DE102015219612A1 - System architecture for a MIMO level radar - Google Patents

Abstract

FMCW level radar for detecting the topology of the surface of a bulk material, where each transmitter and each receiver has its own phase locked loop. All phase-locked loops are controlled by a central reference clock. This makes it possible in a simple and cost-effective manner to increase the number of transmitting and / or receiving channels.

Description

Field of the invention

The invention relates to the three-dimensional level measurement with radar. In particular, the invention relates to an FMCW level radar for detecting the topology of the surface of a bulk material and to a method for detecting the topology of the surface of a bulk material.

Technical background

In the field of three-dimensional level measurement with radar, completely new application goals arise. So far, only a rough measurement of the current filling level could be determined in bulk material measurements, so opens in the three-dimensional level measurement, the possibility of detecting the volume and / or mass of the bulk material contained in a container.

To record the topology of the bulk material surface level radars are used, which can scan the bulk material surface. The surface topology of the bulk material can then be calculated from the transmission signals reflected from the various regions of the bulk material surface.

Scanning of the bulk material surface may be done mechanically by adjusting the main emission direction of the antenna or electronically using digital beamforming techniques. In the latter case, the fill level measuring device has an antenna consisting of a plurality of transmitting and / or receiving devices and a matching evaluation unit. Due to the large number of channels, these devices are expensive to manufacture.

Summary of the invention

It is an object of the invention to provide an FMCW level radar for detecting the topology of the surface of a bulk material which has a simple yet reliable and flexible system architecture.

This object is solved by the subject matters of the independent claims. Further developments of the invention will become apparent from the dependent claims and the description below.

A first aspect of the invention relates to an FMCW (Frequency Modulated Continuous Wave) level radar, which operates according to the frequency-modulated continuous wave radar method and is designed to detect the topology of the surface of the bulk material.

The filling level radar has a transmitting device and a receiving device. The transmitting device contains a first phase locked loop (PLL: Phase Locked Loop), wherein the transmitting device is designed to emit a transmission signal in the direction of the surface of the bulk material. The receiving device has a second phase-locked loop and is used to receive a received signal. The received signal is the transmission signal reflected on the surface of the bulk material.

In addition, the receiving means is for mixing the received signal with a local oscillator signal generated by the second phase locked loop to produce an intermediate frequency signal. A central reference clock is provided, which is designed to provide a clock signal to all phase locked loops of both the transmitting device (s) and the receiving device (s).

In particular, the transmitting device and / or the receiving device can have additional phase locked loops which generate corresponding transmission signals or local oscillator signals for generating the intermediate frequency signals.

The filling level radar therefore has a plurality of transmitters and receivers, wherein each transmitting device and each receiving device is each assigned its own phase locked loop. However, the FMCW level radar, for example, has only one central reference clock, which gives the clock signal to all phase locked loops.

Compared to the provision of a single phase-locked loop whose signal is split among several transmitters, arranging one phase locked loop per transmitter in combination with a central reference clock is advantageous since it is technically less demanding to divide a reference clock signal among the different phase locked loops. as the signal of a single phase locked loop to divide multiple transmitters. One reason for this is that the frequency of the clock signal is significantly lower than the frequency of the signal generated by the phase locked loop.

According to one embodiment of the invention, the first phase-locked loop serves to generate a first local oscillator signal in the form of a frequency ramp, so that the frequency of the local oscillator signal increases over time. The transmitted transmission signal is at least substantially this local oscillator signal. For example, the LO signal in the transmitter can be amplified or frequency multiplied. In addition, it can be provided that the frequency of the LO signal also decreases over time.

According to a further embodiment of the invention, the second local oscillator signal used to generate the intermediate frequency signal is also a signal in the form of a frequency ramp, so that the frequency of this local oscillator signal increases over time.

According to a further embodiment of the invention, the fill level radar has a third phase-locked loop, which is designed to generate a further local oscillator signal in the form of a frequency ramp, so that the frequency of the further local oscillator signal increases over time. A further transmitting device or receiving device is provided which has this third phase locked loop. The transmitting device then uses the further local oscillator signal as the transmission signal or the receiving device uses the further local oscillator signal for generating an intermediate frequency signal.

As already described above, the fill level radar can have a multiplicity of transmitting devices (each provided with its own phase locked loop) and / or receiving devices (likewise each provided with its own phase locked loop). It should be noted, however, that it can also be provided that in each case a transmitting device and a receiving device share a phase locked loop. For example, in this case, transmitting device and receiving device are integrated on one and the same chip, and the chip can, depending on the control, perform the function of the transmitting device or of the receiving device. Also, the chip may be designed to simultaneously perform the function of the transmitting device and the receiving device.

