The bias is dependent upon the signal to interference mean power ratio. Therefore it is – dependent upon both interference level and the number of in the estimate “hits” periodogram. Maximum interference level for reflectivity is defined by the reflectivity bias. – A reflectivity bias (Rb) of 1 dB yields a power ratio of 1.2589. – Power Ratio = 10(Rb/10) = 10(0.1) = 1.2589 Subtracting the unbiased power ratio from the power ratio at which a 1 dB bias occurs yields an interference to signal ratio of 0.2589. = [10(Rb/10) 10(Rb/10)] = [1.2589 1] = 0.2589 I/S – – The interference power level can be computed from the following formula: This value translates to a 6.17 dB signal. (dB) = 10 log (4.14) = 6.17 dB IL For a signal-to-noise-ratio of 3 dB, can be computed as follows: I/N = 6.17 dB + 3 dB = 9.17 dB I/N Combining these factors into a function that describes in relationship to and results in I/N Ns, I/N Rb an equation that yields the maximum required for a single I/N “hit”: where: number of samples in the estimate; Ns: signal mean power; Smp: receiver ratio; S/N: interference-to-signal ratio, I/S: and is expressed as: I/S where: reflectivity bias; Rb: normalized noise floor level. Nnf: Combining the equations yields: An example calculation that is based upon the previous assumptions follows. 8.4.2.2.2 Example calculation Assumptions: = 16; Ns = 3 dB; S/N = 1 dB; Rb = 0 dB; Nnf
– The bias is dependent upon the signal to interference mean power ratio. Therefore it is dependent upon both interference level and the number of “hits” in the estimate periodogram. – Maximum interference level for reflectivity is defined by the reflectivity bias. – A reflectivity bias (Rb) of 1 dB yields a power ratio of 1.2589. Power Ratio = 10(Rb/10) = 10(0.1) = 1.2589 Subtracting the unbiased power ratio from the power ratio at which a 1 dB bias occurs yields an interference to signal ratio of 0.2589. I/S = [10(Rb/10) – 10(Rb/10)] = [1.2589 – 1] = 0.2589 The interference power level can be computed from the following formula: This value translates to a 6.17 dB signal. IL (dB) = 10 log (4.14) = 6.17 dB For a signal-to-noise-ratio of 3 dB, I/N can be computed as follows: I/N = 6.17 dB + 3 dB = 9.17 dB Combining these factors into a function that describes I/N in relationship to Ns, I/N and Rb results in an equation that yields the maximum required I/N for a single “hit”: where: Ns: number of samples in the estimate; Smp: signal mean power; S/N: receiver ratio; I/S: interference-to-signal ratio, and I/S is expressed as: where: Rb: reflectivity bias; Nnf: normalized noise floor level. Combining the equations yields: An example calculation that is based upon the previous assumptions follows. 8.4.2.2.2 Example calculation Assumptions: Ns = 16; S/N = 3 dB; Rb = 1 dB; Nnf = 0 dB;
USWP5B20-17%20M1849_finalDraftR2.docx