5. Communication Links : Page 2

a. Lunar observatory to the satellite link :
Table 5 : Summary of Uplink Information
Frequency (fc ) 37.750 GHz
Moon-based dish antenna diameter (D) 300 m
Aperture efficiency (ηa) 0.90
Satellite dish antenna diameter (d) 1.5 m
Aperture efficiency (ηa) 0.65
Receiver system noise temperature (TSYS ) 20 K
Required C/N in satellite transponder 7 dB
Bandwidth (BW) 3 GHz
RRC filter roll-off factor 0.55
Noise Bandwidth 2.22 Ghz
Distance between the observatory and satellite (Rmax) 64,595 km


Table 6 : Uplink Budget
Wavelength (λ) 0.0079 m
Satellite Antenna Gain (Gr) 56.0927 dB
Moon-based Antenna Gain (Gt) 101.0278 dB
Path Loss (PL) 220.1881 dB
Noise Power (PN) -106.8089 dB
Transmit Power (Pt) -36.7413 dB


b. Satellite to the Earth link :
Table 7 : Summary of Downlink Information
Frequency (fc ) 33.250 GHz
Earth Station dish antenna diameter (D) 34 m
Aperture efficiency (ηa) 0.94
Satellite dish antenna diameter (d) 1.5 m
Aperture efficiency (ηa) 0.65
Receiver system noise temperature (TSYS ) 270 K
Required C/N in earth station 7 dB
Bandwidth (BW) 3 GHz
RRC filter roll-off factor 0.55
Noise Bandwidth 2.22 Ghz
Distance between the earth station and satellite (Rmax) 471,510 km


Table 8 : Downlink Budget
Wavelength (λ) 0.0090 m
Satellite Antenna Gain (Gt) 54.9902 dB
Earth Station Antenna Gain (Gr) 81.2013 dB
Path Loss (PL) 236.3515 dB
Noise Power (PN) -109.4850 dB
Transmit Power (Pt) -2.3250 dB

c. Pulse Shaping : A raised cosine pulse is used for digital transmission. In order to satisfy the requirement to confine most of the radiated energy within the designated bandwidth, the design value of roll-off factor for the raised cosine filter is 0.55. By the chosen value it is achived that the power spectrum outside the specified bandwidth is 50 dB less than the peak value within the band.


Figure 10: Raised Cosine Pulse


Figure 11: Raised Cosine Pulse Spectrum

MATLAB CODES

link budget
pulse shaping

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