A 0.83-2.5-GHz continuously tunable quadrature VCO

A quadrature VCO with /spl plusmn/50% continuous 0.83-2.5-GHz tuning range is presented. It is based on a core LC-QVCO with /spl plusmn/20% tuning range, a single sideband mixer (SSBM), two frequency dividers and a multiplexer. The circuit has been implemented in a 0.13-/spl mu/m 1.2-V CMOS technology. The additional area with respect to the core LC-QVCO is 100 /spl mu/m/spl times/100 /spl mu/m. Quadrature error is less than 2/spl deg/; the phase noise is less than -120 dBc/Hz @ 1 MHz over the whole tuning range and is mainly due to the LC-QVCO. Spurs are more than 34 dB below the fundamental in the worst case.     

A 10-GHz Single Sideband Modulator With 1-kHz Frequency Shift (Correspondence)

A single sideband modulator which frequency shifts a 10-GHz signal by 1 kHz and which suppresses the carrier and unwanted sideband by 65 dB and >57 dB, respectively, with respect to the wanted sideband, is described. The modulator comprises two commercially available double sideband modulators and a readily constructed high-pass filter. Using the modulator in one arm of a microwave bridge, phase shtits and changes in attenuation of <1/spl deg/ and 0.05 dB have been measured; the low modulating frequency allows audio-frequency circuitry to be used to measure the phase shift and attenuation.     

A 2.5-GHz eight-phase VCO in SiGe BiCMOS technology

We present a 2.5-GHz voltage-controlled oscillator (VCO) with eight equally distributed phases derived from a 10-GHz LC VCO. Stochastic and static phase errors were obtained by spectrum analyzer measurements in conjunction with an on-chip single-sideband mixer. From the measured phase noise spectrum, we predict an absolute rms jitter contribution of 130 fs in a 2-MHz bandwidth phase-locked loop. A static phase error of less than 0.7/spl deg/ was deduced from the sideband suppression. The eight-phase VCO is tunable from 2.35 to 2.85 GHz and draws 16 mA from a 2.0-V supply. Possible applications include clock and data recovery of a 10-Gb/s signal in a fiber-optic receiver as well as high-precision image rejection receivers and I/Q direct up-converters for radio-frequency applications.     

Polarimetric microwave wind radiometer model function and retrieval testing for WindSat

A geophysical model function (GMF), relating the directional response of polarimetric brightness temperatures to ocean surface winds, is developed for the WindSat multifrequency polarimetric microwave radiometer. This GMF is derived from the WindSat data and tuned with the aircraft radiometer measurements for very high winds from the Hurricane Ocean Wind Experiment in 1997. The directional signals in the aircraft polarimetric radiometer data are corroborated by coincident Ku-band scatterometer measurements for wind speeds in the range of 20-35 m/s. We applied an iterative retrieval algorithm using the polarimetric brightness temperatures from 18-, 23-, and 37-GHz channels. We find that the root-mean-square direction difference between the Global Data Assimilation System winds and the closest WindSat wind ambiguity is less than 20/spl deg/ for above 7-m/s wind speed. The retrieval analysis supports the consistency of the Windrad05 GMF with the WindSat data.     

High-stability L-band radiometer measurements of saltwater

L-band radiometer brightness temperature measurements of a saltwater pond were made as a function of salinity and temperature. A precision L-band radiometer with stability better than 0.1 K per day was used for these measurements. The L-band measurements are in good agreement with three dielectric constant models over a temperature range from 8/spl deg/C to 32/spl deg/C and a salinity range from 25-40 psu. Based on this experiment, these dielectric models will provide an excellent basis for the algorithm development and design of the future National Aeronautics and Space Administration Aquarius satellite mission.     

On the feasibility of CMOS multiband phase shifters for multiple-antenna transmitters

We present the design of an integrated multiband phase shifter in RF CMOS technology for phased array transmitters. The phase shifter has an embedded classical distributed amplifier for loss compensation. The phase shifter achieves a more than 180/spl deg/ phase tuning range in a 2.4-GHz band and a measured more than 360/spl deg/ phase tuning range in both 3.5-GHz and 5.8-GHz bands. The return loss is less than -10dB at all conditions. The feasibility for transmitter applications is verified through measurements. The output power at a 1-dB compression point (P/sub 1 dB/) is as high as 0.4dBmat 2.4GHz. The relative phase deviation around P/sub 1 dB/ is less than 3/spl deg/. The design is implemented in 0.18-/spl mu/mRF CMOS technology, and the chip size is 1200/spl mu/m /spl times/ 2300 /spl mu/m including pads.     

