Biomedical Engineering Reference
In-Depth Information
Integrator
Thresholder
Multiplier
Filter
∫
Local
Template
Generator
Timing
Generator
Fig. 4.7
A coherent UWB receiver
4.3.2 Coherent UWB Receivers
In a coherent receiver, correlation is performed between the received waveform
and a locally generated template of the waveform. It requires having a good
estimate of the channel, and a template generation mechanism, which makes it
complex in design and high power consuming. The development of an optimum
coherent receiver is demonstrated in [
24
]. Figure
4.7
depicts a basic block diagram
of the optimum coherent receiver architecture. The template generated at the local
template generator of the optimum coherent receiver is closely matched to the
transmitted signal. It also has to perform channel estimation in order to com-
pensate for the presence of multipath components. This results in increased design
complexity and high power consumption.
Coherent rake receivers use energy of precise multipath components of the UWB
signal in order to reconstruct the original waveform [
25
]. This type of coherent
receivers requires large number of rake fingers due to the high temporal resolution of
the UWB signals. Performance of both types of coherent receivers deteriorates with
timing jitters and synchronization errors [
26
]. Performance of coherent receivers is
compared with that of a non-coherent receiver in [
27
,
28
], which show that better
accuracy can be obtained in coherent receivers at the cost of high circuit complexity
and high power consumption. It has been shown in [
28
] that a non- coherent receiver
will perform better than a coherent receiver for timing jitter values above 18 ps.
4.4 UWB Sensor Node Designs
While many publications present the implementation of UWB transmitters in
Integrated Circuits (IC), only few publications present the full implementation of
UWB based sensor platforms that should other peripheral electronics, such as
