ABSTRACT This article presented a review of the most common load-pull approaches adopted in the m... more ABSTRACT This article presented a review of the most common load-pull approaches adopted in the measurement and characterization of large-periphery microwave transistor devices. Although the quarterwave transformer technique is simple and very cost-effective, it has serious limitations in terms of scalability, thereby necessitating a separate quarterwave transformer for each device and frequency. Furthermore, due to the limited bandwidth of the quarterwave transformer, its usage in harmonic load-pull applications is severely limited.
ABSTRACT An ultracompact, low-loss, and broad-band corner mirror, based on photonic crystals, is ... more ABSTRACT An ultracompact, low-loss, and broad-band corner mirror, based on photonic crystals, is investigated in this paper. Based on the theoretical analysis of the loss mechanism, the boundary layers of the photonic crystal region are revised to improve the extra losses, and the transmission characteristics are evaluated by using the 3-D finite-difference time-domain method. The device with optimized structure was fabricated on silicon-on- insulator substrate by using electron-beam lithography and inductively coupled plasma etching. The measured extra losses are about 1.1plusmn0.4 dB per corner mirror for transverse-electronic polarization for the scanning wavelength range of 1510-1630 nm. Dimensions of the achieved PC corner mirror are less than 7times7 mum2, which are only about one tenth of conventional waveguide corner mirrors.
This paper presents for the first time an experimental validation of the continuous inverse class... more This paper presents for the first time an experimental validation of the continuous inverse class-F mode with varying the voltage waveforms, also known as inverse class-FJ. Starting from the standard inverse class-F condition and varying fundamental and third harmonic impedances whilst maintaining an open-circuit second harmonic load it will be demonstrated that output power and drain efficiency can be maintained
2020 IEEE BiCMOS and Compound Semiconductor Integrated Circuits and Technology Symposium (BCICTS), 2020
In the design of power amplifiers the ideal methodology would be a CAD based design cycle using a... more In the design of power amplifiers the ideal methodology would be a CAD based design cycle using a physics-based state-function (I-V, Q-V) non-linear model. In practice state-function models are often more measurement-based than physics-based and by design very general, which does limit their accuracy. Behavioral models extracted directly from measured data provide a complementary methodology, that should address the accuracy limitations of state function models. However, their success in achieving this is highly dependent on the user's behavioral model complexity selection and their measurement dataset choice. In this paper, it will be shown that this issue for the Cardiff Model can be resolved via the design of appropriately tailored measurement datasets.
RF I-V waveform measurement and engineering systems are now finally enabling practical waveform e... more RF I-V waveform measurement and engineering systems are now finally enabling practical waveform engineering to be directly undertaken with systems capable of supporting continuous wave stimulus reaching a high level of maturity. On-going research and development activities are presently addressing the multitone requirement. The availability of RF I-V measurement and engineering capability extends the characterization opportunities for both high-frequency/speed transistor
This study reappraises the optimum design parameters for the sequential power amplifier (SPA) whe... more This study reappraises the optimum design parameters for the sequential power amplifier (SPA) when taking relative phase difference into account. By including the phase relationship between the main and peaking amplifiers, a modified efficiency formulation is derived that reveals the impacts of the key design parameters on the SPA efficiency at output power back-off. To optimise a wideband high-efficiency SPA design, a look-up table method is used to predict the required coupling ratio for a wideband directional coupler. To validate the design approach, a 1.5–2.4 GHz SPA is designed and measured, showing drain efficiency higher than 40% at 6 dB back-off across the band. When characterised using a 20 MHz long term evolution (LTE) signal and digital predistortion, the SPA shows good linearity with error vector magnitude <1.3%, and adjacent channel leakage ratio levels better than −45 dBc across the band.
2016 IEEE International Conference on Electronic Information and Communication Technology (ICEICT), 2016
The intrinsic performance of the devices is of great meaning during power amplifiers design. A me... more The intrinsic performance of the devices is of great meaning during power amplifiers design. A method to update de-embedding network at 5.8 GHz for packaged power devices is put forward based on physical modeling idea. The de-embedding network of a packaged GaN HEMT is presented and its errors are analyzed based on waveform engineering. The results may well lead to optimization of the de-embedding network.
