[SOLVED] Why phase noise is generally seen at 100 Hz offset in RADAR applications ?

[shashy.br]

I need to know why the phase noise of oscillators are generally seen at 100 Hz offset from the carrier ?
is there any reason for the measurement at this frequency offset in RADAR application?:?:

 

[E-design]

Depends what is important in which application. Some time and frequency applications require tight specifications at 1Hz offset.

 

[shashy.br]

The 100Hz offset is cruisual for a ground based RADAR application since it must must detect stationary objects also in some cases,

hence the doppler shift for a stationary object nearer to a RADAR is in 30 to 100 Hz range , Hence to detect these reflected waves the phase noise at this point of the Local oscillator needs to be very pure.

 

[biff44]

you must be talking about weather radars, where very small doppler speeds (i.e. wind speeds) are being measured. Any sort of moving objects will have a much bigger doppler frequency shift, and then the phase noise at 100 Hz is not very important.

 

[pstuckey]

Doppler shift is given by:

Doppler = Target Velocity * RADAR frequency / speed of light

For instance, at x-band (10 GHz), 100 Hz doppler is caused by velocity of only 3 m/s (a person walking quickly).