Khaled M. Gharaibeh

Accurate estimation of digital communication system metrics - SNR, EVM and /spl rho/ in a nonlinear amplifier environment

A nonlinear spectral analysis technique that enables digital communication system metrics; SNR, EVM and the waveform quality factor (/spl rho/) to be related to in-band distortion spectrum is presented. System metrics are estimated from the measured output power and in-band distortion power. The estimated metrics are verified by direct measurements of each metric using a vector signal analyzer (VSA) performed on a forward-link IS-95 signal. Estimated system metrics are in excellent agreement with measured values.

In-band distortion of multisines

Multisine signals are shown to be useful for estimating distortion of communication signals. In particular, a generalized approach for the evaluation of effective in-band distortion in a nonlinear amplifier using multisine excitation is presented. The output of the nonlinearity is represented as the sum of uncorrelated components by the transformation of a behavioral model. Simulated and measured results are presented for code-division multiple-access signals

Multi-slice behavioral model of RF systems and devices

System level behavioral modelling is a powerful tool in the RF and microwave designers toolbox; it allows design tradeoffs to be explored early in a project. Typical models, however, have limitations in the frequency range and power levels at which they are applicable, and in many instances they fail to capture memory effects that lead to the asymmetrical intermodulation behavior observed in actual systems. We present a behavioral model with memory that can be extracted from device measurements or simulation results. It uses modular slices to capture the system behavior including asymmetrical intermodulation. The model can be used in system analysis and in harmonic balance or transient circuit simulators.

Modeling distortion in multichannel communication systems

A behavioral modeling technique suited to capturing the response of wide-band multifunctional and multichannel amplifiers is introduced. The technique is based on the three-box approximation of the Volterra model and takes into account the dependence of the amplifier characteristics on frequency. The model is coupled with a new nonlinear statistical analysis, which enables accurate estimation of intermodulation and cross-modulation distortions of multiple digitally modulated signals. The model parameters can be obtained using simple measurements.

Accurate multisine representation of digital communication signals for characterization of nonlinear circuits

A technique for generating an accurate multisine representation of a digitally modulated signal using discrete fast Fourier (DFT) coefficients is presented in this paper. A reverse link IS-95 signal containing 200 symbols is modeled by a 240 tone multisine signal where the amplitude and phase of each tone is defined by the truncated Fourier coefficients of the original signal. Adjacent-channel power ratio (ACPR) and error vector magnitude (EVM) measurements of the multisine signal applied to a nonlinear amplifier are in excellent agreement with measurements using the IS-95 reverse link signal. This work demonstrates the accurate use of multisine signals obtained from Fourier coefficients to represent time-domain signals for analysis and measurement of nonlinear circuits.

The impact of nonlinear amplification on the performance of CDMA systems

An analytical formulation, separating the correlated and uncorrelated distortion spectrum when a wireless communication signal is processed by a nonlinear amplifier, is presented. The correlated distortion spectrum relates directly to gain compression or expansion while the uncorrelated distortion spectrum contributes to degradation of the signal-to-noise ratio (SNR). The uncorrelated distortion spectrum is used to calculate the bit error rate (BER) when a nonlinear amplifier is followed by an AWGN channel. BER performance, predicted from the uncorrelated distortion spectrum, is in excellent agreement with simulated BER.

Estimation of in-band distortion in digital communication system

A generalized approach for estimating in-band distortion spectrum when a wireless communication signal is processed by a nonlinear amplifier is presented. The output spectrum is represented as the sum of uncorrelated components using Gram-Schmidt orthogonalization without any restriction on the statistical properties of the input signals. The analysis allows the accurate estimation of in-band distortion and hence the effective SNR, Rho and EVM of wireless communication systems. The approach is verified by measurements of in-band distortion using feed-forward cancellation.

Characterization of cross modulation in multichannel amplifiers using a statistically based behavioral modeling technique

A statistically based modeling technique is developed for characterizing in-band and out-of-band intermodulation and cross-modulation distortions in multichannel amplifier environments. The model is based on a new multiple envelope memoryless behavioral model that captures the black-box characteristics of multichannel amplifiers. A power amplifier with a two code-division multiple-access channel signal is characterized experimentally and verifies the approach.

Target classification in Wireless Sensor Network using Particle Swarm Optimization (PSO)

Target classification is one of the main requirements of target tracking processes in military Wireless Sensor Networks (WSN). In this paper, a new sub-optimal target classification approach based on Particle Swarm Optimization (PSO) is proposed. The PSO classification algorithm is shown to have better classification accuracy and processing speed as compared to the k-Nearest Neighbor (kNN) and Maximum Likelihood classification algorithms.

Statistical modeling of the interaction of multiple signals in nonlinear RF systems

A nonlinear statistical analysis for modeling distortion, cross modulation, and jammer susceptibility of CDMA signals in a nonlinear RF system is presented. The development of the statistical technique is presented here and applied to various interference scenarios. It is shown that relatively higher nonlinearities must be included in the RF system model so that nonlinear distortion is adequately captured.