WO2013117277A1

WO2013117277A1 - Radar sensor with monitoring circuit

Info

Publication number: WO2013117277A1
Application number: PCT/EP2012/075760
Authority: WO
Inventors: Christian Waldschmidt; Dirk Steinbuch; Raik SCHNABEL
Original assignee: Robert Bosch Gmbh
Priority date: 2012-02-10
Filing date: 2012-12-17
Publication date: 2013-08-15
Also published as: EP2812725A1; DE102012201990A1; CN104303074B; CN104303074A; DE102012201990B4

Abstract

The invention relates to a radar sensor for motor vehicles, having a monolithic, integrated microwave circuit (10) which comprises an oscillator (16) to generate a transmission signal and a mixer (20) to generate an intermediate frequency signal (IF) from a received signal, the monolithic, integrated microwave circuit (10) further comprising at least one sensor (28; 32; 38; 42; 58; 62; 64; 66) and a monitoring circuit (30; 62) which is configured to compare a measurement variable measured by the sensor to a desired state of the measurement variable, wherein the monitoring circuit (30) can be configured to control a circuit part (50) of the monolithic, integrated microwave circuit (10) on the basis of the result of the comparison.

Description

RADAR SENSOR WITH MONITORING

The invention relates to a radar sensor for motor vehicles, comprising a monolithic integrated microwave circuit (MMIC) comprising an oscillator for generating a transmission signal and a mixer for generating an intermediate frequency signal from a reception signal.

STATE OF THE ART

Radar sensors are used, for example, in motor vehicles for detecting the surroundings of the vehicle and for locating vehicles in front. For example, driver assistance systems are known that have comfort functions, for example, a distance and / or cruise control, such as a cruise control. an ACC system (Adaptive Cruise Control). Safety systems or driver assistance systems with safety functions based on the evaluation of radar sensor signals, such as e.g. an automatic emergency brake (AEB). DE 10 2010 002 638 A1 describes a radar sensor with an interface and with an integrated MMIC component, which comprises a transmitting and receiving device for a radar signal, a control device and an interface unit. Information received via the interface and evaluated by the interface unit can effect adjustment of parameters of the transmitting and receiving device via digital / analog converters of the control device. Conversely, operating states of the transmitting and receiving device can be interrogated via the interface unit via analog / digital converters provided in the control device.

DISCLOSURE OF THE INVENTION

In safety systems that actively intervene in the driving behavior of the vehicle, particularly high demands are placed on the reliability of the system.

The object of the invention is to provide a radar sensor which enables improved system security. This object is achieved by a radar sensor of the type mentioned, in which the monolithic microwave integrated circuit further comprises at least one sensor and a monitoring circuit which is adapted to compare a measured by the sensor measured variable with a desired state of the measured large. This allows very low latency and / or higher accuracy monitoring than when using external monitoring components. Thus, for example, a faster error detection and thus a lower error tolerance time can be made possible. In addition, an at least partially self-sufficient monitoring can be realized within the MMIC. Thus, the safety of actively engaging in driving behavior safety systems can be significantly improved. The desired state of the measured variable may, for example, consist of a desired value of the measured variable or comprise a setpoint range of the measured variable. The measured variable is preferably an in-circuit measured variable of the MMIC, in particular a measured variable related to a respective measuring point. The measured quantity may be, for example, a temperature, a measured variable characterizing a property of an oscillating signal, wherein the at least one oscillating signal may comprise a transmission signal, a received signal and / or an intermediate frequency signal, and / or an electrical measured variable. Examples are given in claim 4. When comparing the measured variable measured with the desired state, for example, a time course of the measured variable can be taken into account. By way of example, the monitoring circuit can be set up to compare a value, determined on the basis of a time profile of a measured signal, of a measured variable with a desired state of the measured variable characterizing a time characteristic of the signal.

