FMCW symmetric triangular modulation signal implementation. More...

#include "radar_signal.h"

Inheritance diagram for fers_signal::FmcwTriangleSignal:

Collaboration diagram for fers_signal::FmcwTriangleSignal:

Public Member Functions
	FmcwTriangleSignal (RealType chirp_bandwidth, RealType chirp_duration, RealType start_frequency_offset=0.0, std::optional< std::size_t > triangle_count=std::nullopt)
	Constructs an FMCW triangular modulation signal.

	~FmcwTriangleSignal () override=default

	FmcwTriangleSignal (const FmcwTriangleSignal &) noexcept=delete

FmcwTriangleSignal &	operator= (const FmcwTriangleSignal &) noexcept=delete

	FmcwTriangleSignal (FmcwTriangleSignal &&) noexcept=delete

FmcwTriangleSignal &	operator= (FmcwTriangleSignal &&) noexcept=delete

RealType	getChirpBandwidth () const noexcept
	Gets the chirp bandwidth in hertz.

RealType	getChirpDuration () const noexcept
	Gets the per-leg chirp duration in seconds.

RealType	getStartFrequencyOffset () const noexcept
	Gets the start frequency offset relative to carrier in hertz.

const std::optional< std::size_t > &	getTriangleCount () const noexcept
	Gets the optional finite triangle count.

RealType	getChirpRate () const noexcept
	Gets the chirp rate magnitude in hertz per second.

RealType	getTrianglePeriod () const noexcept
	Gets the full up/down triangle period in seconds.

RealType	getDeltaPhiUp () const noexcept
	Gets the full, unreduced phase accumulated by one leg.

bool	isTriangle () const noexcept
	Returns true for triangular FMCW waveforms.

RealType	basebandPhaseForTriangleTime (RealType triangle_time) const noexcept
	Computes baseband phase at a time since the triangle train start.

std::optional< RealType >	instantaneousBasebandPhase (RealType time_since_segment_start) const noexcept
	Computes instantaneous baseband phase at a time since segment start.

std::vector< ComplexType >	render (const std::vector< interp::InterpPoint > &points, unsigned &size, RealType fracWinDelay) const override
	Renders an FMCW waveform from interpolation points.

bool	isFmcwFamily () const noexcept override
	Returns true when this signal belongs to the FMCW waveform family.

void	clear () noexcept
	Clears the internal signal data.

void	load (std::span< const ComplexType > inData, unsigned samples, RealType sampleRate)
	Loads complex radar waveform data.

RealType	getRate () const noexcept
	Gets the sample rate of the signal.

unsigned	getSampleCount () const noexcept
	Gets the number of native samples held by this signal.

virtual std::vector< ComplexType >	renderSlice (const std::vector< interp::InterpPoint > &points, RealType outputStartTime, RealType outputSampleRate, std::size_t sampleCount, RealType fracWinDelay) const
	Renders a bounded absolute-time slice on the requested output grid.

ComplexType	sampleAt (RealType time_since_start) const noexcept
	Samples the finite stored complex envelope using the render interpolation filter.

Detailed Description

FMCW symmetric triangular modulation signal implementation.

Definition at line 518 of file radar_signal.h.

Constructor & Destructor Documentation

◆ FmcwTriangleSignal() [1/3]

fers_signal::FmcwTriangleSignal::FmcwTriangleSignal	(	RealType	chirp_bandwidth,
		RealType	chirp_duration,
		RealType	start_frequency_offset = `0.0`,
		std::optional< std::size_t >	triangle_count = `std::nullopt`
	)

Constructs an FMCW triangular modulation signal.

Definition at line 205 of file radar_signal.cpp.

