Digital Modulation Radar Transmitter Module, System and Method

Abstract

The present invention discloses a digital modulation radar (DMR) transmitter module, comprising: a sequence generator configured to generate a repetitive digital sequence signal based on a relatively low-frequency clock signal; a mixer configured to combine the digital sequence signal with at least one phase-delayed copy of the digital sequence signal to provide a combined signal; and a modulator configured to modulate a relatively high-frequency carrier signal depending on the combined signal to provide a modulated signal. The present invention also discloses a corresponding system and method.

Description

Technical Field

[0001] The present disclosure relates to a Digital Modulated Radar (DMR), and more specifically, to a DMR transmitter module, a DMR system, and a method of generating a DMR signal. Background Art

[0002] In a conventional radar system, a pulsed signal is transmitted from a transceiver and a reflected signal is received at the transceiver. The reflected signal is analyzed by analyzing the time-of-flight and Doppler effects to provide information about the distance and velocity of the reflection source. The limitations of the dead time between pulses and differentiating multiple interfering signals can be addressed by using a Digital Modulated Radar (DMR). In a digital modulated radar, a carrier signal is modulated according to a digital signal, rather than transmitting a simple high-frequency carrier signal. The digital signal provides an identification code that can distinguish the reflection of the transmitted signal from interfering signals and introduces time-domain variations such that a dead time need not be included to determine the total time-of-flight of the transmitted and reflected signals.

[0003] However, modulating a carrier signal according to a digital signal introduces side lobes in the frequency domain. These side lobes can carry significant power and, in some regulatory environments, for example, for applications such as 77 GHz automotive radar, this may be undesirable or even unacceptable. There is a need to reduce the power or magnitude of these side lobes. Summary of the Invention

[0004] According to a first aspect of the present disclosure, there is provided a Digital Modulated Radar (DMR) transmitter module comprising: a sequence generator configured to generate a repetitive digital sequence signal based on a relatively low-frequency clock signal; a mixer configured to combine the digital sequence signal with at least one phase-delayed copy of the digital sequence signal to provide a combined signal; and a modulator configured to modulate a relatively high-frequency carrier signal depending on the combined signal to provide a modulated signal. Combining the original repetitive digital sequence signal changes the positioning of the side lobes associated with the transmitted modulated high-frequency signal and the power in the side lobes, and can reduce the power in any individual side lobe. There may be one, two, or more phase-delayed copies. The side lobes may be evenly separated in phase, or the side lobes may be irregularly spaced. Irregular phase spacing may further reduce the power in the side lobes.

[0005] In one or more embodiments, the DMR transmitter module further includes one or more phase delay circuits, each phase delay circuit being configured to receive the digital sequence signal as an input and provide a corresponding one of the at least one phase-delayed copy of the digital sequence signal to the mixer, the corresponding one of the at least one phase-delayed copy being phase-delayed by a respective predetermined phase shift.

[0006] In one or more other embodiments, the DMR transmitter module further includes one or more phase delay circuits, each phase delay circuit being configured to receive the clock signal as an input and output a corresponding copy of the clock signal that is phase-delayed by a corresponding predetermined phase shift; and one or more additional sequence generators, each additional sequence generator being configured to generate a digital sequence signal based on a corresponding one of the at least one phase-delayed copy of the clock signal to provide a corresponding phase-delayed copy of the digital sequence signal to the mixer. Such modules that apply phase delay to the clock signal may be easier to implement compared to those that apply phase delay to the digital sequence signal.

[0007] The modulator may be a phase shift keying (PSK) modulator, and the modulation signal is a PSK modulation signal. The PSK modulation signal may be a binary phase shift keying (BPSK) signal. Phase shift keying modulation signals, and specifically binary phase shift keying modulation signals, have been proven to be particularly effective for transmitting radar signals.

[0008] However, in one or more other embodiments, the modulator is an amplitude modulator and the modulation signal is an amplitude modulation signal, or the modulator is a frequency modulator and the modulation signal is a frequency modulation signal.

