Passive Antenna Research Articles

Design of an Ultra-Compact UHF Passive RFID Tag Antenna for a Medical Sample Tube

In this letter, a small-sized ultra-high frequency (UHF) RFID tag antenna for a medical sample tube is proposed. The RFID tag antenna is designed and fabricated based on the circular loop antenna used in the UHF band (Korea standard, 917 MHz to 923.5 MHz). The tag antenna size is reduced using a circular meander stub. The antenna has a physical size of 8 mm, which is about λ/40 in electrical length. The proposed tag antenna is molded into a medical sample and multitag identification is performed.

Open loop, auto reversing liquid nitrogen circulation thermal system for thermo vacuum chamber

In a thermo vacuum chamber, attaining and controlling low and high temperatures (-100 Deg. C to +120 Deg. C) is a very important task. This paper describes the development of "Open loop, auto reversing liquid nitrogen based thermal system". System specifications, features, open loop auto reversing system, liquid nitrogen flow paths etc. are discussed in this paper. This thermal system consists of solenoid operated cryogenic valves, double embossed thermal plate (shroud), heating elements, temperature sensors and PLC. Bulky items like blowers, heating chambers, liquid nitrogen injection chambers, huge pipe lines and valves were not used. This entire thermal system is very simple to operate and PLC based, fully auto system with auto tuned to given set temperatures. This system requires a very nominal amount of liquid nitrogen (approx. 80 liters / hour) while conducting thermo vacuum tests. This system was integrated to 1.2m dia thermo vacuum chamber, as a part of its augmentation, to conduct extreme temperature cycling tests on passive antenna reflectors of satellites.

Passive and Active Reconfigurable Scan-Beam Hollow Patch Reflectarray Antennas

The design concept of passive and active reconfigurable reflectarray antennas has been proposed and tested. The antenna elements in the array are identical hollowed patches. In the first phase of study the slots are loaded with a SMD capacitor to set the required phase shift needed for array implementation. Simulations show promising results. Mounting a SMD capacitor in such a configuration can be considered as the first step in using capacitive loading on a slotted patch for active microstrip reflectarrays. It is shown that by adjusting the capacitance values it is possible to scan the beam. In the second phase, the patch elements are loaded with active varactor-diode device which its reflected phase can be varied. This phase alteration is based on the variation of the diode capacitance which can be achieved by varying the biasing voltage of the active varactor device. In latter approach by activating these varactor devices, the phase of each antenna element in the array configuration can be adopted dynamically and consequently, its beam direction can be reconfigured. The reflectarrays incorporating passive and active elements have been built and tested at 7.0 GHz and 6.0 GHz, respectively. The performance of the proposed reconfigurable antennas is excellent, and there is good agreement between the theoretical and measurement results which pioneers design of arbitrarily reconfigurable antennas.

The use of civilian-type GPS receivers by the military and their vulnerability to jamming

We considered the impact of external influences on a GPS receiver and how these influences affect the capabilities of civilian-type GPS receivers. A standard commercial radio frequency signal generator and passive GPS antenna were used to test the sensitivity of GPS to intentional jamming; the possible effects of the terrain on the propagation of the jamming signal were also tested. It was found that the high sensitivity of GPS receivers and the low strength level of GPS satellite signals combine to make GPS receivers very vulnerable to intentional jamming or unintentional radio frequency interference. Terrain undulation was used to shield GPS antennas from the direct line-of-sight of the jamming antenna and this indicated that terrain characteristics can be used to mitigate the effects of jamming. These results illuminate the vulnerability of civilian-type GPS receivers to the possibility and the ease of disablement and establish the foundation for future work.

