Electronic Warfare

Sensor Jamming

Sensor jamming attempts to overwhelm an opponent's search sensors (such as radars) to prevent one's detection.

When a Sensor jammer hits a shipborne sensor, it creates a "jammed volume" on that sensor. Given the distance between the jammer and the sensor [math]\displaystyle{ D_{j} }[/math] and the effect area ratio of the jammer, [math]\displaystyle{ E_r }[/math]. The jammed volume is a rectangular box centered on the jammer, with a length [math]\displaystyle{ =2D_{j} }[/math], and a width/height equal to [math]\displaystyle{ =2D_{j}E_r }[/math], with the length pointed toward the spotter. e.g. a jammer that is 5km away from a spotter will give that spotter a jammed volume 10km long and 4km wide.

If the sensor tries to spot a track within the jammed volume, the sensor will have to overcome the jamming power inflicted on it by the jammer.

Given the jammer's radiated power, [math]\displaystyle{ P }[/math], and gain, [math]\displaystyle{ G }[/math], the jamming power on a target at distance [math]\displaystyle{ d }[/math] is given by

[math]\displaystyle{ j = \frac{PG}{4\pi d^2} }[/math]

The modifier per jammer

Jammer power	Jammer multiplier	Total
Strongest Jammer	1.000	1.000
2nd Strongest	0.876	1.876
3rd Strongest	0.589	2.465
4th	0.304	2.770
5th	0.121	2.890
6th	0.037	2.927
7th	0.009	2.935
8th	0.002	2.937
9th	0.000	2.937

If a track is within multiple jammed volumes due to multiple jammers, the sensor will have to overcome the combined power of the jammers. The combined power is not a simple total, each additional jammer after the strongest will only add a fraction of its power to the final combined power. The power multiplier for a given jammer is calculated by [math]\displaystyle{ {e^{-(n/2.75)^{2}}} }[/math], where [math]\displaystyle{ n }[/math] is the number of jammers imparting greater jamming power than this jammer. As a result, total jamming power will never exceed 2.938x of the strongest jammer.

Detection range vs jammers

The distance that the jammer can be spotted by the target is found with the following formulas.

For a target (search) radar with:

• radiated power, [math]\displaystyle{ P_\text{t} }[/math]
• gain, [math]\displaystyle{ G_t }[/math]
• aperture size, [math]\displaystyle{ A }[/math]
• sensitivity, [math]\displaystyle{ S }[/math]
• and noise filtering, [math]\displaystyle{ \nu }[/math]

and with the jammer's cross-section being [math]\displaystyle{ \sigma }[/math] (in-game value divided by 10); and with [math]\displaystyle{ K = PG }[/math] from the numerator in [math]\displaystyle{ j }[/math] above (or the sum of multiple jammers, applying the stacking penalty),

the maximum distance for spotting the jammer, [math]\displaystyle{ d_j }[/math], is

[math]\displaystyle{ \large{ \begin{aligned} d_S &= \left(\frac{P_t G_t^2 A \sigma}{16\pi^2 (0.001)(10^{S/10})}\right)^{1/4}\\ & \\ d_N &= \sqrt{\frac{G_t\left(\sqrt{K^2 + \frac{(4\times 10^{-7})P_t A \sigma}{10^{\nu/10}}}-K\right)}{8\pi(1\times 10^{-7})}}\\ & \\ d_j &= \text{min}(d_S,d_N) \end{aligned} } }[/math]