BAE Systems Inches Out In Public On Electronic Warfare

Cockpit, radar, helmet-mounted display, and other avionics
  • Author
  • Message
Offline
User avatar

XanderCrews

Elite 5K

Elite 5K

  • Posts: 6071
  • Joined: 16 Oct 2012, 19:42

Unread post18 Oct 2016, 12:04

les_paul59 wrote:unfortunately we don't have all the specs on a system like the f-35's ew suite, but I think that the reason the U.S. is so confident in this jet is that the ew suite is a cut above everything else when combined with the vlo airframe and the radar.

The devil is always in the details




According to Marine general Amos a few years back F-35 is 85 percent as effective as an EA-6B...
Choose Crews
Offline

garrya

Forum Veteran

Forum Veteran

  • Posts: 837
  • Joined: 25 Dec 2015, 12:43

Unread post18 Oct 2016, 13:17

XanderCrews wrote:According to Marine general Amos a few years back F-35 is 85 percent as effective as an EA-6B...

In support jamming roles
in self protection jamming , f-35 will be much better.
Offline

hornetfinn

Elite 2K

Elite 2K

  • Posts: 2938
  • Joined: 13 Mar 2013, 08:31
  • Location: Finland

Unread post18 Oct 2016, 13:17

garrya wrote:hill , valley layout isnot needed for angular direction finding ,interferometry can be done with 2 antennas.
IMHO , the reason for the hill, valley layout is so that the jamming beam could be steered electronically.


That configuration could also be phased array antenna with receive only capability, with basically T/R modules without the "T". Phased array antenna would allow several high gain receive beams which would be limited with only number of receivers. Electronic steering works also in receive path. This means it'd be more sensitive than traditional antennas and could handle higher number of simultaneous signals. Restricting the system for receive only sounds a bit strange though as having full T/R modules would not be that much more complicated and would not lower the system performance as ESM system like it would've with other antenna systems. Maybe if there are space, heating or power restrictions that allows receive only system.
Offline

hornetfinn

Elite 2K

Elite 2K

  • Posts: 2938
  • Joined: 13 Mar 2013, 08:31
  • Location: Finland

Unread post18 Oct 2016, 13:33

garrya wrote:Because of eloisa question , i looked at some jamming vs radar problem , not sure if that just me or effect of jamming seem too good to be true ?
:shock:
weak jammer , high RCS and range burn through still extremely short ??????
Image


That's because the equation gives the maximum theoretical effectiveness for the jammer. The jammer is exactly at the same frequency as the radar and can concentrate the power directly against radar. Basically it's how the most basic radar systems would work against jammers. 100W of jamming power directly in band is actually a lot of jamming power. Real world radars have methods to give them much better chances against jamming like frequency hopping over wide bandwidth along with complex waveforms to increase required J/S ratio etc. Also radar antennas usually have higher gain than 30 dBi.
Offline

garrya

Forum Veteran

Forum Veteran

  • Posts: 837
  • Joined: 25 Dec 2015, 12:43

Unread post18 Oct 2016, 13:55

hornetfinn wrote:
That's because the equation gives the maximum theoretical effectiveness for the jammer. The jammer is exactly at the same frequency as the radar and can concentrate the power directly against radar. Basically it's how the most basic radar systems would work against jammers. 100W of jamming power directly in band is actually a lot of jamming power. Real world radars have methods to give them much better chances against jamming like frequency hopping over wide bandwidth along with complex waveforms to increase required J/S ratio etc. Also radar antennas usually have higher gain than 30 dBi.

That seem fair enough but aren't airborne radar limited in X band mostly (8-12 Ghz) the bandwidth is only 4 Ghz, i dont think spreading energy over a bandwidth of 4 Ghz would reduce jamming energy that much.
then there are many jammers with power > 100W too
Offline

wrightwing

Elite 3K

Elite 3K

  • Posts: 3385
  • Joined: 23 Oct 2008, 15:22

Unread post18 Oct 2016, 22:07

SpudmanWP wrote:There is plenty of documentation talking about the interaction of the APG-81 and the ASQ-239 in the active jamming role.