2020 International Workshop on Integrated Nonlinear Microwave and Millimetre-Wave Circuits (INMMiC), 2020
The aim of this paper is to improve the linearity of an envelope tracking (ET) power amplifier (P... more The aim of this paper is to improve the linearity of an envelope tracking (ET) power amplifier (PA) using a simple baseband linearisation approach (BLA), which releases the requirement for the ET-customised digital predistortion (DPD) techniques. The proposed BLA is verified through the comparative study on a Gallium Nitride (GaN) PA with ET and a 28V supply voltage. A two-tone signal and a 20MHz modulated signal are used in the measurement, which demonstrates that in contrast to the 28 V case, the ET PA using BLA can simultaneously achieve higher efficiency and better linearity. To investigate the linearity improvement of using BLA, the constellation diagrams, AM/AM and AM/PM characteristics with and without generalized memory polynomial (GMP)-based DPD are measured and analysed.
This Letter presents a novel characterisation system that is able to fully emulate a complete env... more This Letter presents a novel characterisation system that is able to fully emulate a complete envelope tracking power amplifier (ET-PA) environment, with modulated impedance synthesis and dynamic supply voltage generation while using industry-standard modulated signals and digital pre-distortion. The system is used to characterise a 10 W GaN device and provide impedance control over the signal and distortion bandwidths, in response to a 10 MHz long-term evolution signal. A National Instruments PXI-based measurement system is utilised to apply tracking signals to a bespoke supply modulator and successfully improve the average power added efficiency by ~18 percentage points. Three different shaping functions are implemented, and their efficiency and linearity performance evaluated. In addition, digital pre-distortion (DPD) is used to linearise the PA while operating with the three different tracking trajectories. Experimental results demonstrate that when applying shaping functions, a trade-off needs to be made between efficiency and linearity. Even though a constant gain shaping function provides lower efficiency, it achieves good raw linearity performance without DPD, which is a good option if local linearisation is not available. This novel system is a useful tool in the design of ET-PAs, to more completely investigate the performance of the device.
2016 IEEE MTT-S International Wireless Symposium (IWS), 2016
The intrinsic performance of the devices is of great meaning during power amplifiers design. A me... more The intrinsic performance of the devices is of great meaning during power amplifiers design. A method to update de-embedding network at higher frequency for packaged power devices is put forward based on physical modeling idea. The de-embedding network at 5.8 GHz of a packaged GaN HEMT is presented and its practicability is verified through error analysis. This method is prospected to be applied to other packaged microwave devices.
ABSTRACT This article presented a review of the most common load-pull approaches adopted in the m... more ABSTRACT This article presented a review of the most common load-pull approaches adopted in the measurement and characterization of large-periphery microwave transistor devices. Although the quarterwave transformer technique is simple and very cost-effective, it has serious limitations in terms of scalability, thereby necessitating a separate quarterwave transformer for each device and frequency. Furthermore, due to the limited bandwidth of the quarterwave transformer, its usage in harmonic load-pull applications is severely limited.
ABSTRACT An ultracompact, low-loss, and broad-band corner mirror, based on photonic crystals, is ... more ABSTRACT An ultracompact, low-loss, and broad-band corner mirror, based on photonic crystals, is investigated in this paper. Based on the theoretical analysis of the loss mechanism, the boundary layers of the photonic crystal region are revised to improve the extra losses, and the transmission characteristics are evaluated by using the 3-D finite-difference time-domain method. The device with optimized structure was fabricated on silicon-on- insulator substrate by using electron-beam lithography and inductively coupled plasma etching. The measured extra losses are about 1.1plusmn0.4 dB per corner mirror for transverse-electronic polarization for the scanning wavelength range of 1510-1630 nm. Dimensions of the achieved PC corner mirror are less than 7times7 mum2, which are only about one tenth of conventional waveguide corner mirrors.
This paper presents for the first time an experimental validation of the continuous inverse class... more This paper presents for the first time an experimental validation of the continuous inverse class-F mode with varying the voltage waveforms, also known as inverse class-FJ. Starting from the standard inverse class-F condition and varying fundamental and third harmonic impedances whilst maintaining an open-circuit second harmonic load it will be demonstrated that output power and drain efficiency can be maintained
2020 IEEE BiCMOS and Compound Semiconductor Integrated Circuits and Technology Symposium (BCICTS), 2020
In the design of power amplifiers the ideal methodology would be a CAD based design cycle using a... more In the design of power amplifiers the ideal methodology would be a CAD based design cycle using a physics-based state-function (I-V, Q-V) non-linear model. In practice state-function models are often more measurement-based than physics-based and by design very general, which does limit their accuracy. Behavioral models extracted directly from measured data provide a complementary methodology, that should address the accuracy limitations of state function models. However, their success in achieving this is highly dependent on the user's behavioral model complexity selection and their measurement dataset choice. In this paper, it will be shown that this issue for the Cardiff Model can be resolved via the design of appropriately tailored measurement datasets.
