diff --git a/dcs/frames/__init__.py b/dcs/frames/__init__.py
index 82c94ce..75d062e 100644
--- a/dcs/frames/__init__.py
+++ b/dcs/frames/__init__.py
@@ -18,6 +18,7 @@
 from .ch05_modulation import Ch05ModulationWindow
 from .ch05_iq import Ch05IqWindow
 from .ch05_qam import Ch05QamWindow
+from .ch06_filter import Ch06FilterWindow
 
 
 def get_windows() -> List[Type[base.Window]]:
@@ -33,6 +34,7 @@
         Ch05ModulationWindow,
         Ch05IqWindow,
         Ch05QamWindow,
+        Ch06FilterWindow,
     ]
 
 
diff --git a/dcs/frames/ch06_filter.py b/dcs/frames/ch06_filter.py
new file mode 100644
index 0000000..423da73
--- /dev/null
+++ b/dcs/frames/ch06_filter.py
@@ -0,0 +1,406 @@
+#  SPDX-License-Identifier: MPL-2.0
+#    Copyright (c) 2022 Philipp Le <philipp@philipple.de>.
+#  This Source Code Form is subject to the terms of the Mozilla Public
+#  License, v. 2.0. If a copy of the MPL was not distributed with this
+#  file, You can obtain one at https://mozilla.org/MPL/2.0/.
+
+from __future__ import annotations
+
+from tkinter import ttk, Listbox, LEFT, BOTH, BOTTOM, ACTIVE
+from tkinter.simpledialog import Dialog
+from pydantic import confloat, conint
+from dcs.config import default_store, ConfigObject, ui_create, ConfigControlFrame
+import numpy as np
+import scipy.signal
+from dcs.frames.base import BaseFrame, Window
+from dcs.frames.groups import Ch06Group
+from typing import List, Tuple, Optional
+from enum import Enum
+
+import matplotlib
+matplotlib.use('TkAgg')
+from matplotlib.pyplot import Circle
+from matplotlib.figure import Figure
+from matplotlib.backends.backend_tkagg import FigureCanvasTkAgg, NavigationToolbar2Tk
+
+
+class FilterType(str, Enum):
+    LOW = 'Low-pass'
+    HIGH = 'High-pass'
+    PASS = 'Band-pass'
+    STOP = 'Band-stop'
+
+
+class FilterDesignMethod(str, Enum):
+    BUTTER = 'Butterworth (IIR)'
+    CHEBY1 = 'Chebyshev type I (IIR)'
+    FIR_WIN = 'Windowing Method (FIR)'
+
+
+@ui_create
+class FilterDesigner(ConfigObject):
+    sample_rate: float
+
+    filter_type: FilterType = FilterType.LOW
+    cutoff: confloat(ge=0.0, lt=1000.0, multiple_of=0.1) = 25
+    width: confloat(ge=0.0, lt=1000.0, multiple_of=0.1) = 5
+    design_method: FilterDesignMethod = FilterDesignMethod.BUTTER
+    order: conint(ge=0, lt=100) = 7
+
+    def make_config_widget(self, parent: ttk.Widget) -> ConfigControlFrame:
+        frm = ConfigControlFrame(parent)
+
+        ttk.Label(frm, text='Filter Type:').grid(row=0, column=0)
+        w = self.ui_create_filter_type_dropdown(frm)
+        frm.add_widget(w)
+        w.grid(row=0, column=1)
+
+        ttk.Label(frm, text='Cut-off Frequency:').grid(row=1, column=0)
+        w = self.ui_create_cutoff(frm)
+        frm.add_widget(w)
+        w.grid(row=1, column=1)
+        ttk.Label(frm, text='Hz').grid(row=1, column=2)
+
+        ttk.Label(frm, text='Bandwidth (only Band-pass/-stop):').grid(row=2, column=0)
+        w = self.ui_create_width(frm)
+        frm.add_widget(w)
+        w.grid(row=2, column=1)
+        ttk.Label(frm, text='Hz').grid(row=2, column=2)
+
+        ttk.Label(frm, text='Design Method:').grid(row=3, column=0)