[0009] In one or more embodiments, the relatively high-frequency carrier signal is derived from a local oscillator, and one of the clock signals is derived from the local oscillator, or the local oscillator is derived from the clock signal. Generally, it is much easier to frequency multiply a clock signal operating, for example, between 500 MHz and 4 GHz to generate a higher relatively high-frequency carrier signal operating, for example, at 77 GHz or 140 GHz, rather than directly generating the relatively high-frequency signal.

[0010] According to another aspect of the present disclosure, a DMR system is provided that includes the DMR transmitter module as described above, and the DMR system further includes a receiver module, wherein the receiver module includes: a downconverter configured to downconvert the received signal to a reference frequency; a track-and-hold circuit; and an analog-to-digital converter (ADC) configured to digitize a portion of the downconverted received signal.

[0011] The receiver module may further include a cross-correlation unit configured to cross-correlate the portion of the downconverted received signal with the digital sequence signal.

[0012] According to yet another aspect, there is provided a method of generating a digitally modulated radar signal, the method comprising: generating a digital sequence, and a repeated digital sequence signal based on the digital sequence and a relatively low frequency clock signal; generating at least one phase-delayed copy of the digital sequence signal; combining the digital sequence signal with at least one phase-delayed copy of the digital sequence signal in a mixer to provide a combined signal; and modulating a relatively high frequency carrier signal depending on the combined signal to provide the digitally modulated radar signal.

[0013] In one or more embodiments, generating one of the at least one phase-delayed copies of the digital sequence signal comprises: receiving the repeated digital sequence signal in a respective phase-delay circuit; delaying the phase by a respective predetermined phase shift; and providing a respective one of the at least one phase-delayed copies of the digital sequence signal to the mixer.

[0014] In one embodiment or in other embodiments, generating one of the at least one phase-delayed copies of the digital sequence signal comprises: receiving the clock signal in a respective phase-delay circuit, delaying the phase by a respective predetermined phase shift, and outputting a phase-delayed copy of the clock signal; and generating a digital sequence signal based on the digital sequence and the phase-delayed copy of the clock signal to provide the one of the at least one phase-delayed copies of the digital sequence signal to the mixer.

[0015] These and other aspects of the invention will become apparent from the embodiments described hereinafter and will be elucidated with reference to the embodiments described hereinafter. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Embodiments will be described by way of example only, with reference to the drawings, in which

[0017] Figure 1 an example of a digital sequence is shown;

[0018] Figure 2 the spectrum of a digital signal for a 77 GHz automotive radar application is shown;

[0019] Figure 3a a repeated binary digital sequence signal with signal shaping according to one or more embodiments is shown;

[0020] Figure 3b a repeated 3-3 digital sequence signal with signal shaping according to one or more other embodiments is shown;

[0021] Figure 4 the spectrum of a carrier signal modulated by a combined signal is shown;

[0022] Figure 5Shows a reference frequency section of a module according to one or more embodiments.

[0023] Figure 6 Shows a reference frequency section of a module according to other embodiments;

[0024] Figure 7 Shows a DMR system according to one or more embodiments; and

[0025] Figure 8 Shows a MIMO DMR system according to one or more embodiments.

[0026] Figure 8 (Continued) Shows a MIMO DMR system according to Figure 8 thereof.

[0027] It should be noted that the drawings are illustrative and not necessarily drawn to scale. For clarity and convenience in the drawings, the relative sizes and proportions of the various parts of these drawings may be enlarged or reduced in size. In modified and different embodiments, the same reference numerals are generally used to refer to corresponding or similar features. Detailed Description

[0028] Figure 1 Shows an example of a digital sequence, such as those used for DMR. In this case, the example digital sequence shown: {0,1,0,1,0,0,1,1…} is binary, but those skilled in the art will understand that higher clusters or other forms of the sequence are possible, such that values other than 0 or 1 can be used. In a typical radar application, the digital sequence may include 2^12 or 4k bits; however, other sequence lengths may be used.

