A wide-band monolithic quasi-optical power meter for millimeter and submillimeter-wave applications

A novel monolithic power meter has been developed for submillimeter-wave applications (100 GHz to 10 THz). The detector is a large-area bismuth bolometer integrated on a 1.2-μm-thick dielectric membrane. This approach results in a wide-band, high-responsivity detector. The power meter is simple to fabricate, is inexpensive, and can be easily calibrated using a low-frequency network. Quasi-optical measurements at 90, 140, and 240 GHz show that the bolometer is polarization-independent and could be modeled by a simple transmission line model. Absolute power measurements at 90, 140, and 240 GHz show a ±5% accuracy and agree well with a calibration Anritsu power meter at 90 GHz. Potential application areas are power calibration, antenna coupling efficiency measurements, and absolute power measurements from solid-state devices and far-infrared lasers at submillimeter wavelengths. Absolute output power measurements on a 220-280 GHz tripler using the quasi-optical power meter are presented as an application example     

19 GHz space-Earth depolarization measurements at 4° polarization

Depolarization was measured at a polarization angle of4degfrom vertical. Depolarization transformed to this4degpolarization from measurements made at polarizations21degfrom vertical and horizontal is compared with the direct measurements scaled to the path elevation angle of the transformed measurements. Over the ranges of attenuation and depolarization for which the measurements are meaningful, the agreement between them is good. These results further reinforce our confidence in the results and conclusions obtained earlier using the polarization transformation technique.     

On the estimation of snow depth from microwave radiometricmeasurements

Multiple-channel microwave radiometric measurements made over Alaska at aircraft (near 90 and 183 GHz) and satellite (at 37 and 85 GHz) altitudes are used to study the effect of atmospheric absorption on the estimation of snow depth. The estimation is based on the radiative transfer calculations using an early theoretical model of Mie scattering of single-size particles. It is shown that the radiometric correction for the effect of atmospheric absorption is important even at 37 GHz for a reliable estimation of snow depth. Under a dry atmosphere and based on single-frequency radiometric measurements, the underestimation of snow depth could amount to 50% at 85 GHz and 20-30% at 37 GHz if the effect of atmospheric absorption is not taken into account. The snow depths estimated from the 90-GHz aircraft and 85-GHz satellite measurements are found to be in reasonable agreement. However, there is a discrepancy in the snow depth estimated from the 37-GHz (at both vertical and horizontal polarizations) and 85-GHz satellite measurements     

PARAN antenna for use where horizontal and vertical space islimited

A PARAN (perimeter current antenna) antenna which was constructed, tested, and licensed at radio station KAPS in Mount Vernon, Washington, USA, is described. A PARAN antenna is intended for the broadcaster whose site is severely limited in height and ground area. Both current distribution versus height measurements and full field proof-of-performance measurements were made to prove the antenna's efficiency. The results show that a PARAN antenna can produce a radiation field better than 282 mV/m/1 kw at 1 km (175 mV/m/1 kw at 1 mi). Bandwidth evaluation measurements and radiation hazard measurements are discussed     

Voltage measurement at high and microwave frequencies in coaxial systems

The progress and up-to-date state-of-the-art in measuring voltages at frequencies to 10 GHz and higher is briefly described. The trend towards higher frequencies in voltmeter design is indicated. Advantages of voltage measurements and standards over computation of voltages from power and impedance measurements are briefly discussed. Some pending development problems are indicated and major steps are proposed to improve the application of voltmeters at frequencies above 30 MHz.     

Dual frequency scintillation measurement for remote sensing

A scheme is proposed for utilising measurements of radiowave amplitude scintillation at two frequencies for remote sensing of wind speed and atmospheric turbulence parameters. The main advantage of the method is that all quantities are estimated solely from measured scintillation parameters without the need for secondary measurements. It is shown that the method yields results which compare well with other measurements     

Study on AlSb Polycrystalline Films Prepared by Magnetron Sputtering

AlSb polycrystalline thin films were prepared by magnetron sputtering with an improved geometric target, and their structural,electrical and optical properties were studied. The results of XRD measurements suggest that the annealed AlSb thin films are Zinc-blende structure with the average size of about 23～31 nm, and the higher temperature promotes the crystallization of the films. The morphology obtained from the AFM measurements reveals that the surfaces of the films are smooth and the particles are unifo...     