According to a further embodiment of the invention, a central control unit is provided, which is designed to provide a trigger signal to a plurality or even to all phase-locked loops for starting the respective frequency ramp.

According to a further embodiment of the invention, in each case a transmitting device and a receiving device are integrated in one unit, which is, for example, a chip, wherein each of these units is in each case associated with only one phase-locked loop. It may also be provided that a plurality of transmitting devices and a plurality of receiving devices are accommodated in a chip.

As a result, the flexibility of the arrangement can be increased, since each chip can take over both transmit and receive function. It can thus be provided that the transmitter and receiver are accommodated in a chip, which can then also be operated simultaneously with an LO signal. It is also possible to operate either only the transmitter in the chip or only the receiver in the chip.

According to a further embodiment of the invention, the shape of the local oscillator signal of the first phase locked loop corresponds to the shape of the local oscillator signal of the second phase locked loop. A further aspect of the invention relates to a method for detecting the topology of the surface of a bulk material, wherein a clock signal is provided to a plurality of phase locked loops by a central reference clock. Subsequently, a transmission signal generated by a first phase-locked loop is emitted in the direction of the surface of the bulk material. There is then a reflection of the signal at the bulk material surface and receiving a corresponding received signal, which is the reflected on the surface of the bulk material transmission signal. Thereafter, the receive signal is mixed with a local oscillator signal generated by a second phase locked loop to produce an intermediate frequency signal. This intermediate frequency signal is then evaluated at the evaluation unit (together with the intermediate frequency signals generated by the other receiving units) in order to generate information about the topology of the bulk material surface.

Hereinafter, embodiments of the invention will be described. If the same reference numbers are used in the following figures, these designate the same or similar elements. However, identical or similar elements can also be designated by different reference symbols.

Brief description of the figures

1 shows an FMCW level radar for detecting the topology of the surface of a bulk material according to an embodiment of the invention.

2 shows a system architecture of a level radar for detecting the topology of the surface of a bulk material.

3 shows a system architecture of a level radar for detecting the topology of the surface of a bulk material according to a first embodiment of the invention.

4 shows a system architecture of a level radar for detecting the topology of Surface of a bulk material according to a second embodiment of the invention.

5 shows a system architecture of a level radar for detecting the topology of the surface of a bulk material according to a third embodiment of the invention.

6 shows a system architecture of a level radar for detecting the topology of the surface of a bulk material according to a fourth embodiment of the invention.

7 shows a system architecture of a level radar for detecting the topology of the surface of a bulk material according to a fifth embodiment of the invention.

8th shows a flowchart of a method according to an embodiment of the invention.

Detailed description of embodiments

The illustrations in the figures are schematic and not to scale.

1 shows an FMCW level radar for detecting the topology of the surface of a bulk material or other filling material. Such a Radarmessgerät can also be used to measure the level of liquids, which can be particularly useful when using a stirrer.

The level radar gauge 105 is capable of echo signals or echo curves from different angular ranges 101 . 102 . 103 capture. For each detected echo curve, the distance to the respective point of the surface of the bulk material 104 determined. By numerically integrating these distance values and postulating a flat surface 106 (eg container bottom) below the bulk material, the volume of the bulk material heap 107 be determined. If the density is known, the mass of bulk material can still be calculated.

The level gauge 105 has an antenna mount 108 for fixing an antenna 109 on. In this antenna, the above and described below transmitting and receiving devices and the remaining electronics can be accommodated.

Depending on the configuration of the level measuring device, the antenna holder 108 a mechanical adjustment of the main radiation direction of the antenna, for example by turning 110 or by tilting. Alternatively or additionally, methods of digital beam forming can be used. The level gauge has for this purpose the multiple transmitting and / or receiving devices having antenna 109 as well as a suitable evaluation unit 111 , which, for example, in the housing of the level gauge 105 located.

Various radar methods can be used. Frequently, the frequency-modulated continuous wave method is used. In this context we speak of FMCW level radars. In this case, a phase-locked loop generates a frequency ramp which is transmitted via the antenna. This signal is called a local oscillator (LO) signal. The reflected received signal is mixed with the transmission signal, wherein the frequency of the intermediate frequency signal thus generated in a linear relationship with the distance of the reflector, so for example, the bulk material surface is.

The methods of digital beamforming require a large number of such radar circuits in one device and can be implemented with different system architectures. A distinction must be made between systems with one transmitter or a transmitting device and several receivers or receiving devices (SIMO), systems with several transmitters and one receiver (Multiple Input Single Output, MISO) and systems with several transmitters and multiple receivers ( Multiple Input Multiple Output, MIMO).

