Gerald Holweg

A Multifrequency Passive Sensing Tag With On-Chip Temperature Sensor and Off-Chip Sensor Interface Using EPC HF and UHF RFID Technology

State-of-the-art passive RFID tags are limited in terms of functionality and operating range due to the limited power that can be converted from the electromagnetic field. This is why state-of-the-art wireless sensor systems are mostly battery-based if a high operating range is required. The proposed ultralow-power on-chip sensor unit and off-chip sensor interface which provides enough energy to supply various sensors with a power consumption up to the milliwatt range make it possible to remotely power the proposed RFID tag and use it as wireless sensor node. Equipping sensor nodes with RFID functionality not only enables identification and logistic applications but also an easy integration of the sensing tag into existing RFID systems. Exploiting the different characteristics of HF and UHF RFID systems, namely the large operating range in UHF and the high available power in HF, increases the flexibility and applicability of wireless sensor nodes. This paper presents a remotely powered multifrequency sensing tag according to the EPC HF and EPC Class 1 Gen 2 UHF standard developed in a 0.13-μm low-cost CMOS process. Input powers of -10.3 or -7.9 dBm at a frequency of 900 MHz are necessary to operate the sensing tag with activated on-chip sensor unit or off-chip sensor interface, respectively.

An Electro-Magnetic Energy Harvesting System With 190 nW Idle Mode Power Consumption for a BAW Based Wireless Sensor Node

State-of-the-art wireless sensor nodes are mostly supplied by batteries. Such systems have the disadvantage that they are not maintenance free because of the limited lifetime of batteries. Instead, wireless sensor nodes or related devices can be remotely powered. To increase the operating range and applicability of these remotely powered devices an electro-magnetic energy harvester iPs developed in a 0.13 μ m low cost CMOS technology. This paper presents an energy harvesting system that converts RF power to DC power to supply wireless sensor nodes, active transmitters or related systems with a power consumption up to the mW range. This energy harvesting system is used to power a wireless sensor node from the 900 MHz RF field. The wireless sensor node includes an on-chip temperature sensor and a bulk acoustic wave (BAW) based transmitter. The BAW resonator reduces the startup time of the transmitter to about 2 μs which reduces the amount of energy needed in one transmission cycle. The maximum output power of the transmitter is 5.4 dBm. The chip contains an ultra-low-power control unit and consumes only 190 nW in idle mode. The required input power is -19.7 dBm.

A Triple-Band Passive RFID Tag

This paper presents a broadband analog interface in 0.12 mum CMOS without a Schottky Diode process-option, which powers the chip from 1MHz to 2.45GHz and communicates with EPC UHF and HF. To profit from the application benifit of both13.5613MHz HF RFID systems used in identification and 860 to 960MHz UHF RFID systems used in supply chain applications, two frequency selective tags or one broadband chip with one antenna are necessary.

Impact of the Local Oscillator on Baseband Processing in RFID Transponder

The ultra high frequency (UHF) passive radio frequency identification (RFID) technology has gained popularity, because there are improvements regarding read distance and operational reliability. This features and the low-cost passive technology suppose to play an important role in the field of automatic identification and ubiquitous computing. The operation frequency of the UHF transponder (tag) is between 860 MHz-960 MHz. The performance of the tag is limited by physical reasons such as available power for the baseband processing. The baseband functions are specified in EPCtrade class 1 generation 2 UHF protocol, in which a local oscillator generates the clock for the baseband processor. This paper analyzes the influence of the local oscillator to the communication in the baseband.

Ultra low power oscillator for UHF RFID transponder

This paper presents a realization of an ultra low power ring oscillator in 0.14 mum bulk CMOS technology. The application field for this oscillator is the clock generation for a baseband processor of a passive ultra high frequency (UHF) radio frequency identification (RFID) transponder. This technology will play an important role in the field of automatic identification. The paper contains simulation and measurement results for tuning range, cycle to cycle jitter and power consumption with regarding to the control current and supply voltage. The circuit was designed and fabricated by using 0.14 mum bulk CMOS technology.

Highly efficient multistandard RFIDs enabling passive wireless sensing

This paper presents a highly efficient analog multistandard frontend for passive sensor-enabled RFID transponders. The CMOS only frontend is implemented in a 0.13 µm CMOS technology. The measured overall RF-to-DC power conversion efficiency of the analog frontend for a DC output power of 10 µW is about 7% and the maximum efficiency is about 15% at UHF. An implemented sensor interface consumes 1.4 µA at 1V supply. This interface contains an ultra low-power successive approximation ADC that uses the capacitive charge redistribution technique for its integrated DAC.

A 7.9μW remotely powered addressed sensor node using EPC HF and UHF RFID technology with −10.3dBm sensitivity

The combination of remote powering and wireless data transmission enables the monitoring of data in harsh and difficultly accessible environments, where batteries cannot be replaced or where it is not possible to supply the sensor system by wire or by thermal or photovoltaic energy harvesting. Equipping sensor nodes with RFID functionality not only enables identification and logistic applications but also an easy integration of the sensing tag into existing RFID systems. Exploiting the different characteristics of HF and UHF RFID systems, namely the large operating range in UHF and the high available power in H F, increases the flexibility of wireless sensor nodes.

Energy-Efficient Wireless Sensing Using a Generic ADC Sensor Interface Within a Passive Multi-Standard RFID Transponder

A successive approximation analog-to-digital converter (ADC) is presented, whose components make use of effective ultralow-power techniques to enable wireless sensing with passive and semi-passive sensor nodes. Compared with prior publications, new layout enhancements were applied to the capacitive array of the integrated digital-to-analog converter (DAC) to achieve less distortion caused by mismatch. In addition, it is shown that the digital circuit parts consume most of the available energy. Therefore, digital near-threshold operation is proposed to minimize their consumption. The applicability of the ADC is demonstrated in a UHF RFID system. Within this system, it is applied as a core of a sensor interface integrated into a passive multistandard RFID transponder. The EPC protocol used for communication ensures the compatibility with standard UHF RFID readers while the sensor data is acquired using custom commands. Single sensor readings are demonstrated as well as continuous sensor data transmission without further interaction of the reader device. A stable transponder reading distance of 6.5 m is achieved. The integrated ADC consumes only 525 nA at 40 kSps and 0.9-V supply voltage. Under these conditions, an ENOB of 7.23 is achieved and thus a FOM of 79 fJ/conversion-step.

Wireless sensing by means of passive multistandard RFID tags

This paper presents a generic sensor interface built in a 0.13 µm CMOS process capable of being applied in passive HF & UHF RFID Tags without any additional power supply. The sensor interface contains an ultra low-power successive approximation ADC that uses the capacitive charge redistribution technique for its integrated DAC. An on-chip temperature sensor and up to three additional sensor signals can be applied to the ADC. A conversion rate of 100 kSps is reached while consuming less than 1.5 µA at 0.9 Volt supply voltage.

Analyses and design of low power clock generators for RFID TAGs

This paper introduces a new clock generation concept with a PLL for HF RFID systems. Low power consumption of 1.9 muW and a good decoupling against power supply and bias variations are necessary to reach HF RFID timing and energy performance requirements. All presented oscillator topologies can be used in UHF EPCglobal class1 gen2 RFID systems as local oscillator with a minimum frequency of 1.92 MHz. For all oscillators the PSR, power consumption and temperature drift are simulated and partly measured. In the CTS1 project a new VCO and local oscillator concept was developed and manufactured on an Infineon 120 nm CMOS test-chip. The PLL is simulated with the same process technology.