Space-Time Frequency Multiplexing (STFM) of a Radar System Using Complementary Pair Waveforms

Abstract

A spatio-temporal frequency multiplexing (STFM) scheme for radio frequency (RF) scanning is disclosed, in which complementary sequence pairs (or "Golay pairs") are transmitted at different times using multiple frequencies. Transmission and reception of the sequences can occur on multiple transmit (Tx) and / or receive (Rx) radio sectors to scan the distance, azimuth, elevation, and (optionally) velocity of an object in an entire area.

Description

[0001] Claim of priority

[0002] This patent application claims priority to U.S. Non - Provisional Application No. 16 / 440,934, filed on June 13, 2019, entitled "Space Time Frequency Multiplexing (STFM) for Radar Systems Using Complementary Pair Waveforms", which is assigned to the assignee hereof and is hereby incorporated by reference in its entirety. Background Art

[0003] Radar technology is used in a variety of automotive applications and is considered one of the key technologies for future autonomous driving systems. Since it can work reliably under adverse weather and lighting conditions to provide accurate measurements of target range, speed, and angle in multi - target scenarios, it can be a particularly useful data source in automotive and other applications. However, the resolution and speed requirements of future radar systems may exceed the capabilities of the radar systems used in at least some current automotive applications. Summary of the Invention

[0004] The techniques described herein solve these and other problems by utilizing a Space Time Frequency Multiplexing (STFM) scheme in which multiple frequencies are used to transmit complementary sequence pairs (or "Golay pairs") at different times. The transmission and reception of sequences can occur on multiple transmit (Tx) and / or receive (Rx) radio sectors to scan for the distance, azimuth, elevation, and (optionally) speed of objects in an entire area.

[0005] According to the description, an exemplary method for radio frequency (RF) sensing using Space Time Frequency Multiplexing (STFM) includes: performing a transmit sequence, where the transmit sequence includes wirelessly transmitting a first sequence of a first complementary sequence pair using a first frequency, and then, after wirelessly transmitting the first sequence of the first complementary sequence pair, wirelessly transmitting a first sequence of a second complementary sequence pair using a second frequency. The transmit sequence further includes: after wirelessly transmitting the first sequence of the second complementary sequence pair, wirelessly transmitting a second sequence of the first complementary sequence pair using the first frequency, and after wirelessly transmitting the second sequence of the first complementary sequence pair, wirelessly transmitting a second sequence of the second complementary sequence pair using the second frequency. The method further includes performing a receive sequence, where the receive sequence includes receiving the first complementary sequence pair and receiving the second complementary sequence pair. The method further includes determining the distance of an object based on the received first complementary sequence pair and the received second complementary sequence pair.

[0006] According to the description, an exemplary radar system for performing radio frequency (RF) sensing using spatio-temporal frequency multiplexing (STFM) includes a transmit circuit. The transmit circuit is configured to perform a transmit sequence that includes: wirelessly transmitting a first sequence in a first complementary sequence pair using a first frequency, and after wirelessly transmitting the first sequence in the first complementary sequence pair, wirelessly transmitting a first sequence in a second complementary sequence pair using a second frequency. The transmit sequence further includes: after wirelessly transmitting the first sequence in the second complementary sequence pair, wirelessly transmitting a second sequence in the first complementary sequence pair using the first frequency, and after wirelessly transmitting the second sequence in the first complementary sequence pair, wirelessly transmitting a second sequence in the second complementary sequence pair using the second frequency. The radar system further includes a receive circuit configured to perform a receive sequence that includes receiving the first complementary sequence pair and receiving the second complementary sequence pair. The radar system further includes a processing circuit communicatively coupled to the transmit circuit and the receive circuit, wherein the processing circuit is configured to determine the distance of an object based on the received first complementary sequence pair and the received second complementary sequence pair.

[0007] According to the description, an exemplary device for performing radio frequency (RF) sensing using spatio-temporal frequency multiplexing (STFM) includes means for performing a transmit sequence. The means for performing the transmit sequence includes means for wirelessly transmitting a first sequence in a first complementary sequence pair using a first frequency, and means for wirelessly transmitting a first sequence in a second complementary sequence pair using a second frequency after wirelessly transmitting the first sequence in the first complementary sequence pair. The means for performing the transmit sequence further includes means for wirelessly transmitting a second sequence in the first complementary sequence pair using the first frequency after wirelessly transmitting the first sequence in the second complementary sequence pair, and means for wirelessly transmitting a second sequence in the second complementary sequence pair using the second frequency after wirelessly transmitting the second sequence in the first complementary sequence pair. The device further includes means for performing a receive sequence, including means for receiving the first complementary sequence pair and means for receiving the second complementary sequence pair. The device further includes means for determining the distance of an object based on the received first complementary pair and the received second complementary pair.

