BOSCH CR5CBCC Front Radar Sensor User Manual
- June 6, 2024
- Bosch
Table of Contents
BOSCH CR5CBCC Front Radar Sensor
Description of CR5CBCC parts
Explanation of CW Radar function
Continuous-wave radar is a type of radar system where a known stable frequency
continuouswave radio energy is transmitted and then received from any
reflecting objects. Continuouswave (CW) radar uses Doppler, which renders the
radar immune to interference from large stationary objects and slow moving
clutter.
Maximum distance in a continuous-wave radar is determined by the overall
bandwidth and transmitter power.
This bandwidth is determined by two factors.
- Transmit energy density (watts per Hertz)
- Receiver filter size (bandwidth divided by the total number of filters)
Frequency-modulated continuous-wave radar (FM-CW) – also called continuous- wavefrequency-modulated (CWFM) radar – Pressure compensation element is a short-range measuring radar set capable of determining distance. This increases reliability by providing distance measurement along with speed measurement, which is essential when there is more than one source of reflection arriving at the radar antenna. This kind of radar is often used as “radar altimeter” to measure the exact height during the landing procedure of aircraft. It is also used as early warning radar, wave radar, and proximity sensors. Doppler shift is not always required for detection when FM is used.
In this system the transmitted signal of a known stable frequency continuous
wave varies up and down in frequency over a fixed period of time by a
modulating signal.
Frequency difference between the receive signal and the transmit signal
increases with delay, and hence with distance. This smears out, or blurs, the
Doppler signal. Echoes from a target are then mixed with the transmitted
signal to produce a beat signal which will give the distance of the target
after demodulation.
A variety of modulations is possible, the transmitter frequency can slew up
and down as follows:
- Sine wave, like air raid siren
- Sawtooth wave, like the chirp from a bird
- Triangle wave, like police siren in the United States
- Square wave, like police siren in the United Kingdom
Range demodulation is limited to 1/4 wavelength of the transmit modulation.
Instrumented range for 100 Hz FM would be 500 km. That limit depends upon the
type of modulation and demodulation.
Sawtooth modulation is the most used in FM-CW radars where range is desired
for objects that lack rotating parts. Range information is mixed with the
Doppler velocity using this technique.
Modulation can be turned off on alternate scans to identify velocity using
unmodulated carrier frequency shift. This allows range and velocity to be
found with one radar set. Triangle wave modulation can be used to achieve the
same goal.
As shown in the figure the received waveform (green) is simply a delayed
replica of the transmitted waveform (red). The transmitted frequency is used
to down convert the receive signal to baseband, and the amount of frequency
shift between the transmit signal and the reflected signal increases with time
delay (distance). The time delay is thus a measure of the range; a small
frequency spread is produced by nearby reflections, a larger frequency spread
corresponds with more time delay and a longer range.
Ranging with an FM-CW radar system: if the error caused by a possible Doppler frequency can be ignored and the transmitter’s power is linearly frequency modulated, then the time delay is proportional to the difference of the transmitted and the received signal at any time
References for chapter 2 of this document:
https://en.wikipedia.org/wiki/Continuous-wave_radar
This work is released under CC-BY-SA: http://creativecommons.org/licenses/by-
sa/3.0/
Operation principle of the CR5CBCC
The radar sensor‘s main task is to detect objects and measure their speed and
position relative to the movement of the vehicle in which it is mounted.
To do this, the CR5CBCC senses targets by emitting many short frequency
modulated waves using the transmit antennas while receiving waves reflected by
targets using the receive antennas.
Distance and relative speed are determined via beat frequency (due to
travelling time of the waves) and phase differences between ramps (due to
change of distance in short time). By using the antenna diagram the angles of
departure and arrival of the radar waves can be determined.
Using the Bosch chirp sequence radar modulation, the CR5CBCC allows
unambiguous determination of relative speed in a single measurement cycle.
Therefore, no complex object models are needed for ambiguity resolution.
The radar reflections (strength, distance and relative speed, angular
direction, and derived values) are basis for building a comprehensive model of
the sensed environment.