+        w = self.ui_create_design_method_dropdown(frm)
+        frm.add_widget(w)
+        w.grid(row=3, column=1)
+
+        ttk.Label(frm, text='Filter Order:').grid(row=4, column=0)
+        w = self.ui_create_order(frm)
+        frm.add_widget(w)
+        w.grid(row=4, column=1)
+
+        return frm
+
+    @classmethod
+    def make_dialog(cls, parent: ttk.Widget, sample_rate: float) -> Optional[FilterDesigner]:
+        class DesignDialog(Dialog):
+            def __init__(self, *args, **kwargs):
+                self._cfg: FilterDesigner = cls(sample_rate=sample_rate)
+                self.config: Optional[FilterDesigner] = None
+                super().__init__(*args, **kwargs)
+
+            def body(self, master) -> None:
+                frm = self._cfg.make_config_widget(master)
+                frm.pack()
+
+            def buttonbox(self):
+                box = ttk.Frame(self)
+
+                w = ttk.Button(box, text="OK", width=10, command=self.ok, default=ACTIVE)
+                w.pack(side=LEFT, padx=5, pady=5)
+                self.bind("<Return>", self.ok)
+
+                w = ttk.Button(box, text="Cancel", width=10, command=self.cancel)
+                w.pack(side=LEFT, padx=5, pady=5)
+                self.bind("<Escape>", self.cancel)
+
+                box.pack()
+
+            def apply(self):
+                self.config = self._cfg
+
+        diag = DesignDialog(parent)
+        return diag.config
+
+    def make_filter(self) -> Tuple[np.ndarray, np.ndarray]:
+        iir_param = {
+            'N': self.order,
+            'Wn': None,
+            'btype': '',
+            'analog': False,
+            'output': 'ba',
+            'fs': self.sample_rate,
+        }
+        fir_param = {
+            'numtaps': self.order,
+            'cutoff': None,
+            'window': 'blackman',
+            'pass_zero': '',
+            'fs': self.sample_rate,
+        }
+        if self.filter_type == FilterType.LOW:
+            iir_param['Wn'] = self.cutoff
+            iir_param['btype'] = 'lowpass'
+            fir_param['cutoff'] = self.cutoff
+            fir_param['pass_zero'] = 'lowpass'
+        elif self.filter_type == FilterType.HIGH:
+            iir_param['Wn'] = self.cutoff
+            iir_param['btype'] = 'highpass'
+            fir_param['cutoff'] = self.cutoff
+            fir_param['pass_zero'] = 'highpass'
+        elif self.filter_type == FilterType.PASS:
+            iir_param['Wn'] = (self.cutoff - (self.width/2), self.cutoff + (self.width/2))
+            iir_param['btype'] = 'bandpass'
+            fir_param['cutoff'] = (self.cutoff - (self.width/2), self.cutoff + (self.width/2))
+            fir_param['pass_zero'] = 'bandpass'
+        elif self.filter_type == FilterType.STOP:
+            iir_param['Wn'] = (self.cutoff - (self.width/2), self.cutoff + (self.width/2))
+            iir_param['btype'] = 'bandstop'
+            fir_param['cutoff'] = (self.cutoff - (self.width/2), self.cutoff + (self.width/2))
+            fir_param['pass_zero'] = 'bandstop'
+        else:
+            raise Exception('Invalid filter type')
+
+        if self.design_method == FilterDesignMethod.BUTTER:
