Nonlinear Microwave Systems Research Articles

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.

System-Oriented Harmonic-Balance Algorithms for Circuit-Level Simulation

This paper discusses a self-consistent set of modern computational concepts providing an effective approach to the circuit-level harmonic-balance (HB) simulation of nonlinear microwave systems of complex topology. The system is automatically split into the interconnection of a near-optimal number of nonlinear blocks at run time. The resulting structure is then exploited by the domain-partitioning concept. A block-wise constant spectrum is used rather than a common spectrum by considering for each block only the set of spectral lines that are relevant to its electrical function, which leads to a very significant reduction in the number of problem unknowns. System simulation under digitally modulated RF drive is reduced to a sequence of modified multitone HB analyses that are backward coupled through the envelope dynamics. Besides providing high numerical efficiency, this set of techniques opens the way to an effective co-simulation of RF and baseband transceiver sections.

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.

Why are Nonlinear Microwave Systems Measurements so Involved?

Performing nonlinear measurements on microwave devices is a complex task. This paper introduces, step by step, the key concepts that make the difference between linear S-parameter measurements and nonlinear measurements. The main goal here is to make nonlinear measurements more accessible to the practicing microwave engineer.

A Nevv Method of Third-Order Intermodulation Reduction in Nonlinear Microwave Systems

Third-order intermodulation distortion (IMD (3)) of some microwave systems has been analyzed using Vollterra series. In this paper, theoretical results which have been calculated with a nonlinear FET model show that third-order intermodulation prodgcts of two input signals at f/sub 1/ and f/sub 2/ can be reduced by several orders of magnitude (in fact, theoretically, IMD (3) should be reduced to zero), with a low-frequency feedback at f/sub 1/- f/sub 2/, when the amplitude and the phase of this feedback are correctly chosen. To verify this prediction, a circuit has been realized and measurements have been made on a one-stage FET amplifier. First results confirm our analysis. Experimental measurements show a 12-dB decrease of intermodulation products with our method.