HLSI/common.js at master · vtwireless/HLSI · GitHub

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/**
 * The following code includes functions for generating signals, creating plots, and implementing a
 * pseudo-random number generator based on the Blum Blum Shub algorithm.
 *
 * @param {Function} _xscale - A D3 scale function used for mapping data values to the x-axis in the
 * SVG plot. Typically created using `d3.scaleLinear()`, `d3.scaleTime()`, or other D3 scale functions,
 * depending on the type of data being visualized.
 * @param {Function} _yscale - A D3 scale function for mapping data values to the y-axis in the SVG plot.
 * This scale is used to determine the positioning of data points and elements along the y-axis.
 * @param {string} [parentElement=null] - A CSS selector string for the parent node to which the D3 `<svg>`
 * plot element will be appended. If no value is provided, it defaults to appending the `<svg>` element
 * to the `<body>` of the document.
 * @returns {Function} Returns either `PowerSpectrumPlot_3D()` or `PowerSpectrumPlot_2D()`, depending on
 * the checked status of the element with the ID `psd_3d_checkbox`. If the checkbox is checked, it will
 * call `PowerSpectrumPlot_3D()`; otherwise, it calls `PowerSpectrumPlot_2D()`.
 */

"use strict";

// All the plots use these length parameters and they are used in other
// files too.
//
var plot = {
  margin: { top: 10, right: 50, bottom: 50, left: 50 },
};

plot.width = 720 - plot.margin.left - plot.margin.right; // Use the window's width
plot.height = 320 - plot.margin.top - plot.margin.bottom; // Use the window's height

Object.freeze(plot);

// parentElement is a CSS selector for the parent node that we will append
// the d3 <svg> plot element to.
//
function svg_create(_xscale, _yscale, parentElement = null) {
  if (parentElement === null) parentElement = "body";

  // We need to add data to the object that is what we are given, svg.
  // We did not start this fun code so in order to refactor it without
  // braking it we need to use kludgey methods like so:

  // 1. Add the SVG (time) to the page and employ #2
  var svg = d3
    .select(parentElement)
    .append("svg")
    .attr("width", plot.width + plot.margin.left + plot.margin.right)
    .attr("height", plot.height + plot.margin.top + plot.margin.bottom)
    .append("g")
    .attr("class", "graph-svg-component")
    .attr(
      "transform",
      "translate(" + plot.margin.left + "," + plot.margin.top + ")"
    );

  // create axes
  svg
    .append("g")
    .attr("class", "x axis")
    .attr("transform", "translate(0," + plot.height + ")")
    .call(d3.axisBottom(_xscale));
  svg.append("g").attr("class", "y axis").call(d3.axisLeft(_yscale));

  svg
    .append("rect")
    .attr("width", "86.2%")
    .attr("height", "81%")
    .attr("fill", "black");

  // create grid lines
  svg
    .append("g")
    .attr("class", "grid")
    .call(d3.axisBottom(_xscale).tickFormat("").tickSize(plot.height));
  svg
    .append("g")
    .attr("class", "grid")
    .call(d3.axisLeft(_yscale).tickFormat("").tickSize(-plot.width));

  return svg;
}

function svg_add_labels(_svg, _xlabel, _ylabel) {
  // create x-axis axis label
  _svg
    .append("text")
    .attr(
      "transform",
      "translate(" +
        plot.width / 2 +
        "," +
        (plot.height + 0.75 * plot.margin.bottom) +
        ")"
    )
    .attr("dy", "-0.3em")
    .style("text-anchor", "middle")
    .attr("fill", "white")
    .text(_xlabel);

  // create y-axis label
  _svg
    .append("text")
    .attr("transform", "rotate(-90)")
    .attr("y", 0 - plot.margin.left)
    .attr("x", 0 - plot.height / 2)
    .attr("dy", "1em")
    .style("text-anchor", "middle")
    .attr("fill", "white")
    .text(_ylabel);
}

// determine scale and units for sample value v; use p to adjust cut-off threshold
function scale_units(v, p = 1) {
  let r = v * p;
  if (r >= 1e12) {
    return [1e-12, "T"];
  } else if (r >= 1e9) {
    return [1e-9, "G"];
  } else if (r >= 1e6) {
    return [1e-6, "M"];
  } else if (r >= 1e3) {
    return [1e-3, "k"];
  } else if (r >= 1) {
    return [1, ""];
  } else if (r >= 1e-3) {
    return [1e3, "m"];
  } else if (r >= 1e-6) {
    return [1e6, "u"];
  } else if (r >= 1e-9) {
    return [1e9, "n"];
  } else if (r >= 1e-12) {
    return [1e12, "p"];
  } else {
    return [1e16, "f"];
  }
}

// normal random number
function randn() {
  let u1 = 0,
    u2 = Math.random();
  while (u1 == 0) {
    u1 = Math.random();
  }
  return Math.sqrt(-2 * Math.log(u1)) * Math.sin(2 * Math.PI * u2);
}

// sinc(x) = sin(pi x) / (pi x)
function sinc(x) {
  let r = Math.max(1e-6, Math.abs(Math.PI * x));
  return Math.sin(r) / r;
}