User information
General description
The CR5CBCC radar sensor and control unit (SCU) contains a FMCW radar
transceiver operating in the globally harmonized frequency range of 76.0 –
77.0 GHz. It senses targets by emitting many short frequency modulated waves
using the transmit antennas while receiving waves reflected by targets using
the receive antennas. Distance and relative speed are determined via beat
frequency (due to travelling time of the waves) and phase differences between
ramps (due to change of distance in short time). By using the antenna diagram,
the angles of departure and arrival of the radar waves can be determined.
Using the Bosch chirp sequence radar modulation, the CR5CBCC allows
unambiguous determination of relative speed in a single measurement cycle.
Therefore, no complex object models are needed for ambiguity resolution. The
radar reflections (strength, distance and relative speed, angular direction,
and derived values) are basis for building a comprehensive model of the sensed
environment.
Fitted in corners of the vehicle, the CR5CBCC monitors continuously vehicle
surroundings, supporting driver and vehicle systems at turning or lane change
manoeuvers. While fitted in rear of vehicle, at higher speeds, the CR5CBCC
operates in long-range mode, monitoring area behind vehicle for small, fast
approaching targets (like motorbikes).
Areas of application
The CR5CBCC is the base for range of safety and driver assistance functions. In particular, the CR5CBCC can be used for the following functions:
Blind spot detection
Optical and/or acoustic warning of the driver if a vehicle is detected in the
Blind Spot Zone in order to avoid unsafe lane change or turn maneuvers of the
driver.
Lane change assist
Optical and/or acoustic warning of the driver if an approaching vehicle is
detected in the neighboring lanes in the area behind the Blind Spot Zone in
order to avoid unsafe lane change or turn maneuvers of the driver.
Rear Cross Traffic Assist with braking
Optical and/or acoustic warning of the driver on vehicles crossing the
estimated path of the ego vehicle in the rear area (e.g. backing out of
parking spaces).
Door opening warning
The door opening warning (DOW) feature shall detect target vehicle in the
door opening warning zones. DOW feature warns the driver and passengers
against collisions that may occur with target vehicle passing the subject
vehicle from behind within a specific lateral distance from subject vehicle’s
relevant side when subject vehicle is at standstill and the door is to be
opened.
It supports the driver and passengers of the subject vehicle when leaving the
vehicle.
Rear collision warning
Warning to the target vehicle if it is approaching the subject vehicle from
behind and there is a chance of collision.
Front Cross Traffic Assist – Information
Optical visualization of the time based criticality of the approaching
vehicle, crossing in front of the vehicle. The front cross traffic assist-
Information function is designed to inform the driver at stand-still or during
drive-off / acceleration phase at intersection scenarios or while leaving a
parking spot.
National statements
Canada
This device complies with Industry Canada license-exempt RSS standard(s).
Operation is subject to the following two conditions:
(1) this device must not cause interference, and
(2) this device must accept any interference, including interference that may
cause undesired operation of the device.
European Union
This equipment should be installed and operated with minimum distance of 20 cm between the radiator and any person.
United Kingdom
This equipment should be installed and operated with minimum distance of 20 cm between the radiator and any person.
United States
This device complies with Part 15 of the FCC Rules.
Operation is subject to the following two conditions:
(1) this device may not cause harmful interference, and
(2) this device must accept any interference received, including interference
that may cause undesired operation.
Changes or modifications made to this equipment not expressly approved by Robert Bosch GmbH may void the FCC authorization to operate this equipment.
This equipment has been tested and found to comply with the limits for a Class A digital device, pursuant to Part 15 of the FCC Rules. These limits are designed to provide reasonable protection against harmful interference when the equipment is operated in a commercial environment. This equipment generates, uses, and can radiate radio frequency energy and, if not installed and used in accordance with the instruction manual, may cause harmful interference to radio communications. Operation of this equipment in a residential area is likely to cause harmful interference in which case the user will be required to correct the interference at his own expense.
Radiofrequency radiation exposure Information:
This equipment complies with FCC radiation exposure limits set forth for an
uncontrolled environment. This equipment should be installed and operated with
minimum distance of 20 cm between the radiator and your body.
This transmitter must not be co-located or operating in conjunction with any
other antenna or transmitter.
Vehicle integration
This chapter describes the requirements for all parts mounted in front or
around the sensor, like painted bumper, unpainted cover and emblem/radome,
regarding RF integration at 77 GHz with CR5CB radar sensors. If these
requirements are not met, the sensor performance can be degraded.
Values are marked with t.b.c. or t.b.d. showing that they have to be confirmed
or defined during the development process.
