Add WDF allpass generator

Closes #156 (closed)

b_asic/sfg_generator.py

+"""
+B-ASIC signal flow graph generators.
+
+This module contains a number of functions generating SFGs for specific functions.
+"""
+from typing import Dict, Optional, Sequence, Union
+
+import numpy as np
+
+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
+from b_asic.special_operations import Delay, Input, Output
+
+
+def wdf_allpass(
+    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:
+        raise TypeError("coefficients must be a 1D-array")
+    if input_op is None:
+        input_op = Input()
+    if output is None:
+        output = Output()
+    if name is None:
+        name = "WDF allpass section"
+    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 = (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 + offset1],
+            signal_out,
+            latency=latency,
+            latency_offsets=latency_offsets,
+            execution_time=execution_time,
+        )
+        # Signal(prev_adaptor., adaptor1.input(0), name="Previous-stage to next")
+        delay1 = Delay(adaptor1.output(1))
+        delay2 = Delay()
+        adaptor2 = SymmetricTwoportAdaptor(
+            coefficients[2 * n + offset2],
+            delay1,
+            delay2,
+            latency=latency,
+            latency_offsets=latency_offsets,
+            execution_time=execution_time,
+        )
+        Signal(adaptor2.output(1), adaptor1.input(1))
+        Signal(adaptor2.output(0), delay2)
+        signal_out = Signal(adaptor1.output(0))
+
+    output << signal_out
+    return SFG([input_op], [output], name=Name(name))