G. Neveux

Time-Domain Calibrated Measurements of Wideband Multisines Using a Large-Signal Network Analyzer

This paper presents a calibrated measurement technique that enables phase and magnitude measurements of wideband multisines. This study is based on the use of a large-signal network analyzer (LSNA) performing harmonic sub-sampling and a fine frequency grid (20 MHz) comb generator calibrated using a high-frequency 50-GHz equivalent-time sampling scope. This comb generator is used as a harmonic phase reference generator for the calibration of the LSNA. The research reported here is applied to L-band multisine measurements, but it can be extended to higher microwave frequencies. The motivation of this study is to measure the multipactor phenomena effect in output RF multiplexers of satellite payloads.

Accurate phase measurements of broadband Multitone signals using a specific configuration of a Large Signal Network Analyzer

Accurate measurements of time domain waveforms at microwave frequencies are performed using the harmonic sampling principle. This principle used in the large signal network analyzer (LSNA) enables to transform a measured RF spectrum into an IF spectrum which is then digitized by ADCs. Unfortunately in this principle IF spectrum bandwidth is limited to 10MHz due to the need of high dynamic range ADCs (14bits). In this paper, we propose a new method that enables to accurately measure the phase relationships and the amplitudes of the spectral components of broadband microwave signals. Measurements of a 62MHz bandwidth multitone signal at L band have been performed and are shown. The extension of the proposed method to wider bandwidth is absolutely possible. Furthermore the application of the proposed technique to other harmonic samplers than those used in the LSNA is also possible

Wideband, high-efficiency, high-power GaN amplifiers, using MIC and quasi-MMIC technologies, in the 1–4 GHz range

In this paper, the design and experimental results of a MIC Wideband (1-3GHz) and a balanced Quasi-MMIC wideband (2-4GHz), High Power GaN HEMT Power Amplifier (PA) are presented. The two designs, which use the same GaN process, are based on a theoretical study of the limitations in terms of trade-off between bandwidth and efficiency, derived from the Bode-Fano integrals, and applied to actual circuits. The MIC wideband PA, externally matched, generates an output CW power (Pout) greater than 40W, a Power Gain (G) higher than 9.5dB and a corresponding Power Added Efficiency (PAE) (Drain efficiency (DE)) ranged between 36-44% (40-48%) over the 1-3GHz bandwidth. A second amplifier, based on the same methodology, has been designed with a passive GaAs MMIC circuit technology. This fully and internally matched integrated amplifier size is lower than 420 mm2. The power performances of this quasi-MMIC balanced PA are the following in the 2-4 GHz bandwidth: Pulsed CW Pout higher than 45W (50W between 2.1-4 GHz), G higher than 9.8dB and PAE (DE) ranged between 33-44% (38-50%). These results are ones of the best results published in terms of PAE performances and bandwidth trade-offs.

Time-domain measurement system using Track & Hold Amplifier applied to pulsed RF characterization of high power GaN devices

We propose in this paper a time-domain test bench for the pulsed characterization of a high Power GaN Amplifier. Our findings are based on a Track and Hold Amplifier for the down-conversion of RF spectra using the sub harmonic sampling principle. The use of wideband THA to replace samplers or mixers enables reducing component density in an analog domain. It permits direct digitization of entire pulsed RF spectrum, bringing more flexibility in the receivers performance by enhancing the dynamics and bandwidth. This test bench is capable of completely extracting the phase, amplitude and pulse profile of the RF signal. Power characteristics, phase and amplitude information for multiple bursts of pulses of a 50 W GaN HEMT Nitronex (NPTB00050B) power amplifier have been measured using the proposed calibrated measurement system. The low frequency memory effects (thermal and trapping) of high power GaN amplifier were also measured.

High resolution wideband calibration procedure for RF time-domain measurement of non-linear devices

This paper proposes a high resolution wideband calibration procedure for RF time-domain measurement of nonlinear devices. This calibration is based on the use of wideband multi-sine signal and is applied to a 4 channel Track and Hold Amplifier (THA) based measurement setup. The absolute magnitude and phase calibration is performed with a calibrated coherent interleaving sampling oscilloscope as reference. The new calibration procedure without any IF calibration assumption allows a 10 kHz resolution over 3 GHz bandwidth. A 40 W GaN high power amplifier, driven by a pulsed RF signal at the input, is characterized with this time-domain measurement setup. The fully calibrated measurement setup has the capability to give an accurate visualization of time-domain distortions on input/output voltage and current waveforms within the pulse. Calibrated rising and falling transitions of the pulse are also exhibited.

