Resonator‐enhanced radiating cable for UHF RFID readers

Abstract An antenna cable for enhancing and adjusting radio coverage is proposed. The presented solution is applied to the UHF RFID range of 866 MHz. With this leaky‐wave antenna cable, radio coverage can be efficient and customizable. A 10 × 100 mm resonator patch is attached on an opening on the cable’s outer conductor to improve its radiating properties. The effect of its displacement is studied through simulations and measurements. The alignment affects both resonance frequency and signal strength. One resonator increases the radiated power by 2 dB (37%), multipliable by adding resonators. However, alignment accuracy of millimeters is needed in many cases. The greatest effect in both operating frequency and transmission loss magnitude comes from lifting the resonator from the cable’s surface, averagely being 7.6% and 8.6% per mm in measured operating frequency and linear magnitude of S21, respectively. Smallest changes are observed when moving the resonator along the cable, being 0.8% and 0.7% per mm, respectively

A resonator enhanced UHF RFID antenna cable for inventory and warehouse applications

Abstract Structures to improve the RF properties of leaky coaxial cables (LCX) are proposed. These resonator structures are optimized for UHF RFID frequency of 866 MHz; however, they are applicable also to other frequencies of interest by redimensioning with corresponding data. Simulations of leaky coaxial cables with resonators (denoted “RCX”) show to improve the antenna gain, which is verified also by measurements. Compared to traditional LCX, RCX have increased radiating power capability while the shape of the propagated wave is also controlled. Cables are simulated with lengths 2.1 m and 6.4 m where the number of radiating slots and resonators is varied. RCXs exhibit a much higher radiation capability than LCXs. The radiation efficiency for RCXs is between 40% ⋯60 % whereas an LCX has only 0.2% efficiency. Simulations are complemented with measurements of the 2.1 m cables. A 30x improvement of the read range of passive RFID tags are reported in tests, from 0.05 m to 1.5 m along the resonator cable. The cable length can be extended so that the signal is carried to the radiating point of the cable using conventional, i.e., non-radiating coaxial cable

Dual-polarized dual fed vivaldi antenna for cellular base station operating at 1.7-2.7 GHz

Abstract The paper presents a novel dual polarized dual fed Vivaldi antenna structure for 1.7–2.7 GHz cellular bands. The radiating element is designed for a base station antenna array with high antenna performance criteria. One radiating element contains two parallel dual fed Vivaldi antennas for one polarization with 65 mm separation. Both Vivaldi antennas for one polarization are excited symmetrically. This means that the amplitudes for both antennas are equal, and the phase difference is zero. The orthogonal polarization is implemented in the same way. The dual polarized dual fed Vivaldi is positioned 15 mm ahead from the reflector to improve directivity. The antenna is designed for 14 dB impedance bandwidth (1.7–2.7 GHz) with better than 25 dB isolation between the antenna ports. The measured total efficiency is better than 0.625 dB (87%) and the antenna presents a flat, approximately 8.5 dB, gain in the direction of boresight over the operating bandwidth whose characteristics promote it among the best antennas in the field. Additionally, the measured cross polarization discrimination (XPD) is between 15 and 30 dB and the 3 dB beamwidth varies between 68° and 75° depending on the studied frequency

Capability assessment of inkjet printing for reliable RFID applications

Abstract In this paper, inkjet-printed silver traces and interconnections produced with the print-on-slope technique were used in an radio-frequency identification (RFID) structure operating in the ultra-high-frequency range. Underfill material was used to attach silicon RFID chips onto flexible, 125-μm -thick polymer substrates. The cured underfill was also used as a sloped surface for printing interconnection traces from the chip to the plastic substrate’s radiators. Inkjet printing was performed in one phase, producing both the interconnections to the chip and the radiators. This enables the use of a single-phase continuous roll-to-roll compatible process instead of the commonly used two-phase stop-and-go process. To further investigate the behavior of the printed low-temperature nanoparticle ink and its compatibility with different substrate materials, basic conductive traces were printed onto the substrates. Thereafter, the structures were exposed to thermal/humidity tests at 85 °C temperature/85% relative humidity (“85/85”) for up to a 2000-h period. To gain an understanding of the response of the structures under stress, the samples were intermittently characterized by using a read range measurement device, followed by the removal of failed samples from the test. The samples were characterized also by optical imaging and field-emission scanning electron microscopy. The bulk conductive traces were characterized electrically by measuring their resistances during test breaks. The results point out that although some challenges are still to overcome, inkjet printing is a feasible way of producing conductive traces for RFID structures, and that the print-on-slope technique is utilizable also in practical applications as a cost-effective method with adequate reliability for producing interconnections between chip and substrate