The MMIC may include one or more sensors and one or more monitoring circuits configured to compare a measured variable measured by the sensor or a plurality of measured variables measured by one or more sensors with a desired state of the measured variable (s), in particular, for example to compare with a respective nominal state of the respective measured variable. So In particular, the nominal state of a measured variable may be dependent on the value of another measured measured variable. A sensor can be set up to measure a plurality of measured variables, for example a temperature at a plurality of measuring points. In particular, the MMIC may comprise a switching device for connecting a sensor to one of different measuring points of the monolithic microwave integrated circuit. The monitoring circuit can be set up, for example, to control the switching device.

The at least one sensor may have, for example, an A / D converter (analog / digital converter), for example an A / D converter for the relevant measured variable. However, the measured variable may also be a measured variable measured on an A / D-converted signal. For example, the sensor may comprise an A / D converter and a measuring unit in the form of a digital circuit or a program algorithm for a program-controlled processing unit for determining the measured variable based on the A / D-converted signal. BRIEF DESCRIPTION OF THE DRAWINGS

Preferred embodiments of the invention are explained below with reference to the drawings.

Show it:

Fig. 1 is a schematic block diagram of a radar sensor for motor vehicles; FIG. 2 shows a control circuit for a power of a buffer amplifier; FIG.

3 shows a further control circuit for a power of a buffer amplifier; a block diagram of a circuit part of the radar sensor for evaluating an intermediate frequency signal;

5 shows a block diagram of a circuit part of the radar sensor for monitoring the processing of a control command; Fig. 6 is a block diagram of a transmission / reception channel of the radar sensor;

FIG. 7 shows a control circuit for a phase position of a signal; FIG.

8 shows a control circuit for a power of a signal;

9 shows a further control circuit for a power of a signal; 10 shows a control circuit for a duty cycle of a transmission signal;

11 is a block diagram of a circuit part of the radar sensor for monitoring an antenna element;

Fig. 12 is a block diagram of another example of a transmission / reception channel;

and FIG. 13 shows a block diagram of a circuit part of the radar sensor for monitoring the relative phase position of a plurality of channels.

DESCRIPTION OF EMBODIMENTS

Fig. 1 shows a radar sensor for motor vehicles with a monolithic microwave integrated circuit (MMIC) 10 and antenna elements 12. The radar sensor is connected to an evaluation circuit 14 for the evaluation of intermediate frequency signals IF (intermediate frequency) of the radar sensor. The MMIC 10 includes a voltage controlled oscillator 16 (VCO) for generating a radar transmit signal, and a plurality of transmit / receive channels 18 connected to respective antenna elements 12 and a mixer 20 for generating an intermediate frequency signal IF, respectively a radar received signal. The operating frequency of the oscillator 16 is for example about 77 GHz.

The intermediate frequency signals IF of the channels 18 are applied to inputs of the evaluation circuit 14. The basic structure of such a transmitting / receiving part of a radar sensor for motor vehicles is known. The radar sensor 10 and the evaluation circuit 14 may be part of a driver assistance system for example. be in control of the vehicle. The radar sensor has at least one channel 18, for example four channels 18.

The MMIC 10 comprises an analog circuit part 10a, a digital circuit part 10b and an interface 22 for driving the analog circuit part 10a and for communication with the digital circuit part 10b. The analog circuit part 10a comprises the oscillator 16 and the channels 18. A control input of the oscillator 16 can be controlled via the interface 22.

