Add WDF allpass generator

Closes #156 (closed)

b_asic/sfg_generator.py

@@ -3,11 +3,11 @@ B-ASIC signal flow graph generators.
 
 This module contains a number of functions generating SFGs for specific functions.
 """
-from typing import Dict, Optional, Union
+from typing import Dict, Optional, Sequence, Union
 
 import numpy as np
 
-from b_asic.core_operations import SymmetricTwoportAdaptor
+from b_asic.core_operations import Name, SymmetricTwoportAdaptor
 from b_asic.port import InputPort, OutputPort
 from b_asic.signal import Signal
 from b_asic.signal_flow_graph import SFG
@@ -15,14 +15,44 @@ from b_asic.special_operations import Delay, Input, Output
 
 
 def wdf_allpass(
-    coefficients: np.ndarray,
+    coefficients: Sequence[float],
     input_op: Optional[Union[Input, Signal, InputPort]] = None,
     output: Optional[Union[Output, Signal, OutputPort]] = None,
     name: Optional[str] = None,
     latency: Optional[int] = None,
     latency_offsets: Optional[Dict[str, int]] = None,
     execution_time: Optional[int] = None,
-):
+) -> SFG:
+    """
+    Generate a signal flow graph of a WDF allpass section based on symmetric two-port adaptors.
+
+    Parameters
+    ----------
+    coefficients : 1D-array
+        Coefficients to use for the allpass section
+
+    input_op : Input, optional
+        The Input to connect the SFG to. If not provided, one will be generated.
+
+    output : Output, optional
+        The Output to connect the SFG to. If not provided, one will be generated.
+
+    name : Name, optional
+        The name of the SFG. If None, "WDF allpass section".
+
+    latency : int, optional
+        Latency of the symmetric two-port adaptors.
+
+    latency_offsets : optional
+        Latency offsets of the symmetric two-port adaptors.
+
+    execution_time : int, optional
+        Execution time of the symmetric two-port adaptors.
+
+    Returns
+    -------
+        Signal flow graph
+    """
     np.asarray(coefficients)
     coefficients = np.squeeze(coefficients)
     if coefficients.ndim != 1:
@@ -33,24 +63,30 @@ def wdf_allpass(
         output = Output()
     if name is None:
         name = "WDF allpass section"
-    # First-order section
-    coeff = coefficients[0]
-    adaptor0 = SymmetricTwoportAdaptor(
-        coeff,
-        input_op,
-        latency=latency,
-        latency_offsets=latency_offsets,
-        execution_time=execution_time,
-    )
-    signal_out = Signal(adaptor0.output(0))
-    delay = Delay(adaptor0.output(1))
-    Signal(delay, adaptor0.input(1))
-    # prev_adaptor = adaptor0
+    order = len(coefficients)
+    odd_order = order % 2
+    if odd_order:
+        # First-order section
+        coeff = coefficients[0]
+        adaptor0 = SymmetricTwoportAdaptor(
+            coeff,
+            input_op,
+            latency=latency,
+            latency_offsets=latency_offsets,
+            execution_time=execution_time,
+        )
+        signal_out = Signal(adaptor0.output(0))
+        delay = Delay(adaptor0.output(1))
+        Signal(delay, adaptor0.input(1))
+    else:
+        signal_out = Signal(input_op)
+
     # Second-order sections
-    sos_count = (len(coefficients) - 1) // 2
+    sos_count = (order - 1) // 2 if odd_order else order // 2
+    offset1, offset2 = (1, 2) if odd_order else (0, 1)
     for n in range(sos_count):
         adaptor1 = SymmetricTwoportAdaptor(
-            coefficients[2 * n + 1],
+            coefficients[2 * n + offset1],
             signal_out,
             latency=latency,
             latency_offsets=latency_offsets,
@@ -60,7 +96,7 @@ def wdf_allpass(
         delay1 = Delay(adaptor1.output(1))
         delay2 = Delay()
         adaptor2 = SymmetricTwoportAdaptor(
-            coefficients[2 * n + 2],
+            coefficients[2 * n + offset2],
             delay1,
             delay2,
             latency=latency,
@@ -72,4 +108,4 @@ def wdf_allpass(
         signal_out = Signal(adaptor1.output(0))
 
     output << signal_out
-    return SFG([input_op], [output], name=name)
+    return SFG([input_op], [output], name=Name(name))