Ramiro A. Ramirez

3D tag with improved read range for UHF RFID applications using Additive Manufacturing

In this paper a 3D tag antenna geometry is proposed for UHF RFID systems. Two antennas were built over different dielectric materials with similar properties using both Direct Digital Manufacturing and traditional photolithography and copper etching. The impedance matching between the antenna arms and the passive RFID integrated circuit was accomplished with the H-slot matching technique with a simulated 10 dB return loss bandwidth that allows the tag to operate in the American and European ISM RFID bands of 902-928 MHz and 864-868 MHz, respectively. The antennas were compared to commercially available tags in size, weight and read distance, showing a read range improvement of 136% (for a threshold power of 30 dBm) with respect to the best tag tested. A reduction in length of 78 % with respect to a planar 2D model was also achieved. The radiation patterns were measured, showing an omni-directional beam pattern.

Low permittivity cladding to improve the performance of dielectric rod waveguides and dielectric end-fire antennas

A low loss dielectric rod waveguide design is proposed for use at Ku band. Measured waveguide performance from 10 to 18 GHz is presented and validated using full wave numerical simulations. The proposed design uses a low permittivity cladding to improve performance at the low end of the operating frequency band. Moreover, an improvement of the waveguide isolation due to the cladding is analyzed as well. The proposed ABS cladding is also implemented on a dielectric end-fire antenna obtaining an improvement in return loss, gain and half power beamwidth at the low end of the Ku band; the measured peak gain at 12.2 GHz is 14.6 dBi and 9.8 dBi with and without the cladding, respectively, and the 3 dB beamwidth changes from 22 to 61 degrees.

Reduced-size circular polarized antenna for 434MHz RFID systems using meandered bowtie elements with a novel quadrifilar feed

A meander-line antenna fed in quadrifilar fashion for circular polarized (CP) operation is presented. The antenna and feed network are designed to operate in the 434 MHZ RFID/ISM band (432-435 MHz in this application). The four bowtie elements are fed by a 180 power splitter and 90 degree phase shifters to achieve circularly polarized radiation. Initial measurements show good performance in the 432-435 MHz band, with an axial ratio of 0.72 dB at 434 MHz. The CP performance was demonstrated in a 2×1 and 4×1 array with measured axial ratios of 1.5 and 2 dB, respectively. A 3 dB beam width of 65° and 48° for the 3×1 and 4×1 array was also achieved, respectively.

MMIC packaging and on-chip low-loss lateral interconnection using additive manufacturing and laser machining

A new and versatile 3D printed on-chip integration approach using laser machining is demonstrated in this paper for microwave and mm-wave systems. The integration process extends interconnects laterally from a MMIC to a chip carrier. Laser machining techniques are studied and characterized to enhance the 3D printing quality. Specifically, the width of microdispensed printed traces is accurately controlled within micrometer range and probe pads are formed by laser cutting to facilitate RF measurement. S-parameters of a distributed amplifier integrated into the package are simulated and measured from 2 to 30 GHz. The overall performance is significantly better than traditional wirebonded QFN package. The attenuation of the microstrip line including interconnects is only 0.2 dB/mm at 20 GHz and return loss with the package is less than 10 dB through-out the operating frequency band.

Laser enhanced direct print additive manufacturing for mm-wave components and packaging

Direct print additive manufacturing (DPAM) is an additive manufacturing technique that combines fused deposition modeling with micro-dispensing. As a multimaterial 3D printing method it has proven to be effective for fabricating printed electronics that operate in the microwave frequency range. This paper discusses the addition of picosecond laser processing to the DPAM process, and the enhancements to high-frequency performance and design capability that are made possible. The use of laser-enhanced DPAM for 3D fabrication of transmission lines, passive components and packaging is discussed.

