Arbitrary-angle single-step waveguide twist for quasi-octave bandwidth performance

A quasi-octave bandwidth arbitrary-angle compact waveguide twist using a single matching step is presented. The proposed twist, based on a single intermediate ridge waveguide section that broadens its mono-mode operation, exhibits a similar wave impedance to the rectangular waveguide connected to its ports thus facilitating the reflections minimization in an extended frequency range. An exemplary 45° twist has been manufactured in the 10 GHz to 19.3 GHz frequency range (~64%) for demonstration purposes. The measured data are in concordance with those predicted by the simulation. This result represents, to the authors' knowledge, today's state-of-the-art in terms of compactness and bandwidth performance.This work was supported by the Spanish Ministry of Economy and Competitiveness (reference ESP2015-70646-C2-2-R) and FEDER funding from the EU

Quasi-octave bandwidth phase matched K/Ka antenna feed subsystem for dual

The architecture concept and fabrication of a quasi-octave bandwidth waveguide feed network for circular polarized antennas is discussed here. The main advantages of this extremely compact topology rely on three key achievements: the instantaneous bandwidth capability, the axial ratio improvement and the significant size reduction which is in many cases determinant in antenna feed subsystems. Experimental measurements exhibit very good agreement with the predicted results given by conventional mode matching techniques. The overall structure provides an axial ratio as low as 0.7 dB along with a return loss better than 25 dB, at every waveguide port, over the whole bandwidth (60%), which represents the today's state-of-the-art. Moreover, yield analysis and simple scaling properties assure the use up to Q band

On the use of a new class of simplified multi-window iris notch in the design of ultra-compact high-rejection waveguide filters for satellite links

This work introduces a simplified multi-aperture iris notch suitable for designing waveguide filters having an extremely improved compactness/rejection ratio, regarding available solutions, and adequate pass-band performances. The proposed iris architecture, analyzed for the first time, exhibits a unique transmission zero in the waveguide mono-mode bandwidth which can be easily located below or above the pass-band. The frequency of this transmission zero is evaluated in terms of the iris dimensions thus providing useful guidelines for designing filters with suitable responses. As a consequence of this simplified topology, any designed filter can be easily manufactured by cutting along its E-field symmetry plane. This strategy greatly improves the filter’s insertion loss regarding classical implementations based on more complicated arrangements with piled thin metallic sheets. Two exemplary filters have been designed and tested to be used in a high-performance X-band SATCOM terminal with an 80% size reduction with respect to the existing systems. Both filters covering the Rx (7.25–75 GHz) and Tx (7.9–8.4 GHz) sub-bands show a reflection of −25 dB with insertion losses below 1 dB in the pass-band, whereas they present a very sharp out-of-band rejection of at least 90 dB, that is, a 600 dB/GHz slope at X band.This work was supported by the State Research Agency, Spanish Ministry of Economy, Industry and Competitiveness, through project TEC2017-83343-C4-1-R and FEDER funds from the EU

In-Lab calibration of single TE21 monopulse tracking systems

Autotrack systems for space applications are typically based on monopulse. These systems require a specific test before being operative, typically through calibration towers, leading to expensive operating costs and antenna downtime. This work aims to present a technique to test in-lab these systems by the generation of high order modes as if they would be coupled using a calibration tower as well-known target. The theoretical working principle and a proof-of-concept design will be presented in Ku-band to confirm the reliability of the model

Ambulatory Blood Pressure Monitoring in the Elderly

The incidence of hypertension is high in the elderly and is present in 2/3 of the patients older than 65 years. Prevalence can reach 90% in patients older than 80 years. The presence of isolated systolic hypertension (ISH) is characteristic of this population. However, the prevalence of hypertension by ambulatory blood pressure monitoring (ABPM) is not well known. In this study, we analyzed the special characteristics of hypertension in this population, giving special emphasis on ABPM readings

Full-band oversized turnstile-based waveguide four-way power divider/combiner for high-power applications

Very high-power and high-efficiency microwave applications require waveguide structures to combine/divide the power from/to a variable number of high-power solid-state devices. In the literature, among the different waveguide configurations, those capable of providing the maximum output power show a limited relative bandwidth. To overcome this limitation, in this paper a full-band (40%) waveguide power divider/combiner specifically designed for high-power applications (up to several kW) is presented. The proposed structure uses an evolved turnstile junction with a standard rectangular waveguide common port, rotated 45°, with respect to its central axis, to divide/combine the signal to/from the four output/input rectangular ports. The inclusion of an oversized central cavity together with circular and rectangular waveguide impedance transformers at the common port allows the achievement of a full-band operation with excellent electrical performance, while maintaining a very simple and compact configuration. Only two layers of metal are required for the physical implementation of this structure in platelet configuration. A prototype has been designed covering the full Ka-band (26.5-40 GHz), showing an excellent measured performance with around 30 dB of return loss, 0.18 dB of insertion loss, and less than 1.5° of phase imbalance

