DE19731085A1 - Device for transmitting and receiving radar waves, in particular for a distance sensor - Google Patents

Abstract

The invention relates to a device for sending and receiving radar waves, especially for a distance sensor, wherein the send signals can be transmitted to at least one antenna element and the receive signals can be extracted therefrom. The antenna elements used for transmission are formed by circular polarized radar waves. The send signals are supplied to at least one side of the antenna element so that they are diffused on a first polarization plane. The receive signals are picked up by the antenna element on a second polarization plane which is perpendicular to the first polarization plane.

Description

The invention relates to a device for transmitting and Receiving radar waves, especially for one Distance sensor, at least one antenna element for Example of a surface antenna, signals to be transmitted in one Directed and separated from it and electrically decouples signals received in the opposite direction are removable.

For distance sensors, particularly on motor vehicles are often used frequency modulated Microwaves (FMCW principle) are used, with one Comparison of the respective frequency of the transmitted and the after a reflection received wave on the distance can be closed to reflective obstacle. Here are often the same antenna elements to send and Receiving used.

The object of the present invention is a Transmit-receive isolation with low losses with sufficient To achieve isolation.  

This object is achieved in that the Antenna elements for transmitting circularly polarized Radar waves are formed and that to be transmitted Signals at least on one side of the antenna element be supplied in a first polarization plane be emitted, and that the received signals from Antenna element on a second polarization plane be tapped to the first polarization level is orthogonal. It is preferably provided that the Antenna element is essentially square and that the Feeding and taking the signals from at least two polarization-orthogonal points.

In the device according to the invention, the circular polarization by two diagonally opposite Bevels or through a diagonal slot be effected.

There is a further development of the device according to the invention in that a further supply of signals to be sent from the direction of the received signals. It is a particularly advantageous feed of the to be sent and a removal of the received signal possible that two connections of a 3dB coupler (branch line coupler, Rat-race-coupler) connected in this way to the antenna element are that the signals to be sent on one side of the Antenna element opposite the other side by 90 ° are out of phase that a third connection of the 3dB coupler the received signals are removable and that the signals to be sent can be fed to a fourth connection are.

Another development provides that a Directional coupler in the feed of the signals to be sent to Antenna element is switched and that a coupling arm of  Directional coupler connected to an input of a mixer whose other input is the received signals are feedable and at the exit Intermediate frequency signal can be removed. Preferably thereby for phase adjustment between the coupling arm and the A detour line inserted at the input of the mixer.

A particularly inexpensive construction with the currently Technologies available for manufacturing integrated circuits for microwaves is according to one other training possible that to generate the a controllable oscillator to be sent signals whose frequency is via a frequency control loop a modulation signal supplied can be modulated and whose output signal via a frequency doubler can be fed to at least one antenna element.

A particularly favorable embodiment of this training is that the frequency control loop one Includes harmonic mixer and a controller, the Harmonic mixer other than the output signal of the The signal of a reference oscillator can be fed to the oscillator whose frequency is an integer fraction, preferably a quarter, the oscillator frequency corresponds.

Another configuration of this training enables that the oscillator - also called local oscillator - subsequent circuits largely for the lower Frequency of the local oscillator can be designed that the supply of the output signal of the oscillator to Antenna element via a driver and an as Frequency doubler harmonic amplifier he follows.  

In an advantageous embodiment of the invention provided that the signal supplied to the antenna element and the amplified received signal one Fundamental mixer can be supplied at the output Intermediate frequency signal can be removed.

Unless a local oscillator with a lower frequency can be used instead of this training too be provided that the oscillator signal and the amplified received signal can be fed to a harmonic mixer, an intermediate frequency signal can be taken from its output. The use of harmonic mixers as reception mixers allows the supply at 38.25 GHz with a sufficiently high Level, causing a DC bias of the mixer diodes not applicable. Low-noise mixer with approximately 6 dB Insertion loss can thus be implemented.

An advantageous embodiment of this training sees before that the oscillator signal the antenna element and the Harmonic mixer can be fed via a Wilkinson divider is. Through or with several antenna elements multiple Wilkinson dividers will be a good decoupling both of the channels with each other as well as the feeding of the Receive mixer achieved by the local oscillator.

