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Excel sheet to estimate range for Indoor and Outdoor
Tool/software: WEBENCH® Design Tools
Dear Support Team,
I am facing a few problems with the excel RF_Range_Estimator tool. Following Problems I would appreciate you would help me with:
- Plot Step: Is there any reason why it´s changing each time I choose No or with Antenna Diversity? What Connection does it have with the rest of the calculations in the calc Sheet?
- Direct Wave & Reflected Wave: In the PDF Document swra479a on the page 21, there are all Formulas, or let me say almost all, where you choose an "unknown" distance for me... Could u please explain that?
- Total Energy Friis: What difference does this value have in comparison with the Vertical/Horizontal? In my calculations, the last both mentioned will vary if the polarization is horizontal or vertical. Friis Formula is basically the same, because it considers the Reflected Energy depending on the polarization. My question is: what is the difference?
Thank You in Advance,
Wishing you a nice weekend
1) The calculator considers the link budget which accounts for the attenuation and other sources of losses of a propagating signal. This attenuation/loss can be taken into account by adding margin. This margin can be reduced by using mitigating techniques such as antenna diversity.
2) See Figure 1 in swra479. H1 and H2 are the antenna's elevation above ground. The distance between the two antennas is represented as d. The direct wave and reflect wave's distance traveled, which can be calculated using H1/H2, d, and the formulas on pg21, are represented by the red lines.
3) A horizontally polarized electromagnetic wave's electric field propagates parallel to the ground, which makes it more lossy. This is why the majority of cellular systems use vertical polarization.
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In reply to Seong Kim:
Dear Mr. Seong,
thank you very much for your answer but it´s unfortunately still not clear one question.
In the "Calc" Excel Sheet there is "Total Energy [dBm]" of Friis, Direct + Reflected (Vertical, Horizontal). My question is, what formula or combination of the earlier obtained results are you using? It is clear that the Vertical and the Horizontal Values are obtained from the "Energy" which depends on the Reflection Coefficient calculated before. But Friis? Is it just the sum up of the Vertical and Horizontal values?
In reply to Cotovici Elena:
The "Achieving Optimum Radio Range" Appnote explains that the Friis Equation determines the range for radio systems in open and free space environments. See section 2.4.
The 2-Ray Ground Reflection Model (Friss Equation w/ Ground Reflection) considers the influence of polarization and ground in open field measurements. See section 2.5.
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