8 research outputs found
High-efficiency and broadband PA design considering the impact of device knee voltage
No full textThe new 5G communications system requires the power amplifier (PA) circuits to be operated with high efficiency at both peak and back-off power within a broad RF and video bandwidth. The new 5G signal has an increased complexity for the modulation scheme, resulting into a high signal peak-to-average ratio (PAPR). In consequence, the performances of the PA are limited. This thesis addresses the design analysis for high efficiency and broadband PAs based on harmonic tuned continuous class-F (CCF) mode by including the I-V knee interaction. Most PA modes and waveform engineering techniques to elevate PA performances are ignoring the practical knee voltage. This thesis addresses the new performances of the CCF mode when the I-V knee interaction from the waveforms in considered. The current waveforms are a function of voltage waveforms, that clipped and generates harmonics when voltage waveform is expanded into knee region, as the device is operated with compression. The new performances of the CCF mode does not follow the ideal theoretical performances, instead, changes along the phase of 2nd harmonic impedance termination.
The interaction of the current and voltage (I-V) knee on the waveforms of CCF mode allowing load-pull emulation to be calculated, where the α in CCF mode is the function of 2nd harmonic impedances termination in the actual device’s load-pull technique. In this research, the load-pull emulation is performed only through mathematical calculation in MATLAB by manipulating the equation of drain current and voltage waveforms. Output power and efficiency contours are generated from load-pull emulation for CCF mode, that have almost identical behaviour with the actual device model and measurement, when the non-linear I-V knee interaction is considered. This emulation also investigates the efficiency of the device at the output power back-off (OPBO) range, with the sweep of the α parameter. The investigation of the new CCF mode with I-V knee interaction is used as guide for a PA design with restriction of the phase of 2nd harmonic impedances termination to keep the efficiency high across wide bandwidth.
The video-bandwidth (VBW) performances for the PA can be extended using a baseband termination circuit at the device’s output to shift the resonance frequency coming from the bias network and the device’s output parasitic capacitance. The VBW enhancement is crucial in the 5G communication system where it is expected to operate up to 800 MHz, or even beyond this frequency, for the instantaneous bandwidth. Analyses are made on the components used in the baseband termination circuit in this thesis, where the VBW can be further extended by having the highest value of the shunt capacitor that is placed close to the device, with the lowest equivalent series inductance. This configuration shifted the resonance frequency and reduced the impedances seen by the device output on the matching and bias network. All the methods described in this thesis are adapted to design and investigate the performances of compact PA with integrated matching and baseband termination network. This PA is aimed to operate with high efficiency at the 50 Ω load impedances and at load modulated output power back-off across a wide-bandwidth. A CW simulation tests are used to evaluate the performances of the PA at peak power, while 2 tones signal with sweep frequency spacing is used to evaluate the VBW performances
On the effective modeling of the test-set non-linearity
No full textThis paper investigates and compares the use of nonlinear test-set models for an effective and accurate operation of active load-pull systems. The results demonstrate a simple-to-implement and yet robust technique to align the generator and receiver reference plane with a minimum set of required measurements. With only 14 measurements a high agreement between target and measured load points was achieved with an average error less than 0.1 dB over a 70dB dynamic range. An increase in modeling complexity has therefore yielded no improvement. To compare the results, a behavioral model was employed, and it is shown that a high order of model complexity is required to achieve the same level of accuracy. The presented work provides, for the first time, a practical and effective method for the modeling of test-set nonlinearities, hence allowing a cost-effective implementation of active load-pull systems that operate power amplifiers within a gain compression region
High-efficiency broadband PA design based on continuous Class-F mode with compression
No full textThe paper presents a novel reformulation of the Continuous Class-F (CCF) mode by including an I-V knee scaling equation in the drain current waveform. The device's knee region scales down the waveform and distorts the ideal flat performances especially when the device is in compression. The output power and drain efficiency are no longer constant across α variation in the CCF mode. Instead, symmetrical performances across α space are simulated and measured showing drain efficiency is at peak when α is at its extreme: +1 or -1. 10W GaN HEMT broadband PA (1.7 GHz to 2.7 GHz) is designed by restricting phase rotation of 2 nd harmonic impedances within α=-1 ranges across bandwidth. The manufactured PA achieved 11.3W-18.4W Pout and 65.7%-83.4% DE. When operated with 10MHz LTE signal with 7.6dB PAPR at 2.7 GHz, the PA achieved ACPR levels of -53.6/-54.6 dBc after DPD
