U.S. patent application number 14/634083 was filed with the patent office on 2015-06-18 for fmcw radar system and interference recognition method for fmcw radar systems.
The applicant listed for this patent is Robert Bosch GmbH. Invention is credited to Stefan HEILMANN, Juergen HILDEBRANDT, Armin HIMMELSTOSS.
Application Number | 20150168539 14/634083 |
Document ID | / |
Family ID | 46197033 |
Filed Date | 2015-06-18 |
United States Patent
Application |
20150168539 |
Kind Code |
A1 |
HIMMELSTOSS; Armin ; et
al. |
June 18, 2015 |
FMCW RADAR SYSTEM AND INTERFERENCE RECOGNITION METHOD FOR FMCW
RADAR SYSTEMS
Abstract
An FMCW radar system is provided having a transceiver unit which
is designed to transmit radar signals, which are modulated with the
aid of at least one modulation parameter, and to receive radar
signals, which are reflected from objects, and having an
interference detector for detecting interferences in the received
radar signals based on at least one frequency-dependent reception
power threshold value corresponding to the particular modulation
parameters, one of the modulation parameters being a modulation
slope of the transmitted radar signal. An interference recognition
method is also provided.
Inventors: |
HIMMELSTOSS; Armin;
(Weissach Im Tal, DE) ; HILDEBRANDT; Juergen;
(Weilheim, DE) ; HEILMANN; Stefan; (Vaihingen/Enz,
DE) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Robert Bosch GmbH |
Stuttgart |
|
DE |
|
|
Family ID: |
46197033 |
Appl. No.: |
14/634083 |
Filed: |
February 27, 2015 |
Related U.S. Patent Documents
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
|
|
13554045 |
Jul 20, 2012 |
|
|
|
14634083 |
|
|
|
|
Current U.S.
Class: |
342/159 |
Current CPC
Class: |
G01S 13/931 20130101;
G01S 13/34 20130101; G01S 7/023 20130101 |
International
Class: |
G01S 7/02 20060101
G01S007/02; G01S 13/34 20060101 G01S013/34 |
Foreign Application Data
Date |
Code |
Application Number |
Jul 22, 2011 |
DE |
10 2011 079 615.0 |
Claims
1-12. (canceled)
13. An FMCW radar system, comprising: a transceiver unit configured
to transmit radar signals which are modulated according to at least
one modulation parameter, and to receive radar signals which are
reflected from objects; and an interference detector configured to
detect interferences in the received radar signals based on a
comparison of reception power of the received radar signals to at
least one frequency-dependent reception power threshold value,
wherein the at least one frequency-dependent reception power
threshold value is set based on at least one of a transmission
power of the transceiver unit, an antenna output of the transceiver
unit, a maximally occurring radar backscatter cross section of
expected objects, a speed at which the FMCW radar system moves, and
data of previously detected objects.
14. The FMCW radar system as recited in claim 13, wherein the
reception power threshold value is set based on at least one of the
transmission power of the transceiver unit, and the antenna output
of the transceiver unit.
15. An interference recognition method for a FMCW radar system,
comprising: providing an FMCW radar system, the system including a
transceiver unit configured to transmit radar signals which are
modulated according to at least one modulation parameter, and to
receive radar signals which are reflected from objects, and an
interference detector configured to detect interferences in the
received radar signals based on a comparison of reception power of
the received radar signals to at least one frequency-dependent
reception power threshold value; transmitting, by the transceiver
unit, the radar signals which are modulated with the aid of at
least one modulation parameter; receiving, by the transceiver unit,
the radar signals which are reflected from objects; and detecting,
by the interference detector, interferences in the received radar
signals based on a comparison of reception power of the received
radar signals to the at least one frequency-dependent reception
power threshold value, wherein the at least one frequency-dependent
reception power threshold value is set based on at least one of a
transmission power of the transceiver unit, an antenna output of
the transceiver unit, a maximally occurring radar backscatter cross
section of expected objects, a speed at which the FMCW radar system
moves, and data of objects detected previously by the FMCW radar
system.