[0008] According to the description, a non - transitory computer - readable medium storing instructions for performing radio - frequency (RF) sensing using spatio - temporal frequency multiplexing (STFM). When the instructions are executed by one or more processing units, the one or more processing units are caused to execute a transmission sequence that includes: wirelessly transmitting a first sequence in a first complementary sequence pair using a first frequency; after wirelessly transmitting the first sequence in the first complementary sequence pair, wirelessly transmitting a first sequence in a second complementary sequence pair using a second frequency; after wirelessly transmitting the first sequence in the second complementary sequence pair, wirelessly transmitting a second sequence in the first complementary sequence pair using the first frequency; and after wirelessly transmitting the second sequence in the first complementary sequence pair, wirelessly transmitting a second sequence in the second complementary sequence pair using the second frequency. When the instructions are executed by one or more processing units, the one or more processing units are also caused to execute a reception sequence that includes receiving the first complementary sequence pair and receiving the second complementary sequence pair. When the instructions are executed by one or more processing units, the one or more processing units are also caused to determine the distance of an object based on the received first complementary sequence pair and the received second complementary sequence pair. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] Figure 1 is a block diagram of a Golay processing module, showing how complementary sequences are processed to provide an impulse response without sidelobes.

[0010] Figure 2 is an illustration of a spatio - temporal frequency multiplexing (STFM) scheme according to a first embodiment.

[0011] Figure 3 is an illustration of an STFM scheme according to a second embodiment.

[0012] Figure 4 is a block diagram of components of an STFM radar system capable of providing the functions described herein according to some embodiments.

[0013] Figure 5 is an illustration of an embodiment of an analog phase - array radar.

[0014] Figure 6 is a flowchart of a method for RF sensing of an object using STFM according to an embodiment.

[0015] Figure 7 is a block diagram of an embodiment of an electronic device.

[0016] According to some exemplary embodiments, like reference numerals in the various figures indicate like elements. Additionally, multiple instances of an element may be denoted by following the first digit of the element with a letter or a hyphen and a second digit. For example, multiple instances of element 110 may be denoted as 110-1, 110-2, 110-3, etc. or as 110a, 110b, 110c, etc. When only the first digit is used to refer to such an element, it should be understood to refer to any instance of the element (e.g., element 110 in the previous example would refer to elements 110-1, 110-2, and 110-3 or to elements 110a, 110b, and 110c). Detailed Description

[0017] Several illustrative embodiments will now be described with reference to the accompanying figures which form a part hereof. The following description provides only embodiments and is not intended to limit the scope, applicability, or configuration of the present disclosure. Rather, the following description of the embodiments will provide those skilled in the art with a useful description for implementing the embodiments. It should be understood that various changes may be made to the functions and arrangements of the elements without departing from the spirit and scope of the present disclosure.

[0018] It should also be further noted that while the embodiments described herein are described in the context of automotive applications, the embodiments are not limited thereto. The embodiments may be used in other object sensing applications (e.g., sensing of the position, distance, speed, etc. of an object). Additionally, the embodiments herein generally relate to the use of millimeter wave (mmWave) radar technology, which typically operates at 76 to 81 GHz and may more broadly operate from 30 to 300 GHz. That is, depending on the desired functionality, manufacturing concerns, and / or other factors, the embodiments may use higher and / or lower RF frequencies.

[0019] As used herein, the terms "waveform," "sequence," and their derivatives are used interchangeably to refer to radio frequency (RF) signals generated by the transmitter of a radar system and received by the receiver of the radar system for object detection. "Pulse" and its derivatives are generally referred to herein as complementary sequence pairs. Additionally, the terms "transmitter," "Tx," and their derivatives are used to describe the components of a radar system that are used to form and / or transmit RF signals. (As described in further detail below, this may include hardware and / or software components such as a processor, a dedicated circuit, and one or more antennas.) Similarly, the terms "receiver," "Rx," and their derivatives are used to describe the components of a radar system that are used to receive and / or process RF signals. (Again, this may include hardware and / or software components such as a processor, a dedicated circuit, and one or more antennas.)

[0020] As previously mentioned, due to its reliability in adverse weather and lighting conditions, radar technology is particularly useful in automotive applications. However, the rapid development of autonomous driving technology has posed new requirements and has prompted modern automotive radar systems to evolve from classical object detection sensors to ultra-high-resolution imaging devices with object recognition and classification capabilities. For example, these future radar systems can provide 4D radar images (which provide images of the distance, azimuth, elevation, and velocity of an object) for autonomous vehicles at a real-time refresh rate of 30 frames per second.

[0021] Typical specifications of automotive imaging radars include, for example, a large range coverage of 300 meters, a wide field of view (FOV) of 90 degrees, a large velocity range of ±50 m / s, a high range resolution of 0.5 meters, an angular resolution of 1 degree, and a Doppler resolution of 0.5 m / s. To meet these very demanding requirements of the automotive industry, next-generation radar systems are typically equipped with very large transmit and receive antenna arrays with hundreds of elements and use high-bandwidth signals (about 1 GHz), short pulse repetition intervals of about 20 μs, and long observation times of about 4 ms.

[0022] Today's state-of-the-art radar sensors use chirp sequence modulated pulses (such as frequency-modulated continuous-wave radar (FMCW)) and full-digital multiple-input multiple-output (MIMO) radar systems that have multiple high-speed analog-to-digital converters (ADCs) and digital-to-analog converters (DACs) and the ability to transmit different signals simultaneously from each transmit antenna and receive simultaneously on all receive antennas. However, this may require expanding existing MIMO radars from a few transmitter / receiver (Tx / Rx) chains to dozens or hundreds of Tx / Rx chains. This requires more hardware, and the increase in hardware cost and the accompanying complexity may make this approach practically unfeasible.