[0029] Apply the sequence to a clock to generate a digital sequence signal 120. The clock can run at a so-called reference frequency, which can typically be (but is not limited to) about 500 MHz to 4 GHz. At a clock frequency of 4 GHz, the 4k-bit sequence shown at 130 thus lasts for about 1 ms. Repeat the sequence to generate a repeated digital sequence signal 140.

[0030] As those skilled in the DMR art will be familiar, this repeated digital sequence signal 140 can be used to modulate a carrier signal to generate a radar transmit signal. The carrier signal has a frequency relatively higher than the reference frequency. In the case of automotive radar, regulatory authorities have allocated a frequency band centered at 77 GHz, and thus this frequency band is typically used. However, the present disclosure is not limited thereto: for example, in the automotive field as well, another frequency band of about 140 GHz is also considered available.

[0031] The repetitive digital sequence signal 140 is used to modulate a carrier signal. Most commonly, the modulation is phase modulation, but those skilled in the art will realize that other forms of modulation, such as amplitude modulation and frequency modulation, are equally applicable. In the case of phase modulation, also known as phase shift keying (PSK), binary phase shift keying (BPSK) is generated using, for example, the binary digital signal described above; in the case of multi-level signals or high combinations, alternative forms of phase shift keying, such as quaternary phase shift keying QPSK or n-QSPK, are equally applicable.

[0032] Similarly, as those skilled in the art will be familiar with, when viewed in the frequency domain, modulating a carrier signal by a digital signal generates side lobes. Figure 2 The spectrum 230 of the digital signal for a 77 GHz automotive radar application is shown. The figure shows the effective isotropic radiated power (EIRP) on the ordinate or y-axis 210 plotted against the bandwidth on the abscissa or x-axis. As expected, the power is highest at the carrier frequency, as shown by the main power spike 232. However, there is a significant amount of power in the side lobes, as shown by 234, 236, and 238, which are located at approximately 3 GHz, 5 GHz, and 7 GHz from the center frequency.

[0033] Figure 2 An example of a power mask 240 is also shown. The power mask shows the power limits that can be recommended or imposed by a regulatory body such as ETSI (European Telecommunications Standards Institute). As shown, the power mask can impose the requirement that the transmitted power outside a narrow bandwidth (e.g., ±2 GHz as shown) be limited to a relatively low level (e.g., at least 30 dB lower than the peak signal as shown). Imposing a spectrum mask generally aims to reduce adjacent channel interference by limiting excessive radiation at frequencies outside the required bandwidth. As can be seen from the figure, the side lobes of the DMR transmitted signal can exceed this limit.

[0034] It is known to attenuate these side lobes by using a band-pass filter that is tuned to allow the correct center frequency of the carrier, along with the necessary sidebands, to properly transmit the digital signal. The band-pass filter can be implemented using passive components; however, this may not be feasible in some applications where monolithic integration is desired or required.

[0035] An alternative solution is to implement the band-pass filter in the digital domain. This can be done by applying a finite impulse response (FIR) filter in the signal generation chain. However, to implement this, the signal must be generated by a high-speed digital-to-analog converter (DAC) that operates at a speed higher than the bit rate of the signal to be generated. This in turn requires space on the silicon chip to implement the DAC and the FIR filter, and requires a significant amount of processing power and effort to operate those IP blocks.

[0036] Figure 3aShows a repetitive digital sequence signal with signal shaping. The repetitive digital sequence signal 140 is the same as the repetitive digital sequence signal shown in Figure 1 This signal is combined with one or more copies of the signal. Three copies 310, 320, 330 are shown in this non-limiting example. The "decomposed" signal is shown at the top of the figure, and each signal is overlaid at the second part of the figure. As shown, the signals are copies of the original repetitive digital sequence signal that are phase-delayed or phase-shifted. That is, the signals are the same except for the fact that the clocks of the signals have a relative phase difference. In the example shown, and referring to the original repetitive digital sequence signal, for the first copy 310, the phase delay is 60°, for the second copy 320, the phase delay is 180°, and for the third copy 330, the phase delay is 240°.

