Biomedical Engineering Reference
In-Depth Information
0.01
0.01
E9D3
E9D3
waveform of the
tumor-free case
0.005
0.005
waveform of the
tumor-contained case
0
0
averaged waveform
(calibraon waveform)
calibraon waveform
-0.005
-0.005
-0.01
-0.01
0
0.5
1
1.5
2
2.5
3
0
0.5
1
1.5
2
2.5
3
Time (ns)
Time (ns)
Fig. 6 Received signals compared with average waveform for two cases of normal and malignant
tissues. [ 7 ]
Correlator
Clk
Generator
baseband
signal
processing
dt
Pulse Generator
LNA
Data
Template
Waveform
a
b
Fig. 7 Typical transceiver of a ultra-wideband system
an average waveform of the received signals is calculated. The next step is comparing
the received signals with this waveform, which indicates the probability of a tumor
existing in a specific location. Figure 6 shows two cases of normal and malignant
tissues. As shown, for the malignant tissue, differences between received signal and
the average (calibration) waveform is much higher than for the normal tissue.
Figure 7 shows a symbolic block diagram of UWB medical imaging system
for breast cancer detection. As shown, a UWB medical imaging system has ma-
jor differences when compared with narrowband systems. First, since there is no
carrier in this type of communication, there is no need for complicated modulation
and demodulation blocks. These are among the most complicated blocks used for
conventional continuous wave transmission systems. Not having these complex com-
ponents makes the transmitter architecture of UWB systems inexpensive, simpler to
design, and simpler to implement, when compared to conventional radio systems.
From this point of view, a UWB system's block diagram is much simpler than
its narrowband counterparts. As shown in Fig. 7 , in UWB systems, time-domain
modulation is used for transmitting and receiving data. This makes the correlation
and sample waveform generator blocks of this system very important.
According to the work by Proakis et al. [ 18 ], the optimal receiver for a signal
transmitted in an additive white Gaussian noise (AWGN) channel is a correlation
or a matched filter receiver which makes SNR (signal to noise ratio) maximum.
Figure 7 b shows a receiver architecture that is made of three major blocks: a low-noise
amplifier (LNA), a correlation circuitry and a block for providing template waveform
for correlation circuit. In addition, there is also the baseband signal processing unit
in which the decision making is performed.
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