Matteo Contaldo

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 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.

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

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.

Ultra low power and miniaturized MEMS-based radio for BAN and WSN applications

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.

A 5.4dBm 42mW 2.4GHz CMOS BAW-based quasi-direct conversion transmitter

The trend of low-data rate wireless sensor networks (WSN) to interface at higher data rate with other devices or networks using standard protocols such as Bluetooth Low Energy and ZigBee, calls for a flexible RF system able to transmit efficiently with various modulation schemes over a wide range of data rates. For the 2.4GHz ISM band, direct modulation [1], direct conversion [2] and double conversion [3] transceiver architectures have been implemented, showing a general trend of an increase in the transmitter complexity in order to address problems such as PA pulling of the LO, oscillator leakage on the antenna and I/Q mismatch. This usually comes at the cost of a lower overall efficiency. A transmitter based on BAW resonators represents an interesting solution to combine architecture simplicity, low-power consumption and spectrum quality. Differently from narrowband BAW-based transmitters targeted to OOK modulations as in [4], we present a wideband quasi-direct conversion architecture to take advantage of the BAW resonators filtering and power managing capabilities, and allowing to achieve data rates as high as 1Mb/s. The transmitter architecture is based on a particular frequency selective BAW-based PA, representing to our knowledge the first physical implementation of a truly co-designed PA and BAW resonators.

A low-power fully integrated RF locked loop for Miniature Atomic Clock

Very accurate local clocks play a fundamental role in modern communication and navigation applications. High-precision references enable fast communication data rates, while in navigation they allow longer holdover operation times in the absence of a synchronization signal, for example from the Global Positioning System (GPS). Even if this high accuracy can be achieved with atomic clocks, only the recent developments in photonics and MEMS processes allowed reaching the low power consumptions and small sizes needed for hand-held devices [1], paving the way to the realization of Miniature Atomic Clocks (MAC). However, reaching the target of overall device volumes <1cm3 and power consumptions <30mW [2] requires further miniaturization and improved design of all the system aspects, including the RF control electronics, which has to consume low power without affecting the clock performances. State-of-the-art implementations as [3] and [4] reached interesting low-power consumption performances, but using discrete electronic components that limit system miniaturization. This work presents a fully integrated frequency locked loop designed for MAC applications, tested in combination with a buffered 87Rb cell system based on coherent population trapping (CPT) interrogation.

Driving an eXtra Small Atomic Resonator with low-power integrated RF frequency and laser locked loops

The first prototype of an eXtra Small Atomic Resonator (XSAR) was presented by CSEM in 2009. This paper describes the progress realized in 2010 towards the realization of a low-power miniature atomic clock. We present a second prototype as well as the first RF frequency and laser locked loops fully integrated on a chip.

MEMS-based all-digital frequency synthesis for ultralow-power radio for WBAN and WSN applications

This paper explores the use of MEMS devices such as bulk acoustic wave (BAW) and low frequency silicon resonators, in combination with digital circuits and techniques, to reach miniaturization and low power dissipation in a 2.4 GHz transceiver targeting wireless body area networks (WBAN) and wireless sensor networks (WSN) applications. Precise phase locking of the BAW digitally controlled oscillator (DCO) to the low-frequency temperature compensated oscillator is demonstrated. Additional cancellation within the ADPLL of the deterministic jitter induced by the bi-frequency mode on the 32 kHz clock is proven, with a residual modulation on the DCO command word corresponding to ±0.5 ppm relative frequency deviation. The RF resulting after frequency up-conversion of the system IF signal with the DCO shows an excellent phase noise of −136.6 dBc/Hz at 1 MHz offset frequency, for a total synthesizer current consumption of 7.52 mA under 1.6 V supply. In addition, 1 Mb/s GFSK Bluetooth and Bluetooth Low Energy modulations have been successfully validated in transmission.

A 2.4-GHz Narrowband MEMS-Based Radio

This chapter presents an innovative wireless transceiver architecture that rely on MEMS components to achieve further miniaturization and significant power dissipation reduction compared to low-power radios targeting LDR to MDR applications. It is shown in particular how the limitations of MEMS devices can be waived at the architectural level and how their combination can lead to innovative concepts preserving or even surpassing the performances of current mainstream optimized solutions. Besides the architectural aspects, the chapter also focuses on the design of some ultra-low-power and MEMS-specific circuits and reports measurement results of the complete system. The synthesizer, which is based on a low-phase-noise fixed-frequency BAW DCO and a variable IF LO obtained by fractional division from the RF carrier, achieves a phase noise of − 113 dBc/Hz at 3 MHz. To correct for its ageing and thermal drift, the BAW DCO can intermittently be phase locked to a 3-μ A, ± 5-ppm, 32- K Hz reference, which is obtained after temperature-dependent fractional division of the signal of a 1- M Hz silicon resonator so as to compensate the non-idealities of the latter (frequency tolerance, large thermal drift). An all-digital PLL implementation guaranties a nearly immediate synthesizer settling when returning from an idle period, owing to the memorization of the previous lock conditions eliminating a multi-MHz XTAL and its associated start-up time. A sensitivity of 87 dBm was obtained in receive mode at 100 kb/s for a global consumption of 6 m A. The transmitter demonstrates a high-data-rate quasi-direct 1-point modulation capability with the generation of a 4-dBm, 1-Mbps, GFSK signal with an overall current of 20 m A. Both the receiver and transmitter further take advantage of BAW filters to implement interferers, image, and spurious rejection.