阅读说明：本技术 使用二进制移相器的慢时频分复用 (Slow time frequency division multiplexing using binary phase shifters ) 是由 李正征 K·J·奥斯特 于 2019-07-17 设计创作，主要内容包括：检测器设备(22)的说明性示例实施例包括多个发射器(26)以及控制器(30),该控制器控制该发射器(26)在周期内发射至少部分地由2N个脉冲的序列定义的相应信号。N是大于1的整数。发射器(26)中的第一个在周期内发射2N个第一信号脉冲。该2N个第一信号脉冲中的每一个具有第一相位。发射器(26)中的第二个在周期内发射2N个第二信号脉冲。2N个第一信号脉冲中的每一个与2N个第二信号脉冲中的一个是同时的。N个第二信号脉冲具有相对于第一相位的180°相移。其他第二信号脉冲具有第一相位。具有相移的N个第二信号脉冲在序列中彼此紧密相邻。(An illustrative example embodiment of a detector device (22) includes a plurality of emitters (26) and a controller (30) that controls the emitters (26) to emit respective signals defined at least in part by a sequence of 2N pulses within a period. N is an integer greater than 1. A first one of the transmitters (26) transmits 2N first signal pulses within a period. Each of the 2N first signal pulses has a first phase. A second one of the transmitters (26) transmits 2N second signal pulses within the period. Each of the 2N first signal pulses is simultaneous with one of the 2N second signal pulses. The N second signal pulses have a phase shift of 180 ° with respect to the first phase. The other second signal pulses have a first phase. The N second signal pulses with phase shifts are closely adjacent to each other in the sequence.)

1. A detector apparatus (22) comprising:

a plurality of emitters (26); and

a controller (30) that controls the transmitter (26) to transmit respective signals defined at least in part by a sequence of 2N pulses within a period,

wherein:

n is an integer greater than 1 and N is an integer greater than 1,

a first one of the transmitters (26) transmits 2N first signal pulses within the period,

each of the 2N first signal pulses has a first phase,

a second one of said transmitters (26) transmitting 2N second signal pulses within said period,

each of the 2N first signal pulses is simultaneous with one of the 2N second signal pulses,

the N second signal pulses have a phase shift of 180 deg. with respect to said first phase,

the other second signal pulses have the first phase, an

The N second signal pulses with the phase shift are immediately adjacent to each other in the sequence.

2. A detector device (22) as claimed in claim 1, comprising a binary phase shifter (40) which introduces said phase shift of said N second signal pulses having said phase shift.

3. A detector device (22) as claimed in claim 1, characterized in that

A third one of the transmitters (26) transmits 2N third signal pulses within the period,

each of said 2N first signal pulses being simultaneous with one of said 2N third signal pulses,

the N third signal pulses have a phase shift of 180 deg. with respect to said first phase,

the other of said third signal pulses having said first phase,

the N third signal pulses with the phase shift are immediately adjacent to each other in the sequence, and

at least one of the N third signal pulses having the phase shift is simultaneous with one of the second signal pulses having the first phase.

4. A detector device (22) as claimed in claim 1, comprising a plurality of receivers (28) and

wherein

The receiver (28) receiving a reflected signal comprising respective signals reflected by objects within a vicinity of the detector device (22);

the reflected signal comprises a first portion corresponding to the 2N first signal pulses and a second portion corresponding to the 2N second signal pulses;

the first portion has a single peak having a first amplitude at a first frequency;

the second portion has two peaks separated by a second frequency; and

the controller (30) distinguishes the first portion and the second portion based on the second frequency.

5. A detector device (22) as claimed in claim 4, characterized in that each of the two peaks has an amplitude which is lower than the first amplitude.

6. The detector device (22) according to claim 5, wherein the amplitude of one of the two peaks is greater than the amplitude of the other of the two peaks.

7. A detector device (22) as claimed in claim 4, characterized in that the second frequency corresponds to the 180 ° phase shift.

8. A detector device (22) as claimed in claim 4, characterized in that

The controller (30) controls the transmitter (26) to repeatedly transmit the respective signal over a plurality of periods; and

the second frequency is held constant over the plurality of periods.

9. A detector device (22) as claimed in claim 4, characterized in that the single peak is always different from the two peaks.

