ZH: add gaussian noise to traces when beaconing

Note that this is a single noise realisation that is added to the three traces.
It will be ~3 times stronger for E_AxB

simulations/airshower_beacon_simulation/aa_generate_beacon.py

@@ -82,6 +82,8 @@ def Antenna_from_h5ant(h5ant, traces_key='traces', raise_exception=True, read_Ax
         ant.Ez = deepcopy(h5ant[traces_key][3])
         if len(h5ant[traces_key]) > 4:
             ant.beacon = deepcopy(h5ant[traces_key][4])
+        if len(h5ant[traces_key]) > 5:
+            ant.noise = deepcopy(h5ant[traces_key][5])
 
     # E_AxB
     if read_AxB and 'E_AxB' in h5ant:
@@ -240,6 +242,8 @@ def write_baseline_time_diffs_hdf5(fname, baselines, true_phase_diffs, k_periods
 if __name__ == "__main__":
     from os import path
 
+    rng = np.random.default_rng()
+
     fname = "ZH_airshower/mysim.sry"
 
     # Transmitter
@@ -276,6 +280,9 @@ if __name__ == "__main__":
 
         beacon_amplitudes *= ampl
 
+    # Noise properties
+    noise_sigma = 1e-4 # set to None to ignore
+
     # Disable block_filter
     if False:
         block_filter = lambda x, dt, low, high: x
@@ -294,6 +301,7 @@ if __name__ == "__main__":
 
     print("Beacon amplitude at tx [muV/m]:", beacon_amplitudes)
     print("Tx location:", [tx.x, tx.y, tx.z])
+    print("Noise sigma:", noise_sigma)
 
     # read in antennas
     ev = REvent(fname)
@@ -328,13 +336,20 @@ if __name__ == "__main__":
                 print(f"Modified trace lengths by {pre_N},{after_N-N_samples}")
 
         beacon = lib.beacon_from(tx, antenna, f_beacon, antenna.t, c_light=c_light, radiate_rsq=beacon_radiate_rsq)
-        traces = np.array([antenna.Ex, antenna.Ey, antenna.Ez, beacon])
+
+        # noise realisation
+        noise_realisation = 0
+        if noise_sigma is not None:
+            noise_realisation = rng.normal(0, noise_sigma, size=len(beacon))
+
+        # Collect all data to be saved (with the first 3 values the E fields)
+        traces = np.array([antenna.Ex, antenna.Ey, antenna.Ez, beacon, noise_realisation])
 
         # add to relevant polarisation
         # and apply block filter
         dt = antenna.t[1] - antenna.t[0]
         for j, amp in enumerate(beacon_amplitudes):
-            traces[j] = block_filter(traces[j] + amp*beacon, dt, low_bp, high_bp)
+            traces[j] = block_filter(traces[j] + amp*beacon + noise_realisation, dt, low_bp, high_bp)
 
         append_antenna_hdf5( antennas_fname, antenna, traces, name='traces', prepend_time=True)