阅读说明：本技术 具有同步化的高频模块的雷达传感器 (Radar sensor with synchronized high-frequency modules ) 是由 M·朔尔 M·迈尔 D·施泰因布赫 于 2019-06-18 设计创作，主要内容包括：本发明涉及一种具有至少两个同步工作的高频模块(10、12)的雷达传感器,所述高频模块分别具有至少一个信号路径(TX1、TST1；TX2、TST2),在所述信号路径中,被传递的高频信号的相位被改变了一个与温度有关的相位差,其特征在于,在每个高频模块(10、12)中,鉴相器(28)与所述信号路径(TX1、TST1；TX2、TST2)并联连接,所述鉴相器提供信号(U),在确定的相位差的情况下,所述信号与温度无关地具有极值,在所述信号路径(TX1、TST1；TX2、TST2)中布置有移相器(24),借助所述移相器能够如此调节所述相位差,使得所述鉴相器的信号(U)具有所述极值。(The invention relates to a radar sensor having at least two synchronously operating high-frequency modules (10, 12) each having at least one signal path (TX1, TST 1; TX2, TST2) in which the phase of the transmitted high-frequency signal is changed by a temperature-dependent phase difference, characterized in that in each high-frequency module (10, 12) a phase detector (28) is connected in parallel to the signal path (TX1, TST 1; TX2, TST2), which phase detector supplies a signal (U) which, in the case of a defined phase difference, has an extreme value independently of the temperature, and in that a phase shifter (24) is arranged in the signal path (TX1, TST 1; TX2, TST2), by means of which phase difference can be adjusted in such a way that the signal (U) of the phase detector has the extreme value.)

1. Radar sensor having at least two high-frequency modules (10, 12) which operate synchronously and each have at least one signal path (TX1, TST 1; TX2, TST2), in the at least one signal path, the phase of the transmitted high-frequency signal is changed by a temperature-dependent phase difference, characterized in that in each high-frequency module (10, 12) a phase detector (28) is connected in parallel with the signal path (TX1, TST 1; TX2, TST2), which phase detector provides a signal (U), in the case of a determined phase difference, which has an extreme value independently of the temperature, a phase shifter (24) is arranged in the signal path (TX1, TST 1; TX2, TST2), by means of which phase difference can be set in such a way that the signal (U) of the phase detector has the extreme value.

2. A radar sensor according to claim 1, wherein the phase detector (28) is formed by rectifying diodes on which the signals to be compared are superimposed on each other.

3. The radar sensor according to claim 1 or 2, wherein the phase shifter (24) is formed by an IQ-modulator.

4. Radar sensor according to any one of the preceding claims, wherein each high frequency module (10, 12) has a local oscillator (16), the local oscillators (16) of different high frequency modules (10, 12) being connected to a common reference signal source (30) by a line of known length.

5. The radar sensor according to any one of the preceding claims, wherein each high-frequency module (10, 12) has a mixer (22) which is configured to mix a signal received in a receive channel (RX) with a signal transmitted in a transmit channel (TX).

6. Radar sensor according to claim 5, wherein a synchronization signal output of each high-frequency module (10, 12) can be coupled to a synchronization signal input of each further high-frequency module (12, 10) via a signal path (L), the signals received via the synchronization signal path (L) being able to be supplied in each high-frequency module as transmission signals via the other signal paths (EXT1, EXT2) to the mixers (22) of the high-frequency modules.

7. Radar sensor according to claim 6, wherein in each of the high-frequency modules (10, 12) the output of at least one transmit channel (TX) forms a synchronous input and a synchronous output of the high-frequency module.

8. Radar sensor according to claim 6 or 7, wherein the mixer (22) of each high-frequency module (10, 12) can be supplied with the output signal of its own local oscillator (16) as a test signal via a signal path (TST 1).

9. Radar sensor according to any one of claims 5 to 8, wherein each high frequency module (10, 12) has a further mixer (26) configured to monitor the complex amplitude of the signal transmitted in the transmit channel (TX) of the high frequency module.

Technical Field

The invention relates to a radar sensor having at least two synchronously operating high-frequency modules, each of which has at least one signal path in which the phase of the transmitted high-frequency signal is changed by a temperature-dependent phase difference.