// generate sample i of cosine window, length 2*_m+1 with exponent _beta
function cwindow(_i, _m, _beta) {
  if (_i < 0 || _i > 2 * _m) {
    throw "invalid index for cosine window, i=" + _i + ", m=" + _m;
  }
  return (
    Math.cos((0.5 * Math.PI * (_i - _m)) / _m) ** (_beta == null ? 2 : _beta)
  );
}

// generate sample i of windowed pulse, length 2*_m+1 with bandwidth _bw
function pulse(_i, _m, _bw, _beta) {
  if (_i < 0 || _i > 2 * _m) {
    throw "invalid index for pulse, i=" + _i + ", m=" + _m;
  }
  return sinc(_bw * (_i - _m)) * cwindow(_i, _m, _beta);
}

// generate pulse into buffer (adding on top of existing signals)
function add_pulse(_m, _fc, _bw, _gain, _xi, _xq, _beta) {
  let gain = Math.pow(10, _gain / 20);
  for (var i = 0; i < 2 * _m + 1; i++) {
    let p = pulse(i, _m, _bw, _beta);
    _xi[i] += gain * Math.cos(2 * Math.PI * _fc * i) * p;
    _xq[i] += gain * Math.sin(2 * Math.PI * _fc * i) * p;
  }
}

// generate tone into buffer (adding on top of existing signals)
function add_tone(_m, _fc, _gain, _xi, _xq, _beta) {
  let gain = (_gain == null ? 1 : Math.pow(10, _gain / 20)) / _m;
  for (var i = 0; i < 2 * _m + 1; i++) {
    let p = cwindow(i, _m, _beta);
    _xi[i] += gain * Math.cos(2 * Math.PI * _fc * i) * p;
    _xq[i] += gain * Math.sin(2 * Math.PI * _fc * i) * p;
  }
}

// mu-law compression
function compress_mulaw(_x, _mu) {
  if (_mu == null || _mu == 0) {
    return _x;
  } else if (_mu < 0) {
    throw "invalid mu value for compression: " + _mu;
  }

  let x_abs = Math.abs(_x);
  return (Math.sign(_x) * Math.log(1 + _mu * x_abs)) / Math.log(1 + _mu);
}

// clear sample buffer
function clear_buffer(buf, n) {
  for (let i = 0; i < n; i++) {
    buf[i] = 0;
  }
}

// function class to generate signals, power spectral density
function siggen(nfft) {
  this.nfft = nfft;
  this.fft = new FFTNayuki(nfft);
  this.xi = new Array(nfft);
  this.xq = new Array(nfft);
  this.psd = new Array(nfft);
  this.m = Math.min(120, Math.floor(0.4 * nfft)); // filter semi-length
  this.beta = 2; // filter window exponent parameter
  this.mu = null; // mu-law compression (set to 'null' to disable)

  // clear internal buffer
  this.clear = function () {
    clear_buffer(this.xi, this.nfft);
    clear_buffer(this.xq, this.nfft);
  };

  // generate signals in the time-domain buffer
  this.add_signal = function (_fc, _bw, _gain) {
    add_pulse(this.m, _fc, _bw, _gain, this.xi, this.xq, this.beta);
  };

  // add tone in time-domain buffer
  this.add_tone = function (_fc, _gain) {
    add_tone(this.m, _fc, _gain, this.xi, this.xq, this.beta);
  };

  // add noise to time-domain buffer
  this.add_noise = function (noise_floor_dB) {
    // compute noise standard deviation, compensating for fft size and I/Q components
    let nstd = Math.pow(10, noise_floor_dB / 20) / Math.sqrt(2 * this.nfft);
    for (var i = 0; i < this.nfft; i++) {
      this.xi[i] += randn() * nstd;
      this.xq[i] += randn() * nstd;
    }
  };

  // run fft, adding noise floor as appropriate
  this.generate = function (noise_floor_dB) {
    // compute noise floor (minimum prevents possibility of log of zero)
    if (noise_floor_dB == null) {
      noise_floor_dB = -120;
    }
    let noise_floor = Math.max(1e-12, Math.pow(10, noise_floor_dB / 10));

    // apply compression
    if (this.mu != null) {
      for (var i = 0; i < nfft; i++) {
        this.xi[i] = compress_mulaw(this.xi[i], this.mu);
        this.xq[i] = compress_mulaw(this.xq[i], this.mu);
      }
    }

    // compute transform in place
    this.fft.forward(this.xi, this.xq);

    // convert to dB (adding noise floor as appropriate), and apply fft shift
    for (var i = 0; i < this.nfft; i++) {
      let x2 = this.xi[i] ** 2 + this.xq[i] ** 2;
      this.psd[(i + this.nfft / 2) % nfft] = 10 * Math.log10(noise_floor + x2);
    }
  };
}

// basic pseudo-random number generator based on Blum Blum Shub algorithm
function prng_bbs() {
  this.p = (1 << 17) - 1;
  this.q = (1 << 19) - 1;
  this.M = this.p * this.q;
  this.res = 1 << 8; // small number of unique values
  this.v = 3;

  this.reset = function (seed) {
    this.v = seed == null ? 3 : seed;
  };

  this.step = function () {
    this.v = (this.v * this.v) % this.M;
    return (this.v & (this.res - 1)) / this.res;
  };
}

function power_spectral_density_3d_checkbox_change() {
  if (document.getElementById("psd_3d_checkbox").checked) {
    PowerSpectrumPlot_3D();
  } else {
    PowerSpectrumPlot_2D();
  }
}