A 5.2 GHz CMOS I/Q Modulator With Integrated Phase Shifter for Beamforming

This paper presents the design of an I/Q modulator with integrated phase shifter for beamforming. It is targeted at 802.11a WLAN. An efficient beamforming architecture with a linearly controlled 360^deg phase shifting range is proposed for linear transmitters. The phase shifting takes place in the local oscillator path at three times lower frequency than the carrier. The phase shifters are implemented as vector modulators in an efficient way by utilizing a current reuse technique. All control currents are provided by a single current steering digital to analog converter by means of time multiplexed sample and hold circuits. The circuit, implemented in 0.25 mum CMOS technology, has a 1 dB output compression point of -7.1 dBm and consumes 61 mA. It has a phase shifting resolution of 10^deg with a differential accuracy of 2^deg.     

Splay-to-Bend Transition-Free Reactive Monomer Modified Pi-Cell

A reactive monomer modified Pi-cell (RMM-Pi-cell) comprising a layer of liquid crystal (LC) reactive monomer on one surface was prepared to control the surface pretilt angle. The simulation results suggested that a transition-free Pi-cell can be prepared by asymmetrical cell with one 8 ^deg pretilt angle and the other surface greater than 47^deg when the cell gap was smaller than 4 mum. The nematic reactive monomer layer has a molecular average tilt angle over 80^deg which allowed the LC molecules to be arranged in a favored bend state in the asymmetrical cell. The critical voltages cannot be found in all 3-mu m RMM-Pi-cells. The cell retardation data confirmed the initial bend orientation with zero voltage applied. Moreover, the light leakage of dark state was reduced. The contrast ratio of RMM-Pi-cell was improved by a factor of 11 compared with an original Pi-cell without using compensation film.     

Beam-switchable scanning leaky-wave antenna

A beam-switchable scanning leaky-wave antenna (LWA) has been developed. This LWA with a two-terminal feeding microstrip line structure is integrated with a single port double throw (SPDT) switch as a control circuit. In dual-beam mode, the scanning angle is steered over a range of 36-64° for the right-hand beam and 144-116° for the left-hand beam. In one-beam mode, the scanning angle is measured over 20° for the right-hand beam. The measured result shows that we can change from the one-beam mode to the dual-beam mode electronically by controlling the on/off status of an SPDT switch, in contrast to the case for traditional leaky-wave antennas     

Numerical analysis of bodyworn UHF antenna systems

Bodyworn antennas are found in a wide range of medical, military and personal communication applications, yet reliable communication from the surface of the human body still presents a range of engineering challenges. At UHF and microwave frequencies, bodyworn antennas can suffer from reduced efficiency due to electromagnetic absorption in tissue, radiation pattern fragmentation and variations in feed-point impedance. The significance and nature of these effects are system specific and depend on the operating frequency, propagation environment and physical constraints on the antenna itself. This paper describes how numerical electromagnetic modelling techniques such as FDTD (finite-difference time-domain) can be used in the design of bodyworn antennas. Examples are presented for 418 MHz, 916·5 MHz and 2·45 GHz, in the context of both biomedical signalling and wireless personal-area networking applications such as the Bluetooth^TM wireless technology     

Near-field corrections to site attenuation

The theoretical model used for calculating normalized site attenuation for broadband antennas in ANSI C63.4-1992 and for antenna calibration in ANSI C63.5-1988 includes only the radiation terms in the electric field. The omission of the near field terms leads to errors of as much as 2.0 dB at 30 MHz for horizontally polarized antennas separated by 3 m. Corrected values of normalized site attenuation and E _D^max are presented for the 30-300 MHz frequency range     

A Quiet Standing Index for Testing the Postural Sway of Healthy and Diabetic Adults Across a Range of Ages

A quiet standing index is developed for tracking the postural sway of healthy and diabetic adults over a range of ages. Several postural sway features are combined into a single composite feature C that increases with age a. Sway features are ranked based on the r ²-values of their linear regression models, and the composite feature is a weighted sum of selected sway features with optimal weighting coefficients determined using principal component analysis. A performance index based on both reliability and sensitivity is used to determine the optimal number of features. The features used to form C include power and distance metrics. The quiet standing index is a scalar that compares the composite feature C to a linear regression model f(a) using C ^'(a) = C/f(a). For a motionless subject, C ^' = 0, and when the composite feature exactly matches the healthy control (HC) model, C ^' = 1. Values of C ^' >> 1 represent excessive postural sway and may indicate impaired postural control. Diabetic neurologically intact subjects, nondiabetic peripheral neuropathy subjects (PN), and diabetic PN subjects (DPN) were evaluated. The quiet standing indexes of the PN and DPN groups showed statistically significant increases over the HC group. Changes in the quiet standing index over time may be useful in identifying people with impaired balance who may be at an increased risk of falling.     

