# Array Antenna sizing by number of elements

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#### robb-flynn

##### Newbie
Hi,

I should answer the following question:

A square array at 10 GHz needs 40 dB gain out to ±60° in both planes. The internal loss is 3 dB and SWR limit 3:1. The beam broadening factor is 1.2. How many elements are needed?
The instantaneous bandwidth is 10%. What is the minimum number of time delay devices that the array needs to only suffer a 3 dB loss at band edges?
.

Can anyone help me? In the hypothesis of considering a square array with half-wavelength spacing, I used the empirical formula "D0=32400cos(theta0)/(theta_x * theta_y)" (used, in turn, in the gain expression), but the number of elements that came out is just 3 :-(, thus suggesting the array would be 3x3, which I think is too small for 40dB of gain.

Welcome robb-flynn,

I don't think you've provided enough information. What is the gain and 3dB beamwidth of each element? etc.

Hi,

I should answer the following question:

A square array at 10 GHz needs 40 dB gain out to ±60° in both planes. The internal loss is 3 dB and SWR limit 3:1. The beam broadening factor is 1.2. How many elements are needed?
The instantaneous bandwidth is 10%. What is the minimum number of time delay devices that the array needs to only suffer a 3 dB loss at band edges?
.

Can anyone help me? In the hypothesis of considering a square array with half-wavelength spacing, I used the empirical formula "D0=32400cos(theta0)/(theta_x * theta_y)" (used, in turn, in the gain expression), but the number of elements that came out is just 3 :-(, thus suggesting the array would be 3x3, which I think is too small for 40dB of gain.

Hint: Use the Directivity Aperture equation projected at 60degrees
[D=cos(60)×4ΠA/(λ²)] reduce by 3dB loss=1/2 and fill Aperture with elements spaced at halfwave intervals.

I think you are mixing formulas for beamwidth with formul for gain. what (but I have ti chekc) that seems impossible is the 40dB gain over so wide angular range (probalby unfeasible). Wdie beam implies samll array high gain big array..

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