Coupling-Feed Circularly Polarized RFID Tag Antenna Mountable on Metallic Surface

A square patch passive RFID tag antenna designed for UHF band is presented in this article. To achieve compact size and circular polarization (CP) radiation, the square patch is embedded with a cross slot, while an L-shaped open-end microstrip line linked to a tag-chip and terminated by a shorting pin is capacitively coupled to the patch. By selecting an appropriate length for the microstrip line and its coupling distance with the radiating element, easy control on the input impedance of the proposed tag antenna which leads to excellent impedance matching is achieved. The measured 10-dB return-loss bandwidth of the tag antenna is 50 MHz (904-954 MHz), while its 3-dB axial-ratio bandwidth is 6 MHz (922-928 MHz). Further experiment shows that the tag antenna can provide better reading range when mounted on a metallic surface.

Silk‐Based Conformal, Adhesive, Edible Food Sensors

An array of passive metamaterial antennas fabricated on all protein-based silk substrates were conformally transferred and adhered to the surface of an apple. This process allows the opportunity for intimate contact of micro- and nanostructures that can probe, and accordingly monitor changes in, their surrounding environment. This provides in situ monitoring of food quality. It is to be noted that this type of sensor consists of all edible and biodegradable components, holding utility and potential relevance for healthcare and food/consumer products and markets.

Design of a VHF/UHF/L-Band Low-Power Active Antenna for Mobile Handsets

A small triple-band receiving active antenna for VHF, UHF, and L-band broadcasting that can be used for mobile handsets is presented. This antenna consists of a small single passive helical antenna and a triple-band low noise amplifier (LNA). The design procedure of this antenna, in which the passive antenna shows very different impedances at each band, is also presented. Furthermore, it is demonstrated that the proposed configuration can be used as a triple-band receiving active antenna for VHF (174-216 MHz), UHF (470-806 MHz), and L-band (1450-1492 MHz).

A Reconfigurable Passive UHF Reader Loop Antenna for Near-Field and Far-Field RFID Applications

This letter presents a passive UHF printed loop antenna with left-handed loading. The RFID reader antenna can work at near- and far-field operation within the European UHF (865-868 MHz) band. The operation frequency and radiation properties can be modified by employing varactor diodes. Also, the antenna can work in the near-field region having a flat magnetic distribution in the interrogation zone. A comparative study with other passive RFID reader conventional antennas shows that the left-handed loop achieves stronger near H-field with good impedance matching. Design details, simulated results, and a fabricated prototype are presented. The concept significantly extends the design degrees of freedom for RFID antennas.

DETERMINATION OF DIELECTRIC PROPERTY OF CONSTRUCTION MATERIAL PRODUCTS USING A NOVEL RFID SENSOR

This paper presents a concept, by which radio frequency (RF) tags are employed as remotely read dielectric-property sensors to determine qualities of some construction material products (CMPs); e.g., light weight concrete (LWC), mortar specimens and concrete. Using the dependency of the read range of the passive RF identiflcation (RFID) sensor system on the electromagnetic properties of CMPs near or in contact with RFID tags, the qualities of CMPs can be determined through their estimated dielectric properties. Theoretical formulation is provided, and numerical simulations are performed for optimal design of passive RFID tag antennas suitable for RFID sensors and for read-range calculations. In addition, a series of measurements is performed to measure read ranges of the passive RFID sensor system for an LWC as an example of CMPs, and these measured read ranges will be processed appropriately to inversely determine the dielectric constant of the LWC under test, which in turn provides information on its qualities. It is found that the novel RFID sensor can be employed to determine the dielectric properties of the LWC under test with reasonable accuracy.

A Selective Ink Deposition Method for the Cost-Performance Optimization of Inkjet-Printed UHF RFID Tag Antennas

A selective ink deposition method is proposed for fabricating inkjet-printed passive UHF RFID tag antennas with optimized cost-performance ratios. The deposition method is based on identifying areas with high surface current densities on a given tag antenna and applying additional silver nanoparticle ink onto such areas to increase tag read range. In this paper, the proposed method is experimentally verified by utilizing the method on a small dipole tag antenna. Several ink deposition schemes are created, and their read range performances and ink consumptions are presented.