                                                                                  :
        _chirp_bandwidth(chirp_bandwidth), _chirp_duration(chirp_duration),
        _start_frequency_offset(start_frequency_offset), _triangle_count(triangle_count),
        _chirp_rate(chirp_bandwidth / chirp_duration), _triangle_period(2.0 * chirp_duration),
        _delta_phi_up(2.0 * PI * start_frequency_offset * chirp_duration +
                      PI * _chirp_rate * chirp_duration * chirp_duration)
    {
    }

◆ ~FmcwTriangleSignal()

fers_signal::FmcwTriangleSignal::~FmcwTriangleSignal ( )

overridedefault

◆ FmcwTriangleSignal() [2/3]

fers_signal::FmcwTriangleSignal::FmcwTriangleSignal ( const FmcwTriangleSignal & )

deletenoexcept

◆ FmcwTriangleSignal() [3/3]

fers_signal::FmcwTriangleSignal::FmcwTriangleSignal ( FmcwTriangleSignal && )

deletenoexcept

Member Function Documentation

◆ basebandPhaseForTriangleTime()

RealType fers_signal::FmcwTriangleSignal::basebandPhaseForTriangleTime ( RealType triangle_time ) const

noexcept

Computes baseband phase at a time since the triangle train start.

Definition at line 216 of file radar_signal.cpp.

    {
        if (triangle_time <= 0.0)
        {
            return 0.0;
        }
 
        const auto triangle_index = static_cast<std::size_t>(std::floor(triangle_time / _triangle_period));
        const RealType local_triangle_time = triangle_time - static_cast<RealType>(triangle_index) * _triangle_period;
        const bool down_leg = local_triangle_time >= _chirp_duration;
        const RealType u = down_leg ? local_triangle_time - _chirp_duration : local_triangle_time;
        const RealType phi_base =
            static_cast<RealType>(triangle_index) * 2.0 * _delta_phi_up + (down_leg ? _delta_phi_up : 0.0);
        if (!down_leg)
        {
            return phi_base + 2.0 * PI * _start_frequency_offset * u + PI * _chirp_rate * u * u;
        }
        return phi_base + 2.0 * PI * (_start_frequency_offset + _chirp_bandwidth) * u - PI * _chirp_rate * u * u;
    }

References max, and PI.

◆ clear()

void fers_signal::Signal::clear ( )

noexceptinherited

Clears the internal signal data.

Definition at line 347 of file radar_signal.cpp.

    {
        _size = 0;
        _rate = 0;
    }

Referenced by fers_signal::Signal::load().

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◆ getChirpBandwidth()

RealType fers_signal::FmcwTriangleSignal::getChirpBandwidth ( ) const

noexcept

Gets the chirp bandwidth in hertz.

Definition at line 536 of file radar_signal.h.

536{ return _chirp_bandwidth; }

◆ getChirpDuration()

RealType fers_signal::FmcwTriangleSignal::getChirpDuration ( ) const

noexcept

Gets the per-leg chirp duration in seconds.

Definition at line 539 of file radar_signal.h.

539{ return _chirp_duration; }

◆ getChirpRate()

RealType fers_signal::FmcwTriangleSignal::getChirpRate ( ) const

noexcept

Gets the chirp rate magnitude in hertz per second.

Definition at line 548 of file radar_signal.h.

548{ return _chirp_rate; }

◆ getDeltaPhiUp()

RealType fers_signal::FmcwTriangleSignal::getDeltaPhiUp ( ) const

noexcept

Gets the full, unreduced phase accumulated by one leg.

Definition at line 554 of file radar_signal.h.

554{ return _delta_phi_up; }

◆ getRate()

RealType fers_signal::Signal::getRate ( ) const

noexceptinherited

Gets the sample rate of the signal.

Returns: The sample rate of the signal.

Definition at line 94 of file radar_signal.h.

94{ return _rate; }

◆ getSampleCount()

unsigned fers_signal::Signal::getSampleCount ( ) const

noexceptinherited

Gets the number of native samples held by this signal.

Definition at line 97 of file radar_signal.h.

97{ return _size; }

◆ getStartFrequencyOffset()

RealType fers_signal::FmcwTriangleSignal::getStartFrequencyOffset ( ) const

noexcept

Gets the start frequency offset relative to carrier in hertz.

Definition at line 542 of file radar_signal.h.

542{ return _start_frequency_offset; }

◆ getTriangleCount()

const std::optional< std::size_t > & fers_signal::FmcwTriangleSignal::getTriangleCount ( ) const

noexcept

Gets the optional finite triangle count.

Definition at line 545 of file radar_signal.h.

545{ return _triangle_count; }

◆ getTrianglePeriod()

RealType fers_signal::FmcwTriangleSignal::getTrianglePeriod ( ) const

noexcept

Gets the full up/down triangle period in seconds.

Definition at line 551 of file radar_signal.h.