The interface 22 is connected, for example, via a phase-locked loop (PLL) 24 for controlling the oscillator 16 to its control input, wherein an output of the oscillator 16 is connected via a frequency divider 26 to an input of the phase locked loop 24. The frequency divider 26 may, for example, be in the form of variable divider chains or comprise a mixer for downmixing the output signal of the oscillator 16 by means of a reference oscillator and comprises, for example, the reference oscillator. The interface 22 comprises an A / D converter 28 which is connectable to the output of the frequency divider 26 and allows A / D conversion of the output signal of the oscillator 16. A processing unit 30 of the digital circuit part 10b is configured, for example, to measure the frequency of the A / D converted output signal and thus to monitor the frequency of the output signal, for example to compare it with a desired value. For example, the processing unit 30 may be a programmable or hard-coded processing unit 30. The processing unit 30 forms a monitoring circuit and, together with the frequency divider 26 and the A / D converter 28, a sensor for measuring the frequency of the output signal of the oscillator 16. A part of the processing unit 30 belonging to the sensor can be used, for example, as a measuring unit 32 in FIG Form of a program algorithm be formed. The processing unit 30 is connected to a memory 34 and includes this. The monitoring circuit is configured to transmit an alarm signal AL (alarm) to the evaluation circuit 14 upon detection of a malfunction of the oscillator 16 of the MMIC. The processing unit 30 is additionally connected to a non-volatile FLASH memory 36. The non-volatile memory 36 is set up to store control commands, operating parameters or values of measured variables. These are then also after an interruption of the power supply, such as a defect, a shutdown of the sensor and / or the vehicle still ready. A monitoring circuit formed by the processing unit 30, in particular a monitoring circuit according to one of the examples described in this application, may for example be configured to control a circuit part taking into account at least one data value stored in the nonvolatile memory 36, for example at least one control command, operating parameter and / or at least one previous value of a measurand. A control command or operating parameter may, for example, define a desired state of a measured variable. This allows, for example, a controlled by the monitoring device self-calibration of the measurement variable influencing circuit part. A monitoring circuit formed by the processing unit 30, in particular a monitoring circuit according to one of the examples described in this application, can for example be set up to compare a measured variable measured by a sensor with a desired state taking into account at least one previous value of a measured variable stored in the memory 36 , This allows, for example, the monitoring of degradation effects, in which a deviation from the target state gradually increases.

Optionally, a monitoring device formed by the processing unit 30 may be configured to log values of a measured parameter or of an operating parameter in the nonvolatile memory 36. This allows for improved diagnostics options in the event of a fault. For example, logging can occur at regular intervals and / or when a malfunction is detected.

The non-volatile memory 36 optionally includes a tuning characteristic of the oscillator 16, which indicates a voltage-dependent frequency response of the oscillator 16. The above-mentioned monitoring circuit is configured, for example, on the basis of a memory 34 stored in the nonvolatile memory 36 Characteristic of the oscillator 16 and on the basis of the comparison result to drive the oscillator 16 according to a predetermined frequency or to control according to a predetermined frequency ramp, ie to modulate its frequency accordingly. For this purpose, for example, for a desired frequency of the output signal of the oscillator 16, a control voltage for the oscillator 16 corrected for the characteristic curve or for a reference oscillator of the phase locked loop 24 is determined. A monitoring of the frequency of the output signal of the oscillator, as described, via the A / D converter 28 and the measuring unit 32nd

The interface 22 may comprise one or more A / D converters 28, which, for example by means of a multiplexer, can be connected to different measuring points of the analog circuit part 10a in order to enable the monitoring of respective measured variables. In Fig. 1, only an A / D converter 28 is shown for the sake of illustration.

Optionally, the analog circuit part 10a comprises at least one temperature sensor 38, which is connected to the interface 22 and, for example, to the same or another A / D converter 28 is connectable.

The processing unit 30 optionally forms a monitoring circuit for the temperature measured by the temperature sensor 38. The temperature sensor 38 is configured to measure a temperature in the vicinity of the oscillator 16. The monitoring circuit is configured, for example, to control the oscillator 16 as a function of the measured temperature, for example via the control voltage of the oscillator 16 or a reference oscillator of the phase-locked loop 24. The frequency of the output signal of the oscillator 16 can in turn be monitored by the processing unit 30. The monitoring circuit is configured to transmit an alarm signal AL (alarm) to the evaluation circuit 14 upon detection of a malfunction of the oscillator 16 of the MMIC, such as failure to reach a setpoint frequency.

Instead of or in addition to the tuning characteristic curve, a temperature characteristic curve (temperature response) may also be taken into account when controlling the oscillator 16, which characterizes a temperature-dependent frequency response of the oscillator 16 and is stored, for example, in the nonvolatile memory 36. Through the Considering the tuning characteristic and / or the temperature characteristic, an improved control behavior of the phase-locked loop 24 can be achieved.

