Biomedical Engineering Reference
In-Depth Information
Matrix
keyboard
Telephone line
DTMF
generator
Low
Pass
Filter
Transmitter
unit
to receiver
Encoded ECG
data
PES
Module
Local
EPBAX
Unit
Switch
Fig. 4.8
ECG transmission scheme using standard telephone
Fig. 4.9 Test results for ECG encoding and detection of header using PSTN communication
line. a Encoded ECG from PES, b Packet detection and serial interrupt generation at receiving
end
4.3.4 ECG Transmission Using Wireless Communication
For ECG transmission using wireless communication, Panasonic Make cordless
telephone set (model: KX-TG2338BX) operating in 2.4 GHz ISM band was used.
Here, the encoded bit stream was DC biased with appropriate value before sending
it to the transmitter unit. Since the existing telephone (Cordless) set was utilized
for ECG transmission purposes, the primary requirement was to block the DC of
the telephone line. Actually in its working, the receiver utilizes DC of the trunk
line for its own working supply purposes, the level of which varies from 'On-hook'
and 'Off-hook' conditions. The analog receivers modulates this DC trunk line in
order to transmit the voice/audio signal (of about 5 kHz bandwidth) using AM or
FM principles. Now-a-days digital receivers modulates this line with ASK, FSK,
BPSK or even quadrature phase shift key (QPSK) technique in order to achieve all
the advantages of digital modulation. The receiver utilized QPSK modulation to
transmit the digital bits as well as QPSK demodulation to extract digital bit
streams.
 
Search WWH ::




Custom Search