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Old 11-17-2019, 08:48 PM   #11
Kev2go
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Besides what Klarsnow said (which imo is overall the best answer)

il also throw in that various sources also state MPRF is also superior for all aspect detection and tracking. AWG9 as i have read is also not as good as the AN/APG63 in detecting targets in the sides and rear aspects.

True in AWG9 Pulse Mode you have all around better all aspect performance in the tomcat relative to other radar modes, but as we know without the Doppler filters the basic pulse mode it will be very prone to ground clutter reflections. In that mode you may as well have flying with a larger F4E radar.
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Old 11-18-2019, 12:24 AM   #12
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Quote:
Originally Posted by drPhibes View Post
A bank of analog bandpass filters.
Can you point me to how that works? It can have math and suff in it . How are those filters geting time domain info from the freq shift without fft?
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Old 11-18-2019, 03:49 AM   #13
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Quote:
Originally Posted by Harlikwin View Post
Can you point me to how that works? It can have math and suff in it . How are those filters geting time domain info from the freq shift without fft?
First off, it isn't a band-pass filter, it's a band-reject filter. Also called a 'notch' filter (hence the term). There would be two notch filters: One set to exactly the radar frequency, and one varied based on the aircaft's calculated ground-speed. The former is used for sidelobe clutter and self-noise filtering, and is always on. The latter would be used for main-lobe clutter rejection. The idea is that the doppler shift would need to be enough to cause the return's frequency to be outside the notch filters' range in order to make it to the signal processor.
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Old 11-18-2019, 04:59 PM   #14
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Quote:
Originally Posted by Hyena View Post
First off, it isn't a band-pass filter, it's a band-reject filter. Also called a 'notch' filter (hence the term). There would be two notch filters: One set to exactly the radar frequency, and one varied based on the aircaft's calculated ground-speed. The former is used for sidelobe clutter and self-noise filtering, and is always on. The latter would be used for main-lobe clutter rejection. The idea is that the doppler shift would need to be enough to cause the return's frequency to be outside the notch filters' range in order to make it to the signal processor.
How would vary the filter freq based on aircraft velocity? I mean the velocity could be anywhere from 150-900kts.
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Old 11-18-2019, 09:08 PM   #15
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The MLC filter frequency is simply ground speed from the INS fed into this:

I assume the bandwidth of +/-133 kts of own speed is to compensate for the limited accuracy of the INS.
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Old 11-18-2019, 09:25 PM   #16
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I guess i was asking how you geta a analog variable freq filter.
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Old 11-18-2019, 09:46 PM   #17
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Variable capacitors and resistors I imagine? At its very core one does not need a complex circuit to get something like that
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Old 11-18-2019, 10:12 PM   #18
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Take an analog parametric EQ and swap the frequency potentiometer for a transistor driven by the doppler frequency solver.
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Old 11-18-2019, 11:07 PM   #19
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Or, as previously written, have a bank of notch filters. Then you basically get the same as when doing a DFT. Each of the filter will be a frequency bin and the output of the filter still has amplitude and phase information.
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Old 11-19-2019, 06:15 PM   #20
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I have a hunch that most of the AF guys were talking about the lack of medium PRF in the AWG-9 system, which can really improve performance over land and against retreating bandits. (as stated by Kev above)
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