16. The interference recognition method as recited in claim 15,
wherein the reception power threshold value is set based on at
least one of the transmission power of the transceiver unit and the
antenna output of the transceiver unit.
Description
CROSS REFERENCE
[0001] The present application claims the benefit under 35 U.S.C.
.sctn.119 of German Patent Application No. DE 102011079615.0 filed
on Jul. 22, 2011, which is expressly incorporated herein by
reference in its entirety.
FIELD OF THE INVENTION
[0002] The present invention relates to radar systems in general.
In particular, the present invention relates to FMCW radar systems
and interference recognition methods for FMCW radar systems.
BACKGROUND INFORMATION
[0003] FMCW radar systems are presently used in a plurality of
applications. For example, FMCW radar systems, in particular, may
be used in motor vehicles. FMCW radar systems in motor vehicles
are, for example, used to detect objects which are located in the
surroundings of the motor vehicle. The data received by the FMCW
radar systems regarding objects which are located around the
vehicle may then be used, for example, for automatic cruise control
of a motor vehicle.
[0004] FMCW radar systems make it possible to determine a speed and
a distance of an object relative to the FMCW radar system. For this
purpose, multiple modulations are transmitted by the radar and the
reflected radar signals are evaluated. A series of transmitted
modulations (radar signals) is referred to as a sequence. Here, the
individual modulations are each characterized by different
modulation parameters, in particular by a modulation slope of the
transmission frequency. For example, a modulation may have a
modulation slope of 400 MHz/ms.
[0005] For object recognition, usually a plurality of modulations
of radar signals is transmitted. The modulations may have identical
or different modulation parameters.
[0006] Since radar systems are in general based on transmitting
electromagnetic waves and detecting and evaluating the reflections
of these transmitted electromagnetic waves from objects, radar
systems are susceptible to interferences of other radar systems.
Interferences are mutual disruptions of radar systems.
Interferences may, for example, delimit the sensitivity of a radar
sensor or have an influence on its detection range. Furthermore, an
interference may result in an erroneous recognition or
non-recognition of objects.
[0007] In modern radar systems, methods for detecting interferences
are thus used.
[0008] U.S. Published Patent Application No. US 2007/0018886 A1
describes an interference recognition method in which interferences
are detected based on a rate of change of the amplitude of the
received radar signal.
[0009] Furthermore, Japanese Patent Application No. JP 2002 168947
(A) describes a method for interference recognition in which a
threshold value is established for the output signal of a mixer of
a receiver unit. If the level of the output signal exceeds the
threshold value, an interference is assumed. The threshold value is
determined as a function of a relative speed or a distance between
the radar system and a detected object.
SUMMARY
[0010] The present invention relates to an FMCW radar system and an
interference recognition method for FMCW radar systems.
[0011] An example FMCW radar system is provided having a
transceiver unit which is designed to transmit radar signals, which
are modulated with the aid of at least one modulation parameter,
and to receive radar signals, which are reflected from objects, and
having an interference detector for detecting interferences in the
received radar signals based on at least one frequency-dependent
reception power threshold value corresponding to the particular
modulation parameters, one of the modulation parameters being a
modulation slope of the transmitted radar signal.
[0012] An example interference recognition method for FMCW radar
systems is provided having the steps of providing an FMCW radar
system according to the present invention; transmitting radar
signals which are modulated with the aid of at least one modulation
parameter; receiving radar signals which are reflected from
objects; detecting interferences in the received radar signals
based on at least one frequency-dependent reception power threshold
value corresponding to the particular modulation parameters, one of
the modulation parameters being a modulation slope of the
transmitted radar signal.
[0013] In accordance with the present invention, a reception power
of radar signals usually does not exceed certain maximum values for
actual existing objects.
[0014] According to the present invention, an interference
recognition is carried out based on the threshold values for the
reception power of radar signals, the reception power threshold
values being determined with the aid of at least one modulation
slope of the transmitted radar signal. For this purpose, a
signature or a set of frequency-dependent reception power threshold
values, which indicate a reception power threshold value for each
of the frequencies occurring in the particular modulation, is
determined for any given modulation slope.
