Talk:Continuous-wave radar

Comment

Continuous wave doppler radar is a special purpose radar which sends out continuous sine waves and uses doppler effect to detect the frequency change by a moving target.The relative velocity of the target is displayed on an indicator. The apparent frequency of electromagnetic waves depends on the relative radial motion of the source and the observer.If the source and the observer are moving away from each other,the apparent frequency will decrease.If they are moving toward each other,the apparent frequency will increase.This is the doppler effect.

  Expression for the doppler frequency......
         Fd =2Vr/wavelength

Merge Frequency-modulated continuous-wave radar here

The article FMCW (for Frequency-modulated continuous-wave radar) is redundant with the portion of this article talking about the same subject. The Continuous-wave radar is a more general concept and should be the only one kept, adding information from FMCW.

Pierre cb (talk) 15:04, 4 August 2012 (UTC)

Yes, please do. Dicklyon (talk) 15:56, 4 August 2012 (UTC)

I vote for merge K5okc (talk) 17:33, 4 August 2012 (UTC)

Agree, per nominator. Debresser (talk) 20:24, 4 August 2012 (UTC)

 Done Merger done Pierre cb (talk) 17:36, 7 August 2012 (UTC)

The merge looks good, but there are fundamental problems that seem to be a result of restricting coverage to altimeters, police radar, and sporting goods. First - The frequency modulation technique that is shown uses sawtooth FM, which only works on simple reflectors. Non-linear modulation cannot reliably range propellers and fan turbines because multiple reflectors create modulation artifacts, and that corrupts the reflected spectrum for most conventional aircraft. Military systems use sinusoidal modulation with corresponding demodulation in the receiver that uses several cycles that permits simultaneous ranging for multiple discrete objects. Blade modulation artifacts and multiple reflectors can be separated when linear modulation is used (sinusoidal FM). Range is determined by identifying the sinusoidal modulation index of each spectral region that break the CFAR threshold. The article fails to mention the limitations section corresponds to the specific modulation technique described in the article. Second - CWAT utilizes an antenna that acquires energy density measurement and phase measurements in the side lobe region, and range demodulators for at least 5 receivers must be slaved to the main beam (monopulse). This provides angular offset perpendicular to the centerline of the receive antenna, including side lobe rejection required for reliable operation. Third - CW radars cannot work without removing the bleed over from the transmitter that leaks into the receiver and overwhelms target reflections. Over 100dB of rejection is required for operation beyond 1 kilometer, which cannot be achieved in cheap systems that lack bleed-over compensation. That rejection can only be achieved by interrupting the carrier in cheap systems that restricts the system to resolving single reflectors, which the article lumps in with pure CW radar systems. The article omits all other bleed-over compensation techniques, like filters and other approaches. Fourth - the article states there is no way to range more than one object simultaneously, which is simply not true. Common anti-personnel CW radar have been doing this for decades. Bistatic CW radar has been used to measure range without FM modulation, which associated with another false statement. These are system-specific design flaws imposed by modulation and receiver architecture peculiar to each manufacturer (i.e.: information picked up from sales material, technical manuals, or similar sources). I will address some those weaknesses if nobody objects, but I thought some of those topics had already been addressed in the existing CWAT article. I would hope these changes would not be removed if I go to the trouble of improving the quality.Nanoatzin (talk) 00:46, 13 August 2012 (UTC)

maximize total power

Section Continuous-wave_radar#Operation states:

"Continuous-wave radar maximize total power on a target because the transmitter is broadcasting continuously."

For me this sounds like marketing speech and either unprecise or technically incorrect. I guess the author intended to say something like this:

"Eventhough continuous-wave radar typically transmits with lower power than pulse radar it can transmit with higher energy because the transmitter is broadcasting continuously."

I am not radar expert, but if I am right, please correct the article accordingly. Otherwise, I would like to know what is meant with "total power"? Is it Energy (i.e., power integrated over time)? Or is it total over frequency domain? Or is it summed up over several amplifiers? Or what? Moreover, I do not understand the meaning of "maximized" in this context. What are the variables and constraints of the optimization problem resulting in "maximum total power"? --85.181.131.170 (talk) 13:34, 8 January 2016 (UTC)

Continuous wave radars aren't just doppler radars.

From the lede:

"Individual objects are detected using the Doppler effect, which causes the received signal to have a different frequency than the transmission, allowing it to be detected by filtering out the transmitted frequency.

As this process also filters out slow or non-moving objects, it renders the radar immune to interference from large stationary objects and slow-moving clutter."

This isn't the case for all CW radars, many of them just measure the backscatter from the field of view (from which the presence of an object can be inferred). I've therefore made it clear that doppler-operation is one potential mode of operation, rather than the general case.

To be honest I'm not sure whether that bit about Doppler shift belongs in the lede at all (given it's not an intrinsic part of CW radar), but I'll wait a bit before moving it to see if people disagree.

--Robbie Mallett (talk) 14:38, 13 November 2020 (UTC)