A uniplanar microstrip line RF/microwave real-time analog signal processing (RAP) units are proposed in this article to operate concurrently at two frequencies for spectrum aggregation applications. First, a fundamental building block novel microstrip line dual-band Hilbert transformer (DBHT) is developed by integrating a dual-band 180° coupler and a dual-band delay line (DBD). The theoretical analysis is carried out to determine the relation of coupler and delay line forming closed loop resonance in the proposed circuit topology. Then, a dual-band edge detector from DBHT and a dual-band single-sideband (DBSSB) modulator composed of dual-band power divider/combiner (DBPD/DBPC), DBHT, and DBD are developed for dual-band real-time RF/microwave signal processing. To verify the proposed concept, a prototype of microstrip line DBHT working at 0.9 and 1.98 GHz is designed, and the measurement and simulation agree well with theoretical analysis. To demonstrate the real-time RF/microwave analog signal processing, a dual-band edge detector composed of DBHT is verified in the experiment. Furthermore, a prototype of microstrip line DBSSB modulator is fabricated and validated in the experiment to demonstrate the real-time single-sideband modulation at two concurrent RF/microwave frequencies.

In this paper, a novel analytical design technique is presented to implement a coupled-line wideband Wilkinson power divider (WPD). The configuration of the WPD is comprised of three distinct coupled-line and three isolation resistors. A comprehensive theoretical analysis is conducted to arrive at a set of completely new and rigorous design equations utilizing the dual-band behavior of commensurate transmission lines. Further, the corresponding S-parameters equations are also derived, which determine the wideband capability of the proposed WPD. To validate the proposed design concept, a prototype working at the resonance frequencies of 0.9 GHz and 1.8 GHz is designed and fabricated using 60 mils thick Rogers’ RO4003C substrate. The measured result of the fabricated prototype exhibits an excellent input return loss > 16.4 dB, output return loss > 15 dB, insertion loss < 3.30 dB and a remarkable isolation > 22 dB within the band and with a 15 dB and 10 dB references provide a fractional bandwidth of 110% and 141%, respectively.

In this paper, a new analytical design technique for a three-section wideband Wilkinson power divider is presented. The proposed design technique utilizes the dual-frequency behavior of commensurate transmission lines for the even-mode analysis and contributes a set of completely new and rigorous design equations for the odd-mode analysis. Measurement of a fabricated prototype utilizing the proposed technique shows an excellent return-loss (>16 dB), insertion loss (22.7 dB) over 104% fractional bandwidth extending beyond the minimum requirements.

Electromagnetic (EM) fields at a point in space generated by electric/magnetic dipole embedded in a general anisotropic stratified media can be analytically solved [1] by decomposing the fields into transverse electric (TE) and transverse magnetic(TM) modes. The electromagnetic field strengths are dependent on the nature (electric or magnetic) of dipoles, their placement in the stratified media, and relative location of dipoles. A three-layer stratified media has been employed in this paper to model the environment consisting of air, seawater, seabed. The mathematical formulations provided by Tang [1] are used for EM field calculation containing both magnitude and phase information of Ẽ and H̃ fields for dipole antenna of 4 types namely: horizontal magnetic dipole along x- direction (HMDx), horizontal electric dipole along x- direction (HEDx), vertical magnetic dipole (VMD) and vertical electric dipole (VED). Parametric computational investigations are presented to delineate effects of i) the electric and magnetic properties of the media, ii) the nature and orientations of dipole sources, on EM fields at a specified observation point. It is observed that contributions from horizontal electric dipoles have comparable electric and magnetic field strengths at an observation point in the air.

In this paper, a microstrip line Hilbert transformer is proposed to operate concurrently at the dual-frequency for spectrum aggregation real-time analog signal processing applications. The proposed dual-band Hilbert transformer consists of a dual-band 180° coupler and dual-band delay line. The theoretical analysis is carried out to find the relation of coupler and delay line forming closed loop resonance. To verify the proposed design concept, a prototype of Hilbert transformer working at 0.9 GHz and 1.98 GHz is designed and tested, and the simulated and measured results correlate well with each other.