Derive an expression of c/n ratio of satellite communication.
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A measure of the performance of a satellite link is the ratio of carrier power to noise power at the receiver input, and link-budget calculations are often concerned with determining this ratio.
Conventionally, the ratio is denoted by CNCN (or CNR), which is equivalent to PRPNPRPN . In terms of decibels,
CN=(PR)−(PN)(1)CN=(PR)−(PN)(1)
Evaluating the values for PRPNPRPN , we get
CN=(EIRP)+(GR)−(LOSSES)−(k)−(TS)−(BN)(2)CN=(EIRP)+(GR)−(LOSSES)−(k)−(TS)−(BN)(2)
The GTGT ratio is a key parameter in specifying the receiving system performance. The antenna gain GRGR and the system noise temperature TSTS can be combined in eq. (2) as
[GT]=[GR]−[TS]dBK−(3)[GT]=[GR]−[TS]dBK−(3)
Therefore, the link equation becomes
CN=(EIRP)+(GT)−(LOSSES)−(k)−(TS)−(BN)(4)CN=(EIRP)+(GT)−(LOSSES)−(k)−(TS)−(BN)(4)
The ratio of carrier power to noise power density PRN0PRN0may be the quantity actually required.
Since PN=kTNBN=N0BNPN=kTNBN=N0BN, then
[CN]=[CN0BN][CN]=[CN0BN]
=[CN0]−[BN]=[CN0]−[BN]
…and therefore,
[CN0]=[CN]+[BN](5)[CN0]=[CN]+[BN](5)
CNCN is a true power ratio in units of decibels, and BNBN is in decibels relative to 1 Hz, or dBHz. Thus, the units for [CN0][CN0] are dBHz. Substituting eq. (5) for [CN][CN] gives
CN0=(EIRP)+(GT)−(LOSSES)−(k)(6)
I Hope it will help!
^_^
A measure of the performance of a satellite link is the ratio of carrier power to noise power at the receiver input, and link-budget calculations are often concerned with determining this ratio.
Conventionally, the ratio is denoted by CNCN (or CNR), which is equivalent to PRPNPRPN . In terms of decibels,
CN=(PR)−(PN)(1)CN=(PR)−(PN)(1)
Evaluating the values for PRPNPRPN , we get
CN=(EIRP)+(GR)−(LOSSES)−(k)−(TS)−(BN)(2)CN=(EIRP)+(GR)−(LOSSES)−(k)−(TS)−(BN)(2)
The GTGT ratio is a key parameter in specifying the receiving system performance. The antenna gain GRGR and the system noise temperature TSTS can be combined in eq. (2) as
[GT]=[GR]−[TS]dBK−(3)[GT]=[GR]−[TS]dBK−(3)
Therefore, the link equation becomes
CN=(EIRP)+(GT)−(LOSSES)−(k)−(TS)−(BN)(4)CN=(EIRP)+(GT)−(LOSSES)−(k)−(TS)−(BN)(4)
The ratio of carrier power to noise power density PRN0PRN0may be the quantity actually required.
Since PN=kTNBN=N0BNPN=kTNBN=N0BN, then
[CN]=[CN0BN][CN]=[CN0BN]
=[CN0]−[BN]=[CN0]−[BN]
…and therefore,
[CN0]=[CN]+[BN](5)[CN0]=[CN]+[BN](5)
CNCN is a true power ratio in units of decibels, and BNBN is in decibels relative to 1 Hz, or dBHz. Thus, the units for [CN0][CN0] are dBHz. Substituting eq. (5) for [CN][CN] gives
CN0=(EIRP)+(GT)−(LOSSES)−(k)(6)
I Hope it will help!
^_^
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