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.

Abstract This paper presents a feasibility study of a singlylayered dual-band reflectarray for space applications. The data links should operate simultaneously at K-band downlink frequency band 17.7-20.2 GHz with left-hand circular polarization (LHCP) and at Ka-band uplink frequency band 27-30 GHz with right-hand circular polarization (RHCP). The main aim is to present how a reflectarray can be designed so as to allow reconfigurability of its radiation pattern, especially in terms of beam steering to two different directions. The design is automated by means of a computational tool developed in MATLAB environment interfaced with the electromagnetic simulator CST Studio Suite by means of Visual Basic scripts. Simulation results are presented to demonstrate the efficiency of the proposed computational tool and reconfiguration strategy. dualband dual applications Kband K 17.720.2 177202 17.7 20.2 17 7 20 2 17.7-20. lefthand left hand LHCP (LHCP Kaband Ka 2730 27 30 27-3 righthand right RHCP. RHCP . (RHCP) pattern directions scripts strategy 720 17.720. 17720 177 17. 202 20. 1 17.7-20 273 3 27- (RHCP 72 17.720 1772 17.7-2 17.72 17.7-

Abstract This paper presents a study about the dielectric constant εr, dielectric loss tangent tan g(δ) and effective electrical conductivity σe of graphene, graphite and graphene-bakelite combination using the resonant cavity method. For this purpose, cylindrical samples with diameter of 30 mm and thickness of 4.5 mm were analyzed taking into account the central frequency f0 = 3.5 GHz, according to 5G technology standards. The constants εr and tan g(δ) were obtained from the resonance frequency fa of measured scattering parameters (S-parameters), when the cavity was loaded with the samples. An empirical equation was developed to model the relation between fa and εr. With this empirical equation it was found εr = 9.3203 and tan g(δ) = 0.7000 for graphene and εr = 17.1508 and tan g(δ) = 0.2700 for graphite. The addition of bakelite in combination with graphene allowed controlling the dielectric properties of these composites. The results, obtained in this macroscale characterization, are interesting for Telecommunications Engineering, especially in the development of radiation-absorbent material, which is suitable for mitigation of interference between different wireless communication systems. gδ g δ g(δ graphenebakelite method purpose 3 45 4 5 4. f 35 3. GHz G standards Sparameters, Sparameters S , (S-parameters) 93203 9 3203 9.320 07000 0 7000 0.700 171508 17 1508 17.150 02700 2700 0.270 composites results characterization Engineering radiationabsorbent radiation absorbent material systems (S-parameters 9320 320 9.32 0700 700 0.70 17150 1 150 17.15 0270 270 0.27 932 32 9.3 070 70 0.7 1715 15 17.1 027 27 0.2 93 9. 07 7 0. 171 17. 02 2

Abstract This paper proposes the formulation of a sinusoidal basis function with a novel segmented edge condition to model the impulsive behavior of the surface electric current density at the edges of rectangular microstrip scatterers. In comparison to traditional basis functions, the one considered in this approach demands using very few modes to expand the induced current. The effectiveness of the proposed formulation is validated using the commercial electromagnetic simulator Ansys Designer. Good agreement between the results obtained with the proposed formulation and with the commercial software has been obtained.

Abstract This paper describes the application of the Firefly Algorithm for the optimization of linear and planar antenna arrays. In order to demonstrate the potential of this technique, three applications are reported. The first one is the synthesis of a radiation pattern with isoflux distribution with a non-uniformly spaced linear array composed of isotropic antennas. The second application is the optimization of a non-uniformly spaced planar array composed of isotropic radiators installed on an 8-U nanosatellite. Finally, the optimization of a 3×3 planar antenna array for beam steering with simultaneous side lobe level control is described, whereby the beamforming coefficients were allowed to assume only discrete values. In the three cases considered, good agreement between the desired (mask) and the optimized patterns has been obtained.