The analog circuit part 10a further comprises a buffer amplifier or buffer 40 for variably amplifying the output signal of the oscillator 16. A part of the output signal is fed to the frequency divider 26, another part to the buffer 40. The buffer 40, in particular its output power, is can be controlled via the interface 22. The output signal of the buffer 40 is supplied as an LO (local oscillator) signal to the transmission / reception channels 18. The analog circuit part 10 a optionally includes a power sensor 42 for measuring the power of the LO signal connected to the interface 22. The processing unit 30 forms, for example, a monitoring circuit for comparing the power measured by the power sensor 42 with a desired state.

According to the control circuit shown in FIG. 2, the monitoring circuit is set up to control the buffer 40 on the basis of the measured power P _act and a setpoint value P _set, and in particular to regulate the power of the LO signal.

For example, a temperature sensor 38 may be configured to measure a temperature dependent on the temperature of the buffer 40. It may, for example, be arranged in the vicinity of the buffer 40. Several temperature sensors 38 can be provided at different measuring points of the analog circuit part 10a, for example within the respective channels 18. This allows more accurate temperature measurements in temperature-critical areas. For example, processing unit 30 may be configured to measure a temperature by interpolation or extrapolation based on measured temperatures of a plurality of temperature sensors 38. Thereby, temperatures may also be determined for circuit points where a temperature sensor can not be located directly.

3 shows a control loop formed by the monitoring circuit for controlling the output power P _{act of} the buffer 40 based on a temperature T _act measured by a temperature sensor 38, a set value of the temperature T _set and an initial value of the power P _start . This makes it possible to provide a desired output power of the buffer 40 for any operating states of the radar sensor. Since the control loops are implemented internally in the MMIC, an improved control behavior can be achieved compared to the use of external sensors. If a desired output power of the buffer 40 is not reached and / or an admissible maximum temperature is exceeded (limit of a setpoint range), the monitoring circuit detects a malfunction and transmits a corresponding alarm signal to the evaluation circuit 14.

The evaluation circuit 14 is connected to the MMIC 10 via the interface 22.

An output of the oscillator 16 is connected to the channels 18 to provide each of the channels 18 with a reference signal "test". For example, a part of the buffer 40 supplied to the output signal of the oscillator 16 is coupled. For example, the reference test signal has a frequency of about 77 GHz. For example, the reference test signal may be coupled to the LO signal.

FIG. 4 shows an optional monitoring circuit formed by the processing unit 30 for monitoring a measured variable which identifies an intermediate frequency signal of one or more channels 18. A sensor for measuring such a measured variable comprises, for example, an A / D converter 28 of the interface 22 and a measuring unit 32 of the processing unit 30. The sensor is configured, for example, to provide an intermediate frequency signal IF of one or more of the channels 18 by means of the A / D converter 28 to digitize and based on the digitized signal

to measure the measurand. The measured variable may be any desired variable relevant to the reliability of the radar sensor, for example a DC voltage component of the intermediate frequency signal IF. The DC voltage component can be compared, for example, with a nominal value range of the DC voltage component. For example, when leaving the setpoint range, an alarm signal AL can be transmitted to the evaluation circuit 14.

Fig. 5 shows schematically a circuit part of the radar sensor for controlling a circuit part of the analog circuit part 10a, generally indicated by reference numeral 50. The interface 22 comprises an interface 44, which is connected to the processing processing unit 30, for example, a serial three-wire interface in the form of a serial peripheral interface bus (SPI bus) with lines for a selection signal CS (Chip Select), a clock signal CLK (Clock) and a data signal SISO (Signal In - Signal Out) on , The SPI interface 44 is configured to write control commands and / or operating parameters to at least one shift register 46 of the interface 22 and to read it from the shift register 46. The interface 22 comprises at least one D / A converter 48 for controlling the circuit part 50 based on control commands / operating parameters transmitted by the processing unit 30. The at least one D / A converter 48 is connected or connectable, for example, to a circuit part 50. The circuit part 50 can be, for example, the phase locked loop 24, the oscillator 16, the buffer 40, a modulation device for the transmission frequency or the frequency of the oscillator 16, or one of the circuit parts controllable via the interface 22 or the processing unit 30, described below act. A control command may, for example, consist of a value of a control variable for the circuit part 50, for example a value of a control voltage of the oscillator 16.

