Biomedical Engineering Reference
In-Depth Information
Receiver
antenna
r'(t)=s
B
(t)+n
B
(t)
T
s
LNA
G:48 dB
NF:3.5 dB
nT
s
BPF
(3.5-4.5 GHz)
()
2
LPF
(1GHz)
Mixer
r(t)=s(t)+n(t)
VCO (4 GHz)
Fig. 3.8
The energy detection receiver architecture used in the simulations
receiver is used as the receiver model for the simulations (Fig.
3.8
)[
19
]. The
integration duration (T
s
) for the receiver is 2 ns, which is equal to the pulse width
of the UWB signal. The small integration time helps to reduce the multipath
interference that might occur during UWB communication.
The bit errors in a WBAN environment mainly occur due to multipath inter-
ference and random fading of the UWB signal that originates from reflection from
various surfaces and different absorption characteristics of objects, such as various
body surfaces and indoor equipment. Assume that a sensor node transmits data
with a sufficient transmit power for the signal to be detected by the receiver node
in an ideal free space scenario without fading and multipath interference. Also,
assume that two identical sets of data are transmitted using the same transmit
power and same separation distance as above in a realistic WBAN environment
that is susceptible to multipath interference and random fading with one data set
transmitted using a higher PPB value and the other with a lower PPB value. The
transmit signal with higher PPB transmission results in a lower BER than a lower
PPB transmission for the same separation distance in a realistic environment with
fading and multipath interference. Consider the energy detection receiver archi-
tecture shown below:
The input to the band pass filter at the UWB receiver of the parent node can be
expressed as:
8
<
n
ð
t
Þ
if there is no pulse present
in a time slot
r
ð
t
Þ¼
ð
3
:
9
Þ
s
ðÞþ
n
ð
t
Þ
:
if there is a pulse present
in a time slot
where r (t) is the input to the band pass filter, s(t) is the received UWB signal and
n(t) is the Additive White Gaussian Noise (AWGN) with zero mean and a flat
power spectral density of N
0
/2. The received signal is then sent through a Band
Pass Filter (BPF) with a 1 GHz bandwidth centered at 4 GHz. Then it is down
converted into a base band signal using a mixer. A Low Pass Filter (LPF) with a
bandwidth of 1 GHz is applied before the integrator. The received signal at the
input to the integrator can be given by:
