Angle estimator for signals with known waveforms

A large-sample decoupled maximum likelihood angle estimator for signals with known waveforms is presented based on exploiting the a priori knowledge that the observation noise can be modelled as spatially white. It is shown that the incorporation of this knowledge significantly improves the angle estimation accuracy over existing angle estimators for signals with known waveforms     

Decomposition of M-ary CPM signals into PAM waveforms

It is widely known that minimum shift keying (MSK) may be seen as a PAM signaling scheme and that the same is true, albeit approximately, with MSK-like modulations. It is also known (perhaps not so widely) that any binary continuous phase-modulated (CPM) signal may be exactly decomposed into the sum of a few PAM waveforms. In this paper we show that this property extends to multilevel CPM signaling. Features of a PAM decomposition are discussed as a function of the alphabet size, the modulation index, and the frequency response of the system. It is found that, especially with signaling schemes with a long memory, the decomposition has so many terms that it becomes unmanageable. For these cases an approximation is proposed with a limited number of terms     

Bounds for truncation error in sampling expansions of band-limited signals

Forf(t)a real-valued signal band-limited to- pi r leq omega leq pi r (0 < r < 1)and represented by its Fourier integral, upper bounds are established for the magnitude of the truncation error whenf(t)is approximated at a generic timetby an appropriate selection ofN_{1} + N_{2} + 1terms from its Shannon sampling series expansion, the latter expansion being associated with the full band[-pi, pi]and thus involving samples offtaken at the integer points. Results are presented for two cases: 1) the Fourier transformF(omega)is such that|F(omega)|^{2}is integrable on[-pi, pi r](finite energy case), and 2)|F(omega)|is integrable on[-pi r, pi r]. In case 1) it is shown that the truncation error magnitude is bounded above byg(r, t) cdot sqrt{E} cdot left( frac{1}{N_{1}} + frac{1}{N_{2}} right)whereEdenotes the signal energy andgis independent ofN_{1}, N_{2}and the particular band-limited signal being approximated. Correspondingly, in case 2) the error is bounded above byh(r, t) cdot M cdot left( frac{1}{N_{1}} + frac{1}{N_{2}} right)whereMis the maximum signal amplitude andhis independent ofN_{1}, N_{2}and the signal. These estimates possess the same asymptotic behavior as those exhibited earlier by Yao and Thomas [2], but are derived here using only real variable methods in conjunction with the signal representation. In case 1), the estimate obtained represents a sharpening of the Yao-Thomas bound for values ofrdose to unity.     

Wideband compact antenna for K-band applications

A compact coupled microwave active antenna is presented. This antenna is proximity fed, and consists of a square radiating element array on a polymer dielectric layer. The compactness of the antenna is obtained through technological optical processes and the parasitic patch phenomenon which increases the bandwidth     

Study of compact antenna for UWB applications

A novel miniature antenna design for ultra-wideband (UWB) applications is presented. The proposed compact antenna is achieved by exploiting a quasi-self-complementary structure along with a tapered radiating slot. The optimal design of this type of antenna can offer an ultra-wide 10 dB impedance bandwidth with reasonable radiation properties. It also exhibits very small dimensions, 19 x 16 mm in physical size, and 0.19 l in electrical size. Good agreement is obtained between simulated and measured antenna characteristics.     

Serrodyne frequency translation of continuous optical signals using ultrawide-band electrical sawtooth waveforms

Serrodyne frequency translation of continuous optical signals by /spl plusmn/1.28 GHz is reported, significantly exceeding the highest previously published serrodyne shifts. To achieve these shifts, an ultrawide-band high-power electrical sawtooth created by spectral modulation of dispersed optical pulses was used. Its amplification involved a novel predistortion technique to compensate for the gain and phase ripple in the amplifier bandwidth.     

Design concept of compact antenna for SDARS applications

A design concept to reduce the overall dimensions of a microstrip antenna using a wrapped radiating structure and embedded slits is proposed. A compact microstrip antenna for SDARS (satellite digital audio radio services) systems is designed and manufactured with light weight and compact size. Comparison between simulations by Ansoft HFSS software and measurement is provided.     