10. A method of detecting at least one object, the method comprising:

transmitting a sequence of 2N first pulse signals from a first transmitter (26) over a period, each of the 2N first signal pulses having a first phase; and

transmitting a sequence of 2N second signal pulses from a second transmitter (26) within the period,

wherein each of said 2N first signal pulses is simultaneous with one of said 2N second signal pulses, N second signal pulses having a 180 ° phase shift with respect to said first phase, the other of said second signal pulses having said first phase, said N second signal pulses having said phase shift being immediately adjacent to each other in said sequence, and N being an integer greater than 1.

11. The method of claim 10, comprising introducing said phase shift of said N second signal pulses having said phase shift using a binary phase shifter (40).

12. The method of claim 10, comprising transmitting a sequence of 2N third signal pulses from a third transmitter (26) within the period,

wherein each of the 2N first signal pulses is simultaneous with one of the 2N third signal pulses, N third signal pulses having a 180 ° phase shift with respect to the first phase, the other third signal pulses having a first phase, the N third signal pulses having the phase shift are immediately adjacent to each other in the sequence, and at least one of the N third signal pulses having the phase shift is simultaneous with one of the second signal pulses having the first phase.

13. The method of claim 10, comprising:

receiving a reflected signal comprising the first signal pulse and a second signal pulse reflected by an object, wherein the reflected signal comprises a first portion corresponding to the 2N first signal pulses and a second portion corresponding to the 2N second signal pulses, the first portion having a single peak with a first amplitude at a first frequency, the second portion having two peaks separated by a second frequency, and

distinguishing the first portion from the second portion based on the second frequency.

14. The method of claim 13, wherein each of the two peaks has an amplitude that is lower than the first amplitude.

15. The method of claim 14, wherein the amplitude of one of the two peaks is greater than the amplitude of the other of the two peaks.

16. The method of claim 13, wherein the second frequency corresponds to the 180 ° phase shift.

17. The method of claim 13, comprising repeating the transmitting of the sequence of respective signal pulses over a plurality of periods, and wherein the second frequency is held constant over the plurality of periods.

18. The method according to claim 13, wherein said single peak is always different from said two peaks.

19. A detector apparatus (22) comprising:

a plurality of emitting devices (26); and

control means (30) for controlling the emitting means to emit respective signals defined at least in part by a sequence of 2N pulses within a period,

wherein:

n is an integer greater than 1 and N is an integer greater than 1,

a first one of said transmitting means transmits 2N first signal pulses within said period,

each of the 2N first signal pulses has a first phase,

a second one of said transmitting means transmits 2N second signal pulses within said period,

each of the 2N first signal pulses is simultaneous with one of the 2N second signal pulses,

the N second signal pulses have a phase shift of 180 deg. with respect to said first phase,

the other second signal pulses have the first phase, an

The N second signal pulses with the phase shift are immediately adjacent to each other in the sequence.

20. A detector device (22) as claimed in claim 19, comprising a plurality of receiving means (28) and wherein

-the receiving means (28) receiving a reflected signal comprising respective signals reflected by objects in a range near the detector device (22);

the reflected signal comprises a first portion corresponding to the 2N first signal pulses and a second portion corresponding to the 2N second signal pulses;

the first portion has a single peak having a first amplitude at a first frequency;

the second portion possesses two peaks separated by a second frequency; and

the control device (30) distinguishes the first portion and the second portion based on the second frequency.

Background

Automotive radar sensors play a key role in Advanced Driving Assistance Systems (ADAS) because they provide information about the environment surrounding the host vehicle. Highly automated driving requires high resolution in range, doppler and angle, especially the ability to distinguish multiple targets with the same range and doppler, which requires more antenna channels.

A MIMO (multiple input multiple output) scheme is commonly used for radar systems to realize a large number of antenna channels. For example, a typical MIMO radar system with three Transmit (TX) channels and four Receive (RX) channels may form a virtual array of 12 channels. Since the virtual array position is a spatial convolution of the TX and RX antenna positions, by placing the TX and RX antennas in different ways, different virtual arrays can be formed to achieve better angle discrimination performance, reduce angle uncertainty, or both.

Waveform orthogonality is used in MIMO radar systems to transmit and receive independent orthogonal RF signals and enables different TX channels to be identified or separated in the same RX channel. Various methods exist for implementing orthogonal waveforms, including Time Division Multiplexing (TDM), Frequency Division Multiplexing (FDM), and Code Multiplexing (CM). Each of these three approaches has advantages and disadvantages associated with it.