[0015] If a set of frequency-dependent reception power threshold
values is determined for each modulation slope, a very effective
and simple interference recognition is possible. One individual set
of frequency-dependent reception power threshold values makes it
possible to determine for one modulation whether an interference
has occurred within the modulation.
[0016] Here, an interference may be detected for individual
frequencies of a modulation. Furthermore, an interference may also
be detected across a partial frequency range or the entire
frequency range of a modulation. In particular, interferences may
be differentiated from actual targets even within the frequency
range, in which targets usually occur, with the aid of the
modulation- and/or frequency-dependent reception power threshold
value. Furthermore, the present invention offers the possibility of
detecting any type of interferences in the admissible frequency
range.
[0017] These interferences may, for example, be caused by other
FMCW radar systems, FSK, step FMCW, chirp and/or pulsed radar
systems, as well as other radar systems.
[0018] Furthermore, a set of frequency-dependent reception power
threshold values for a known modulation may be determined once and
then stored. It is then possible to detect an interference by
effortlessly and very quickly comparing the reception power for a
certain frequency to the reception power threshold value which is
indicated for this frequency by the set of frequency-dependent
reception power threshold values.
[0019] A set of frequency-dependent reception power threshold
values for a certain modulation slope may, for example, be
determined with the aid of the FMCW equation, the general radar
equation, or a conditional equation derived from one of these
equations.
[0020] A set of frequency-dependent reception power threshold
values may not only be determined as a function of a certain
modulation slope. The set of frequency-dependent reception power
threshold values may also be determined, for example, as a function
of a relative speed range and/or of a target distance range and/or
for a maximally expected radar backscatter cross section of objects
which are to be detected with the aid of the radar. For this
purpose, a weighting between the recognition accuracy of
interferences and the likelihood of a false alarm regarding the
interference recognition may be performed when determining the set
of reception power threshold values. It is, in particular, possible
to illustrate a set of the frequency-dependent reception power
threshold values according to the present invention as a curve in a
diagram.
[0021] In one specific embodiment, the interference detector has an
evaluation unit, which is designed to determine the reception power
and the frequency of the received radar signals, a threshold value
unit, which is designed to determine at least one
frequency-dependent reception power threshold value based on the
certain frequency and the particular modulation parameters, and a
comparison unit which is designed to compare the determined
reception power threshold value to the reception power of the
received radar signals and to indicate the presence of an
interference if the reception power is greater than the reception
power threshold value. In another specific embodiment, the
threshold value unit is designed to determine the
frequency-dependent reception power threshold value based on the
certain frequency from a set of frequency-dependent reception power
threshold values corresponding to the particular modulation
parameters.
[0022] In another specific embodiment, the modulation parameters
also have a transmission power of the transceiver unit and/or an
antenna output of the transceiver unit and/or a maximally occurring
radar backscatter cross section of expected objects and/or a speed
at which the FMCW radar system moves and/or data of previously
detected objects, such as relative speed and/or distance. If other
modulation parameters are used to determine the frequency-dependent
reception power threshold value, the tolerance for detecting an
interference may be significantly reduced. In this way,
interferences are detected more reliably and the likelihood of a
false alarm is reduced. This increases the availability and the
quality of the object recognition of the FMCW radar system.
[0023] In one specific embodiment, the threshold value unit is
designed to also determine the reception power threshold value
based on an installation situation of the transceiver unit.
Additionally or alternatively, the threshold value unit is designed
to also determine the reception power threshold value based on a
transceiver characteristic of the transceiver unit. The transceiver
characteristic of the transceiver unit influences the reception
power of the FMCW radar system and depends on the particular
electrical as well as mechanical construction and the installation
situation of the FMCW radar system. If the installation situation
and the transceiver characteristic are taken into account when
determining the reception power threshold value, the accuracy of
the interference recognition is further increased. The influences,
which the installation situation and the transceiver characteristic
have on the particular reception power threshold values, may be
ascertained in simulations or may be determined through
measurements at the actual FMCW radar system.