Performance of High-Permittivity Ceramic-Polymer Composite as a Substrate for UHF RFID Tag Antennas

A high-permittivity ceramic-polymer composite substrate is fabricated and proposed for its potential use in UHF RFID tags. The substrate is developed using high-permittivity Barium Titanate (BaTiO3) ceramic powder mixed with polydimethylsiloxane (PDMS) polymer. The resulting composite achieves a soft, hydrophobic, heat resistant, low loss, and flexible material with high dielectric constant. The percentage of the ceramic powder in the composite helps in achieving variable permittivity values. When this material is used as a substrate for a tag antenna, it will help the tag to be reduced in size, to conform to uneven or rough surface, and to be less vulnerable to breakage or other environmental damages. A small passive UHF RFID tag antenna is designed, fabricated, and attached to this type of composite substrate, to demonstrate the performance of this composite material.

UWB Antennas Beamforming Using Passive Time-Reversal Device

In this letter, the feasibility of a new concept of passive antenna beamformer is investigated. The main idea is to develop a (1×N)-ports device in which the weightings on output ports are applied by time-reversal operation. The control of antennas weightings is then contained in the input waveform without the need of active components or external control signals. This approach is validated experimentally by radiation pattern measurement of a four-Vivaldi-antennas array, associated to a small reverberation cell beamformer. Finally, this concept is applied to realize a passive ultrawideband (UWB) phased-array radar for target imaging.

Multiplexing passive wireless antenna sensors for multi-site crack detection andmonitoring

This paper investigates the multiplexing of unpowered wireless antenna sensors for crackmonitoring at multiple locations. Four antenna sensors were multiplexed to form two sets ofdual-antenna sensor arrays based on two multiplexing principles, namely the frequencydivision and spatial division principles. Taking advantage of frequency division, twoantenna sensors operating at different frequencies can be simultaneously interrogated. Thespatial division enables sequential interrogation of antenna sensors installed at differentlocations, even if they share the same resonant frequencies. The capability of the antennasensor array to monitor multiple crack growth in a fatigue specimen was characterized.Multiplexing antenna sensors enables us to track sub-millimeter crack growth over a largearea.

The influence of suppression of side lobes on the range of passive sonars

This paper presents a universal procedure of the de-embedding of mathematical functions of ratios of maximal ranges depending on the level of suppression of side lobes at the directivity pattern of passive sonar antenna. This dependence is founded on the specially made and named as “idealized model” of measured directivity pattern of a sonar antenna with the model of elliptical cross section of the main lattice perpendicular on acoustic axes. Using the given mathematical expressions of directivity index and dependence of suppression of side lobes at the mentioned idealized model of directivity pattern characteristics with equations of hydrolocations and their conditions, there are relatively simple expressions of ratio of maximum ranges in form of defined function mz. Using the given mathematical function mz there is possible to control the value of all important parameters for the de-embedding of the sonar ranges in its specification. In accordance with given model, there are point out the importance of ratio of ranges of maximum value of level of suppression of side lobes at directivity pattern characteristic with elliptical cross section of main lattice of antenna. Mainly, the level of suppression of side lobes is less than −50 dB at contemporary passive sonars today.

Secure Resource Allocation and Scheduling for OFDMA Decode-and-Forward Relay Networks

In this paper, we formulate an optimization problem for secure resource allocation and scheduling in orthogonal frequency division multiple access (OFDMA) half-duplex decode-and-forward (DF) relay assisted networks. Our problem formulation takes into account artificial noise generation to combat a passive multiple antenna eavesdropper and the effects of imperfect channel state information at the transmitter (CSIT) in slow fading. The optimization problem is solved by dual decomposition which results in a highly scalable distributed iterative resource allocation algorithm. The packet data rate, secrecy data rate, power, and subcarrier allocation policies are optimized to maximize the average secrecy outage capacity (bit/s/Hz securely and successfully delivered to the users via relays). Simulation results illustrate that our proposed distributed iterative algorithm converges to the optimal solution in a small number of iterations and guarantees a non-zero secrecy data rate for given target secrecy outage and channel outage probability requirements.