[0037] The signals are then combined to provide a combined signal that can be plotted as an amplitude versus time in the third part of the figure, as shown at 340. The combination is performed in the case of binary signals such that the combined signal is "high" or "1" whenever any one or more of the individual signals is "high" or "1", and the combined signal is only "low" or "0" when all individual signals are "low" or "0". Thus, a single "0" bit in the original signal results in a much shorter "0" time in the combined signal, as shown at 342, and a single "1" bit in the original signal results in a longer "1" time in the combined signal, as shown at 344. It will be observed that in the case of another bit having the same parity after a bit (e.g., two "0"s as shown at 346), one of the bits is unaffected. In the case of two consecutive "0"s, this is the second bit. In the case of two consecutive "1"s, this will be the first bit that is unaffected.

[0038] Finally, the bottom part of the figure shows the signal 345 after smoothing. It should be understood that the "square wave" digital signal shown at the top of the figure is idealized. In any actual circuit, the instantaneous sharp transitions shown in the upper part of the figure between the high and low states do not occur, and the signal transitions are rounded. By including phase-delayed copies of the signal, the irregularity of the transition intervals is increased, and this effect is to smooth the transitions between the levels. This will increase the slope of the transitions and will round the square signal in such a way that the spectral components are reduced.

[0039] Figure 3aShows a repetitive digital sequence signal with signal shaping according to one or more other embodiments. The original three-level signal 360 is combined with phase-delayed copies, in this example, with 3 such copies 362, 364, and 368. In this particular non-limiting example, the phase delays are 60°, 180°, and 240° respectively. As shown by the idealized signal 370, the irregularity between the level transitions of the composite signal increases. And, the composite signal actually obtained after inevitable and indeed desirable transition smoothing is shown at 375.

[0040] Figure 4 Shows the spectrum of the carrier signal modulated by the combined signal 340. The spectrum 230 of the original digital signal and the spectrum 430 of the combined signal are shown. As can be seen, the shape of the main peak 432 of the combined signal remains unchanged with respect to the original signal; however, the side lobes 434, 436, 438, 439 have different center frequencies and have a lower magnitude with respect to the side lobes of the original signal.

[0041] The exact degree of power reduction in the side lobes depends on the digital sequence, the number of phase-delayed copies of the repetitive digital sequence signal combined with the original repetitive digital sequence signal, and the choice of phase delay. Currently, it is not possible to mathematically calculate the optimal phase delay for a given number of copies and range of digital sequences.

[0042] It should be understood that the choice of the digital sequence used in the system depends on several criteria. In addition to the sequence length mentioned above, two important factors are autocorrelation and cross-correlation. Generally speaking, for radar applications, it is required to have a minimum and preferably zero cross-correlation between two sequences in the same system, or in two systems expected to operate in the same physical space and thus potentially interfere with each other. As used in the radar field, cross-correlation is a mathematical function corresponding to the result of convolving two sequences or signals. If the sequences are the same, then a perfect cross-correlation corresponding to a correlation level of "1" is produced; conversely, if the sequences are completely uncorrelated, then a zero cross-correlation corresponding to a correlation level of "0" is produced. The lower the cross-correlation, the lower the probability that the receiver will incorrectly identify a signal carrying one sequence as a signal carrying the other sequence or a reflected version of the signal. For two sequences with zero cross-correlation, they must be completely orthogonal, and it should be understood that this is only the case for infinitely long sequences. The shorter the sequence, the higher the cross-correlation with any other sequence. The choice of sequence length is therefore a trade-off for the admissible degree of cross-correlation.

