Radar transceiver arrangement

Abstract

The invention relates to a radar transceiver arrangement for generating modulated multi-tone chirp signals, characterised by a transmission device with at least two digital chirp generators (110, 120; 310, 320, 330), which each generate a complex, digital chirp signal with configurable parameters, and at least two transmission paths, for which each of the chirp generators (110, 120; 310, 320, 330) generates a signal by combining the chirp signals, which is converted to analogue via a digital-analogue converter (150, 160) for the transmission of radar signals via a transmission antenna (TX1, TX2).

Description

[0001] Description

[0002] title

[0003] Radar transceiver

[0004] The invention relates to a radar transceiver arrangement for generating modulated multi-tone chirp signals.

[0005] State of the art

[0006] Such radar transceiver arrangements are used, for example, in vehicles to implement driver assistance systems and driving safety systems.

[0007] The use of a chirp sequence modulation method in combination with a MIMO (multiple-input multiple-output) radar system is also known from the prior art. A chirp signal is transmitted via multiple transmit antennas, and the reflection is received via multiple receive antennas. To enable multiplexing of multiple transmit antennas, various multiplexing methods are used, such as TDM (time division multiplexing), FDM (frequency division multiplexing), or DDM (Doppler division multiplexing). Furthermore, radar sensors exist that enable transmit beamsteering, in which the same modulation signal is transmitted from multiple transmitters, but with different phase and amplitude.

[0008] The necessary chirp signals are typically generated using analog components, such as voltage-controlled oscillators (VCOs). To enable modulations such as DDM or TX beam steering, analog phase shifters are used to modulate the phase of the analog chirp signals. The reflections are mixed with the transmitted chirp signal in analog form, low-pass filtered, and then converted from analog to digital. The digitized signals are then further processed using digital signal processing techniques.

[0009] Disclosure of the invention

[0010] The radar transceiver arrangement for generating modulated multi-tone chirp signals, which has a transmitting device with at least two digital chirp generators, each generating a complex, digital chirp signal with configurable parameters, and which has at least two transmitting paths for which each of the chirp generators generates a signal by combining the chirp signals, which signal is converted into analogue via a digital-to-analogue converter for transmitting radar signals by a transmitting antenna, enables an efficient and flexibly configurable implementation of a chirp sequence radar, which enables a frequency multiplex of differently modulated chirp signals in an M1 MO system.

[0011] An essential aspect of the invention is the realization of a hardware architecture for the efficient digital generation of modulated multi-tone chirp signals as well as an associated hardware architecture for an efficient digital demodulation of the reflected chirp signals.

[0012] Another key aspect of the invention is that the chirp signals are processed digitally. This applies, firstly, to the purely digital generation of the modulation. The digital signal is then converted via a digital-to-analog converter and converted to the radar frequency band in an I / Q mixer. The proportion of cost-intensive and tolerance-prone analog components is kept to a minimum, while simultaneously maximizing modulation flexibility, which goes beyond conventional signal generation methods. This is particularly advantageous for multi-tone signals, where an analog implementation would be very complex, whereas a digital implementation allows for effective utilization of the high number of degrees of freedom.

[0013] According to one aspect of the invention, a receiving device with at least two receiving antennas is provided for receiving at least two chirp signals reflected from an object, each of which is fed to an analog-to-digital converter and digitally mixed with at least one of the transmitted chirp signals in at least one receive path assigned to each receiving antenna by means of a complex multiplier. In accordance with the procedure for signal transmission, the received reflected chirp signals are digitally mixed with the transmitted chirp signals in the complex baseband and further processed only after the analog-to-digital conversion. Compared to analog mixing, this also reduces the complexity in the analog part of the receive path for multi-tone signals, since even with multiple tones, only one analog quadrature mixer is required.

[0014] The configurable parameters include at least the start phase, the start frequency, the ramp steepness, the ramp length.

[0015] The local oscillator required for mixing into the transmission frequency band is typically operated at a fixed frequency or in a few discrete frequency steps (typically 2 to 16). This makes it possible to increase the overall bandwidth of the radar transmission or, for example, to avoid interference. However, the frequency of the local oscillator is not changed during the transmission of a chirp.

[0016] According to one aspect of the invention, the chirp signals are each weighted with an individual complex parameter before combining the chirp signals in the transmission paths. The configurable parameters can include this individual complex parameter.

