SUMMARYLow-frequency (flicker) noise is one of the most important issues in the design of direct-conversion zero-IF front-ends. Within the front-end building blocks, the direct-conversion mixer is critical in terms of flicker noise, since it performs the signal down-conversion to baseband. This paper analyzes the main sources of low-frequency noise in Gilbert-cell-based direct-conversion mixers, and several issues for minimizing the flicker noise while keeping a good mixer performance in terms of gain, noise figure and power consumption are introduced in a quantitative manner. In order to verify these issues, a CMOS Gilbert-cell-based zero-IF mixer has been fabricated and measured. A flicker noise as low as 10.4 dB is achieved (NF at 10 kHz) with a power consumption of only 2 mA from a 2.7 V power supply. More than 14.6 dB conversion gain and noise figure lower than 9 dB (DSB) are obtained from DC to 2.5 GHz with an LO power of −10 dBm, which makes this mixer suitable for a multi-standard low-power zero-IF front-end.

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A silicon pressure microsensor fabrication process is reported. The microsensor has been designed as a low-cost disposable device for invasive blood pressure measurements. Results obtained from static, dynamic and leakage pressure tests are presented. A sensitivity of has been measured. The combined linearity and hysteresis is less than 1.5% FSO. The dynamic response is fast enough to reproduce the blood pressure waveform of the human heart. Results based on a material biocompatibility study are also included.

The main features involved in the design of a pressure sensor are the maximum non-destructive pressure and the sensitivity. In this work, these two characteristics are related to the following design variables: dimensions of the membrane and mechanical properties of the selected material. Von Misses stress and strain distributions have been calculated by the finite-element method (FEM). The knowledge of these distributions is a good design guideline lbr an accurate location of the piezoresistors. The results obtained have been appl!ed to the design of silicon microsensors for biomedical and domestic applications.