Polydextrose changes the gut microbiome and attenuates fasting triglyceride and cholesterol levels in Western diet fed mice

Abstract Obesity and dyslipidemia are hallmarks of metabolic and cardiovascular diseases. Polydextrose (PDX), a soluble fiber has lipid lowering effects. We hypothesize that PDX reduces triglycerides and cholesterol by influencing gut microbiota, which in turn modulate intestinal gene expression. C57BL/6 male mice were fed a Western diet (WD) ±75 mg PDX twice daily by oral gavage for 14 days. Body weight and food intake were monitored daily. Fasting plasma lipids, caecal microbiota and gene expression in intestine and liver were measured after 14 days of feeding. PDX supplementation to WD significantly reduced food intake (p < 0.001), fasting plasma triglyceride (p < 0.001) and total cholesterol (p < 0.05). Microbiome analysis revealed that the relative abundance of Allobaculum, Bifidobacterium and Coriobacteriaceae taxa associated with lean phenotype, increased in WD + PDX mice. Gene expression analysis with linear mixed-effects model showed consistent downregulation of Dgat1, Cd36, Fiaf and upregulation of Fxr in duodenum, jejunum, ileum and colon in WD + PDX mice. Spearman correlations indicated that genera enriched in WD + PDX mice inversely correlated with fasting lipids and downregulated genes Dgat1, Cd36 and Fiaf while positively with upregulated gene Fxr. These results suggest that PDX in mice fed WD promoted systemic changes via regulation of the gut microbiota and gene expression in intestinal tract

Effect of voids on thermomechanical cracking in lead-free Sn3Ag0.5Cu interconnections of power modules

Abstract In this article, the effect of voids on thermomechanically-induced failure in the lead-free solder interconnections of power amplifier (PA) modules is investigated. The interconnection of interest is between the module’s flange and substrate (baseplate) initially having a large contact area, and whose cracking has strong detrimental effects on the RF performance and reliability of the PA. PA modules were attached onto baseplates with lead-free SAC305 solder and put to a thermal cycling test (TCT) in the 15 °C to 95 °C range. X-ray imaging was used to characterize the number of voids in interconnections after reflow soldering. The cross-sections of the pristine reflow-soldered and tested interconnections were inspected with cross-polarized light microscopy to reveal the shapes of the voids and crack paths. It was noted that the voids forming in interconnections during the final stages of the reflow process take an elliptical shape, leaning towards the module’s outer edge, due to differences in the thermal expansions of the module and baseplate. During the TCT, high thermomechanical stresses caused localized recrystallization of the as-soldered SAC matrix in the vicinity of the elliptical voids. Finally, creep related intergranular cracks formed in these recrystallized areas. Anand’s viscoplastic model was used to model the void formation and the effect of the formed voids on crack evolution in solder. Simulations of the high creep energy of the elliptical, tilted voids and their correlation with the recrystallization behavior of the SAC305 interconnections were consistent with the observed creep related failures. Confirmed by simulations, these voids are detrimental to the reliability of solder interconnection because the creep strain is strongly localized to the sharp curvatures of the elliptic void

Power module interconnection reliability in BTS applications

Abstract In this paper, the reliability of RF power transistors’ solder attachments is characterized through experiments and simulations. Test cases consisted of power amplifier (PA) modules on AlSi10Mg substrates with either a low or high mutual thermal mismatch. The module’s flange interconnections were stressed by means of thermal cycling testing (TCT) in the 15 °C–95 °C range. Scanning acoustic microscopy (SAM) was used intermittently to inspect the interconnections of selected structures during cycling breaks. Optical cross-polarization microscopy and scanning electron microscopy were used in the failure analysis of the solder joints. Different materials and dimensional variations were tested in simulations to observe differences in thermal stress. The viscoplastic behavior of lead-free solder in the interconnection was modeled using Anand’s constitutive equations. The first cracks could be observed with SAM after 100 cycles. SAM imaging showed that in the worst case, 72% of the interconnection area had cracked at the end of the 1100-cycle TCT. Only a marginal amount of cracks could be observed in PA modules with a better coefficients of thermal expansion match to the substrate. Simulations indicated that it is possible to decrease creep energies significantly and thereby increase the lifetime expectancy of interconnections by selecting the correct materials and structures