iir_designs.hpp

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// toolboxes/signal/include/nk/signal/filter_design/iir_designs.hpp
//
// Top-level IIR filter designs that compose the analog prototypes
// (cheb1ap / cheb2ap / besselap / ellipap) with the LP→{HP,BP,BS}
// frequency transforms, zp2tf, and bilinear.
 
#pragma once
 
#include <memory_resource>
#include <nk/value/value.hpp>
 
#include <string>
#include <string_view>
#include <tuple>
 
namespace nk::signal {

 

enum class FilterType {
    Lowpass,   
    Highpass,  
    Bandpass,  
    Bandstop   
};

std::tuple<Value, Value>
cheby1(int                          N,
       double                       Rp,
       const Value &                Wn,
       FilterType                   ftype  = FilterType::Lowpass,
       bool                         analog = false,
       std::pmr::memory_resource *  mr     = nullptr);

std::tuple<Value, Value>
cheby2(int                          N,
       double                       Rs,
       const Value &                Wn,
       FilterType                   ftype  = FilterType::Lowpass,
       bool                         analog = false,
       std::pmr::memory_resource *  mr     = nullptr);

std::tuple<Value, Value>
besself(int                          N,
        const Value &                Wn,
        FilterType                   ftype  = FilterType::Lowpass,
        bool                         analog = false,
        std::pmr::memory_resource *  mr     = nullptr);

std::tuple<Value, Value>
butter(int                          N,
       const Value &                Wn,
       FilterType                   ftype  = FilterType::Lowpass,
       bool                         analog = false,
       std::pmr::memory_resource *  mr     = nullptr);

std::tuple<Value, Value>
ellip(int                          N,
      double                       Rp,
      double                       Rs,
      const Value &                Wn,
      FilterType                   ftype  = FilterType::Lowpass,
      bool                         analog = false,
      std::pmr::memory_resource *  mr     = nullptr);
 
// ─────────────────────────────────────────────────────────────────────
// Order estimators — pick the minimum order to meet given specs.
// ─────────────────────────────────────────────────────────────────────

std::tuple<int, Value>
buttord(const Value &                Wp,
        const Value &                Ws,
        double                       Rp,
        double                       Rs,
        bool                         analog = false,
        std::pmr::memory_resource *  mr     = nullptr);

std::tuple<int, Value>
cheb1ord(const Value &Wp, const Value &Ws, double Rp, double Rs,
         bool analog = false,
         std::pmr::memory_resource *mr = nullptr);

std::tuple<int, Value>
cheb2ord(const Value &Wp, const Value &Ws, double Rp, double Rs,
         bool analog = false,
         std::pmr::memory_resource *mr = nullptr);

std::tuple<int, Value>
ellipord(const Value &Wp, const Value &Ws, double Rp, double Rs,
         bool analog = false,
         std::pmr::memory_resource *mr = nullptr);

std::tuple<int, Value, Value, Value>
firpmord(const Value &                F,
         const Value &                A,
         const Value &                dev,
         double                       fs = 2.0,
         std::pmr::memory_resource *  mr = nullptr);

std::tuple<int, Value, double, std::string>
kaiserord(const Value &                F,
          const Value &                A,
          const Value &                dev,
          double                       fs = 2.0,
          std::pmr::memory_resource *  mr = nullptr);
 

} // namespace nk::signal