Development of radio frequency transmitters including on‐chip antenna for intelligent human sensing systems

Abstract

This paper presents the essentials of the development of an integrated smart microsensor system that has been developed to monitor the motion and vital signs of humans in various environments. Integration of RF transmitter technology with complementary metal-oxide-semiconductor/micro electro mechanical systems (CMOS/MEMS) microsensors is required to realize wireless smart microsensors for the monitoring system. Sensors for the measurement of body temperature, perspiration, heart rate (pressure sensor), and motion (accelerometers) are candidates for integration on the wireless smart microsensor system. In this paper, the development of radio frequency transmitter (RF) that will be integrated on wireless smart microsensors is presented. A voltage controlled RF-CMOS oscillator (VCO) has been fabricated for the 300-MHz frequency band applications. Also, spiral inductors for an LC resonator and an integrated antenna have been realized with a CMOS-compatible metallization process. The essential RF components have been fabricated and evaluated experimentally. The fabricated CMOS VCO showed a conversion factor from voltage to frequency of about 81 MHz/V. After matching the characteristic impedance (50 ) of the on-chip integrated antenna and the VCO output, more than 5 m signal transmission from the microchip antenna has been observed. The transmitter showed remarkable improvement in transmission power efficiency by correct matching with the microchip antenna. Essential technologies of the RF transmitter for the wireless smart microsensors have been successfully developed. Also, for the 300-MHz band application, the integrated RF transmitter, with the CMOS oscillator and the on-chip antenna, has been successfully demonstrated for the first time. 

Integrated Inductors for RF Transmitters in CMOS/MEMS Smart Microsensor Systems

“…Figure 3 shows the configuration of a simple RF transmitter for monolithic integration with CMOS/MEMS smart sensors [8]. The transmitter can be realized by standard CMOS technology, and it is integrated with CMOS/MEMS sensors.…”

“…Figure 4 shows a photograph of a fabricated CMOS VCO that was used as the FM transmitter in the smart microsensor by our previews works [8]. It consists of three-stage inverters and a power amplifier with 1-, 3-, and 9-times buffer stages.…”

“…The configuration of the measurement system for the transmission characteristic is shown in Figure 10. The packaged antenna on the silicon chip and the CMOS VCO chip were attached to SMA connectors for transmission characteristic measurement [8]. Each measurement commenced by sending out the signal generated from the CMOS VCO via the antenna on silicon.…”

“…The integration of the RF communication unit, including RF circuitry, and the on-chip antenna on such smart complementary metal oxide-semiconductor/micro electro mechanical systems (CMOS/MEMS) sensors is required. Thus, essential fabrication technologies of the RF communication unit for wireless smart micro sensors have been developed [8]. Nevertheless, the passive matching element that is inductor was not yet integrated.…”

Evaluation of antenna-integrated 315MHz transmitter for smart microsensors

“…The integration of the RF communication unit, including RF circuitry, and the on-chip antenna on such smart complementary metal oxidesemiconductor/micro electro mechanical systems (CMOS/MEMS) sensors is required. Thus, essential fabrication technologies of the RF communication unit for wireless smart micro sensors have been developed [8]. In this paper, the evaluation of the prototype of an integrated smart microsensor system is reported.…”