Sampling of compact signals in offset linear canonical transform domains

The offset linear canonical transform (OLCT) is the name of a parameterized continuum of transforms which include, as particular cases, the most widely used linear transforms in engineering such as the Fourier transform (FT), fractional Fourier transform (FRFT), Fresnel transform (FRST), frequency modulation, time shifting, time scaling, chirping and others. Therefore the OLCT provides a unified framework for studying the behavior of many practical transforms and system responses. In this paper the sampling theorem for OLCT is considered. The sampling theorem for OLCT signals presented here serves as a unification and generalization of previously developed sampling theorems.     

A compact Cramer-Rao bound expression for parametric estimation ofsuperimposed signals

The problem of parameter estimation of superimposed signals in white Gaussian noise is considered. Closed-form expressions of the Cramer-Rao bound for real or complex signals with vector parameters are derived, extending recent results by P. Stoica and A. Nehorai (1989)     

CPW-fed compact monopole antenna for dual-band WLAN applications

A compact CPW-fed monopole antenna is proposed for dual-band wireless local area network (WLAN) operations. The proposed antenna, which consists of two strips, has compact size of 20/spl times/15.5/spl times/1.6 mm/sup 3/ including the ground. The proposed antenna effectively covers both 2.4 GHz (2.4-2.484 GHz) and 5 GHz (5.15-5.825 GHz) bands. The measured peak gains are 1.3 dBi at 2.44 GHz and 2.8 dBi at 5.32 GHz.     

A linear compact tunable transconductor for Gm-C applications

A CMOS highly linear voltage-controlled transconductor suitable for Gm-C filter design is presented. The control loop to program the transconductance maintains the input transistors in triode region with a compact topology. Measurement results for the transconductor fabricated in a 0.5-??m CMOS technology feature a spurious-free dynamic range (SFDR) of 72?dB for 1 V_pp differential inputs at 1?MHz. The voltage to current converter ensures a high linearity level for a wide transconductance range. Functionality of the transconductor is shown in a fifth-order Gm-C tunable complex filter well suited for a dual-mode Bluetooth/Zigbee transceiver.     

An open-source software tool for compact modeling applications

This column features an open-source software tool - called automatic device model synthesizer (ADMS) - that supports and simplifies compact model development, implementation, distribution, maintenance, and sharing. The intended audience is people in universities or CAD companies interested in contributing to the development and improvement of the tool. It should also help people whose main interest is using the tool to get a better understanding of how ADMS works internally. ADMS is available on SourceForge.net, one of the most popular open-source software development Web sites. It was developed at Motorola Inc., whose main interest is to support standardization of compact models.     

Wigner-Ville analysis of asymptotic signals and applications

The Wigner-Ville joint representation (WVJR) appears as a quite good candidate among the various time and frequency JR. This JR performs exact demodulation of finite energy signals even in presence of linear filtering. Signal or waveform synthesis may be derived from this JR or from ambiguity function. Asymptotic signals are depicted in such a way that modulation parameters may be estimated. Dealing with vibroseismic signals the WVJR allows to identify damping parameters related to propagation effects. Propagation models may be checked by this technique. An example of such a technique is provided by processing of synthetic seismic data.     

CAS-CAS transform for 2-D signals: A few applications

A few applications of a separable Hartley-like (CAS-CAS) transform in two-dimensional (2-D) signal processing is presented. The applications discussed include (i) the interpolation of signals, (ii) the computation of Hilbert transform, and (iii) the complex cepstrum computation. The computational advantage of the proposed methods over the algorithms using 2-D FFT are discussed.     

Development of compact half-Sierpinski fractal antenna for RFID applications

A compact half-Sierpinski fractal antenna is presented for UHF RFID applications. Taking the thickness of the substrate (177 mum) and compactness (length: width <2 :1) as constraints, the fractal antenna was studied for the highest exhibited gain. A gain close to 0 dBi (-0.64 dBi) with a return loss of less than -10 dB at 915 MHz was observed.     

Quality-of-service support for multimedia applications

A major project at Lancaster University is the development of network infrastructures capable of supporting the quality-of-service (QoS) requirements of a wide range of distributed multimedia applications. The project includes more than thirty researchers and covers not only the network support but also the enabling technologies. The authors believe that QoS development cannot be done in isolation from the applications to be supported, which must form an integral part of the project. They focus on three application areas: interactive teaching and learning, mobile systems, and virtual reality. They chose applications that stretch network support to its limit. To realize the full potential of these distributed multimedia applications, the underlying network must satisfy all these requirements concurrently. They give a brief overview of their activities to this end and discuss the need for QoS support