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Future space research communications systems may require spectra above 20 GHz. Frequency bands above 20 GHz are identified that are suitable for space research. The selection of the proper bands depends on consideration of interference with other radio services, adequate bandwidths, link performance, and technical requirements for practical implementation.
In this work, we describe new miniaturized low noise amplifier modules which we developed for incorporation in small-scale satellites or Cubesats, and which exhibit similar or better performance compared to previously reported LNAs in the literature. We have targeted the WR4 (170-260 GHz) and WR3 (220-325 GHz) waveguide bands for the module development. The modules include two different methods of E-plane probes which have been developed for low loss, and stability at high frequencies. MMIC LNAs were also developed for these frequency ranges and fabricated in Northrop Grumman Corporation's 35 nm InP HEMT technology, and we have experimentally verified that noise performance is lower than reported in prior work. The best results include a miniature LNA module with 550K noise at 224 GHz, and a wideband LNA module with 15 dB gain from 230-280 GHz.
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-ohm load resistance obtained at 150 GHz is 37.7 W, with a dc current density of 200 kA/sq cm, 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.
Radiation spectra have been obtained in order to calculate the frequency bandwidth and polarization of three microwave noise sources. Results were obtained in the 1-10-mm wavelength region using a lamellar grating Fourier transform spectrometer and a helium-cooled bolometer detector. A secondary transmission region was found to have an input current as well as a polarization dependence, despite the directional output of the waveguide antenna.
The results of a low sensitivity Radio Frequency Interference (RFI) survey carried out at the Venus Station of the Goldstone Communications Complex are reported. The data cover the spectral range from 1 GHz to 10.4 GHz with a 10-kHz instantaneous bandwidth. Frequency and power levels were observed using a sweep-frequency spectrum analyzer connected to a 1-m diameter antenna pointed at zenith. The survey was conducted from February 16, 1987 through February 24, 1987.
JPL has measured and calibrated a WR2.2 waveguide wafer probe from GGB Industries in order to allow for measurement of circuits in the 325-500 GHz range. Circuits were measured, and one of the circuits exhibited 10 dB of gain at 475 GHz. The MMIC circuit was fabricated at Northrop Grumman Corp. (NGC) as part of a NASA Innovative Partnerships Program, using NGC s 35-nm-gatelength InP HEMT process technology. The chip utilizes three stages of HEMT amplifiers, each having two gate fingers of 10 m in width. The circuits use grounded coplanar waveguide topology on a 50- m-thick substrate with through substrate vias. Broadband matching is achieved with coplanar waveguide transmission lines, on-chip capacitors, and open stubs. When tested with wafer probing, the chip exhibited 10 dB of gain at 475 GHz, with over 9 dB of gain from 445-490 GHz. Low-noise amplifiers in the 400-500 GHz range are useful for astrophysics receivers and earth science remote sensing instruments. In particular, molecular lines in the 400-500 GHz range include the CO 4-3 line at 460 GHz, and the CI fine structure line at 492 GHz. Future astrophysics heterodyne instruments could make use of high-gain, low-noise amplifiers such as the one described here. In addition, earth science remote sensing instruments could also make use of low-noise receivers with MMIC amplifier front ends. Present receiver technology typically employs mixers for frequency down-conversion in the 400-500 GHz band. Commercially available mixers have typical conversion loss in the range of 7-10 dB with noise figure of 1,000 K. A low-noise amplifier placed in front of such a mixer would have 10 dB of gain and lower noise figure, particularly if cooled to low temperature. Future work will involve measuring the noise figure of this amplifier.
This paper reviews the effects of precipitation on earth-space communication links operating the 10 to 35 GHz frequency range. Emphasis is on the quantitative prediction of rain attenuation and depolarization. Discussions center on the models developed at Virginia Tech. Comments on other models are included as well as literature references to key works. Also included is the system level modeling for dual polarized communication systems with techniques for calculating antenna and propagation medium effects. Simple models for the calculation of average annual attenuation and cross-polarization discrimination (XPD) are presented. Calculation of worst month statistics are also presented.
