A Sub-1μA Low-Power FSK Modulator for Biomedical Sensor Circuits

Low-power wireless telemetry is extremely important for non-invasive monitoring of biomedical sensor signals. Usually for successful monitor of various physiological parameters, an implantable sensor incorporates a transmitter unit to send the sensor data outside of the human body for further diagnostics. This paper reports a new low-power frequency shift keying (FSK) modulator for a biomedical sensor circuits. With a very simple architecture, this circuit integrates the modulation functionality into the oscillator itself by using the data signal to control the oscillation frequency. Besides, it can generate tunable carrier frequencies for different data signals. The carrier frequency can range from 5 MHz to tens of MHz with configurable tuning for adaptable data rate applications. In addition, the data rate from 450kbps to several Mbps can be achieved for common applications. The modulator is implemented in a 0.35 μm bulk-CMOS process with a power supply voltage of 2.5 V. For a carrier frequency of 10MHz the entire unit consumes less than 1 μA current which makes the design very suitable for low-power biomedical application. The circuit has already been submitted for monolithic integration.