RF Communication Systems Research Articles

Device Verification Testing of High-Speed Analog-to-Digital Converters in Satellite Communication Systems

This paper presents a step-by-step sequence of operations for the dynamic performance testing of a high-speed analog-to-digital converter (ADC) using on-chip digital demultiplexing and clock distribution. Demultiplexed digital outputs are postprocessed and fed into a computer-aided ADC performance characterization tool. The described methodology reduces test costs and overcomes many test hardware limitations. The problems of high-sampling-rate ADC testing are described. As our focus is on RF communication system applications, we emphasize the measurement of intermodulation distortion (IMD) and effective resolution bandwidth (ERB). Accurate gain and phase matching are also of critical importance. As Fourier analysis is an important component of characterization, we address the issue of automated sample window adjustment to eliminate leakage and false spur generation. A 6-bit 800 MSample/s dual-channel SiGe-based ADC is used as a target example.

Monolithic 1-Chip FBAR duplexer for W-CDMA handsets

Film bulk acoustic resonator (FBAR) filters and duplexers are receiving increasing attentions in RF systems due to the advantages of having high power handling capability, high Q-factors, good thermal stability, require a small volume and are relatively cheap. There are currently no published papers and research about FBAR 1-Chip duplexer, which have been designed with Tx and Rx filters because it is a very challenging task. We report for the first time that a monolithic 1-Chip RF duplexer is achieved with the size of 2.5 mm × 2.5 mm using thin FBAR technology to meet the stringent demand for miniaturization and monolithic integration of duplexers in RF communication systems. In this work, a novel 1-Chip duplexer is designed by EM (electromagnetic) simulation and RF circuit simulation using HFSS and ADS. The highest insertion losses in the pass band (1920–1980, 2110–2170 MHz) are measured below 4.35 dB, and attenuation are over 39 dB.

Noise modeling of heterojunction bipolar transistors using neural network approach

AbstractThe advantages of heterojunction bipolar transistors (HBTs) make them very promising for modern RF communication systems and therefore their noise performance becomes an important issue as well. A procedure for HBT noise modeling based on the neural network approach is presented in this paper. The proposed models are characterized by high accuracy and efficiency commonly requested for today's CAD techniques. © 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 852–854, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI.10.1002/mop.22275

Parametric Conversion Using Custom MOS Varactors

The possible role of customized MOS varactors in amplification, mixing, and frequency control of future millimeter wave CMOS RFICs is outlined. First, the parametric conversion concept is revisited and discussed in terms of modern RF communications systems. Second, the modeling, design, and optimization of MOS varactors are reconsidered in the context of their central role in parametric circuits. Third, a balanced varactor structure is proposed for robust oscillator frequency control in the presence of large extrinsic noise expected in tightly integrated wireless communicators. Main points include the proposal of a subharmonic pumping scheme based on the MOS varactor, a nonequilibrium elastance-voltage model, optimal varactor layout suggestions, custom 0.13 µm-CMOS varactor design and measurement, device-level balanced varactor simulations, and parametric circuit evaluation based on measured device characteristics.

Neural network for noise modeling of SiGe HBT's

The advantages of SiGe HBTs make them very promising for modern RF communication systems and therefore their noise performance becomes an important issue as well. This paper presents the noise modeling of SiGe HBTs for broad operating ranges. Two neural network structures are presented and discussed from the aspect of modeling accuracy: a basic one and an extended one obtained by adding the S-parameters to the input.

Effect of Zr-Substitution on the Magnetic Property of a YIG Ferrite

Yttrium Iron Garnet (YIG) has been used as an important material in the Circulator/Isolator which is used in RF communication system, mobile phone, and satellite broadcasting, etc. In this study, we investigated the variation of electromagnetic properties of YIG ferrites for Isolator/Circulator application with Zr addition. The YIG ferrites, Y2.1Ca0.9Fe4.4-xV0.5In0.05Al0.05ZrxO12 with x=0, 0.05, 0.1 and 0.2, were prepared by the conventional ceramic sintering process. The Zr-substituted YIG ferrite, Y2.1Ca0.9Fe4.4-xV0.5In0.05Al0.05ZrxO12, showed the highest saturation magnetization (1097 gauss) at x=0.1. Good microwave properties were shown as isolation of 18.60 dB and insertion loss of 0.45 dB at x=0.2. In addition, the ferromagnetic resonance (FMR) linewidth decreased as Zr content increased

MEMS for RF Applications

Micro-Electro-Mechanical-Systems (MEMS) technology promises revolution in the various application domains in the 21st century. RF communication systems are expected to be benefited through MEMS technology. The desire for the mobile gadgets to do the computing, communication and customer specific functions dictates that these gadgets should encompass a variety of device capabilities. Along with the sensory and actuating functions that MEMS can accomplish, MEMS can do value addition to the RF CMOS device integration to enable mixed signal System On Chip (SOC) solution. This paper specifically addresses the use of MEMS technology to realize the components of RF subsystem. The possible components include, but not limited to, varactors, inductors, switches, resonators and oscillators.

Pb(Zr,Ti)O3-GaN Heterostructures for RF MEMS Applications

Ferroelectric (Pb(Zr0.3Ti0.7)O3 or PZT(30/70))/GaN/Sapphire heterostructures were fabricated by the sol-gel process. The structure and composition of PZT, and its dielectric and ferroelectric properties in Pt/PZT/Ru or Pt/PZT/Pt, and Pt/PZT/GaN configurations were characterized to assess their feasibility as RF MEMS devices for eventual insertion in RF communication systems. The X-ray diffraction and pole figure analysis confirmed the stoichiometric, phase-pure PZT with (111) out-of-plane relationship on (0001) GaN. The secondary ion mass spectrometry (SIMS) depth profile indicated a stable interface with insignificant inter-diffusion of the Pb, Zr, or Ti elements into the GaN. The properties of PZT in Pt/PZT/Ru/GaN or MFM configuration were high capacitance density (C/A = 1.25 μF/cm2) and polarization (30 μC/cm2). In contrast, PZT in Pt/PZT/GaN or MFS configuration exhibited lower capacitance density (C/A = 0.35 μF/cm2) and asymmetrical hysteresis loops (polarization ∼4 μC/cm2). From the calculated spatial distribution of the electric field, E(x), and potential, V(x), which stem from all the charge densities within the entire MFS system, one may eventually design and fabricate PZT/GaN heterostructures in terms of controllable parameters (e.g., PZT phase and orientation, donor and acceptor ionization energies, and thickness and screening lengths of PZT and GaN), such that the depolarization field (Edepol) is minimized and the polarization is maximized in PZT.

A flexible, transceicver-based RF communications system for small satellites

A flexible, transceicver-based RF communications system for small satellites

A novel nonlinear distortion characterisation standard for RF and microwave communication systems

Theoretical results obtained with a simplified third order memoryless nonlinear system have shown that multitone test characteristics can be directly related to the more usual two-tone test figures. These theoretical developments have also proved that the noise power ratio (NPR) gives an optimistic measure of co-channel distortion. A corrected co-channel power ratio (CCPR) characterisation standard and its associated laboratory measurement set-up have therefore been proposed to circumvent the failings of the NPR. The usefulness of this approach is illustrated by some measurements of a practical C-band amplifier circuit.

Floquet theory and non-linear perturbation analysis for oscillators with differential-algebraic equations

Oscillators are key components of electronic systems. In RF communication systems, they are used for frequency translation of information signals and for channel selection, and in digital electronic systems, they are used as a time reference, i.e. a clock signal, in order to synchronize operations. Undesired perturbations in practical electronic systems adversely affect the spectral and timing properties of oscillators, which is a key performance limiting factor, being a major contributor to bit-error-rate (BER) of RF communication systems, and creating synchronization problems in clocked and sampled-data systems. Characterizing how perturbations affect oscillators is therefore crucial for practical applications. The traditional approach to analysing perturbed nonlinear systems (i.e. linearization) is not valid for oscillators. In this paper, we present a theory and efficient numerical methods, for non-linear perturbation and noise analysis of oscillators described by a system of differential-algebraic equations (DAEs). Our techniques can be used in characterizing phase noise and timing jitter due to intrinsic noise in IC devices, and evaluating the effect of substrate and supply noise on the timing properties of practical oscillators. In this paper, we also establish novel results for periodically time-varying systems of linear DAEs, which we rely on in developing the above theory and the numerical methods. Copyright © 2000 John Wiley & Sons, Ltd.

