David Ruffieux

A 1 V 433/868 MHz 25 kb/s-FSK 2 kb/s-OOK RF transceiver SoC in standard digital 0.18 /spl mu/m CMOS

A 1 V wireless SoC embedding an RF transceiver, a sensor interface, a 6.4 MHz RISC micro-controller with an 8k instruction SRAM and a power management unit is reported. The radio supports 25 kb/s FSK and 2 kb/s OOK modulations in the 433/868 MHz bands. In the 433 MHz band, the receiver draws 2.1 mA while providing a sensitivity of -108 dBm and the transmitter draws 27.6 mA for an output power of 10.5 dBm.

Silicon Resonator Based 3.2

This paper presents an ultra-low power generic compensation scheme that is used to implement a real time clock based on an AlN-driven 1 MHz uncompensated silicon resonator achieving 3.2 μW power dissipation at 1 V and ±10 ppm frequency accuracy over a 0-50°C temperature range. It relies on the combination of fractional division and frequency interpolation for coarse and fine tuning respectively. By proper calibration and application of temperature dependent corrections, any frequency below that of the uncompensated resonator can be generated yielding programmability, resonator fabrication tolerances and temperature drift compensation without requiring a PLL. To minimize the IC area, a dual oscillator temperature measurement concept based on a ring oscillator/resistor thermal sensor was implemented yielding a resolution of 0.04°C. The IC was fabricated on a 0.18 μm 1P6M CMOS technology.

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A 150¿A/MHz DSP with two MAC/cycle instructions is integrated with a configurable 863-to-928MHz RF transceiver that yields 3.5mW in continuous reception, 2¿C per channel sampling and 40mW for 10dBm output. The SoC includes voltage converters that allow 1.0-to-1.8V or 2.7-to-3.6V primary voltage supplies. In sleep mode, it consumes 1¿A with a 32kHz crystal-based RTC running.

W Real Time Clock With

This paper presents a BAW-based transceiver targeting wireless networks for biomedical applications. The use of high-Q microelectromechanical-systems resonators brings interesting benefits to the fundamental building blocks of the frequency synthesis, receiver, and transmitter and allows achieving at the same time low-power consumption, improved phase noise, and high selectivity in the receiver and transmitter paths. In the baseband, the power consumption is minimized thanks to the use of a phase analog-to-digital converter (ADC) which directly quantizes the phase of the received signal instead of using two separate amplitude ADCs. A complete wireless node composed of the transceiver integrated circuit (IC) and a microprocessing IC, both integrated in a standard digital 0.18-μm complementary metal-oxide semiconductor technology are described and validated by measurement results. The RF carrier phase noise is -136.2 dBc/Hz at 1-MHz offset. The transmitter demonstrates 1-Mb/s Gaussian frequency-shift keying modulation at an output power of 5.4 dBm with an overall current of 35 mA, in compliance with Bluetooth and Bluetooth low energy output spectrum requirements. At the receiver, further investigations are needed to find the origins of an unexpected sensitivity of -75 dBm at 200 kb/s.

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This paper presents the fabrication steps of a MEMS package based on silicon interposer wafers with copper filled TSVs and bonded cap wafers for hermetic sealing of resonator components. All processes were performed at 200 mm wafer level. For interposer fabrication a standard process flow including silicon blind hole etching, isolation, copper filling, wafer front side redistribution, support wafer bonding, wafer thinning, and TSV backside reveal was applied. As interposer backside metallization, appropriate I/O terminals and seal ring structures were deposited by semi-additive Au and Au+Sn electro plating. Following, getter material was deposited onto the interposer wafers which were 90 μm thick and still mounted onto carrier wafers. Subsequently, the I/O terminal pads of the interposer were stud bumped and finally more than 5000 quartz resonator components were assembled onto each interposer wafer by Au-Au direct metal bonding. The cap wafer was equipped with 200 μm deep dry etched cavities and electro plated Au seal rings around them. Finally, both cap and interposer wafers were bonded together using a wafer to wafer bonder and an adapted AuSn soldering process scheme. In a last step, the carrier wafer was removed from the former front side of the interposer wafer and wafer level testing was performed. From a total of 4824 tested devices we found that more than 75 % were sealed properly under vacuum. The getter appears to be effective leading to ~0.1 mbar equivalent air pressure and cavities without getter appear to reach residual air pressure between 1-2 mbar. The used fabrication processes and final results will be discussed detailed in this manuscript.

