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How did they get 10000 in working below? Why is the lobe at -10dB?

How did they get 10000 in working below? Why is the lobe at -10dB?

Introductory Circuit Analysis (13th Edition)
Introductory Circuit Analysis (13th Edition)
13th Edition
ISBN:9780133923605
Author:Robert L. Boylestad
Publisher:Robert L. Boylestad
Chapter1: Introduction
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Problem 1P: Visit your local library (at school or home) and describe the extent to which it provides literature...
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How did they get 10000 in working below? Why is the lobe at -10dB?
A 6 GHz common-carrier microwave communications link uses a tower-mounted antenna with a gain of 40 dB, and a transmitter power of 5 W. To evaluate the radiation hazard of this system, calculate the power density at a distance of 20 m from the antenna. Do this for a position in the main beam of the antenna, and for a position in the side lobe region of the antenna. Assume a worst-case side lobe level of -10 dB. Note: The recommended safe power density is as low as 0.2 mW/cm² at the lower RF range of around 100 MHz because the fields penetrate the body more deeply at lower frequencies. Above 15 GHz the power density limit rises to 10 mW/cm². At 6 GHz the safe limit is 1.2 mW/cm².
Transcribed Image Text:A 6 GHz common-carrier microwave communications link uses a tower-mounted antenna with a gain of 40 dB, and a transmitter power of 5 W. To evaluate the radiation hazard of this system, calculate the power density at a distance of 20 m from the antenna. Do this for a position in the main beam of the antenna, and for a position in the side lobe region of the antenna. Assume a worst-case side lobe level of -10 dB. Note: The recommended safe power density is as low as 0.2 mW/cm² at the lower RF range of around 100 MHz because the fields penetrate the body more deeply at lower frequencies. Above 15 GHz the power density limit rises to 10 mW/cm². At 6 GHz the safe limit is 1.2 mW/cm².
A Tower mounted antenna 20m S = Gt Pt 47 R² Lobe at -10 dB = f = 6GHZ G=40dB P₁ = 5W R= 20m 10 000 x5 47 (201² S: 0.1m w/cm² = 9.947 w/m² 9.947x0³ 104 ≈ /mw/cm² = mW/cm²
Transcribed Image Text:A Tower mounted antenna 20m S = Gt Pt 47 R² Lobe at -10 dB = f = 6GHZ G=40dB P₁ = 5W R= 20m 10 000 x5 47 (201² S: 0.1m w/cm² = 9.947 w/m² 9.947x0³ 104 ≈ /mw/cm² = mW/cm²
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