To achieve a sufficiently large sensor angle and Direction detection is common with distance sensors multiple antennas provided. This is with a Embodiment of the device according to the invention realizes that the output signal of the oscillator several, preferably three, antenna elements over one Power divider, via one driver and one each as Frequency doubler harmonic amplifier is feedable.  

In another advantageous embodiment of the Invention, a larger angle is detected by three Antenna elements are provided, two of which are outer Antenna elements are loaded with signals to be sent and that signals received by all antenna elements One mixer each can be fed from its outputs Intermediate frequency signals can be removed.

Embodiments of the invention are in the drawing represented with several figures and in the following Description explained in more detail. It shows:

Fig. 1 shows a first embodiment of a device according to the invention,

Fig. 2 shows a second embodiment,

Fig. 3 to Fig. 5, various embodiments for the supply and removal of antenna signals,

Fig. 6 shows an embodiment of a harmonic mixer,

Fig. 7 is a partially illustrated third embodiment, in which only the two outer are three antennas used for transmission,

Fig. 8 detail of a fourth embodiment,

Fig. 9 is also detail of a fifth embodiment,

Fig. 10 shows an embodiment of a harmonic amplifier,

Fig. 11 for several embodiments of the inventive device usable antenna elements and

Fig. 12, several examples of connecting lines to one antenna element.

Identical parts are given the same reference symbols in the figures Mistake. Components framed in dashed lines in the figures are in a monolithic microwave circuit (MMIC) realized while the rest of the components Cost reasons or due to high quality requirements (for example in the case of the dielectric resonator or the patch antennas) in MIC technology (Microwave Integrated Circuit) are arranged on a surrounding substrate, just like a metallic subcarrier is not shown is. Both MMICs and the MIC are mounted on this.

Low-noise frequency generation takes place in a voltage-controlled 38.25 GHz oscillator (DRVCO) 1 , the dielectric resonator (DR) of which, including a varactor diode for frequency modulation and the necessary coupling loops, is arranged on the substrate, which is made of quartz, for example, and by means of RF-compatible connections ( for example so-called ribbon bonds) is connected to the active part of the oscillator within the monolithic microwave circuit.

The oscillator energy is decoupled via an isolating amplifier 2 and fed to a directional coupler 3 , from the coupling arm of which a part of the energy is decoupled into a harmonic mixer 4 . The harmonic mixer 4 is also connected to the output of a reference oscillator 5 , the passive resonator of which is also arranged on the substrate. The reference oscillator oscillates at a frequency of 9.5 GHz. The harmonic mixer 4 is therefore tuned to the 4th harmonic (n = 4). A circuit 6 connected to the output of the harmonic mixer 4 and a control amplifier 7 of the frequency control loop are implemented as ASIC in bipolar technology and mounted on the substrate, not shown. The modulation signal, preferably a triangular voltage, is fed to the control amplifier 7 .

The output arm of the directional coupler 3 opens into a triple power divider 8 , the arms of which feed three preamplifiers 9 , 9 ′, 9 ″. The outputs of the preamplifiers 9 , 9 ', 9 ''are each connected to a double Wilkinson divider 10 , 10 ', 10 '', consisting of two microstrip arms and a resistor. The upper output arms of the double Wilkinson divider are each connected to a driver amplifier 11 , 11 ', 11 ''. Three harmonic amplifiers 12 , 12 ', 12 ''generate the working frequency of 76.5 GHz from the basic frequency of the 38.25 GHz oscillator 1 by selective selection of the second harmonic. The output signals of the harmonic amplifiers 12 , 12 ', 12 ''are fed to the circularly polarized antenna elements (for example patch antennas) 13 which are arranged on the surrounding substrate in order to achieve good radiation due to its low dielectric constant.

In the case of patch antennas, a circular polarization of the emitted waves is achieved, for example, either by chamfering two opposite corners of the patch antennas 13 , 13 ', 13 ''according to FIG. 1 or by a slot of the patch antennas shown in the exemplary embodiment according to FIG. 2 23 , 23 ', 23 ''reached. These and two further exemplary embodiments for patch antennas are shown in FIGS. 11a to 11d. In the examples shown in FIGS . 11c and 11d, the circular polarization is achieved by indenting a square ( FIG. 11c) or round ( FIG. 11d) patch with lateral coupling. A microwave lens 18 is used to bundle the emitted and received waves.

