Analog, Digital & RF Circuit DesignImpulse Radio Ultra-WideBand (IR-UWB) systems have drawn growing attention for wireless sensor networks such as Wireless Personal Area Network (WPAN) and Wireless Body Area Network (WBAN) systems ever since the Federal Communications Commission (FCC) released the spectrum between 3.1 and 10.6GHz for unlicensed use in 2002. The restriction on transmitted power spectral density in this band is equal to the noise emission limit of household digital electronics. This band is also shared with several existing service, therefore in-band interference is expected and presents a challenge to UWB system design.
UWB devices as secondary spectrum users must also detect and avoid (DAA) other licensed users from the cognitive radio???s point of view. For the DAA requirement, it is more effective to deploy signal with variable center frequency and a minimum 10dB bandwidth of 500MHz than a signal covering the entire UWB spectrum range with fixed center frequency.
A key requirement of the applications using IR-UWB signal is ultra-low power consumption for longer battery life. Also, cost reduction is highly desirable. Recently, digital IR-UWB pulse generation is studied more than analog approach due to its lower power consumption.
An all-digital pulse generator in a standard 0.13-um CMOS technology for communication systems using Impulse Radio Ultra-WideBand (IR-UWB) signal is presented. A delay line-based architecture utilizing only static logic gates and leading lower power consumption for pulse generation is proposed in this thesis. By using of all-digital architecture, energy is consumed by CV2 switching losses and sub-threshold leakage currents, without RF oscillator or analog bias currents. The center frequency and the fixed bandwidth of 500MHz of the output signal can be digitally controlled to cover three channels in low band of UWB spectrum. Delay based Binary Shift Keying (DB-BPSK) and Pulse Position Modulation (PPM) schemes are exploited at the same time to modulate the transmitted signals with further improvement in spectrum characteristics. The total energy consumption is 48pJ/pulse at 1.2V supply voltage, which is well suitable for WBAN systems.ope
