No abstract

In this work, broadband linear to cross and circular to circular polarization converter for K and Ka-band applications is proposed. The metasurface comprises a novel H-shaped unit cell printed on 1.2 mm thin FR-4 grounded dielectric substrate. It exhibits 90% polarization conversion ratio (PCR) over a bandwidth of 22.26 GHz (17.97-40.23 GHz) with 76.5% FBW maintaining a minimal PCR of 92.5%. The converter also maintains handedness for circularly polarized incident wave. Surface current distributions at different resonant frequencies are analyzed to illustrate the reason behind the broadband behavior.The converter design is simple with the cell periodicity of 0.209λ o and thickness of 0.071λ o , where λ o is the free-space wavelength corresponding to the lowest frequency of the band. Monostatic and Bistatic RCS analysis of the designed converter is performed, demonstrating greater than 10 dBsm RCS reduction over all the frequency range. It shows 16 to 30 dBsm at resonant

Self-phase locked loop (SPLL) through long optical delay lines is investigated for improving the phase noise of the optoelectronic oscillator (OEO) and the voltage-controlled oscillator (VCO). This paper features analytical modeling of close-in to carrier phase noise of oscillators employing SPLL technique using single and multiple delay loops. Experimental results are also provided to verify the analytical modeling and explore critical circuit design parameters to achieve substantial phase noise reduction. Performance comparison is presented for SPLL using electrical phase shifter, Mach-Zehnder modulator (MZM)-based phase shifting, and electrical VCO. Phase noise reduction of 65 dB at 1-kHz offset is achieved for an electrical VCO employing a dual-loop SPLL with 3-and 5-km optical fiber delay lines, whereas the phase locking based on MZM and electrical phase shifter provided 20-and 38-dB reductions at 1-kHz offset for an OEO, respectively.

No abstract

A single radiator that is a part of four-port diversity Multiple-Input Multiple-Output (MIMO) antenna design is composed of four octagonal rings embedded between the two opposite sides of a T-shaped conductive layer surrounded by inverted angular edge cut L-shaped and E-shaped structures. The radiators are placed at the four corners with common ground at the center of a smartphone to form a four-element mobile MIMO antenna. The printing of the antenna is carried out on the flexible polyamide substrate (dielectric constant = 3.5 and loss tangent = 0.0027) with dimensions of 70 × 145 × 0.2 mm3. A wide impedance bandwidth of (84.12%) 2.39 to 5.86 GHz is achieved for all four radiators. The compact size of the radiators along with their placement enables the proposed MIMO antenna to occupy much less area while preserving the space for 2G/3G/4G antennas. The placement of the antennas results in self-isolation between antenna elements by achieving isolation greater than 17.5 dB in the desired operating bands. Furthermore, besides showing a high efficiency of 85% and adequate gain above 4 dBi, good diversity performances such as Envelope Correlation Coefficient (ECC) of less than 0.05, Diversity Gain (DG) of above 9.8 dB, Mean Effective Gain (MEG) of −3.1 dB, Channel Capacity of 21.50 bps/Hz, and Total Active Reflection Coefficient (TARC) of below −10 dB are achieved by the flexible MIMO smartphone antenna. The effect of bending along the X and Y-axis on the performance of the proposed MIMO antenna is also analyzed where decent performance is observed. This makes the proposed flexible four-element MIMO antenna a potential candidate to be deployed in future smartphones.