The signals received are coupled out of the patch antennas orthogonally to the feed of the patch antennas and fed to three harmonic reception mixers 15 , 15 ', 15 ''via three low-noise amplifiers 14 , 14 ', 14 ''. Furthermore, the associated local oscillator signals are fed from the lower arms of the Wilkinson divider 10 , 10 ', 10 ''to the harmonic receiver mixers 15 , 15 ', 15 ''. The output signals of the harmonic reception mixers 15 , 15 ', 15 ''are amplified in an intermediate frequency amplifier 16 , 16 ', 16 '' and can be found in the outputs 17 , 17 ', 17 ''. The frequency responses of the intermediate frequency amplifiers take into account the radar distance law. The intermediate frequency amplifiers 16 , 16 ', 16 ''are also constructed as ASICs and mounted on the substrate.

The concentrated structure in MIC and MMIC technology allows a hermetic seal by a Ceramic substrate hood, the top (Superstrat) in a distance of about lambda / 4 above the patch antennas is arranged, resulting in an improved beam concentration on a common lens.

In contrast to the exemplary embodiment according to FIG. 1, fundamental wave mixers 25 , 25 ', 25 ''are provided in the exemplary embodiment according to FIG. 2, their supply with the local oscillator signal via directional couplers (branch line couplers) 19 , 19 ', 19 '' from the output signals of the harmonic amplifier 12 , 12 ', 12 ''. As already mentioned in connection with FIG. 1, in the exemplary embodiment according to FIG. 2 patch antennas 23 , 23 ', 23 ''are each provided with a slot for achieving the circular polarization. However, it is also possible in the exemplary embodiment according to FIG. 2 to use other antenna elements, for example those shown in FIG. 11. It is also possible to use dielectric resonator elements instead of the patches.

In the exemplary embodiment according to FIG. 2, the reference oscillator 26 oscillates at a frequency of 38 GHz. A fundamental wave mixer 24 (n = 1) is therefore used in the frequency control loop.

Fig. 3 shows an example for the supply and extraction of signals at an antenna element 23. The signals are generated by an oscillator 34 , which represents circuits 1 to 12 ( FIG. 2). The signal to be transmitted is fed from the oscillator 34 to the antenna 23 via the main line of a directional coupler 19 . The received signal is taken at right angles to it and fed to a fundamental wave mixer 25 which contains a directional coupler 19 which branches off from the signal to be transmitted. The intermediate frequency signal can be taken from an output 31 .

In the embodiment according to Fig. 4 3 is compared to FIG. Between the directional coupler 19 and the fundamental wave mixer 25, a bypass line 32 is provided so that the fundamental wave mixer 25 supplied signal contains a convenient for mixing phase position with respect to the received signal.

The exemplary embodiment according to FIG. 5 enables the signals to be transmitted to be fed from the oscillator 34 to two sides of the antenna 23 while the received signal is separated from the signal to be transmitted. This is done via a 3dB coupler 35 , which is designed such that it forwards the signal supplied by the oscillator 34 with 3 dB attenuation to the two connections of the antenna 23 . In order to achieve a 90 ° phase shift on the antenna, the line 36 emanating from the branch arm of the directional coupler 35 is made correspondingly longer. Furthermore, the 3dB coupler 35 enables the received signal to be extracted at 37 .

Fig. 6 shows an embodiment of a harmonic mixer having a ring line 41. The signal from the local oscillator is fed to an input 42 and reaches the ring line via a coupling capacitor 43 . The received signal is present at a further input 44 . Mixing diodes 47 , 48 are connected to the ring line via a line 45 , 46 , the lines 45 , 46 having stub lines 49 , 50 for adapting the characteristic impedance. At the connection point of the diodes 47 , 48 there is a relatively large area which forms a short circuit for the microwaves with the continuous ground coating running underneath the entire arrangement. The intermediate frequency signals can be taken from the plate 51 .

