Abstract This paper describes the development of a double-sided band-pass frequency selective surface based on Matryoshka geometry, preserving features such as miniaturization, multiband operation and stability of polarization and angle of incidence. Unlike cascaded FSSs, the proposal uses only one layer of substrate, with Matryoshka geometry on one side and a square mesh on the other, reducing volume and simplifying manufacturing by avoiding spacers. The double-sided FSS allows the frequency response to be adjusted using the geometry of the opposite face, which in this work is a square loop. With an attenuation of -10 dB, the proposed configuration offers a free band from 3.48 GHz to 9.06 GHz, compared to the original configuration, which ranged from 5.88 GHz to 7.43 GHz, with only 1.55 GHz free. Initial design equations are presented which facilitate the creation of FSSs for other frequencies and applications. An FSS has been designed, fabricated, and characterized, with good agreement between numerical and experimental results. The resonant frequency remains practically constant for different incidence angles, from 0º to 60º, confirming the angular stability. doublesided double sided bandpass pass miniaturization substrate spacers face loop 10 -1 dB 348 3 48 3.4 906 9 06 9.0 588 5 88 5.8 743 7 43 7.4 155 1 55 1.5 applications designed fabricated characterized results angles º 60º - 34 4 3. 90 0 9. 58 8 5. 74 7. 15 1.

Abstract This paper presents a novel design of an X-band (812 GHz) 4-bit monolithic microwave integrated circuit (MMIC) type true-time-delay (TTD) line for wideband high-resolution imaging radar applications. The designed TTD line circuit offers a maximum time delay of 920 picoseconds (ps) using eight 115 ps delay elements and a distributed switching network. The unit delay line is synthesized using an artificial transmission line (ATL) circuit and implemented in a compact form of 18.5 mm2 using 130 nm gallium arsenide (GaAs) pseudomorphic high-electronmobility-transistor (p-HEMT) technology. The size of the switches and characteristic impedance of the transmission lines have been optimized to minimize insertion loss variation across different delay states while maintaining a flat delay response over a wide bandwidth. A basic 115 ps delay line cell is fabricated to prototype the circuit using GaAs-based MMIC processes. The final 920 ps chip layout simulation exhibited input and output return loss of better than 10 dB, insertion loss of 28±2 dB, and group delay variation of ±10 picoseconds over a 4 GHz bandwidth. Xband X band 812 (81 4bit bit (MMIC truetimedelay true (TTD highresolution high resolution applications 92 (ps 11 network ATL (ATL 185 18 5 18. mm 13 GaAs (GaAs highelectronmobilitytransistor electronmobility transistor pHEMT p HEMT (p-HEMT technology bandwidth GaAsbased based processes 1 dB 282 28 2 28± ±1 81 (8 9 ± 8 (

Abstract This paper presents the design of a dual-band and dual-polarized microstrip antenna for global navigation satellite systems reflectometry (GNSS-R) for the L1/E1/B1 and L5/E5a/B2a bands. In order to allow advanced GNSS-R signal processing and sensing techniques, the design has been carried out for dual-band and dual-polarization operation with isolated ports to receive both left and right-hand circular polarizations. The design procedure to allow receiving both bands independently and with high isolation is described in detail. Numerical and experimental results show that the antenna presents good performance in terms of impedance matching, circular polarization purity and isolation between the ports. The measured levels of axial ratio are 0.86 dB and 1.89 dB for the L1/E1/B1 and L5/E5a/B2a bands, respectively. The measured isolation levels are larger than 30 dB and 40 dB in the L1/E1/B1 and L5/E5a/B2a bands, hence proving that the proposed antenna concept can be properly used in dual-band dual-polarized GNSS-R applications. dualband dual band dualpolarized polarized GNSSR GNSS R (GNSS-R L1E1B1 LEB L1 E1 B1 L E B L1/E1/B L5E5aB2a LEaBa L5 E5a B2a techniques dualpolarization righthand right hand polarizations detail matching 086 0 86 0.8 189 1 89 1.8 respectively 3 4 applications L1E1B aB Ea Ba 08 8 0. 18 1.