Cardiff University | Prifysgol Caerdydd ORCA
Online Research @ Cardiff 
WelshClear Cookie - decide language by browser settings

An enhanced modulated waveform measurement system

Akmal, Muhammad 2011. An enhanced modulated waveform measurement system. PhD Thesis, Cardiff University.
Item availability restricted.

PDF - Accepted Post-Print Version
Download (39MB) | Preview
[img] PDF - Supplemental Material
Restricted to Repository staff only

Download (79kB)


The microwave devices and circuits need to be characterized prior to being employed in the design of systems and components. Unfortunately the measurement systems required to characterize the microwave devices and circuits have not kept pace with the emerging telecommunication technologies demands. This has resulted into a situation where either the circuits being employed in the components are unoptimized or the yield and turn-around of optimized circuits are slow. One of the contributing factors of such situations is the limitations of the existing measurement systems to scale up in performance to fulfil the necessary requirements. This thesis presents an enhanced multi-tone, time domain waveform measurement and engineering system. The presented system allows for a more considered, and scientific process to be adopted in the characterisation and measurement of microwave power devices for modern day communications systems. The main contributions to the field of research come in two areas; firstly developments that allow for accurate time domain measurement of complex modulated signals using commercially available equipment; and secondly in the area of active impedance control, where significant developments were made allowing active control of impedance across a modulated bandwidth. The first research area addressed is the fundamental difficulty in sampling multi-tone waveforms, where the main achievements have been the realisation of a high quality trigger clock for the sampling oscilloscope and a “Time Domain Partitioning” approach to measure and average multi-tone waveforms on-board. This approach allows the efficient collection of high quality vectoral information for all significant distortion terms, for all bands of interest. The second area of research investigated suitable impedance control architectures to comprehensively investigate out-of-band impedance effects on the linearity performance of a device. The ultimate aim was to simultaneously present independent, baseband impedances to all the significant baseband (IF) frequency components and to 2nd harmonic that result from a multi-tone excitation. The main achievement in this area was the ability of the enhanced measurement system to present the broadband impedance. At baseband this has been achieved in the time domain using a single arbitrary waveform generator (AWG) to synthesise the necessary waveforms to allow a specific IF impedance environment to be maintained across a wide IF bandwidth. To engineer the RF out-of-band load terminations at RF frequencies and to emulate specific power amplifier modes, a Tektronix AWG7000 Arbitrary Waveform Generator was used to deliver the desired impedances, practically fulfilling the wideband application requirements for reliable device characterisation under complex modulated excitations.

Item Type: Thesis (PhD)
Status: Unpublished
Schools: Engineering
Subjects: T Technology > TK Electrical engineering. Electronics Nuclear engineering
Uncontrolled Keywords: Active load-pull; Baseband; Envelope domain; Hysteresis; Intermodulation; Linearization; Memory effects; Power device
Date of First Compliant Deposit: 30 March 2016
Last Modified: 19 Mar 2016 22:26

Citation Data

Cited 4 times in Google Scholar. View in Google Scholar

Actions (repository staff only)

Edit Item Edit Item


Downloads per month over past year

View more statistics