Noureddine Boulejfen

Frequency- and time-domain analyses of nonuniform lossy coupled transmission lines with linear and nonlinear terminations

A new technique for the frequency- and time-domain characterization of nonuniform coupled transmission lines is presented in this paper. In the frequency domain, a method-of-moments-based approach is used to compute the 2N/spl times/2N scattering parameter matrix of the N-coupled lines using special frequency-dependent basis functions that give good accuracy over very large bandwidths. In the time domain, the structures S-parameters are used as its Greens function and are combined with source and terminating load conditions to obtain its transient response. The proposed method can account for loss and is particularly suitable for wideband microwave component designs and ultrahigh-speed/large-bandwidth digital interconnects, including nonlinear terminating loads. A detailed formulation of both the frequency- and time-domain approaches is presented. Several examples of two- and three-line structures are analyzed and the results are compared to published results and other computer-aided-design simulations.

An automated N-port network analyzer for linear and non linear multi-port RF and digital circuits

A new automated N-port time and frequency domain network analyzer based on the microwave transition analyzer MTA, used as a high speed digital oscilloscope, has been developed. The validity of the developed system is demonstrated with number of experimental measurements on different multi-ports structures.

A frequency/time domain characterization technique for frequency-translating devices

A novel approach and a new measurement setup for the characterization of frequency translating devices (FTD) are proposed. The proposed approach allows for an automated, one-step full characterization of FTDs by measuring both the magnitudes and phases of the incident and reflected waves at all signal ports. The application of the proposed approach and the developed measurement setup to the characterization of a double balanced mixer is presented.

Small-signal, complex distortion and waveform measurement system for multiport microwave devices

This paper presented a general-purpose multiport measurement system and calibration algorithm for the characterizations of N-port microwave devices. The system is built around the micro wave transition analyzer as a multi-harmonic receiver from DC to 40 GHz, which provides the system with the scope capability for time domain measurements and the vector network analyzer capabilities for frequency-domain measurements. The developed system has the capability of measuring the S-parameters of linear microwave circuits as well as the AM-AM and AM-PM conversions for nonlinear microwave devices in single-step measurements, without any need for reconnection or change in the calibration technique or meas urement setup. The system can accurately quantify the impact of crosstalk on the performance of the multiport nonlinear microwave systems in terms of power efficiency and signal distortion. The proposed calibration algorithm for waveform measurements utilizes a standard signal frequency generator and does not rely on the use of a multi-harmonic generator to calculate the error box parameters at the fundamental and harmonic frequencies. The algorithm is also applicable to any multi-harmonic phase-locked receiver based measurement system. Finally, it has been demonstrated that the measurement system is capable of performing waveform engineering measurements. The comparison of waveforms obtained in 50 Ω and non-50 Ω impedance environments using the developed system and standard commercial scopes shows good agreement. This enhances confidence in the measurement data obtained from the developed measurement system.

A Multiport Measurement System for Complex Distortion Measurements of Nonlinear Microwave Systems

An effective multiport measurement system for the characterization of N-port nonlinear microwave devices is proposed. The proposed measurement system has the capability of measuring the S-parameters of linear microwave circuits and the amplitude-modulation-to-amplitude-modulation (AM/AM) and amplitude-modulation-to-phase-modulation (AM/PM) conversions for fundamental and harmonic frequencies for nonlinear microwave devices on single-step measurement without any need for reconnection or change in the calibration technique or measurement setup. It is found suitable that the proposed system can accurately quantify the impact of crosstalk on the performance of multibranch amplifiers and multiport nonlinear microwave systems in terms of power efficiency and signal distortion.

Performance assessment of RF power amplifier memory polynomial models under different signal statistics

Memory polynomial models are widely used in the behavioural modelling and linearization of RF power amplifiers (PAs). In this paper we assess the performances of theses models under different signal bandwidths, statistics and power distributions. For this purpose, Normalized mean square error (NMSE) has been used to compare the model output to measured data when the PA is driven by different input signals. Several simulations and measurements have been carried out and the results demonstrated the effects of the signal characteristics on the performances of the model. Real multi carrier WCDMA and multi tone signals were used with an experimental Doherty amplifier. The obtained results revealed a degradation of the polynomial model performances when the statistics of the input signals change.

A robust and efficient method for the frequency domain analysis of non-uniform, lossy multi-line transmission structures

A new efficient and robust method of moment-based formulation for the analysis of non-uniform, lossy multi-line transmission structures is proposed. The stability and speed of this method are demonstrated by analyzing different non-uniform structures. The performances obtained show the proposed approach to be suitable for CAD applications.

A homodyne multi-port network analyzer for S parameter measurements of microwave N-port circuits/systems

In this paper a homodyne multi-port network analyzer using a single six-port junction as a wave correlator is proposed for the characterization of N-port microwave devices, circuits and systems. The six-port wave correlator is operated as a two-channel wave receiver. The use of an additional test set, which comprises two switching matrices and N directional couplers, allows the measurements of complete S parameter matrices of N-port devices. By comparison to existing network analyzers, the proposed system is homodyne in the sense that it does not require any frequency down conversion to determine the phase information and uses only one six-port junction to obtain complex S parameter measurements from only scalar measurements.

Compensation of I/Q impairments and nonlinear distortion in MIMO wireless transmitters

In this paper, a joint predistorter based on the multi-variable memory polynomial (MP) model is proposed to compensate for the modulator in-phase/quadrature (I/Q) imbalance, the power amplifier (PA) nonlinearity and the crosstalk induced by the interference between the different paths in MIMO radio systems simultaneously. The proposed algorithm was experimentally validated and compared to the crossover predistorter and its performance was evaluated for 2×2 MIMO transmitter with -30 dB nonlinear crosstalk and for unbalanced modulator. The proposed predistorter shows an improvement around 25 dBc over the uncompensated output.

A novel measurement technique for microwave frequency translating devices (FTD)

A new measurement setup for the characterization of frequency translating devices (FTD) is presented. The proposed approach allows one-step full characterization of FTDs by measuring both the magnitudes and phases of the incident and reflected waves at all signal ports. The application of the proposed approach to the characterization of a double balanced mixer is presented.