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feat: add high-fidelity radar antenna model (draft) #914

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3 changes: 3 additions & 0 deletions doc/architecture/proto-files.adoc
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Expand Up @@ -6,6 +6,9 @@ endif::[]

TODO: Add general description.

osi_antenna.proto::
High-fidelity, polarimetric antenna model of radar sensors (Jones matrix patterns per antenna element, array geometry).

osi_common.proto::
TODO: Add description.

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284 changes: 284 additions & 0 deletions osi_antenna.proto
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syntax = "proto2";

option optimize_for = SPEED;

import "osi_common.proto";

package osi3;

//
// \brief High-fidelity antenna model of a radar front end.
//
// DRAFT PROPOSAL (osi-hfss). This message extends the scalar
// \c RadarSensorViewConfiguration::AntennaDiagramEntry description with a
// complex, polarimetric (Jones matrix based) far-field description per
// antenna element, plus the element geometry of the array.
//
// The model consists of
// - \c AntennaElementType : the radiation behaviour shared by many elements
// (e.g. all patches of a receive array have the same pattern), and
// - \c AntennaElement : a placed instance of an element type with an index
// (channel number), a position and an orientation.
//
// With this information a sensor model can compute the complex response of
// every Tx / Rx channel for any departure / arrival direction, which is the
// prerequisite for MIMO, beamforming, direction-of-arrival estimation and
// polarimetric simulation.
//
// \note The legacy \c tx_antenna_diagram / \c rx_antenna_diagram of
// \c RadarSensorViewConfiguration can be derived from this model as the
// co-polarised magnitude in dB and should be filled for consumers that do
// not support \c AntennaModel.
//
message AntennaModel
{
// Identifier of the antenna model.
//
optional Identifier id = 1;

// Polarisation basis in which all \c JonesPattern of this model and the
// \c RadarSensorView::Reflection::polarimetric_response are expressed.
//
optional PolarizationBasis polarization_basis = 2;

// Element types referenced by \c element.
//
repeated AntennaElementType element_type = 3;

// Placed antenna elements (Tx and Rx channels).
//
repeated AntennaElement element = 4;

// Polarisation basis.
//
enum PolarizationBasis
{
// Unknown (must not be used in ground truth).
//
POLARIZATION_BASIS_UNKNOWN = 0;

// Other (unspecified but known).
//
POLARIZATION_BASIS_OTHER = 1;

// Linear basis, index 0 = horizontal (H), index 1 = vertical (V).
//
POLARIZATION_BASIS_LINEAR_HV = 2;

// Circular basis, index 0 = left hand (L), index 1 = right hand (R).
//
POLARIZATION_BASIS_CIRCULAR_LR = 3;
}
}

//
// \brief Radiation behaviour shared by one or more antenna elements.
//
message AntennaElementType
{
// Identifier of the element type, referenced by
// \c AntennaElement::element_type_id.
//
optional Identifier id = 1;

// Whether the element transmits or receives.
//
optional Mode mode = 2;

// Characterisation of the element at discrete frequencies.
//
// Sensor models interpolate between entries if needed.
//
repeated FrequencyInstance frequency_instance = 3;

// Operating mode of an element.
//
enum Mode
{
// Unknown (must not be used in ground truth).
//
MODE_UNKNOWN = 0;

// Other (unspecified but known).
//
MODE_OTHER = 1;

// Receiving element.
//
MODE_RECEIVE = 2;

// Transmitting element.
//
MODE_TRANSMIT = 3;
}
}

//
// \brief Antenna behaviour at one frequency.
//
message FrequencyInstance
{
// Frequency.
//
// Unit: Hz
//
// \rules
// is_greater_than: 0
// \endrules
//
optional double frequency = 1;

// Absolute gain applied to all radiation patterns.
//
// The gain is given for the field amplitude, i.e. 20*log10 of the
// linear amplitude factor.
//
// Unit: dB
//
optional double gain = 2;

// Absolute phase offset applied to all radiation patterns.
//
// Unit: rad
//
optional double phase = 3;

// Axial ratio of the principal polarisation.
//
// Unit: dB
//
optional double axial_ratio = 4;

// Normalised complex far-field radiation pattern.
//
optional JonesPattern radiation = 5;
}

//
// \brief Complex polarimetric far-field pattern on a regular angular grid.
//
// For a direction (h, v) the 2x2 Jones matrix J maps an excitation vector
// e = (e_0, e_1) in the polarisation basis of \c AntennaModel to the
// radiated field E = J * e:
//
// \f$ E_0 = J_{00} e_0 + J_{10} e_1 \f$
// \f$ E_1 = J_{01} e_0 + J_{11} e_1 \f$
//
// All \c ComplexGrid values are stored row-major with
// index = i_horizontal * size(vertical_angle) + i_vertical.
//
// \note Angles are defined analog to \c Spherical3d in antenna coordinates:
// horizontal (azimuth) 0 and vertical (elevation) 0 is boresight.
//
message JonesPattern
{
// Horizontal (azimuth) grid angles, strictly increasing.
//
// Unit: rad
//
repeated double horizontal_angle = 1 [packed = true];

// Vertical (elevation) grid angles, strictly increasing.
//
// Unit: rad
//
repeated double vertical_angle = 2 [packed = true];

// Co-polar pattern of basis component 0 (HH in linear basis).
//
optional ComplexGrid pattern_00 = 3;