Observations of tropical cyclone structure from WindSat

Passive microwave (PMW) radiometric observations of clouds from multichannel imaging sensors onboard low Earth-orbiting environmental satellites are now a vital operational dataset. The first operational passive microwave sensor was the Special Sensor Microwave/Imager onboard the Defense Meteorological Satellite Program satellites, which has been gathering hydrological data records since 1987, and continued with the Tropical Rainfall Measuring Mission (TRMM) and the Advanced Microwave Scanning Radiometer onboard Aqua. These sensors view the underlying scene with an Earth incidence angle near 53/spl deg/ and with a variable azimuthal angle, depending upon the orbit direction and scan position. The WindSat sensor onboard the Coriolis satellite, launched in January 2003, is a five-channel polarimetric PMW radiometer designed to optimize ocean surface wind vector retrievals. While it does not have 85-GHz channels, an added feature is its unique fore-aft viewing capability across a portion of its fore scan swath. This provides a view of the underlying scene from two separate azimuthal directions, which provides added information on the three-dimensional (3-D) structure of clouds and their evolution. In this paper, we compare WindSat and TRMM Precipiation Radar observations of tropical cyclones (TCs) with Monte Carlo radiative transfer simulations performed on idealized 3-D convective cloud structures. The TC 3-D structure and possible tilt in the convective cloud structure are inferred from the difference between the 37-GHz equivalent blackbody brightness temperatures (T/sub B/) from the corresponding fore and aft view observations. The information gained from this analysis is important since asymmetries in the cloud vertical and horizontal structure may be an indication of upper level wind shear, which plays a major role in influencing changes of the TC intensity.     

Deep-space calibration of the WindSat radiometer

The WindSat microwave polarimetric radiometer consists of 22 channels of polarized brightness temperatures operating at five frequencies: 6.8, 10.7, 18.7, 23.8, and 37.0 GHz. The 10.7-, 18.7-, and 37.0-GHz channels are fully polarimetric (vertical/horizontal, /spl plusmn/45/spl deg/ and left-hand and right-hand circularly polarized) to measure the four Stokes radiometric parameters. The principal objective of this Naval Research Laboratory experiment, which flys on the USAF Coriolis satellite, is to provide the proof of concept of the first passive measurement of ocean surface wind vector from space. This paper presents details of the on-orbit absolute radiometric calibration procedure, which was performed during of a series of satellite pitch maneuvers. During these special tests, the satellite pitch was slowly ramped to +45/spl deg/ (and -45/spl deg/), which caused the WindSat conical spinning antenna to view deep space during the forward (or aft portion) of the azimuth scan. When viewing the homogeneous and isotropic brightness of space (2.73 K) through both the main reflector and the cold-load calibration reflector, it is possible to determine the absolute calibration of the individual channels and the relative calibration bias between polarimetric channels. Results demonstrate consistent and stable channel calibrations (with very small brightness biases) that exceed the mission radiometric calibration requirements.     

Development of multiband phase shifters in 180-nm RF CMOS technology with active loss compensation

We present the design and development of a novel integrated multiband phase shifter that has an embedded distributed amplifier for loss compensation in 0.18-/spl mu/m RF CMOS technology. The phase shifter achieves a measured 180/spl deg/ phase tuning range in a 2.4-GHz band and a measured 360/spl deg/ phase tuning range in both 3.5- and 5.8-GHz bands. The gain in the 2.4-GHz band varies from 0.14 to 6.6 dB during phase tuning. The insertion loss varies from -3.7 dB to 5.4-dB gain and -4.5 dB to 2.1-dB gain in the 3.5- and 5.8-GHz bands, respectively. The gain variation can be calibrated by adaptively tuning the bias condition of the embedded amplifier to yield a flat gain during phase tuning. The return loss is less than -10 dB at all conditions. The chip size is 1200 /spl mu/m/spl times/2300 /spl mu/m including pads.     

A Ka-band InP MMIC 180/spl deg/ phase switch

A new type of Ka band (26 to 36 GHz) 180 degree phase switch (bi-phase modulator) monolithic microwave integrated circuit has been developed for the EC funded FARADAY radio astronomy project. This integral component forms part of a chip set for a very low noise switching radiometer operating at a temperature of approximately 15 K. To maximize the sensitivity of the radiometer lattice-matched indium phosphide HEMT technology has been used: all of the active components of the radiometer, with the exception of the detectors, have been manufactured on a single wafer process. Design principles are described, together with a comparison of modeled and measured results. The results show an average insertion loss of 3.5 dB, return loss of better than 10 dB and an average phase difference close to 170/spl deg//spl plusmn/10/spl deg/ the 26-36 GHz band.     