A sensor in the form of an A / D converter 28 of the interface 22 is connectable to the circuit part 50 and adapted to measure a control command or operating parameter of the circuit part 50, i. to digitize and transfer to the shift register 46 for readout by the processing unit 30. The processing unit 30 is optionally configured to monitor the control command / operating parameter measured by the A / D converter 28 and to compare it with a target value, for example the previously issued control command / operating parameter. Thereby, it can be monitored whether the control command / operating parameter has been correctly converted by the D / A converter 48 and the circuit part 50.

If an impermissible deviation is detected when comparing a desired value with a read-out value, the processing unit 30 may be configured to transmit the relevant control command / operating parameter again to the circuit part 50 and / or a result of an operation to be controlled by the control command / operating parameter Discard MMIC 10. The interface 22 may optionally have a further SPI interface for connection to the evaluation circuit 14. The evaluation circuit 14 may form a monitoring circuit for monitoring a transmitted to the circuit part 50 control command / operating parameter. It can, for example, assume the described functions of the processing unit 30. A structure of an interface between a circuit part 50 of an MMIC and a digital processing unit 30 integrated in the MMIC and / or an evaluation circuit 14, as described above with reference to FIG. 5, also represents an independent invention independently of the other components and features of the radar sensor described It is also possible to monitor the transmission of a control command / operating parameter, for example, by reading out the control command / operating parameter again from the shift register 46 via the D / A converter 48 via a D / A converter 48 to a circuit section 50. This allows a comparison to the original value. In addition, it is ensured that the register information in the shift register 46 has not changed since writing.

Fig. 6 shows schematically a block diagram of a channel 18 and its connection to the interface 22 and antenna elements 12. The channel 18 is supplied with the LO signal from the buffer 40 and the reference test signal "Test". 6 shows an example of an operation of a channel 18 with at least one transmit / receive antenna element 12, which serves both to emit the transmit signal and to receive a receive signal. The LO signal is supplied to the mixer 20 via an optional phase shifter 52. The phase shifter 52 is arranged to adjust the phase of the signal applied to the mixer and thus allows the heterodyne operation of the channel 18. The LO signal is supplied to the antenna element 12 as a transmission signal via an optional amplifier 54 and an optional phase shifter 56. The amplifier 54 and the phase shifters 52, 56 can be controlled via the interface 22. An optional phase detector 58 forms a sensor for measuring the phase position of the signal supplied to the mixer 20 of the phase shifter 52. A monitoring circuit formed by the processing unit 30 is adapted to the phase position measured by the phase detector 58. to compare with a desired state. The phase detector 58 is connectable to the output of the phase shifter 52. The same or a further phase detector 58 can be connected to the output of the phase shifter 56. A power sensor 42 is also connectable to the output of the phase shifter 56 or to the output of the amplifier 54. The processing unit 30 forms, for example, a monitoring circuit for comparing a phase position of the output signal of the phase shifter 56 measured by the phase detector 58 and / or for comparing a power of the transmission signal measured by the power sensor 42 with a desired state. Thus, the effective phase position and the amplitude of the transmission signal can be measured internally in the MM IC 10 and monitored.

7 shows a control circuit for the phase position (p _{act of} an output signal of the phase shifter 52 or 56, based on a setpoint value ( _pset)) which controls the respective phase shifter 52, 56 based on the measured phase position and thus to regulate the phase position.

FIG. 8 shows a control circuit for the power of the transmission signal, in particular the output power of the amplifier 54, which comprises the monitoring circuit. The monitoring circuit is set up to control the amplifier 54 based on the output power P _act measured by the power sensor 42 and thus the output power based on a Setpoint P _set to regulate.