The Herschel and Planck Space Telescopes

The European Space Agency launches in 2009 two flagship missions in the domain of submillimeter space astronomy. The Herschel Space Observatory is a common user facility featuring a 3.5 m aperture Cassegrain telescope passively cooled to 80 K. The Planck survey mission includes a 1.5 m unobscured aperture off-axis aplanatic telescope passively cooled to 40 K. Herschel will make pointed target observations of astrophysical objects and phenomena in the frequency range 448 GHz to 5.3 THz (or 672 to 55 mum wavelength). Planck, on the other hand, will map the entire sky by strip scanning at a spin rate of one revolution per minute covering a frequency bandwidth of 30-857 GHz (or wavelength from 10 to 0.35 mm). Its spin axis is pointed antisunward and can be oriented within a 10deg cone around that direction. The telescope line of sight is fixed at an angle of 85^deg to the spacecraft spin-axis. This paper describes briefly the specific telescopes developed for each mission; their design characteristics, the development process for each, their achieved performances (from on ground testing) and their expected performances in flight.     

Argus: An L-Band All-Sky Astronomical Surveillance System

Argus is an experimental antenna array system designed to demonstrate all-sky monitoring for transient signals in the frequency range 1200-1700 MHz. It currently consists of 22 broadband spiral antennas (expandable to 32) which are individually instrumented, digitized, and analyzed in an attempt to detect and localize both broadband and narrowband astronomical transients. In this paper, we describe the design of the instrument. Notable features include a novel array data aggregation architecture, a detection algorithm which does not require accurate calibration or detailed knowledge of the array manifold, and very low per-element cost of about US$1 k/element. A sensitivity of at least 6.6times10^-22 Wm^-2 Hz^-1 = 66 kJy (zenith at 1700 MHz for a 209 ms observation with 60 kHz bandwidth) is achieved for the system as implemented. Performance is demonstrated in an experiment in which the Sun is detected, localized, and tracked as it moves across the sky. Other experiments confirming the functionality of Argus as an all-sky surveillance system are summarized.     

A low-power-consuming SOM for wireless communications

This paper presents theoretical and experimental results of a low-power-consuming hybrid push-pull self-oscillating mixer (SOM) circuit at the UHF frequency band. The frequency-stable SOM circuit is designed and fabricated using matched-pair Si bipolar junction transistors and high-Q resonators, where measured phase noise of this free-running voltage-controlled oscillator is -101.2 dBc/Hz at 100-kHz offset. A 20-dB up-conversion gain, a compression dynamic range (CDR) of 65 dB·MHz, and a spurious-free dynamic range of 50 dB·MHz ^2/3 are also measured for the mixer portion of this SOM. Moreover, a down-conversion gain of ≈-2 dB with a CDR of 100 dB·MHz is also measured     

Basic Element for Square Kilometer Array Training (BEST): Evaluation of the Antenna Noise Temperature

In this paper, a rigorous procedure for calculating the antenna noise temperature is described, and applied to the antenna of BEST-1 (basic element for SKA training - version 1), which represents one of the SKA (square kilometer array) demonstrators. The SKA will be a new-generation radio telescope, with a collecting area 50 times larger than the area of today's largest radio telescope. BEST is the Italian reduced-scale SKA demonstrator, based on the re-instrumentation of about 8000 m² of the Northern Cross radio telescope, built with cylindrical parabolic antennas. In order to perform the antenna-temperature analysis, an electromagnetic tool to accurately evaluate the antenna pattern in the whole space surrounding the antenna itself is required. We used the commercial software GRASP8, developed by TICRA, to characterize reflector antennas. The antenna temperature was evaluated using the guideline adopted by the Antenna Task Force of the SKA world consortium. For BEST-1 at 408 MHz, we found an antenna temperature equal to 30 K in the zenith direction and 60 K at the horizon. The numerical results have been verified through several celestial calibration radio sources.     

