In situ endoscopic observation of higher-order mode conversion in a microwave mode converter based on an electro-optic probe system

Visualizing the electromagnetic field transformation inside a microwave mode conversion region has been considered to be only realizable by simulation studies. For the first time, we present a comprehensive experimental observation of the electric field transformation occurring inside a metallic waveguide TE01-to-TE02 mode converter. An efficient electro-optic (EO) probe and its associated probing system were used for measuring the electric field pattern in the external near-field region as well as in the internal and penetrated region of the mode converter. Utilizing the optically measured field patterns at the aperture of the mode converter, the conversion performance from the TE01 mode to the TE02 mode can be also evaluated. Experimentally measured field patterns near the apertures show excellent agreement with simulation data. The mode conversion to the next higher-order mode (TE01 to TE02) was experimentally demonstrated with phase-stabilized and field-animated post processing. The presented in situ endoscopic photonic measurement technique for the field evolution inside a semi-enclosed structure could be used for visually inspecting manufacturing errors in fabricated structures, and could be of great interest for research on higher-order mode formation and transmission.open0

Efficient Verifiable Image Redacting based on zk-SNARKs

Image is a visual representation of a certain fact and can be used as proof of events. As the utilization of the image increases, it is required to prove its authenticity with the protection of its sensitive personal information. In this paper, we propose a new efficient verifiable image redacting scheme based on zk-SNARKs, a commitment, and a digital signature scheme. We adopt a commit-and-prove SNARK scheme which takes commitments as inputs, in which the authenticity can be quickly verified outside the circuit. We also specify relations between the original and redacted images to guarantee the redacting correctness. Our experimental results show that the proposed scheme is superior to the existing works in terms of the key size and proving time without sacrificing the other parameters. The security of the proposed scheme is proven formally

Development of an Energy-Recirculating Micromachined G-band Folded Waveguide Traveling Wave Tube Oscillator

Department of Electrical Engineeringclos

Nano-CNC fabricating Y-band folded waveguide backward wave oscillator

We present simulation results on a Y-band folded waveguide backward wave oscillator (BWO). Since the finalized circuit will be fabricated by nano-computer numerical control machining, we obtained its parameters from analytic equations with considering cutting tool's dimensions. Depending on the different number of periods, BWO's generated frequency and power were obtained. A cold test and hot test of the circuit is discussed in simulation level

High-Directivity Orbital Angular Momentum Antenna for Millimeter-Wave Wireless Communications

Although orbital angular momentum (OAM) millimeter-wave wireless communications have attracted much attention given their potential to provide an additional degree of freedom in channel capacity, they still face challenges for realization. For instance, the OAM Although orbital angular momentum (OAM) millimeter-wave wireless communications have attracted much attention given their potential to provide an additional degree of freedom in channel capacity, they still face challenges for realization. For instance, the OAM beam diverges rapidly in free space, limiting the coverage of wireless communication. To increase the communication range, we propose a high-directivity broad-bandwidth OAM antenna, which consists of a nonlinear taper and a lens-integrated metamaterial structure (MMS). A linearly polarized TE (transverse electric)(11) mode traverses through the antenna to generate two OAM modes with the low reflectance of the MMS and a low divergence angle (DiA). We evaluate these two factors separately and analyze the effect of reducing the OAM DiA. Then, we validate the OAM antenna using the CST Microwave Studio software and experimentally verify its performance. The measured mode patterns are quantitatively analyzed using a cross correlation function and by calculating the beam DiA from beam radius variations. The proposed OAM antenna provides a novel approach to effectively reduce the DiA of the OAM beam and may be suitable for realizing millimeter-wave wireless communications