[0023] Alternative, more cost-effective techniques, such as analog phased array beam scanning, hybrid beamforming, and time-division multiplexing MIMO, use time-division multiplexing methods to significantly reduce the number and complexity of Tx / Rx chains, but at the cost of slower scanning times. Unfortunately, chirp sequences are typically long (tens of microseconds), so time-division multiplexing methods may not be able to meet the high Doppler resolution requirements (where the movement is determined by transmitting multiple pulses in a single direction) and the radar frame rate requirements. (For example, a 90° FOV with 1° resolution may require transmitting pulses in 90 different directions.)

[0024] The embodiments provided herein address these and other problems by using a much shorter complementary pair-based radar waveform (e.g., about 1 μs) length and efficient spatio-temporal frequency multiplexing. This provides a fast scan of sectors, antennas, or subarrays, thus enabling a more practical and cost-effective radar solution with a much smaller number of Tx / Rx chains. Specifically, short complementary pairs of phase-coded waveforms (e.g., Golay complementary sequences) can be used, together with time and frequency degrees of freedom, for efficient multiplexing and fast scanning of different antennas and / or sectors in a massive MIMO radar system.

[0025] An attractive property of complementary waveforms is that the sum of their autocorrelation functions equals a perfect impulse response function, thus achieving zero range side lobes. Figure 1 FIG. 100 is a block diagram of Golay processing 100, showing how a Golay binary complementary sequence (also referred to herein as a "Golay pair" or "complementary pair") can be processed by a receiver (Rx) of a radar system to provide an impulse response without side lobes. As will be understood by those of ordinary skill in the art, Golay processing 100 is a form of digital signal processing that can be implemented by hardware and / or software at, for example Figure 4 the receiver (Rx) of the radar system shown.

[0026] Here, the Golay pair includes a first sequence Ga and a second sequence Gb. Golay processing 100 includes autocorrelating the Ga sequence and the Gb sequence using a Ga correlator 110-1 and a Gb correlator 110-2, respectively. Then, summation 120 is performed on the output of each correlator to provide an output 130: a perfect impulse response without side lobes. To utilize this complementary property of radar pulses, the sequences Ga and Gb can be transmitted separately in time such that the time interval between the two transmissions is greater than the round-trip delay to the farthest object. Otherwise, the cross-correlation between the long target echoes of the first sequence and the second transmitted sequence will destroy the zero side lobe property.

[0027] With this in mind, the embodiments described herein can utilize this idle time between complementary sequences and use orthogonal frequency subbands and different Tx antenna / sector configurations to transmit additional complementary sequence pairs. This can efficiently and quickly scan the Tx antenna / sectors in an almost zero-overhead manner. Switching the Tx antenna / sector configuration means that the same Tx chain / DAC can be reused and / or connected to different antennas or analog sectors, thus reducing the number of required Tx chains / DACs.

[0028] Since the Rx side must wait for the round-trip delay to receive the longest echo before the Rx antenna / sector configuration can be changed, fast switching (similar to the Tx antenna / sector) may not be feasible for the Rx antenna / sector. That is, any switching of the Rx antenna / sector has a significant penalty time equal to the round-trip delay to the farthest target (usually, the maximum round-trip delay is longer than the Golay pulse). Therefore, according to many embodiments, the switching of the Rx antenna / sector can be minimized. In some cases, for example, the Rx antenna / sector may only occur as frequently as needed. That is, due to other factors, some embodiments may involve frequent switching of the Rx antenna / sector.

[0029] Figure 2 FIG. 4 is an illustration of a space-time frequency multiplexing (STFM) scheme 200 according to an embodiment. As shown, the horizontal axis represents time. The vertical axis represents the Tx frequency 210, the Tx radio sector 220, the Rx radio sector 230, the Rx frequency 240, and the Rx multi-band correlation period 250 (for each frequency). For this example, it can be assumed that an analog phased array radar system is used to scan all Tx and Rx sectors to obtain a radar image. It can be understood that the number of TX and / or RX sectors that determine the output data resolution can vary according to the required function.

[0030] In Figure 2 the symbols are as follows:

[0031] Ga, Gb – Golay sequence pairs

[0032] Tg – single Golay sequence duration

[0033] Trtd – round-trip delay corresponding to the farthest object (defining the shortest duration of the idle period between two complementary Golay pulses)

[0034] Tpulse – Golay pair pulse interval (equal to twice the Golay duration and twice the idle time)

[0035] Doppler PRI – pulse repetition interval of the same Tx / Rx sector for target velocity estimation

[0036] Tburst – burst interval (a burst is a sequence of pulses for velocity estimation)

[0037] Ts – transmit sector

[0038] Rs – receive sector

[0039] The Golay pairs Ga and Gb are transmitted as shown in the Tx frequency 210 figure. It can be seen that the idle time Trtd between the Ga and Gb sequences can be approximately equal to the duration of a single Ga / Gb pulse to help maximize the efficiency of the STFM scheme 200. (However, in alternative embodiments, this may not be the case.) Thus, as shown, two Golay pairs can be efficiently time-division multiplexed to scan two Tx sectors in one pulse duration Tpulse. As shown in the Tx radio sector 220 figure, Tx sectors TS1 and TS2 are scanned during the first pulse duration, and Tx sectors TS3 and TS4 are scanned during the second pulse duration. Thus, one or more different antennas can be used during the first and second pulse durations.

