A >40% bandwidth fully scalable turnstile-based waveguide orthomode transducer having excellent phase performance is described for the WR75 standard rectangular waveguide. Flexible bandwidth tuning is achieved through the use of an interchangeable stepped scattering element. Reduced height waveguide topology provides a simple, compact, and robust design against mechanical tolerances. The intrinsic broadband nature of half-height E-plane bends and single-step power combiners assures high order mode free increased bandwidth in balanced phase operation. The designed orthomode transducer exhibits a return loss better than 23 dB at any port, an insertion loss less than 0.06 dB, and an isolation of 50 dB over the full bandwidth. Moreover, the phase difference between orthogonal polarizations is lower than 0.7° over the band, thus enabling applications where phase-matched outputs are required. This design has been chosen for the QUIJOTE cosmic microwave background experiment due to its cost-effective, compact design, and high-quality performance as well as being readily scalable to the WR51 and WR28 waveguide bands. © 2010 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2010.

This work proposes an easily scalable quadrature hybrid coupler (QHC) topology with two symmetric stepped apertures that originate a square coaxial-like mid-section. This new configuration enables an ultra-compact design, three times shorter than equivalent structures, having 40% of fractional bandwidth with 25 dB of matching/isolation and 1 dB of axial ratio (AR). The impedance transformers can be easily redesigned to meet other requirements related to electrical performance or even other desired coupling values. For verification purposes, a prototype at Ku -band was manufactured and measured showing good agreement with simulation results.

An octave bandwidth concept for compact rectangular-to-circular and square-to-circular waveguide transitions based on the use of intermediate octagonal-shaped sections is presented. Apart from its inherent bandwidth capability and spurious mode free operation, this architecture offers some other useful advantages such as easy fabrication, low losses, and extremely short length (less than 0.75 λ₀ , with λ₀ being the wavelength at the center frequency), which allows their use in the millimeter-wave frequency range. Experimental verification is provided through the measurement of a rectangular-to-circular mode transformer covering more than the super-extended C -band (3.6-7.025 GHz) with 30-dB return loss and 0.1-dB insertion loss, which represents state-of-the-art performance in terms of bandwidth.

This article introduces an easy and accurate technique for the full characterization of septum polarizers (SPs) in back-to-back configuration through standard amplitude/power measurements at the rectangular waveguide ports. The proposed calibration algorithm, based on the use of two simple waveguide sections, along with the developed mathematical formulation, allows the complete extraction of the relevant SP parameters: return loss, isolation, cross-coupling (XP) or axial ratio (AR), and copolarization losses (CP). The methodology has been successfully validated for two different designs at Ku-band.

The objective of the present study is to evaluate the Specific Absorption Rate (SAR) within the human head model exposed to the radiation of planar monopole antenna with T-shaped coupling feed and an inductive shorting strip. The presented design has a compact structure, a planar configuration and occupying a small size of 36×20mm2. Two wide bands can be generated by the proposed antenna 546 MHz (734-1280 MHz) and 1066 MHz (1934-3000 MHz) for the LTE/WWAN/WLAN internal mobile phone. The antenna performance parameters comprising return loss, radiation patterns, and gain are discussed. In this research work four different human head models have been implemented: homogenous spherical head, spherical seven layer model, Specific Anthropomorphic Mannequin (SAM) phantom and HUGO human head model. On the other hand the effects of operating frequency and gap distance between the mobile phone antenna and the human head model on distributions of the SAR inside the human head are investigated. All the simulations are done for three different distances between the antenna and the head model (5 mm, 10 mm and 20 mm). Moreover, the SAR levels for the head tissues are calculated in accordance to the two currently accepted standards: Federal Communications Commission (FCC) and International Commission on Non-Ionizing Radiation Protection (ICNIRP).

Differential phase shifters are common circuits in communication systems where a fixed phase difference between two points within the circuit is required. Among the available technologies, waveguide phase shifters are preferred for applications such as antenna feed or beam-forming networks. Typical designs in the literature are devoted to specific phase delays such as 90° or 180°, but any phase shift might be required, and therefore a design procedure resulting in mechanically-related parameter fitting equations for any arbitrary phase difference would be advantageous. This paper presents a parametric design of full-band (40% relative bandwidth) waveguide differential phase shifters, providing polynomial equations for all design parameters in order to obtain arbitrary phase shifts between standard rectangular waveguides with equal physical lengths. The phase shift is achieved through the use of a multi-step ridge section together with a single width-step in the shift line. The proposed design procedure results in differential phase shifters with 25 dB of return loss and minimal physical length for any phase shift between 0° and 180°. To validate this parametric design process, two exemplary differential phase shifters with 30° and 140° phase shifts were measured, showing very good agreement with the simulated results.