Everything from your house electricity to cosmic rays involves electromagnetic energy. There is electromagnetic radiation bathing us all the time from your electric blanket to TV to cellphones to radioactive decay of the bricks in your house to cosmic rays. Each has its own characteristic oscillation frequency and corresponding wavelength related by the velocity of light. Figure 2.1 shows much of the electromagnetic spectrum including the general location of frequency and source of emissions in that band. In addition the energy per photon increases as the wavelength gets shorter. So even though it is easy to feel those big fat photons coming out of an open fire or oven, the much shorter wavelengths have far more energy to penetrate most materials. Nonetheless, all of these wavelengths can carry significant energy. Radars are limited in the same way as your eye but, with significant signal processing and high signal to noise and interference ratios (SNIR), dramatic improvements in accuracy and acuity can be achieved. This is enabled by use of coherent processing not available to the naked eye.

Chapter Contents:

• 2.1 Basic principles
• 2.2 Basic radar
• 2.3 The matched filter notion
• 2.4 Fourier transform
• 2.5 Decibel notation
• 2.6 Antenna principles
• 2.6.1 Active electronic scan antennas (AESA)
• 2.6.2 Antenna Example 2.2
• 2.7 Multichannel receivers
• 2.8 Measuring the distance to a scatterer in wavelengths and the Doppler effect
• 2.9 Pulse Doppler
• 2.10 Radar equation
• 2.11 Pulse compression
• 2.11.1 Radar equation Example 2.4
• 2.12 Radar surface returns
• 2.13 Ambiguities and folding
• 2.14 Range and Doppler resolution
• 2.14.1 High-resolution mapping Example 2.5
• 2.15 Elements of geolocation
• 2.15.1 Radar antenna pointing Example 2.6
• References

Inspec keywords: radar signal processing

Other keywords: energy per photon; cosmic rays; cellphones; electromagnetic energy; electric blanket; electromagnetic spectrum; SNIR; electromagnetic radiation; coherent processing; TV; signal processing; coherent radars; characteristic oscillation frequency; signal to noise and interference ratios

Subjects: Radar equipment, systems and applications; Signal processing and detection