

Axial irradiance distribution throughout the whole space behind an annular aperture: comments

We comment on the recent paper by Harvey and Krywonos [Appl. Opt. 41, 3790-3795 (2002)], in which approximate irradiance calculations along the axis of a circular aperture illuminated by a plane wave are performed. As the starting point of their calculations, an approximated version (valid for z > lambda) of the Rayleigh-Sommerfeld diffraction integral is used. They based their numerical conclusions on a misleading "near field criterion," which guides the readers to the wrong idea that their calculations are valid even for the very near field behind the aperture. Their ideas are not original; the exact calculations of diffracted fields behind a circular aperture have been known for 40 years.     

Modeling of a crossed-groove cavity in the 8 mm wavelength range

Results are presented of experiments on the scale modeling of a crossed-groove quasioptic cavity. It is demonstrated that high-Q modes can be excited with a ring structure at the mirror and a field maximum at the center of the cavity. Pis’ma Zh. Tekh. Fiz. 24, 69–75 (October 12, 1998)