A subharmonically injected LC delay line oscillator for 17-GHz quadrature LO generation

An injection-locked delay line oscillator multiplies a 5-6-GHz input by 3 to generate I/Q LO signals for 17-GHz wireless networking applications. I/Q errors caused by asymmetric injection are minimized by symmetric injection via a passive polyphase prefilter. Passive delay lines set the measured free-running frequency of the LC ring oscillator to 16.24 GHz. The measured locking range for a 0 dBm (50 /spl Omega/) input is 14.6-17.86 GHz. Input-to-output phase noise degradation is negligible, and I/Q amplitude and phase errors are <0.17 dB and <2/spl deg/, respectively. Power consumption of the 1.2/spl times/1.4 mm/sup 2/ 0.2 /spl mu/m SiGe BiCMOS testchip (excluding buffers) is 22 mW at 2.2 V.     

Airborne Imaging System Using a Cryogenic 90-Ghz Receiver

A cryogenic 90-GHz receiver has heen developed with a noise figure of 2.36 dB ((double sideband) (DSB)) and an instantaneous band-width of 1.2 GHz. The cooled front-end consists of a Schottky-barrier mixer followed by a GaAs FET IF amplifier. The radiometer is small in size and weighs only 52 kg, including the refrigerator system. It is part of an airborne imaging system, that has been fight-tested aboard a Dornier Do 28 aircraft. First test results are presented.     

A 60-GHz point-to-multipoint millimeter-wave fiber-radio communication system

A 60-GHz point-to-multipoint wireless access link with data rate of 156 Mb/s incorporating 60-GHz transceiver modules and full-duplex fiber-optic millimeter-wave transmission is developed for short-range applications such as indoor wireless local area networks and intelligent transport systems. For compact system configuration, a small-size millimeter-wave transceiver module with planar antennas is developed. The transceiver module is based on broadband planar integration and packaging of millimeter-wave circuits. The RF output power is +10 dBm and the measured 3-dB antenna beamwidth is 30/spl deg/. The total size of the developed 60-GHz transceiver module, except input and output connectors, is 50 mm /spl times/ 75 mm /spl times/ 35 mm. A point-to-point full duplex fiber-optic configuration is extended to the scheme with multiple access points (APs) by using a tree coupler and a dense wavelength division multiplexing multiplexer. The AP has a simple configuration without frequency conversion. The bit error rate and packet error rate performances of the 60-GHz fiber-radio access link are evaluated. Furthermore, the effect of the extension to the scheme with multiple APs is investigated.     

A multiband /spl Delta//spl Sigma/ fractional-N frequency synthesizer for a MIMO WLAN transceiver RFIC

This work presents a shared fractional-N synthesizer used by two dual-band 802.11 radios integrated on a single chip for 2/spl times/2 multiple-input multiple-output (MIMO) applications. Additional 2/spl times/2 MIMO chips can be used in a system by phase synchronizing the signal paths through a bidirectional LO porting scheme developed for this application. This synthesizer was fully integrated with the exception of an off-chip loop filter. The synthesizer is a /spl Delta//spl Sigma/-based fractional-N frequency synthesizer with three on-chip LC tuned VCOs to cover the entire frequency bands specified in the IEEE 802.11a/b/g and Japanese WLAN standards. The radio uses a variable IF frequency so that both the RF LO and IF LO can be derived from a single synthesizer saving chip area and power. The synthesizer includes a programmable second/third-order /spl Delta//spl Sigma/ noise shaper, a phase frequency detector, a differential charge pump, and a 6-bit multimodulus divider (MMD). The nominal jitter from 100 Hz to 10 MHz is 0.63-0.86/spl deg/ rms in the 5-GHz band and 0.35-0.43/spl deg/ rms in the 2.4-GHz band. The maximum frequency deviation of the synthesizer when enabling the transmitter is less than 150 kHz and the frequency error settles to 2 kHz in less than 12 /spl mu/s. For MIMO applications requiring more than two full paths, a single synthesizer on one die can be used to generate the LOs for all other radios integrated in different dies.     