10 ppm Frequency Accuracy

In this paper, a solution to realize local oscillators (LO) for a low power super-heterodyne receiver is presented. The first oscillator uses a bulk acoustic wave (BAW) resonator with high Q-factor. A quasi- harmonic quadrature relaxation oscillator with large tuning range is used to compensate for variations in the first oscillator and to cover the entire bandwidth for multiple channel selection.

A 1V RF SoC with an 863-to-928MHz 400kb/s radio and a 32b Dual-MAC DSP core for Wireless Sensor and Body Networks

A 0.9 V 1.2 mA fully integrated radio data system (RDS) receiver for the 88-108 MHz FM broadcasting band is presented. Requiring only a few external components (matching network, VCO inductors, loop filter components), the receiver, which has been integrated in a standard digital 0.18 /spl mu/m CMOS technology, achieves a noise figure of 5 dB and a sensitivity of -86dBm. The circuit can be configured and the RDS data retrieved via an I/sup 2/C interface so that it can very simply be used as a peripheral in any portable application. A 250 kHz low-IF architecture has been devised to minimize the power dissipation of the baseband filters and FM demodulator. The frequency synthesizer consumes 250 /spl mu/A, the RF front-end 450 /spl mu/A while providing 40 dB of gain, the baseband filter and limiters 100 /spl mu/A, and the FM and BPSK analog demodulators 300 /spl mu/A. The chip area is 3.6 mm/sup 2/.

A 2.4-GHz BAW-Based Transceiver for Wireless Body Area Networks

This paper describes the design of a temperature sensor based on integrated poly-silicon thermistors. The thermistors are incorporated in a Wien-bridge RC filter, which, in turn, is embedded in a frequency-locked loop. The loops output frequency is then determined by the filters temperature-dependent phase shift, thus realizing an energy-efficient and high resolution temperature sensor. After a 3-point calibration, the sensor achieves an inaccuracy of less than ±0.12^°C (min-max) from -40^°C to 85^°C. This translates into a frequency stability of better than ±2 ppm from -40^°C to 85^°C when the sensor is used to temperature compensate the quartz-crystal oscillator of a 32 kHz real-time clock. The 0.09 mm² sensor also achieves 2.8 mK (rms) resolution in a 32 ms conversion time while dissipating only 31 μW.

Hermetic wafer level packaging of MEMS components using through silicon via and wafer to wafer bonding technologies

This paper explores where MEMS devices such as BAW and low frequency silicon resonators can be used to reach further miniaturization and to lower the power dissipation of 2.4GHz transceivers targeting BAN and WSN applications. The system requirements for improving such networks are derived after analyzing appropriate low power communication protocols. A super-heterodyne transceiver architecture taking advantages of the high-Q of BAW resonators to reach lower phase noise and implement highly selective RF filters to reject interferers or unwanted IF harmonics is then presented. The design of related MEMS-based specific circuits is also discussed in details. Experimental results validate the functioning of the complete transceiver in both RX and TX modes. The measurements also demonstrate phase locking of the synthesizer to an electronically temperature-compensated low frequency silicon resonator, which is used to implement a unique ultra-low power oscillator for both RTC and reference frequency functions. Key measured features are a phase noise of −140dBc/Hz at 1MHz offset and the demonstration of 1Mbps GFSK modulation in TX. The receiver sensitivity reaches only −66dBm at 200kbps requiring further investigations to understand the reasons of the current limitation.

Frequency synthesis for a low-power 2.4 GHz receiver using a BAW oscillator and a relaxation oscillator

Miniaturization and reduction of power dissipation are two issues that currently prevent the seamless integration of wireless and networking capability into any tiny high-tech object such as hearing aids or miniature drug delivery monitoring devices or implants. The combination of MEMS technologies, yielding novel devices such as RF bulk acoustic wave (BAW) resonators and filters or low frequency silicon resonators, with RF ICs call for several innovations at the architectural, packaging, circuit and device levels to demonstrate the miniaturization and power reduction potential of the involved technologies.