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A two-stage cascaded power amplifier (PA) employing a proposed Resistor-Capacitor (RC) interstage was provided and simulated. The current-reuse topology is employed at the first stage to lower the power consumption, while the RC interstage helps to enrich the gain flatness and the wideband matching. The shunt peaking topology in a common source configuration is adopted at the second stage to enhance the power gain. The postlayout simulation is performed using the TSMC 65 nm CMOS process operating in a frequency band of 3.1 GHz to 10.6 GHz. The postlayout simulation results indicate that a high flat gain of approximately 22.8 ± 1.2 dB, small group delay variation of ±50 ps, and good input and output matching of less than −10 dB are achieved over the desired working band. Moreover, a saturated output power of 10 dBm and maximum power-added efficiency (PAE) of 29.5% is achieved at 6 GHz. The proposed PA consumes the low power of 15.5 mW from 1.2 V supply voltage.

Some applications are constrained only to implement low cost receivers. In this case, designers are required to use less complex and non-expensive modulation techniques. Differential Quadrature Phase Shift Keying (DQPSK) and Gaussian Frequency Shift Keying (GFSK) can be non-coherently demodulated with simple algorithms. However, these types of demodulation are not robust and suffer from poor performance. This paper proposes a new method to enhance the performance of DQPSK and GFSK using Interactive Kalman Filtering (IKF) technique, in which a one Unscented Kalman Filter (UKF) and two Kalman Filters (KF) are coupled to optimize the demodulated signals. This method consists of simple but very effective algorithms without adding complexity to the demodulators comparing to other very complex methods. UKF is used in this method due to its superiority in approximating and estimating nonlinear systems and its ability to handle non-Gaussian noise environments. The proposed method has been validated by creating a MATLAB/SIMULINK Bluetooth system model, in which the IKF is integrated into the receiver, which implement both DQPSK and GFSK, and run simulation in Gaussian and Non-Gaussian noise environments. Results have shown the effectiveness of this method in optimizing the received signals, and that the UKF outperforms the Extended Kalman Filter (EKF)

The interaction among species is one of the most important factors influencing the distribution of plants in a given habitat. Vegetation of arid rangelands often appears patchy with many herbaceous species associated with shrub species. It was hypothesised that plant interactions among different life forms together with the effect of grazing preference generate this type of spatial distribution of plant species in the semi-arid rangelands of middle Iran. Spatial patterns and associations were quantitatively analysed using Hopkins’ index and Chi-square tests to establish links between spatial relationships, plant life forms and preference by grazers on the south foothills of the Taleghan ranges, Alborz Province. Data were collected from three geographical sites with different dominant species and clumped patterns of plant spatial distributions for these species were detected. These spatial patterns were probably generated by the interplay of life form-dependent facilitative interactions among plants and the grazing pressure on preferred species rather than due to their intrinsic characters. In the study sites, grass species were significantly more frequently observed in the vicinity of nurse species than in open areas. It was also found that plant-plant interactions may change in response to changes in environmental conditions, such as soil characters and the benefits achieved by the beneficiary species from being associated with nurse species. All preferred perennial species were spatially associated with shrub species (Astragalus gossypinus Fischer and Thymus kotschyanus Boiss & Hohen), while nurse species that just physically protect the beneficiary species from grazing (e.g. A. gossypinus) did not associate with non-preferred species (e.g. Stipa barbata Desf). Instead, these non-preferred species may positively aggregate with nurse plants showing other beneficial characteristics such as nitrogen fixation and improvement of soil conditions.

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