2016年11月29日 · I found by Knott (The Radar Handbook, chapter 11)- "The echo characteristics depend in strong measure on the size and nature of the target surfaces exposed to the radar beam. The variation is small for electrically small targets (targets less than a wavelength in size) because the incident wavelength is too long to resolve target details."

An object many times smaller than the wavelength can still cause scattering or absorption, so it would create a detectable change to the incident beam of light, which is all we need for detection. The quantum efficiency (what fraction of photons are scattered) will be small, but as long as a few are, the particle is detectable. Think of the ...

2023年11月7日 · Advanced photodetectors have a significant probability of detecting an individual photon. But IR has a lot more energy per photon than radar. radar? angular resolution: Radar, being longer wavelength, gives a much lower angular resolution for the same aperture: IR, being much shorter wavelength, gives a higher angular resolution: infrared ...

For that reason many RADAR’s in use for obstacle detection will be “high frequency” so that the wavelength is shorter (hence why we often use mm-wave in robotics) and can detect smaller objects." This does provide some intuitive understanding as to why devices emitting higher frequency signals provide high-resolution data.

2019年2月28日 · Narrow beams pick up less RFI for example. With a lower noise floor, weaker signals can be detected, which means that for a fixed range, objects with a smaller radar cross section may be observed. Keep in mind however, that radar cross section is not the same as physical cross section, but is the term used when dealing with radars.

2022年12月10日 · Interference can redirect energy, but it cannot absorb it. So, you must back your coating with some sort of absorber. Then, the behavior depends on wavelength and geometry. It works better to use an absorber straight, without extra complication.

This results in a wavelength $\lambda_0$ of $\frac{c}{f_0}$ ... This wavelength is then observed by the ...

2021年2月13日 · Radar sensors make use of the Doppler effect to measure the radial velocity of an object. The radar's Tx antennas emit an electromagnetic wave which travels to the moving objects, is reflected and the radar's Rx antennas detect the incident wave. Due to the movement of the measured object, the received wave has a different frequency.

2020年9月10日 · But so far I don’t really see or understand why the limit of resolution should be half the wavelength? Am I missing something? Edit: So I googled common microscope apertures and found that they are mostly in the range of 1.0 to 1.35 and so this would very roughly approximate the constant 0.66/N.A to 0.5. So indeed the maths makes it work out.

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