Martin Wiessflecker

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 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.

An electro-magnetic energy harvester with 190nW idle mode power consumption for wireless sensor nodes

To increase the operating range and applicability of remotely powered devices an electro-magnetic energy harvester is developed in a 0.13 µm low cost CMOS technology. The presented system 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. The chip includes an ultra low power control unit and consumes only 190 nW in idle mode. The input sensitivity is −19.7 dBm.

A sub 1V self clocked switched capacitor bandgap reference with a current consumption of 180nA

This paper presents a bandgap reference capable of operating at supply voltages below 1V. In contrast to the vast majority of bandgap circuits the multiplication of the proportional to absolute temperature voltage is done by a switched capacitor network. Thus a reduced chip area is achieved. As a clock is needed for the switching, a relaxation oscillator is deeply integrated into the circuit. Combined the circuits provide a continuous sub bandgap voltage reference output of 615mV and a clock signal with a frequency of roughly 53kHz. The overall current consumption is 180nA at room temperature. The circuit is developed in a 130nm CMOS technology and occupies an active area of 0.0132mm2.

An 11 bit SAR ADC combining a split capacitor array with a resistive ladder and a configurable noise time domain comparator

This paper presents a successive approximation analog to digital converter with a configurable resolution of 8 or 11 bit. The resolutions are achieved by combining an 8 bit split capacitor array with a 3 bit resistive ladder allowing for a simpler layout and good power efficiency. Configurable buffers are included and enable a wide range of operation frequencies. Sample rates between 300S/s and 80kS/s were tested where at the lower frequency a total current consumption of just 8.4nA was measured. A configurable time domain comparator is employed to adapt the noise requirement to the desired resolution. The circuit is developed in a 130nm CMOS technology and occupies an active area of 0.0664mm2.

Measured wideband near-field characteristics of an UWB RFID tag with On-Chip Antenna

The combination of UWB Impulse Radio with RFID technology is proposed, implemented and analysed in this paper. For future RFID technologies, inexpensive and power efficient transceivers on the tag side are necessary for the application of Smart Dust and the Internet of Things. Therefore, we have designed and manufactured two silicon prototypes of a reconfigurable frontend of an UWB impulse radio transmitter with a total size of 1×1.3mm2. This includes an On-Chip Antenna which is manufactured in a standard CMOS. The centre frequency and the bandwidth of the radiated pulse are controllable as well as the data rate of the modulated signal. The embedded voltage controlled oscillator allows the characterisation of the On-Chip Antennas without the need of any external RF feeding structure. We emphasize this issue because RF feeding structures are inadequate for On-Chip Antenna measurements; they interfere heavily with the device under test. With this prototype we are able to perform antenna and communication characterisation measurements towards passive ultra wideband RFID tags.

Bandwidth reconfigurable UWB RFID tag with on-chip antenna

Inexpensive and power efficient transmitters are essential in tiny RFID tags or wireless sensors. We manufactured a CMOS UWB impulse radio transmitter which is connected to an on-chip antenna. The overall size of the tiny grain is 1×1.3 mm2, and is developed in a standard CMOS process. In this paper we show simulations and measurements of our active reconfigurable bandwidth UWB transmitter. As well as the reconfigurable bandwidth, the center frequency of the radiated pulse are adjustable. We compare the measured current consumptions of a continuous wave and the pulse amplitude modulated signals, both created by the active driven circuit. This shows the feasibility of UWB Impulse Radio in asymmetric communication link scenarios, where most of the implementation complexity can be moved to the reader station (away from the RFID tag).

A 2-pin input multi frequency power scavenging unit for wireless sensor nodes and RFID tags

This paper presents a multi frequency power scavenging unit dedicated but not exclusively designed for supplying RFID transponders and wireless sensor nodes. The power scavenging unit converts the incoming AC power into DC power (from 1MHz up to 2.45GHz). The circuit is used in a fully-passive multi frequency RFID transponder according to the EPC HF and EPC Class 1 Gen 2 UHF standard and is developed in a 0.13 µm low cost CMOS technology. A new concept is utilized to combine a balanced HF and an unbalanced UHF frontend to harvest energy from the magnetic or electro-magnetic field.

An ultra-low power voltage regulator for wireless sensor nodes

This paper presents an ultra-low power voltage regulator used for low power wireless sensor nodes. As the input conditions for these types of regulators can be quite different in terms of voltage range and transient speed, the introduced architecture is designed to be almost insensitive to these variations. Even if the pass device is formed by an NMOS transistor, low-dropout operation is possible by the utilization of a charge pump. The focus is on reducing the energy consumption of the regulator while keeping the robustness high. The regulator does not need an external compensation device. The circuit, implemented in a 0.13 µm CMOS process, generates the supply voltage for an ultra-low power temperature sensor and an ADC. Implementation and experimental results are discussed.