FDM places signals from different TX channels in different frequency bands by adding a frequency offset to the transmitted signal. Which is typically implemented in the fast time (range) domain. Apart from the range-dependent phase offset introduced between the channels and the reduced unambiguous range coverage, the main drawback is that it requires a higher sampling rate due to the increased IF bandwidth.

Both FDM and CM methods enable simultaneous transmission and both methods can be implemented in both fast-time (within one chirp, range domain) and slow-time (chirp-to-chirp, doppler domain). The CM attempts to recover the signal that matches the current code by suppressing energy from other encoded signals. The allocated energy left by the suppressed signal is commonly referred to as the residual, which limits the dynamic range of the system. The limited dynamic range limits the ability to detect small objects when large objects are present.

Us patent No. 7,474,262 describes the concept of using a MIMO radar system with TDM that does not have simultaneous transmission. Instead, the individual transmitters transmit sequentially, which results in no interference between the TX channels and maximum orthogonality between the TX channels. However, this technique does not provide the signal-to-noise ratio gain achieved by simultaneous transmissions and can lead to other problems, such as doppler uncertainty between TX channels.

U.S. patent No. 9,952,319 to seary et al describes a technique for reducing residual levels. While this approach works well, it involves computational complexity and can be difficult to implement in real-time. CM is typically implemented in the slow-time doppler domain because it requires a specific transmitter and receiver design and higher IF bandwidth for fast-time implementation.

Published by c.sturm, y.l.sit, g.li, h.a.vayghan and U.L ü bbert entitled "Automotive Fast-Chirp MIMO Radar with simultaneous Transmission in Doppler multiplexing" (proc.irs convention, 2018) describes the implementation of ST-FDM with binary phase shifters for Radar systems with two TX channels.

Us patent No. 9,182,476 describes a radar system having an arrangement and method for decoupling transmit and receive signals and for suppressing interfering radiation.

U.S. published application No. 2017/0160380 suggests a pseudo-random phase modulation (PRPM) scheme for achieving high residual levels of MIMO, residual cancellation, and improved dynamic range from the PRPM scheme.

Despite the advances in utilizing such technologies, there is also a need for improvements. For example, increased reliance on object detection on motor vehicles increases the need for better detection. The previously proposed approaches are often affected by at least one drawback, such as not providing sufficient discrimination between signals, or not providing simultaneous transmission resulting in a smaller signal-to-noise ratio.

Disclosure of Invention

An illustrative example embodiment of a detector apparatus includes a plurality of emitters and a controller that controls the emitters to emit respective signals defined, at least in part, by a sequence of 2N pulses within a period. N is an integer greater than 1. A first one of the transmitters transmits 2N first signal pulses within a period. Each of the 2N first signal pulses has a first phase. A second one of the transmitters transmits 2N second signal pulses within the period. Each of the 2N first signal pulses is simultaneous with one of the 2N second signal pulses. The N second signal pulses have a phase shift of 180 ° with respect to the first phase. The other second signal pulses have a first phase. The N second signal pulses with phase shifts are closely adjacent to each other in the sequence.

An example embodiment having one or more features of the detector apparatus in the previous paragraph includes a binary phase shifter that introduces a phase shift of the N second signal pulses having a phase shift.

In an example embodiment having one or more features of the detector device of any of the preceding paragraphs, a third one of the emitters emits 2N third signal pulses within the period, each of the 2N first signal pulses is simultaneous with one of the 2N third signal pulses, the N third signal pulses have a 180 ° phase shift with respect to the first phase, the other third signal pulses have the first phase, the N third signal pulses having the phase shift are closely connected to each other in the sequence, and at least one of the N third signal pulses having the phase shift is simultaneous with one of the second signal pulses having the first phase.

An example embodiment having one or more features of the detector device of any of the preceding paragraphs includes a plurality of receivers. The receiver receives a reflected signal comprising a respective signal reflected by an object located within a vicinity of the detector device, the reflected signal comprising a first portion corresponding to the 2N first signal pulses and a second portion corresponding to the 2N second signal pulses, the first portion having a single peak with a first amplitude at a first frequency and the second portion having two peaks separated by a second frequency, and the controller distinguishes the first portion from the second portion based on the second frequency.

In an example embodiment having one or more features of the detector device of any of the preceding paragraphs, each of the two peaks has an amplitude that is lower than the first amplitude.