+            b, a = scipy.signal.butter(**iir_param)
+            return b, a
+        elif self.design_method == FilterDesignMethod.CHEBY1:
+            b, a = scipy.signal.cheby1(**iir_param, rp=1)
+            return b, a
+        elif self.design_method == FilterDesignMethod.FIR_WIN:
+            b = scipy.signal.firwin(**fir_param)
+            return b, np.array([])
+        else:
+            raise Exception('Invalid design method')
+
+
+@ui_create
+class PolyCoeff(ConfigObject):
+    real: str = '0.0'
+    imag: str = ''
+
+    def make_config_widget(self, parent: ttk.Widget) -> ConfigControlFrame:
+        frm = ConfigControlFrame(parent)
+
+        ttk.Label(frm, text='Real:').grid(row=0, column=0)
+        w = self.ui_create_real(frm)
+        frm.add_widget(w)
+        w.grid(row=0, column=1)
+
+        ttk.Label(frm, text='Imaginary:').grid(row=1, column=0)
+        w = self.ui_create_imag(frm)
+        frm.add_widget(w)
+        w.grid(row=1, column=1)
+
+        return frm
+
+    def get(self) -> complex:
+        val = 0 + 0j
+        try:
+            val += float(self.real)
+            val += 1j * float(self.imag)
+        except ValueError:
+            pass
+        return val
+
+    def make_title(self):
+        if self.get().imag == 0:
+            return f'{self.get().real}'
+        else:
+            return f'{self.get().real} + j {self.get().imag}'
+
+
+class ConfigCh06FilterFrame(ConfigControlFrame):
+    wdg_poly_b_box: Listbox
+    wdg_poly_a_box: Listbox
+
+
+@ui_create
+class ConfigCh06Filter(ConfigObject):
+    _KEY = 'ch06_filter'
+
+    sample_rate: confloat(ge=0.0, lt=1000.0, multiple_of=0.1) = 100
+    poly_b: List[PolyCoeff] = [PolyCoeff(real='1.0')]
+    poly_a: List[PolyCoeff] = []
+
+    def _sample_cfg(self, parent: ConfigControlFrame):
+        frm = ttk.Frame(parent, borderwidth=1, relief='raised')
+        frm.pack()
+
+        ttk.Label(frm, text='Sampling Rate:').grid(row=0, column=0)
+        w = self.ui_create_sample_rate(frm)
+        parent.add_widget(w)
+        w.grid(row=0, column=1)
+        ttk.Label(frm, text='Hz').grid(row=0, column=2)
+
+    def make_config_widget(self, parent: ttk.Widget) -> ConfigCh06FilterFrame:
+        frm = ConfigCh06FilterFrame(parent, borderwidth=1, relief='raised')
+
+        self._sample_cfg(frm)
+
+        ttk.Label(frm, text='Numerator Coefficients:').pack()
+        frm.wdg_poly_b_box = self.ui_create_poly_b_list(frm, lambda e: e.make_title())
+        frm.add_widget(frm.wdg_poly_b_box)
+        frm.wdg_poly_b_box.pack()
+
+        ttk.Label(frm, text='Denominator Coefficients:').pack()
+        frm.wdg_poly_a_box = self.ui_create_poly_a_list(frm, lambda e: e.make_title())
+        frm.add_widget(frm.wdg_poly_a_box)
+        frm.wdg_poly_a_box.pack()
+
+        ttk.Button(frm, text='Generate Filter', command=lambda: self._generate(parent, frm)).pack()
+
+        return frm
+
+    def _generate(self, parent: ttk.Widget, frm: ConfigCh06FilterFrame):
+        cfg = FilterDesigner.make_dialog(parent, self.sample_rate)
+        if cfg is not None:
+            b, a = cfg.make_filter()
+            self.poly_b = [PolyCoeff(real=str(x.real), imag=str(x.imag)) for x in b]