[0043] Now consider the autocorrelation, for perfect autocorrelation the sequence should be infinitely long. Conceptually, autocorrelation relates to the degree to which a sequence corresponds to a time-shifted copy of itself. If the sequence matches the time-shifted sequence perfectly, a perfect autocorrelation corresponding to a correlation level of "1" is produced, resulting in absolute confidence that the time-shifted sequence originates from the original sequence (e.g., from a reflection of the original sequence); conversely, if the sequence is completely uncorrelated with the time-shifted sequence, a zero autocorrelation corresponding to a correlation level of "0" is produced, from which it can be concluded that the time-shifted sequence does not originate from the original sequence, but therefore from an interfering signal. In the field of radar, the autocorrelation function is not a discrete signal: if there is a match in the autocorrelation due to a reflected signal that is delayed relative to the transmitted signal but has the same sequence, then the level of the deltaDirac that will produce the autocorrelation will depend on the magnitude of the reflected signal.

[0044] It will therefore be appreciated that the phase delayed replica of the original sequence has a very high level of autocorrelation with the original sequence. This is quite important as it greatly simplifies the processing requirements of the signal received by the radar receiver in order to identify and analyze reflections of the transmitted signal, as will be discussed in more detail below.

[0045] Now returning to the problem of selecting the number and phase delay of the phase-delayed copies of the repeating digital sequence signal, as already mentioned, it is likely that the optimal number and phase delay cannot be calculated mathematically. However, it has been found experimentally that, in general, an increase in the number of copies leads to a reduction in side lobes, as well as a reduction in the irregular intervals of the phase delay. Conceptually, this can be explained as follows: It is known that a pure square wave signal has an extremely high harmonic component, especially when compared with a sine wave signal having only a fundamental frequency component. The original repeating digital sequence signal corresponds closely to a square wave signal, and it has a high harmonic content. By combining the sequence with a phase-delayed version of the sequence, it is made less similar to a square wave, and this results in a reduction in harmonic content.

[0046] Now turn Figure 5 and 6 According to a first aspect of the present disclosure, a digital modulation radar DMR transmitter module is provided, comprising: a sequence generator 510, 610, which is configured to generate a repetitive digital sequence signal 515, 615 based on a relatively low-frequency clock signal 520, 620. The module further comprises a mixer 530, 630, which is configured to combine the digital sequence signal with at least one phase-delayed copy of the digital sequence signal to provide a combined signal 560, 660; and a modulator ( Figure 5 and Figure 6 ), which is configured to modulate a relatively high frequency carrier signal depending on the combined signal to provide a modulated signal.

[0047] Special consideration now Figure 5, this figure shows an example of the reference frequency section 500 of a module, where there are one or more phase delay circuits 542, 544, 546. Each phase delay circuit is configured to receive a digital sequence signal 515 as an input and provide a corresponding one of at least one phase-delayed copy 552, 554, 556 of the digital sequence signal to a mixer. The at least one phase-delayed copy is phase-delayed by a corresponding predetermined phase shift (φ0 - φ1), (φ0 - φ2), (φ0 - φn). The mixer can be implemented as an exclusive-OR gate. Thus, in this embodiment, a single code generator is used, and a shifted version is generated by delaying the original signal with a phase shifter. Although there are various known methods for phase shifters required to implement such an embodiment, those skilled in the art will understand that this may be challenging or consume a large amount of silicon space and / or power to implement such a phase shifter at the frequencies involved (as mentioned above, it may be about 4 GHz): applying a digital sequence to a clock signal generates an ultra-wideband or UWB signal, and those skilled in the art will understand that phase-shifting the UWB signal is very important.