[0024] In one specific embodiment, a first memory is provided in
which for each set of reception power threshold values at least two
reception power threshold values are stored for any differing
frequencies, the interference detector being designed to
interpolate a reception power threshold value for frequencies for
which no reception power threshold value is stored based on the at
least two stored reception power threshold values. If only a
selection of reception power threshold values of one set of
reception power threshold values is stored, it is possible to store
the particular set in a very efficient manner. In this case,
storing fewer reception power threshold values of a set of
reception power threshold values reduces the memory requirements
for storing the particular set to a fraction of the memory
necessary to store the entire set. Due to the interpolation, the
possibility is maintained to determine a reception power threshold
value for any frequency of a modulation.
[0025] In one specific embodiment, a second memory is provided in
which, for a plurality of sets of reception power threshold values,
at least two reception power threshold values for any differing
frequencies are stored in each case in one characteristics field.
If the reception power threshold values for different sets of
reception power threshold values are stored in one characteristics
field in one single memory, a particularly efficient access to the
individual reception power threshold values is possible. In
particular, the sets of reception power threshold values may be
stored in the characteristics field according to the sequence in
which the modulations corresponding to the individual sets are
transmitted by the FMCW radar system. The memory locations of the
subsequent set of the reception power threshold values may then be
accessed by simply adding an offset to an index to the reception
power threshold values.
[0026] The above-mentioned embodiments and refinements may be
combined in any desired manner, provided that the combination is
reasonable. Other possible embodiments, refinements, and
implementations of the present invention also include not
explicitly named combinations of features of the present invention
described previously or in the following with regard to the
exemplary embodiments. In particular, those skilled in the art will
add individual aspects as improvements or enhancements to the
particular base form of the present invention.
BRIEF DESCRIPTION OF THE DRAWINGS
[0027] The present invention is explained below in greater detail
with reference to the exemplary embodiments shown in the
figures.
[0028] FIG. 1 shows a block diagram of one specific embodiment of
an FMCW radar system according to the present invention.
[0029] FIG. 2 shows a flow chart of one specific embodiment of an
interference recognition method according to the present
invention.
[0030] FIG. 3 shows a block diagram of another specific embodiment
of an FMCW radar system according to the present invention.
[0031] FIG. 4 shows a diagram of an exemplary specific embodiment
of a set of reception power threshold values according to the
present invention.
DETAILED DESCRIPTION OF EXAMPLE EMBODIMENTS
[0032] In all figures, elements and devices which are identical or
have identical functions are identified with identical reference
numerals, unless otherwise indicated.
[0033] FIG. 1 shows a block diagram of one specific embodiment of
an FMCW radar system 1 according to the present invention. FMCW
radar system 1 has a transceiver unit 2 which transmits radar
signals 3 and receives radar signals 3a. Transmitted radar signals
3 are modulated with the aid of predefined modulation parameters.
Furthermore, transceiver unit 2 makes received radar signals 3a
available to interference detector 6 which detects interferences in
received radar signals 3a based on at least one frequency-dependent
reception power threshold value 8 corresponding to the particular
modulation parameters.
[0034] Interference detector 6 is designed as a microcontroller 6
which converts received radar signals 3a into digital data with the
aid of analog/digital converters and detects interferences in
received radar signals 3a.
[0035] In other specific embodiments, interference detector 6 is
designed as an embedded computer, as an application-specific
integrated circuit (ASIC), as a programmable logic component or the
like.
[0036] FIG. 2 shows a flow chart of one specific embodiment of an
interference recognition method according to the present
invention.
[0037] In FIG. 2, an FMCW radar system 1 according to the present
invention is made available in a first step S1. In a second step
S2, radar signals 3 are transmitted which are modulated with the
aid of at least one modulation parameter. Transmitted radar signals
3 which are reflected from objects are received in a third step S3.
In a fourth step S4, interferences are detected in received radar
signals 3a based on at least one frequency-dependent reception
power threshold value 8 corresponding to the particular modulation
parameters. Steps S3 and S4 may run simultaneously in one specific
embodiment.
