Sparsity Enhanced Beamforming in The Presence of Coherent Signals

In order to find the directions of coherent signals, a sparsity enhanced beam-forming method is proposed. Unlike the conventional minimum variance distortless response (MVDR) method, the minimum variance in the proposed method corresponds to the orthogonal relationship between the noise subspace and the sparse representation of the received signal vector, whereas the distortless response corresponds to the nonorthogonal relationship between the signal subspace and the sparse representation of the received signal vector. The proposed sparsity enhanced MVDR (SEMVDR) method is carried out by the iterative reweighted Lp-norm constraint minimization. for direction finding of coherent signals. Simulation results are shown that SEMVDR has better performance than the existing algorithms, such as MVDR and MUSIC, when coherent signals are present.

Evaluating of the Axivity accelerometers algorithm in measurement of physical activity intensity in boys and girls

Background: Accelerometers are new but popular tools in measurement of physical activity level but most of them use the algorithms which are more suitable for adults rather than adolescents. Also accelerometers accuracy in assessing physical activity intensity in boys and girls is widely unknown. Therefore, purpose the current study was to evaluate the validity of the Axivity accelerometers in relation to establish algorithm in the measurement of physical activity intensity in boys and girls. Methods: A total of 143 participants recruited from a local school in Oxfordshire and 119 of them (84 boys and 35 girls, age (12.71 ± 0.46)) completed the shuttle run test while wearing an AX3 accelerometer. Signal Vector Magnitude (gravity-subtracted) (SVMgs) and Metabolic equivalent (MET) values were calculated for both of boys and girls. Results: The study result showed that girls had significantly higher SVMgs value (P< 0.05) while according to the standard equations, girls have lower VO2max and MET in each shuttle run lap. Conclusion: This study result suggest that different algorithms might be necessary to measure physical activity in different genders.

Large-signal vector characterization of LDMOS devices for analysis and design of broadband Doherty high-power amplifiers

We present a novel broadband large-signal vector characterization technique, suitable for high-power broadband Doherty amplifiers (DPAs). It consists of characterizing the DPA three-port sub-circuit composed of the main and peak power devices that are inter-connected by the input network. We discuss a suitable way to extract the three-port X-parameters of a DPA sub-circuit, which is based on a pair of high-power Silicon Laterally Diffused MOSFETs (LDMOSs) for UHF applications. It is then applied to the analysis of a high-power broadband DPA developed on the basis of the same DPA sub-circuit. This technique permits the broadband analysis of the operation of the DPA, as well as to get insight on the load modulation for both the peak and main devices, while they mutually interact through the input network. Measurements and simulated data in the 700–960 MHz bandwidth are compared so as to demonstrate the feasibility of three-port X-parameters characterization for high-power DPAs in UHF band.