UHF RFID Tags for On-/Off-Metal Applications Fabricated Using Additive Manufacturing

Radio frequency identification (RFID) tag design is generally focused specifically on either off-metal or on-metal configurations. In this letter, passive 2-D and 3-D RFID tags are presented, which perform similarly in both configurations. The tags operate in the industrial, scientific, and medical (ISM) RFID UHF bands (864–868 MHz and 902–928 MHz). A matching loop consisting of two parallel stubs to ground is used for impedance matching to a passive integrated circuit, which has −18-dBm sensitivity. A planar 2-D tag with a footprint of 13126.5 mm2 is first introduced, showing a simulated gain of approximately 3 dBi and a measured read range of 10 m (for 31-dBm transmit power from the reader) in both on-metal and off-metal conditions. The tag is miniaturized into a 3-D geometry with a footprint of 2524.25 mm2 (520% reduction) and achieves the same broadside simulated on-metal gain. The antennas are fabricated using a 3-D printed acrylonitrile butadiene styrene. The conductive layer is realized by microdispensing silver paste (Dupont CB028). A meshed ground configuration is explored in order to accomplish a 50% conductive paste reduction without disrupting the performance. The proposed tags are compared to commercially available tags as well as previously published tags in terms of read range and size. The tags in this letter present an improvement in terms of read range, gain, and area with respect to previous designs covering the ISM RFID UHF bands. Moreover, the performance of these tags is maintained in on- and off-metal conditions, achieving comparable performance and a reduction in volume of 11 482% with respect to the best tag reported.

Dielectric-loaded end-fire slot antenna with low back-lobe radiation for UHF RFID applications

In this paper two end-fire constant width slot antennas built over an FR4 substrate are presented for UHF RFID tracking systems (902-928 MHz). The antennas are fed by a CPW to slot-line transition tuned to 915 MHz. Dielectric loading is implemented as a way to reduce the half-power beamwidth (HPBW); specifically, variations in the FR4 substrate thickness and additional loading material are used to achieve a 3 dB beamwidth of 75°, which is an improvement of 55° compared with the 130° HPBW when no loading is applied. Corrugated edges provide front-to-back ratio enhancement, achieving a ratio of 17.74 dB compared to 10.7 dB with no corrugation.

3D printed on-package tripolar antennas for mitigating harsh channel conditions

A compact, 3D printed tripolar antenna operating at 2.4 GHz is presented. The antenna is designed for integration with a commercial wireless node in order to mitigate multipath and depolarization channel effects that could exist in many machine-to-machine deployments. The antenna substrate is fabricated with fused deposition modeling and the conductive layers by micro-dispensing silver paste. A median channel loss reduction of 4.3 dB is achieved in a Rayleigh fading environment using selection diversity.

3D printed multilayer mm-wave dielectric rod antenna with enhanced gain

A multilayer dielectric rod antenna (DRA) design is proposed for mm-wave applications. The multilayer DRA is formed by a medium permittivity dielectric rod core encased by a low permittivity cladding to increase the peak gain. The antenna is fabricated using fused deposition modeling (FDM) of two thermoplastics; a ceramic composite material for the core and acrylonitrile butadiene styrene (ABS) for the cladding. The antenna performance is measured from 30 to 40 GHz and the results are validated using numerical simulations. The peak gain of the multilayer antenna is over 22 dBi for the entire frequency range. The effect of the cladding on the antenna performance is to increase the gain by 3–8.5 dB, with a reduction in the half power beamwidth of 22 degrees at the center frequency. The multilayer DRA design offers high gain performance, scalability to other frequency ranges and low-cost fabrication.

Additive manufactured tripolar antenna system for link improvement in high multipath environments

A 2.4 GHz single-piece additive manufactured tripolar antenna system is presented for integration with a commercially available wireless node. The antenna is 3D-printed using fused deposition modeling of ABS plastic and micro-dispensing of silver paste. Performance is evaluated in anechoic and highly reflective environments achieving a return loss greater than 15 dB at the desired frequency of operation and median and 1% link margin improvements through selection diversity of 4 dB and 11 dB, respectively.