[0040] Also as shown in the Tx frequency 210 figure, different Golay pairs are transmitted on separate frequency sub-bands f1 and f2 to avoid cross-correlation interference between the two pairs on the Rx side. Here, the time-division multiplexed pairs in Tx do not overlap in time and do not need to be orthogonal to each other, but the transmitted pulses may reflect from multiple different targets and thus may arrive at the receiver at overlapping times. Thus, according to some embodiments, Ga and Gb in one pair can be orthogonal to both Ga and Gb in a second pair.

[0041] Transmitting the Golay pairs in this orthogonal manner can be similar to true MIMO, where two orthogonal signals are transmitted simultaneously and then separated on the receiver side. However, in the STFM scheme 200, a single Tx chain can be used together with time interleaving to transmit two different pulses and achieve the same MIMO effect on the Rx side. Then, the Rx side may receive (overlap) two orthogonal signals simultaneously and thus may need to separate between them.

[0042] As previously mentioned, the sectors can be scanned multiple times for Doppler determination (e.g., movement of any detected object). In some embodiments, for example, 100 to 200 pulses can be sent in a single direction for Doppler determination. (In other words, the Golay pairs can be sent 100 to 200 times using the same Tx and Rx radio sectors, resulting in a Tburst time that is 100 to 200 times longer than Tpulse.) However, in other embodiments, more or fewer pulses can be sent. (Some embodiments may not require Doppler determination and thus these repeated scans can be omitted.) The frequency of scanning the sectors can determine the maximum speed that the radar system can clearly estimate. In Figure 2In the STFM scheme 200, the Doppler pulse repetition interval (PRI) is twice the duration Tpulse of the Golay pair. Therefore, two additional Golay pairs can be time-division multiplexed and transmitted, enabling the scanning of four Tx sectors (TS1, TS2, TS3, and TS4) within a single Doppler PRI. In contrast, in the typical case of an FMCW automotive radar, only a single pulse can be transmitted within a single Doppler PRI interval. Thus, Figure 2 the STFM scheme 200 shown in Figure 2 results in a beam scan that is four times faster than that of a typical FMCW automotive radar.

[0043] Continuing Figure 2 with the STFM scheme 200 shown in Figure 2 , the pattern of multiplexing the four Tx sectors is repeated to scan all available Tx sectors while maintaining the same Rx sector. The amount of times each sector is scanned can vary depending on the desired functionality. As previously mentioned, some embodiments can scan each sector only once if Doppler determination is not required. Other embodiments, including those that do provide Doppler determination, can scan each sector multiple times. The scan of all Tx radio sectors (which, as previously mentioned, can include transmitting / receiving multiple pulses in a single direction) is referred to as a "burst", and the time required to complete this burst is denoted as Tburst in Figure 2 Figure 2 . (In some embodiments, Tburst can be, for example, 2 ms or 4 ms. However, alternative embodiments can have longer or shorter Tburst periods.) The amount of bursts required to scan the entire scan region (e.g., 90° FOV) can depend on factors such as the number of Tx radio sectors scanned per burst and the number of Tx and Rx radio sectors used to scan the region.

[0044] As previously mentioned, based on the round-trip delay of the longest reflection path within the region scanned by the radar system, there is a certain overhead Trtd for switching between Rx sectors. Therefore, the switching between Rx sectors can be minimized to reduce this overhead. In the STFM scheme 200, once all Tx sectors have been scanned, the switching between Rx sectors occurs. Once the Rx sector has been switched (e.g., from RS1 to RS2), the Tx sectors can be scanned in a similar manner. Additionally, time can be allocated for the overhead of switching between Rx sectors. That is, after transmitting the last pulse of the last Tx sector burst, as shown in Figure 2 Figure 2 , a Rx sector switch overhead period 255 of length Trtd can be allocated to wait for all echoes of the last transmitted sequence in the first one to be received before switching to the next Rx sector.

[0045] The illustration of Rx frequency 240 shows the received Ga sequence 260 and the received Gb sequence 265 (shown side by side with the transmitted sequences). (To avoid clutter, only a portion of the received Ga sequence 260 and the received Gb sequence 265 are labeled.) Here, the received Ga sequence 260 and the Gb sequence 265 are delayed and attenuated. The amount of delay depends on the distance of the object reflecting the corresponding transmitted signal, and the amount of attenuation can depend on various factors, including the distance and composition of the object. As shown, the reception of the sequence can start before the transmission of the sequence is complete (again, based on the distance of the object).

[0046] The illustration of the Rx multi-band correlation period 250 shows how multiple correlators can be used to process in parallel the pulses received at different frequencies. That is, the GA correlator can operate during the period Tg of the transmitted sequence and during the period Trtd, thus allowing for the maximum round-trip delay. This helps to ensure detection of objects both far and near to the radar system. Once the period of the Ga correlator is complete, the Gb correlator can be used to detect the reflection of the transmitted Gb sequence. It can be seen that the operating periods of the Ga correlator and the Gb correlator can be offset for each frequency (f1 and f2), corresponding to the offset in the transmission of the Ga sequence and the Gb sequence between the two frequencies.