[0017] According to one aspect of the invention, the mixing of the at least two reflected chirp signals with the transmitted chirp signals takes place after inverting the frequency.

[0018] A further aspect of the invention provides low-pass filtering of the mixed signals and sampling rate reduction.

[0019] Instead of at least a second chirp generator, a complex sine wave generator and at least one additional mixer can also be provided. According to one aspect of the invention, the received chirp signals are separated in each receive path in a filter bank configured for this purpose.

[0020] Short description of the drawings

[0021] Embodiments of the invention are illustrated in the drawings and explained in more detail in the following description.

[0022] Fig. 1 shows a transmitting device according to the invention with at least two digital chirp generators.

[0023] Fig. 2 shows a receiving device according to the invention with at least two receiving antennas for receiving at least two chirp signals reflected from an object.

[0024] Fig. 3 shows the extension of a transmitting device according to the invention with three digital chirp generators.

[0025] Fig. 4 shows a cascade structure for generating multiple frequency-shifted chirp signals.

[0026] Fig. 5 shows the extension of a receiving device according to the invention for demodulating reflected radar signals with more than two tones.

[0027] Fig. 6 shows the separation of the individual tones of a multi-tone chirp signal using a “polyphase channelizer”.

[0028] Embodiments of the invention

[0029] Fig. 1 shows the basic form of a hardware architecture for generating modeled multi-tone chirp signals consisting of two tones. Two digital chirp generators 110, 120 are provided. These can independently generate a complex digital chirp signal with configurable parameters. These configurable parameters can be, for example, the start frequency, the start phase, the ramp steepness, or the ramp length. Each of these chirp signals can be independently configured for each transmitting antenna TX1 or TX2 of the radar with a complex parameter a x , b xmultiplied, as shown by the multipliers 111, 112, 121, 122. For this purpose, a number of TX antennas multiplied by two complex multipliers are provided. In this way, two chirp signals with configurable amplitude and phase are obtained per transmitting antenna. Depending on the desired modulation, it is sufficient if the complex parameter is only changed from ramp to ramp (for example DDM or TX beamsteering) or, for other modulation types, e.g. Code Division Multiplex CDM, it can also be changed during the transmission of the ramp if designed accordingly. In principle, all modulation types based on modulating the amplitude and / or phase of the chirp signal can be implemented. For each of the transmitting antennas TX1, TX2, the modulated chirp signals are added together. Adders 130, 140 are provided for this purpose. In this way, an individually modulated multi-tone chirp signal is obtained for each transmitting antenna TX1, TX2.These digital multi-tone chirp signals are converted into analog signals by digital-to-analog converters 150, 160. For each of the transmitting antennas TX1, TX2, two analog signals exist, representing the in-phase (I) and quadrature (Q) components of the multi-tone chirp signal. These signals are converted to the desired radar frequency band using a quadrature mixer 155, 165, which uses a local oscillator 170, amplified by amplifiers 157, 167, and transmitted via the antennas TX1, TX2.

[0030] The receive path is shown in Fig. 2. In the receive path, the reflected analog radar signals received by antennas RX1, RX2 are amplified by amplifiers 201, 202 and converted to the complex baseband for each receive antenna RX1, RX2 using a quadrature mixer 210, 220. Mixing is performed using the local oscillator 270. These signals are then converted into digital signals by analog-to-digital converters 215, 225. The receive path of each receive antenna RX1, RX2 is then divided into two paths. Each of these paths contains a complex multiplier 232, 234 or 242, 244, which mixes the received signal with one of the chirp signals generated at the transmit end, but with a negated frequency. The negated frequency is achieved, for example, by inverting the sign of the imaginary part. These signals are then filtered through corresponding low-pass filters 252, 254 or 256.262, 264 are digitally low-pass filtered, and the sampling rate is reduced by decimators 272, 274, and 282, 284, respectively. This produces a separate signal for each receiving antenna RX1, RX2 and for each individual transmit tone, which can be further processed using conventional digital radar signal processing techniques.

[0031] An extension to more than two tones is shown in Fig. 3 and 5. In this case, the same elements are shown with the same reference numerals as in Fig. 1 and Fig. 2. In Fig. 3 and Fig. 5, the extension to three tones is shown. In Fig. 3, three digital chirp generators 310, 320, 330 are provided for this purpose, with the number of multipliers being increased accordingly to three, 311, 321, 331 and 312, 322, 332 respectively. For each transmitting antenna TX1, TX2, these three modulated chirp signals are added in adders 130, 140 and further processing takes place as described in connection with Fig. 1.