Adaptive Empirical Path Loss Prediction Models for Indoor WLAN

This paper presents robust empirical path loss models to characterize indoor propagation for access point (AP) deployed at different heights. The proposed models are developed with wireless local area network infrastructure at 2.4 GHz. The models are backed by extensive received signal strength (RSS) measurements acquired in line of sight and obstructed line of sight regions. The models are developed for two conditions, viz; quasi realistic and realistic RSS measurements. The quasi realistic measurements are taken after suppressing human intervention and electrical interferences to minimum. While the realistic RSS measurements are made in presence of all the human interventions and electrical interferences. The shadow fading component for both quasi realistic and realistic conditions is statistically modeled with the dependency on AP height. The proposed technique can be applied with higher confidence level to the buildings with similar construction features where RSS measurements are made upon. The results reveal that the performance of the proposed propagation models is significantly higher than the existing International Telecommunication Union-path loss model. The results also demonstrate that the realistic path loss model is more robust than the quasi realistic model.     

A 225 GHz polarimetric radar

An incoherent 225-GHz polarimetric radar capable of measuring the Mueller matrix of point and distributed targets is described. The transmitter employs an extended interaction oscillator that transmit 60-W pulses of 50- to 600-ns duration. Incoherent measurements of the Mueller matrix are achieved by transmitting four linearly independent polarizations and measuring the scattered wave using a dual-polarized receiver. A novel calibration technique that requires a single in-scene reflector is presented. Polarimetric measurements are presented of a dihedral corner reflector and foliage which are the first polarimetric measurements reported at this wavelength. The foliage measurements indicate a pronounced sensitivity of the polarimetric data to fine-scale surface structure     

The reconstruction of the relative phases and polarization of theelectromagnetic field based on amplitude measurements

The problem of determining the relative phases among the components of a monochromatic electromagnetic field at a single point based on amplitude measurements only is addressed. The following questions are answered: (1) How is the phase information reconstructed from amplitude measurements? (2) Do amplitude measurements contain enough information to reconstruct the phases uniquely? (3) How many amplitude measurements are required? and (4) In what directions must the amplitude measurements be taken to ensure that the reconstructed phases are unique? To answer these questions, a more general problem in n dimensions, the special case where n=3 being the solution to the above problem, is proposed and solved     

On the scattering mechanism of power lines at millimeter-waves

The radar signature of power lines is of high importance in the design of systems for helicopter collision avoidance. Laboratory measurements have been reported previously, but field measurements at millimeter waves are missing. The present contribution describes measurements done in ground-based configuration with a real aperture scanning-beam radar operating simultaneously at 35 and 94 GHz. By scanning, an aspect angle interval of 60/spl deg/ was covered, including the broadside aspect. The narrow beam width allowed to discriminate between different wires separated horizontally. While these measurements were done under a very shallow incidence angle, assisting measurements were done with the same radar mounted into an aircraft using synthetic aperture radar techniques. The results for shallow and steep incidence are compared and show the significant influence of this parameter on the signature of the power line. Additionally the measurement results are compared with those from model calculations.     

Steady state and transient electromagnetic coupling through slabs

The problem of electromagnetic transmission through a slab where transmitting and receiving antennas are at finite distances from the slab is considered. The mathematical formulation of the problem is quite general. A detailed solution is presented for the case of a highly conducting slab exposed to sinusoidal and transient excitations. A discussion is given of the conditions under which measurements with the source and receiver at finite distances are equivalent to the same measurements with plane wave excitation.     

Measurements of the characteristic impedance of coaxial air linestandards

A method for electrically measuring the characteristic impedance of coaxial air line standards is described. This method, called the gamma method, determines the characteristic impedance of a coaxial air line from measurements of its propagation constant and capacitance per unit length. The propagation constant is measured on a network analyzer, and the capacitance per unit length is measured on a capacitance bridge at 1 kHz. The measurements of characteristic impedance with the gamma method are independent of any dimensional measurements. Measurements of the characteristic impedance using the gamma method are compared to theoretical predictions from dimensional measurements. Test results are shown for 14 mm, 7 mm, and 3.5 mm coaxial air lines     

A 90-GHz double-drift IMPATT diode made with Si MBE

For the first time silicon double-drift IMPATT structures have been grown completely by Si molecular-beam epitaxy. The n-type layers are grown at 750 °C on low-resistivity n⁺-type substrates followed by p-type layers at 650 °C. The highly doped p⁺-layers are grown by solid-phase epitaxy in the MBE system. Device design is made for CW operation in W-band. The material is investigated by inspection of beveled samples, defect etching, TEM, SIMS, and spreading resistance measurements. Double-drift flat-profile diodes are housed and mounted employing a technological procedure approved for single-drift diodes. For initial device characterization, dc measurements are performed. Information about doping profile, series, and thermal resistances is obtained. Preliminary RF measurements delivered a maximum output power of 600 mW at 94 GHz with 6.7-percent efficiency from an unoptimized structure.     