[0047] By using time-frequency multiplexing of more Golay pairs, this idea can be easily extended to more than two frequency bands. Figure 3 An example of this is shown in

[0048] Figure 3 is a diagram showing the STFM scheme 300, which shows four-pulse multiplexing (i.e., using Golay pairs at four frequencies). Similar to Figure 2 , the horizontal axis represents time, and the vertical axis represents the Tx frequency 310, the Tx radio sector 320, the Rx radio sector 330, the Rx frequency 340, and the Rx multi-band correlation period 350 (for each frequency). However, here, the idle time Trtd between the two transmitted complementary sequences Ga and Gb is approximately equal to three times the duration Tg of a single Ga / Gb sequence. Thus, four Golay pairs can be efficiently time-frequency multiplexed to scan four Tx sectors (TS1 to TS4) in one pulse duration Tpulse and eight Tx sectors in one Doppler PRI, so the STFM scheme 300 can perform Tx radio sector scanning 8 times faster than a traditional FMCW automotive radar.

[0049] It can be noted here that four orthogonal frequency sub-bands (f1 to f4) are used to achieve orthogonality between Ga and Gb of all four Golay pairs. By using shorter pulses, additional frequencies, and / or shorter intervals between Ga and Gb, additional beam scanning acceleration can be obtained. Although additional correlators may be required at the Rx to perform parallel correlation, the Tx still only transmits one time pulse. Thus, in many embodiments, using many frequencies in an STFM scheme such as Figure 3 the STFM scheme 300 may be a cost-effective solution.

[0050] In Figure 3 , the received Ga sequence 360 and the received Gb sequence 365 are shown in the Rx frequency 340. (Again, for clarity, only a portion of the received Ga sequence 360 and the received Gb sequence 365 are labeled.) Similar to the received sequences in Figure 2 , these received sequences may overlap. Thus, signals received at different frequencies can be processed in parallel. The parallel processing of various Golay pairs at frequencies f1 to f7 is shown in the Rx multi-band correlation period 350.

[0051] It can be noted that Figure 3 (and subsequent figures) show multiple received Ga sequences 360 and received Gb sequences 365, which correspond to a single respective transmitted Ga or Gb sequence. This is to illustrate that multiple reflected signals may occur due to the transmitted signal being reflected by multiple targets in the illuminated sector. (Although not shown in Figure 2 , this phenomenon may also occur in this embodiment.) In addition, the reflected signals may overlap with each other and / or with the transmitted signal.

[0052] Figure 4 is a block diagram of the components of an STFM radar system 400 capable of providing the functions described herein. The STFM radar system 400 includes an analog phased array radar having a single-chain / DAC transmitter 402 and a single-chain / ADC receiver 404, although alternative embodiments may use different types of phased array radars depending on the required functions and may include multi-chain / DAC transmitters and / or multi-chain / ADC receivers.

[0053] In the transmitter 402, the multi-band pulse generator 405, DAC 410, mixer 415, RF Tx amplifier 420, and phase shifter array 425 operate to transmit Ga and Gb pulses at four frequencies, as shown in the Tx spectrogram 430 (similar to Figure 3The STFM scheme 300). More specifically, the time-frequency multiplexed signal can be digitally generated by the multi-band pulse generator 405, converted to an analog signal using a single wideband DAC 410, and then mixed to the RF frequency using the mixer 415.

[0054] Tx analog sector switching can be synchronized with the timing of the pulses to achieve the desired STFM scheme. The input Tx sector configuration 445 can be used to control this sector switching. A processing unit or other hardware and / or software components (not shown) can be used to provide input to the Tx sector configuration 435 and can be communicatively coupled with the multi-band pulse generator 405 and / or other components to help ensure the synchronization of the Tx sector switching. Finally, Figure 4 The Tx chain (multi-band pulse generator 405, DAC 410, mixer 415, RF Tx 420, and phased array 425) in the illustrated embodiment operates to generate a beam scanning pattern in which four multiplexed sectors are scanned using four different frequency sub-bands (f1 - f4).

[0055] In Figure 4 the RF signal generated by the scan is reflected by the object 445 and received at the phased array 450. As Figure 2 and Figure 3 shown, a single Rx sector can be used during the scan of multiple Tx sectors. Similarly, Figure 4 shows that a single Rx sector is used to receive signals from the beam scanning pattern of four multiplexed Tx sectors.

[0056] The phased array 450 works together with the RF Rx amplifier 455, mixer 460, ADC 465, and bandpass filter bank 470 to separate the received Golay pairs, as shown in the Rx spectrogram 475. More specifically, the signal received at the phased array 450 is amplified by the RF Rx amplifier 455, down-converted to the baseband using the mixer 460, and sampled using a single wideband ADC 465. Since the multi-target reflections at each Tx sector are different, the echoes of the four pulses may overlap. Therefore, the Rx signal passes through the bandpass filter bank for orthogonal signal separation. Similar to the phased array 425 used for Tx, an input for the Rx sector configuration 473 can be used to manage the configuration of the phased array 450 for Rx.

[0057] As shown, parallel processing 475 can occur on all four received pulses. That is, different Golay correlators are applied simultaneously (at overlapping times) to the pulses received at different frequencies to extract four correlator profiles, one for each of the four Tx sectors (e.g., as Figure 3 shown in the Rx multi-band correlation periodogram 350 of Figure 1As shown, the sum of the autocorrelations of the Ga sequence and the Gb sequence (e.g., performed by a summing module) can generate the channel impulse response (CIR) for each of the four Tx sectors. As will be understood by those skilled in the art, the range (distance), azimuth, elevation, and / or velocity of one or more objects in the scan area can then be determined based on the channel impulse responses of the Tx / Rx sectors.

