In this paper, new designs of a bandpass diplexer and switchplexer are presented. Based on the proposed design method, they can be implemented by the direct connection of two parallelcoupled bandpass filters. As a result, the circuit size and mismatch losses can be reduced compared with conventional designs. In addition, based on the proposed filter prototypes, multiple functional blocks in the RF front end can be integrated into a single component. As an example, a balun-integrated bandpass switchplexer that effectively integrates all the functional blocks between the antenna and the TX/RX amplifiers in a single-band RF transceiver is demonstrated. In this way, not only can the level of integration of the RF front end be further improved, but the circuit size and power losses can also be reduced.

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A predictive vector quantizer (PVQ) is a vector extension of a predictive quantizer. It consists of two parts: a conventional memoryless vector quantizer (VQ) and a vector predictor. Two gradient algorithms for designing a PVQ are developed in this paper: the steepest descent (SD) algorithm and the stochastic gradient (SG) algorithm. Both have the property of improving the quantizer and the predictor in the sense of minimizing the distortion as measured by the average mean-squared error. The differences between the two design approaches are the period and the step size used in each iteration to update the codebook and predictor. The SG algorithm updates once for each input training vector and uses a small step size, while the SD updates only once for a long period, possibly one pass over the entire training sequence, and uses a relatively large step size. Code designs and tests are simulated for both Gauss-Markov sources and for sampled speech waveforms, and the results are compared to codes designed using techniques that attempt to optimize only the quantizer for the predictor and not vice versa.

Digital watermarking provides a feasible way for copyright protection of multimedia. The major disadvantage of the existing methods is their limited resistance to both extensive geometric distortions and watermark-estimation attack (WEA). In view of this fact, this paper aims to propose a robust image watermarking scheme that can withstand geometric distortions and WEA simultaneously. Our scheme is mainly composed of two components: (i) mesh generation and embedding for resisting geometric distortions; and (ii) construction of hash-based content-dependent watermark (CDW) for resisting WEA. Extensive experimental results obtained from standard benchmark confirm the ability of our method in improving robustness.

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