551{ return _triangle_period; }

◆ instantaneousBasebandPhase()

std::optional< RealType > fers_signal::FmcwTriangleSignal::instantaneousBasebandPhase ( RealType time_since_segment_start ) const

noexcept

Computes instantaneous baseband phase at a time since segment start.

Definition at line 237 of file radar_signal.cpp.

    {
        if (time_since_segment_start < 0.0)
        {
            return std::nullopt;
        }
 
        const auto triangle_index = static_cast<std::size_t>(std::floor(time_since_segment_start / _triangle_period));
        if (_triangle_count.has_value() && triangle_index >= *_triangle_count)
        {
            return std::nullopt;
        }
 
        const RealType local_triangle_time =
            time_since_segment_start - static_cast<RealType>(triangle_index) * _triangle_period;
        if (local_triangle_time < 0.0 || local_triangle_time >= _triangle_period)
        {
            return std::nullopt;
        }
        return basebandPhaseForTriangleTime(time_since_segment_start);
    }

References max.

◆ isFmcwFamily()

bool fers_signal::FmcwTriangleSignal::isFmcwFamily ( ) const

overridevirtualnoexcept

Returns true when this signal belongs to the FMCW waveform family.

Reimplemented from fers_signal::Signal.

Definition at line 570 of file radar_signal.h.

570{ return true; }

◆ isTriangle()

bool fers_signal::FmcwTriangleSignal::isTriangle ( ) const

noexcept

Returns true for triangular FMCW waveforms.

Definition at line 557 of file radar_signal.h.

557{ return true; }

◆ load()

void fers_signal::Signal::load	(	std::span< const ComplexType >	inData,
		unsigned	samples,
		RealType	sampleRate
	)

inherited

Loads complex radar waveform data.

Parameters

inData	The input span of complex signal data.
samples	The number of samples in the input data.
sampleRate	The sample rate of the input data.

Definition at line 353 of file radar_signal.cpp.

    {
        clear();
        const unsigned ratio = params::oversampleRatio();
        const auto oversampled_samples = static_cast<std::size_t>(samples) * static_cast<std::size_t>(ratio);
        if (oversampled_samples > std::numeric_limits<unsigned>::max())
        {
            throw std::overflow_error("Oversampled signal sample count exceeds unsigned range");
        }
        _data.resize(oversampled_samples);
        _size = static_cast<unsigned>(oversampled_samples);
        _rate = sampleRate * static_cast<RealType>(ratio);
 
        if (ratio == 1)
        {
            std::ranges::copy(inData, _data.begin());
        }
        else
        {
            upsample(inData, samples, _data);
        }
    }

References fers_signal::Signal::clear(), max, params::oversampleRatio(), and fers_signal::upsample().

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◆ operator=() [1/2]

FmcwTriangleSignal & fers_signal::FmcwTriangleSignal::operator= ( const FmcwTriangleSignal & )

deletenoexcept

◆ operator=() [2/2]

FmcwTriangleSignal & fers_signal::FmcwTriangleSignal::operator= ( FmcwTriangleSignal && )

deletenoexcept

◆ render()

std::vector< ComplexType > fers_signal::FmcwTriangleSignal::render	(	const std::vector< interp::InterpPoint > &	points,
		unsigned &	size,
		RealType	fracWinDelay
	)		const

overridevirtual

Renders an FMCW waveform from interpolation points.

Reimplemented from fers_signal::Signal.

Definition at line 259 of file radar_signal.cpp.

    {
        size = 0;
        return {};
    }

References max.

◆ renderSlice()

std::vector< ComplexType > fers_signal::Signal::renderSlice	(	const std::vector< interp::InterpPoint > &	points,
		RealType	outputStartTime,
		RealType	outputSampleRate,
		std::size_t	sampleCount,
		RealType	fracWinDelay
	)		const

virtualinherited

Renders a bounded absolute-time slice on the requested output grid.

Definition at line 413 of file radar_signal.cpp.

