Low Power CMOS Implementation of Ultra Wideband Radios

1
Low Power CMOS Implementation of Ultra Wideband
Radios
2
Shannon likes UWB!
Bits/sec/Hz
4
3
Energy Limited
2
Bandwidth Limited
1
-5db
Eb/N0
5 db
10 db
15 db
1/2
UWB
1/4
1/8
1/16
3
Background

• Harmuth -- 60s pioneer in nonsinousoidal
  transmission
• didnt have DSPs!
• Recent system demonstrations
• Mulispectral Systems Inc. military communication
  systems
• Time domain Inc. Impulse Radio

4
Impulse Radio Transmission

• Sparse codes keep power low.
• Long codes give high processing gain.
• Aperiodic sequence is relatively immune to
  multipath.

5
Impulse Radio Receiver

• Impulse radio uses gated correlator to
  approximate a matched filter.
• Synchronization is critical.
• Current implementation uses exotic devices to
  generate and detect impulses.

6
CMOS UWB Radio Concept

• Use antenna/filter characteristics to shape pulse
• Use switching transient edge as broadband
  excitation
• Transceiver requires minimal analog circuitry.

7
Edge-Driven Waveforms

• Waveforms are mainly determined by channel
  bandwidth.
• Increased relative bandwidth (h) results in
  narrower pulses with fewer ringing cycles --
  approaches monocycle for h0.5.

8
Feasibility

• The main technical challenge is to couple
  significant power from a transient -- needs
  wideband power amplifier.

9
Proposal

• Year 1) Develop the architecture of a CMOS
  implementation to generate UWB signals based on
  edge transients. Investigate architectures that
  are CMOS compatible for the detection circuitry
  with particular emphasis on circuits that will be
  able to support the very large dynamic ranges
  required.
• Year 2) Implement a prototype in both discrete
  and integrated form and compare the experimental
  results to the theory. Develop a CMOS approach
  for detection and synchronization.
• Year 3) Build prototype of UWB radio and compare
  results to theoretical analyses of years 1 2.