Glossary#
- Direct leakage#
Direct leakage refers to the transmission of the radar signal directly from the transmitter to the receiver without reflecting off a target. The length of the direct leakage varies with the transmitted pulse length. The transmitted pulse length is set using Profiles.
- PCR#
Pulsed Coherent Radar.
- PRF#
Pulse repetition frequency. The frequency at which the radar transmits wavelets.
- Profile#
Profiles are used to set the transmitted pulse length in discreet steps. The higher the Profile, the longer the transmitted pulse length.
- SNR#
Abbreviation of Signal-to-noise ratio. General ratios quantify how much more there is of one thing (Signal in this case), compared to the other thing (noise). Generally, a high SNR means high signal quality. SNR can be defined as
(31)#\[SNR=C \sigma \gamma \frac{1}{R^{4}}\]Where \(R\) is the distance of the radar to the target, \(C\) is the radar loop gain, including both the transmitter and receiver chain (two-ways signal path), \(\sigma\) is the Radar Cross Section (RCS) of the scattering object and \(\gamma\) determines the reflected power of the object’s material. RCS depends on the size and shape of the scattering object.
- Reflectivity#
A property of physical materials. If a material is more reflective, more power finds its way back to the sensor and vice versa. See \(\gamma\) in Eq. 31.
- Radar Cross Section#
Depends on the shape of the Object measured. Affects how much power returns to the sensor.
- Object#
The physical thing a sensor should measure.
- Detector#
A reusable, well tested, package-offering that consists of an API for Sensor Control, higher-level output (like distance to objects) all backed by signal processing algorithms.
Detectors are used to enable many use cases. They are diligently used in our Reference Applications.
- Sensor Control#
Describes controlling the sensor on a low level or the sequence of sensor verbs (
prepare,measure,process,power_on, etc.) in the context of Detectors, Reference Applications or Example Applications.- Reference Application#
A nearly complete use case specific package-offering. Unlike Detectors, these packages are targeting more specific use cases, such as Tank Level or Parking.
- Example Application#
A use case specific proof-of-concept signal processing algorithm that haven’t undergone significant testing, but works quite well in the scenarios tested.
- Exploration Tool#
Acconeer’s graphical sensor evaluation application. All Detectors, Reference Applications and Example Applications are showcased here and new ones are added continuously.
- Far-field#
The far-field distance can be determined by the aperture of the sensor and the radar target.
(32)#\[R_{farfield}>\frac{2A^{2}}{\lambda_{0}}\]where \(A\) is the largest dimension of either the sensor or the radar target, and \(\lambda_{0}\) is the wavelength in free-space. The far-field region is where the radiation pattern shape does not change with the distance. However, the radar works below the far-field distance with different characteristics than the far-field region with radiation pattern dependency on the distance.
- RLG#
Radar Loop Gain, the transmitter and receiver gain of the radar, combined.
- Dielectric#
A dielectric is an insulating, non-conducting material that can be polarized by an electric field. It is often used as a structural component or as a medium for controlling electromagnetic wave propagation. Some common examples include air, wood, and various polymers and plastics.
- Reflection#
Reflection is the portion of an electromagnetic wave that is returned or “bounced back” when it encounters a boundary between two materials with different dielectric properties. In radomes, reflection causes a fraction of the radar signal to be lost or redirected, depending on the difference in dielectric constants between air and the radome material.
- Transmission#
Transmission is the portion of an electromagnetic wave that passes through a material. For radomes, good transmission means most of the radar signal passes through the material without significant loss or distortion.
- Refraction#
Refraction is the bending or change in direction of an electromagnetic wave as it passes from one material into another with a different dielectric constant. In radomes, refraction slightly alters the wave’s path but is usually minimal if the material is thin and uniform.
- Diffraction#
Diffraction is the bending and spreading of electromagnetic waves as they pass through apertures or around obstacles. In dielectric Fresnel zone plate lenses, diffraction is the primary mechanism that shapes the wavefront and focuses energy along the designed propagation path.
- Permittivity#
Permittivity is a material property that describes how an electric field interacts with a medium. It determines how much the electromagnetic wave slows down and how the material stores electric energy. The relative permittivity, often called the dielectric constant, compares the material’s permittivity to that of free space and is the key parameter for radar-transparent materials like radomes and lenses.
- Linear polarization#
Linear polarization describes an electromagnetic wave in which the electric field oscillates in a single plane along the direction of propagation. Most radome and lens analyses assume linear polarization to simplify reflection and transmission calculations.
- Normal incidence#
Normal incidence occurs when an electromagnetic wave strikes a surface or interface at a 90° angle, meaning the wavefront is perpendicular to the surface. Reflection and transmission at normal incidence are simplified compared to oblique angles.
- LOS#
Line-of-sight. A straight line between the radar and a target without obstructions.