Fix cn0 estimate

JuliaGNSS · Jan 24, 2020 · fefe6fc · fefe6fc · zsoerenm · Jan 24, 2020
1 parent b43066f
commit fefe6fc
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Showing 3 changed files with 5 additions and 3 deletions.
diff --git a/Project.toml b/Project.toml
@@ -1,7 +1,7 @@
 name = "Tracking"
 uuid = "10b2438b-ffd4-5096-aa58-44041d5c8f3b"
 authors = ["Soeren Zorn <soeren.zorn@nav.rwth-aachen.de>"]
-version = "0.11.0"
+version = "0.11.1"
 
 [deps]
 DocStringExtensions = "ffbed154-4ef7-542d-bbb7-c09d3a79fcae"

diff --git a/README.md b/README.md
@@ -29,7 +29,7 @@ using Tracking
 using Tracking: Hz, GPSL1
 carrier_doppler = 1000Hz
 code_phase = 50
-sample_frequency = 2.5MHz
+sample_frequency = 2.5e6Hz
 prn = 1
 state = TrackingState(GPSL1, carrier_doppler, code_phase)
 results = track(signal, state, prn, sample_frequency)

diff --git a/src/cn0_estimation.jl b/src/cn0_estimation.jl
@@ -42,6 +42,8 @@ function estimate_cn0(cn0_estimator::MomentsCN0Estimator, integration_time)
     M₂ = 1 / length(cn0_estimator) * sum(abs2_prompt_buffer)
     M₄ = 1 / length(cn0_estimator) * sum(abs2_prompt_buffer .^ 2)
     Pd = sqrt(abs(2 * M₂^2 - M₄))
-    SNR = Pd / (M₂ - Pd)
+    noise_power = (M₂ - Pd)
+    noise_power_non_neg = noise_power - 2 * (noise_power < 0) * noise_power
+    SNR = Pd / noise_power_non_neg
     dBHz(SNR / integration_time)
 end