# Radar questions

**URL:** <https://boards.straightdope.com/t/radar-questions/714632>\
**Category:** Factual Questions\
**Created:** [March 9, 2015, 8:20pm UTC](https://boards.straightdope.com/t/radar-questions/714632 "2015-03-09T20:20:40Z")\
**Posts on this page:** 2\
**Page:** 2

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**Author:** ![MichaelEmouse](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/michaelemouse/32/101_2.png) [@MichaelEmouse](https://boards.straightdope.com/u/MichaelEmouse)\
**Post date:** [March 17, 2015, 8:29pm UTC](https://boards.straightdope.com/t/radar-questions/714632/21 "2015-03-17T20:29:47Z")

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Thanks for the book recommendation, I’ve ordered it.  
I have some questions which I think may be too context-dependent to be covered in a primer.  
When a target is getting light up by a radar, does it look like jamming from the target’s perspective? That is, does the target know the general direction of the radar but not its range, altitude or precise location?  
A big trade-off when it comes to radars is the detection threshold, right? If you set it too high, you’ll miss real targets. If you set it too low, you’ll get too much noise, too many false targets, correct?

With enough processing power, would it eventually be possible to set the detection threshold quite low and let very power computers figure it out reliably enough?

The delay between sending and receiving the signal is quite low, at most hundreds of seconds. What about the processing? Can that take much longer in military applications?

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**Author:** ![engineer\_comp\_geek](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/engineer_comp_geek/32/504_2.png) [@engineer\_comp\_geek](https://boards.straightdope.com/u/engineer_comp_geek)\
**Post date:** [March 17, 2015, 10:59pm UTC](https://boards.straightdope.com/t/radar-questions/714632/22 "2015-03-17T22:59:51Z")

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> [@MichaelEmouse](#):
>
> With enough processing power, would it eventually be possible to set the detection threshold quite low and let very power computers figure it out reliably enough?
> 
> The delay between sending and receiving the signal is quite low, at most hundreds of seconds. What about the processing? Can that take much longer in military applications?

I can’t answer the first part of your question, but the processing of radar signals these days is done digitally. The main processing algorithm is called a Fast Fourier Transform (FFT) and all kinds of extra processing is done to the signals to reduce clutter and help pick out the target. The signal processing is very fast.

Here’s some links that you may find interesting, though the FFT page gets a bit hairy on the math:

> **[Pulse-Doppler signal processing](https://en.wikipedia.org/wiki/Pulse-Doppler_signal_processing)**
>
> Pulse-Doppler signal processing is a radar and CEUS performance enhancement strategy that allows small high-speed objects to be detected in close proximity to large slow moving objects. Detection improvements on the order of 1,000,000:1 are common. Small fast moving objects can be identified close to terrain, near the sea surface, and inside storms.
> This signal processing strategy is used in pulse-Doppler radar and multi-mode radar, which can then be pointed into regions containing a large numbe...

> **[Fast Fourier transform](https://en.wikipedia.org/wiki/Fast_Fourier_transform)**
>
> A fast Fourier transform (FFT) is an algorithm that computes the Discrete Fourier Transform (DFT) of a sequence, or its inverse (IDFT). Fourier analysis converts a signal from its original domain (often time or space) to a representation in the frequency domain and vice versa. The DFT is obtained by decomposing a sequence of values into components of different frequencies. This operation is useful in many fields, but computing it directly from the definition is often too slow to be practical.

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