Question

Design a satellite communication link operating in the Ku band to meet C/N and link margin specifications. UPLINK: Design a transmitting earth station (transmitted antenna gain in dB and earth station transmitted power in W) to provide (C/N)up of 35 dB in a Ku-band transponder. Use an uplink antenna with a diameter of 3m and an aperture efficiency of 65%. The uplink station is located at -2 dB contour of the satellite footprint. Allow 1.5 dB for clear air atmospheric attenuation and other losses. Path length to satellite is 38 500 km. Assume standard frequency allocation of 14GHz for the uplink in Ku-band.

Satellite parameters are: Antenna gain 25 dB; Receive system noise temperature 500 K; Transponder saturated output power in Ku band 40 W; Transponder bandwidth 36 MHz; Signals: FM-TV analog signal. Earth station receiver IF noise bandwidth is 27MHz. Minimum C/N overall = 12 dB. Perform your calculations using decibels. (Boltzmann’s constant in decibels is k=-228.6 dBW/K/Hz)

Answer 1

To design a satellite communication link operating in the Ku band, the transmitting earth station needs an antenna gain of 38.25 dB and transmit power of 207.77 W, based on the given C/N and link margin specifications. The required values can be calculated using formulas for antenna gain, transmitted power, and path loss.

Step-by-step explanation:

To design a satellite communication link operating in the Ku band to meet C/N and link margin specifications, we need to calculate the values for the transmitting earth station. The transmitted antenna gain in dB is calculated using the formula:

Antenna Gain (dB) = 10 * log10(pi * (D/λ)^2 * η)

Where D is the diameter of the antenna, λ is the wavelength, and η is the aperture efficiency. Plugging in the values given, we have:

Antenna Gain (dB) = 10 * log10(pi * (3/0.021)^2 * 0.65) = 38.25 dB

The earth station transmitted power in W can be calculated using the formula:

Transmitted Power (W) = (C/N)up - Antenna Gain (dB) + Satellite EIRP (dB) + Path Loss (dB)

Where (C/N)up is the desired carrier-to-noise ratio, and Satellite EIRP (dB) is the effective isotropic radiated power of the satellite. With the given value of (C/N)up = 35 dB and Satellite EIRP = 40 dBW, we have:

Transmitted Power (W) = (35 - 38.25 + 40 + Path Loss (dB))

To find the Path Loss (dB), we can use the formula:

Path Loss (dB) = 20 * log10(4 * pi * distance * f / c)

Where distance is the path length to the satellite, f is the frequency (14 GHz), and c is the speed of light. Plugging in the values, we have:

Path Loss (dB) = 20 * log10(4 * pi * 38500 * 14 * 10^9 / 3 * 10^8) = 171.02 dB

Substituting this value into the previous equation, we get:

Transmitted Power (W) = (35 - 38.25 + 40 + 171.02) = 207.77 W

Therefore, to meet the C/N and link margin specifications, the transmitting earth station should have an antenna gain of 38.25 dB and transmit power of 207.77 W.