RFID tag search system which is used to find specific tags has many applications such as inventory management, supply chain, and search for books in the library. Recently, secure serverless search protocols using mobile readers are proposed in the environment where a persistent connection between mobile readers and a backend server cannot be guaranteed. However, the protocols are insecure against replay attacks and breach the privacy of mobile reader holders. In this paper, we point out the vulnerabilities of the previous protocols and propose an RFID tag search protocol which protects the privacy of mobile reader holders. Our protocol is secure against all known major attacks in RFID systems.
In this paper, we propose new symmetric cost functions for global stereo methods. We first present a symmetric data cost function for the likelihood and then propose a symmetric discontinuity cost function for the prior in the MRF model for stereo. In defining cost function, both the reference image and the target image are taken into account to improve performance without modeling half-occluded pixels explicitly. The performance improvement of stereo matching due to the proposed symmetric cost functions is verified by applying the proposed symmetric cost functions to the belief propagation (BP) based stereo method.
A planar folded dipole antenna suitable for WLAN and WiMAX applications is presented. By properly using a pair of multi-branch strips in the radiator, the proposed antenna with a small size of only 35(L) × 4(W)mm2 is capable of achieving dual-band operation about 2.35-2.51GHz and 4.82-6.22GHz. Moreover, the resonant frequencies of the antenna can be flexibly adjusted with various strip lengths. Experimental results show that the proposed design behaves not only good omnidirectional coverage but also stable gain variation across the operating bands. With a compact size, the proposed folded dipole antenna is thus satisfactory for integration with an access point as a transmitting antenna for WLAN/WiMAX operations.
This paper presents a novel Parallel-Coupled Microstrip Line (PCML) bandpass filter by etching of some slot resonators on the strip for suppressing the first spurious response. These slots perform a serious LC resonance property in certain frequency and suppress the spurious signals. Slot on the strip that is called Defected Microstrip Structure (DMS). The DMS interconnection disturbs the current distribution only across the strip, thereby giving a modified microstrip line with certain stop band and slow-wave characteristics. The measured results show a satisfactory rejection level more than 30dB at first spurious passband without affecting the passband response.
The high-speed downlink packet access (HSDPA) system can effectively support real-time voice services if the HS-SCCH-less feature is adopted in the 3GPP Release 7 standard. In this paper, we point out that the feature only offers a limited statistical multiplexing capability and it also causes serious power consumption at the user equipment. This paper proposes an HSDPA scheduling operation that utilizes the entire code space and considers the packet generation pattern of voice services.
A fully integrated system-in-package (SiP) for UHF (860-960MHz) RFID mobile reader is presented. The SiP is made up of an UHF transceiver, a power amplifier (PA), and two baluns. The UHF transceiver was designed in TSMC 0.18µm Si CMOS and the PA was developed with InGaP/GaAs hetero-junction-bipolar transistor (HBT) technology. The transceiver IC is fully integrated for mobile UHF RFID applications and the PA has high efficiency and linearity with 24dBm output power for wireless RFID communications over a distance of 1m. The total size of the SiP module is 11mm × 11mm. The measured data show a transmitter gain of 19.2dB, total current of 253mA and adjacent channel power ratio (ACPR) of -41.8dBc with the second harmonic performance of -57.6dBc. Also, TX-RX leakage was reduced by careful power amplifier and board designs in small SIP module implementation.
We propose a simple method for predicting the characteristics of Frequency Selective Surface (FSS) radome using an equivalent circuit model. The required material properties, such as the permittivity and permeability of the FSS, were extracted from a FSS equivalent circuit model using a transmission and reflection method. These parameters were then used to calculate the transmission characteristics of FSS radome. We designed a sandwich radome using a square loop FSS for a 23GHz band application. In order to demonstrate the validity of our approach, we also performed a simulation to obtain the characteristics of the FSS radome using commercial full-wave software. The results from the two approaches are in good agreement. The method proposed herein could be used for the simple and rapid calculation of the design and fabrication of a FSS radome. The FSS radome is that a square loop FSS that has a stop band at 23GHz is insulated between two dielectric materials. A simple analysis of a FSS radome requires the material constants, the permittivity and permeability of the square loop FSS, which we extracted using transmission/reflection. Using the material constants derived from a FSS equivalent circuit model, the characteristics of the FSS radome were calculated for a simple 2-D case. The results were verified using a commercial full-wave three-dimensional electromagnetic wave simulator. The resulting characteristics of the FSS radome agreed with those obtained using a full-wave simulation. We show herein that the characteristics of a FSS radome can be analyzed and predicted with relative ease using an approximate FSS to achieve a simple 2-D construction. Our method can be applied to the analysis of FSS radome for use with various communication systems and electrical instruments.
A high-speed capacitance difference-to-sum ratio measurement circuit is presented for differential capacitance transducers. It consists of a switched-capacitor input stage, two sample-and-hold (S/H) circuits followed by voltage-to-current (V/I) converters, and a current-ratio-controlled relaxation oscillator. This circuit offers a square-wave output whose oscillation period is directly proportional to the capacitance difference-to-sum ratio of the transducers. A prototype circuit built using discrete components exhibits conversion sensitivity (period per unit capacitance difference-to-sum ratio) amounting to 400µs and linearity error as low as 0.037%. The maximum conversion time is about 160µs when the capacitance difference-to-sum ratio is 0.4.
Handsets with metal frame, which are very popular recently, cause higher SAR value due to current leakage into the metal frame. We propose a new design to reduce the SAR (Specific Absorption Rate) without degrading antenna performance which is represented by TRP (Total Radiated Power). We place the contact points between PCB GND and the metal frame at the length of λ/2. This distributes the current over wider area and hence reduces SAR. Besides, we extend the PCB GND around the antenna feed to reduce the high current density in the area. Our experiment shows 32% reduction in SAR without degrading TRP.
We report on the high-power lasing characteristics of a large area bottom-emitting vertical-cavity surface-emitting laser (VCSEL). There have been difficulties in uniform current injection for large area VCSELs, which are caused by the band discontinuity at the interface between AlAs and GaAs of the n-type Distributed Bragg Reflector (DBR). We have reported the n-type DBR using a graded composition interface of 20nm thick suppresses the crowding of current to the edge of emitting area and improves external efficiency . The highest peak pulsed power of over 49W was achieved by a five-quantum-well VCSEL with a current aperture diameter of 200µm.