Radar Channels¶
Hermes’ radar channels can be used to simulate basic propagation characteristics of sensing signals. They can be thought of as stripped down raytracing channels which consider only a single reflection in between the transmitting and receiving device, with the reflection being generated by target objects specified by the user.
There are currently two types of Radar Channels
,
namely the easy-to-use SingleTargetRadarChannel
,
considering only a single reflector between its two linked devices,
and the more complex MultiTargetRadarChannel
,
which allows for the specification of multiple reflectors with individual Cross Sections
,
that may represent Virtual Targets
or existing Physical Targets
.
A radar channel linking two devices indexed by \(\alpha\) and \(\beta\) and located at cartesian coordinates \(\mathbf{p}_{\mathrm{Device}}^{(\alpha)}\) and \(\mathbf{p}_{\mathrm{Device}}^{(\beta)}\) while moving with a global velocity of \(\mathbf{v}_{\mathrm{Device}}^{(\alpha)}\) and \(\mathbf{v}_{\mathrm{Device}}^{(\beta)}\) respectively, is modeled by the impulse response
considering a line-of-sight (LOS) interference component between both devices and a sum of \(L\) first-order reflection components generated by the \(L\) targets. The LOS component
depends on the distance and resulting time-of-flight delay between the devices
as well as the relative velocity between the devices
Note that if a mono-static radar configuration is considered, i.e. \(\alpha = \beta\), the LOS component is not considered, since it is equivalent to Leakage between transmit and receive chains. The reflection components generated by the \(L\) targets are modeled by
where the distance and resulting time-of-flight delay between the device and the \(\ell\)-th target are given by
The doppler shift perceived by the receiving device depends on the velocities on both devices and the target, which results in an overall relative velocity of
- class RadarChannelBase(attenuate=True, *args, **kwargs)[source]¶
Bases:
Generic
[RCRT
],Channel
[RCRT
,RadarChannelSample
]Base class of all radar channel implementations.
- Parameters:
attenuate (bool, optional) – Radar channel attenuation flag, see also
RadarChannelBase.attenuate()
. Enabled by default.
- class RadarChannelRealization(sample_hooks, gain)[source]¶
Bases:
ChannelRealization
[RadarChannelSample
]Realization of a radar channel.
_summary_
- Parameters:
sample_hooks (Set[ChannelSampleHook[CST]], optional) – Hooks to be called after the channel is sampled.
gain (float) – Linear power gain factor a signal experiences when being propagated over this realization.
- class RCRT¶
Type of radar channel realization.
alias of TypeVar(‘RCRT’, bound=
RadarChannelRealization
)
- class RadarChannelSample(paths, gain, state)[source]¶
Bases:
ChannelSample
Realization of a radar channel.
Generated by
RadarChannelBase.realize()
andRadarChannelBase.realize_interference()
.- Parameters:
- null_hypothesis()[source]¶
Generate a null hypothesis channel sample rom a given channel sample.
Null hypothesis sample will remove non-static propagation components from the channel model. This function is, for example, accessed to evaluate a radar link’s receiver operating characteristics.
Returns: The null hypothesis radar channel realization.
- Return type:
- state(num_samples, max_num_taps, interpolation_mode=InterpolationMode.NEAREST)[source]¶
Generate the discrete channel state information from this channel realization.
Denoted by
\[\mathbf{H}^{(m, \tau)} \in \mathbb{C}^{N_{\mathrm{Rx}} \times N_{\mathrm{Tx}}}\]within the respective equations.
- Parameters:
num_samples (int) – Number of discrete time-domain samples of the chanel state information.
max_num_taps (int) – Maximum number of delay taps considered per discrete time-domain sample.
interpolation_mode (InterpolationMode, optional) – Interpolation behaviour of the channel realization’s delay components with respect to the proagated signal’s sampling rate. If not specified, an integer rounding to the nearest sampling instance will be assumed.
- Return type:
Returns: The channel state information representing this channel realization.
- class RCST¶
Type of radar channel sample.
alias of TypeVar(‘RCST’, bound=
RadarChannelSample
)
- class RadarPath(attenuate=True, static=False)[source]¶
Bases:
HDFSerializable
Realization of a radar propagation path between transmitter and receiver
- Parameters:
- add_propagation(transmitter_state, receiver_state, signal, bandwidth, carrier_frequency, propagated_samples, propagation_delay=None, relative_velocity=None)[source]¶
Add propagation of a signal over this path realization to a given sample buffer.
- Parameters:
transmitter (DeviceState) – Transmitting device.
receiver (DeviceState) – Receiving device.
signal (np.ndarray) – Signal samples to be propagated.
bandwidth (float) – Sampling rate of the the propagated signal model in Hz.
carrier_frequency (float) – Central carrier frequency of the propagated signal in Hz.
propagated_samples (np.ndarray) – Sample buffer to be written to.
propagation_delay (float, optional) – Propagation delay of the wave from transmitter over target to receiver. If not specified, the delay will be queried from
propagation_delay()
.relative_velocity (float, optional) – Relative velocity between transmitter and receiver. If not specified, the velocity will be queried from
relative_velocity()
.
- Return type:
- add_state(transmitter, receiver, bandwidth, carrier_frequency, delay, state)[source]¶
Add propagation of a signal over this path realization to a given channel state information sample buffer.