A patch antenna design for application in a phased-array head and neck hyperthermia applicator

In this paper, we describe a specifically designed patch antenna that can be used as the basis antenna element of a clinical phased-array head and neck hyperthermia applicator. Using electromagnetic simulations we optimized the dimensions of a probe-fed patch antenna design for operation at 433 MHz. By several optimization steps we could converge to a theoretical reflection of -38 dB and a bandwidth (-15 dB) of 20 MHz (4.6%). Theoretically, the electrical performance of the antenna was satisfactory over a temperature range of 15 degrees C-35 degrees C, and stable for patient-antenna distances to as low as 4 cm. In an experimental cylindrical setup using six elements of the final patch design, we measured the impedance characteristics of the antenna 1) to establish its performance in the applicator and 2) to validate the simulations. For this experimental setup we simulated and measured comparable values: -21 dB reflection at 433 MHz and a bandwidth of 18.5 MHz. On the basis of this study, we anticipate good central interference of the fields of multiple antennas and conclude that this patch antenna design is very suitable for the clinical antenna array. In future research we will verify the electrical performance in a prototype applicator.     

A fully integrated low-noise 1-GHz frequency synthesizer design formobile communication application

This paper describes a fully monolithic phase-locked loop (PLL) frequency synthesizer circuit implemented in a standard 0.8-μm CMOS technology. To be immune to noise, all the circuits in the synthesizer use differential schemes with the digital parts designed by static logic. The experimental voltage controlled oscillator (VCO) has a center frequency of 800 MHz and a tuning range of ±25%. The measured frequency synthesizer performance has a frequency range from 700 MHz to 1 GHz with -80 dBc/Hz phase noise at a 100 kHz carrier offset. With an active area of 0.34 mm², the test chip consumes 125 mW at maximum frequency from a 5 V supply. The only external components are the supply decoupling capacitors and a passive filter     

The Design of Low LO-Power 60-GHz CMOS Quadrature-Balanced Self-Switching Current-Mode Mixer

This letter describes the analysis and measurement of a complementary metal-oxide semiconductor (CMOS) quadrature-balanced current-mode mixer with a 90^deg branch-line hybrid coupler and self-switching current-mode devices. The proposed mixer, using 0.13 mum 1P8M CMOS technology, can downconvert a 60 GHz RF signal to a 2 GHz intermediate frequency (IF) signal, with a local-oscillator power of 0 dBm at 58 GHz. In the design, the mixer had a single-end conversion gain of 1 dB and an input-referred 1 dB compression point of 2 dBm. The LO-RF isolation of the mixer can achieve -37 dB while using 3 mA from a supply voltage of 1.2 V.     

A CMOS transconductor with 80-dB SFDR up to 10 MHz

A CMOS transconductor uses resistors at the input and an OTA in unity-gain feedback to achieve 80-dB spurious-free dynamic range (SFDR) for 3.6-V_pp differential inputs up to 10 MHz. The combination of resistors at the input and negative feedback around the operational transconductance amplifier (OTA) allows this transconductor to accommodate a differential input swing of 4 V with a 3.3-V supply. The total harmonic distortion (THD) of the transconductor is -77 dB at 10 MHz for a 3.6-V_pp differential input and third-order intermodulation spurs measure less than -79 dBe for 1.8-V_pp differential inputs at 1 MHz. The transconductance core dissipates 10.56 mW from a 3.3-V supply and occupies 0.4 mm² in a 0.35-μm CMOS process     

2-D periodic leaky-wave antennas-part I: metal patch design

The far-field radiation characteristics of a two-dimensional (2-D) periodic leaky-wave antenna (LWA) constructed from a periodic array of metal patches on a grounded dielectric substrate is investigated. A simple dipole source is used as the excitation. Reciprocity together with a periodic spectral-domain method of moments is used to calculate the far-field pattern. Design rules for the scan angle, the substrate dielectric constant, and the periodicity are provided. Finally, a comparison of the 2-D periodic LWA and a dielectric-layer LWA is given to show the similar performance of the two antennas.     