In the exemplary embodiment according to FIG. 7, the oscillator 1 and the associated control loop ( FIG. 2) are omitted for the sake of simplicity. The amplified oscillator signal is fed from node 61 to a first Wilkinson divider 62 , one output of which carries the signal to be transmitted and the other output of which carries the local oscillator signal for mixing with the received signals. A second Wilkinson divider 63 divides the signal to be transmitted for two drivers 11 , 11 ″, to each of which a harmonic amplifier 12 , 12 ″ is connected. Two antennas 23 , 23 ″ are fed with their output signals, while a central antenna 23 ′ is used only for reception. A harmonic mixer 15 , 15 ', 15 ''is connected to each of the antennas. The frequency of the local oscillator is fed to these mixers via a power divider 64 . The intermediate frequency signals can be taken from the harmonic mixers 15 , 15 ', 15 ''and outputs 17 , 17 ', 17 '' can be supplied via intermediate frequency amplifiers 16 , 16 ', 16 ''.

The stripline preferably have one Characteristic impedance of 50 Ω while the characteristic impedance of the ring lines of the Wilkinson divider is √2 times and the resistance in the Wilkinson divider is reel 100 Ω.

FIG. 8 shows an exemplary embodiment in which a Wilkinson divider 65 is first connected to the switching point 61 and two further Wilkinson dividers 66 , 67 are connected to this. The Wilkinson divider 66 and an output of the Wilkinson divider 67 each feed a driver 68 , 68 ', 68 ''to which the harmonic amplifiers 69 , 69 ', 69 '' are connected, which are already explained ( Fig. 8) Control antennas not shown. The signals taken from the lower output of the Wilkinson divider 67 are fed via a circuit 70, not shown, to reception mixers.

In the embodiment according to FIG. 9, a power divider 71 is provided after the circuit point 61 with three outputs, two of which serve to feed two antennas 72 , 72 ″. For this purpose, the outputs of the power divider 71 are each via an amplifier 73 , 73 ″, a driver 74 , 74 ″, a harmonic amplifier 75 , 75 ″ and a ring coupler 76 , 76 ″ with the antennas 72 , 72 ′ connected. The ring couplers 76 , 76 ″ are also called rat race couplers. Due to the distribution of the connections on the circumference of the ring, different transit times are achieved from connection to connection, which lead to cancellation or to a summation of the signals circulating in both directions around the ring. Such a rat-race coupler is used in the exemplary embodiment according to FIG. 9 as harmonic mixer 77 , 77 ', 77 ''and is via diodes 78 , 78 ''with a supply voltage U _V and via diodes 78 ', 79 , 79 'and 79 ''each connected to an open lambda / 4 line 80 as an HF short circuit.

The signals to be amplified and doubled in frequency are fed to the harmonic amplifier according to FIG. 10 via an input 81 . An associated ground connection 82 is connected to a continuous conductive coating, which is not shown in FIG. 10, on another substrate level. At 83 , a gate bias can be supplied which, together with the signal to be amplified, can be supplied to the gate electrodes of two field effect transistors 85 , 86 via lines 84 , which are used for impedance matching and power division. Connections 87 to 90 of the source electrodes are also plated through to the ground electrode.

The gate electrodes 91 , 92 are constructed in the form of strips, for example with four strips each having a width of 100 μm. The drain electrodes of the field effect transistors 85 , 86 are connected via a network 93 to form the second harmonic, to combine the output signals of both field effect transistors and to convert impedance to an output 94 and to a connection 95 for supplying the drain voltage. The network has ground connections 96 , 97 at suitable points.

FIGS. 12a to 12c show various forms of 3 dB couplers 101, 102, 103 for connecting the antenna elements 104, 105 with outputs and inputs 106, 107.

While in the case of FIGS. 12a and 12b the line routing is symmetrical, in the asymmetrical construction according to FIG. 12c a length difference of the lines to the antenna element 104 is required which corresponds to an integral multiple of the wavelength.