A novel modulated rapid load pull system with digital pre-distortion capabilities
No full textThis paper investigates the concurrent operation of a commercially available, modulated impedance synthesis and measurement system with digital pre-distortion (DPD) for industry standard modulated signals. The system was used to characterize a 10W GaN HEMT device, and provide impedance control over signal and distortion bandwidths, in response to a 10 MHz LTE signal centred at 2 GHz, and was able to rapidly achieve target reflection coefficients with an error less than −40dB (1%). A National Instruments (NI) PXi based characterisation system was used to apply a commercially available memory-based DPD algorithm. The transistor was biased in class-AB and was successfully linearised to better than −47.95 dBc ACPR when delivering at 2.5W average output power into an optimum load. Interestingly, the analysis showed that the DPD corrected ACPR contours aligned closely with the P 1dB contours, confirming the relevance of targeting peak-power for DPD, rather than raw ACPR. Also, and importantly, a level of linearity performance was achieved that meets for example, the 3GPP linearity specifications (45dBc) for commercial deployment, and demonstrates how this modulated load-pull system and DPD can be combined to de-risk an amplifier design at a very early stage in the design process
What Makes a Good Health Related Research Data Repository? Findings from a Scoping Review
No full textIntroduction There is a strong need for having a focal point such as a data repository platform to ensure that evidence produced in local context can be collected, managed, protected and disseminated to relevant parties in timely manner. In establishing such platform, understanding the best practices and major characteristics of established data repositories on health-related research data worldwide would be the first crucial step. A scoping review was thus performed with the objective of mapping the characteristics of online-based health-related research data repositories that are being practised globally.
Methodology A three phase processes was performed which include; identifying relevant articles from major online databases, namely Pubmed, CINAHL, Web of Science and Google Scholar; charting the data, and; collating and summarising the data from the articles collected.
Results A total of 46 final articles were identified and analysed. Majority of the articles discussed on platforms which are based in the United States and Canada (n=26), combination of more than one country (n=9), Europe (n=8), Africa (n=2), and Asia (n=1). Three major themes emerged that describe the characteristics of these data repositories, namely; Data deposit and archive; Data retrieval and access; Data policy and governance.
Discussion/Conclusion The scoping review has revealed the major characteristics of established health-related research data repositories that are being practised globally. It is thus imperative to adopt these characteristics in local data repository platforms to enhance the function of these platforms especially for organisations that produce and manage local research products such as the National Institutes of Health (NIH) Malaysia.
[Disclaimer: Abstract text might vary slightly from what is displayed in the e-poster]This poster was submitted to the 14th National Conference for Clinical Research (NCCR) in August 18-20, 2021. https://nccrconference.com.my
Abdominal Obesity and Its Associated Factors Among Malaysian Women, Does Ethnicity Matter?
No full textIntroduction Generally, a cause of death and disability were contributed by an excess of body fat. For health, the issue is not how much you weigh, but how much abdominal fat you have. This study aims to determine the prevalence of abdominal obesity among Malaysian women and its association with sociodemographic and personal life style.
Methodology Data were obtained from the National Health and Morbidity Survey (NHMS) 2019 which was carried out via face-to-face interviews using mobile devices. Abdominal obesity was defined according to WHO/IASO/IOTF, 2000 Waist Circumference cut-off (>= 90cm for Men, >= 80cm for Women). A complex sample analysis was carried out at 95% confidence interval using SPSS version 21.0.
Results The prevalence of abdominal obesity among women was 64.8% (95% CI: 62.62, 66.94). Ethnic Malays with age 60 years and above have the highest rate of abdominal obesity compared to other groups. Higher abdominal obesity was found in rural area, age 40-59 years old, unemployed, B40 income group and inactive physical activity for Sarawakians. Logistic regression analysis found that women at risk of having abdominal obesity in Malaysia were those of older people [aOR: 3.464 (95% CI: 2.460 - 4.879)], Sarawakians [aOR: 3.682 (95% CI: 2.222 - 6.102)] and no formal education [aOR: 1.354 (95% CI: 1.052 - 1.742)].
Discussion NHMS 2019 revealed that abdominal obesity was higher among women compared to male. Therefore, health education programs should provide information about the risk factors for abdominal obesity to all women, and preventive strategies should be implemented accordingly.
[Disclaimer: Abstract text might vary slightly from what is displayed in the e-poster]This poster was submitted to the 14th National Conference for Clinical Research (NCCR) in August 18-20, 2021. https://nccrconference.com.my
