Signal to Noise Ratio Between Spacecraft Transmitter and Receiver Antenna

In summary, the SNR for the spacecraft using a transmitter power of 16 W at a frequency of 2.4 GHz, with transmitter and receiver antenna gains of 28 dBi and 60 dBi respectively, a distance from spacecraft to ground of 2 x 10^10 m, and an effective noise temperature of 14 degrees Kelvin, with a bit rate of 120 kbps and a bandwidth of 60 kHz, is 36.22 dB.
  • #1
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Homework Statement


Determine the SNR for the spacecraft that uses a transmitter power of
16 W at a frequency of 2.4 GHz. The transmitter and receiver antenna
gain are 28 dBi and 60 dBi, respectively. The distance from the space-
craft to ground is 2 ϫ 1010 m, the effective noise temperature of antenna
plus receiver is 14 degrees Kelvin, and a bit rate of 120 kbps. Assume
the bandwidth of the system to be half of the bit rate, 60 kHz.

Homework Equations


The equation below calculates received power in free space (no loss due to non free space).
Pr = Pt * (λ/(4πd))^2 * (Gt * Gr)

Pr is received power.
Pt is transmitted power.
λ is wavelength.
d is distance.
Gt is transmitter gain.
Gr is receiver gain.

Also, SNR = Pr/Pn [Pn = noise power]

The Attempt at a Solution


I calculated Pr plugging in the following...
Pt = 16 W
λ = 0.125 m
d = 2E10 m
Gt = 28 dBi = 630.96
Gr = 60 dBi = 1,000,000

giving me Pr = 2.497 * 10^(-15) W = -146.03 dBW

The main problem is I don't know how to calculate Pn, or how/why bandwidth, bit rate, and temp come into play here. Textbook not very helpful and struggled deciphering meaning on wikipedia.
 
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  • #2
I think I can use the equation Pn = kTBW to calculate noise power, where k is Boltzmann's constant, T is temp, and BW is bandwidth.k = 1.38 * 10^(-23) J/KT = 14 KBW = 60 kHzwhich gives me Pn = 1.232 * 10^(-13) W = -109.81 dBWSo SNR = -146.03 - (-109.81) = 36.22 dB
 

1. What is Signal to Noise Ratio (SNR)?

The Signal to Noise Ratio (SNR) is a measure of the strength of a signal compared to the background noise in a communication system. It is typically expressed as a ratio or in decibels (dB).

2. Why is SNR important in spacecraft communication?

In spacecraft communication, SNR is important because it determines the quality of the received signal. A higher SNR means a stronger signal and therefore a clearer and more reliable communication link between the transmitter and receiver.

3. How is SNR calculated?

SNR is calculated by taking the ratio of the signal power to the noise power. This can be expressed as SNR = Psignal/Pnoise or in decibels as SNR = 10log(Psignal/Pnoise).

4. What factors can affect SNR between spacecraft transmitter and receiver antenna?

There are several factors that can affect SNR in spacecraft communication, including distance between the spacecraft, atmospheric interference, antenna size and quality, and the power of the transmitter and receiver.

5. How can SNR be improved in spacecraft communication?

To improve SNR in spacecraft communication, the transmitter power can be increased, the receiver antenna can be made more sensitive, and the distance between spacecraft can be minimized. Additionally, advanced signal processing techniques can be used to filter out noise and improve the overall SNR.

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