+            self.poly_a = [PolyCoeff(real=str(x.real), imag=str(x.imag)) for x in a]
+            frm.wdg_poly_b_box.sync_in()
+            frm.wdg_poly_a_box.sync_in()
+            frm.wdg_poly_b_box.sync_out()
+            frm.wdg_poly_a_box.sync_out()
+
+    def get_poly(self) -> Tuple[List[complex], List[complex]]:
+        b = [x.get() for x in self.poly_b]
+        a = [x.get() for x in self.poly_a]
+        if len(b) == 0:
+            b = [1]
+        if len(a) == 0:
+            a = [1]
+        return b, a
+
+    def get_dlti(self) -> scipy.signal.dlti:
+        b, a = self.get_poly()
+        return scipy.signal.dlti(b, a, dt=1/self.sample_rate)
+
+    def get_zpk(self) -> Tuple[np.ndarray, np.ndarray, float]:
+        b, a = self.get_poly()
+        return scipy.signal.tf2zpk(b, a)
+
+
+class Ch06FilterFrame(BaseFrame):
+    def __init__(self, *args, **kwargs):
+        super().__init__(*args, **kwargs)
+
+        self._config: ConfigCh06Filter = default_store().get_config(ConfigCh06Filter)
+
+        ctrl_frm = self._create_control()
+        ctrl_frm.pack(side=LEFT)
+
+        signal_frm = self._create_signal_tabs()
+        signal_frm.pack(expand=True, fill=BOTH)
+
+    def _create_control(self) -> ConfigControlFrame:
+        frm = self._config.make_config_widget(self)
+        frm.widgets_on_change(self._on_change)
+        return frm
+
+    def _on_change(self, _, __, ___):
+        default_store().save()
+        self.draw_bode()
+        self.draw_impulse()
+        self.draw_pz()
+
+    def _create_signal_tabs(self) -> ttk.Widget:
+        tabs = ttk.Notebook(self)
+
+        bode_frm = ttk.Frame(tabs)
+        tabs.add(bode_frm, text='Bode Plot')
+        self._bode_fig = Figure(figsize=(12, 6), dpi=100)
+        self._bode_canvas = FigureCanvasTkAgg(self._bode_fig, bode_frm)
+        self._bode_canvas.get_tk_widget().pack(expand=True, fill=BOTH)
+        bode_tb = NavigationToolbar2Tk(self._bode_canvas, bode_frm, pack_toolbar=False)
+        bode_tb.pack(side=BOTTOM)
+
+        impulse_frm = ttk.Frame(tabs)
+        tabs.add(impulse_frm, text='Impulse Response')
+        self._impulse_fig = Figure(figsize=(12, 6), dpi=100)
+        self._impulse_canvas = FigureCanvasTkAgg(self._impulse_fig, impulse_frm)
+        self._impulse_canvas.get_tk_widget().pack(expand=True, fill=BOTH)
+        impulse_tb = NavigationToolbar2Tk(self._impulse_canvas, impulse_frm, pack_toolbar=False)
+        impulse_tb.pack(side=BOTTOM)
+
+        pz_frm = ttk.Frame(tabs)
+        tabs.add(pz_frm, text='Pole-Zero Map')
+        self._pz_fig = Figure(figsize=(12, 6), dpi=100)
+        self._pz_canvas = FigureCanvasTkAgg(self._pz_fig, pz_frm)
+        self._pz_canvas.get_tk_widget().pack(expand=True, fill=BOTH)
+        pz_tb = NavigationToolbar2Tk(self._pz_canvas, pz_frm, pack_toolbar=False)
+        pz_tb.pack(side=BOTTOM)
+
+        self.draw_bode()
+        self.draw_impulse()
+        self.draw_pz()
+
+        return tabs
+
+    def draw_bode(self):
+        self._bode_fig.clear()
+
+        ax_mag = self._bode_fig.add_subplot(2, 1, 1)
+        ax_mag.set_xlabel('frequency')
+        ax_mag.set_ylabel('magnitude (dB)')