Intersatellite laser crosslinks

Intersatellite laser crosslinks (ISL) provide a method of communication that has significantly increased the data throughput that can be managed over typical RF communication systems, and has significant growth potential. Optical communications offer very wide bandwidths which can be effectively utilized with wavelength division multiplexing techniques. The data rate growth potential is well beyond the few gigabit per second range of RF technology. The use of lasers in transmitting optical data takes advantage of its small wavelength and low beam divergence to send highly directed signals over significant distances with controlled losses in intensity. The high directivity of the laser aids in resistance to jamming communications between satellites, or between satellites and ground stations. Various intersatellite laser optical crosslink system are discussed including the Massachusetts Institute of Technology's Laser Intersatellite Transmission Experiment (LITE), the McDonnell Douglas Electronic Systems Company Laser Crosslink System, and The Ball Aerospace Optical Intersatellite Link,in order to display the various subsystem and their implementations. Link budget calculations are performed on the most commonly used modulation formats to determine system parameters necessary to close the crosslink. Background is provided on primal system architectures and methods of laser communication, as well as presently implemented systems. The authors provide some insights on where ISL systems have opportunity to increase their data throughput and reduce acquisition time.

SHIP EM DESIGN TECHNOLOGY

ABSTRACTThis paper describes the design procedure and engineering design tools used for Navy shipboard exterior RF communication system design. The approach is an iterative process by which candidate RF system designs can be analyzed to determine their relative desirability.Several computer codes have been developed for designing the exterior RF communication systems for Navy ships. The software design aids consist of two packages, one for antenna modeling (such as the NEC‐Method of Moments, NEC‐Basic Scattering, and NEC‐Reflector antenna codes), and another for communication systems analysis (such as DECAL, PECAL, LINCAL, and COSAM II). These codes have been well documented, validated, and applied successfully to design and integrate a number of shipboard exterior communication and topside antenna systems. However, there exist two shortcomings: (1) lack of a user friendly interface, and (2) lack of the ability to enforce design discipline and completeness. The Naval Ocean System Center recognized these shortcomings and has initiated the development of engineering workstations such as the Interactive Graphic Utility Automated for Numerical Electromagnetic Code (NEC) Analysis (IGUANA), the Numerical Electromagnetics Engineering Design System (NEEDS), and the Communication Engineering Design System (COEDS).

Fast tunable active receiving antennas

With mobile RF communication systems, sensitivity and linearity characterized by the dynamic are the main important qualities of the system on the receiving side. Up to now, especially in the low frequency and the short wave frequency range this problem has not been solved satisfactorily with professional passive antenna systems even though heavy filters are used. Considering nonlinear effects and taking the electromagnetic pulse problem (emp) into account, the short selective active receiving antenna is the optimum solution to this problem. A formula is derived for the field strength sensitivity of the selective active rod antenna. Taking the external noise into account, the minimum height of the antenna is evaluated with respect to optimum sensitivity as well as with respect to minimum nonlinear distortion of the amplifier, which means optimum dynamic range. Antenna heights and dynamic range of the selective active antenna are compared to different systems such as active broadband antennas and standard receiving systems with passtive antennas. For sensitivity reasons, capacitive antenna elements must be tuned by inductive means. In combination with a special switching strategy, premagnetized ferrite inductances are appropriate tuning elements. Nonlinear effects in the ferrites, however, are one of the main problems with electrically tuned antennas, which therefore are taken into account as well.

Automated Procedure for Shipboard Exterior Communication RF System Design

This paper describes the design procedure used for Navy shipboard exterior RF communication system design. The approach is an iterative process by which candidate RF-system designs can be analyzed to determine their relative desirability. To support the design procedure, an automated capability has been developed consisting of two system modeling codes and three antenna modeling codes. This automated design procedure also has been applied to nonshipboard cosite communication systems.