An Ultra-Wideband Sensor Node Development with Dual-Frequency Band for Medical Signal Monitoring - Ultra Wideband Wireless Body Area Networks - page 103

Fig. 5.21 CPWG parameters

Ground RF track Ground

Signal plane

W
W+ 2G

ε PCB core

h

r

Ground plane

Z 0 ¼ 60p
e eff

1

ohms ;

Kk ðÞ þ Kk ðÞ

K ðÞ

Kk 0

ðÞ

k 0 ¼

p

W
W þ 2G ;

k ¼ 1 k 2 ;

4h ffi

q

1 k 1

pW

tanh

k 0

;

k 1 ¼

1 ¼

;

p W þ 2G ð Þ

tanh

4h

Kk ðÞ K ð k 1 Þ
K ðÞ K ð k 0

1 þ e r

dt
1 t 2

K ðÞ¼ Z 1
0

1 Þ
1 þ Kk ðÞ K ð k 1 Þ
K ðÞ K ð k 0

e eff ¼ ; p ð 5 : 11 Þ

ð Þ 1 k 2 t 2 ð Þ

1 Þ

where Z 0 is the impedance of the CPWG, e r is the relative permittivity of the PCB
material, W, G, and h are CPWG parameters as depicted in Fig. 5.21 .
A block diagram showing the overall integration of the sensor node is depicted
in Fig. 5.22 . The time domain signals obtained at various places of the sensor node
are shown in Fig. 5.23 . UWB PRF is chosen to be 100 MHz for the signals shown
in Fig. 5.23 .
Two versions of the dual band sensor node are implemented. The first sensor
node has dimensions of 30 mm (L) 9 25 mm (W) 9 0.7 mm (H); hence, this
sensor node is suitable for wearable applications. The second sensor node is cir-
cular in design. It is implemented as a combination of two PCBs that can be
interconnected with each other in a stack-up configuration. This design has a
diameter of 15 mm; hence, it is suitable for both wearable and implantable
applications. Both sensor node designs are shown in Fig. 5.24 . Figure 5.25 depicts
different regions of the PCB design for the first sensor node.

5.2.10 Comparison

Table 5.3 compares specifications of some of the existing WBAN platforms with
the suggested sensor node design. Wireless sensor nodes based on narrow band
platforms are used widely for WBAN applications. Most of the UWB based
designs available in the literature are either limited to Integrated Circuit (IC) based