2 shows a system architecture of an FMCW level radar for detecting the topology of the surface of a bulk material with multiple transmit and receive channels. For multi-channel systems, the transmitting and receiving devices require 204 . 205 . 206 . 207 a common LO signal to receive the transmitted electromagnetic waves again. This high-frequency LO signal is transmitted through a network, for example 202 of resistive power dividers 201 or power couplers on the number of desired transmitters and receivers 204 . 205 . 206 . 207 divided and comes from a PLL 203 , The resistive power dividers are, for example, Wilkinson Divider.

This type of distribution of high-frequency signals of the PLL 203 can be very lossy and thus can not be repeated as often as you like. Also, this type of power sharing is sensitive to mechanical tolerances and the structures of the tracks as well as the bandwidth used in the system.

3 shows the system architecture of a level radar according to an embodiment of the Invention. It is a MISO system architecture with a single receiver 310 ,

A fundamental aspect of the invention is the fact that each transmitter 304 . 306 . 308 and every recipient 310 a PLL 303 . 305 . 307 . 309 is assigned, which supplies the corresponding transmitter or receiver with a ramp-like transmission signal. As already explained above, each transmitter can also be combined with a receiver and manufactured as an integrated component. In this case, the transmitter / receiver unit is assigned exactly one PLL.

There are four PLLs 303 . 305 . 307 . 309 intended. The signal output of each PLL is connected to exactly one transmitter or receiver. The combination of PLL and transmitter or receiver forms the above-mentioned transmitting device 301 or receiving device 302 from, these devices may also have other elements. In the case of the receiving device 302 in particular, the further elements are an intermediate frequency amplifier 311 to the output of the receiver 310 connected, a subsequent analog / digital converter 312 and a subsequent signal processing device 313 ,

Each transmitter 304 . 306 . 308 may have a transmission amplifier and possibly a frequency multiplier. The recipient 310 may have a LNA (Low Noise Amplifier), a mixer and possibly also a frequency multiplier.

Each transmitter and each receiver is thus connected to the signal output of its own PLL, which generates the LO signal separately for each transceiver.

However, the individual PLLs are supplied with the same system clock, which consists of a single reference 314 , For example, a quartz oscillator, is derived. This clock signal can be executed by a multiple lower frequency than the LO signal. This has the advantage that no high-frequency effects have to be taken into account for splitting the signals. Thus, mechanical tolerances and the structures of the tracks play a minor role. The system bandwidth used, on the other hand, does not matter because only a pure clock signal is distributed. This reference 314 can also be called a reference clock.

In addition, is a central control unit 315 provided, for example in the form of a microprocessor, a DSP or an FPGA, which to each PLL 303 . 305 . 307 . 309 is connected, and this by means of a trigger signal gives the command to generate the frequency ramp and thus start a measurement.

Each PLL thus generates a separate frequency ramp which is identical to the frequency ramps of the other PLLs. By the transmitter, this frequency ramp is sent and mixed in the receivers, the received signal with this frequency ramp, so as to obtain an intermediate frequency signal. Additional phase errors caused by this system architecture can be eliminated by calibration.

4 shows a system architecture of a FMCW level radar according to another embodiment of the invention. In this embodiment, a transmitter 304 with its own PLL 303 and three recipients 402 . 407 . 310 with appropriate own PLLs 401 . 406 . 309 intended. Of course, additional receivers and corresponding PLLs may be provided, depending on how many receive channels are needed. Every receiver 402 is with its own IF amplifier 403 . 408 . 311 connected to an analog / digital converter 404 . 409 . 312 is connected, which in turn to a corresponding signal processing device 405 . 410 . 313 connected.

As in the previous and also in the following exemplary embodiments, a single one can be a reference clock 314 be provided, which provides a clock signal to all PLLs. Furthermore, a single control unit 315 be provided, which supplies all PLLs with control signals, for example, to trigger a measurement.

In the embodiment of the 4 is therefore a so-called SIMO system architecture.

5 shows another embodiment of a system architecture for an FMCW level radar according to an embodiment of the invention. This is a MIMO system architecture with a large number of transmitters 304 . 306 and a variety of recipients 310 . 407 ,

According to a further embodiment, a transmitter and a receiver may each be integrated in one unit. This unit uses the same LO signal for sending and receiving and can be understood as a front end for a single level gauge, as shown in the 6 is shown. The combined transmitter and receiver units are denoted by the reference numerals 601 . 602 . 603 . 604 designated.

Thus, the transmitting device and the receiving device are the same device (see, for example, device 601 ). For example, such a unit 601 be implemented by a monolithic microwave integrated circuit (MMIC). The transmitters and receivers of these radar chips can be selected by the control unit 315 be turned on and off to form a suitable co-array can.