[0058] For example, in an analog phased array radar where Tx is used for azimuth scanning and Rx is used for elevation scanning, it is possible to scan the Tx sector while maintaining the same Rx sector. Figure 5 An illustration of an embodiment of such an analog phased array radar is shown.

[0059] As Figure 5 shown, the analog phased array radar 500 includes a horizontal Tx antenna array 510. (Examples of the Tx antenna array 510 are shown as a single-row figure and a 2-row by 8-column array in Figure 5 .) The analog phased array radar 500 also includes a vertical Rx antenna array 520. (Examples of the Rx antenna array 520 are shown as a single-column figure and an 8-row by 2-column array in Figure 5 .) This arrangement makes the Tx sector narrow in the azimuth direction and wide in the elevation direction. In contrast, the Rx sector is wide in the azimuth direction and narrow in the elevation direction. Thus, by maintaining the same Rx elevation sector (as Figures 2 to 4 shown), all Tx azimuth sectors can be scanned.

[0060] The proposed STFM method can be efficiently used to accelerate radar scanning in various large-scale MIMO radar architectures, where time division multiplexing is applied in Tx to reduce the hardware complexity of the radar system. It includes analog phased arrays, time division multiplexing (TDM) MIMO, and various analog-digital hybrid beamforming (BF) schemes.

[0061] Figure 6 is a flowchart of a method 600 for RF sensing of an object using STFM according to an embodiment. Method 600 captures a portion of the functionality described in the above embodiments and shown in Figures 2 to 5 . Figure 6 One or more of the functions described in the blocks shown in Figure 7 can be performed by software and / or hardware components (e.g., a digital signal processor (DSP)) of an electronic device (such as the electronic device shown in Figure 4 and described below) and / or one or more components shown in Figure 7 that can be incorporated into the electronic device shown in Figure 6 . Additionally, those of ordinary skill in the art will understand that alternative embodiments can be achieved by adding, omitting, combining, separating, and otherwise changing theFigure 6 Variations in the manner of these functions as shown.

[0062] At block 610, the function includes performing a transmission sequence at least in part by performing the functions described in blocks 610-a through 610-d. The function at block 610-a includes wirelessly transmitting a first sequence in a first complementary sequence pair using a first frequency. At block 610-b, the function includes, after wirelessly transmitting the first sequence in the first complementary sequence pair, wirelessly transmitting a first sequence in a second complementary sequence pair using a second frequency. At block 610-c, the function includes, after wirelessly transmitting the first sequence in the second complementary sequence pair, wirelessly transmitting a second sequence in the first complementary sequence pair using the first frequency. At block 610-d, the function includes, after wirelessly transmitting the second sequence in the first complementary sequence pair, wirelessly transmitting a second sequence in the second complementary sequence pair using the second frequency. As previously mentioned, complementary sequences or Golay pairs can provide an impulse response after each sequence is individually autocorrelated, and then the autocorrelations of each resulting sequence are summed together. This is particularly useful for determining the distance to an object. Additionally, because complementary sequences are relatively short (compared to FMCW scans), embodiments may be able to transmit multiple Golay pairs (pulses) in a shorter time than it would take to complete a scan using FMCW radar. The time between the transmission of the first and second sequences of each complementary pair can be based on the maximum round-trip delay between the transmitter and an object at the maximum distance to be scanned.

[0063] Components for performing the function at block 610 can include, for example, a multi-band pulse generator 405, a DAC 410, a mixer 415, an RF Tx 420, a phase shifter array 425, and one or more antennas, as Figure 4 shown and described above. Additionally, one or more of these components can be included in a communication subsystem 730 (including a wireless communication interface 733) and / or other hardware and / or software components of the electronic device 700, as Figure 7 shown and described in further detail below.

[0064] The functions of the embodiments can vary, as pointed out in the above description. Because the complementary pairs are orthogonal, the first complementary sequence pair can have the same values as the second complementary sequence pair. (That is, the first complementary sequence pair is the same as the second complementary sequence pair, but transmitted orthogonally.) First additionally or alternatively, as Figures 2 to 4 shown, different complementary sequence pairs can be used to scan different Tx sectors. That is, the first complementary sequence pair can be transmitted in a first direction, while the second complementary sequence pair can be transmitted in a second direction.

[0065] This can be extended to more than two directions. For example, as Figure 2As shown, some embodiments can perform scanning in four directions using two frequencies. In this case, the function of executing the transmission sequence as shown in Figure 6 box 610 of can further include wirelessly transmitting the first sequence in the third complementary sequence pair along the third direction using the first frequency, and after wirelessly transmitting the first sequence in the third complementary sequence pair, wirelessly transmitting the first sequence in the fourth complementary sequence pair along the fourth direction using the second frequency. Executing the transmission sequence can further include, after wirelessly transmitting the first sequence in the fourth complementary sequence pair, wirelessly transmitting the second sequence in the third complementary sequence pair along the third direction using the first frequency, and after wirelessly transmitting the second sequence in the third complementary sequence pair, wirelessly transmitting the second sequence in the fourth complementary sequence pair along the fourth direction using the second frequency.

