For ideal case, the directivity of an antenna equals to 1, indicating no loss. However, in real situation, antenna’s gain is less than directivity. Directivity Directivity relates radiation intensity in a given direction in terms of the average radiation intensity in all directions. D(θ,∅)=U(θ,∅)/U_av =4π U(θ,∅)/P_rad Where D(θ,∅) is the directivity of the antenna U(θ,∅) is the radiation intensity in a given direction (W/unit solid angle) Uav is the average radiation intensity over all directions (W/unit solid
INTRODUCTION 1.1 Overview of Radar The word RADAR is an acronym coined in 1942 by U.S Navy for RAdio Detection And Ranging whose principle of operation is if an electromagnetic wave encounters sudden change in conductivity, permittivity or permeability in the medium, a part of the electromagnetic energy gets absorbed by the second medium and is re-radiated. Radar was originally developed to satisfy the needs of the military for surveillance and weapon control. Radar is an electronic sensor for the detection and location of reflecting objects. Radar radiates electromagnetic energy from an antenna to propagate in space. Some of the radiated energy is intercepted by a reflecting object, usually called a target, located at a distance from radar.
And finds the presence, location, and velocity of such objects and radar can find their size and shape as well. Principle of operation Radar works similar to principle of sound wave reflection. Radar uses electromagnetic energy pulses and radio frequency energy is transmitted and reflected from reflecting object a small portion of the reflected energy returns to radar the returned energy is called ECHO just it was in sound terminology radar sets uses echo to find the direction and distance of reflecting object Transmitter radar transmitter generates some short duration and high-power rf pulses energy that are into space by antenna. Transmitter is not too large in size and weight and it has wide band width and high power. Duplexer The duplexer alternately switches
Contrast i. Wavelength of radiation The range of visible light is 400-700nm. Different rays have different wavelengths as shown in fig 1. So, before the experimentation one should know the specific wavelength of a particular radiation ii. Light refraction and image magnification Light is refracted when it enters from a medium of light into glass. When a light bends while passing through a lens, then light rays are focused at a point that particular point is known as Focal point and due to which a larger image of the object is observed.
Primary Surveillance radar Secondary Surveillance Radar Primary surveillance radar uses the common principle of newtons third law by sending a narrow beam of energy which upon reflection from the aircraft under surveillance is collected back by receiver radar. The time taken for the transmission of radar pulse and the received echo will helps in finding the distance of the object. Secondary Surveillance Radar It worked on the coded reply from the airborne radio beacon Transponder located in aircraft which is the response to the interrogation sent from the ground station. RADAR principle The electronic principle on which the radar works is very similar to the principle of sound wave reflection. As the sound wave reflection principle says if u shout in the direction of sound reflecting object the echo reflected sound is heared.
Introduction The cross product of two vectors can be defined as the binary operation that is done on the two vectors in the three dimensional space. This operation is defined by the symbol ×. If the two vectors, suppose a and b are perpendicular to each other than their product will be also a vector quantity. Also this true for the normal plane containing these vectors. Cross product has many applications in engineering, physics and mathematics.
For example, for a plastic target an capacitive or photoelectric sensor might be suitable; an inductive proximity sensor always requires a metal target. The maximum distance that can be detected by the sensor is known as "nominal range". Some of these sensors that have adjustments to the nominal range or means to report a graduated detection distance. This is known as "thermosensation". Sensors which are generally used in detecting ferrous targets, ideally mild steel thicker than one millimeter are called inductive or non-contact proximity sensors.
It can also be derived from the impedances: VSWR = (1+ )/(1- ) Fig. 6.1.2 VSWR Plot for Antenna Configuration 1 6.1.3 Smith Plot: The scattering matrix is a mathematical construct that quantifies how RF energy propagates through a multi-port network. The S-matrix is what allows us to accurately describe the properties of incredibly complicated networks as simple "black boxes". For an RF signal incident on one port. The same is being shown here in the manner of Smith Plot.
They are used in satellite remote sensing for measurements of the earth 's land and sea surface temperature The most commonly used microwave imaging sensor is the Synthetic Aperture Radar (SAR) that is a radar system capable of providing high-resolution microwave images. They have distinctive characteristics compared to common optical images acquired in the visible or infrared bands; for this reason, radar and optical data can be complementary, as they carry on a different informative