A single-chip dual-band direct-conversion IEEE 802.11a/b/g WLAN transceiver in 0.18-/spl mu/m CMOS

This paper presents a single-chip dual-band CMOS direct-conversion transceiver fully compliant with the IEEE 802.11a/b/g standards. Operating in the frequency ranges of 2.412-2.484 GHz and 4.92-5.805 GHz (including the Japanese band), the fractional-N PLL based frequency synthesizer achieves an integrated (10 kHz-10 MHz) phase noise of 0.54/spl deg//1.1/spl deg/ for 2/5-GHz band. The transmitter error vector magnitude (EVM) is -36/-33 dB with an output power level higher than -3/-5dBm and the receiver sensitivity is -75/-74 dBm for 2/5-GHz band for 64QAM at 54 Mb/s.     

An experimental study of harmonic SIS mixing at 205-235 GHz

A 230-GHz subharmonically pumped waveguide mixer employing superconducting tunnel junctions has been developed. We present, in this paper, an experimental study of harmonic superconductor-insulator-superconductor (SIS) mixing at 230 GHz, focusing mainly on its noise behavior. The mixer has a double-tuned waveguide structure and employs an array of four 1.7-/spl mu/m/sup 2/ Nb-AlOx-Nb SIS junctions in series, with /spl omega/R/sub n/C/sub j//spl sim/3 at 230 GHz. Harmonic quantum mixing occurred over an experimental frequency range of 205-235 GHz (local oscillator: 112.5-117.5 GHz), exhibiting corresponding double sideband noise temperatures of lower than 150 K, with a lowest value of 75 K at /spl sim/230 GHz. The measured mixer noise is believed to be the lowest yet reported for a mixer using subharmonic-pump configuration at this frequency. A phenomenon that we attribute to the third harmonic SIS mixing has also been observed.     

A Microwave System for the Controlled Production of Local Tumor Hyperthermia in Animals

A microwave system was designed and constructed which provides controlled, localized hyperthermia in the tumors of four experimental animals. The components of the system are a 2.45-GHz microwave source, a four-way power-dividing network and reflected power monitor, a temperature-controlled microwave power regulator, and small direct-contact microwave applicators. Adjustment of the temprature control results in elevated temperatures in the centers of tumors which can be maintained to within /spl plusmn/ 0.1/spl deg/C without production of significant whole body hyperthermia.The temperatures at the edges of the locally heated tumors were found to vary within /spl plusmn/1.0/spl deg/C of the center temperature. The system is currently being used to evaluate the therapeutic potential of sustained Iocalized hyperthermia in small tumors implanted subcutaneously in mice.     

Thermally controlled wavelength locker integrated in widely tunable SGDBR-LD module

A sampled-grating distributed Bragg reflector laser module having an integrated multiwavelength locker has been developed and evaluated. The uniquely designed wavelength locker made of thermally controlled etalon has provided uniform wavelength monitoring and very stable wavelength locking in the 188-ITU grid channels (37 nm) with 25-GHz spacing. Over the case temperature from -5/spl deg/C to 65/spl deg/C, the laser wavelength was locked within /spl plusmn/0.5 GHz, and the total power consumption of the module was less than 4 W.     

A new active RF phase shifter using variable gain, drain Voltage controlled PHEMTs:A 2.4-GHz ISM implementation

Phase shifters operating at RF bands are an essential component of phased and adaptive arrays circuits. In this letter, an active phase shifter is proposed, using vector summing of an in-phase and a quad-phase replica of the incoming signal. The proposed scheme was designed and implemented using a Wilkinson power combiner/divider, a branch line hybrid coupler and single-stage variable gain amplifiers (VGAs), achieving continuous phase shift within the range of [0/spl deg/, 90/spl deg/]. The manufactured prototype is suitable for WLAN operations in the 2.4-GHz ISM band. Details of the phase shifter design and experimental results are presented.     

A 5-6-GHz polyphase filter with tunable I/Q phase balance

A tunable polyphase filter with integrated input and output buffers was designed and fabricated in a 0.4 /spl mu/m SiGe BiCMOS technology with a 5-6-GHz bandwidth. Series tunable capacitors (varactors) provide phase tunability for the differential quadrature outputs of the polyphase filter. The tunable phase can be used to improve image rejection in Weaver or Hartley architectures, or mitigate in-phase and quadrature (I/Q) phase error in direct conversion or low-IF receivers. The die area of the fabricated circuit with pads is 920 /spl mu/m/spl times/ 755 /spl mu/m. Based on measurements, approximately 15/spl deg/ of I/Q phase imbalance can be tuned out using the fabricated polyphase filter, proving the concept of tunable phase. To the authors' knowledge, this is the first reported tunable I/Q balance polyphase network.