[0048] Turning now to Figure 6 , this figure shows an example of the reference frequency section 600 of a module, which further includes: one or more phase delay circuits 642, 644, 646. Each phase delay circuit is configured to receive a clock signal as an input and output a corresponding copy of the clock signal, and the corresponding copy is phase-delayed by a corresponding predetermined phase shift (φ1 - φ0), (φ2 - φ0), and (φn - φ0). Those skilled in the art will understand that the shown phase delay circuit 640 that gives the phase shift φ0 is optional. Including this circuit creates a matching path for all signals; φ0 can be set to 0. However, this may be omitted, in which case the phase shifts of the phase delay circuits 642, 644, and 646 will be φ1, φ2, and φ03 respectively. This embodiment also includes one or more additional sequence generators 612, 614, 616 (in addition to the sequence generator 610). Each sequence generator is configured to generate a digital sequence signal based on a corresponding one of at least one phase-delayed copy of the clock signal to provide a corresponding phase-delayed copy of the digital sequence signal to the mixer. That is, each generated signal is triggered by its own separate clock signal. Phase shift can be achieved by shifting the phase of each clock. Thus, for example, the phase shifter in the embodiment can have lower complexity compared to the phase shifter shown in Figure 5 the phase shifter shown in

[0049] Turning now to Figure 7, this figure generally shows a DMR system 700, which includes a DMR transmitter 720 and a receiver module 740. The receiver module includes: a downconverter configured to downconvert the received signal to a reference frequency; a track-and-hold circuit; and an analog-to-digital converter ADC configured to digitize a portion of the downconverted received signal, as well as a digital signal processing module.

[0050] The DMR transmitter 720 includes a transmitter module 710 having one or more phase delay circuits, in this example three phase delay circuits 642, 644, and 646, which are configured to delay the phase of the clock signal 620. The transmitter module 600 includes a sequence generator 610 that applies a digital sequence to the incoming clock signal, and sequence generators 612, 614, and 616 that apply digital sequences to the corresponding phase-delayed versions of the clock signal to generate an original repeated digital sequence signal and three phase-delayed versions of the repeated digital sequence signal, as discussed above with respect to Figure 6 that discussed. The original repeated digital sequence signal is combined with the three phase-delayed versions also as discussed above by a mixer 630. This combined reference signal is then used to modulate a relatively high-frequency carrier signal 715. The modulated carrier signal output from the transmitter module 710 is amplified by a variable gain amplifier 725 and transmitted via an antenna 728.

[0051] The relatively high-frequency carrier signal 715 can be provided by a local oscillator 717. In a non-limiting example, the local oscillator can operate at a relatively high frequency, which can be, for example, 77 GHz. The output from the local oscillator can be divided in a frequency divider 718 to a reference frequency, which can be, for example, between 500 MHz and 4 GHz. The frequency divider can include a fractional frequency divider 719 or be associated with a fractional frequency divider 719. As will be appreciated by those skilled in the art, in other embodiments, the relatively high-frequency carrier signal can be provided by multiplying the frequency of the clock signal. The clock signal can operate at a reference signal, which can be, in another non-limiting example, between 500 MHz and 4 GHz.

[0052] At an antenna 738 forming part of the receiver 730, reflections from the transmitted modulated carrier signal and other interfering or stray signals are received. Together with the antenna 738, the receiver 730 includes a receiver module 740 and a digital signal processing (DSP) unit 760.

[0053] The receiver module 740 receives incoming signals from the antenna 738 and processes the incoming signals in a conventional manner. Specifically, after being amplified by the variable gain amplifier 744, the signal is down-converted by the down-converter 446 into in-phase and quadrature components having a 90° phase difference therebetween. The down-converter utilizes the relatively high-frequency carrier signal 715. The in-phase and quadrature components of the down-converted signal can be amplified in the variable gain amplifier 748 and filtered in the low-pass filter 752. The filtered baseband signal can be digitized with an effective sampling frequency that is twice the signal bandwidth. For example, to do this, a divided-by-two LO signal can be used to drive the track-and-hold amplifier 754 in a normal sampling manner. Alternatively, the frequency of the divided-by-two LO signal can be further divided by a factor k (to provide a signal with a frequency K times lower than the reference frequency): in this way, the signal is subsampled: in other words, the signal is sampled with an instantaneous sampling frequency lower than the instantaneous sampling frequency indicated by the Nyquist theorem, but the signal will repeat k times so that a portion of the signal is sampled in each repetition.