As product development is an on-going process, we reserve the right to make
amendments in line with technical progress.
The radar sensor performance should be influenced as low as possible by the
installation behind a fascia. Therefore the two-way radar loss by the fascia
should be as low as possible and the reflection attenuation must fulfill the
requirements listed below.
Vertical misalignment will cause additional attenuation reducing the maximum
range.
Horizontal misalignment will cause reduced detection at higher azimuth angles.
Ghost target detection caused by interference signals of multiple reflection
at fascia and metallic parts of the vehicle must be avoided. A simulation can
be offered to evaluate the risk and the need of using absorber material to
suppress this unwanted signal. Because the threshold of detection is very low,
a high attenuation is required. Plastic material can only achieve high enough
attenuation, if carbon black is added.
Radar cone
The radar cone describes the zone where the fascia has to be optimized. Any
parts of the vehicle inside the radar cone may influence the radar
performance. Cables, brackets, bars etc.
should not touch the radar cone. The fascia in this zone may not have bends
and edges as well as changes in thickness or material or painting.
Based on the footprint on the top side of the radar PCB the cone is characterized by a vertical and a horizontal opening angle. The footprint is centered regarding to the sensor housing. A CAD model of the radar cone is available.
The footprint for radar cone has the following dimensions: (W x H) 55 mm x 55
mm
Radar cone definition for covered installation (CR5CB):
The horizontal opening angle depends on the angle range that is evaluated by the sensor in azimuth and elevation, whereby the opening angle of the radar cone has to be larger than the angle range that is evaluated. For covered integration the radar cone is 10° larger than the used angle range that is evaluated by the sensor.
Radar cone:
- ±80° (1) (tbc) in horizontal direction (not including misalignment)
- ±20° (tbc) in vertical direction (not including misalignment)
(1) Valid for angle measurement range of ±75°
Fascia design guidelines
Material
Material with low dielectric constant ( r) and low dielectric loss factor tanδ
at 77 GHz should be used. Recommended are materials based on polypropylene
(PP) and polymethyl methacrylate (PMMA), while materials like polycarbonate
(PC) and acrylonitrile butadiene styrene (ABS) are still ok. The material
shall be homogenous, compounds including glass fiber, carbon fiber or metal
particles are not recommended.
The fascia shall be designed for radar transparency. The thickness shall be a
multiple of the half wavelength (in the material) to minimize the influence of
the fascia. The quality criteria of radar transparency is the reflection
coefficient of the radome/fascia. Tolerances of the overall thickness and the
dielectric constant of the used material influence the amount of reflection at
the radome/fascia. Additional influence occurs due to curvature of the fascia.
Therefore the radius has to be as large as possible. With sharp edges the
negative influence will increase significantly. Not allowed are ribs,
structures and steps changing the thickness of the radome/fascia.
Painting
The layer structure of the painting, typically made of three painting layers
consisting of primer, base coating and clear coating, will increase the
effective permittivity value r,eff and dielectric loss factor tanδ of the
painted plate used as fascia.
Fascia Classification (CR5CB)
The two-way radar loss caused by fascia should be as low as possible. High
losses decrease the sensor performance regarding range and angle estimation.
Therefore it is recommended to achieve a two-way radar loss below 4 dB in the
ranges [-20;+20]° and [+/-60;+/-75]° and 3 dB in
the range [+/-20,+/-60]° t.b.c.. 4 dB attenuation corresponds to a loss of
about 20% of sensor range.
Classification of the fascia
| Fascia type| Material characteristic| Reflection and
attenuation
---|---|---|---
1.| Unpainted bumper| Optimized thickness within a tolerance ±0.2 mm and
permittivity within a tolerance ±0.05. Dielectric loss factor tanδ shall be
<0.03.| – Reflection coefficient <-10 dB
– 2-way attenuation <4 dB.
2.| Painted bumper with various colors| Range of the permittivity values
between 2.5 and 3.2.| Dielectric loss factor tanδ <0.02| – Reflection
coefficient <-6 dB
– 2-way attenuation <4 dB.
Dielectric loss factor tanδ >0.02| – Reflection coefficient >-6 dB
– The attenuation may exceed the maximum allowed limit.
The examples described in the classification of the fascia are derived from
evaluation of flat plates with constant thickness and homogeneous material.