Measured and Simulated Impact of Irregular Radar Pulse Trains on the Pulse-to-Pulse Stability of Microwave Power Amplifiers

This paper investigates the impact of irregular pulsed RF signals on the pulse-to-pulse (P2P) stability of a microwave power GaN HEMT amplifier. This study is based on both the time-domain envelope measurements and nonlinear circuit envelope simulations of P2P stabilities. Measurements and simulations are performed with an irregular pulse train that integrates a long silence (i.e., off-time) between each periodic burst of RF pulses because of its influence on temperature and trap behaviors of GaN HEMTs. The first aim is to experimentally characterize the impact of silence durations and output mismatching on the amplitude and phase P2P stabilities of a 10-W S-band GaN HEMT amplifier. The second objective is to assess the ability of nonlinear HEMT models to fit the time-domain measurements of pulse-to-pulse stabilities. This final part of the paper is focused on the relative impact of electrothermal and drain-lag models on the nonlinear circuit envelope simulations of pulse-to-pulse stabilities. It is demonstrated that both the thermal and trapping effects have to be considered to fit the complex behavior of measured pulse-to-pulse stabilities for microwave GaN HEMT power amplifiers.

A measurement set-up and methodology combining dynamic biasing and baseband predistorsion for high efficiency and linear amplifier design

This paper presents a time domain envelope measurement system that enables the study and the optimization of high efficiency and linear power amplifiers by applying both envelope tracking and digital base band predistorsion techniques. A man focus of this paper is the description of the set up architecture along with its capability to achieve in depth investigations on the dynamic behavior of envelope tracking amplifiers (ET PAs). To reach optimal efficiency and linearity performances ET PAs need to be accurately characterized under dynamic operating conditions in order to perform a well suited control of RF input envelope and Was voltage tracking signals. The proposed set up is applied here to a 10 W GaN Power amplifier from Cree at 3.6 GHz

Broadband Time-Domain Measurement System for the Characterization of Nonlinear Microwave Devices With Memory

This paper describes a novel fully calibrated four channel broadband time-domain measurement system for the characterization of nonlinear microwave devices with memory. The hardware architecture of the proposed time-domain measurement system is based on a wideband sub-sampling principle. The sampling heads work at a high strobe signal repetition frequency that can be tuned between 357-536 MHz. We achieve a 40-GHz RF frequency bandwidth and a 160-MHz IF bandwidth. This instrument enables the measurement of carrier and envelope waveforms at both ports of nonlinear microwave devices driven by broadband modulated multicarriers. The test-bench is applied to the cross modulation characterization of a 15-W GaN HEMT CREE S-band power amplifier with memory due to different biasing circuit configurations. The amplifier under test is driven by the sum of a large-signal modulated carrier (double-sideband amplitude modulation at 3.6 GHz) and a small single-tone signal at a 110-MHz offset frequency. Our significant contribution comes from the capability of the measurement system to record the time-domain waveforms of several nonadjacent modulated signals on a similar time equivalent scale for different cases of memory effects of the power amplifier under test.

Time-domain interleaved high sampling rate system for large signal characterization of non-linear devices

This paper proposes a high sampling rate, 4-channel Track and Hold Amplifier based time-domain measurement setup. It achieves an equivalent high sampling rate using Coherent Time Interleaved Sampling (CTIS) technique to accurately characterize high Power amplifiers driven by repetitive pulsed RF large signal. The acquired samples are the combination of non-sequential sub-sampling technique and the measurement system based on the use of Track and Hold amplifiers to avoid Intermediate Frequency (IF) aliasing and IF filtering. This principle is applied to the large signal pulsed characterization of S-band 50 W GaN amplifier. Fully calibrated acquired time-domain waveforms and power characteristics under varying load conditions are presented. To the authors knowledge the transients at the beginning and end of pulses are measured and exhibited for the first time.

Calibrated oscilloscopic system for RF time-domain characterization of non-linear devices

This paper proposes a fully calibrated four channel high sampling rate oscilloscopic system based on the use of Track and Hold Amplifiers. The system achieves a high equivalent sampling rate (up to 1THz) using coherent interleaved sampling principle. An accurate calibration procedure allows a 10 kHz resolution over a 3 GHz bandwidth is applied. The capabilities of the system are presented and validated by characterizing a bandpass filter and an S-band 50 W GaN high power broadband amplifier under wideband CW pulsed signal excitation. S-parameters and power characteristics measurements are also presented. The fully calibrated system has the capability to give an accurate visualization of time-domain distortions of input/output voltage and current waveforms within the pulse. It also allows the determination of rising and falling transitions times of the pulse.