Prephase-Based Equivalent Amplitude Tailoring for Low Sidelobe Levels of 1-Bit Phase-Only Control Metasurface under Plane Wave Incidence

<p>A prephase synthesis method is proposed for sidelobe level (SLL) suppression of a 1-bit phase-only control metasurface under plane wave incidence. The array factor of the metasurface with N×N unit cells shows that controlling the number of prephases with varying values over the reflective surface realizes equivalent amplitude tailoring. Different from optimizing the prephase distribution, selection of the numbers of 0 and π/2 prephases in specific N regions is used to suppress the SLLs. Therefore, the parameters in the optimization can be dramatically reduced from N² to N. The prephase distribution is then designed based on the optimized number of prephases and a symmetric matrix for SLL suppression in the whole space. The SLLs are further suppressed by optimizing some of the unit cell states based on similar equivalent amplitude tailoring. Simulation and measurement of a set of 1-bit reflective metasurfaces with 20×20 unit cells verify that the phase-only control metasurface realizes SLL suppression to -13 dB for multiple beam directions from -30 to 30 degrees with a 10-degree step under normal plane wave incidence.</p>

Prephase-Based Equivalent Amplitude Tailoring for Low Sidelobe Levels of 1-Bit Phase-Only Control Metasurface under Plane Wave Incidence

<p>A prephase synthesis method is proposed for sidelobe level (SLL) suppression of a 1-bit phase-only control metasurface under plane wave incidence. The array factor of the metasurface with N×N unit cells shows that controlling the number of prephases with varying values over the reflective surface realizes equivalent amplitude tailoring. Different from optimizing the prephase distribution, selection of the numbers of 0 and π/2 prephases in specific N regions is used to suppress the SLLs. Therefore, the parameters in the optimization can be dramatically reduced from N² to N. The prephase distribution is then designed based on the optimized number of prephases and a symmetric matrix for SLL suppression in the whole space. The SLLs are further suppressed by optimizing some of the unit cell states based on similar equivalent amplitude tailoring. Simulation and measurement of a set of 1-bit reflective metasurfaces with 20×20 unit cells verify that the phase-only control metasurface realizes SLL suppression to -13 dB for multiple beam directions from -30 to 30 degrees with a 10-degree step under normal plane wave incidence.</p>

The optical system of the Tenerife Microwave Spectrometer: a window for observing the 10–20 GHz sky spectra

The TMS optical system is based on a decentered dual-reflector system in a Gregorian configuration to observe with an angular resolution of less than 2°. The primary goal of the present study is to evaluate the final design and verify that it satisfies the design requirements. We aim for low cross-polarization (-30 dB), low sidelobe (-25 dB) levels, and a stable beam in terms of shape (low ellipticity) and size over a full octave bandwidth (10–20 GHz). We performed both ray-tracing and full-wave simulations using the CST Studio software in order to investigate the system behaviour. We gave special attention to the beam frequency variation and polarization leakage. We have characterized the effects on the radiation pattern produced by the cryostat window. We present the final design of the TMS optical system, as well as a complete study of the system's performance in terms of cross-polarization, sidelobes, ellipticity and beamwidth. We discuss the effects of sidelobes and study the need for a baffle.

Design of A Ka-Band 3D-Printed Dual-Polarization Magnetoelectric Dipole Antenna Array with Low Sidelobe

A Ka-band dual-polarization magnetoelectric (ME) dipole antenna array based on three-dimensional (3D)-printed technology with low sidelobe level (SLL) is proposed in this paper. The metal posts and cross-slots are explored to build a novel subarray with 2 × 2-unit ME-dipoles as the basic element. Creatively, a square waveguide to cross-slots transition with a pyramid horn cavity structure is investigated to feed the ME-dipole subarray. Furthermore, two types of power-tapering corporate-feed networks with laminated structures are used to design an 8 × 8-unit low-SLL array. The fabricated array has a relative bandwidth (VSWR < 2) of 14.3% and 17.1%, with a realized gain higher than 25.8 dBi and 26.1 dBi for the H-pol. and V-pol., respectively. The maximum radiation efficiency for both arrays is 73.2%. The measured first sidelobe levels are less than –17.5 dB for both polarizations. With competitive performance and low fabrication cost, the proposed dual-polarization ME-dipole antenna array would be valuable for polarization-agile radar and communication systems.

Hybrid FSK-PSK Waveform Optimization for Radar Based on Alternating Direction Method of Multiplier (ADMM)

In this paper, a new radar signal modulated with a hybrid of the frequency shift keying (FSK) and the phase shift keying (PSK) signal—i.e., the FSK-PSK signal—is studied. Different phase encoding sequences are used to modulate the sub-pulses to obtain lower sidelobe levels and ensure signal orthogonality. In addition, to counter intra-pulse slice repeater jamming of specific length generated by the enemy jammer, an orthogonal waveform made of sub-pulses of equal length based on the FSK-PSK modulation scheme is designed. The simulation results show that the optimized discrete phase encoding sequence can significantly enhance the orthogonality of the sub-pulse in the FSK-PSK signal and effectively suppress the slice repeater jamming. Two algorithms are proposed: (1) the low sidelobe waveform optimization algorithm based on ADMM (LSW-ADMM); and (2) the anti-slice-repeater-jamming algorithm based on ADMM (ASRJ-ADMM). Both algorithms exhibit fast convergence speed and low computational complexity.