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To: TXnMA

The most popular radar waveform is “linear frequency modulation”, LFM, in which the frequency increases linearly with time. For instance, the frequency of a one millisecond pulse might start at 3200 MHz and finish at 3201 MHz, increasing linearly throughout. This form of modulation gives you the energy of a one millisecond pulse, and the range resolution of a one microsecond pulse.


19 posted on 12/28/2016 8:30:04 PM PST by Lonesome in Massachussets (Psephomancers for Hillary!)
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To: Lonesome in Massachussets; Tucker39; Steely Tom
I'm bandwidth-starved" by my lousy satellite ISP. But, I guess I better watch the video -- in hopes they will show the received signal's waveform envelope.

L-I-M, as I understand your RADAR description, the carrier was sinusoidal -- linearly frequency-swept (modulated) over a 1MHz range by a 1KHz "sawtooth" signal. Every millisecond, the modulation frequency would reach peak, then instantly drop back 1 MHz, and begin its sweep again... (IOW, I'd guess that early RADARs were modulated by a VCO -- driven by a relaxation oscillator-generated sawtooth...)

OTOH, a point source on a rapidly-spinning sphere -- Doppler-modulated by the angular velocity -- would sinusoidally reach a peak frequency, and sinusoidally drop back to minimum. Then, with the signal occluded by the object, the signal would be attenuated (below detectable level) for half a revolution, and then the half-sinewave signal would reappear. (Basically a frequency-modulated signal, driven by a half-rectified sine wave...)

Going to go "bomb" my bandwidth allocation, watch the video, hope for a look at the actual signal, and -- I hope -- stop speculating... '-)

Back soon...

29 posted on 12/29/2016 9:17:21 AM PST by TXnMA ("Allah": Satan's current alias. "Barack": Allah's current ally. "Comey" Barack's current toadie...)
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