QAM/PSK Pulse shaping filter transition bandwidth corrected (#98)

* excess bandwidth is defined in porportion to signal bandwidth, not sampling rate, thus needs to be scaled by the samples per symbol

* filling in a comment to describe modification to code

torchsig/datasets/synthetic.py

@@ -366,8 +366,10 @@ def _generate_samples(self, item: Tuple) -> np.ndarray:
             (self.iq_samples_per_symbol * len(symbols),), dtype=np.complex64
         )
         zero_padded[:: self.iq_samples_per_symbol] = symbols
+        # excess bandwidth is defined in porportion to signal bandwidth, not sampling rate,
+        # thus needs to be scaled by the samples per symbol
         pulse_shape_filter_length = estimate_filter_length(
-            signal_description.excess_bandwidth
+            signal_description.excess_bandwidth/self.iq_samples_per_symbol
         )
         pulse_shape_filter_span = int(
             (pulse_shape_filter_length - 1) / 2