ScopeFIR™ is the premier software tool for Finite Impulse Response (FIR) filter design. It can:

Design multi-band Complex FIR filters of the following types:

• Parks-McClellan (Equiripple). ScopeFIR can design Filters, Hilbert Transformers, or Differentiators. Its "Simple Filter Specification Editor" allows you to easily design simple single-passband filters, and its "Advanced Filter Specification Editor" gives you access to the full capability of the Parks-McClellan algorithm by allowing you to enter any number of pass/stop bands, with any edge frequencies. ScopeFIR lets you enter frequencies in terms of the sample rate, and enter band response specifications in your choice of linear or dB units. Its "Optimize" feature searches for the minimum number of taps which meets specifications.
• Windowed Sinc. ScopeFIR can design lowpass, highpass, bandpass, or bandstop filters with user-specified band edge frequencies, and using any of its built-in data windows, including Dolph-Chebyshev, Blackman-Harris, Kaiser-Bessel (with choice of Alpha), Hamming, Hanning, and Gaussian.
• Lth-Band. ScopeFIR can design special computationally efficient Lth-band (Nyquist) filters, including half-band filters.
• Raised Cosine. ScopeFIR automatically designs Raised Cosine and Root Raised Cosine filters (commonly used in digital data communications systems) with the specified rolloff factor and length.
• Maxflat. ScopeFIR can design lowpass FIR filters having a maximally flat passband.
• Cascaded Integrator-Comb. ScopeFIR can design CIC filters, which are widely used in hardware-based multirate applications.
• Import. ScopeFIR lets you import filters which have been designed with another application so you can analyze them using ScopeFIR's powerful plotting and analysis capabilities, and to modify them using ScopeFIR's powerful filter modification capabilities.
• Boxcar. ScopeFIR lets you fill the N taps with a constant to create a boxcar (or comb) filter.

Analyze FIR filters by:

• Examining the actual band ripple and attenuation values in the Band Editor.
• Plotting the Frequency Response. ScopeFIR can plot the Magnitude, Phase, Unwrapped Phase, Group Delay, and Phase Delay of the Inphase, Quadrature, or Complex filters. Plots feature a sophisticated multi-level zooming capability, and are similar to ScopeDSP's plots.
• Plotting the Impulse Response. ScopeFIR can plot the magnitude or phase of the Inphase, Quadrature, or Complex Filter Impulse Responses.
• Viewing the coefficients in the Coefficient Editor. ScopeFIR lets you view the Inphase and/or Quadrature coefficients in decimal, binary or hex formats. Coefficients can be copied to/from the Windows clipboard.

Modify FIR filters by:

• Scaling. Changes the gain of the filter. The coefficients can be automatically scaled to a given gain at a given frequency, or can be automatically scaled to a given maximum coefficient magnitude.
• Quantizing. Coefficients can be quantized to N bits.
• Mixing. The mix function mixes the coefficients with a sine of a given frequency, which creates a complex bandpass filter with a new center frequency from a real filter that was designed previously.
• Editing. ScopeFIR's built-in Coefficient Editor lets you manually edit the coefficients in decimal, binary or hex text formats, then plot the altered frequency and impulse responses.
• Convolving. Two or more filters can be convolved to create a single filter whose response is equivalent to the cascaded response.
• Zero-Stuffing, Zero-Padding, and Truncating. Allows you to fine-tune the number of coefficients in your filter.
• Selecting a Polyphase Subfilter. Helps you create filters which have fractional-sample delays .

Interface with your compiler or other programs by:

• Reading and writing Real or Complex FIR filter coefficients as text, C arrays, or in any of Iowegian's large number of common data file formats.

Of course, ScopeFIR also includes many graphical user interface goodies to make your life in DSP a little easier.

The ScopeFIR distribution file also includes:

• A comprehensive set of example ScopeFIR project files to get you started on FIR designs of all types.
• fir_algs.c: a free and open collection of FIR filter algorithms to help you implement FIR filters in C.
• multirate_algs.c: a free and open collection of multirate FIR filter algorithms to help you implement FIR decimators, interpolators, and resamplers in C.