An active tri-band (AMPS/PCS/GPS) antenna with enhanced cellular-to-GPS isolation for automotive applications

The design and performance of an active tri-band antenna for automotive applications that includes the global positioning system (GPS), analog mobile phone service (AMPS), and personal communication service (PCS) is presented. For automotive emergency applications, the close proximity of the GPS and cellular antenna elements demands stringent isolation requirements on the GPS low noise amplifier (LNA) design to prevent interference to GPS during cellular transmissions. The GPS low-noise amplifier designed in this letter exhibited a power gain of 26.4 dB, an out of band rejection in excess of 31 dB at +/-50 MHz around the center frequency, a noise figure of 1.5 dB, a 1dB power compression of 9.7 dBm, isolation over the AMPS band in excess of 62 dB, isolation over the PCS band in excess of 48 dB, an input 3rd order intercept of −6.5 dBm and an output 3rd order intercept of 20.6 dBm while operating at 5 volts with a current draw of 20mA. In addition, the antenna patterns measured on a ground plane are presented for the active GPS antenna, AMPS passive antenna and the PCS passive antenna. © 2011 Wiley Periodicals, Inc. Microwave Opt Technol Lett, 2011; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.26117

Facilitating breakdown in noble gases at near-atmospheric pressure using antennas

Electrical breakdown in near-atmospheric pressure noble gases requires voltages that are quite high, which is undesirable for a large number of possible applications. Metallic structures (antennas) were used on the outer side of the lamp burner to enhance the electric field locally while keeping the same potential difference across the electrodes. Optical and electrical measurements were performed in an argon or xenon atmosphere at 0.3 or 0.7 bar, with 4 or 7 mm between the electrode tips. We used rod-shaped tungsten electrodes of 0.6 mm in diameter. We found that both active and passive antennas facilitate breakdown, and we demonstrated the differences between the two types and their effects on the breakdown process.

Radiation Pattern Optimization by Loaded Impedance in the Base of Passive Element

Radiation Pattern Optimization by Loaded Impedance in the Base of Passive ElementThis article deals with optimizing the radiation pattern by using two vertical middle wave antenna arrays. Optimization is achieved by adding an appropriate impedance into the base of the passive antenna radiator. The proposed solution deals with finding the best value of the loaded impedance. The final result is to achieve the most effective shape of the radiation pattern. The proposed method was finally approved by measurement on a real middle wave antenna array.

Imprinted laminate wafer-level packaging for SAW ID-tags and SAW delay line sensors

We have developed a wafer-level packaging solution for surface acoustic wave devices using imprinted dry film resist (DFR). The packaging process involves the preparation of an imprinted dry film resist that is aligned and laminated to the device wafer and requires one additional lithography step to define the package outline. Two commercial dry film solutions, SU-8 and TMMF, have been evaluated. Compared with traditional ceramic packages, no detectable RF parasitics are introduced by this packaging process. At the same time, the miniature package dimensions allow for wafer-level probing. The packaging process has the great advantage that the cavity formation does not require any sacrificial layer and no liquids, and therefore prevents contamination or stiction of the packaged device. This non-hermetic packaging process is ideal for passive antenna modules using polymer technology for low-cost SAW identification (ID)-tags or lidding in low-temperature cofired ceramic (LTCC) antenna substrates for high-performance wireless sensors. This technique is also applicable to SAW filters and duplexers for module integration in cellular phones using flip-chip mounting and hermetic overcoating.

Wire-Frame Monocone Antenna for Direction-Finding Applications on Unmanned Aerial Vehicle Platform

A detailed design for a loaded wire-frame monocone antenna for direction-finding applications on an Army UAV platform is presented. This was used to compare simulation and measurement results of radiation-pattern and gain measurements for a scaled prototype mounted on a UAV wing, using the FEKO electromagnetic-simulation software. The results indicated that this antenna design offers bandwidth and gain performance that is far superior to many other passive antenna candidates. The results also confirm the accuracy and efficiency of using FEKO for modeling candidate antennas integrated onto large-scale Army platforms.