A new binary version of Particle Swarm Optimization called Boolean PSO (BPSO) is applied in order to design current dividers that distribute the current to three output ports and resonate simultaneously at three frequencies. The BPSO is based on the negative selection, which is one of the basic processes in an Artificial Immune System (AIS). The optimizer must satisfy specific requirements at all resonant frequencies, concerning the impedance-matching bandwidth and the distribution of the complex current on unmatched real or complex terminal loads. The dividers are considered to feed mobile communications antenna arrays and are optimized for GSM/DCS/UMTS operation. The optimization is performed by applying both the BPSO and a conventional PSO. The comparison shows that the BPSO is more efficient because it has the ability to produce structures with better frequency response.
A broadband microstrip-to-coplanar waveguide (CPW) transition using two parallel folded balun structures with easy transmission band control for various RF circuits and integrated systems is proposed in this paper. Each balun is employed an open-circuited microstrip line and a short-circuited slotline with one quarter-wavelength long each. As the change of the length of the open and short circuits, the transmission band can be easily controlled. The measured return and insertion losses are better than 10dB and 1.4dB, respectively, over the bandwidth of 82.5% at the center frequency of 6GHz.
Optical and morphological properties of self-assembled InAs quantum dots (QDs) covered by InxGa1-xAs strain reducing layers (SRL) with different thicknesses (2, 4, 6 and 8nm) and compositions (x=0.13, 0.18 and 0.30) were investigated. Photoluminescence from InAs QDs shows the dependence on indium mole fraction and thickness of the overgrown InxGa1-xAs SRL.Improvement in PL intensity and narrowing of PL width up to 26meV occurred together with a red shift of up to 138nm when the QDs were coved with 6nm of In0.18Ga0.82As. Also, we found that when the total amount of InAs deposited to form the QDs and the SRL was larger than a critical value of around 6MLs, the surface roughness increased and the PL intensity decreased drastically.
A new method of designing FIR notch filters with arbitrary notch frequency is proposed, where a modified sampling kernel is introduced and utilized along with a complementary filter concept. In particular, the proposed sharp notch FIR filter design provides a closed-form solution for filter coefficients, leading to further utilization for designing reconfigurable FIR notch filters.
A novel switched-RC sampling MDAC is proposed to obtain high linearity under low-voltage and low-power conditions without significant degradation in speed or causing any reliability problem. Moreover, the proposed MDAC has the capability of working as the front-end stage of a pipelined ADC while its front-end S/H stage has been removed to save power consumption. The proposed techniques have been employed to design a 10-bit 100MSample/s ADC with 1Vp-p, diff input signal in a 90nm CMOS process and 0.9V supply voltage. Results show an SNDR of 59dB and an SFDR of 66dB while consuming 15.8mW power.
A compact accurate scalable model for CPW on InP with a single under-bridge is successfully established and testified by both measurements and EM simulations up to 50GHz. Then it helps realize a novel matching network design consisting of only two under-bridges beneath CPW, with the functions of both even mode impedance matching and odd mode suppression.
We first offer a so-called limit explanation of 2-D 1/ƒ spectra by which a 2-D 1/ƒ signal is regarded as the limit of a family of stationary processes. With such a representation, a new method to generate 2-D 1/ƒ behavior via dyadic wavelets is proposed. A variety of numerical experiments are presented to demonstrate the accuracy of the proposed fractal model.