CMOS oscillators to satisfy 802.15.4 and Bluetooth LE PHY specifications without a crystal reference

We compare measured CMOS relaxation oscillator performance against physical-layer specifications defined by low-power RF communication standards IEEE 802.15.4 and Blue-tooth Low-Energy with the aim of satisfying those specifications without a crystal oscillator. The time and frequency aspects of these FSK-based specifications concern RF channel, modulation frequency, data rate, and sleep time. If they can be satisfied without a crystal oscillator, future wireless ICs can be designed that do not rely on a crystal reference and still perform standards-compatible communication. We find most physical-layer specifications can be satisfied by relaxation oscillators with the exception of RF carrier accuracy. The RF ring oscillator under test is dominated by flicker noise, which sets an Allan variance/jitter floor about an order of magnitude noisier than is required by current specifications.