7 ms·

Yeah, but it does take a lot more power as you point out. Just like you can use the phased array to form a beam toward a particular location of a particular siz

Yeah, but it does take a lot more power as you point out. Just like you can use the phased array to form a beam toward a particular location of a particular size, you can also do the opposite and create deliberately low gain toward the jammer. So then you need enough jammer power to overwhelm the LNAs on the individual elements, each of which have relatively low gain.

sidewndr46 2y ago
no, it doesn't work that way at all. The receive side of a communication satellite would be multiple antennas each connected to its own receivers. The receiver all use a common clock source to perform demodulation (which is a bunch of steps usually, but whatever). The result of each receiver is summed, the result signal is transmitted by another transmitter connected to a different antenna on a different frequency. Phase difference between the receivers is used to steer the array. How the phase difference is created varies. But if you overwhelm just one receiver it basically just injects noise into the entire process. So you wind up summing noise with all the other signals, which destroys the signal to noise ratio of the transmitted signal now if the control station can switch one receiver off to a dummy load, instead of to an antenna that might be useful. Whether or not military comm satellites can do that is most definitely classified.
- gruez 2y ago
  >now if the control station can switch one receiver off to a dummy load, instead of to an antenna that might be useful. That wouldn't do anything, would it? A phased array antenna is relatively small enough that a jamming signal from the ground would jam all antennas, not just one or a few.
  - sidewndr46 2y ago
    depends on the arrangement of the antennas. When it comes to phased arrays you can basically use any arrangement you want within reason
- MegaDeKay 2y ago
  I was assuming the receive antenna is also a phased array and the first thing after each element has to be a passband filter and an LNA for reasons of G/T. That happens before all the demodulation per element. You said the approach was to "overwhelm the receiver to the point it becomes a non-linear device", and pushing that LNA past P1dB will start to do just that. If the LNA remains linear, a countermeasure to the process you're talking about would be for its user to lower the symbol rate and number of carriers per channel to increase the C/N of the desired signal in an effort to punch through the jamming, albeit with less capacity. Having said all that, not sure which of the two effects is at play here.

sidewndr46 2y ago

no, it doesn't work that way at all. The receive side of a communication satellite would be multiple antennas each connected to its own receivers. The receiver all use a common clock source to perform demodulation (which is a bunch of steps usually, but whatever). The result of each receiver is summed, the result signal is transmitted by another transmitter connected to a different antenna on a different frequency. Phase difference between the receivers is used to steer the array. How the phase difference is created varies. But if you overwhelm just one receiver it basically just injects noise into the entire process. So you wind up summing noise with all the other signals, which destroys the signal to noise ratio of the transmitted signal now if the control station can switch one receiver off to a dummy load, instead of to an antenna that might be useful. Whether or not military comm satellites can do that is most definitely classified.

gruez 2y ago
>now if the control station can switch one receiver off to a dummy load, instead of to an antenna that might be useful. That wouldn't do anything, would it? A phased array antenna is relatively small enough that a jamming signal from the ground would jam all antennas, not just one or a few.
- sidewndr46 2y ago
  depends on the arrangement of the antennas. When it comes to phased arrays you can basically use any arrangement you want within reason
MegaDeKay 2y ago
I was assuming the receive antenna is also a phased array and the first thing after each element has to be a passband filter and an LNA for reasons of G/T. That happens before all the demodulation per element. You said the approach was to "overwhelm the receiver to the point it becomes a non-linear device", and pushing that LNA past P1dB will start to do just that. If the LNA remains linear, a countermeasure to the process you're talking about would be for its user to lower the symbol rate and number of carriers per channel to increase the C/N of the desired signal in an effort to punch through the jamming, albeit with less capacity. Having said all that, not sure which of the two effects is at play here.