To resist geometrical attacks, the video zero watermarking algorithm based on logpolar transform presented in this paper. In our method, an original image transformed in logpolar coordinate after transformation of 2D DWT and 3D DCT. In experiment, the proposed method was evaluated the performance of resistance against attacks such as noise attack, rotation attack, compression attack and frame attack. The experiment results show that this algorithm can effectively resist against geometric attacks, and it has high robustness to the noise, filtering, compression and other common attacks. The bit error rate of the proposed algorithm is less than 0.06 for all tested attacks.

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In this paper, a balanced-to-balanced filtering directional coupler (FDC) that can realize a 3 dB coupling degree directional coupler with high isolation and directivity is proposed. The design of the proposed FDC is primarily based on microstrip/slotline transition structures, resonance structures, and odd–even mode phase velocity compensation structures. A U-type microstrip feed line integrated with a stepped-impedance slotline resonator is adopted at the input and output ports, which makes the differential-mode (DM) responses independent of the common-mode (CM) ones, and brings superior DM transmission and CM suppression. In addition, by loading the microstrip stub-loaded resonators (SLRs), a DM passband with sharp filtering performance is realized, and transmission zeros (TZs) can be added into the design, which makes it more selective. Moreover, phase compensating slotlines are added into the coupling structure to enhance the isolation. In order to verify the feasibility of the proposed design method, an FDC prototype circuit was made and tested. The simulation results are in good agreement with the measured results. The designed coupler’s DM operating band covers 2.65 GHz to 3 GHz (FBW = 12.4%), and the insertion and return losses are 4.6 dB and 20 dB, respectively. The isolation degree is better than 15 dB, and the CM suppression is more than 55 dB. The total coupler size is about 67.7 mm × 63.8 mm. The designed balanced-to-balanced FDC can be widely used in S-band wireless communication systems.

A reconfigurable balanced phase shifter is designed in this paper, which can achieve stable differential mode (DM) phase shift and high common mode (CM) suppression. The proposed balanced phase shifter is mainly composed of micro strip/slot line transition structure and π-shape slot line. The U-shaped micro strip line and the stepped impedance slot line are employed to form the differential input and output ports, which can make the DM response and the CM one are independent. By switching the PIN diode on or off, a stable 180 DM phase shift difference is achieved between two states. In order to verify the design, a 180 balanced phase shifter with a central frequency of 4.7 GHz was simulated and fabricated. DM insertion loss of the design is 1.1 dB, DM phase deviation range is ±5 , 10 dB DM impedance matching fractional bandwidth is 45%, and phase fractional deviation bandwidth is 42%. Meanwhile, the CM rejection can reach about 35 dB. The simulation and measurement are in good agreement with the theory.