Ibrahim Tekin

RFID Coverage Extension Using Microstrip-Patch Antenna Array [Wireless Corner]

In this paper, a UHF-band 2 times 2 microstrip phased-array antenna is designed and implemented to extend the coverage of an RFID reader system. The phased-array antenna has four microstrip-patch antennas, three Wilkinson power dividers, and a transmission-line phase shifter. These are printed on a dielectric substrate with a dielectric constant of 4.5. The array has dimensions of 34 cm times 45 cm, operating at a frequency of 867 MHz, as specified in RFID Gen2 protocol European standards. The phased-array antenna has a measured directivity of 12.1 dB, and the main-beam direction can be steered to angles of plusmn 40deg, with a HPBW of 90deg. The phased-array antenna is used as the receiving antenna in a commercial reader system. Experimental results indicate that the coverage of the RFID system with the phased-array antenna is superior to the coverage with a conventional broader-beamwidth microstrip-patch antenna. The proposed system can also be used for a wireless positioning system.

Design of an RFID-based Manufacturing Monitoring and Analysis System

Radio frequency identification (RFID) technology has become an important driver in the production and logistics activities of todays information-based industries and economies. With the innovative developments in information and communication technologies, companies focus more on how these changes can be implemented and promoted in order to improve their value-added processes. This paper presents one such implementation approach for the monitoring and analysis of a discrete manufacturing environment using the RFID technology. Our aim is to bridge the gap between the physical flow of materials on the shop floor and manufacturing information and execution systems by allowing a rapid development and deployment of an RFID-based manufacturing automation solution.

Ultra-wideband n-bit digitally tunable pulse generator

This paper presents a low-cost ultra-wideband (UWB) pulse generator that can vary the pulse duration digitally by using a step recovery diode (SRD), microstrip transmission lines and PIN diodes. First, a sharp edge is generated by using a SRD. Through the use of transmission lines and the PIN diodes, a pulse is formed from the sharp edge. Based on the number of transmission lines (N), the duration of the pulse can be varied in 2/sup N/ steps. The UWB pulse generator circuit is implemented on FR-4 substrate using microstrip line technology and UWB pulses with durations of 550 to 1750 psec are measured.

Performance comparison of state-of-the-art heterojunction bipolar devices (HBT) based on AlGaAs/GaAs, Si/SiGe and InGaAs/InP

Abstract This paper presents a comprehensive comparison of three state-of-the-art heterojunction bipolar transistors (HBTs); the AlGaAs/GaAs HBT, the Si/SiGe HBT and the InGaAs/InP HBT. Our aim in this paper is to find the potentials and limitations of these devices and analyze them under common Figure of Merit (FOM) definitions as well as to make a meaningful comparison which is necessary for a technology choice especially in RF-circuit and system level applications such as power amplifier, low noise amplifier circuits and transceiver/receiver systems. Simulation of an HBT device with an HBT model instead of traditional BJT models is also presented for the AlGaAs/GaAs HBT. To the best of our knowledge, this work covers the most extensive FOM analysis for these devices such as I – V behavior, stability, power gain analysis, characteristic frequencies and minimum noise figure. DC and bias point simulations of the devices are performed using Agilents ADS design tool and a comparison is given for a wide range of FOM specifications. Based on our literature survey and simulation results, we have concluded that GaAs based HBTs are suitable for high-power applications due to their high-breakdown voltages, SiGe based HBTs are promising for low noise applications due to their low noise figures and InP will be the choice if very high-data rates is of primary importance since InP based HBT transistors have superior material properties leading to Terahertz frequency operation.

Method of moments solution for a wire attached to an arbitrary faceted surface

This paper presents a method of moments (MoM) solution to the problem of a wire attached to an arbitrary faceted surface by developing a special attachment basis function, which enforces continuity of current at the wire/plate junction and also models the nearly singular-plate surface-current density in the vicinity of the attachment point. This new attachment mode contains a nonplanar disk, which conforms to the faceted surface in the vicinity of the attachment point and has current that spreads uniformly from the attachment point. It is applicable near or at the edges and corners of the facets.

Microstrip Patch Antenna for RFID Applications

UHF band microstrip patch antenna for RFID reader with a center frequency of 867 MHz, as specified in Gen2 protocol European standards, is designed. Patch antenna is printed on FR4 material with dielectric constant of 4.55 with dimensions of 10times12 cm, from measurements at 867 MHz S11 is observed to be -22dB with an input impedance of 42.4 Omega.

2D Indoor positioning system using GPS signals

In this paper, we present an indoor positioning system based on GPS repeaters. Each repeater consists of a directional antenna for receiving a non-overlapping set of GPS satellites, a LNA and a power amplifier for compensating the antenna and cable losses, and a transmitting antenna for re-radiating the amplified GPS signals. The proposed system has been shown to be very successful for 1D positioning using a set of two repeaters. Similarly, successful results have been obtained for 2D positioning using three repeaters.

SiGe Process Integrated On-Chip Dipole Antenna on Finite-Size Ground Plane

This letter investigates the effect of a finite-size ground plane on the radiation pattern and reflection coefficient of a SiGe process integrated on-chip antenna. A flat 77-GHz on-chip strip dipole antenna integrated with a lumped LC balun circuit is designed and implemented. For increased directivity, the etched silicon substrate is placed on a metal ground plate. The on-chip antenna with the LC balun circuit is connected to GSG pads for measurement purposes. The antenna is well matched at the original resonance frequency band with 7-12 GHz impedance bandwidth and 4 dBi measured gain at 85 GHz.

Reconfigurable dual band microstrip patch antenna for Software Defined Radio applications

In this paper, a reconfigurable microstrip patch antenna with RF pin diode switches is implemented for dual band of 2.4 GHz and 5.6 GHz Software Defined Radio (SDR) applications. For the dual band SDR system, the use of a single antenna with a wide bandwidth to cover both of the bands can be limiting for low power level signal applications due to wideband noise. A reconfigurable nested microstrip patch antenna is designed on a Rogers 5880 RT/DUROID substrate which is fed by a coaxial probe from the back side of the grounded substrate. RF switching circuitry involves four RF pin diodes at each side of the inner patch. The dual bands of 2.4 GHz and 5.6 GHz frequency operation can be simply obtained by switching the PIN diodes on and off. The antenna is well matched and achieves approximately 7 dBi simulated gain at both frequency bands. Simulation results show that the nested patch antenna is suitable for dual band SDR applications.

Broadband circularly polarized antennas for UHF SATCOM

Novel circularly polarized (CP) antenna configurations derived from Moxon type antenna (bent dipole element over a ground plane) for broadband UHF SATCOM applications. A sequence of topologies starting from a single vertical element to two vertical elements of the Moxon arms, then widened strip arm elements were studied. Further, arms were widened to bowtie structures with bents at 90°. for achieving broadband operation. Bowtie elements were further split and optimized at a certain angle to achieve wider bandwidth. The logic in this evolution was to obtain highest possible gain based on Fano-Chu limits, which suggests that higher gain can be achieved in an electrically small antenna with maximized metallization in the structure that fill the volume. Circular polarization is obtained by two Moxon based cross elements that are fed through a hybrid 90° quadrature coupler. For the antennas that are prototyped, return loss S11 measurements were performed, and gains are simulated using HFSS. For the band of 225–400 MHz, antenna gain varies between 8–12 dB, and S11 is measured to be below 10 dB. Fabricated antennas coupled to a hybrid coupler yielded excellent bandwidths, low cross-polarization and low back lobes on the finite ground planes.