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# Tag Info

## Hot answers tagged phased-array

9 votes
Accepted

### Phased array (rx only) with separate complete receivers

In short: yes, it's possible, but it's a bit harder than that. You want to drive all of the receivers from a shared clock, and sample them in phase with one another, to form a "coherent receiver&...
• 12.7k
5 votes
Accepted

### How do phased array antennas work when they produce spot beams?

I'm doing this from a transmit direction, first, I find that easier to explain. You know that antennas work in transmit as in receive, so what you'll (maybe?) learn will work for reception as well. ...
• 16.6k
4 votes

### Dual Rubber Ducky antennas

Theoretically yes, if you carefully control the lengths of the cables and the placement of the antennas. This is called a phased array. However, you would get a far better improvement in range by ...
4 votes

### Destructive interference between two close antennas

There is no single "destructive interference frequency". There is maybe a frequency where destructive interference occurs in a useful direction. It can be shown that for any array, at any ...
4 votes

### Phased array (rx only) with separate complete receivers

In Radio Astronomy, arrays are phased either by a distributed local oscillator, or by reconstructing the timebase (local atomic clocks synched to GPS) during analysis by also listening to known strong ...
• 543
4 votes

### What cause multiply has difference result between float and complex signal?

That's just the math behind it – everything is alright with these results! You need to write down the formula of the real-valued $\sin(t)$ in terms of $e^{j2\pi t}$ and $e^{-j2\pi t}$, and you'll see ...
• 16.6k
4 votes
Accepted

### What cause multiply has difference result between float and complex signal?

This is a consequence of what was discussed in your previous question, that any real-valued function like $\sin(\omega t)$ consists of both positive and negative frequencies. Multiplying by a complex ...
3 votes

### Why does beamforming bring more power to the received desired signal?

I don't understand the parameters of your equations. But ignoring the equations and answering the text of the question: beam forming depends on frequency and phase. If the phase of the output of two ...
• 13.5k
3 votes
Accepted

### Destructive interference between two close antennas

Look at the radiation patterns in all cases, and do that before you start plotting over frequency. What looks like "destructive interference" only happens in a certain direction, where the ...
• 11.5k
3 votes

### Variable polarization Yagi using two antennas on the same boom, joined together with variable feedpoint phase?

Yes, it is possible given two antennas at orthogonal angles to adjust the relative amplitude and phase between them and create vertical, horizontal, or anything between polarization. You can even ...
3 votes

### Phased Array Pattern

The hex grids can fit more transmitter/receivers into the same space, resulting in greater power output per square meter. But more importantly, the one you pictured also has independent ...
• 2,087
3 votes
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### Does antenna array structure effect overall radiation resistance?

Yes, element spacing and geometry most definitely has an effect on radiation resistance in the real world. Radiation resistance is essentially that part of the signal which is not lost in some other ...
• 1,844
3 votes

### Total cancellation in corporate feed network for patch antenna

I recommend eliminating the array altogether and instead put a single patch antenna inside the rocket body facing upward. The frequencies of GPS signals will freely penetrate a non-metalic body, ...
• 18.6k
3 votes

### Why is the total radiated power of array calculated by sum of square of excitation coefficients different from the result by integral of power pattern

It's all to do with mutuals, and you can't wish them away - even for 'ideal' antennas. Consider a simple case, two elements a reasonable distance apart. Give them excitation amplitudes +1 and -1. ...
• 181
2 votes

### Does antenna array structure effect overall radiation resistance?

An antenna is effectively a transformer between the impedance of free space (377Ω) and whatever the feedpoint impedance is. For any antenna which has only negligible losses, and no reactive impedance ...
2 votes
Accepted

### how does this collinear antenna work?

the lower coil seems to be an "ugly balun", a choke made out of coax, is this it? Sure looks like it. What is the 447mm "covered" section, though? Is it some sort of quarter-wave matching? should ...
• 12.7k
2 votes
Accepted

### How should I stack these folded dipoles?

The info is in the model number BM - Bluewave Marathon E - Exposed offset 139- Frequency F - Gain 5.5dBd N1 - Connector Type H - Horizontal Polarized More info can be found here - Please note ...
• 136
2 votes

### Effective Area of Dipole Array

For some context, the relevant part of the cited source: The average collecting area is defined by $$\langle A_e \rangle \equiv {\int_{4\pi} A_e d \over \int_{4\pi}d}.$$ The effective collecting ...
2 votes

### Variable polarization Yagi using two antennas on the same boom, joined together with variable feedpoint phase?

You should be able to use a traditional offset mount: The counterweight balances the weight and the wind-generated torque of the yagi. If you want to use a different offset for either side, use ...
• 7,888
2 votes

### Phasing harness for antenna array

The Christman feed system using 84 and 71 degree lines is an example in ON4UN's Low Band DXing book where 1/4 wave ground mounted verticals are used. The line lengths are calculated from feed line ...
• 31
2 votes

### Bow Tie antennas impedance

A single bowtie dipole does have an impedance of about 50 ohms. However, stacking multiple dipoles with a properly-designed phasing system can change that. Here's a TV antenna that I made and use, ...
• 8,081
2 votes
Accepted

### Vertically orienting beams with antenna arrays

A practical approach for steerable patterns at these frequecies is to use electronically steerable arrays. These can take on various forms but a simple example consists of 2 or 4 vertical elements ...
• 18.6k
2 votes
Accepted

### 440MHz collinear dipole array - suitable coax?

Good RG8 such as Belden 9913 has less loss than RG58 or LMR240, so as long as the thicker diameter doesn't cause you trouble, then it should work fine for your project.
• 9,262
2 votes

### Effective area of a phased array

The previous answers are correct only in the limit for a sparse array, where the elements are spaced at greater than a wavelength apart. N is the "array gain" (for an un-tapered array) ...
2 votes
Accepted

### Total radiation pattern in antenna arrays

The first is still correct, and can be evaluated at any position. The second is true only at broadside, when $\theta=0$. In your attempts, do you find that $\vec{E}_{total}$ is the same in all ...
• 11.5k
2 votes

### Why does beamforming bring more power to the received desired signal?

Since the originating signal is not a unidimensional, laser-like effect, but rather an inverse-square-law wave... an enormous percentage of the original signal is neglected by a single element antenna ...
• 4,423
2 votes
Accepted

### How to Feed 2 x Co-Phased 4 Element Yagi Antennas?

A gamma match on the yagi should give you 50 ohms unbalanced. If you do it both sides and have a balanced input, it's usually called a T-match. So the two Yagis each provide a roughly 50 ohm ...
• 11.5k
1 vote

### Excitation coefficient of a linear phased array

$I_n$ is the current on the element, the current which gives rise the to the fields. It has a magnitude and phase. From that you can derive the array patterns. This is a big simplification from a real-...
• 11.5k
1 vote
Accepted

### Phase shifts in antenna arrays

In your diagram, the + terminals would all be connected to the A arms. Assuming a half wave spacing of the dipole feedpoints, the EM fields can cancel parallel to the antenna elements, then add up to ...
• 13.5k
1 vote
Accepted

### Effective area of a phased array

In the textbook starting case of an antenna composed of N identical elements, with some spacing and individual pattern, all fed in phase with equal power, then the directivity, gain and effective ...
• 11.5k

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