Police radars transmit a microwave signal and receive reflections simultaneously. The microwave radiates in a cone shaped beam that varies with model from 9° to 18°. Most of the microwave misses the target, and most of the target reflection is directed away from the radar.
The scenario below is an optimum setup, radar close to traffic lanes, and the radar antenna beam angled to maximize coverage. The below radar has a 12° beamwidth that is angled 6° down-the-road.
Reflections from moving objects have a slight frequency difference from the transmit signal, this phenomena is called the Doppler Effect or Shift. The difference is based on target speed, the greater the speed the greater the frequency difference. This difference can be converted to miles per hour or kilometers per hour or knots, etc. Reflections from the ground and stationary objects are not frequency shifted.
Detection range varies with target size, shape, and reflectivity. Other factors include radar frequency and power, angle to the target, antenna factors, and weather conditions.
RADAR / LIDAR
Police Traffic Radar -- types of radar and lidar.
Tuning Forks -- daily microwave radar test.
Cosine Error -- applies to radar and iidar.
Radar Test Results -- US DOT report summary.
RF (Radio Frequency) and MICROWAVES
Frequency Bands -- Radar and Radio Bands.
Electromagnetic Waves -- Frequency, Wavelength, Power.
RF Biological Effects -- Non-Ionizing / Ionizing Radiation.
Radiation Standards -- ANSI and IEEE Standards.
Digital TV -- Over-the-air DTV broadcast (free TV).
ON THE ROAD AGAIN
Police 10 Codes
Red Light Cameras -- use radar or road sensors
Universal Time (UTC)
Radar Range Equations
Early Vehicle Radar
Radar Specifications Archive
Lidar Specifications Archive
LIDAR (Laser Radar)
Police lidars (Laser Radars) transmit pulsed infrared (IR) laser radiation to measured range. The IR pulse travel time (at the speed of light) between lidar and target and back is used to determine range. The target change in range during 0.3 seconds (or more) is used to calculate speed. Lidars have very narrow beams, just under 0.2°. Practical range is limited to about 500 feet (150 yards).
Police radars and lidars are not just point (at target) and click (transmit) devices. There are some basic setup limitations and operating procedures that must be observed. Too often procedures are not properly followed in order to save a little time or hide from motorists, resulting in speed errors. Additionally, far too many operators don't remember, or don't use, what they were taught in radar training.
Radars can and do make mistakes, even when properly setup.
CopRadar Video Channel
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PublicationsPolice Radar Basics (Table of Contents)
Everything Every Driver, and the Police, should know about Traffic Speed Radar
Book | Kindle
Police Radar Operator Error (Table of Contents)
Microwave and Laser Radar Protocols and Results of Improper Use
Book | Kindle | iPad
Police Radar Handbook (Table of Contents)
A Comprehensive Guide to Speed Measuring Systems
Book | Kindle