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RAdio Detection And Ranging (RADAR)

Radar was initially developed in the early 1900's as a technique to measure distance, direction, and speed of objects by transmitting pulses of high-frequency electromagnetic waves. These electromagnetic waves reflect off the object and back to its source. The time it takes the electromagnetic wave to return to its source is translated into a distance to the object.

How RADAR Works

  1.  The Radar system generates an electromagnetic (EM) pulse that is focused by an antenna, and then transmitted through the atmosphere. 
  2. Objects in the path of the transmitted EM pulse scatter most of the energy, but some will be reflected back toward the radar.
  3. The receiving antenna gathers back-scattered radiation and feeds it to a "receiver."
  4. An EM pulse encountering a target is scattered in all directions. The larger the target, the stronger the scattered signal.
  5. The radar measures the returned signal, generally called the "reflectivity." Reflectivity magnitude is related to the number and size of the targets encountered.

Taken from National Oceanic and Atmospheric Administration

There is a tremendous amount of information about radar available on the internet and in text books. Below is a list to some of our favorite radar sites and text books.

Websites:

Radar Tutorial
NOAA
Novelda

Text Books:

Fundamentals of radar signal processing (Richards)
Principles of Modern Radar (Volumes 1 & 2, Assorted editors)
MTI and Pulsed Doppler Radar with Matlab (Schleher)
Radar Handbook (Skolnik)

About Ultra Wide Band Radar

Many of the radar sensors used at Flat Earth are consider Ultra Wide Band (UWB) Radar and span the frequency range 0.75 GHz to 11 GHz. UWB radar sensors use a very low energy level for short-range, high-bandwidth communications over a large portion of the radio spectrum. UWB radar can be used in applications such as radar imaging, target sensor data collection, precision locating and tracking applications.

Flat Earth uses Novelda Xe Thru UWB radar technology in many of our applications. Xe Thru Radar is a complete radar transceiver integrated on a single chip. The high bandwidth of the transmitted pulses offers unique penetration abilities and very high accuracy.  Xe Thru radar can receive reflections from hidden objects like the heart in the human body or an object hidden behind an obstacle. This makes Xe Thru radar sensors particularly suitable for applications where light-based sensors fall short, such as through-the-wall detectors and in dark or dirty environments.

Radar Demonstrations 

Ranging to a Single Object – using a single radar sensor and antenna pair we can range to a single object. You can determine range to object with high accuracy (<cm) but you can not determine the direction to the object. Additional radar chips or antenna pairs is required to determine the direction to an object. 

Video Demo #1 Ranging to a Single Object

2D Positioning to a Single Target

By adding a second radar sensor with antenna pair we can measure the range (distance) and direction to a single object.  Demo #2 show the ability to track a ball in 2 dimensions.

Video Demo #2 2D Positioning to a Single Object

Because of the high accuracy over a short range, UWB radar can track small objects quite well. In Demo #3 we show the radar sensitivity by tracking a human finger.

Video Demo #3 2D Positioning of a Finger

Xe Thru radar has the ability to penetrate many types of materials including fabrics, construction materials, walls, and in to the earth. In Demo #4 we show how the radar can track an object through a sheet of glass. In demo #5 we demonstrate how the radar can track a single object through heavy clothing.

Video Demo #4 2D Positioning Through Glass

Video Demo #5 2D Positioning Through Heavy Clothing

3D Positioning and Tracking

By adding a third radar sensor and antenna pair we can begin tracking objects in 3 Dimensions. Video Demo #6 show how synchronizing 3 radar development kits we can track an object in 3 dimensions. 

Video Demo #6 3D Positioning and Tracking of a Single Object

Utilizing the Doppler effect we can produce distance and velocity data of an object. Video Demo #7 demonstrates Doppler tracking of a single object. Video Demo #8 demonstrates tracking two object using Doppler techniques.

Video Demo #7 Tracking Single Object using Doppler Techniques

Video Demo #8 Tracking Two Objects using Doppler Techniques 

With three synchronized Flat Earth development kits we can also track multiple targets in three dimension. Video #9 demonstrates tracking two objects in three dimensions.


Video Demo #9 Tracking Two Objects in Three Dimensions