Thus, defined phase and / or amplitude ratios between the channels 18 and with respect to the LO signal can be adjusted. This may allow monitoring, control or regulation of a field of view of the radar sensor.

9 shows a control loop with a temperature sensor 38 for detecting a temperature in the vicinity of the amplifier 54 of a channel 18. According to the example of FIG. 3, the processing unit 30 forms a monitoring circuit for a temperature measured by the temperature sensor 38 and is adapted to to regulate the output power of the amplifier 54 and thus the transmission power channel individually in consideration of the temperature. Fig. 10 shows a control circuit for a duty cycle of the transmission signal or the LO signal. A monitoring circuit formed by the processing unit 30 is configured to measure by means of a temperature sensor 38 a dependent of the temperature of the oscillator 16 temperature T _act . The monitoring circuit is configured to compare the measured temperature T _act with a desired value T _set and to control the oscillator 16 based on the comparison result, in particular to control a control device 60 for controlling the duty cycle and frequency modulation of the oscillator 16. Thus, the duty cycle can be optimized taking into account the temperature at a given transmission power, optionally taking into account a selectable operating mode "mode", such as an energy-saving operating mode or a sports mode. For example, controlling the duty cycle may include setting a length of a pause between two transmit phases, each including at least one frequency ramp.

FIG. 6 further shows an antenna monitoring device 62, which is set up for monitoring an antenna parameter characterizing the functionality of an antenna element 12. The antenna parameter may be, for example, a measured variable characterizing the coupling of the antenna element 12 to the MMIC 10, for example an electrical resistance or an impedance, for example a difference between a channel-side impedance and an antenna-side impedance.

As shown in FIG. 11, the antenna monitoring device 62 forms a sensor for measuring at least one antenna parameter and transmitting it via the interface 22 to the processing unit 30. Depending on the result of a comparison of the measured variable with a desired state of the relevant antenna parameter, the processing unit 30 detects the presence of a malfunction of an antenna element 12 or the coupling of the antenna element. Upon detection of a malfunction, the processing unit 30 outputs a corresponding alarm signal AL to the evaluation circuit 14. The MMIC 10 can thus independently detect any fault of the antenna or the antenna coupling and, for example, an interrupt in the evaluation circuit 14 via the alarm signal AL trigger. An alarm line of the processing unit 30 is connected to an interrupt input IRQ of the evaluation circuit 14, as shown in FIG. 11.

Fig. 12 shows a block diagram of a transmission / reception channel 18 in which separate antenna elements 12 are provided for transmission and reception. The antenna elements 12 are respectively monitored by associated antenna monitoring devices 62 "RX sense" or "TX sense", which monitor antenna parameters of the antenna elements 12 in a corresponding manner. Otherwise, the circuits of the channels 18 in FIG. 6 and in FIG. 12 correspond to one another.

In the examples of FIGS. 6 and 12, the antenna element 12 configured for reception is connected to the mixer 20 in order to supply the received signal. The received signal is also supplied to a phase detector 64, which forms a sensor for the phase position of the received signal. The processing unit 30 forms a monitoring circuit for comparing the phase position measured by the phase detector 64 with a desired state. The channel 18 further comprises an offset detection / compensation unit 66, which is configured to measure and / or compensate for a DC voltage component at the intermediate frequency signal output of the mixer 20. It forms, for example, a sensor for the DC component. The processing unit 30 forms, for example, a monitoring circuit for comparing the measured DC voltage component with the nominal value zero and is set up, for example, to actuate the offset detection / compensation unit 66 to compensate for the DC voltage component, for example by injecting an opposing direct current into the DC depending on the result of the comparison Mixer. Additionally or alternatively, the monitoring circuit may be configured to compare the DC voltage component measured by the offset detection / compensation unit 66 with the desired value and, based on the comparison result, to control the phase position of the LO signal supplied to the mixer 20. The processing unit 30 can control the phase shifter 52 for this purpose. By changing the phase relationship between the LO signal and the received signal, the DC component of the intermediate frequency signal IF at the output of the mixer 20 can be minimized. The DC voltage component can be measured, for example, by measuring a DC-coupled intermediate frequency signal. Alternatively, the processing unit 30 may be configured to perform a Fourier transformation of an intermediate frequency signal IF digitized via an A / D converter 28 and determination of the DC voltage component. It thus forms together with the A / D converter 28 a sensor for the DC voltage component.

