271,541 research outputs found
Novel Compact and High Selectivity Dual-band BPF with Wide Stopband
A novel type of compact and high selectivity dual-band bandpass filter (BPF) incorporating a dual-mode defected ground structure resonator (DDGSR) and a dual-mode open-stub loaded stepped impedance resonator (DOLSIR) is proposed in this paper. Utilizing capacitive source-load coupling and the intrinsic characteristics of the two types of dual-mode resonators, compact dual-band BPF with multi transmission zeros near the passband edges as well as a wide stopband which can be used to achieve high selectivity is realized. An experimental dual-band BPF located at 2.4 and 3.2 GHz was designed and fabricated. The validity of the design approach is verified by good agreement between simulated and measurement results
Low-Complexity Reduced-Rank Beamforming Algorithms
A reduced-rank framework with set-membership filtering (SMF) techniques is
presented for adaptive beamforming problems encountered in radar systems. We
develop and analyze stochastic gradient (SG) and recursive least squares
(RLS)-type adaptive algorithms, which achieve an enhanced convergence and
tracking performance with low computational cost as compared to existing
techniques. Simulations show that the proposed algorithms have a superior
performance to prior methods, while the complexity is lower.Comment: 7 figure
Iterative Equalization and Source Decoding for Vector Quantized Sources
In this contribution an iterative (turbo) channel equalization and source decoding scheme is considered. In our investigations the source is modelled as a Gaussian-Markov source, which is compressed with the aid of vector quantization. The communications channel is modelled as a time-invariant channel contaminated by intersymbol interference (ISI). Since the ISI channel can be viewed as a rate-1 encoder and since the redundancy of the source cannot be perfectly removed by source encoding, a joint channel equalization and source decoding scheme may be employed for enhancing the achievable performance. In our study the channel equalization and the source decoding are operated iteratively on a bit-by-bit basis under the maximum aposteriori (MAP) criterion. The channel equalizer accepts the a priori information provided by the source decoding and also extracts extrinsic information, which in turn acts as a priori information for improving the source decoding performance. Simulation results are presented for characterizing the achievable performance of the iterative channel equalization and source decoding scheme. Our results show that iterative channel equalization and source decoding is capable of achieving an improved performance by efficiently exploiting the residual redundancy of the vector quantization assisted source coding
Optical spectroscopy study of the collapsed tetragonal phase of CaFe(AsP) single crystals
We present an optical spectroscopy study on P-doped CaFeAs which
experiences a structural phase transition from tetragonal to collapsed
tetragonal (cT) phase near 75 K. The measurement reveals a sudden reduction of
low frequency spectral weight and emergence of a new feature near 3200 \cm (0.4
eV) in optical conductivity across the transition, indicating an abrupt
reconstruction of band structure. The appearance of new feature is related to
the interband transition arising from the sinking of hole bands near
point below Fermi level in the cT phase, as expected from the density function
theory calculations in combination with the dynamical mean field theory.
However, the reduction of Drude spectral weight is at variance with those
calculations. The measurement also indicates an absence of the abnormal
spectral weight transfer at high energy (near 0.5-0.7 eV) in the cT phase,
suggesting a suppression of electron correlation effect.Comment: 6 pages, 4 figure
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