- Parameters:
transmitter (DeviceState) – Transmitting device.
receiver (DeviceState) – Receiving device.
bandwidth (float) – Sampling rate of the the propagated signal model in Hz.
carrier_frequency (float) – Central carrier frequency of the propagated signal in Hz.
delay (float) – Delay of the channel state information in seconds.
state (np.ndarray) – Sample buffer to be written to.
- Return type:
- abstract propagation_delay(transmitter, receiver)[source]¶
Propagation delay of the wave from transmitter over target to receiver.
Denoted by \(\tau_{\ast}\) within the respective equations.
- Parameters:
transmitter (DeviceState) – Transmitting device.
receiver (Device) – Receiving device.
- Return type:
Returns: Propagation delay in seconds.
- abstract propagation_response(transmitter, receiver, carrier_frequency)[source]¶
Multipath sensor array response matrix from transmitter to receiver.
Includes polarization losses.
- Parameters:
transmitter (DeviceState) – Transmitting device.
receiver (DeviceState) – Receiving device.
carrier_frequency (float) – Carrier frequency of the propagated signal in Hz. Denoted by \(f_{\mathrm{c}}^{(\alpha)}\) within the respective equations.
- Return type:
Returns: Numpy matrix of antenna response weights.
- abstract relative_velocity(transmitter, receiver)[source]¶
Relative velocity between transmitter and receiver.
Denoted by \(v_{\ast}\) within the respective equations.
- Parameters:
transmitter (DeviceState) – Transmitting device.
receiver (DeviceState) – Receiving device.
- Return type:
Returns: Relative velocity in m/s.
- class RadarTargetPath(position, velocity, cross_section, reflection_phase, attenuate=True, static=False)[source]¶
Bases:
RadarPath
Realization of a radar propagation path resulting from a target scattering
- Parameters:
position (np.ndarray) – Global position of the path’s target.
velocity (np.ndarray) – Global velocity of the path’s target.
cross_section (float) – Radar cross section of the path’s target in \(\mathrm{m}^2\).
reflection_phase (float) – Reflection phase of the path’s target in radians.
attenuate (bool, optional) – Should the propagated signal be attenuated during propagation modeling? Enabled by default.
static (bool, optional) – Is the path considered static? Static paths will remain during null hypothesis testing. Disabled by default.
- propagation_delay(transmitter, receiver)[source]¶
Propagation delay of the wave from transmitter over target to receiver.
Denoted by \(\tau_{\ast}\) within the respective equations.
- Parameters:
transmitter (DeviceState) – Transmitting device.
receiver (Device) – Receiving device.
- Return type:
Returns: Propagation delay in seconds.
- propagation_response(transmitter, receiver, carrier_frequency)[source]¶
Multipath sensor array response matrix from transmitter to receiver.
Includes polarization losses.
- Parameters:
transmitter (DeviceState) – Transmitting device.
receiver (DeviceState) – Receiving device.
carrier_frequency (float) – Carrier frequency of the propagated signal in Hz. Denoted by \(f_{\mathrm{c}}^{(\alpha)}\) within the respective equations.
- Return type:
Returns: Numpy matrix of antenna response weights.
- relative_velocity(transmitter, receiver)[source]¶
Relative velocity between transmitter and receiver.
Denoted by \(v_{\ast}\) within the respective equations.
- Parameters:
transmitter (DeviceState) – Transmitting device.
receiver (DeviceState) – Receiving device.
- Return type:
Returns: Relative velocity in m/s.
- property cross_section: float¶
Radar cross section of the path’s target in \(\mathrm{m}^2\).
Denoted by \(\sigma_{\ell}\) within the respective equations.
- property ground_truth: Tuple[ndarray, ndarray]¶
Consolidate the true target information represented by this path.
Either a tuple of the target’s position and velocity or None if the path represents only interference / clutter.
- property position: ndarray¶
Global position of the path’s target.
Denoted by \(\mathbf{p}^{(\ell)}\) within the respective equations.
- class RadarInterferencePath(attenuate=True, static=False)[source]¶
Bases:
RadarPath
Realization of a line of sight interference propgation path between a radar transmitter and receiver
- Parameters:
- propagation_delay(transmitter, receiver)[source]¶
Propagation delay of the wave from transmitter over target to receiver.
Denoted by \(\tau_{\ast}\) within the respective equations.
- Parameters:
transmitter (DeviceState) – Transmitting device.
receiver (Device) – Receiving device.
- Return type:
Returns: Propagation delay in seconds.
- propagation_response(transmitter, receiver, carrier_frequency)[source]¶
Multipath sensor array response matrix from transmitter to receiver.
Includes polarization losses.
- Parameters:
transmitter (DeviceState) – Transmitting device.
receiver (DeviceState) – Receiving device.
carrier_frequency (float) – Carrier frequency of the propagated signal in Hz. Denoted by \(f_{\mathrm{c}}^{(\alpha)}\) within the respective equations.
- Return type:
Returns: Numpy matrix of antenna response weights.
- relative_velocity(transmitter, receiver)[source]¶
Relative velocity between transmitter and receiver.
Denoted by \(v_{\ast}\) within the respective equations.
- Parameters:
transmitter (DeviceState) – Transmitting device.
receiver (DeviceState) – Receiving device.
- Return type:
Returns: Relative velocity in m/s.