• Marine radars are used to measure the bearing and distance of ships to prevent collision with other ships, to navigate and BASIC ELECTRONICS to fix their position at sea when within range of shore or other fixed references such as islands ,buoys , and lightships. TITLE: RADAR AND ANTENNA Brightness can indicate reflectivity as in this 1960 weather radar image (of Hurricane Abby). The radars frequency, pulse form, polarization, signal processing, and antenna determine what it can observe.
What is radar?• An object-detection system which uses electromagnetic waves specifically radio waves to determine the range, altitude, direction, or speed of both moving and fixed objects such as aircraft, ships, spacecraft• Transmits pulses of radio waves or microwaves which bounce off any object in their path.• The object returns a tiny part of the waves energy to a dish or antenna which is usually located at the same site as the transmitter.
Basic radar operation• Light waves, radio waves, microwaves, radar waves is electromagnetic waves.• Unlike water waves, electromagnetic waves do not require a medium such as water or air to travel through. They can travel through a complete vacuum.• Similar to light waves, radar waves bounce off some objects and travel through others.• The simplest mode of radar operation is determining how far away an object is. The radar unit sends radar waves out toward the target . The waves hit the target and are reflected back.
• The returning wave is received by the radar unit and the travel time is registered.• According to basic principles of physics, distance is equal to the rate of travel (speed) multiplied by the time of travel.• All electromagnetic waves travel at the same speed in a vacuum—the speed of light which is 186,282 miles (299,727 kilometers) per second. This speed is reduced by a small amount when the waves are traveling through air but this can be calculated.
The USES of radar• Modern uses of radar are highly diverse including • air traffic control, radar astronomy, air- defense systems, antimissile systems like nautical radars to locate landmarks and other ships, aircraft anti-collision systems for ocean-surveillance systems, meteorological precipitation monitoring, altimetry and flight-control systems, guided-missile target-locating systems and ground-penetrating radar for geological observations.• High tech radar systems are associated with digital signal processing and are capable of
• ALTAIR - used to detect and track space objects in conjunction with ABM testing at the Ronald ReaganTest Site on Kwajalein Atoll. » Israeli military radar is typical of the type of radar used for air traffic control. The antenna rotates at a steady rate, sweeping the local airspace with a narrow vertical fan-shaped beam, to detect aircraft at all altitudes.• This Melbourne base Primary and secondary radaris used for air traffic control and to observe terminalarea conflicts by VFR local aircraft.
WHAT IS ANTENNA?An electrical device whichconverts electric currentinto radio waves, and vice versa.
antenna• Also contain reflective or directive elements or surfaces not connected to the transmitter or receiver, such as parasitic elements, parabolic reflectors or horns, which serve to direct the radio waves into a beam or other desired radiation pattern.
THE HISTORY ANDDEVELOPMENT OF ANTENNA First experiments Involved the coupling of electricity and magnetism and showed a definitive relationship was that done by Faraday somewhere around 1830s Creating a time-varying magnetic field, which as a result (from Maxwell’s
The coil acted as a loop antenna and received the electromagnetic radiation, which was received (detected) by the galvanometer- the work of antenna.
First antenna Built in 1888 by German physicist Heinrich Hertz in his pioneering experiments To prove the existence of electromagnetic waves predicted by the theory of James Clerk Maxwell Developed a wireless communication system in which he forced an electrical spark to occur in the gap of a dipole antenna.
He used a loop antenna as receiver, and observed a similar disturbance This was 1886. Hertz placed dipole antennas at the focal point of parabolic reflector for both transmitting and receiving.
By 1901, Marconi was sending information across the Atlantic. For a transmit antenna, he used several vertical wires attached to the ground. In 1901, Columbia University had an Experimental Wireless Station There are several discovered antennas :
Yagi-Uda Antenna (1920s)It is simple to construct and has a high gain, typically greater than 10dBoperate in the HF and UHF bands ( about 3MHz to 3GHz)The Yagi antenna was invented in Japan done by Shintaro UdaPresented for the first time in English by Yagi at America
Horn Antenna (1939)At UHF (300 MHz-3GHz) and higher frequencies will achieved to 140 GHz.Can range up to 25dB in some cases
Antenna Arrays (1940s)• Often called a ‘phased array’ is asset of 2 or more antennas• The signals from the antennas are combined or processed in order to achieve improved performance
Parabolic reflectors (late 1940) Commonly known as satellite dish antenna (30-40 dB is common) and low cross polarization Huge dishes( which can operate from 150 MHz to 1.5 GHz) Smaller dish antenna typically operate between 2-28 GHz The feed antenna is often a Horn antenna with a circular aperture
Patch Antenna (1970s)• It printed directly onto a circuit board.• low cost, have a low profile and are easily fabricated
PIFA (1980) The quarter-wavelength Patch Antenna, which leads into the Planar Inverted-F antenna (PIFA). The patch is shorted at the end Has the same current-voltage distribution as a half-wave patch antenna reduced in size 50%.
THE USE OF ANTENNA• Radio broadcasting A one-way wireless transmission over radio wave intended to reach a wide audience. The signal types can be either analog or digital audio.
• Broadcast television A mode of television broadcasting which does not involve satellite transmission or cables which is typically using radio waves through transmitting and receiving antennas or television antenna aerials
• Two-way radio A radio that can both transmit and receive (a transceiver), unlike a broadcast receiver which only receives content
• Communication receiver A type of radio receiver used as a component of a radio communication link
• Cell phone A device which can make and receive telephone calls over a radio link whilst moving around a wide geographic area. It does so by connecting to a cellular network provided by a mobile network operator
• Satellite communication An artificial satellite stationed in space for the purpose of telecommunication They are also used for mobile applications such as communications to ships, vehicles, planes and hand-held terminals, and for TV and radio broadcasting, for which application of other technologies
• Wireless microphone A microphone without a physical cable connecting it directly to the sound recording or amplifying equipment with which it is associated
• Wireless computer network A wireless local area network (WLAN) links two or more devices using some wireless distribution method (typically spread-spectrum or OFDM radio), and usually providing a connection through an access point to the wider internet