[0054] The receiver further includes a DSP module 760. The DSP module 760 can be part of a microcontroller. (It should be noted that in one or more other embodiments, the DSP module and / or the microcontroller can be separate from the receiver; it can be part of a central processing unit).

[0055] The DSP module 760 performs the functions required for DMR signal processing. Specifically, after the signal has been digitized, the signal can be averaged by using the coherent adder 762 to increase the SNR of the system, and then the signal will be cross-correlated with the original digital sequence used at the transmitter 764. If there are multiple transmitters, then each transmitter can use a different orthogonal digital signal, and thus at each receiver, the same number of cross-correlators must be implemented. In this way, a MIMO system is constructed, and all transmitters can transmit simultaneously, thereby allowing the response of each TX channel on each RX channel to be reconstructed. The advantage of this method is that by using the same number of physical TX / RX, but allowing the virtual RX channels to be reconstructed with cross-correlators, the angular resolution of the radar system can be improved. This is Figure 7 shown as MIMO synthesis 766. The cross-correlation function shows the range of all targets. It should be noted that for each TX, a spectral shaping system is constructed. Finally, as will be familiar to those skilled in the art, by applying fast Fourier transform techniques as shown in 768 to obtain spectral information, Doppler techniques can be used to evaluate the velocity of the target from the spectral information.

[0056] It should be understood that, according to embodiments of the present disclosure, the received baseband signal for radar processing is not a simple copy of the original digital sequence signal. Not only can there be a Doppler effect as in a conventional DMR radar, but according to embodiments, the received signal is a combination of multiple phase-delayed versions of the original digital sequence signal. Although this may be considered to add additional complexity to the processing, this is not actually the case: since the received signal is based on multiple copies of the same digital sequence, these only present as additional time-shifted copies of the original signal that are easily recognizable to the correlator. The correlator can be implemented as a matched filter for the incoming signal, and the matched filter is in the form of a finite impulse response (FIR) filter.

[0057] Turning now Figure 8 , according to one or more embodiments, this figure generally shows a multiple-input multiple-output (MIMO) DMR system 800. In a MIMO DMR system, there are multiple transmitter modules 710, four of which are shown in this particular example. Each of the resulting 4 repeated digital sequence signals, each having a separate orthogonal digital sequence associated therewith, is used to modulate a carrier signal 715, and after being amplified in a respective variable gain amplifier 725, the repeated digital sequence signals are transmitted from separate antennas 728.

[0058] The reflected signal and any interference signals are received by two or more antennas 738, four of which are shown in this particular example. The combination of N transmitters and M receivers results in N×M combinations, which in the example shown is 4×4, thus resulting in 16 combinations. As shown, each receiver includes, for example Figure 7 the receiver module shown at 740 in Figure 7 . The DSP module 860 is also generally similar to

[0059] the module shown in

[0060] The correlator can be based on (but is not limited to) a fast Hadamard transform (FHT) 864 or other techniques that will be well known to those skilled in the art of radar processing. The additional processing feature provided by MIMO is the feature of digital beamforming 870 in order to provide angle-of-arrival information to improve the localization of individual targets, which will also be well known to those skilled in the art of radar processing.

[0059] By reading this disclosure, those skilled in the art will appreciate other variations and modifications. Such variations and modifications may relate to equivalents and other features known in the DMR field, and these features can be used to replace or supplement the features already described herein.

[0060] As used herein, the term "phase-delayed copy of a signal" (or generally "phase-shifted copy of a signal") refers to a signal having the same content as the original signal but delayed (or correspondingly shifted) in time. Thus, if a signal has a fundamental frequency of, for example, 1 GHz, then it has a primary period of 1 ns. A phase-delayed copy of the signal having a 90° phase delay will thus lag the original signal by (90° / 360°)×1 ns, that is, 250 ps, and a phase-delayed copy of the signal having a 270° phase delay will lag the original signal by (270° / 360°)×1 ns or 750 ps.