In an example embodiment having one or more features of the detector device of any of the preceding paragraphs, the amplitude of one of the two peaks is greater than the amplitude of the other of the two peaks.

In an example embodiment having one or more features of the detector device of any of the preceding paragraphs, the second frequency spectrum corresponds to a 180 ° phase shift.

In an example embodiment having one or more features of the detector device of any of the preceding paragraphs, the controller controls the emitter to repeatedly emit the respective signal over a plurality of periods and the second frequency is kept constant over the plurality of periods.

In an exemplary embodiment having one or more features of the detector device of any of the preceding paragraphs, the single peak is always different from the two peaks.

An illustrative example method for detecting at least one object includes: transmitting a sequence of 2N first pulse signals from a first transmitter over a period, each of the 2N first pulse signals having a first phase; and transmitting a sequence of 2N second signal pulses from the second transmitter over the period. Each of the 2N first signal pulses is simultaneous with one of the 2N second signal pulses, the N second signal pulses having a 180 ° phase shift with respect to the first phase, the other second signal pulses having the first phase, the N second signal pulses having the phase shift being immediately adjacent to each other in the sequence, and N being an integer greater than 1.

An example embodiment having one or more features of the method of the preceding paragraph includes using a binary phase shifter to introduce a phase shift of the N second signal pulses having a phase shift.

An example embodiment having one or more features of the method of any of the preceding paragraphs includes transmitting a sequence of 2N third signal pulses from a third transmitter within the period. Each of the 2N first signal pulses is simultaneous with one of the 2N third signal pulses, the N third signal pulses having a 180 ° phase shift with respect to the first phase, the other third signal pulses having the first phase, the N third signal pulses having the phase shift being immediately adjacent to each other in the sequence, and at least one of the N third signal pulses having the phase shift being simultaneous with one of the second signal pulses having the first phase.

Example embodiments having one or more features of the method of any of the preceding paragraphs include: receiving a reflected signal comprising first signal pulses and second signal pulses reflected by an object, wherein the reflected signal comprises a first portion corresponding to 2N first signal pulses and a second portion corresponding to 2N second signal pulses, the first portion having a single peak having a first amplitude at a first frequency, the second portion having two peaks separated by a second frequency; and distinguishing the first portion from the second portion based on the second frequency.

In an example embodiment having one or more features of the method of any of the preceding paragraphs, each of the two peaks has an amplitude that is lower than the first amplitude.

In an example embodiment having one or more features of the method of any of the preceding paragraphs, the amplitude of one of the two peaks is greater than the amplitude of the other of the two peaks.

In an example embodiment having one or more features of the method of any of the preceding paragraphs, the second frequency spectrum corresponds to a 180 ° phase shift.

An example embodiment having one or more features of the method of any of the preceding paragraphs includes repeatedly transmitting the sequence of respective signals over a plurality of periods and wherein the second frequency is held constant over the plurality of periods.

In an example embodiment having one or more features of the method of any of the preceding paragraphs, the single peak is always different from the two peaks.

An illustrative example embodiment of a detector apparatus comprises a plurality of emitting means and control means for controlling the emitting means to emit respective signals defined at least in part by a sequence of 2N pulses within a period. N is an integer greater than 1, a first one of the transmitting means transmits 2N first signal pulses within a period, each of the 2N first signal pulses having a first phase, a second one of the transmitting means transmits 2N second signal pulses within the period, each of the 2N first signal pulses being simultaneous with one of the 2N second signal pulses, the N second signal pulses having a 180 ° phase shift with respect to the first phase, the other second signal pulses having the first phase, and the N second signal pulses having the phase shift being immediately adjacent to each other in the sequence.

An example embodiment having one or more features of the detector apparatus of any of the preceding paragraphs includes a plurality of receiving devices. The receiving means receives a reflected signal comprising a respective signal reflected by an object located in a range near the detector device, the reflected signal comprising a first portion corresponding to the 2N first signal pulses and a second portion corresponding to the 2N second signal pulses, the first portion having a single peak with a first amplitude at a first frequency and the second portion having two peaks separated by a second frequency, and the control means distinguishes the first portion from the second portion based on the second frequency.

Various features and advantages of at least one disclosed embodiment will become apparent to those skilled in the art from the following detailed description. The drawings that accompany the detailed description can be briefly described as follows.

