Hyoung-Hwan Roh

Extending the Interrogation Range of a Passive UHF RFID System With an External Continuous Wave Transmitter

This paper introduces an interrogation enhancer (IE) as an external system that boosts a reader continuous wave (CW) with its auxiliary CW. The boosted reader CW powers the backscatters from a passive ultrahigh frequency radio frequency identification (UHF RFID) tag to reach the reader in extended range. The system performance is verified according to the measured ranges in practical tests. The IE permits the reader to successfully interrogate the tag in tripled or doubled range (e.g., 80-290 and 182-370 cm). The measurement results imply that the IE can be used for readers that may not transmit enough CW due to the local regulation or its limited battery capacity.

TX Leakage Cancellation via a Micro Controller and High TX-to-RX Isolations Covering an UHF RFID Frequency Band of 908–914 MHz

A transmitter (TX) leakage cancellation scheme using a micro controller (MCU) is introduced. This letter highlights an adaptive anti-leakage signal generation via an MCU, which plays the key role in reducing the TX leakage signal level. High transmitter-to-receiver (TX-to-RX) isolation is verified with measurement results.

Multipath fading measurement on the circularly propagated UHF RFID reader antennas in a practical area

In this paper, the effect of the Rician fading along the travel distance is studied, and practical measurement results are presented. Signal distortions have been can be detected as the travel distance between two antennas increases. The null points of an observed field are regarded as inter-symbol intersymbol interference from one RFID reader that will affect affects another neighboring RFID reader using an identical frequency channel. The results are shown and are discussed, compared.

A common gate low noise amplifier with high linearity over UHF RFID bands

A CMOS common gate LNA with high linearity over UHF mobile RFID bands is presented. A common gate configuration applied to design the proposed LNA overall leads to high linearity and wide band characteristics. Proposed LNA is fabricated with 0.35 mum (one poly, four metals) CMOS manufacturing technology. The proposed LNA shows 3.2 dB noise figure, 13.4 dB voltage gain with 1.4 dBm P1 dB.

Differential Colpitts VCO for Enhancing Transceiver Performance in Specified UHF Mobile RFID Environment Conditions

In this paper, we introduce a differential Colpitts voltage-controlled oscillator (VCO), performing a signal oscillation with low phase noise. The proposed VCO is a part of our RF integrated circuit (IC) transceiver design project; some transceiver components are also introduced. VCO performance is verified both in simulation and practical measurement using the proposed RF IC transceiver, communicating with a commercial passive UHF RF identification tag in a small-scale area. The measured phase-noise level at the frequency divider output port is nearly -106 and -135 dBc/Hz at 40-kHz and 1-MHz offset, respectively. A good figure-of-merit of 1.93 dB is obtained. The paper also highlights some important components [e.g., phase-locked loop, low-noise amplifier, dc offset canceller (DCOC)], and their performance. We configure the reader system, which consists of the proposed transceiver on board and a patch antenna, to use frequency hopping in 15 channels at a 200-kHz interval. The transceiver power amplifier supports 22 dBm of power. Configuring the interrogation range to 1 m, we measure received backscatters at the DCOC output port (the regenerated tag data level is 8 mV). Finally, we verify satisfactory states of the tag data process in the receiver.

A design of Balun for UHF mobile RFID system

Mobile RFID system has been obtained much attention since modern trends in wireless communication technologies based on the Ubiquitous Networks. Among many components, Balun act as a converter which convert common mode signal to differential mode signal. There are two type of Balun, active type and passive type. Active Balun act good noise performance in entire communication system, but their linearity is limited by supply voltage. In this paper, we propose passive Balun implemented by IPD technology. Because Large power of TX CW compared to Tag reflecting signal leakages to RX signal path, so their linearity (especially 1 dB-compression point) is very important issue, and read range of Mobile RFID is not exceeding 2 m, so Tag reflected signal power is big compared to input thermal noise power. Besides we implement the Balun using IPD process, we can make entire system including RFID RF front-end chip and Balun into the Single chip. So we finally gained much smaller full-chip package.

Tx-Leakage Signal Blocking System in RFID System

Rx and Tx signal use same band in RFID. Then RFID system is not used duplexer and used coupler. RFID system have problem about Rx part to Tx leakage signal because that Rx signal port is Tx signal port`s Isolation port. We proposal using phase shifter Tx leakage signal decrease than other RFID system. It is same signal Tx signal port`s coupling port and isolation port signal except amplitude and phase. So if make coupling signal and isolation signal is in all same signal. We cancel Tx leakage signal used coupling port. And verification about ADS2006.

Design of Regulated Low Phase Noise Colpitts VCO for UHF Band Mobile RFID System

A regulated low phase noise differential colpitts VCO(Voltage Controlled Oscillator) for mobile RFID system is presented. The differential colpitts VCO meets the dense reader environment specifications. The VCO use a technology and achieves tuning range . Measuring 910 MHz frequency divider output, phase noise performance is -106 dBcMz and -135dBc/Hz at 40 kHz and 1MHz offset, respectively. 5-bit digital coarse-tuning and accumulation type MOS varactors allow for 28.2% tuning range, which is required to cover the LO frequency range of a UHF Mobile RFID system, Optimum design techniques ensure low VCO gain(