I realize that, but this article is suggesting that the ASQ-239 has jamming capabilities too, which wasn't necessarily acknowledged before.
Offline

SpudmanWP

Elite 5K

Elite 5K

  • Posts: 8406
  • Joined: 12 Oct 2006, 19:18
  • Location: California

Unread post18 Oct 2016, 22:17

wrightwing wrote:
SpudmanWP wrote:There is plenty of documentation talking about the interaction of the APG-81 and the ASQ-239 in the active jamming role.

I realize that, but this article is suggesting that the ASQ-239 has jamming capabilities too, which wasn't necessarily acknowledged before.


Which could simply be the towed decoy too.

The only thing that is known is what is unknown.... :roll:
"The early bird gets the worm but the second mouse gets the cheese."
Offline

eloise

Elite 1K

Elite 1K

  • Posts: 1744
  • Joined: 27 Mar 2015, 16:05

Unread post19 Oct 2016, 05:51

SpudmanWP wrote:Which could simply be the towed decoy too.

but that wouldn't make lots of sense
towed decoy cant jam frontal aspects and APG-81 would be limited in frequency (X band), I think it totally makes sense for ASQ-239 to have jamming capability
Offline
User avatar

popcorn

Elite 5K

Elite 5K

  • Posts: 7715
  • Joined: 24 Sep 2008, 08:55

Unread post19 Oct 2016, 06:13

eloise wrote:
SpudmanWP wrote:Which could simply be the towed decoy too.

but that wouldn't make lots of sense
towed decoy cant jam frontal aspects and APG-81 would be limited in frequency (X band), I think it totally makes sense for ASQ-239 to have jamming capability

There's no silver bullet. Individual pieces of kit contribute to achieve the desired effect.
"When a fifth-generation fighter meets a fourth-generation fighter—the [latter] dies,”
CSAF Gen. Mark Welsh
Offline

wrightwing

Elite 3K

Elite 3K

  • Posts: 3385
  • Joined: 23 Oct 2008, 15:22

Unread post19 Oct 2016, 08:58

My takeaway is this- the title suggests that BAE is saying the ASQ-239 is more capable than previously admitted, and actually has broadband jamming capabilities, in addition to the X band jamming of the APG-81, and decoy functions.
Offline

eloise

Elite 1K

Elite 1K

  • Posts: 1744
  • Joined: 27 Mar 2015, 16:05

Unread post19 Oct 2016, 10:25

garrya wrote:That seem fair enough but aren't airborne radar limited in X band mostly (8-12 Ghz) the bandwidth is only 4 Ghz, i dont think spreading energy over a bandwidth of 4 Ghz would reduce jamming energy that much.
then there are many jammers with power > 100W too

Let say the transmitting power of jammer is 1kW , instantaneous bandwidth of radar pulse is 40 Hz ,radar only operate in X band so maximum bandwidth of radar is 4Ghz , the jammer has to spread its power over 4000/40= 100 times compared to radar, so when they are overlap in frequency , jamming power in band is 1kW/100 = 10W.
Secondly, because jammer doesn't know exactly when radar transmit , it will have bigger duty cycle which will reduce peak power more
Offline

eloise

Elite 1K

Elite 1K

  • Posts: 1744
  • Joined: 27 Mar 2015, 16:05

Unread post19 Oct 2016, 10:41

Many fighter radar can actually operate outside X-band
EX :Apg-66v1
Image

Btw why APG-66v2 has such a narrow bandwidth compared to v1 version?
Offline

hornetfinn

Elite 2K

Elite 2K

  • Posts: 2938
  • Joined: 13 Mar 2013, 08:31
  • Location: Finland

Unread post19 Oct 2016, 11:10

garrya wrote:
hornetfinn wrote:
That's because the equation gives the maximum theoretical effectiveness for the jammer. The jammer is exactly at the same frequency as the radar and can concentrate the power directly against radar. Basically it's how the most basic radar systems would work against jammers. 100W of jamming power directly in band is actually a lot of jamming power. Real world radars have methods to give them much better chances against jamming like frequency hopping over wide bandwidth along with complex waveforms to increase required J/S ratio etc. Also radar antennas usually have higher gain than 30 dBi.