Drawings

Fig. 1 schematically illustrates a vehicle comprising a plurality of detector devices.

Fig. 2 schematically illustrates an example embodiment of a detector device.

Fig. 3 illustrates an example relationship between TX signals of two transmitters.

Fig. 4 schematically illustrates simultaneously transmitted signal pulses consistent with fig. 3.

Figure 5 graphically illustrates a received signal represented by a doppler frequency bin.

Fig. 6 illustrates an example relationship between TX signals of three transmitters.

Fig. 7 schematically illustrates simultaneously transmitted signal pulses consistent with fig. 6.

Fig. 8 illustrates the relationship between signal pulse sequences for any number of transmitters.

Detailed Description

Embodiments of the present invention facilitate the simultaneous transmission of multiple TX channels for a MIMO detector system with binary phase shifters. The disclosed example embodiments support multiple transmitters to transmit simultaneously with accurate recovery and in the absence of uncertainty. Accurate recovery is possible because there is no interference between TX channels. Uncertainty is also not a problem because the disclosed scheme makes it possible to identify each channel in the received signal without additional information.

Fig. 1 illustrates a vehicle 20 that includes a plurality of detectors 22 that are capable of detecting any objects located in a field of view 24. For discussion purposes, the detector 22 of the disclosed example embodiment is configured to use radio detection and ranging (RADAR) technology. Other detection techniques are useful in some embodiments, such as sonar and light detection and ranging (LIDAR).

A plurality of transmitters 26, which plurality of transmitters 26 are antennas in this example, are configured to transmit respective signals useful for detecting any objects located near the vehicle 20 and within the field of view of the detector 22. The plurality of receivers 28 are configured to receive the reflected signal, which is the reflected signal of the transmitted signal after it has been reflected by the object.

The controller 30 includes a processor 32 and a memory 34. At least processor 32 includes programming or is otherwise configured to control operation of transmitter 26. In the illustrated example embodiment, the controller 30 includes a voltage controlled oscillator 38 that provides a basis for the signal transmitted by the transmitter 26. Binary phase shifters 40 are respectively associated with the transmitters 26 to control the phase shift applied on one or more signal pulses transmitted by the transmitters 26. Each binary phase shifter 40 has two output stages: the binary phase shifter 40 in this example introduces a pi phase shift, 0 deg. (through) and 180 deg. (sign flipped or phase reversed). In the present example, the controller 30 is schematically shown as including a binary phase shifter 40, but they may be different components.

The receiver 28 receives the reflected signals and the controller 30 processes such received signals to make one or more determinations relating to any objects located within the field of view 24 (fig. 1) of the detector apparatus 22. The output of voltage controlled oscillator 30 is used as a reference and is combined with the received signal at 42. The received signal is then processed by a band pass filter 44, a low noise amplifier 46, and an analog-to-digital converter 48, and then analyzed by a digital signal processor 50 to make one or more determinations about any objects reflecting the received signal. Although illustrated as separate processors 32 and 50, some embodiments include a single processor that controls the transmission and makes decisions based on the reception of signals by the detector device 22.

Fig. 3 and 4 schematically illustrate an example control strategy 52 for controlling two transmitters 26. Based on the operation of voltage controlled oscillator 38, a first one of transmitters 26 transmits a sequence of 2N first signal pulses 54, 56, 58, and 60 within a period. Each of the first signal pulses has a first phase, which in this example corresponds to 0 °. The first phase may be considered a reference or reference phase. In this example, N is 2 and there are four pulses per cycle. The second cycle is shown in fig. 3.

A second one of the transmitters 26 transmits second signal pulses 62, 64, 66 and 68 simultaneously with the first signal pulses 54, 56, 58 and 60 during the same period. One aspect of the exemplary detector device 22 is that each of the first signal pulses is transmitted simultaneously with one of the second signal pulses. Controller 30 causes binary phase shifter 40 associated with a second one of transmitters 26 to introduce a 180 ° phase shift for N of the second signal pulses. In this example, only two of the second signal pulses include a phase shift in each period, since N-2. The second signal pulses comprising the phase shift are transmitted in sequence next to each other without any pulse having a different phase between them. In other words, the second signal pulses comprising a phase shift of 180 ° are transmitted one after the other until N of them are all transmitted in each period. The same pulse pattern or sequence is repeated in each subsequent cycle.