[0032] The reception path essentially corresponds to that shown in Fig. 2, but here three complex multipliers 532, 534, 536 and 542, 544, 546 are provided, and low-pass filtering is performed in three low-pass filters 552, 554, 556 and 562, 564, 566. Following the low-pass filters are three decimators 582, 584, 586 and 572, 574, 576 to reduce the sampling rate.

[0033] If a large number of tones are to be generated, it may be advisable to reduce the hardware expenditure and use a cascade structure, as shown by way of example in Fig. 4. Here, only one chirp signal is generated by a digital chirp generator 410, and a complex sine tone with a constant frequency is generated using a numerically controlled oscillator (NCO) 405. These signals are digitally mixed with one another several times using multipliers 420, 421, 422, 423, 424, 425, 426, and 427. This multiple digital mixing is carried out in order to obtain several chirp signals that are equidistantly shifted in frequency and have the same bandwidth and ramp steepness.Regardless of the number of tones, in this case only one digital chirp generator 410 and one complex sine tone generator (numerically controlled oscillator - NCO) 405 are required, although the number of required multipliers 420 to 427 increases with the number of tones. Further signal processing is performed as described in connection with Fig. 1.

[0034] On the receive side, schematically shown in Fig. 5, a larger number of tones can be processed—as explained above—by replicating the path with mixers and low-pass filters corresponding to the number of tones. Each path is then mixed with the respective tone to be separated.

[0035] As an alternative to the circuit shown in Fig. 5, the individual tones of a multi-tone chirp signal can be separated using so-called polyphase channelizers 650, 660, as schematically shown in Fig. 6, in which the same elements are designated by the same reference numerals as in Fig. 2, so that for their description, reference is made to the description of Fig. 2. In multipliers 630, 640, a sign reversal of the imaginary part is performed as described above, and the individual tones are separated in the aforementioned polyphase channelizers 650, 660.

Claims

Claims 1. Radar transceiver arrangement for generating modulated multi-tone chirp signals, characterized by a transmitting device with at least two digital chirp generators (110, 120; 310, 320, 330), each generating a complex, digital chirp signal with configurable parameters, and at least two transmission paths, for which each of the chirp generators (110, 120; 310, 320, 330) generates a signal by combining the chirp signals, which signal is converted into analogue via a digital-to-analogue converter (150, 160) for transmitting radar signals by a transmitting antenna (TX1, TX2).

2. Radar transceiver arrangement according to claim 1, characterized by a receiving device with at least two receiving antennas (RX1, RX2) for receiving at least two chirp signals reflected from an object, which are each fed to an analog-digital converter (215, 225) and are digitally mixed with at least one of the transmitted chirp signals in at least one receiving path assigned to each receiving antenna (RX1, RX2) by means of a complex multiplier.

3. Radar transceiver arrangement according to claim 1 or 2, characterized in that in the transmitting device and in the receiving device, the signals are converted between complex baseband and radar frequency band by a quadrature mixer (155, 165; 210, 220) and a local oscillator (170; 270).

4. Radar transceiver arrangement according to claim 1, characterized in that the configurable parameters include at least: the start phase, the start frequency, the ramp steepness, the ramp length.

5. Radar transceiver arrangement according to claim 1, characterized in that before combining the chirp signals in the transmission paths, these are each weighted with an individual complex parameter.

6. Radar transceiver arrangement according to claim 4 and 5, characterized in that the configurable parameters comprise the individual complex parameters.

7. Radar transceiver arrangement according to claim 2, characterized in that the mixing of the at least two reflected chirp signals with the transmitted chirp signals takes place after inverting the frequency.

8. Radar transceiver arrangement according to claim 2, characterized in that low-pass filters (252, 254, 262, 264; 552, 554, 556, 562, 564, 566) in which a low-pass filtering of the mixed signals takes place, and decimators (272, 274, 282, 284; 572, 574, 576, 582, 584, 586) in which a sampling rate reduction takes place are provided in the reception paths.

9. Radar transceiver arrangement according to claim 1, characterized in that instead of at least one second chirp generator, a complex sine tone generator (405) and at least one additional mixer (420, 423, 426) are provided.

10. Radar transceiver arrangement according to claim 2, characterized in that in each reception path a separation of the received chirp signals takes place in a filter bank (650,660) set up for this purpose.

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