    {
        auto out = std::vector<ComplexType>(sampleCount);
        if (_size == 0 || _rate <= 0.0 || outputSampleRate <= 0.0 || points.empty())
        {
            return out;
        }
 
        const RealType timestep = 1.0 / outputSampleRate;
        const int filt_length = static_cast<int>(params::renderFilterLength());
        const auto& interp = interp::InterpFilter::getInstance();
 
        auto iter = points.begin();
        auto next = points.size() > 1 ? std::next(iter) : iter;
        const RealType idelay = std::round(_rate * iter->delay);
        RealType sample_time = outputStartTime;
 
        for (std::size_t i = 0; i < sampleCount; ++i)
        {
            while (sample_time > next->time && next != iter)
            {
                iter = next;
                if (std::next(next) != points.end())
                {
                    ++next;
                }
                else
                {
                    break;
                }
            }
 
            auto [amplitude, phase, fdelay, i_sample_unwrap] =
                calculateWeightsAndDelays(iter, next, sample_time, idelay, fracWinDelay);
            const RealType native_position = (sample_time - points.front().time) * _rate;
            const auto source_index = static_cast<int>(std::floor(native_position));
            RealType source_fraction = native_position - static_cast<RealType>(source_index);
            if (source_fraction < 0.0 && source_fraction > -1.0e-12)
            {
                source_fraction = 0.0;
            }
 
            const RealType combined_delay = fdelay + source_fraction;
            const auto delay_unwrap = static_cast<int>(std::floor(combined_delay));
            fdelay = combined_delay - static_cast<RealType>(delay_unwrap);
            i_sample_unwrap += delay_unwrap;
 
            const auto& filt = interp.getFilter(fdelay);
            const ComplexType accum =
                performConvolution(source_index, filt.data(), filt_length, amplitude, i_sample_unwrap);
            out[i] = std::exp(ComplexType(0.0, 1.0) * phase) * accum;
 
            sample_time += timestep;
        }
 
        return out;
    }

References interp::InterpFilter::getInstance(), max, and params::renderFilterLength().

Referenced by fers_signal::Signal::render().

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◆ sampleAt()

ComplexType fers_signal::Signal::sampleAt ( RealType time_since_start ) const

noexceptinherited

Samples the finite stored complex envelope using the render interpolation filter.

Times outside [0, duration) return zero; file-backed signals never wrap implicitly.

Definition at line 376 of file radar_signal.cpp.

    {
        if (_data.empty() || _rate <= 0.0 || !std::isfinite(time_since_start) || time_since_start < 0.0 ||
            time_since_start >= static_cast<RealType>(_size) / _rate)
        {
            return {0.0, 0.0};
        }
 
        const RealType position = time_since_start * _rate;
        const auto center = static_cast<long long>(std::floor(position));
        const RealType fraction = position - std::floor(position);
        const auto& filter = interp::InterpFilter::getInstance().getFilter(fraction);
        const auto filter_length = static_cast<long long>(filter.size());
        const auto sample_count = static_cast<long long>(_data.size());
        ComplexType value{0.0, 0.0};
        for (long long tap = 0; tap < filter_length; ++tap)
        {
            const long long sample_index = center + tap - filter_length / 2;
            if (sample_index >= 0 && sample_index < sample_count)
            {
                value += _data[static_cast<std::size_t>(sample_index)] * filter[static_cast<std::size_t>(tap)];
            }
        }
        return value;
    }

References interp::InterpFilter::getFilter(), interp::InterpFilter::getInstance(), max, and position.

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The documentation for this class was generated from the following files:

packages/libfers/src/signal/radar_signal.h
packages/libfers/src/signal/radar_signal.cpp

Public Member Functions

Detailed Description

Constructor & Destructor Documentation

◆ FmcwTriangleSignal() [1/3]

◆ ~FmcwTriangleSignal()

◆ FmcwTriangleSignal() [2/3]

◆ FmcwTriangleSignal() [3/3]

Member Function Documentation

◆ basebandPhaseForTriangleTime()

◆ clear()

◆ getChirpBandwidth()

◆ getChirpDuration()

◆ getChirpRate()

◆ getDeltaPhiUp()

◆ getRate()

◆ getSampleCount()

◆ getStartFrequencyOffset()

◆ getTriangleCount()

◆ getTrianglePeriod()

◆ instantaneousBasebandPhase()

◆ isFmcwFamily()

◆ isTriangle()

◆ load()

◆ operator=() [1/2]

◆ operator=() [2/2]

◆ render()

◆ renderSlice()

◆ sampleAt()