Background

In the case of radar sensors for motor vehicles, there is a trend of increasing complexity and in particular of increasing number of transmit and receive channels in an effort to approach targets of fully autonomous driving, for example in order to implement MIMO schemes (Multiple Input Multiple Output) or digital Beamforming (beamformng) schemes. In terms of reliability and power consumption, it is desirable here to limit the size of the high-frequency modules (MMICs) used in the radar sensor and instead to use a plurality of MMICs, which are preferably designed identically, which are synchronized with one another in such a way that the phase relationships between the signals transmitted in all transmission channels are known and can be taken into account appropriately when evaluating the received signals.

Due to the space requirement of the individual MMICs, as the number of modules increases, the spacing between the individual MMICs becomes so large that the signal propagation time of the signals used for synchronization can become non-negligible. This creates the particular difficulty that, in the case of large spatial distances between the individual MMICs, it is no longer possible to assume the same temperature for all MMICs, so that propagation time differences and phase differences of unknown magnitude can occur as a result of temperature changes of the electronic components.

Disclosure of Invention

The object of the invention is to provide a possibility: an accurate synchronization of the high-frequency modules is achieved even with temperature-dependent phase differences, and the function of the radar sensor is not impaired.

According to the invention, this object is achieved by: in each high-frequency module, a phase detector (phase detector) is connected in parallel with the signal path, which phase detector supplies a signal which, in the case of a defined known phase difference, has (anehmen) extrema independently of the temperature, and a phase shifter is arranged in the signal path, by means of which phase difference can be set such that the signal of the phase detector has extrema.

The invention provides the advantage that a temperature-dependent phase difference, which is unknown in its nature, can be set to a known value by means of a phase shifter and a phase detector, so that said phase difference can be taken into account when synchronizing the high-frequency modules. The phase detector used according to the invention, although it is not possible to quantitatively measure the phase difference, has the advantage that the point at which its signal has an extreme value is independent of the temperature, so that no disturbing temperature effects can occur when correcting the phase difference. The components to be added in the individual high-frequency modules, i.e. the phase discriminator and the phase shifter, can be integrated into the module without problems and without significantly affecting the power consumption or the measurement accuracy of the components.

Advantageous embodiments and embodiments of the invention are specified in the dependent claims.

The phase detector can for example involve a rectifier diode which, when loaded with signals at opposite ends of the signal path, provides as an output signal a direct voltage which is proportional to the superimposed amplitude of the signals and thus varies as a function of the phase difference between a maximum value (when the signals are constructively superimposed) and a minimum value (zero when the signals are completely cancelled).

For example, an IQ modulator can be used as a phase shifter in the signal path.

The synchronization of the different high-frequency modules can be achieved by means of specific synchronization signals exchanged between the modules. In a further embodiment, the transmission signal of the high-frequency module or of the transmission channel of this module (master) is simultaneously used as a synchronization signal for the further module (slave). In this case, each individual module can have a plurality of signal paths in which temperature-dependent phase differences can occur. In this case, a phase detector and a phase shifter are assigned to each of these signal paths.

Each high frequency module can have its own, voltage controlled local oscillator for generating the high frequency signal. A common reference signal can then be used to synchronize the oscillators in the different modules, which common reference signal is provided to all modules. Since the transmission path for the reference signal has no temperature profile, the phase differences resulting from the different propagation times of the reference signal to the individual oscillators are known or can be set to known values by suitable selection of the line length.

In the case of FMCW radars (Frequency Modulated Continuous Wave), the receiving channels of each high-Frequency module each have a mixer in which the received signal is mixed with a component (Anteil) of the signal transmitted at the same time, so that an intermediate-Frequency signal is generated whose spectrum provides information about the distance and relative speed of the located object during the measuring operation of the radar sensor. In one or more calibration modes, the mixer can be used to measure phase differences in different closed signal path chains. Since at least some of the chains also contain paths for the synchronization signals from one high-frequency module to another high-frequency module, all relevant phase differences can be determined when the phase differences for the remaining signal paths have been calibrated by means of phase detectors and phase shifters, so that the high-frequency modules can be correctly synchronized with each other.

In one embodiment, each high-frequency module can contain an additional mixer, by means of which the complex amplitude (magnitude and phase) of the transmit signal can be monitored.