Effect of unit-cell size on performance of composite right/left-handed transmission line based leaky-wave antenna

The leakage rate and the scanning ability of composite right/left-handed transmission line based leaky-wave antennas (LWA) is investigated. It is demonstrated how the leakage rate is altered with unit-cells of different sizes. It is observed that the LWA with smaller unit-cells exhibits lower rate of leakage and higher gain at a cost of reduced bandwidth.     

A 0.3-μm CMOS 8-Gb/s 4-PAM serial link transceiver

An 8-Gb/s 0.3-μm CMOS transceiver uses multilevel signaling (4-PAM) and transmit preshaping in combination with receive equalization to reduce intersymbol interference due to channel low-pass effects. High on-chip frequencies are avoided by multiplexing and demultiplexing the data directly at the pads. Timing recovery takes advantage of a novel frequency acquisition scheme and a linear phase-locked loop that achieves a loop bandwidth of 35 MHz, phase margin of 50°, and capture range of 20 MHz without a frequency acquisition aid. The transmitted 8 Gb/s data are successfully detected by the receiver after a 10-m coaxial cable. The 2×2 mm² chip consumes 1.1 W at 8 Gb/s with a 3-V supply     

The Atacama Large Millimeter/Submillimeter Array

The Atacama Large Millimeter/Submillimeter Array (ALMA) is an international radio telescope under construction in the Atacama Desert of northern Chile. ALMA is situated on a dry site at 5000 m elevation, allowing excellent atmospheric transmission over the instrument wavelength range of 0.3-10 mm. ALMA will consist of two arrays of high-precision antennas. One, of up to 64 12-m-diameter antennas, is reconfigurable in multiple patterns ranging in size from 150 m up to ~ 15 km. A second array is composed of a set of four 12-m and 12 7-m antennas operating in one of two closely packed configurations ~ 50 m in diameter. The instrument will provide both interferometric and total-power astronomical information on atomic, molecular, and ionized gas and dust in the solar system, our galaxy, and the nearby to high-redshift universe. In this paper, we outline the scientific drivers, technical challenges, and planned progress of ALMA.     

High-performance phase locking of wide linewidth semiconductorlasers by combined use of optical injection locking and opticalphase-lock loop

The requirement for narrow linewidth lasers or short-loop propagation delay makes the realization of optical phase-lock loops using semiconductor lasers difficult. Although optical injection locking can provide low phase error variance for wide linewidth lasers, the locking range is restricted by stability considerations. Theoretical and experimental results for a system which combines both techniques so as to overcome these limitations, the optical injection phase-lock loop (OIPLL), are reported. Phase error variance values as low as 0.006 rad ² (500 MHz bandwidth) and locking ranges exceeding 26 GHz were achieved in homodyne OIPLL systems using DFB lasers of summed linewidth 36 MHz, loop propagation delay of 15 ns and injection ratio less than -30 dB. Phase error variance values as low as 0.003 rad² in a bandwidth of 100 MHz, a mean time to cycle slip of 3×10¹⁰ s and SSB noise density of -94 dBc/Hz at 10 kHz offset were obtained for the same lasers in an heterodyne OIPLL configuration with loop propagation delay of 20 ns and injection ratio of -30 dB     

Non-Foster Impedance Matching of Electrically-Small Antennas

Electrically-small antennas present high-Q impedances characterized by large reactances and small radiation resistances. For such antennas, the effectiveness of passive matching is severely limited by gain-bandwidth theory, which predicts narrow bandwidths and/or poor gain. With receivers, the inability to resolve this impedance mismatch results in poor signal-to-noise (S/N) ratio, as compared to using a full-size antenna. With transmitters, the consequence is poor power efficiency. However, in many applications full-size antennas are impractical, and a means is required to effectively match their electrically-small counterparts. This paper presents the technique of non-Foster impedance matching, which employs active networks of negative inductors and capacitors to bypass the restrictions of gain-bandwidth theory. We first review the origins and development of non-Foster impedance matching, and then present experimental results for the non-Foster impedance matching of electrically-small dipoles and monopoles. For receivers, our best measurements on the antenna range demonstrate up to 20 dB improvement in S/N over 20–120 MHz; for transmitters, we show a power efficiency improvement which exceeds a factor of two over an 5% bandwidth about 20 MHz with an average signal power of 1 W to the radiation resistance.