Digital Signal Processing Reference
In-Depth Information
Fig. 5.8
Chip photograph of the 1
D
touch sensor on flexible foil. This circuit is made in technology
provided by Polymer Vision
Finger Tip
V
out
Serial Sensor
R
4
R
3
R
2
R
1
Read−Out
>
Clk
b
0
R
1
b
1
C
1
b
0
b
1
b
0
R
2
R
3
b
1
b
0
b
1
C
2
R
4
b
b
2
3
2
3
2
3
2
3
C
1
C
3
b
C
2
b
b
C
3
b
b
b
C
4
C
4
2.8 cm
Fig. 5.9
Schematic view of the flexible 2
D
touch pad with integrated pixel driver circuit and sensor
read-out circuit
5.4.2 2-Dimensional Touch Sensor
5.4.2.1 Architecture
The same technique of capacitive sensing, which is used in the 1
D
sensor can also
be extrapolated towards a 2-dimensional touch sensor, where the read-out circuit
measures the capacitance of the different pixels in a serial way. This is demonstrated
with the design of a flexible 2
D
touch pad with 4
4 pixels presented in Fig.
5.9
.
The row and column plates are respectively built in the first and the second metal
layer and they are built with 4
×
9mm
2
squares. When a finger is positioned on
top of a pixel, as depicted in the figure, an overlap capacitance is generated according
.
9
×
4
.
