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

A theory for magnetic-field effects of nonmagnetic organic semiconducting materials

A universal mechanism for strong magnetic-field effects of nonmagnetic organic semiconductors is presented. A weak magnetic field (less than hundreds mT) can substantially change the charge carrier hopping coefficient between two neighboring organic molecules when the magnetic length is not too much longer than the molecule-molecule separation and localization length of electronic states involved. Under the illumination of lights or under a high electric field, the change of hopping coefficients leads also to the change of polaron density so that photocurrent, photoluminescence, electroluminescence, magnetoresistance and electrical-injection current become sensitive to a weak magnetic field. The present theory can not only explain all observed features, but also provide a solid theoretical basis for the widely used empirical fitting formulas.Comment: 4 pages, 2 figure

Reduced-Rank STAP Schemes for Airborne Radar Based on Switched Joint Interpolation, Decimation and Filtering Algorithm

In this paper, we propose a reduced-rank space-time adaptive processing (STAP) technique for airborne phased array radar applications. The proposed STAP method performs dimensionality reduction by using a reduced-rank switched joint interpolation, decimation and filtering algorithm (RR-SJIDF). In this scheme, a multiple-processing-branch (MPB) framework, which contains a set of jointly optimized interpolation, decimation and filtering units, is proposed to adaptively process the observations and suppress jammers and clutter. The output is switched to the branch with the best performance according to the minimum variance criterion. In order to design the decimation unit, we present an optimal decimation scheme and a low-complexity decimation scheme. We also develop two adaptive implementations for the proposed scheme, one based on a recursive least squares (RLS) algorithm and the other on a constrained conjugate gradient (CCG) algorithm. The proposed adaptive algorithms are tested with simulated radar data. The simulation results show that the proposed RR-SJIDF STAP schemes with both the RLS and the CCG algorithms converge at a very fast speed and provide a considerable SINR improvement over the state-of-the-art reduced-rank schemes

The MicroJansky Radio Galaxy Population

We use highly spectroscopically complete observations of the radio sources from the VLA 1.4 GHz survey of the HDF-N region to study the faint radio galaxy population and its evolution. We spectrally classify the sources into four spectral types: absorbers, star formers, Seyfert galaxies, and broad-line AGNs, and we analyze their properties by type. We supplement the spectroscopic redshifts with photometric redshifts measured from the rest-frame UV to MIR spectral energy distributions. Using deep X-ray observations of the field, we do not confirm the existence of an X-ray-radio correlation for star-forming galaxies. We also do not observe any correlations between 1.4 GHz flux and R magnitude or redshift. We find that the radio powers of the host galaxies rise dramatically with increasing redshift, while the optical properties of the host galaxies show at most small changes. Assuming that the locally determined FIR-radio correlation holds at high redshifts, we estimate total FIR luminosities for the radio sources. We note that the FIR luminosity estimates for any radio-loud AGNs will be overestimates. Considering only the radio sources with quasar-like bolometric luminosities, we find a maximum ratio of candidate highly-obscured AGNs to X-ray-luminous (>10^42 ergs/s) sources of about 1.9. We use source-stacking analyses to measure the X-ray surface brightnesses of various X-ray and radio populations. We find the contributions to the 4-8 keV light from our candidate highly-obscured AGNs to be very small, and hence these sources are unable to account for the light that has been suggested may be missing at these energies.Comment: 20 pages, Accepted by The Astrophysical Journal (scheduled for 1 Jan 2007), color figures 2 and 3 can be found at http://www.astro.wisc.edu/~barger/radiopaper.htm