The channel 18 circuitry shown in FIGS. 6 and 12 optionally includes a built-in self-test (BIST) test signal generator 68 configured to generate a test signal based on the supplied reference test signal "test." to create. This is fed via an optional controllable buffer amplifier 70 and an optional controllable phase shifter 72 an input of the mixer 20 to simulate the reception case during a self-test. The test signal generator 68 can be formed, for example, by a modulator or by an oscillator coupled to the reference test signal. The analog circuit part 10a includes a power sensor 42 for measuring the power of the test signal, which is connectable to the buffer amplifier 70, for example, and a phase detector 58 (sensor) for measuring the phase position of the test signal. A temperature sensor 38 is disposed in the vicinity of the signal generator 68 and / or the buffer amplifier 70. The processing unit 30 forms monitoring circuits for monitoring the output power of the test signal measured by the power sensor 42, the phase position of the test signal measured by the phase detector 58 and / or the temperature measured by the temperature sensor 38. According to the examples of FIGS. 7, 8 and 9, the monitoring circuits are set up to regulate the power P _{act of} the buffer amplifier 70 as a function of a measured value P _set and / or the temperature or the phase position of the test signal (p _act in response to a setpoint (p _set by controlling the phase shifter 72 to regulate.

The processing unit 30 thus forms a monitoring circuit for monitoring the mixer 20 by means of a test signal supplied to the mixer 20 and is adapted, when the test signal is supplied, to ensure the functionality of the mixer. schers 20 characteristic measured variable and to compare with a nominal state. The measured variable may be, for example, a frequency, an amplitude and / or a phase position of the intermediate frequency signal IF at the output of the mixer 20. By monitoring the temperature and controlling the power of the test signal as a function of the measured temperature, it is possible to specify a setpoint temperature for the self-test. Thus, by regulating the output power of the buffer amplifier 70, the temperature of the relevant part of the circuit of the channel 18 can be increased until the setpoint temperature is reached. As a result, for example, a self-test near a specification limit can be performed.

The test signal generators 68 of the channels 18 are individually controllable by the processing unit 30, i. for example, activated and deactivated. The adjustable buffer amplifiers 70 and phase shifters 72 allow a channel-specific adjustment of the amplitude and the phase of the respective test signal, wherein the set values can be monitored and verified by the sensors 42, 58. 13 shows by way of example that the monitoring circuit formed by the processing unit 30 can be set up to control the phase positions of the test signal of the individual channels 18 as a function of the measured phase positions of the test signals of the individual channels 18, so that predetermined desired phase positions φ (FIG. with n = 4) relative to the phase of the LO signal. In a corresponding manner, the amplitude relationships of the test signals can also be regulated relative to the LO signal. Thus, specifically desired storage frequencies in the spectrum of the intermediate frequency signal can be generated.

In a corresponding manner, a measurement and monitoring of the phase positions of the received signals of the channels 18 can be carried out by the phase detectors 64. For example, the processing unit 30 may form a monitoring circuit to monitor the received signals by measuring their relative phase angles and comparing them with setpoints. The setpoints may be stored in non-volatile memory 36, for example. In this way, for example, the deviation from a desired characteristic of the reception branch can be determined. The monitoring The switching circuit can be set up, for example, to control the phase shifter 52 as a function of the comparison result in order to calibrate the phase position of the received signals.

