Radio communication

technolgy
history
during radio's first two decades, called the radiotelegraphy era, the primitive radio transmitters could only transmit pulses of
radio waves, not the continuous waves which were needed for audio modulation, so radio was used for person-to-person
commercial, diplomatic and military text messaging. Starting around 1908 industrial countries built worldwide networks of
powerful transoceanic transmitters to exchange telegram traffic between continents and communicate with their colonies
and naval fleets. During World War I the development of continuous wave radio transmitters, rectifying electrolytic, and
crystal radio receiver detectors enabled amplitude modulation (AM) radiotelephony to be achieved by Reginald Fessenden
and others, allowing audio to be transmitted. On 2 November 1920, the first commercial radio broadcast was transmitted
by Westinghouse Electric and Manufacturing Company.

Bandwidth
A modulated radio wave, carrying an information signal, occupies a range of frequencies. The information (modulation) in a
radio signal is usually concentrated in narrow frequency bands called sidebands (SB) just above and below the carrier
frequency. The width in hertz of the frequency range that the radio signal occupies, the highest frequency minus the lowest
frequency, is called its bandwidth (BW).[31][36] For any given signal-to-noise ratio, an amount of bandwidth can carry the same
amount of information (data rate in bits per second) regardless of where in the radio frequency spectrum it is located, so
bandwidth is a measure of information-carrying capacity. The bandwidth required by a radio transmission depends on the
data rate of the information (modulation signal) being sent, and the spectral efficiency of the modulation method used; how
much data it can transmit in each kilohertz of bandwidth. Different types of information signals carried by radio have
different data rates. For example, a television (video) signal has a greater data rate than an audio signal
 regulations Audio: Radio broadcasting Digital radio
Digital radio involves a variety of standards and
Most radios can receive both AM and FM.
technologies for broadcasting digital radio signals over
• Two radio transmitters in the AM (amplitude modulation) – in AM, the the air. Some systems, such as HD Radio and DRM,
same area that attempt to amplitude (strength) of the radio carrier operate in the same wavebands as analog broadcasts,
transmit on the same frequency wave is varied by the audio signal. Because either as a replacement for analog stations or as a
will interfere with each other,
causing garbled reception, so waves in these bands travel as ground waves complementary service. Others, such as DAB/DAB+
neither transmission may be following the terrain, AM radio stations can and ISDB_Tsb, operate in wavebands traditionally
received clearly. be received beyond the horizon at hundreds used for television or satellite services.
• To prevent interference between of miles distance, but AM has lower fidelity
different users, the emission of
radio waves is strictly regulated than FM.
by national laws, coordinated by FM (frequency modulation) – in FM the
an international body which
allocates bands in the frequency of the radio carrier signal is varied
radio spectrum for different slightly by the audio signal.
uses.Radio transmitters must be
licensed by governments and are Radio waves in this band travel by
restricted to certain frequencies line-of-sight so FM reception is limited by the
and power levels.
visual horizon to about 30–40 mi (48–64 km),
• In some cases, such as radio and and can be blocked by hills. However it is less
television broadcasting stations,
the transmitter is given a unique susceptible to interference from radio noise (
identifier consisting of a string of RFI, sferics, static), and has higher fidelity,
letters and numbers called a better frequency response, and less
call sign, which must be used in
all transmissions. audio distortion than AM.
 Digital radio
• Digital radio involves a variety of standards and technologies for broadcasting digital radio signals over the air.
Some systems, such as HD Radio and DRM, operate in the same wavebands as analog broadcasts, either as a
replacement for analog stations or as a complementary service. Others, such as DAB/DAB+ and ISDB_Tsb,
operate in wavebands traditionally used for television or satellite services.

Micrwaves examples

• Microwaves are widely used in modern technology, for example in point-to-point communication
links, wireless networks, microwave radio relay networks, radar,
satellite and spacecraft communication, medical diathermy and cancer treatment, remote sensing
, radio astronomy, particle accelerators, spectroscopy, industrial heating,
collision avoidance systems, garage door openers and keyless entry systems, and for cooking food
in microwave ovens.
microwaves
• Microwave is a form of electromagnetic radiation with wavelengths shorter than other
radio waves (as originally discovered) but longer than infrared waves. Its wavelength ranges from
about one meter to one millimeter, corresponding to frequencies between 300 MHz and
300 GHz, broadly construed.[1][2][3][4][5][6] A more common definition in radio-frequency engineering
is the range between 1 and 100 GHz (wavelengths between 30 cm and 3 mm),[2] or between 1
and 3000 GHz (30 cm and 0.1 mm).[7][8] The prefix micro- in microwave is not meant to suggest a
wavelength in the micrometer range; rather, it indicates that microwaves are small (having
shorter wavelengths), compared to the radio waves used in prior radio technology.
• The boundaries between far infrared, terahertz radiation, microwaves, and ultra-high-frequency
(UHF) are fairly arbitrary and are used variously between different fields of study. In all cases,
microwaves include the entire super high frequency (SHF) band (3 to 30 GHz, or 10 to 1 cm) at
minimum. A broader definition includes UHF and extremely high frequency(EHF) (millimeter wave
; 30 to 300 GHz) bands as well.
Micro wave
for scientific research
• This band is commonly used in radio astronomy and remote sensing. Ground-
based radio astronomy is limited to high altitude sites such as Kitt Peak and
Atacama Large Millimeter Array (ALMA) due to atmospheric absorption issues.
• Satellite-based remote sensing near 60 GHz can determine temperature in the
upper atmosphere by measuring radiation emitted from oxygen molecules that is
a function of temperature and pressure. The
International Telecommunication Union non-exclusive passive frequency
allocation at 57–59.3 GHz is used for atmospheric monitoring in meteorological
and climate sensing applications and is important for these purposes due to the
properties of oxygen absorption and emission in Earth's atmosphere.
Microwave in telecommunication
• The Wi-Fi standards IEEE 802.11ad and IEEE 802.11ay operate in the 60 GHz (V band)
spectrum to achieve data transfer rates as high as 7 Gbit/s and at least 20 Gbit/s, respectively.
• Uses of the millimeter wave bands include point-to-point communications, intersatellite links,
and point-to-multipoint communications. In 2013 it was speculated that there were plans to
use millimeter waves in future 5G mobile phones.[10] In addition, use of millimeter wave bands
for vehicular communication is also emerging as an attractive solution to support
(semi-)autonomous vehicular communications.[11]
• Shorter wavelengths in this band permit the use of smaller antennas to achieve the same high
directivity and high gain as larger ones in lower bands. The immediate consequence of this
high directivity, coupled with the high free space loss at these frequencies, is the possibility of
a more efficient use of frequencies for point-to-multipoint applications.
• Since a greater number of highly directive antennas can be placed in a given area, the net
result is greater frequency reuse, and higher density of users. The high usable
channel capacity in this band might allow it to serve some applications that would otherwise
use fiber-optic communication or very short links such as for the interconnect of circuit
boards.[12]
 Difference btw micro and radio
charecteristics Radio wave microwave
Wavelength range Greater than 0.1 m Lies between 0.1 to 1mm

Generation Rapid acceleration and deceleration of electrons

Detection Receivers aerials Point contact diodes

Properties Has a low frequency and low energy. Contain high frequency and high energy.

Wave can travel in All directions Single (Unidirectional)

Applications AM, FM and cellular systems. Radar system, aircraft navigation and microwave
oven.