Deviations from this situation may cause a change in classification.
Surface Properties of the fascia
The surfaces of the fascia shall not exceed an average roughness height of 20 µm (corresponding to ISO 1302 class N10; VDI 3400 class 45).
Installation Hints
To enable the full performance of the radar sensor, the following installation hints and guidelines for the RF integration of the sensor must be used.
Maximum angle between radar cone and fascia
The angle α between the radar beam inside the radar cone and the fascia may
not be larger than 80° anywhere inside the radar cone
Distance between sensor and fascia
The minimum distance between the sensor radome and the fascia or any other
part of the vehicle may not be smaller than 3 mm.
This is valid for fascia parts fulfilling the following requirements.
The distance between the sensor radome and the fascia should be however as close as possible to the minimum value in order to reduce the risk of multipath reflection and consequently to prevent ghost targets.
Vertical tilt of fascia (CR5CB)
The vertical tilt angle between the sensor normal and the surface normal of
the fascia shall be in the range according to the following table.
Vertical tilt angle t.b.c:
Vertical tilt| Reflection coefficien t| Max. tolerance
thickness| Permittivity εr| Tolerance Permittivity εr|
tanδ| Type of fascia
---|---|---|---|---|---|---
2°| <-14 dB| ±0.1 mm| single value| ±0.05| <0.03| unpainted (black) bumper
6°| <-10 dB| ±0.2 mm| single value| ±0.05| <0.03| unpainted (black) bumper
<-6 dB| –| range from 2.5 to 3.2| ±0.05| <0.02| painted bumper
8°| >-6 dB| –| range from 2.5 to 3.2| ±0.05| >0.02| painted bumper
Table: minimum vertical tilt angle of fascia to sensor normal
The values provided in the previous table are derived from evaluation of flat plates with constant thickness and homogeneous material. Deviations from this situation may cause a change in classification and the vertical tilt angle of fascia has to be increased.
Curvature of fascia for CR5CB
Curvature of the fascia may influence the radar performance, especially with
low vertical tilt angles. The minimum radius of the curvature shall be
according to the following rules:
R > 300 mm, no significant influence expected
R < 300 mm, significant influence possible, not recommended
Absorber around the sensor
It is highly recommended to use a cone made of absorber material around the
radar cone of the sensor to prevent ghost targets. The design of the absorber
cone must fulfill the following design guidelines (reflection from outside the
radar cone, multipath reflection).
Reflection from outside the radar cone
Reflections from structures located outside the radar cone have to be avoided.
Furthermore interference signals picked up by the sensor antennas should be
avoided by keeping a minimum distance (d) of 5 mm to 10 mm for parts in front
of the sensor.
Even with compliance to the radar cone, reflections at parts outside the radar
cone may disturb the received signal. Reflections at parts causing an
interference signal to the receiving antenna and reflections at parts getting
to the receiving antenna after a second reflection at the fascia (multipath
reflection).
Closed surfaces of brackets and masks made of metal or high reflecting
material need a tilt angle being arranged that the reflection is not received
by the receiving antennas of the sensor.
For closed surfaces (masks) in azimuth, the angle between mask surface and
the normal vector n of the sensor shall be greater than the azimuth opening
angle of the keep-out zone.
For closed surfaces (masks) in elevation, the angle between mask surface and
the normal vector n of the sensor shall be greater than the azimuth opening
angle of the keep-out zone.
Multipath reflection
Reflections of incoming signals at bracket or shielding absorber are coming back to the sensor if reflection at the bumper occurs. The figure below shows the situation which should be avoided. The worst case happens if the combination of the vertical tilt angles of shielding and bumper is 1 = 2 / 2 . For a low interference signal the condition shall be:
1 > 2 / 2 +10°
or
1 < 2 / 2 -10°
The same requirements are valid for a horizontal tilt of the fascia.
Calibration
No manual alignment procedure is necessary, as the sensor performs it’s own internal SW calibration.
Technical Data
Product model name: | CR5CBCC |
---|---|
Frequency Band: | 76-77 GHz |
Maximum Transmit Power:
Nominal mean EIRP| 18,58 dBm
Maximum Transmit Power:
Measured mean EIRP| 17,96 dBm
Maximum Transmit Power:
Measured peak EIRP| 26,97 dBm
XC-DA/ECR3-Bp
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