Design and development of low noise traveling wave amplifiers for 18 to 75 GHz frequency range
The selection of preferred frequency bands for deep space telecommunications in the 20 to 120 GHz range is discussed. The performance of links between Earth stations and stations in deep space is affected by the atmosphere of the Earth. Attenuation and emission by the atmosphere generally limits deep space telecommunications to frequencies below 20 GHz. There are, however, certain frequency bands in the 20 to 120 GHz range where atmospheric attenuation is low enough to permit links between Earth stations and deep space stations. Additionally there are certain other bands in the 20 to 120 GHz range that would be particularly suitable for links between an Earth orbiting relay station and deep space stations.
Studies of the Earth’s atmosphere require a comprehensive set of observations that rely on instruments flown on spacecraft, aircraft, and balloons as well as those deployed on the surface. Within NASA’s Goddard Space Flight Center (GSFC) Earth Sciences Division-Atmospheres, laboratories and offices maintain an active program of instrument system development and observational studies that provide: 1) information leading to a basic understanding of atmospheric processes and their relationships with the Earth’s climate system, 2) prototypes for future flight instruments, 3) instruments to serve as calibration references for satellite missions, and 4) instruments for future field validation campaigns that support ongoing space missions. Our scientists participate in all aspects of instrument activity, including component and system design, calibration techniques, retrieval algorithm development, and data processing systems. The Atmospheres Program has well-equipped labs and test equipment to support the development and testing of instrument systems, such as a radiometric calibration and development facility to support the calibration of ultraviolet and visible (UV/VIS), space-borne solar backscatter instruments. This document summarizes the features and characteristics of 46 instrument systems that currently exist or are under development. The report is organized according to active, passive, or in situ remote sensing across the electromagnetic spectrum. Most of the systems are considered operational in that they have demonstrated performance in the field and are capable of being deployed on relatively short notice. Other systems are under study or of low technical readiness level (TRL). The systems described herein are designed mainly for surface or airborne platforms. However, two Cubesat systems also have been developed through collaborative efforts. The Solar Disk Sextant (SDS) is the single balloon-borne instrument. The lidar systems described herein are designed to retrieve clouds, aerosols, methane, water vapor pressure, temperature, and winds. Most of the lasers operate at some wavelength combination of 355, 532, and 1064 nm. The various systems provide high sensitivity measurements based on returns from backscatter or Raman scattering including intensity and polarization. Measurements of the frequency (Doppler) shift of light scattered from various atmospheric constitutes can also be made. Microwave sensors consist of both active (radar) and passive (radiometer) systems. These systems are important for studying processes involving water in various forms. The dielectric properties of water affect microwave brightness temperatures, which are used to retrieve atmospheric parameters such as rainfall rate and other key elements of the hydrological cycle. Atmosphere radar systems operate in the range from 9.6 GHz to 94 GHz and have measurement accuracies from -5 to 1 dBZ; radiometers operate in the 50 GHz to 874 GHz range with accuracies from 0.5 to 1 degree K; conical and cross-track scan modes are used. Our passive optical sensors, consisting of radiometers and spectrometers, collectively operate from the UV into the infrared. These systems measure energy fluxes and atmospheric parameters such as trace gases, aerosols, cloud properties, or altitude profiles of various species. Imager spatial resolution varies from 37 m to 400 m depending on altitude; spectral resolution is as small as 0.5 nm. Many of the airborne systems have been developed to fly on multiple aircraft.
The author has identified the following significant results. Employing two FM-CW radar spectrometers, scattering data were acquired from stands of deciduous trees during the spring and autumn. The data suggest that the trees act as a volume scatter target particularly in the 7-18 GHz region. A comparison of data collected in spring and autumn indicates that the radar scattering coefficient, sigma deg, as measured in spring can be substantially larger (as much as 10 dB) than sigma deg as measured in the autumn.
A semi-empirical model for microwave backscatter from vegetation was developed and a complete set of canope attenuation measurements as a function of frequency, incidence angle and polarization was acquired. The semi-empirical model was tested on corn and sorghum data over the 8 to 35 GHz range. The model generally provided an excellent fit to the data as measured by the correlation and rms error between observed and predicted data. The model also predicted reasonable values of canopy attenuation. The attenuation data was acquired over the 1.6 to 10.2 GHz range for the linear polarizations at approximately 20 deg and 50 deg incidence angles for wheat and soybeans. An attenuation model is proposed which provides reasonable agreement with the measured data.