+        ax_mag.set_title('Magnitude Plot')
+        ax_pha = self._bode_fig.add_subplot(2, 1, 2)
+        ax_pha.set_xlabel('frequency')
+        ax_pha.set_ylabel('phase (°)')
+        ax_pha.set_title('Phase Plot')
+
+        w, mag, pha = scipy.signal.dbode(self._config.get_dlti(), n=1024)
+        f = w / (2 * np.pi)
+        ax_mag.plot(f, mag, label='Magnitude', linestyle='solid', color='blue', linewidth=1)
+        ax_mag.plot((0, np.max(f)), np.array([np.max(mag)-3]).repeat(2), label='-3 dB', linestyle='dotted', color='red', linewidth=1)
+        ax_mag.legend()
+        ax_pha.plot(f, np.unwrap(pha, discont=360), linestyle='solid', color='green', linewidth=1)
+
+        ax_mag.set_ylim(np.clip(np.min(mag), -80, None), np.max(mag)+5)
+
+        self._bode_fig.tight_layout()
+        self._bode_canvas.draw()
+
+    def draw_impulse(self):
+        self._impulse_fig.clear()
+
+        ax_ir = self._impulse_fig.add_subplot(1, 1, 1)
+        ax_ir.set_xlabel('time')
+        ax_ir.set_ylabel('value')
+        ax_ir.set_title('Impulse Response')
+
+        try:
+            order = len(self._config.poly_b) + len(self._config.poly_a)
+            t, y = scipy.signal.dimpulse(self._config.get_dlti(), n=order * 32)
+            y = y[0]
+            ax_ir.plot(t, np.squeeze(np.real(y)), label='Real', linestyle='solid', color='blue', linewidth=1)
+            if (np.min(np.imag(y)) != 0.0) or (np.max(np.imag(y)) != 0.0):
+                ax_ir.plot(t, np.squeeze(np.imag(y)), label='Imag', linestyle='solid', color='blue', linewidth=1)
+            ax_ir.legend()
+        except ValueError as e:
+            print(repr(e))
+
+        self._impulse_fig.tight_layout()
+        self._impulse_canvas.draw()
+
+    def draw_pz(self):
+        self._pz_fig.clear()
+
+        ax_pz = self._pz_fig.add_subplot(1, 1, 1)
+        ax_pz.set_xlabel('real')
+        ax_pz.set_ylabel('imag')
+        ax_pz.set_title('Pole-Zero Map')
+        ax_pz.set_aspect(1)
+
+        ax_pz.add_artist(Circle((0, 0), 1, color='red', fill=False, label='Circle of Unity'))
+
+        z, p, k = self._config.get_zpk()
+        ax_pz.scatter(np.real(p), np.imag(p), marker='x', label='Poles', color='blue', linewidth=1)
+        ax_pz.scatter(np.real(z), np.imag(z), marker='o', label='Zeroes', color='blue', linewidth=1)
+        ax_pz.legend()
+
+        concat = np.concatenate((p, z))
+        ax_pz.set_xlim(np.clip(np.min(np.real(concat)) + 0.2, None, -1.2), np.clip(np.max(np.real(concat)) + 0.2, 1.2, None))
+        ax_pz.set_ylim(np.clip(np.min(np.imag(concat)) + 0.2, None, -1.2), np.clip(np.max(np.imag(concat)) + 0.2, 1.2, None))
+
+        self._pz_fig.tight_layout()
+        self._pz_canvas.draw()
+
+
+class Ch06FilterWindow(Window):
+    GROUP = Ch06Group
+    TITLE = 'Digital Filter'
+    FRAME = Ch06FilterFrame
+
+
+if __name__ == '__main__':
+    Ch06FilterWindow.main()
+
diff --git a/dcs/frames/groups.py b/dcs/frames/groups.py
index b3c8d10..4a5a0f2 100644
--- a/dcs/frames/groups.py
+++ b/dcs/frames/groups.py
@@ -21,3 +21,7 @@
 
 class Ch05Group(Group):
     NAME = 'Chapter 05'
+
+
+class Ch06Group(Group):
+    NAME = 'Chapter 06'