A blind, low complex, fast, and highly resistant to attacks watermarking algorithm is proposed for JPEG compressed images. Our method is a discrete cosine transform (DCT) and block based algorithm that adds some Huffman code words to the end of the code sequence of some blocks during JPEG compression procedure. Via a blind approach in decoder, each block is determined to be a watermarked or unwatermarked one. While the robustness to attacks is still preserved, the size of watermarked image may differ from the JPEG compressed one insignificantly. Presented scheme is used for pictures that have perceptually high quality and due to this, are very apt to watermarking task for the sake of contents owner authenticity. Peak signal to noise ratio (PSNR) will be our benchmark to asses the quality of images.
In this study a low-cost 6-bit P-I-N phase shifter with fast switching time, low RF attenuation variation over phase change, and low switching power is described. These unique characteristics make it ideal for S band beam steering applications. The circuit made in microstrip line, consists of six cells in cascade, giving phase shifts of 5.625, 11.25, 22.5, 45, 90, and 180 o , respectively. Each section consists of a 3dB coupler loaded by phase shifting networks. Novel phase shifting networks result in a wide bandwidth, low loss and, ultra low phase error.
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