2. Electronic communication system
Transfer info from one place to another
Is the transmission, reception and processing of
information between two or more locations using
electronic circuits
3 main components of communication
system:
Transmitter
Channel
Receiver
3.
4. Transmitter – circuit/device which converts
original source info to a form more suitable
for transmission
Medium/channel – provides means of
transporting signal between transmitter and
receiver
Noise – unwanted signals that interfere with
the info signal
Receiver – circuit/device which accepts
transmitted signals and converts them back
to their original form
5. Two types:
Guided propagation
Free propagation
6.
7.
8. Signal = set of information/data represented
by mathematical functions of time
System will process a set of signals (i.e.
inputs) to produce another set of signals (i.e.
outputs)
9. 1. Continuous-time and discrete-time signals
2. Analog and digital signals
3. Periodic and non-periodic signals
4. Even and odd signals
10. Continuous-time signal: Specified at every
value of time t. Represented by x(t).
Discrete-time signal: Specified at separate
values of time. Represented by x[n].
Continuous-time
signal
Discrete-time
signal
11.
12.
13. Binary signal
Is a type of digital signal
Has only two possible levels (‘high’, or ‘low’)
14. Periodic signal: Signal that repeats itself over
a time period T. Otherwise, it is non-periodic
A continuous-time periodic signal satisfies
the condition x(t) = x(t ± T), where T is the
period
A discrete-time periodic signal satisfies the
condition x[n] = x[n + N], where N is the
period
16. Even Signal
A signal that is identical to its reflection about
the origin
Symmetric about the vertical axis
x(-t) = x(t), or x[-n] = x[n]
Odd signal
Symmetric about a line midway between the
vertical axis and the negative horizontal axis and
passing through the coordinate origin
Signal is zero at the origin, and
-x(-t) = x(t) or -x[-n] = x[n]
17. Decibel (dB) – to define power ratios, voltage
ratios or current ratios
Note:
ö
÷ ÷ø
æ
dB P
ç çè
=
1
P
2
10log10
Power levels P1 and P2 must be in same units
+ dB power gain
- dB power loss (attenuation)
0 dB unity power gain (i.e. P1 = P2)
18. Given P1/P2 = 100. Convert this absolute
power ratio to dB
20. Decibel milliwatt (dBm) – a unit of
measurement to indicate the ratio of a
power level with respect to a fixed
reference level i.e. 1 mW
dBm P
ö çè
÷ø
= æ
mW
1
10log10