Jérémie Chabloz

A Low-Power 2.4GHz CMOS Receiver Front-End Using BAW Resonators

A low-power 2.4GHz heterodyne receiver front-end is integrated in 0.18mu;m CMOS using BAW solidly mounted resonators. The resonators with Qs of up to 580, provide both impedance matching and selectivity. An image rejection of up to 50dB, a NF of 11dB and IIP3 of -16.1dBm with a power dissipation of 1.8mW are demonstrated

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

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.

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 2.4GHz MEMS-Based Transceiver

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.

Ultra low-power MEMS-based radio for wireless sensor networks

The recent advances made in MEMS and particularly in RF MEMS technology are enabling new architectures for the integration of RF transceivers with improved performance and smaller size. Several fundamental building blocks benefit from the availability of high-Q resonators in the RF front-end, the analog baseband and the frequency synthesizer to lower power consumption, phase noise and die area. In addition, the compatibility of MEMS with CMOS opens the door to a higher integration level using for example an above-IC approach. This paper presents the recent work made at CSEM in the field of ultra low-power transceiver for wireless sensor network applications. It first presents the high-Q resonators, including the BAW resonators used in the RF front-end and in the RF oscillator together with MEMS used in the low frequency oscillators and IF section. These MEMS are activated thanks to an A1N piezo layer avoiding the need for high voltage generation which is incompatible with the low-power and low-voltage requirement. These MEMS are also temperature compensated by the combination of additional layers and electronics means. The paper then focuses on the main building blocks that can take advantage of high-Q resonators starting with the RF front-end. The fundamentals of oscillators built around high-Q devices is described, highlighting the basic trade-offs. Finally, new approaches for the analog baseband are described. This includes an example of a quadrature Sigma-Delta converter combining the different functions of anti-alias and image-reject filter together with analog-to-digital conversion. An alternative to traditional Sigma-Delta oversampled converters is the use of phase analog-to-digital converters to directly quantize the phase information without the need to convert the amplitude. This innovative approach can save power and complexity for all wireless applications using phase or frequency modulations.

A novel I/Q mismatch compensation scheme for a low-IF receiver front-end

Any quadrature IF front-end inherently suffers from mismatch between its I and Q paths. This results in an image rejection degradation, thus decreasing the dynamic range. In this paper, a novel mismatch compensation scheme for a low-IF receiver, but also suitable to many other quadrature front-ends, is proposed. With this approach, gain and phase imbalance corrections result independently from simply two gain adjustments. This allows an analog realization, therefore avoiding costly DSP implementation. In order to compute the wanted compensation gains, an LMS-type adaptive algorithm is also proposed. Its robustness and stability are investigated by extensive simulations.

Building Blocks for an Ultra Low-Power MEMS-based Radio

The recent advances made in MEMS and particularly in RF MEMS technology are enabling new architectures for the integration of RF transceivers with improved performance and smaller size. Several fundamental building blocks benefit from the availability of high-Q resonators in the RF front-end and the frequency synthesizer to lower power consumption, phase noise and die area. In addition, the compatibility of MEMS with CMOS opens the door to a higher integration level using for example an above-Q approach. This paper presents the recent work made at CSEM in the field of low-power transceiver for wireless sensor network applications. It first presents the high-Q resonators, including the BAW resonators used in the RF front-end and in the RF oscillator together with MEMS used in the low frequency reference oscillators. These MEMS are activated thanks to an AlN piezo layer avoiding the need for high voltage generation which is incompatible with the low-power and low-voltage requirement. These MEMS are also temperature compensated by the combination of additional layers and electronics means. The paper then focuses on the main building blocks that can take advantage of high-Q resonators. The fundamentals of oscillators built around high-Q devices is described, highlighting the basic trade-offs. It is also described how to take advantage of such devices within a receiver front-end.

A low-power programmable dynamic frequency divider

In this paper, a solution to realize a low-power programmable frequency divider using dynamic logic is proposed. By cascading compact dual-modulus divider slice with recursive feedback mechanisms, any dividing ratio is easily implemented. A 5-stages 0.18 mum CMOS implementation demonstrates a power consumption factor as low as 235 nW/MHz under 1.2 V supply for high dividing ratios.

A Low-Power Versatile CMOS Transceiver for Automotive Applications

In this work, we will present a wake-up controller system complete with UHF and LF transceivers. Typical targeted applications are automotive remote/passive keyless entry key-fob and central unit solutions. Details for the implementation of the UHF transceiver front-end and signal processing are given that demonstrate the desired versatility in frequency, data rate and output power configurations.

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.