[0061] Although the appended claims are directed to specific combinations of features, it should be understood that the scope of the disclosure of the present invention also includes any novel feature or any novel combination of features or any generalization thereof that is explicitly or implicitly disclosed herein, regardless of whether it relates to the same invention as that currently claimed in any claim or whether it alleviates the same technical problems as any or all of the technical problems alleviated by the present invention.

[0062] Features described in the context of separate embodiments may also be provided in combination in a single embodiment. Conversely, for the sake of brevity, the various features described in the context of a single embodiment may also be provided separately or in any suitable sub-combination. The applicant hereby reminds that during the examination of this application or any additional application derived therefrom, new claims may be formulated based on such features and / or combinations of such features.

[0063] For completeness, it is also stipulated that the term "comprising" does not exclude other elements or steps, the articles "a" or "an" do not exclude a plurality, a single processor or other unit may fulfill the functions of several means recited in the claims, and the reference signs in the claims should not be construed as limiting the scope of the claims.

Claims

1. A digital modulation radar (DMR) transmitter module, characterized in that, Comprising: A sequence generator configured to generate a repetitive digital sequence signal based on a low-frequency clock signal; A mixer configured to combine the repetitive digital sequence signal with at least one phase-delayed copy of the repetitive digital sequence signal to provide a combined signal; And A modulator configured to modulate a high-frequency carrier signal depending on the combined signal to provide a modulated signal.

2. The DMR transmitter module according to claim 1, characterized in that, Further comprising: One or more phase delay circuits, each phase delay circuit being configured to receive the repetitive digital sequence signal as an input and provide a corresponding one of the at least one phase-delayed copy of the repetitive digital sequence signal to the mixer, the corresponding one of the at least one phase-delayed copy being phase-delayed by a corresponding predetermined phase shift.

3. The DMR transmitter module according to claim 1, wherein Further comprising: One or more phase delay circuits, each phase delay circuit being configured to receive the clock signal as an input and output a corresponding copy of the clock signal, the corresponding copy being phase-delayed by a corresponding predetermined phase shift; And One or more additional sequence generators, each additional sequence generator being configured to generate a repetitive digital sequence signal based on a corresponding one of the at least one phase-delayed copy of the clock signal to provide a corresponding phase-delayed copy of the repetitive digital sequence signal to the mixer.

4. The DMR transmitter module according to any one of the preceding claims, characterized in that, The modulator is a phase shift keying (PSK) modulator and the modulated signal is a PSK modulated signal.

5. The DMR transmitter module according to claim 4, characterized in that, The PSK modulated signal is a binary phase shift keying (BPSK) signal.

6. The DMR transmitter module according to any one of claims 1-3, characterized in that, The modulator is an amplitude modulator and the modulated signal is an amplitude modulated signal.

7. The DMR transmitter module according to any one of claims 1-3, characterized in that, The high-frequency carrier signal is sourced from a local oscillator and one of the clock signals is sourced from the local oscillator, or the local oscillator is sourced from the clock signal.

8. A DMR system, characterized in that, Comprising a DMR transmitter module according to any one of the preceding claims and further comprising a receiver module, wherein the receiver module comprises: A downconverter configured to downconvert the received signal to a reference frequency; A track and hold circuit; And an analog-to-digital converter (ADC) configured to digitize a portion of the downconverted received signal.

9. The DMR system according to claim 8, wherein The receiver module further comprises A cross-correlation unit configured to cross-correlate the portion of the downconverted received signal with the repetitive digital sequence signal.

10. A method for generating a digitally modulated radar signal, characterized in that, The method comprises: Generating a digital sequence and a repetitive digital sequence signal based on the digital sequence and a low-frequency clock signal; Generating at least one phase-delayed copy of the repetitive digital sequence signal; Combining the repetitive digital sequence signal with at least one phase-delayed copy of the repetitive digital sequence signal in a mixer to provide a combined signal; and Modulating a high-frequency carrier signal depending on the combined signal to provide the digitally modulated radar signal.

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