Doppler Radar - Bandwidth, Continuous Wave or Pulse?

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Discussion Overview

The discussion centers on Doppler radar, specifically addressing questions about its bandwidth and whether it typically operates as a continuous wave or in pulses. Participants seek general knowledge about the operational principles and variations of Doppler radar systems.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • One participant inquires about the bandwidth of Doppler radar and whether it operates as a continuous wave or in pulses, suggesting uncertainty about its general characteristics.
  • Another participant asserts that Doppler radars primarily send brief pulses, explaining that the transmitter must be off to detect incoming signals, likening it to yelling into a canyon and waiting for the echo.
  • A different participant adds that the radar's ability to detect distances is influenced by the transmit pulse duration, repetition rate, and output power, indicating a technical understanding of radar operation.
  • A later reply reiterates the inquiry about Doppler radar's operational modes, stating that older vehicle speed radars typically use continuous wave signals but turn off the transmitter during the reception period, which results in long pulses. This participant also mentions newer radars that can utilize short pulses and discusses the use of Lidar.

Areas of Agreement / Disagreement

Participants express differing views on the operational modes of Doppler radar, with some asserting that it primarily uses pulses while others mention the use of continuous wave systems, indicating that multiple competing views remain without a consensus.

Contextual Notes

Participants reference various operational characteristics of Doppler radar, but there are limitations in the discussion regarding specific definitions of bandwidth and the conditions under which different radar types are used. The discussion does not resolve the nuances of these technical aspects.

imonthejazz
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Doppler Radar??

Please can someone help me with doppler radar...need to know bandwidth?? Is it usually continuous wave or pulse?? or can it be both??

pretty much just after some general knowledge on doppler radar?

thanks in advance!
 
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As far as I know, the only Doppler radars in use send brief pulses. The transmitter has to be off in order for the receiver to detect an incoming signal (the way you or I might yell into a canyon, then be quiet to hear the echo).
 
As far as I know about radar and radio in general, unless you have two separate antennas one each exclusively for transmit and receive, the transmitter of the radar has to be stopped so it can "see" the return echo on the same antenna.

The min and max distances you can see with a radar are a function of the transmit pulse duration, repetition rate and output power.
 


imonthejazz said:
Please can someone help me with doppler radar...need to know bandwidth?? Is it usually continuous wave or pulse?? or can it be both??

pretty much just after some general knowledge on doppler radar?

thanks in advance!

The doppler radars used for measuring vehicle speed (older ones) send out a CW wave of a single frequency. They do turn it off for the reception period as noted above --- so those are generally long pulses. Similar to morse code for Ham Radio operators -- the returning frequency is "mixed" with the original frequency -- and the difference in frequency is measured. The difference is proportional to speed.

I have read that newer radars can use short pulses (and then there is Lidar). The difference in time in the return pulses from one pulse to the next can be measured and used to compute speed. I don't know how common the one or the other gun is today.
 

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