Drawings

Embodiments are explained in more detail below with reference to the drawings.

The figures show:

fig. 1 shows a simplified circuit diagram of a radar sensor according to the invention, which has two high-frequency modules synchronized with one another; and

fig. 2 shows a signal characteristic of a phase detector used in the high-frequency module according to fig. 1.

Detailed Description

The radar sensor shown in fig. 1 has two high-frequency modules 10, 12, which are designed as MMICs, for example, and can be arranged on a common circuit board. Each high frequency module has a plurality of transmit channels and a plurality of receive channels. However, for the sake of simplicity of the diagram, only one transmit channel TX and only one receive channel RX are shown for each high frequency module.

For synchronization of the high-frequency modules 10, 12, a signal path L is provided which couples the outputs of the transmit channels TX of the two high-frequency modules to one another. For example, the radar sensor can be operated such that the high-frequency module 10 serves as a master and the high-frequency module 12 serves as a slave, which uses the signal transmitted on the signal path L as a synchronization signal. Since the two high-frequency modules 10, 12 have to be arranged at a distance from one another on the circuit board, the signals propagating on the signal path L have a certain signal propagation time which leads to a phase difference which is not known a prioriLThis phase difference must be compensated for correct synchronization of the modules.

Each of the two high-frequency modules 10, 12 contains a local oscillator 16 with a downstream amplifier 18. The output signal of the amplifier 18 is fed via a coupler 20 into the transmit path TX and transmitted as a transmit signal, on the one hand, and is supplied to a first input of a mixer 22, on the other hand. The signal received in the receive path RX is supplied to a second input of the mixer 22, so that the mixer 22 provides as an output signal the mixing product of the signals applied at the two inputs.

In the high-frequency module 10, a signal path EXT1 returns from the output of the transmission channel TX to the coupler 20. This enables the signal arriving via the signal path L to be used as an external transmit signal instead of the signal of the local oscillator 16 of the module itself. The signal path of coupler 20 to the output of transmit channel TX is referred to as TX 1. The signal path of coupler 20 to mixer 22 is referred to as LO 1. The two signal paths each contain a phase shifter 24, which is formed, for example, by an IQ modulator.

If no signal is received in the receive channel RX, the output signal of the input amplifier 18 is coupled directly at the associated input of the mixer 22 via the signal path TST 1. Signal path TST1 also includes phase shifter 24. The output of the phase shifter is connected to the input of the further mixer 26. The transmit signal intercepted at the output of the transmit channel TX can be provided to a further input of the mixer.

A phase detector 28, which is formed, for example, by a rectifier diode, is connected between this output of the transmit channel TX and the output of the amplifier 18. A further phase detector 28 is connected between the output of the amplifier 18 and the receive input of the mixer 22.

The local oscillators 16 of the two high-frequency modules 10, 12 have their inputs connected to a common reference signal source 30, which is used to synchronize the oscillators with one another. The connection between the two oscillators 16 and the reference signal source 30 can be regarded as a further signal path DPH, on which a phase difference can occurDPHThe phase difference depends on the respective line length. For example, the arrangement can be chosen such that the lines from the reference signal source 30 to each of the two oscillators 16 have the same length. In this case, the phase relation is appliedDPH＝0。

The high-frequency module 12 has the same configuration as the high-frequency module 10. The different signal paths are denoted here by the same letter designations as in the high-frequency module 10, but with the index "2" instead of "1".

A phase difference occurs in the signal path TX1TX1The phase difference has a component that is related to the local temperature. The same applies to the signal paths LO1, EXT1 and TST 1. The associated phase differences are each denoted by the same reference numeralsBut is underlined. The corresponding applies also to the signal paths in the high-frequency module 12. Phase difference in signal path LLAnd is generally also temperature dependent.

For synchronization of the two high-frequency modules 10, 12, a temperature-dependent phase difference needs to be calibrated. For this purpose, the radar sensor can be operated in four different calibration modes.

