How many carriers for phased array?

[sophiecentaur]

as far as the angular range to operate is concerned, the desirable limit would be 5 degrees,

What do you mean by this statement? How does this relate to the situation?

 

[Esquilo]

What do you mean by this statement? How does this relate to the situation?

I mean it would be desirable to have a very collimated and directional beam with the same directionality as a laser, but with that wavelength it would be difficult, that was just my guess

 

[Esquilo]

@sophiecentaur So, what antenna size is best for my purpose? I'm just missing this information, but I can't seem to find the right path. I believe the half-wave antenna will provide more stability, but I'm looking for your opinion, which is much more valuable.

 

[sophiecentaur]

@sophiecentaur So, what antenna size is best for my purpose? I'm just missing this information, but I can't seem to find the right path. I believe the half-wave antenna will provide more stability, but I'm looking for your opinion, which is much more valuable.

You haven't stated your "purpose" so there is no answer. Are you aware of the theory that applies to multiple element antennae?

I mean it would be desirable to have a very collimated and directional beam with the same directionality as a laser,

This is nonsense in the context of a small array and the RF frequency you propose. Are you aware of the formula for the limiting width of a beam, given the wavelength and aperture of the array? I think some homework is called for. There's no point in my telling you about this; you have to do some searching about multi-element arrays. Google is full of that information and you need to have an idea about it if you plan to have a working system.
I suspect you may be in the world of simulation and not the practical world

 

[Esquilo]

@sophiecentaur yes yes I already knew that the focal point of the array depends on the aperture of the array itself and on the wavelength, and I did the calculations for near field focusing and the Frasnel distance is around 50 and 70 cm away, but I don't understand what this has to do with the choice of the size of the antenna, whether half wave or quarter wave, yes I am a beginner and I study every topic that I don't know, but since I am a beginner I am here asking questions, if I knew everything I wouldn't be here.

 

[renormalize]

but I don't understand what this has to do with the choice of the size of the antenna, whether half wave or quarter wave, yes I am a beginner and I study every topic that I don't know, but since I am a beginner I am here asking questions, if I knew everything I wouldn't be here.

Perhaps you can gain intuition regarding the kind of beams that can be formed from a phased array of antennas by playing with on-line calculators. For example, here's one that allows you to adjust the number of antenna elements, their spacing and relative phase shifts:
https://www.desmos.com/calculator/ ahcf6sjs7z

Here's another that lets you choose the specific type of the individual antennas:
https://antennaarraycalculator.blogspot.com/p/calculator.html

But do bear in mind that these calculators model a linear (1D) $n$-element array of antennas. If you desire a beam that is narrow in both transverse directions, you require a 2D rectangular array of $n^2$ elements. That amounts to 100 antennas for the second case above and a whopping 324 in the first!

 

[Esquilo]

@renormalize yes, to have 5 degrees like lasers, I would need arrays with sides of many meters and therefore with many antennas also considering the frequency, but no, as already said, I will operate in the non-radiative near field (Fresnel) and therefore with the waves not yet propagating, therefore in near field focusing, as already said the distance is about 50 or even less, however, the fact of using a rectangular array rather than a square one I did not know, I will have to find out more, the spacing between the antennas will still be half a wavelength, but returning to my original question and that is what size to choose for the antennas, I believe that the half-wavelength solution is the most suitable choice because having ground planes with quarter-wavelengths distorts the lines, do you agree too??

 

[sophiecentaur]

I will operate in the non-radiative near field

When you say "operate", are you trying to do Direction Finding or position finding? I have asked several times about the actual application because this could be very relevant. There is a long history of working navigation system designs - so called Hyperbolic systems which use phase / timing difference between the reception of two transmissions from different directions to produce a locus of possible positions (on a hyperbola). Adding a third transmitter source will locate position at the intersection of two hyperbola. If you haven't considered this and if the dimensions of your system are suitable (actual distances and available aperture) then it could be worth while researching the basics of the Decca Navigator system.

All this is far more relevant than the choice of radiating elements so it needs to be decided upon and stated first. Look carefully in the above post from @renormalize. The overall pattern that's quoted is for omnidrectional elements; the direction and width of the 'main beam' is largely independent of the element pattern. Have you taken that on board?

 

[Esquilo]

@sophiecentaur No, my goal isn't that complex. I need it to create beats in a water tank and calculate how rainwater behaves as the beat's envelope frequency varies. That's all, so no navigator. As for directionality, patch antennas are best suited for arrays (which are already directional as a whole). So, yes, cavity patches aren't directional individually, but they become so with the array.

 

[sophiecentaur]

@sophiecentaur No, my goal isn't that complex. I need it to create beats in a water tank and calculate how rainwater behaves as the beat's envelope frequency varies. That's all, so no navigator. As for directionality, patch antennas are best suited for arrays (which are already directional as a whole). So, yes, cavity patches aren't directional individually, but they become so with the array.