// Co-polar pattern of basis component 1 (VV in linear basis).
//
optional ComplexGrid pattern_11 = 4;

// Cross-polar pattern 0 -> 1 (HV in linear basis).
//
optional ComplexGrid pattern_01 = 5;

// Cross-polar pattern 1 -> 0 (VH in linear basis).
//
optional ComplexGrid pattern_10 = 6;
}

//
// \brief Complex values on a \c JonesPattern grid in polar form.
//
message ComplexGrid
{
// Linear amplitude.
//
repeated double amplitude = 1 [packed = true];

// Phase.
//
// Unit: rad
//
repeated double phase = 2 [packed = true];
}

//
// \brief A placed antenna element (one Tx or Rx channel).
//
message AntennaElement
{
// Channel index of the element, unique per mode within the model.
//
optional uint32 index = 1;

// Identifier of the referenced \c AntennaElementType.
//
optional Identifier element_type_id = 2;

// Phase centre position of the element in the sensor coordinate system.
//
// Unit: m
//
optional Vector3d position = 3;

// Orientation of the element antenna coordinate system relative to the
// sensor coordinate system.
//
optional Orientation3d orientation = 4;
}

//
// \brief Complex value in polar form.
//
message ComplexValue
{
// Linear amplitude.
//
optional double amplitude = 1;

// Phase.
//
// Unit: rad
//
optional double phase = 2;
}

//
// \brief Complex 2x2 matrix, e.g. a polarimetric scattering matrix.
//
// Element m_rt maps transmitted basis component t to received basis
// component r.
//
message JonesMatrix
{
// Element (0, 0).
//
optional ComplexValue m00 = 1;

// Element (0, 1).
//
optional ComplexValue m01 = 2;

// Element (1, 0).
//
optional ComplexValue m10 = 3;

// Element (1, 1).
//
optional ComplexValue m11 = 4;
}
30 changes: 30 additions & 0 deletions osi_sensorview.proto
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Expand Up @@ -7,6 +7,7 @@ import "osi_common.proto";
import "osi_groundtruth.proto";
import "osi_sensorviewconfiguration.proto";
import "osi_hostvehicledata.proto";
import "osi_antenna.proto";

package osi3;

Expand Down Expand Up @@ -245,6 +246,35 @@ message RadarSensorView
// Unit: rad
//
optional double source_vertical_angle = 5;

// RX horizontal angle (azimuth) of arrival (DRAFT PROPOSAL, osi-hfss).
//
// Horizontal angle under which the reflection arrives at the RX
// antenna. Differs from \c source_horizontal_angle for bistatic
// configurations and multi-bounce paths.
//
// Unit: rad
//
optional double arrival_horizontal_angle = 6;

// RX vertical angle (elevation) of arrival (DRAFT PROPOSAL, osi-hfss).
//
// Unit: rad
//
optional double arrival_vertical_angle = 7;

// Antenna-free polarimetric propagation channel of the reflection
// (DRAFT PROPOSAL, osi-hfss).
//
// Complex 2x2 scattering matrix including path loss and scattering,
// but excluding any antenna characteristics, expressed in the
// \c AntennaModel::polarization_basis. The propagation phase due to
// \c time_of_flight is not included. Only filled if
// \c RadarSensorViewConfiguration::antenna_application is
// \c ANTENNA_APPLICATION_SENSOR_MODEL; \c signal_strength then
// excludes the antenna diagrams as well.
//
optional JonesMatrix polarimetric_response = 8;
}
}

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37 changes: 37 additions & 0 deletions osi_sensorviewconfiguration.proto
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Expand Up @@ -4,6 +4,7 @@ option optimize_for = SPEED;

import "osi_common.proto";
import "osi_version.proto";
import "osi_antenna.proto";

package osi3;

Expand Down Expand Up @@ -435,6 +436,42 @@ message RadarSensorViewConfiguration
//
repeated AntennaDiagramEntry rx_antenna_diagram = 11;

// High-fidelity antenna model (DRAFT PROPOSAL, osi-hfss).
//
// Complex, polarimetric description of all Tx and Rx elements including
// the array geometry. If set, \c tx_antenna_diagram and
// \c rx_antenna_diagram should still be filled as the co-polarised
// magnitude derived from this model for backward compatibility.
//
optional AntennaModel antenna_model = 12;

// Defines which party applies the antenna characteristics
// (DRAFT PROPOSAL, osi-hfss).
//
optional AntennaApplication antenna_application = 13;

// Party responsible for applying the antenna characteristics.
//
enum AntennaApplication
{
// Unknown, treated as \c ANTENNA_APPLICATION_ENVIRONMENT.
//
ANTENNA_APPLICATION_UNKNOWN = 0;

// Legacy behaviour: the environment simulation applies
// \c tx_antenna_diagram and \c rx_antenna_diagram and folds them
// into \c RadarSensorView::Reflection::signal_strength.
//
ANTENNA_APPLICATION_ENVIRONMENT = 1;

// The environment simulation delivers the antenna-free
// propagation channel per reflection
// (\c RadarSensorView::Reflection::polarimetric_response, departure
// and arrival angles). The sensor model applies \c antenna_model.
//
ANTENNA_APPLICATION_SENSOR_MODEL = 2;
}

//
// \brief The radar antenna diagram.
//
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