The first signal pulse and the second signal pulse are always transmitted simultaneously and include a phase shift for N of the 2N pulses within each period makes it possible to accurately recover the received signal without uncertainty. The MIMO feature reduces or eliminates signal-to-noise loss. A doppler bin representation of an example received signal is shown schematically at 70 in figure 5. The first portion of the received signal corresponds to the first signal pulse and includes a single peak 72. The second portion of the received signal corresponds to the second signal pulse and includes two peaks 74 and 76. The peak 72 has a first amplitude and is centered at a first frequency that depends on a reference frequency of the first signal pulses, such as 0 °. The two peaks 74 and 76 have a second amplitude and are separated by a second frequency, indicated by 80. The phase shift in the N second signal pulses included in the second signal pulses and the sequential manner in which these pulses are transmitted within a cycle (i.e., one after the other) establishes the two peaks 74 and 76 and the second frequency 80 separating the two peaks. The controller 30 distinguishes between the portion of the received signal corresponding to the first signal pulse and the portion corresponding to the second signal pulse based on the second frequency 80.

The consistent separation between the two peaks 74 and 76 enables the portion of the received signal corresponding to the second signal pulse to be consistently distinguished, which minimizes or eliminates uncertainty between the first and second portions of the received signal. Transmitting pulses from each of the actively transmitting transmitters all the time increases the amount of signaling information available as compared to other techniques that transmit pulses from a second transmitter only part of the time. The disclosed signaling techniques provide better detection than previous MIMO techniques.

The controller 30 uses the first and second portions of the received signal for detection and analysis based on the doppler shift principle in the reflected signal and a signaling technique comprising a sequence of 2N transmitted pulses, transmitting all pulses from multiple transmitters simultaneously and a binary phase shift for N of the 2N pulses. Moving objects cause progressive phase differences between pulses, which introduce doppler shifts in the received signal. This can be expressed by the following equation

Where x represents the received signal, k represents the pulse, Δ t is the pulse repetition time, n (k) represents noise and ω is_dIs the doppler frequency.

The phase modulation c (k) introduced by the binary phase modulator 40 of the example phase modulation scheme of the present disclosure that repeats 2N phase terms in each cycle can be represented by the following equation

Wherein the nth peak of the mth code is described by

Amplitude at nth peak of mth code is

It can be further simplified to

Turning to the examples in fig. 3-5, phase modulation is described as

Wherein e^jk(π/2)Correspond to

e^j-k(π/2)Correspond to

e^j-(π/2)Corresponds to-j, and e^j(π/2)Corresponding to + j.

Using S to represent the slow-time fast Fourier transform, the controller 30 (or DSP50) is based on S (ω)_d) A single peak 72 is determined. Doublets 74 and 76 are based on controller 30

And (6) obtaining. The amplitude of peak 74 is 0.5(1+ j) TX2 and the amplitude of peak 76 is 0.5(1-j) TX 2. After combining, peaks 74 and 76 have the same power TX 1. In some embodiments, peaks 74 and 76 are each 3dB lower than peak 72. The controller uses such information related to the received signal to make a desired or necessary determination regarding objects present near or in the path of the vehicle 20.

Although two transmitters 26 are included in the above example, the disclosed approach supports any number of transmitters that transmit using simultaneous pulses, with N of their 2N pulses having a phase shift for all but one of the transmitters. Fig. 6 and 7 schematically illustrate a transmission scheme using a period of four pulses and N-2. A first one of the transmitters 26 transmits a sequence of first signal pulses 92, 94, 96 and 98 without any phase shift. A second one of the transmitters 26 transmits a sequence of second signal pulses 100, 102, 104 and 106. Two pulses 104 and 106 of the second signal pulse train include a phase shift relative to the first phase of first signal pulses 92-98 introduced by binary phase shifter 40 associated with second transmitter 26. During the same period, third transmitter 26 transmits a third signal pulse train comprising four pulses 108, 110, 112, and 114. The two pulses 110 and 112 include a phase shift relative to the first phase of the pulses 92-98.

As can be appreciated from fig. 6 and 7, the second and third transmitters transmit one of the respective signal pulses each time the first transmitter 26 transmits one of the first signal pulses 92-98.

