Reflections in anechoic chambers in 100-200 GHz range

Three anechoic chambers have been tested at 110 and 183 GHz. Typical sidewall reflectivity levels are about -60 dB at 110 GHz and -50 dB at 183 GHz measured with pyramidal horns which have a gain of 20 dB. Backwall reflectivity levels are about -35 dB at 110 GHz and -25 dB at 183 GHz.<>     

Broad-Band Bias-Current-Tuned IMPATT Oscillator for 100-200 GHz

Broad-band bias-current-tuned IMPATT oscillators rising harmonic oscillations have been realized for the short-millimeter wave-length region (100-300 GHz). The relationship between diode and wave-guide parameters (breakdown voltage, junction diameter, and waveguide cutoff frequency) to obtain broad-band tunable oscillations is investigated theoretically and experimentally. Consequently, a tuning bandwidth of 35 GHz is obtained with IMPATT oscillators in the 160-GHz band, and 30 GHz in the 200-GHz band.     

High-power generation in IMPATT devices in the 100-200-GHz range

A silicon double-drift IMPATT diode with high uniform doping levels was simulated. Simulation results show that it is possible for silicon IMPATT diodes to generate extremely high pulsed output power for frequencies above 100 GHz under high current-density operation. The highest output power matched to a 1-Ω load resistance obtained at 150 GHz is 37.7 W with a DC current density of 200 kA/cm², although the calculated power conversion efficiency is low. It is also shown that the low-power conversion efficiency limits the diode's continuous wave power operation     

Volume integral equation solution of extinction cross section byraindrops in the range 0.6-100 GHz

The validity of the volume integral equation formulation (VIEF) is validated for the purpose of estimating the extinction cross section (ECS) of raindrops. The validations are performed against two well-established models. The validated volume integral equation model is employed to calculate the extinction cross sections of raindrops specified by a modified Pruppacher and Pitter (MPP) model. Data are given for drops with mean radii between 0.25 to 3.5 mm in the frequency range 0.6 to 100 GHz. Our study has showed that results of the extinction cross section for vertical and horizontal polarizations can be used to predict rain attenuation in wireless communications     

An empirical formula for the prediction of rain attenuation infrequency range 0.6 - 100 GHz

An empirical formula for calculating the extinction cross section (ECS) by raindrops over a broad frequency range is first derived based on extensive calculations made on a widely varying in mean radius of modified Pruppacher and Pitter (MPP) raindrop models ranging from 0.25 to 3.5 mm. The expansion coefficients in the empirical formula are determined by least-squares curve fitting of numerical data obtained by the volume integral equation formulation (VIEF). The formula satisfies the frequency and raindrop size dependence. Numerical results obtained from the empirical formula for calculating the ECS are generally in good agreement with those calculated by the VIEF for raindrops with mean radius varying from 0.25 to 3.5 mm in the frequency range from 0.6 to 100 GHz. The average error in the ECS is less than 10%. The formula thus provides a simple and inexpensive method for calculating the ECS of raindrops, which otherwise requires complicated and expensive methods of calculation. By implementing this empirical formula of ECS into the rain attenuation equation, a new numerically empirical formula for calculating the specific rain attenuation is also proposed. The validity of the empirical formula for calculating the specific rain attenuation is also checked by comparing the obtained results of specific rain attenuation with those obtained from Li et al.'s (1995) solution, Yeo et al.'s (1993) measurement, and Olsen et al.'s (1978) power-law equation     

Reflectivity of some materials at 94 GHz

In order to better understand the characteristics of discrete natural land clutter at millimeter wavelengths, an experimental investigation of the relative reflectivity of various materials at 94 GHz was performed using a substitution technique. The data show that nonconducting materials have a relative reflectivity on the order of 2–3%, and that absorbed water can increase the relative reflectivity significantly.     

