Conference Paper

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

Swiss Center for Electron. & Microtechnol., Neuchatel
DOI: 10.1109/ECCTD.2007.4529599 Conference: Circuit Theory and Design, 2007. ECCTD 2007. 18th European Conference on
Source: IEEE Xplore

ABSTRACT 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.

0 Bookmarks
 · 
69 Views
  • [Show abstract] [Hide abstract]
    ABSTRACT: A quadrature sub-sampling direct conversion mixer capable of sampling two or more bands concurrently using a single sampling frequency is presented. The implementation of the mixer to sample a band in quadrature and downconvert it to baseband is discussed and it is shown how this idea could be extended to sample in quadrature two or more bands concurrently. The proposed circuit is analyzed in detail and the results are validated using Spectre RF simulations for a 0.18 mum CMOS process.
    Circuit Theory and Design, 2009. ECCTD 2009. European Conference on; 09/2009
  • [Show abstract] [Hide abstract]
    ABSTRACT: A low power sub-sampling multi-channel 2.4-GHz receiver front-end is presented. Bulk Acoustic Wave (BAW) resonators which intrinsically exhibit high quality factor (Q) are exploited in the frequency synthesis to provide low phase noise signal with low power consumption. A low power solution to perform channel selection and filtering directly at RF by employing current reuse and using a BAW resonator is proposed. The filter is capable of tuning the bandwidth and thus making the front-end to be suitable for multi-band/multi-standard applications. The overall performance of the front-end is improved by additional discrete time filtering which also down-converts the wanted channel to baseband in quadrature. The proposed front-end is designed and integrated in a 0.18-μm CMOS process. Measurements reveal that the front-end is capable of providing very narrow band filtering down to 300 kHz. The rejection at 10-MHz offset is 62 dB with conversion gain of 44.2 dB.
    IEEE Journal of Solid-State Circuits 01/2013; 48(6):1343-1356. · 3.06 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: A Bulk Acoustic Wave (BAW) resonator based 2.4-GHz low power receiver is presented in this work. The intrinsic high quality factor (Q) of the BAW resonator (around 400 at 2.4-GHz) is exploited to provide channel selection at RF and in the frequency synthesis. A novel way of addressing multiple channels (arbitrary frequency) using integer dividers and a BAW digitally controlled oscillator (DCO) and thus avoiding the need for a PLL is proposed in this work. To the best of our knowledge, this work is the first one to report a multi-channel (arbitrary frequency) receiver whose frequency synthesis depends solely on the low phase noise BAW DCO and does not include a PLL. A BAW pseudo-lattice with frequency and bandwidth tuning is proposed which significantly improves the rejection of unwanted signals in the channel filter. A quadrature sub-sampling mixer is used to down-convert the selected channel to baseband. The receiver is designed and integrated in a 0.18- μm CMOS process. With Q-boosting, the channel filter provides bandwidth down-to 1-MHz. For a BFSK modulated signal, the receiver exhibits a sensitivity of -78 mathchar "702D dBm at a rate of 268-kbps for a BER of 10-3 . The total power consumption of the receiver is 5.94-mA from a 1.8-V power supply.
    IEEE Journal of Solid-State Circuits 01/2013; 48(7):1689-1700. · 3.06 Impact Factor