Claims (16)

1. Device for transmitting and receiving radar waves, in particular for a distance sensor, wherein signals to be transmitted can be supplied to at least one antenna element and received signals can be extracted, characterized in that the antenna elements ( 13 , 13 ', 13 '', 23 , 23 ', 23 '') are designed to transmit circularly polarized radar waves and that the signals to be transmitted are fed to at least one side of the antenna element ( 13 , 13 ', 13 '', 23 , 23 ', 23 '') so that they are in are emitted at a first polarization level, and that the received signals are tapped by the antenna element ( 13 , 13 ', 13 '', 23 , 23 ', 23 '') at a second polarization level which is orthogonal to the first polarization level. 2. Device according to claim 1, characterized in that the antenna element ( 13 , 13 ', 13 '', 23 , 23 ', 23 '') is substantially square and that the supply and removal of the signals at least at two polarization-orthogonal Points. 3. Device according to claim 2, characterized in that circular polarization by two diagonally opposite bevels is effected.   4. Device according to claim 2, characterized in that the circular polarization by a diagonal extending slot is effected. 5. Device according to one of the preceding claims, characterized in that a further supply of to sending signals from the direction of the received signals he follows. 6. Device according to claim 5, characterized in that two connections of a 3dB coupler (branch line coupler, rat-race coupler) ( 35 ) are connected to the antenna element ( 23 ) in such a way that the signals to be transmitted at the one side of the antenna element ( 23 ) is 90 ° out of phase with respect to the other side, so that the received signals can be taken from a third connection of the 3dB coupler ( 35 ) and that the signals to be transmitted can be fed to a fourth connection. 7. Device according to one of claims 1 to 4, characterized in that a directional coupler ( 19 ) is connected to the feed of the signals to be sent to the antenna element ( 23 ) and that a coupling arm of the directional coupler ( 19 ) with an input of a mixer ( 25th ) is connected, the other input of which the received signals can be fed and an intermediate frequency signal can be taken from the output ( 31 ). 8. Device according to claim 7, characterized in that a detour line ( 32 ) is inserted between the coupling arm and the input of the mixer ( 25 ). 9. Device according to one of the preceding claims, characterized in that a controllable oscillator ( 1 ) is provided for generating the signals to be transmitted, the frequency of which can be modulated with a supplied modulation signal via a frequency control loop ( 3 , 4 , 6 , 7 ) and the latter Output signal via a frequency doubler ( 12 , 12 ', 12 '') which can be fed to at least one antenna element ( 13 , 13 ', 13 '', 23 , 23 ', 23 ''). 10. The device according to claim 9, characterized in that the frequency control loop comprises a harmonic mixer ( 4 ) and a controller ( 7 ), wherein the harmonic mixer ( 4 ) in addition to the output signal of the oscillator ( 1 ), the signal of a reference oscillator ( 5 ) can be supplied, the frequency of which corresponds to an integer fraction, preferably a quarter, of the oscillator frequency. 11. Device according to one of the preceding claims, characterized in that the supply of the output signal of the oscillator ( 1 ) to the antenna element ( 13 , 13 ', 13 '', 23 , 23 ', 23 '') via a driver ( 11 , 11th ', 11 '') and a harmonic amplifier ( 12 , 12 ', 12 '') acting as a frequency doubler. 12. Device according to one of the preceding claims, characterized in that the antenna elements ( 23 , 23 ', 23 '') fed signal and the amplified received signal of a fundamental wave mixer ( 25 , 25 ', 25 '') can be fed to the latter Output an intermediate frequency signal can be removed. 13. Device according to one of claims 1 to 11, characterized in that the oscillator signal and the amplified received signal a harmonic mixer ( 15 , 15 ', 15 '') can be fed, at the output of an intermediate frequency signal can be removed. 14. Device according to claim 13, characterized in that the oscillator signal, the antenna elements ( 13 , 13 ', 13 '') and the harmonic mixer ( 15 , 15 ', 15 '') via a Wilkinson divider ( 10 , 10 ' , 10 '') can be fed. 15. Device according to one of the preceding claims, characterized in that the output signal of the oscillator ( 1 ) several, preferably three, antenna elements ( 13 , 13 ', 13 '', 23 , 23 ', 23 '') via a power divider ( 8 , 8 '), can be fed via one driver ( 11 , 11 ', 11 '') and one harmonic amplifier ( 12 , 12 ', 12 '') acting as a frequency doubler. 16. Device according to one of claims 1 to 11, characterized in that three antenna elements ( 23 , 23 ', 23 '') are provided, of which two outer antenna elements ( 23 , 23 '') are acted upon with signals to be transmitted, and that signals received by all antenna elements ( 23 , 23 ', 23 '') can each be fed to a mixer ( 15 , 15 ', 15 '') from whose outputs intermediate frequency signals can be taken.