A planar wideband 80-200 GHz subharmonic receiver

A wideband planar subharmonic mixer has been designed for millimeter-wave operation. The receiver consists of a back-to-back Schottky-diode pair integrated at the base of a wideband log-periodic antenna and placed on a silicon lens. The wideband planar receiver results in state-of-the art-performance at 90 GHz (and 182 GHz) with a double-sideband conversion loss and noise temperature of 6.7 dB (and 8.5 dB) and 1080 K (and 1820 K), respectively. These results are about 3 dB higher than the results for best tuned waveguide subharmonic mixers using planar diodes. The design is well suited for higher frequencies (up to 1 THz) and for the inclusion of biased back-to-back planar diodes to ease the LO power requirements. The planar subharmonic approach results in an inexpensive wideband receiver, and the design can be easily extended to receiver arrays     

Reflectivity measurements of various commercial absorbers atmillimetre and submillimetre wavelengths

Several absorbers made from new materials, and intended for frequencies up to 1THz, are commercially available. Reflectances of these absorbing panels, measured at 200, 300, 400, 500, and 600 GHz with different incident angles, are presented     

A 90-100 GHz double-folded slot antenna

A double-folded slot antenna (DFS) has been designed, fabricated, and tested at 90-100 GHz. The antenna shows a very wideband impedance around 20 Ω from 85 to 110 GHz. The low impedance is compatible with superconductor-insulator-superconductor (SIS) junctions, Schottky diodes or high electron mobility transistor (HEMT) amplifiers, which require a low impedance at millimeter wave frequencies. The antenna is placed on a dielectric lens to synthesize a semi-infinite substrate and realize high-directivity patterns. The measured radiation patterns agree very well with theoretical calculations and demonstrate symmetric main beams and sidelobe levels below -15 db over a 10% bandwidth. The double folded slot antenna is an attractive candidate for low-cost wideband millimeter-wave monolithic microwave integrated circuits (MMIC) front ends     

A Very Low-Noise Single-Sideband Receiver for 200-260 GHz

A cryogenic Schottky diode mixer receiver has been built for the 230-GHz region with true single-sideband operation and a receiver noise temperature as low as 330 K. Local oscillator power is provided by a frequency tripler, with LO injection and sideband filtering accomplished through quasi-optical interferometers. The image sideband is terminated in a cryogenic load with an effective temperature of 33 K. The IF bandwidth is 600 MHz with nearly flat noise, and the RF band is nearly flat over 50 GHz using backshort tuning of the mixer.     

A solid-state frequency source for radio astronomy in the 100 to 1000 GHz range

A compact Gunn oscillator-multiplier combination can provide the for SIS receivers necessary LO power up to 1000 GHz. Frequency multiplication factors of 2 to 8 are accomplished in a single step using a Schottky mixer diode in the varistor mode.     

Low-loss sapphire waveguides for 75-110 GHz frequency range

Low-loss dielectric waveguides are promising for use instead of metal ones, but problems in transitions have to be overcome. A simple and effective structure made of a monocrystalline sapphire waveguide has been designed. Experimental results at 75-110 GHz indicate good matching with metal waveguides (VSWR ⩽1.13) and low insertion loss (0.05-0.35 dB for 47 mm dielectric section)     

Monostatic Reflectivity Measurement of Radar Absorbing Materials at 310 GHz

This paper presents monostatic reflectivity measurements of radar absorbing materials at 310 GHz in a phase-hologram-based compact range. The radar cross-section method was used and the backscattered reflection was measured with horizontal and vertical polarizations in plane-wave conditions. Transmission was also studied. The reflectivity was measured over an incidence angle of 0$^circ$–45$^circ$. The reflectivity of Thomas Keating Terahertz RAM at normal incidence was found to be$-$56 dB—the smallest of the studied materials. The reflectivity of carpet material measured was also below$-$40 dB and it was found to be suitable for use as an absorber. The results are in line with those available from previous studies of reflectivity and complement them with new materials, frequency, and angle information.     

Spherical near-field facility for microwave coupling assessments inthe 100 MHz-6 GHz frequency range

This paper describes a spherical near-field facility set up at the Centre d'Etudes de Gramat (CEG) to perform low-power microwave coupling assessments. Specifically, this facility has been designed to determine the coupling cross section of a complex object. However, it can also be used for the characterization of any radiating system in electromagnetic compatibility (EMC) or high-power microwave (HPM) environments. The near-field approach is shown to be complementary and to offer increased flexibility when compared to other more conventional measurement techniques. More particularly, the use of a probe array in the upper part of the frequency band significantly speeds up the near-field measurement process. Consequently, broadband and multiparameter acquisitions can be performed within acceptable duration. The examples given in this paper provide a broad illustration of the capabilities of near-field techniques for EMC and HPM applications     