[0066] Embodiments can also use more than two frequencies. For example, some embodiments, such as Figures 3 to 4 the embodiments shown, can perform scanning in four directions using four frequencies. In this case, the function of executing the transmission sequence as shown in Figure 6 box 610 of can further include transmitting the third complementary sequence pair using the third frequency and transmitting the fourth complementary sequence pair using the fourth frequency. As further indicated in the embodiments of Figures 3 to 4 , wirelessly transmitting the first sequence in the third complementary sequence pair and transmitting the first sequence in the fourth complementary sequence pair can occur after wirelessly transmitting the first sequence in the second complementary sequence pair and before wirelessly transmitting the second sequence in the first complementary sequence pair.

[0067] Referring again to Figure 6 , method 600 further includes performing a reception sequence at block 620 at least in part by executing the functions at blocks 620-a and 620-a. At block 620-a, the function includes receiving the first complementary sequence pair, and at block 620-b, the function includes receiving the second complementary sequence pair.

[0068] The components for performing the functions at block 620 can include, for example, one or more antennas, a phase shifter array 450, an RF Rx 455, a mixer 460, an ADC 465, a bandpass filter bank 470, and parallel processing 475, as Figure 4 shown and described above. In addition, one or more of these components can be included in the communication subsystem 730 (including the wireless communication interface 733) and / or other hardware and / or software components of the electronic device 700, as Figure 7 shown and described in further detail below.

[0069] At block 630, the functionality includes determining the distance of an object based on a received first complementary pair and a received second complementary pair. As noted in the above embodiments, the distance can be determined based on the time at which either or both of the first complementary pair and the second complementary pair are transmitted and received (e.g., the calculated round-trip time). The time at which a pulse is received can be determined by generating a pulse response as shown in Figure 1 , by performing autocorrelation on each sequence in the pair and then summing the autocorrelations of the two sequences in the pair. The pulse response for each pair can be determined using parallel processing 475, as shown in Figure 4 . This can be implemented in hardware and / or software. Thus, the components for performing the functionality at block 630 can include, for example, a module configured to perform the parallel processing 475 of Figure 4 , as described above. The module can be implemented in hardware (e.g., a dedicated circuit) and / or software (e.g., software executed by a processing unit), which can be included in the communication subsystem 730 (including the wireless communication interface 733), the processing unit 710, and / or other hardware and / or software components of the electronic device 700, as shown in Figure 7 and described in further detail below.

[0070] As previously noted herein and as shown in Figure 4 , embodiments provide for the use of a single Tx and / or Rx chain. This is particularly helpful for fabricating low-cost RF sensing circuits capable of implementing the STFM scheme detailed herein. Thus, the transmit sequence of block 610 can be performed using a transmit circuit having a single DAC. Additionally or alternatively, the receive sequence of block 620 can be performed by a receive circuit having a single ADC. However, other embodiments can utilize multiple Tx and / or Rx chains.

[0071] Some embodiments can allow for the determination of Doppler information of a detected object by transmitting multiple pulses in a single direction (each pulse including the transmission of a complementary sequence pair). Thus, method 600 can also include performing the transmit sequence and the receive sequence multiple times in succession. In some embodiments, multiple Tx sectors can be scanned during each transmit sequence. In such cases, the Doppler PRI can be based on the total amount of time required to transmit a pulse in each direction.

[0072] Figure 7 An embodiment of an electronic device 700 is shown, which can be capable of performing RF sensing using the STFM described in the above embodiments, including one or more functions of the method described in Figure 6 . As previously described, the components shown in Figure 4 can be incorporated into one or more hardware elements of the electronic device 700, such as the communication subsystem 730.

[0073] It should be noted that Figure 7It is only intended to provide a generalization of the various components and any or all of them may be utilized as appropriate. Thus, Figure 7 it is shown broadly how individual system elements may be implemented in a relatively separated or relatively more integrated manner. Additionally, it may be noted that Figure 7 the components shown may be localized to a single device and / or distributed among various networked devices, which may be located in different physical locations (e.g., different locations in an automobile). For automotive applications, electronic device 700 may include an in-vehicle computer of the automobile.

[0074] Electronic device 700 is shown as including hardware elements that may be electrically coupled (or may communicate in other ways as appropriate) via bus 705. The hardware elements may include a processing unit 710, which may include but is not limited to one or more general-purpose processors, one or more dedicated processors (such as a digital signal processor (DSP), a graphics processing unit (GPU), an application-specific integrated circuit (ASIC), a field-programmable gate array (FPGA), etc.) and / or other processing structures, which may be configured to perform one or more functions of the methods described herein, including Figure 6 the methods shown therein. Electronic device 700 may also include: one or more input devices 715, which may include but are not limited to a touchscreen display or other user interface, one or more automation systems for an autonomous vehicle, etc.; and one or more output devices 720, which may include but are not limited to a display device, one or more automation systems for an autonomous vehicle, etc.

[0075] Electronic device 700 may also include (and / or communicate with) one or more non-transitory storage devices 725, which may include but are not limited to local and / or network-accessible storage, and / or may include but are not limited to a disk drive, an array of drives, an optical storage device, a solid-state storage device (such as random access memory (RAM)) and / or read-only memory (ROM), which may be programmable, flash-updatable, etc. Such storage devices may be configured to implement any suitable data storage, including but not limited to various file systems, database structures, etc.

