Doppler Radar - Bandwidth, Continuous Wave or Pulse?

[imonthejazz]

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!

 

[LURCH]

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).

 

[Francis M]

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.

 

[andrewr]

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.