That seem fair enough but aren't airborne radar limited in X band mostly (8-12 Ghz) the bandwidth is only 4 Ghz, i dont think spreading energy over a bandwidth of 4 Ghz would reduce jamming energy that much.
then there are many jammers with power > 100W too


4 GHz is actually a huge swath of bandwidth to jam. If we have 100 watts jammer, it would have only 0.025 Watts per MHz. That means the jammer ERP would actually be only 17 dBi instead of 53 dBi. That change would directly mean that burn through range would become about 16 km instead. Another thing is that required J/S is only 2 dB for jamming to be effective. With modern radars the processing gain of complex coded waveforms is much higher and can easily be 30-40 dB (or even higher). Since usually detection requires about 13 dB SNR, the required J/S would be 17 to 27 dB in this case. That would further increase the range to well over 100 km. 40 dB processing gain would bring this to 355 km or so. These calculations do not take into account many things like system losses in radar and jammer etc, but they give the general idea.

Sure there are higher powered self protection jammers, but not by that much. Usually we are talking about less than 1 kW of power. Radars also have higher antenna gain than 30 dBi. A typical fighter radar has antenna gain of 30-40 dBi and larger surveillance and ground based fire control radars can have even higher antenna gain.

The equation clearly shows the importance of low RCS and directional antennas for effective jamming against modern radars. No wonder VLO stealth along with GaN phased array antennas for both radars and jammers are sought after.
Offline

garrya

Forum Veteran

Forum Veteran

  • Posts: 837
  • Joined: 25 Dec 2015, 12:43

Unread post19 Oct 2016, 11:49

eloise wrote:Let say the transmitting power of jammer is 1kW , instantaneous bandwidth of radar pulse is 40 Hz ,radar only operate in X band so maximum bandwidth of radar is 4Ghz , the jammer has to spread its power over 4000/40= 100 times compared to radar, so when they are overlap in frequency , jamming power in band is 1kW/100 = 10W

Necessary jamming power reduce at the same rate as RCS , the target in earlier example has 10 sqm RCS , if we was to consider target with RCS = 1 sqm then suddenly 10W is more than enough.
Offline

garrya

Forum Veteran

Forum Veteran

  • Posts: 837
  • Joined: 25 Dec 2015, 12:43

Unread post19 Oct 2016, 12:05

hornetfinn wrote:4 GHz is actually a huge swath of bandwidth to jam. If we have 100 watts jammer, it would have only 0.025 Watts per MHz.

But frequency range ( bandwidth) of a complex pulse would be much wider than 1 MHz though , is it not ?

hornetfinn wrote: That means the jammer ERP would actually be only 17 dBi instead of 53 dBi. That change would directly mean that burn through range would become about 16 km instead.

TBH iam not so good with number so can you elaborate a bit more ?
anyway, 16 km burn through range still seem extremely short for target with RCS = 10 m2 , that is well within range of IR sensor
hornetfinn wrote:Another thing is that required J/S is only 2 dB for jamming to be effective. With modern radars the processing gain of complex coded waveforms is much higher and can easily be 30-40 dB (or even higher).

That a fair point but as far as i know , while angle jamming technique require very high J/S ratio to be effective , range jamming technique doesnt seem to need J/S ratio that high
Image

hornetfinn wrote:Since usually detection requires about 13 dB SNR, the required J/S would be 17 to 27 dB in this case. That would further increase the range to well over 100 km. 40 dB processing gain would bring this to 355 km or so.

I dont really get this part , can you elaborate ?


hornetfinn wrote: Radars also have higher antenna gain than 30 dBi. A typical fighter radar has antenna gain of 30-40 dBi and larger surveillance and ground based fire control radars can have even higher antenna gain.

I know that ground radar can have very high gain ( their size is practically unlimited after all ) , but i dont think average fighter radar ( aka APG-81 ) has higher gain than 30 dB given their size and operating frequency
PreviousNext

Return to F-35 Avionics

Who is online

Users browsing this forum: No registered users and 13 guests