OMG you have totally confused me now. Are you looking at water surface waves or RF EM waves.
I assume you will have looked at the radiation patterns of patch antennae. In general, they fire ' forward with a reduced field to the side. But, like I already commented, it would be the array pattern which would dominate.

I still don't know why you are not up front about the actual project. How do you intend to "create beats" on a water surface by firing RF at it? Please do not invest any money in this project until it makes engineering sense. Patterns of numbers from a simulation may not represent reality.

 

[Esquilo]

OMG you have totally confused me now. Are you looking at water surface waves or RF EM waves.
I assume you will have looked at the radiation patterns of patch antennae. In general, they fire ' forward with a reduced field to the side. But, like I already commented, it would be the array pattern which would dominate.

I still don't know why you are not up front about the actual project. How do you intend to "create beats" on a water surface by firing RF at it? Please do not invest any money in this project until it makes engineering sense. Patterns of numbers from a simulation may not represent reality.

Yes, my goal is to examine the behavior of rainwater at different types of beat frequencies, and based on the presence of dissolved salts or metals, knowing how rainwater behaves—that is, if I transmit an electromagnetic frequency, how do the different concentrations of metals in the water behave—will help me create a quick method for determining water pollution. Yes, I know the patches radiate forward, and in fact all the patch antennas will have to converge on a single point to create the beat, that's all. The fact that they don't radiate laterally is a good thing so there will be no coupling, so at this point and knowing my goal and project, what size antenna is best?

 

[sophiecentaur]

my goal is to examine the behavior of rainwater at different types of beat frequencies,

You seem to be suggesting that an RF signal would interact with the molecules on the surface of water. What sort of force would (could) be acting on the molecules of water due to the passage of an EM wave?

Before writing this post, I went to the top of this thread to check that the first post was not submitted on the First of April. This thread is more than 40 posts long which is a bit embarrassing because it hangs on a very dodgy premise. Where did you get the idea from?

I have asked, several times for you to give some background to all this but you have not responded until this last post. When you come up with a similar type of PF query, please start off with the basics and check that it involves real Science. It would save a lot of time

 

[Esquilo]

You seem to be suggesting that an RF signal would interact with the molecules on the surface of water. What sort of force would (could) be acting on the molecules of water due to the passage of an EM wave?

Before writing this post, I went to the top of this thread to check that the first post was not submitted on the First of April. This thread is more than 40 posts long which is a bit embarrassing because it hangs on a very dodgy premise. Where did you get the idea from?

I have asked, several times for you to give some background to all this but you have not responded until this last post. When you come up with a similar type of PF query, please start off with the basics and check that it involves real Science. It would save a lot of time

Mine is an innovative project. Furthermore, in the microwave range, water molecules interact with microwaves. Having the beats at visible frequencies (20 Hz or 10 Hz) would allow me to see the level of pollution. Anyway, if you don't want to answer my initial question, then no problem, I'll see what I can do.

 

[sophiecentaur]

Mine is an innovative project.

The term 'innovativer' implies it will work. Your idea is not founded on any real Science and will not work, for very good reasons. Microwaves increase the thermal energy of water. That doesn't involve the necessary forces to move the water.

Actually, what you are suggesting doesn't follow the basic rules of the Forum in that it proposes a personal theory that's not supported by accepted Physics.

 

[renormalize]

Mine is an innovative project. Furthermore, in the microwave range, water molecules interact with microwaves. Having the beats at visible frequencies (20 Hz or 10 Hz) would allow me to see the level of pollution. Anyway, if you don't want to answer my initial question, then no problem, I'll see what I can do.

But how much effort have you expended to understand and appreciate the already existing technology? For example, it took me less than a minute online to find this article from 2023:
Water quality analysis using mmWave radars
Abstract:
Water quality and drinkability assessment are of high importance for various applications from monitoring water utilities to emergency water source evaluation. Traditionally, water quality assessment is done in laboratories with spacious and expensive equipment. We propose a wearable, mm Wave Frequency-Modulated Continuous Wave (FMCW) radar based system to assess water quality. Given its small form-factor, low price, and its robustness to lighting and weather conditions, this family of radars can be integrated into wearable devices such as smart-watches, smart glasses, smart rings, etc. Equipped with mm Wave radar sensors, such wearables enable seamless monitoring of water quality in hands free settings. The proposed system is able to directly process the In-phase and Quadrature (IQ) data generated by the radar to detect varying levels of different contaminants in four different kinds of water. Specifically, it can identify different concentrations of salt with 100% accuracy, namely nitrate and chloride, as well as detecting different types of waters including Reverse Osmosis (RO), tap, river, and well water with 99.1 % accuracy.
The authors of this paper seem to be way ahead of you. So aren't you just trying to reinvent the wheel?

 

[berkeman]

And after that very helpful reply by @renormalize this thread is locked for Moderation.

UPDATE: Thread will remain closed. Thanks to all who tried to help the OP with their moving-target questions.