[0038] Interferences are detected in another specific embodiment in
particular by comparing the value of the reception power of
received radar signals 3a to a corresponding reception power
threshold value 8. For this purpose, reception power threshold
value 8 is taken from the set of reception power threshold values 8
at the location corresponding to the frequency of the received
radar signal 3a. For this purpose, a set of reception power
threshold values 8 is made available for each variant of modulation
parameters used by FMCW radar system 1. In another specific
embodiment, the individual sets of reception power threshold values
8 are stored in the memory in the form of one single
characteristics field.
[0039] In one specific embodiment, the individual sets of reception
power threshold values 8 may be calculated based on the FMCW
equation, for example. In other specific embodiments, the sets of
reception power threshold values may be calculated with the aid of
the general radar equation or calculation specifications derived
therefrom. In yet other specific embodiments, the sets of reception
power threshold values may be determined experimentally, or the
calculated sets of reception power threshold values may be adjusted
to the particular application based on experimental studies.
[0040] In other specific embodiments, a set of reception power
threshold values may be determined in real time by threshold value
unit 7 and/or adjusted as a function of other data. These data may,
for example, be a speed of a vehicle having FMCW radar system 1 or
a speed of an FMCW radar system 1, data of detected objects, e.g.,
relative speed and distance, transmission power of the transceiver
unit or the like.
[0041] FIG. 3 shows a block diagram of another specific embodiment
of an FMCW radar system 1 according to the present invention.
[0042] The block diagram in FIG. 3 differs from the block diagram
in FIG. 1 in that interference detector 6 has an evaluation unit 9
which evaluates received radar signals 3a and makes available
reception power 11 of received radar signals 3a to a comparison
unit 10 as well as frequency 12 of received radar signals 3a to a
threshold value unit 7. Threshold value unit 7 determines an
appropriate reception power threshold value 8 for reception power
11 of received radar signals 3a at least based on a predefined
modulation parameter and frequency 12. Comparison unit 10 then
compares reception power 11 to reception power threshold value 8
and indicates an interference when reception power 11 exceeds
reception power threshold value 8. For this purpose, threshold
value unit 7 may read reception power threshold values 8 from a
memory or calculate them in real time.
[0043] FIG. 4 shows a diagram of an exemplary specific embodiment
of a set of the reception power threshold values according to the
present invention.
[0044] In FIG. 4, a diagram of an exemplary set of reception power
threshold values for a modulation slope of 400 MHz/ms is
illustrated in the form of a threshold value curve. The diagram is
further based on a radar backscatter cross section of 3000 m.sup.2,
a relative speed range from -75 m/s to +20 m/s, and a target
distance from 1 m to 200 m.
[0045] In one specific embodiment of a radar system according to
the present invention, the threshold value curve is stored in the
form of a set of reception power threshold values. Here, the points
of the threshold value curve in the set of reception power
threshold values are stored as pairs of frequency and reception
power. Here, the frequency distance of the pairs corresponds to the
frequency resolution of the transceiver unit.
[0046] In the diagram, the frequency of received radar signal 3a is
plotted on the abscissa. The plotted frequency starts at 0 kHz and
ends at 300 kHz; steps of 50 kHz are indicated on the abscissa in
each case. On the ordinate, the reception power is plotted in dB
from 0 dB to -60 dB in 10 dB steps. Furthermore, a curve is plotted
in the diagram. The curve proceeds from 0 Hz to approximately 40
kHz at approximately -8 dB. Subsequently, the curve drops to 300
kHz at an increasingly lower gradient up to approximately -57
dB.
[0047] The range above the upper curve is the range which is
considered as the interference detection range. If a reception
power, which is above the upper curve, is determined for a received
radar signal 3a at a frequency it is assumed that an interference
exists. If the reception power of received radar signals 3a is in
the range below the curve, it may be assumed that an object is
located in the recognition range of transceiver unit 2.
[0048] In one specific embodiment of the present radar system, the
frequency-dependent reception power threshold values correspond to
the upper curve of the diagram. In other specific embodiments,
other curve variations are possible as a function of the modulation
slope, other modulation parameters, and vehicle-specific
parameters.
[0049] Although the present invention was described above with
reference to preferred exemplary embodiments, it is not limited
thereto, but is modifiable in many ways. In particular, the present
invention may be changed or modified in various ways without
deviating from the core of the present invention.
* * * * *