Phased array sources need to be, as their name implies, phase-locked to each other.
So, the transmitters would need to be, typically, interconnected by coax, fiber or laser link to maintain relative phase and thus pointing direction. Or they’d need to be both synchronized to an external source.
This typically takes a deliberate action - it doesn’t just happen by accident normally. And when it does, the sources will be beating with each other since their frequencies may be close but not the same.
But that all applies if the sources were transmitting CW or something like it with a lot of unmodulated carrier present.
Instead, the digital transmission systems of today transmit what amounts to bandwidth-limited noise. There will be almost no correlation between the signals from two sources even if they run from the same clock source. They’ll just be each transmitting their own data.
If they are properly designed, they won’t be transmitting at the same time. Or they’ll use orthogonal code modulation that lets the receiver hear each transmitter individually even though they transmit at the same time.
That’s how GPS works. All the GPS satellites overhead transmit at the same time and same frequency, more-or-less. The receiver has a set of correlators that each separate one data stream from one satellite. The number of correlators is often referred to as “number of channels” - those are code modulation channels, not frequency channels!
Another example: we have two smartphones, and we have fed all circuits inside of them from shared clock sources, so they are perfectly synchronous.
Those cellphones respect a protocol that assigns them time slots or frequency channels that are not overlapping. So they will not interfere with each other in spite of being two identical RF systems at a fixed distance from each other. The frequency channels can be baseband channels, subcarrier channels, or a combination of them.
Imagine two transmitters synchronized to the same frequency reference and transmitting each a different 100% AM-modulated pure tone. The receiver will “hear” the sum of the tones. Even if the carriers are perfectly in phase. For there to be dropouts due to destructive interference, both transmitters would need to transmit the same tone, synchronously - so the spectrum of both signals would need to overlap. It's easy enough to make sure it doesn't, and AM modulation is not used for digital transmission all that much anyway.
Your concern is valid. RF systems have their modulation scheme and protocol designed not to interfere in such scenarios, by ensuring each transmitter can be heard individually at the receiver and is not transmitting a phase-locked signal identical to its neighbor.
Suppose we have a phone trying to communicate with a receiving satellite which is approximately 0 degree to the antenna, now this broadcasting satellite should be omnidirectional pattern. But now if an identical phone with identical antenna comes into picture at a distance lambda/4 and causes an antenna array to be formed, suppose it has phase diff. B=90 deg, than because of the array factor there will now be a zero towards the direction of satellite and all the directivity is focused opposite to satellite, which is unfortunate. If this type of scenario is possible, How do engineers counter this type of error to be formed. Since we hardly have issues with multiple devices close together in labs etc. I would like to understand how to counter the negative effect of antenna array.