In calibration mode 1, the high-frequency module 10 supplies its transmit signal (output of the transmit channel TX) as a synchronization and transmit signal to the high-frequency module 12. The signal then passes to mixer 22 through signal paths TX1, L, EXT2 and LO 2. There, the mixing products are formed as measurement signals by means of the signals supplied via the signal path TST2 to the mixer 22 in the high-frequency module 12. The output signal of the mixer then represents the following phase difference:

D1＝(DPH+TX1+L+EXT2+LO2)-TST2 (1)

in calibration mode 2, the high frequency module 12 supplies its transmit signal to the mixer of the high frequency module 10. The signals are passed to the mixer 22 of the high-frequency module 10 via signal paths TX2, L, EXT1 and LO 1. There, the mixing products are formed together by means of the signals supplied via the signal path TST 1. In this case, the output signals of the mixer 22 are:

D2＝(-DPH+TX2+L+EXT1+LO1)-TST1 (2)

in calibration mode 3, the high frequency module 10 provides the transmit signal passed through signal path LO1 to its own mixer. There, the mixing products are formed by means of the signal delivered via the signal path TST1 as a reference signal. The output signals of the mixers then correspond to the following phase differences:

D3＝LO1-TST1 (3)

in calibration mode 4, the high-frequency module 12 supplies the transmit signal supplied to the mixer via the signal path LO2 to its own mixer 22. There, the mixing products are formed by means of a reference signal provided via signal path TST 2. The output signal of the mixer then represents the following phase difference:

D4＝LO2-TST2 (4)

the system of equations with ten variables is obtained by measurements in four calibration modes:DPH、TX1、L、EXT2、LO2、TST2、TX2、EXT1、LO1andTST1。

wherein the content of the first and second substances,DPHcan be determined from the line length and can therefore be considered known. For calibration of two high-frequency modules, phase differenceLNot directly related, but only by phase differenceL+EXT2Sum of constituents or sumL+EXT1Are related such thatLCan be eliminated as independent variables, instead, only the independent variables (c) need to be consideredL+EXT2) AndL+EXT1). Thus, there are eight unknowns remaining, but with the eight unknowns, the system of equations is still underdetermined.

Therefore, to solve the system of equations, four of the eight unknowns need to be determined in other ways. However, according to the invention, these unknowns are not measured directly (which would in turn require active components with their own unknown temperature course), but the unknown phase difference is corrected to a known value by means of the phase detector 28 and the phase shifter 24. For this purpose, a phase detector 28 is used, which, although not being able to carry out an absolute measurement of the phase difference, is able to carry out a temperature-independent determination of the phase difference because of its specific characteristic curve, which has a minimum value (or a maximum value) in the case of this phase difference. An example for such a characteristic is shown in fig. 2. The dc voltage U dropping across the rectifier diodes used as the phase detector 28 is plotted here as a function of the phase difference Φ of the signals superimposed on one another in the rectifier diodes. When the profile of the superimposed signal has a sinusoidal course, the characteristic curve has a maximum at a phase difference of 0 and 360 °, and a prominent minimum (differentiable) based on the characteristic curve is clearly locatable at a phase difference of 180 °. The phase difference can then be adjusted by means of the associated phase shifter 24 in such a way that the output signal U provided by the phase detector has this minimum value. Then, the phase difference between the signals compared with each other is known to be 180 °.

In fig. 1, in this way, the phase difference can be set by means of a phase detector 28 connected in the high-frequency module 10 between the amplifier 18 and the output of the transmission channel TX and by means of a phase shifter 24 in the signal path TX1TX1The adjustment is 180 °. By means of the phase detector 28 connected between the amplifier 18 and the mixer 22 and by means of the phase shifter 24 in the signal path TST1, the phase difference can be madeTST1The adjustment is 180 °. The corresponding applies also to the phase difference in the high-frequency module 12TX2AndTST2. Therefore, the same can be determined by equations (3) and (4)LO1AndLO2so that the remaining system of equations can be solved for the unknowns (L+EXT2) And (a)L+EXT1). Since all the relevant phase shifts can thus be determined independently of the temperature, the high-frequency modules 10 and 12 can be synchronized precisely with one another.

In the example shown, the signals transmitted in the respective transmission channels TX can be compared directly with the signals supplied to the mixer 22 in the calibration mode 1 or 2, using the mixer 26. Then, possible deviations can be compensated for by means of the phase shifter 24 in the signal path LO1 or LO 2.

The function of the above-described components of the high-frequency modules 10, 12 in the measuring operation and in the different calibration modes is controlled by an electronic control device, not shown.