The second signal pulses 104 and 106 include a phase shift and are timed with respect to the third signal pulses such that at least one of the third signal pulses 110 and 112 that includes the phase shift is transmitted simultaneously with one of the second signal pulses that does not include any phase shift with respect to the first phase of the first signal pulse. In this illustration, pulse 110, which includes a phase shift, is simultaneous with pulse 102, which does not include a phase shift. Staggering the phase-shifted pulses of the second and third transmitters within a period while maintaining the pattern of the phase-shifted pulses (i.e., maintaining them in close proximity to each other in the sequence) enables distinguishing between the portion of the received signal corresponding to the second signal pulse and the portion of the received signal corresponding to the third signal pulse.

Fig. 5 is also a doppler bin representation of a received signal generated by the reflection of a signal pulse, which is represented in the graphs of fig. 6 and 7. In this case, TX1 (e.g., the first part) of the received signal is received by DSP50 from S (ω)_d) Obtained, and TX2 and TX3 can be obtained from the following linear equations:

wherein the amplitude of the peak 74 is determined by

Described, and the amplitude of peak 76 is defined byA description is given.

For up to 3 TX channels, the disclosed phase modulation scheme is based on a sequence of 4 (i.e., N-2) repeated phase terms in each period. This scheme supports arbitrary periods that contain pulses that are multiples of 4, such as 64 or 512. When N ═ 2, only three independent codes are available, which means that up to three TX are supported using a total of four code combinations. This is because the energy is divided into three peaks in the slow-time spectrum. Different combinations can be obtained by changing the initial phase of TX2 and TX3 from 0 ° to 180 °.

Additional orthogonal codes may be used by extending the repeated phase terms to 6 (i.e., N-3), 8 (i.e., N-4), or even more terms. As the period becomes longer, the spectrum becomes more congested with more peaks and channels, but the manner of the channel including multiple peaks of phase-shifted pulses still allows for distinguishing between portions of the received signal corresponding to each channel.

For example, when N-3, the energy is divided into three peaks and the detector device 22 supports four independent TX channels, each with its own signal pulse sequence. If a code with 4 repeating phase terms and 6 repeating phase terms is combined, the disclosed phase modulation scheme can support a total of 6 TX and the phase length (i.e., 2N) is set to a multiple of 12, such as 60. For 8 repeated phase terms, the energy source is divided into four peaks, so the detector apparatus 22 can support four independent TX channels. It should be noted that two of the peaks from the 8 repeated phase terms will overlap with two of the peaks from the 4 repeated phase terms, so it is best to combine with the 6 repeated phase terms in order to obtain the best performance by supporting a total of 8 TX channels.

Fig. 8 illustrates how the disclosed technique may be applied to any number m of transmitters 26 and transmit channels TX, where m is N + 1. The first signal pulse at 120 has a first phase of 0 deg. throughout the entire sequence of 2N pulses. Each signal pulse sequence of the other TX comprises 2N terms in each period, where the N terms comprise the phase shift introduced by the corresponding binary phase shifter 40. The N pulses with phase shift remain closely adjacent to each other in the sequence, even though the number of pulses without any phase shift may vary between the end of the sequence and the N pulses with phase shift. For example, TX2 includes N pulses with a first frequency of 0 ° before N pulses with a phase shift. TXm has only one pulse of the first frequency before N pulses including phase shifting. Staggering the positions of the N pulses, including the phase shift, within the respective sequence as shown allows distinguishing each TX from the other. The order within each sequence may be considered to be different codes and each TX has a unique code.

Although the first phase of the first signal pulse of TX1 is 0 ° in the above example, it is also possible to add a random code to TX1 for interference mitigation purposes. The code of TX2 passing through any TXm may be modified accordingly so that the phase difference between the channels is maintained consistent with the techniques described above.

The improved MIMO method used in the disclosed embodiments supports multiple TX simultaneous transmissions and generates reliable TX channel recovery from the received signal without uncertainty. The disclosed example embodiments provide a technique that enables simultaneous transmission and recovery of multiple TX channels in a slow time (doppler) spectrum using binary phase modulation. The disclosed ST-FDM scheme transfers energy from different TXs to different frequency bins in the slow-time doppler frequency spectrum. It also improves detection dynamic range, signal to noise ratio, and processing efficiency.

The preceding description is exemplary rather than limiting in nature. Variations and modifications to the disclosed examples may become apparent to those skilled in the art that do not necessarily depart from the essence of this invention. The scope of legal protection given to this invention can only be determined by studying the following claims.