We present measurements of prototype thin film Al microwave kinetic inductance detectors (MKIDs) intended for application in the sub-mm astronomy balloon experiment EXCLAIM. The device we show is dark, or non-optically coupled, and contains 16 coplanar waveguide (CPW) resonators etched into a 261 nm sputter deposited Al layer on a Si wafer. The resonators span the f0 = 3.5 - 4 GHz range, and include both lambda=2 and lambda=4 resonators. Each resonator is coupled to the feedline using one of three alternating coupling designs. We performed transmission line measurements of the device for a series of excitation powers ranging from -90 dBm to -30 dBm, and at a series of base temperatures ranging from 73 mK to 400 mK. We observed quality factors of up to Qi 107 at a base temperature of 73 mK. The lambda=2 and lambda=4 resonators performed similarly, achieving comparable Qi values. The results of these measurements are actively informing the fi nal design of the EXCLAIM instrument. EXCLAIM will incorporate six spectrometers, each containing an array of over 300 resonators in the 420-540 GHz range.
Millimeter wave transmission measurements through YBa2Cu3O(7-delta) thin films on MgO, ZrO2 and LaAlO3 substrates, are reported. The films (approx. 1 micron) were deposited by sequential evaporation and laser ablation techniques. Transition temperatures T sub c, ranging from 89.7 K for the Laser Ablated film on LaAlO3 to approximately 72 K for the sequentially evaporated film on MgO, were obtained. The values of the real and imaginary parts of the complex conductivity, sigma 1 and sigma 2, are obtained from the transmission data, assuming a two fluid model. The BCS approach is used to calculate values for an effective energy gap from the obtained values of sigma sub 1. A range of gap values from 2 DELTA o/K sub B T sub c = 4.19 to 4.35 was obtained. The magnetic penetration depth is evaluated from the deduced values of sigma 2. These results are discussed together with the frequency dependence of the normalized transmission amplitude, P/P sub c, below and above T sub c.
Data collected with the Advanced Microwave Moisture Sounder (AMMS), which operates in the 183.3 GHz range, are compared to measurements collected at 22 GHz in order to show that the 183 GHz measurements are more sensitive to total precipitable water (W) values than the 22 GHz measurements. Radiative transfer calculations for the upwelling microwave emission from the ocean surface were performed at the AMMS frequencies with a variety of atmospheric temperature and humidity profiles. The derived brightness temperatures at these frequencies are compared with W values derived from the humidity profiles. It is observed that the sensitivity between the brightness temperatures and W values at the AMMS channel is greater than 130 K/g per sq cm and 12 K/g per sq cm for the 22 GHz frequency.
The microwave dielectric behavior of vegetation materials is examined as a function of water content, microwave frequency, and temperature. Dielectric spectra for various types of vegetation, such as leaves, stalks, and trunks at various moisture conditions, were measured using a coaxial probe technique. The basic features and operation of the coaxial probe system are described. Examples of dielectric measurements for the vegetation materials are presented, and the relation between temperature and the dielectric constant is studied. The development of a dual-dispersion model that accounts for the dielectric properties of water in both free and bound conditions is described. The applicability of the model is evaluated by comparing it with the dielectric data; good correlation is observed between the model and the data over a wide range of moisture conditions and over the 0.2-20 GHz range.
The printed circuit and GaAs beam lead technology-based, low noise integrated receiver presented was developed for low cost space communications and operates in the 59-64 GHz range, using a phase-locked Gunn oscillator at 51.5 GHz. An IF output of 7.5-12.5 GHz is obtained. With the exception of the IF amplifier, and of the E-plane technology-based RF preselect filter, all circuits of the device employ suspended stripline construction.
Monolithic (MMIC) and discrete transistor (MIC) low noise amplifiers are compared on the basis of performance, cost, and reliability. The need for cryogenic LNA's for future large microwave arrays for radio astronomy is briefly discussed and data is presented on a prototype LNA for the 1 to 10 GZH range along with a very wideband LNA for the 1 to 60 GHz range.