Sine Cosine Generator

Overview

Sine and Cosine Waves

sin_cos_gen is an oscillator that simultaneously generates sine and cosine waveforms. sin_cos_gen is implemented utilizing Hal Chamberlin’s state variable IIR filter, a digital derivation of the analog state variable filter optimized for infinite Q oscillation. sin_cos_gen is suitable as a low frequency sine wave oscillator. The upper frequency limit for stability is roughly 1/6 sps. At low frequencies, the waveform symmetry is very pure, but it becomes skewed as you approach the upper limit. For low frequencies, we can reduce the calculation of the coefficient to 2*Pi*freq/sps. When utilized with fixed point or IEEE floating point, the oscallator should run forever without instability.

While sin_cos_gen is technically an oscillator which generates periodic waveforms, it is presented as a model of Generator because it does not conform to the Oscillator concept which requires complete control over the phase.

Although sin_cos_gen is technically an oscillator that produces periodic waveforms, it is represented as a model of a Generator because it does not adhere to the Oscillator concept, which requires complete control over the phase for synchronicity. As a free-running oscillator,sin_cos_gen can exhibit phase drift over time due to accumulating floating-point errors.

Source: The digital state variable filter

Include

#include <q/synth/sin_cos_gen.hpp>

Declaration

struct sin_cos_gen
{
                              sin_cos_gen(frequency f, float sps);

   std::pair<float, float>    operator()();
   void                       config(frequency f, float sps);
   void                       reset(float sin = 0.0f, float cos = 1.0f);
   void                       midpoint();
};

Expressions

sin_cos_gen is a model of Generator. In addition to valid expressions for Generator, sin_cos_gen allows these expressions.

Notation

g: Object of type sin_cos_gen.
f: Object of type frequency.
sps: Floating point value representing samples per second.
sval, cval: Floating point value values.

Constructor

Expression Semantics

Expression	Semantics
`sin_cos_gen(f, sps)`	Construct `sin_cos_gen` given frequency, `f`, and samples per second, `sps`.

sin_cos_gen(f, sps)

Construct sin_cos_gen given frequency, f, and samples per second, sps.

C++ brace initialization may also be used.

Function Call

Expression Semantics Return Type

Expression	Semantics	Return Type
`g()`	Generate a sin/cos signal and get both `sin` and `cos` result. The return type is a `std::pair<float, float>` which stores the `sin` and `cos` results.	`std::pair<float, float>`
`g().first`	Generate a sin/cos signal and get only the `sin` result.	`float`
`g().second`	Generate a sin/cos signal and get only the `cos` result.	`float`

g()

Generate a sin/cos signal and get both sin and cos result. The return type is a std::pair<float, float> which stores the sin and cos results.

std::pair<float, float>

g().first

Generate a sin/cos signal and get only the sin result.

float

g().second

Generate a sin/cos signal and get only the cos result.

float

Mutators

Expression Semantics

Expression	Semantics
`g.config(f, sps)`	Set the frequency, `f`, with samples per second, `sps`.
`g.reset()`	Reset the current `sin` and `cos` to 0.0f and 1.0f, respectively.
`g.reset(sval, cval)`	Reset the current `sin` and `cos` values, respectively.
`g.midpoint()`	Equivalent to `g.reset(0.0f, -1.0f)`.

g.config(f, sps)

Set the frequency, f, with samples per second, sps.

g.reset()

Reset the current sin and cos to 0.0f and 1.0f, respectively.

g.reset(sval, cval)

Reset the current sin and cos values, respectively.

g.midpoint()

Equivalent to g.reset(0.0f, -1.0f).