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.
[Show abstract][Hide abstract] ABSTRACT: The EKV MOS transistor model and design methodology evolved from the first weak inversion transistor models of the 1970's. In this first-hand account, Christian Enz chronicles the evolution of the hierarchical structure, limited parameters and flexibility of the EKV model that he developed with colleagues such as Francois Krummenacher and Eric Vittoz (the "E" "K" and "V" of EKV) at the Centre Electronique Horloger (CEH) in Neuchatel. With the aggressive downscaling of CMOS technologies today, the EKV compact model is shifting increasingly from the traditional strong inversion region toward moderate and weak inversion regions.
[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: This paper presents for the first time a theoretical study of the second order effects of a 4-bit Phase-domain Analog-to-Digital Converter (ADC) circuit for QPSK demodulation and analyzes its benefits and drawbacks. The study encompasses the phase resolution, dynamic range and robustness of this circuit to circuit non-idealities and noise. Our analysis shows that the phase ADC is extremely robust against circuit non-linearities, offsets and noise while providing a large dynamic range compared to traditional amplitude ADCs.
International Symposium on Circuits and Systems (ISCAS 2010), May 30 - June 2, 2010, Paris, France; 01/2010
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