Methods to generate UWB signals:
- Multi-band systems: Frequency Hopping/Multi-Carrier OFDM
- Single-band approach: Time Hopping, Direct Sequence or Direct Sequence Impulse
Pulse Shape Design Requirements for multi-pulse UWB-IR Systems:
1. Flexibility in the frequency domain. FCC and ETSI constraints.
2. Short and finite time duration Large Bandwidth.
3. Easiness to implement and Low complexity.
4. Pulses with same length, same energy and similar bandwidth.
5. Mutual-orthogonal conditions at the receiver: Including antenna and channel
6. Narrowband Interference suppression
- Existing orthogonal pulse constructions:
1. Modified Hermite Pulses (MHP):
Pulses of order 0 and 1 needs frequency shift to meet FCC spectral mask
The pulse length is not constant over all the n pulses.
2. Prolate Spheroidal Wave Function (PSWF) Pulses:
They are based on eigenvalue decomposition. High implementation complexity.