Every group 601 . 602 . 603 . 604 is then replaced by a PLL 303 . 305 . 307 . 309 fed to each other via the reference clock of the reference clock 314 are synchronized.

7 shows a further embodiment of a system architecture of a FMCW level radar. In this case, parts of the PLL, for example the voltage-controlled oscillator (Voltage-Controlled Oscillator, VCO) 703 , on the transmitter or receiver side 702 integrated. This allows different frequency ranges with the same PLL 303 be driven, since the VCO 703 is crucial for the frequency domain. For this, it is not necessary to exchange the LO signal between the two units, but the control voltage 704 and the feedback output signal 705 of the VCO 703 ,

The Indian 7 shown "VCO block" 702 corresponds to the transmitter 601 of the 6 ,

PLL 303 and VCO block 702 can be integrated on one chip or each on a separate chip.

In this and in all other embodiments, ten or more transmitting and / or receiving channels may be provided.

8th shows a flowchart of a method according to an embodiment of the invention. In step 801 a clock signal of a reference clock is provided to a plurality of phase locked loops, which in step 802 causes each phase-locked loop to generate a ramp-type transmit signal, which in step 803 transmitted by a transmitter. In step 804 This transmission signal is, after it has been reflected on a bulk material surface, received by a corresponding receiving device. The received signal is in step 805 mixed with a local oscillator signal generated by a second phase locked loop to produce an intermediate frequency signal.

The system architecture described above with regard to the simpler LO distribution network, in which almost any number of radar front ends can be parallelized, offers a significant advantage. Due to the high integrability of the individual system components of the PLL and the radar front end, additional PLL components do not cause any higher costs.

In addition, it should be noted that "comprising" and "having" does not exclude other elements or steps, and "a" or "an" does not exclude a plurality. It should also be appreciated that features or steps described with reference to any of the above embodiments may also be used in combination with other features or steps of other embodiments described above. Reference signs in the claims are not to be considered as limitations.

Claims (8)

FMCW level radar for detecting the topology of the surface of a bulk material, comprising: a transmitting device ( 301 ) with a first phase locked loop ( 303 ), wherein the transmitting device is designed to emit a transmission signal in the direction of the surface of the bulk material; a receiving device ( 302 ) with a second phase locked loop ( 309 wherein the receiving means is adapted to receive a receive signal which is the transmit signal reflected at the surface of the bulk material and to mix the receive signal with a local oscillator signal generated by the second phase locked loop to produce an intermediate frequency signal; a central reference clock ( 314 ) for providing a clock signal to all phase locked loops ( 303 . 309 ) is executed. Filling level radar according to claim 1, wherein the first phase locked loop ( 303 ) for generating a local oscillator signal in the form of a frequency ramp, so that the frequency of the local oscillator signal increases over time; and wherein the transmission signal is substantially the local oscillator signal. Level radar according to claim 1 or 2, wherein the second phase locked loop ( 309 ) for generating the local oscillator signal in the form of a frequency ramp, so that the frequency of the local oscillator signal increases over time. Filling level radar according to one of the preceding claims, further comprising: a further transmitting device ( 305 . 306 ) or receiving device ( 406 . 407 ) with a third phase locked loop ( 305 . 406 ); wherein the third phase-locked loop is designed to generate a further local oscillator signal in the form of a frequency ramp so that the frequency of the further local oscillator signal increases over time; wherein the further transmitting device for using the further local oscillator signal as a transmission signal or the further receiving device for using the further local oscillator signal for generating an intermediate frequency signal is executed. Level radar according to one of the preceding claims, a central control unit ( 315 ) for providing a trigger signal to all phase locked loops ( 303 . 309 ) is executed to start generating the corresponding frequency ramp. Level radar according to one of the preceding claims, wherein in each case one or more transmitting devices ( 301 ) and one or more receiving devices ( 302 ) in one unit ( 601 ), which only has one phase locked loop ( 303 ) assigned. Level radar according to one of claims 2 to 6, wherein the shape of the local oscillator signal of the first phase locked loop ( 303 ) the shape of the local oscillator signal of the second phase locked loop ( 309 ) corresponds. Method for detecting the topology of the surface of a bulk material, comprising the steps of: providing a clock signal to a plurality of phase locked loops ( 303 . 309 ) by a central reference clock ( 314 ); Sending out a signal through a first phase locked loop ( 303 ) generated transmission signal in the direction of the surface of the bulk material; Receiving a received signal which is the transmitted signal reflected on the surface of the bulk material; Mixing the received signal with one of a second phase locked loop ( 309 ) generate local oscillator signal to generate an intermediate frequency signal.

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