Doubt in Antenna phased array

Hi all,

In the below image shows a phased antenna array act as receiver. The source 1 and source 2 transmitting simultaneously. Array pattern 1 generated by phase shifters. My doubt is there will be one potential generated by source 1 in all the antennas elements if we consider the generated potential is x1’. There will another potential y1’ generated by all the antennas due to source 2. Will that potentials adds together(x1’+y1’) and generate a junk data? . In actual case it’s not happening , Will somebody you explain the physics behind its ?

Akhil

In this case we must consider time varying signals, which have phase.
Signals from source 1 and 2 received on each patch with some phase shift. Here is simplified example:

Two patches example
Assume we have two patches, signal source 1 is to the left , and signal source 2 is on the right, placed symmetrically at the same angle.
Patch 1 receives signal 1 with phase shift 0 deg, signal 2 with phase shift 90 deg
Patch 2 receives signal 1 with phase shift 90 deg, signal 1 with phase shift 0 deg.

Configuring phase shifters:
Phase shifter 1: + 90deg
Phase shifter 2: + 0deg

After phase shifters:
signal 1 patch 1: 90deg
signal 1 patch 2: 90deg

signal 2 patch 1: 180 deg
signal 2 patch 2: 0 deg

after power combiner:
signal 1: summed in-phase 2x amplitude
signal 2: summed out-of-phase (0deg, 180deg) , results in zero amplitude

Phase is relative to global time.

Random example for eight patches:

1) patch 1, signal source 1 is received with phase shift of 10 deg, source 2 is received with phase shift of 60 deg
2) 13 deg / 57 deg
3) 16 deg / 54 deg
4) 19 deg / 51 deg
5) 22 deg / 48 deg
6) 25 deg / 45 deg
7) 28 deg / 42 deg
8) 31 deg / 39 deg

Phase shifters are configured to form beam in source 1 direction, so each patch provides copy of signal 1 with the same phase
For example, each phase shifter provides phase shift:
1) phase shifter 1 provides shift of -3 deg, source 1 signal phase after phase shifter: 10-3=7deg
2) phase shifter 2 provides shift of -6 deg, source 1 signal phase after phase shifter: 13-6=7deg
3) phase shifter 3 provides shift of -9 deg, source 1 signal phase after phase shifter: 16-9=7deg
4) ... -12 deg, source 1 signal phase after phase shifter: 19-12=7deg
5) ... -15 deg, source 1 signal phase after phase shifter: 22-15=7deg
6) ... -18 deg, source 1 signal phase after phase shifter: 25-18=7deg
7) ... -21 deg, source 1 signal phase after phase shifter: 28-21=7deg
8) ... -24 deg, source 1 signal phase after phase shifter: 31-24=7deg

After phase shifting there is power combiner, adding 8 copies of signal 1 in power combiner provides signal with 8x amplitude received by single patch, because
we have the same sinusoidal signal and relative phase shift is 0 deg (7deg - 7deg = 0 deg)

Signal from source 2 while beam is directed to source 1,
1) 60 deg - 3 deg = 57 deg
2) 57 deg - 6 = 51
3) 54 deg - 9 = 45
4) 51 deg - 12 = 39
5) 48 deg - 15 = 33
6) 45 deg - 18 = 27
7) 42 deg - 21 = 21
8) 39 deg - 24 = 15
Signals from source 2 after phase shifting are more out of phase after shifting.

To get best results of suppressing unwanted directions each patch also may be equipped with variable power attenuator.

akhilpaulv said:

The source 1 and source 2 transmitting simultaneously.

Click to expand...

Superposition principle applies, so you can calculate both paths independently and then calculate the sum signal at the output. Beam direction of this phased array is controlled by phase shifters, as Georgy.Moskin described. If beam direction is towards source 1, a signal from source 2 direction will be attenuated, and vice versa.

So your statement

akhilpaulv said:

Will that potentials adds together(x1’+y1’) and generate a junk data? . In actual case it’s not happening

Click to expand...

is wrong: the signals will add, in calculation and in reality. But you need to consider the effective antenna pattern of the phased array, so magnitude of each signal depends on phase shifter settings.

"Patch 1 receives signal 1 with phase shift 0 deg, signal 2 with phase shift 90 deg
Patch 2 receives signal 1 with phase shift 90 deg, signal 1 with phase shift 0 deg."

In patch 1 , will the signal 1 and signal 2 add and create a new wave with new phase? because they are in the same frequency ???

akhilpaulv said:

In patch 1 , will the signal 1 and signal 2 add and create a new wave with new phase? because they are in the same frequency ???

Click to expand...

Yes, of course.

Antenna directivity results after adding the signals of all patches.

I see what are you trying to understand.
Each individual patch outputs sum of two received signals. Frequency of signals may be the same, or may be different, it works in both cases.

Small 2-patch example:
Assume we sampling signal from antenna using ADC
Phase shifters are configured to form narrow beam in source 1 direction and make perfect null at source 2 direction.
Let source 1 signal be very weak, and maximum digitized sine amplitude from single patch is -10 to +10
Let unwanted source 2 signal be very strong, and maximum digitized signal amplitude from single patch is -10000 to +10000
So at some time T single sample from ADC from first patch may be something like (-10)+(+10000)=9990. At first it seems that weak signal is totally lost (what you called "interference").
Using phase shifter after second patch we will obtain signal (-10)+(-10000)=-10010. Again, it seems that unwanted signal 2 is totally "interfered" weak amplitude of "-10".
But see what will happen after power combining: 9990+(-10010)=-20
we recovered weak signal with 2x gain (-10 -10 = -20), and totally eliminated unwanted signal (+1000-1000=0).

So any individual patch may have huge amount of unwanted signals summed. By tuning phase shifters we achieve following:
1) combine signals from wanted direction in-phase, sum
2) combine signals from unwanted direction out-of-phase, subtract them

In reality unwanted signal may be not on perfect nulling direction, and wanted signal is not on perfect in-phase combining direction. But even if unwanted signal is attenuated by some -10dB, and wanted signal is gained additional +5dB, it already changes whole picture.

If you still have doubts, read about microphone array beamforming. It is very similar topic, but may be easier to understand, because most part is done using software, so you can think about actual numbers.

Georgy.Moshkin said:

If you still have doubts, read about microphone array beamforming. It is very similar topic, but may be easier to understand, because most part is done using software, so you can think about actual numbers.

Click to expand...

Hi Geory Moshkin ,

My doubt arise , How to generate simultaneously two interdependent beams in an array for 5G communication!!

_akhil

Do search on dual-beam and multi-beam in Google, add filetypeDF keyword to find more articles.

In practice designing a Phased Array Antenna using identical antenna elements is more complicated, because there are at least five types of controls that can be used to shape the overall pattern of the antenna system:

- The geometrical configuration of the overall Antenna Array (linear, circular, rectangular, spherical, etc.).
- The relative spacing between the antenna elements (in practice, the separation (mutual coupling) between antenna elements is a critical characteristic of Antenna Array).
- The excitation amplitude of the individual antenna elements.
- The excitation phase of the individual antenna elements.
- The relative pattern of the individual antenna elements.