As was illustrated with reference to the examples of FIGS. 1 to 13, the MMIC 10 comprises at least one monitoring circuit which is set up to compare a measured variable measured by a sensor of the MMIC 10 with a desired state and, if appropriate, a function of the comparison result Circuit part of the MMIC 10 to control. The respective monitoring circuit can be set up, for example, to automatically regulate the relevant measured variable into its nominal state as part of an MMIC-internal control loop. The respective monitoring circuit can also be set up to output an alarm signal AL upon detection of a malfunction which, for example, prevents reaching the desired state. The reliability of the radar sensor is thus significantly improved by the internal MMIC monitoring. For example, an alarm signal AL indicating the type of malfunction can be output. The alarm signal AL may have about a coding for the cause of the error or the malfunction. In the switch-on state, an alarm signal is preferably output which identifies an error and is canceled only after a successful monitoring of the relevant measured variable. This can ensure that in case of an internal defect not malfunctioning is signaled.

By means of an integrated monitoring circuit, the time for monitoring can be determined internally in the MMIC 10, so that the control of the processes is simplified. In addition, an internal detection of a malfunction, for example, allows a corrective measure by a circuit part of the MMIC 10 is controlled via the interface 22 in dependence of the comparison result of the measured variable with the desired state, for example by transmitting a control command or operating parameter or by triggering a reset of the circuit part. Thus, certain situations with erroneous measured variables can be resolved internally, without a malfunction is reported to the evaluation circuit 14.

Claims

A vehicular radar sensor comprising a monolithic microwave integrated circuit (10) including an oscillator (16) for generating a transmit signal and a mixer (20) for generating an intermediate frequency signal (IF) from a receive signal, the monolithic microwave integrated circuit further comprising at least one sensor (28; 32; 38; 42; 58; 62; 64; 66) and a monitoring circuit (30; 62) arranged to compare a measured variable measured by the sensor with a desired state of the measured variable.

A radar sensor according to claim 1, wherein the monolithic microwave integrated circuit (10) comprises a digital program-controlled processing unit (30) forming at least part of the monitoring circuit (30; 62).

A radar sensor according to claim 1 or 2, wherein said monolithic microwave integrated circuit (10) comprises at least one analogue to digital converter (28).

Radar sensor according to one of the preceding claims, wherein the measured variable at least one of a temperature, a frequency and / or phase of at least one oscillating signal, an amplitude, a power and / or a DC component of at least one oscillating signal, a power of an amplifier (40; 70), an electrical current, an electrical voltage, a resistance, an impedance, an operating parameter of a circuit part (50), and an antenna parameter of an antenna element (12) of the radar sensor.

Radar sensor according to one of the preceding claims, wherein the monitoring circuit (30) is further adapted to control based on the comparison result, a circuit part (50) of the monolithic microwave integrated circuit (10), in particular a set up for influencing the measured variable circuit part (50). A radar sensor according to claim 5, wherein the circuit portion (50) comprises at least one of an oscillator (16; 68), an amplifier (40; 54; 70), a phase shifter (52; 56; 72), a duty cycle controller (60) an oscillator (16) and an offset compensation unit (66) for compensating a DC component of the intermediate frequency signal (IF).

A radar sensor according to claim 5 or 6, wherein the monitoring circuit (30) is arranged to control the circuit part (50) considering at least one data value stored in the nonvolatile memory (36).

Radar sensor according to one of the preceding claims, wherein the oscillator (16) via a frequency or phase-locked loop (24) is controlled, and wherein the radar sensor in addition to the frequency or phase locked loop (24) the at least one, in the monolithic microwave integrated circuit (10 integrated sensor (28; 32; 38; 42; 58; 62; 64; 66) and the monitoring circuit (30; 62) integrated in the monolithic microwave integrated circuit (10).

Radar sensor according to one of the preceding claims, wherein the monitoring circuit (30; 62) is adapted to detect a malfunction based on the comparison result and to output an alarm signal in the event of a detected malfunction.

A radar sensor according to any one of the preceding claims, wherein the monolithic microwave integrated circuit (10) comprises a nonvolatile memory (36) and the monitoring circuit (30; 62) is adapted to receive a signal from the sensor (28; 32; 38; 42; 58; 62; 64; 66) measured variable, taking into account at least one measured at an earlier time and in the non-volatile memory (36) stored value of the measured variable with a desired state of the measured variable to compare.