RF I-V waveform measurement and engineering systems are now finally enabling practical waveform e... more RF I-V waveform measurement and engineering systems are now finally enabling practical waveform engineering to be directly undertaken with systems capable of supporting continuous wave stimulus reaching a high level of maturity. On-going research and development activities are presently addressing the multitone requirement. The availability of RF I-V measurement and engineering capability extends the characterization opportunities for both high-frequency/speed transistor
This study reappraises the optimum design parameters for the sequential power amplifier (SPA) whe... more This study reappraises the optimum design parameters for the sequential power amplifier (SPA) when taking relative phase difference into account. By including the phase relationship between the main and peaking amplifiers, a modified efficiency formulation is derived that reveals the impacts of the key design parameters on the SPA efficiency at output power back-off. To optimise a wideband high-efficiency SPA design, a look-up table method is used to predict the required coupling ratio for a wideband directional coupler. To validate the design approach, a 1.5–2.4 GHz SPA is designed and measured, showing drain efficiency higher than 40% at 6 dB back-off across the band. When characterised using a 20 MHz long term evolution (LTE) signal and digital predistortion, the SPA shows good linearity with error vector magnitude <1.3%, and adjacent channel leakage ratio levels better than −45 dBc across the band.
2016 IEEE International Conference on Electronic Information and Communication Technology (ICEICT), 2016
The intrinsic performance of the devices is of great meaning during power amplifiers design. A me... more The intrinsic performance of the devices is of great meaning during power amplifiers design. A method to update de-embedding network at 5.8 GHz for packaged power devices is put forward based on physical modeling idea. The de-embedding network of a packaged GaN HEMT is presented and its errors are analyzed based on waveform engineering. The results may well lead to optimization of the de-embedding network.
2020 International Workshop on Integrated Nonlinear Microwave and Millimetre-Wave Circuits (INMMiC), 2020
The aim of this paper is to improve the linearity of an envelope tracking (ET) power amplifier (P... more The aim of this paper is to improve the linearity of an envelope tracking (ET) power amplifier (PA) using a simple baseband linearisation approach (BLA), which releases the requirement for the ET-customised digital predistortion (DPD) techniques. The proposed BLA is verified through the comparative study on a Gallium Nitride (GaN) PA with ET and a 28V supply voltage. A two-tone signal and a 20MHz modulated signal are used in the measurement, which demonstrates that in contrast to the 28 V case, the ET PA using BLA can simultaneously achieve higher efficiency and better linearity. To investigate the linearity improvement of using BLA, the constellation diagrams, AM/AM and AM/PM characteristics with and without generalized memory polynomial (GMP)-based DPD are measured and analysed.
This Letter presents a novel characterisation system that is able to fully emulate a complete env... more This Letter presents a novel characterisation system that is able to fully emulate a complete envelope tracking power amplifier (ET-PA) environment, with modulated impedance synthesis and dynamic supply voltage generation while using industry-standard modulated signals and digital pre-distortion. The system is used to characterise a 10 W GaN device and provide impedance control over the signal and distortion bandwidths, in response to a 10 MHz long-term evolution signal. A National Instruments PXI-based measurement system is utilised to apply tracking signals to a bespoke supply modulator and successfully improve the average power added efficiency by ~18 percentage points. Three different shaping functions are implemented, and their efficiency and linearity performance evaluated. In addition, digital pre-distortion (DPD) is used to linearise the PA while operating with the three different tracking trajectories. Experimental results demonstrate that when applying shaping functions, a trade-off needs to be made between efficiency and linearity. Even though a constant gain shaping function provides lower efficiency, it achieves good raw linearity performance without DPD, which is a good option if local linearisation is not available. This novel system is a useful tool in the design of ET-PAs, to more completely investigate the performance of the device.
2016 IEEE MTT-S International Wireless Symposium (IWS), 2016
The intrinsic performance of the devices is of great meaning during power amplifiers design. A me... more The intrinsic performance of the devices is of great meaning during power amplifiers design. A method to update de-embedding network at higher frequency for packaged power devices is put forward based on physical modeling idea. The de-embedding network at 5.8 GHz of a packaged GaN HEMT is presented and its practicability is verified through error analysis. This method is prospected to be applied to other packaged microwave devices.
Uploads
Papers by Paul Tasker