A 2GHz GaN Class-J power amplifier for base station applications

The design and implementation of a high efficiency Class-J power amplifier (PA) for base station applications is reported. A commercially available 10 W GaN HEMT device was used, for which a large-signal model and an extrinsic parasitic model were available. Following Class-J theory, the needed harmonic terminations at the output of the transistor were defined and realised. Experimental results show good agreement with simulations verifying the class of operation. Efficiency above 70% is demonstrated with an output power of 39.7 dBm at an input drive of 29 dBm. High efficiency is sustained over a bandwidth of 140 MHz.The design and implementation of a high efficiency Class-J power amplifier (PA) for base station applications is reported. A commercially available 10 W GaN HEMT device was used, for which a large-signal model and an extrinsic parasitic model were available. Following Class-J theory, the needed harmonic terminations at the output of the transistor were defined and realised. Experimental results show good agreement with simulations verifying the class of operation. Efficiency above 70% is demonstrated with an output power of 39.7 dBm at an input drive of 29 dBm. High efficiency is sustained over a bandwidth of 140 MHz

Power amplifier memory-less pre-distortion for 3GPP LTE application

A new and simple Power Amplifier (PA) linearization method is proposed and demonstrated using a very high efficiency yet inherently nonlinear inverse class-F PA. This was conducted in the presence of a generic variable envelope RF signal in order to extract its AM-AM and AM-PM characteristics. Deducing the polynomial pre-distortion parameters from the AM-AM and AM-PM characteristic has resulted in the successful linearization of the PA in the presence of 3GPP Long Term Evolution (LTE) signals. The results obtained for the PA - a 12W GaN HEMT inverse Class-F structure designed to operate at 900MHz - demonstrate the proof of concept and the efficiency of the proposed linearization technique with significant advantageous reduction in base-band resources for 3GPP LTE applications.A new and simple power amplifier (PA) linearization method is proposed and demonstrated using a very high efficiency yet inherently nonlinear inverse class-F PA. This was conducted in the presence of a generic variable envelope RF signal in order to extract its AM-AM and AM-PM characteristics. Deducing the polynomial pre-distortion parameters from the AM-AM and AM-PM characteristic has resulted in the successful linearization of the PA in the presence of 3GPP long term evolution (LTE) signals. The results obtained for the PA - a 12 W GaN HEMT inverse class-F structure designed to operate at 900 MHz - demonstrate the proof of concept and the efficiency of the proposed linearization technique with significant advantageous reduction in base-band resources for 3GPP LTE applications

Performance analysis for partial feedback downlink MIMO with unitary codebook beamforming for LTE

Until recently, mobile communication tasks have been grouped into different layers in a hierarchical layer approach. In this conventional approach, layer-specific protocols are developed and optimised independently. As new wireless applications emerge, requiring high data rates and flexibility for supporting applications with significantly varying QoS requirements, it has become imperative that a higher level of communication between adjacent layers needs to be established. A unitary codebook based beamforming approach has been proposed for LTE that incorporates an improved cross-layer interface in order to improve service to users according to specified QoS criteria. This paper examines this beamforming approach under partial feedback conditions for different MIMO configurations. It is shown that non-obvious precoding matrix selection strategies and scheduling policies for the DLC, can achieve superior performance for LTE system, whilst meeting the QoS requirements of urgent users.Until recently, mobile communication tasks have been grouped into different layers in a hierarchical layer approach. In this conventional approach, layer-specific protocols are developed and optimised independently. As new wireless applications emerge, requiring high data rates and flexibility for supporting applications with significantly varying QoS requirements, it has become imperative that a higher level of communication between adjacent layers needs to be established. A unitary codebook based beamforming approach has been proposed for LTE that incorporates an improved cross-layer interface in order to improve service to users according to specified QoS criteria. This paper examines this beamforming approach under partial feedback conditions for different MIMO configurations. It is shown that non-obvious precoding matrix selection strategies and scheduling policies for the DLC, can achieve superior performance for LTE system, whilst meeting the QoS requirements of urgent users

Pure frequency oscillations of semiconductor lasers with filtered optical feedback

A semiconductor laser subject to delayed filtered optical feedback can show pure frequency oscillations with a period of the order to the delay time, while the power remains practically constant. This is remarkable in light of the strong self-phase modulation in semiconductor lasers that couples frequency and power. It turns out that the dynamics of the filter plays an essential role in this behavior, because it changes the instantaneous amount of feedback in response to the instantaneous laser frequency. By using numerical bifurcation techniques we show how frequency oscillations bifurcate in Hopf bifurcatious from the continuous wave solutions known as external filtered modes

Strangles: The Molecular Identification and Epidemiology of Streptococcus equi subsp. equi

A conventional PCR diagnostic test was established to confirm the microbiological isolation of Streptococcus equi subsp. equi (S. equi), the causative agent of strangles. This test was based on the amplification of the seeI gene, which is species-specific for S. equi. Further, a multiplex PCR was developed using species-specific primers; to identify the presence of S. equi and two other streptococci know complicate the diagnosis of strangles in horses, Streptococcus equi subsp. zooepidemicus (S. zooepidemicus) and Streptococcus dysgalactiae subsp. equisimilis (S. equisimilis). A total of 18 clinical isolates of S. equi plus the Pinnacle IN vaccine isolate, two isolates of S. zooepidemicus and four isolates of S. equisimilis were obtained via culture and used in the development of the multiplex diagnostic tool. Two multiplex tests were trialed; a conventional multiplex PCR and a real-time multiplex PCR. Both the conventional and real-time multiplex PCR’s were able to distinguish between the streptococci and accurately identified all isolates. However, further testing on 26 field specimens revealed that the real-time multiplex PCR had lower specificity, sensitivity and diagnostic accuracy as compared to the conventional multiplex PCR. This was theorised to be the result of the PEG/KOH solution used in the DNA extraction, possibly interfering with the intercalating dye in the real-time reaction. Based on these preliminary results, the conventional multiplex PCR diagnostic test developed here is recommended for further trials to determine its robustness. The 19 S. equi isolates obtained, including the vaccine, were further subjected to epidemiological studies. These included sequencing of the variable N-terminal region of the antiphagocytic M-protein SeM to determine SeM allele subtypes and a Sau-PCR amplification method, which previously has not been trialled on S. equi isolates. Sau-PCR involves digestion of genomic DNA and subsequent amplification. Two novel strains of S. equi were found within NZ based on the variable region of the seM gene, SeM alleles 99 and 100. SeM allele 100 had a higher pervalance over allele 99 as it was isolated in 6 out of 9 outbreaks and was found to occur on both the North and South Islands of New Zealand. SeM allele 99 was only found to occur on the North Island. Further to this study, the Pinnacle IN vaccine strain, SeM 2 was isolated from lymph node abcesses of two horses. It was unclear as to whether this ‘vaccine breakdown’ was just a severe adverse reaction to the vaccine or if the vaccine reverted to a more virulent type. The Sau-PCR was able to differentiate between the field isolates of S. equi and the vaccine strain but was unable to further differentiate between the field isolates and was therefore determined not as valuable for S. equi epidemiological studies

A measurement based feasibility study of space-frequency MIMO detection and decoding techniques for next generation wireless LANs

This article presents a performance evaluation of various multi-antenna concepts based on OFDM for wireless LAN. The studies are based on state-of-the-art measured channel data. The studies aim to assess the MIMO concepts for future high speed W-LA