Microwave (1-100 GHz) dielectric model of leaves

A semiempirical formula for the complex dielectric permittivity of leaves from different plants is found from a comparison of published measurements covering the frequency range from 1 to 100 GHz. The explicit parameters are the dry-matter fraction m_d of the leaf and the permittivity ϵ_SW of saline water with a salinity of about 1 percent. The physical part of the formula is its basis on ϵ_SW while the empirical part is its linearity with m_d. The formula is applicable to fresh leaves; their m _d values are in the range 0.1d<0.5. A test indicates that besides the m_d variation and the spectral dependence the formula also describes the temperature variation correctly     

Atmospheric emission and attenuation in the range 100 to 600 GHz measures from a mountain site

Further measurements of atmospheric emission from a site in the Canary Islands (Izana, âltitude 2.4 km) have been made during the month of August 1980. The measurements were made with a polarising Interferometer and a composite Ge bolometer. An independent measurement of the precipitable water vapour was made using Infrared Hygrometers. The experimental details are described and the spectra obtained are compared with model spectra using the measured precipitable water vapour.     

Model for estimating rain attenuation at frequencies in range 6-30GHz

The raindrop size distribution (RSD) for various types of rainfall over Guwahti, India is presented. The observed RSD parameters are compared with those given by other models. By employing the observed RSD, the values of a and b in the relation A=aR^b for estimating the rain attenuation at frequencies from 6 to 30 GHz are given. The significance of the type of rainfall in controlling attenuation is discussed     

Monostatic Reflectivity and Transmittance of Radar Absorbing Materials at 650 GHz

Transmittance and monostatic reflectivity of different radar absorbing materials at 650 GHz are presented. The reflectivity was measured in plane-wave conditions in a radar cross-section (RCS) range with vertical polarization. The lowest reflectivity level (-70 dB) was achieved with commercial absorbers TK THz RAM and Firam-500 with oblique incidence angles. Floor carpets were also studied, and the reflectivity level of those was found to be sufficiently low (from -50 to -60 dB) for use in antenna test ranges. Results agree with earlier studies and indicate the applicability of the RCS method in reflectivity measurements also at 650 GHz.     

Transistor and circuit design for 100-200-GHz ICs

Compared to SiGe, InP HBTs offer superior electron transport properties but inferior scaling and parasitic reduction. Figures of merit for mixed-signal ICs are developed and HBT scaling laws introduced. Device and circuit results are summarized, including a simultaneous 450 GHz f/sub /spl tau// and 490 GHz f/sub max/ DHBT, 172-GHz amplifiers with 8.3-dBm output power and 4.5-dB associated power gain, and 150-GHz static frequency dividers (a digital circuit figure-of-merit for a device technology). To compete with advanced 100-nm SiGe processes, InP HBTs must be similarly scaled and high process yields are imperative. Described are several process modules in development: these include an emitter-base dielectric sidewall spacer for increased yield, a collector pedestal implant for reduced extrinsic C/sub cb/, and emitter junction regrowth for reduced base and emitter resistances.     

Universal MOSFET gate impedance model for 200 MHz–20 GHz frequency range

The scaling of CMOS technology to 100 nm and below and the endless pursuit of higher operating frequencies drives the need to accurately model effects such as gate leakage and the deterioration of transport characteristics that dominate at those feature sizes and frequencies. Current modeling techniques are frequency limited and require different models for different frequency ranges in order to achieve accuracy goals. In the foundry world, high frequency models are typically empirical in nature and significantly lag their low frequency counterparts in terms of availability. This tends to slow the adoption of new foundry technologies for high performance applications such as extremely high data rate serializer/deserializer (SERDES) transceiver cores. However, design cycle time and time to market while transitioning between technology nodes can be reduced by incorporating a re-usable, industry-standard model. This work proposes such a model for device gate impedance that is simulator-friendly, compact, frequency-independent, and relatively portable across technology nodes. This semi-empirical gate impedance model is based on depletion in the poly-silicon gate electrode. The model performs accurately over 200 MHz–20 GHz at different bias conditions and widths and has been verified by measured data in three technology nodes. The model and model parameter behavior are consistent across technology nodes thereby enabling re-usability and portability.