Excellent work there garrya!

Glad that we can help you here Spurts!

I think you should go through this document about jamming LPI radars.

All modern military radars have a lot of LPI features and many can be classified as LPI radars. Those equations in garrya's Excel document are simplified (because they would get very complex quickly) and don't separately take into account things like radar and jammer instantaneous and total bandwidth or number of frequencies used for frequency hopping or modulation or pulse compression. Those things give the radar massive processing gain and that could simply be taken into account by increasing the required J/S in the equations. For example modern LPI radar could have something like additional 20-50 dB gain from those. So insted of requiring 10 dB J/S the required J/S could be 40 dB (or even more). Or if you wish, you could take that into account in the radar antenna gain by increasing it by tht amount. The end result would be the same.

In other words, the radar knows the frequencies it uses and how the radar signals are coded. The jammer does not and has to spread the energy over far wider bandwidth. For example this quote from the document here:

I think the equations there are exactly what you need to use but you just have to find correct figures to use. I think it's easiest to just assume pretty high required J/S against modern radar.

Glad that we can help you here Spurts!

I think you should go through this document about jamming LPI radars.

- LPI_Jamming_a456960.pdf
- (1.88 MiB) Downloaded 81 times

All modern military radars have a lot of LPI features and many can be classified as LPI radars. Those equations in garrya's Excel document are simplified (because they would get very complex quickly) and don't separately take into account things like radar and jammer instantaneous and total bandwidth or number of frequencies used for frequency hopping or modulation or pulse compression. Those things give the radar massive processing gain and that could simply be taken into account by increasing the required J/S in the equations. For example modern LPI radar could have something like additional 20-50 dB gain from those. So insted of requiring 10 dB J/S the required J/S could be 40 dB (or even more). Or if you wish, you could take that into account in the radar antenna gain by increasing it by tht amount. The end result would be the same.

In other words, the radar knows the frequencies it uses and how the radar signals are coded. The jammer does not and has to spread the energy over far wider bandwidth. For example this quote from the document here:

FSK radars are said to have an anti-jam advantage as seen in Figure 62. This advantage is based on the assumption that the jammer knows only the full hopping range and must spread its jamming power over that full frequency range. Assume an FSK radar that has a 2000 frequency hopping sequence which is random or unknown to the ES receiver. The FSK radar can be said to have a jamming advantage of 2000, which converts to 33dB. This means that it takes 33dB more jammer power to achieve a given JSR against this frequency hopper than would be required if it were a fixed-frequency conventional radar.

I think the equations there are exactly what you need to use but you just have to find correct figures to use. I think it's easiest to just assume pretty high required J/S against modern radar.