Microwave communication uses electromagnetic waves between 1-30 GHz to transmit information over short distances. It allows for point-to-point communication and frequency reuse without interference. The microwave band provides 30 times more bandwidth than frequencies below it. A transmitter converts a signal to the uplink frequency, amplifies it, and filters it before transmission. A receiver converts the downlink frequency to an intermediate frequency, demodulates it to extract the original signal, amplifies it, and filters it before output. Fax machines transmit documents over phone lines by scanning, compressing, and transmitting images, then receiving, decompressing, and printing them.

1. BE8251-Basic Electrical and
Electronics Engineering
MICROWAVE COMMUNICATION

2. MICROWAVE COMMUNICATION
Microwave transmission refers to the technology of transmitting
information or energy by the use of electromagnetic waves whose
wavelengths are conveniently measured in small numbers of
centimeters; these are called microwaves.
This part of the radio spectrum ranges across frequencies of roughly
1.0 gigahertz (GHz) to 30 GHz.
These correspond to wavelengths from 30 cm down to 1.0 cm.

3. CONTD….
Used for point-to-point communications.
Allows nearby microwave equipment to use the same
frequencies without interfering with each other.
The microwave band has a bandwidth 30 times that of all the
rest of the radio spectrum below it.

4. TRANSMITTER

5. CONTD…
The signal to be transmitter must be at uplink frequency.
The converter multiply the signal frequency to uplink frequency after
it is encoded and modulated properly.
After converting the frequency, it is applied to power dividers. The
output of power divider goes to high power amplifier.
Normally travelling wave tube amplifiers or multi cavity klystron
amplifiers are used.
These tubes require good amount of cooling.

6. CONTD…
The modulation is performed at 70 MHz intermediate frequency and is
converted to a uplink frequency of 6 GHz.
The output of high power amplifiers are combined in a power
combining amplifier and the output is passes through band pass filter
and circulators.
 Frequency stability and power control are necessary to avoid
interferences. The manufacturing is high and it increases as transmitted
power increases.

7. RECEIVER

8. CONTD…
The first stage of the terminal station receiver is the front end converter
which is usually a double converter to convert the down link frequency
signal of the order of GHz into an intermediate frequency of 70 MHz.
Now this intermediate frequency signal is first passed through a chain
of bandpass filters and amplifier combinations to improve signal
strength.
 Thus the IF signal is demodulated to get the original baseband signal.
The FM used here is a phase-locked loop (PLL) type of FM
demodulator.

9. CONTD…
Now the signal is amplified after it is given to de-emphasis network.
A 5.5 MHz sound trap is provided in the circuit to get the sound IF.
Now this sound IF is given to FM detector to get the original audio
signal.

10. FAX
 Fax is a very important method of electronic communication.
 It is used to transmit any sort of written matter, picture,
diagram etc, from one place to another.
 This device acts through telephone line.
 The receiving fax machine reconverts the coded image and
prints a paper copy of the document.

11. FAX

12. GENERAL BLOCK DIAGRAM OF FAX

13. TYPES
 Photographic facsimile
 Document facsimile

14. PHOTOGRAPHIC FACSIMILE
 Gray level information is transmitted and printed in addition
to black and white.
 Typically, they are 8 or 16 gray levels that can be recognized
by the system.

15. DOCUMENT FACSIMILE
 Document facsimile system handles only black and white
levels, i.e, only two gray levels.

16. WORKING

17. WORKING
The input document is applied to the scanning process.
This scanner converts the print material into a set of points
represented by bit-mapped electrical signals.
This signal should be compressed by using compression
techniques.
The signal should be transmitted.

18. CONTD…
This transmitted signal is received by receiver and the
compressed signal is converted into decompressed signal by using
decompression method.
Here we can get original document and it is fed to the printer.

19. THANK YOU…..