Compact K/Ka 4-port feed subsystem for dual circular polarisation

A compact four-port dual circular polarization feed antenna system for satellite communication is described. It consists of a septum Polarizer and two identical duplexers formed by an E-plane T-junction and of two iris filters, along with two electric field rotators since the vectors of the electric field in the rectangular ports must be vertical. This 4-ports system transmits and receives radio frequency signals in double track in which the transmission Tx is made through two ports having as access the standard rectangular waveguide WR42 and the reception RX is made also through two ports having as access the standard rectangular waveguide WR28. To separate the two ways at the circular common port (or rather at the antenna level) RHCP and LHCP was used.The authors would like to thank Spanish MICINN and AECID through their codes TEC-2008-06684-C03-01, CSD2008-68, and D/018607/08 for their human capital support. Also, the authors wish to thank the staff of the Spanish Agency for International Development Cooperation (AECID) as well as Indra Espacio for their useful suggestions

Highly efficient monopulse tracking feed subsystem for unmanned aerial vehicle

A monopulse tracking subsystem for unmanned aerial vehicle is described. It is composed of a septum polarizer and a TM01 circular waveguide mode tracking coupler. The tracking coupler utilizes only two parallel slots for sensing TM01 mode which made the system more compact along with a very small size. The whole monopusle tracking subsystem was designed, fabricated and tested for the Ku-band (14.4-15.5). It provides an excellent return loss > 28dB, an axial ratio better than 0.45dB and an isolation between the sum and the difference signals more than 50dB.The authors would like to thank Spanish MICINN and AECID through their codes TEC-2008-06684-C03-01, CSD2008-68, and D/018607/08 for their human capital support. Also, the authors wish to thank the staff of the Spanish Agency for International Development Cooperation (AECID) as well as Indra Espacio for their useful suggestions

A wideband correlation and detection module based on substrate-integrated waveguide technology for radio astronomy applications

A wideband (30% relative bandwidth) correlation and detection module based on substrate-integrated waveguide (SIW) technology intended for a radio astronomy polarimeter is presented. The SIW circuit is a six-port network with two input ports that are correlated in two hybrid couplers and their corresponding output signals are routed to Schottky diode detectors, which are designed using microstrip technology and assembled within the same system. The designed SIW structure includes hybrid couplers, power dividers, a 90° phase shifter, and 90° bends, providing a real implementation of a functional system with improved bandwidth performance from 35 to 47 GHz. Experimental results are in concordance with simulations, and they validate the module operation for the proposed application.This work was supported by the Spanish Ministry of Economy and Competitiveness under Project AYA2013-49759-EXP

Novel full-band waveguide polar modulator for radio astronomy applications

A novel full-band (40% relative bandwidth) waveguide polar modulator (WPM) design based on a new architecture with two turnstile junctions and a nearly frequencyindependent differential 180° phase shift between orthogonal arms is presented. The use of suitably designed turnstile junctions together with antiphase waveguide-coaxial-waveguide transitions in reduced-height waveguide technology enables the improvement of bandwidth over previous WPMs with a very compact and simple solution. This design enables continuous rotation about its central axis at 40 revolutions/s, which makes the modulator suitable for receivers with significant 1/f noise such as cryogenic radiometers. The polar modulator presented in this paper is designed to be cooled down to cryogenic temperatures in order to reduce its contribution to the receiver noise. This design is suitable for radio astronomy applications due to its costeffective, compact design, and high quality performance as well as being readily scalable. A polar modulator in the Ka-band (26.5-40 GHz) has been designed to show a reflection better than -20 dB, an insertion loss around 0.3 dB, and a cross-coupling near -35 dB measured at room temperature (T = 298 K). This insertion loss is reduced by 30%, while the phase difference and cross-coupling maintain similar values when the polar modulator is cooled to approximately T = 80 K.This work was supported by the Spanish Ministry of Economy and Competitiveness under the CONSOLIDERINGENIO 2010 program and project CSD2010-00064