Construction and measurement of the pre-series twin aperture resistive quadrupole magnet for the LHC beam cleaning insertions

CERN's Large Hadron Collider (LHC) requires 48 twin aperture resistive quadrupoles in the beam cleaning insertions. Canada is contributing these magnets to CERN in the framework of the TRIUMF-LHC collaboration contracts. A pre-series magnet was produced by Canadian industry and delivered in March 2001. This magnet incorporates important design changes that resulted from experience with a prototype magnet. The construction of this pre-series magnet and the measurements made at ALSTOM and at CERN are reported. A comparison is made between high precision pole distance measurements and the magnetic measurements performed with a rotating coil mole. Conclusions for series production and possibilities for multipole corrections are outlined.     

Microwave attenuation measurements in satellite-ground links: thepotential of spectral analysis for water vapor profiles retrieval

The authors address the problem of estimating vertical profiles of atmospheric water vapor by means of attenuation measurements simultaneously made at different frequencies along a vertical satellite-ground link. The operating frequencies selected are those around the spectral absorption lines of water vapor at 22.235 GHz. A simulation is presented of multifrequency attenuation measurements, based on an atmospheric propagation model and on radiosonde data providing true profiles of temperature, pressure, and water vapor. The results indicate that such multifrequency measurements are correlated to variations of the vertical profiles of water vapor. It is therefore expected that vertical detail of such profiles depends on number and position of the frequencies utilized     

Incoherent Scatter Radar Probing of the 60-100-km Atmosphere and Ionosphere

All current incoherent backscatter radars can make mesospheric or D region measurements (60-90-km altitude) under at least some conditions. This paper, which is tutorial in nature, develops the basic concepts of incoherent scatter radar measurements in the D region and the conditions under which measurements are possible are derived and shown for each radar. Conditions examined include overall system sensitivity, electron and ion spectral line widths and power distributions, and time/height averaging effects. The appropriate form of the radar equation is derived and calibration of the radar system is discussed along with the various aspects of signal processing involved. Total power only and combined total power and ion line spectral measurements are described in terms of ease of use, applicability to various radars, and parameters of aeronomic interest derivable from the measurements.     

Directional ocean wave measurements in a coastal setting using afocused array imaging radar

A unique focused array imaging Doppler radar was used to measure directional spectra of ocean surface waves in a nearshore experiment performed on the North Carolina Outer Banks. Radar images of the ocean surface's Doppler velocity were used to generate two dimensional spectra of the radial component of the ocean surface velocity field. These are compared to simultaneous in-situ measurements made by a nearby array of submerged pressure sensors. Analysis of the resulting two-dimensional spectra include comparisons of dominant wave lengths, wave directions, and wave energy accounting for relative differences in water depth at the measurement locations. Limited estimates of the two-dimensional surface displacement spectrum are derived from the radar data. The radar measurements are analagous to those of interferometric synthetic aperture radars (INSAR), and the equivalent INSAR parameters are shown. The agreement between the remote and in-situ measurements suggests that an imaging Doppler radar is effective for these wave measurements at near grazing incidence angles     

EVALUATION OF STATISTICAL MODELS FOR CLEAR-AIR SCINTILLATION PREDICTION USING OLYMPUS SATELLITE MEASUREMENTS

The objective of this study is to evaluate and to compare some of the statistical models for the monthly prediction of clear-air scintillation variance and amplitude from ground meteorological measurements. Two new statistical methods, namely the direct and the modelled physical-statistical prediction models, are also introduced and discussed. They are both based on simulated data of received scintillation power derived from a large historical radiosounding set, acquired in a mid-latitudue site. The long-term predictions derived from each model are compared with measurements from the Olympus satellite beacons at the Louvain-la-Neuve site at 12·5 and 29·7 GHz and at the Milan site at 19·77 GHz during 1992. The model intercomparison is carried out by checking the assumed best-fitting probability density function for the variance and log-amplitude fluctuations and analysing the proposed relationships between scintillation parameters and ground meteorological measurements. Results are discussed in order to understand the potentials and the limits of each prediction model within this case study. The agreement with Olympus measurements is found to be mainly dependent on the proper parametrization of prediction models to the radiometeorological variables along the earth–satellite path. ©1997 by John Wiley & Sons, Ltd.     

A procedure for calculating the atmospheric mutual coherencefunction via the statistical Fourier-optical method

An algorithm is presented for computing the atmospheric mutual coherence function at optical and millimeter wavelengths from flux measurements taken at the focal plane of a reflector antenna. The procedure consists of first computing the inverse Abel transform of the flux, taking the Fourier transform of the result, and then dividing by the aperture pupil function. It is shown that when the flux measurements contain additive noise, the Abel inversion is an ill-posed problem. Therefore, calculation of the inverse Abel transform is accomplished by a Kalman filtering algorithm. Results of the mutual coherence function estimator are given for simulated flux measurements