[0076] The electronic device 700 may also include a communication subsystem 730, which may include support for wired communication technologies and / or wireless communication technologies (in some embodiments) managed and controlled by a wireless communication interface 733. The communication subsystem 730 may include a modem, a network card (wireless or wired), an infrared communication device, a wireless communication device, and / or a chipset, etc. The communication subsystem 730 may include one or more input and / or output communication interfaces, such as the wireless communication interface 733, to allow for the exchange of data and signaling with a network, a mobile device, other computer systems, and / or any other electronic device described herein. As previously mentioned, Figure 4 one or more of the components shown in Figure 4 may be incorporated into a wireless communication interface 733 capable of RF sensing as well as communication according to the embodiments provided herein. In other embodiments,

[0077] In many embodiments, the electronic device 700 also includes a working memory 735, which may include RAM and / or ROM devices. Software elements shown to be located within the working memory 735 may include an operating system 740, device drivers, executable libraries, and / or other code, such as an application 745, which may include computer programs provided by various embodiments, and / or may be designed to implement methods and / or configure systems provided by other embodiments, as described herein. By way of example only, one or more of the functions described with respect to the above methods (such as with respect to Figure 6 the methods described) may be implemented as (e.g., temporarily) stored in the working memory 735 and executable by a computer (and / or a processing unit within the computer, such as the processing unit 710); then, in one aspect, such code and / or instructions may be used to configure and / or adapt a general-purpose computer (or other device) to perform one or more operations in accordance with the method.

[0078] This set of instructions and / or code may be stored on a non-transitory computer-readable storage medium, such as the storage device 725 described above. In some cases, the storage medium may be incorporated into a computer system, such as the electronic device 700. In other embodiments, the storage medium may be separate from the computer system (e.g., a removable medium, such as an optical disc), and / or may be provided in an installation package such that the storage medium may be used to program, configure, and / or adapt a general-purpose computer with the instructions / code stored thereon. These instructions may be in the form of executable code executable by the electronic device 700, and / or may be in the form of source code and / or installable code, which, when compiled and / or installed on the electronic device 700 (e.g., using any of a variety of general compilers, installers, compression / decompression utilities, etc.), takes the form of executable code.

[0079] It can be noted that although the present document may provide specific frequencies, hardware, and other features in the embodiments, alternative embodiments may vary. That is, alternative embodiments may utilize additional or alternative frequencies, antenna elements (e.g., an array of antenna elements having different sizes / shapes), frame rates, electronic devices, and / or other features described in the embodiments herein. A person of ordinary skill in the art will understand such variations.

[0080] A person of ordinary skill in the art will further understand that various aspects of the embodiments described herein can be implemented in various ways. For example, pulse generation, correlation, and / or other types of signal generation and / or processing can be implemented in hardware, software (e.g., firmware), or both. Additionally, the hardware and / or software functions can be distributed among different components and / or devices.

[0081] The embodiments provided herein can be used for autonomous driving and / or other applications. Generally, Figure 4 the architectures shown can be incorporated into any of a variety of different types of computing devices and / or systems. These devices / systems typically may include a processing unit (which may include, for example, a general-purpose processor, a dedicated processor (such as a digital signal processing (DSP) chip, a graphics acceleration processor, an application-specific integrated circuit (ASIC), etc.), and / or other processing structures or components); an input device (which may include, for example, a keyboard, a touch screen, a touchpad, a microphone, buttons, a dial pad, switches, etc.); an output device (which may include, for example, a display, a light-emitting diode (LED), an audio speaker, etc.); a communication bus that communicatively couples the various components of the electronic device together; a communication interface; and so on.

[0082] The foregoing memory may include non-transitory machine-readable media. As used herein, the terms “machine-readable medium” and “computer-readable medium” refer to any storage medium that participates in providing data that causes a machine to operate in a particular manner. In the embodiments provided above, various machine-readable media may be involved in providing instructions / code to the processing unit and / or other devices for execution. Additionally or alternatively, the machine-readable medium may be used to store and / or carry such instructions / code. In many implementations, the computer-readable medium is a physical and / or tangible storage medium. Such media may take many forms, including but not limited to non-volatile media, volatile media, and transmission media. Common forms of computer-readable media include, for example, magnetic and / or optical media, RAM, PROM, EPROM, FLASH-EPROM, any other storage chip or cartridge, and / or any other medium from which a computer can read instructions and / or code.

[0083] The methods, systems, and devices discussed in this document are examples. Various embodiments may omit, substitute, or add various processes or components as appropriate. For example, the features described with respect to certain embodiments may be combined in various other embodiments. The different aspects and elements of the embodiments may be combined in a similar manner. The various components of the figures provided herein may be embodied in hardware and / or software. Additionally, technology is evolving, and as such, many of the elements are examples and do not limit the scope of the disclosure to those specific examples.

[0084] Primarily for general reasons, it has proven convenient at times to refer to such signals as bits, information, values, elements, symbols, characters, variables, terms, numbers, numerals, etc. However, it should be understood that all such or similar terms should be associated with appropriate physical quantities and are merely convenient labels. Unless otherwise specifically stated, as will be apparent from the above discussion, it should be understood that throughout this specification, terms such as "processing," "computing," "accounting," "determining," "ascertaining," "identifying," "associating," "measuring," "performing," etc., refer to the actions or processes of a specific apparatus (such as a special-purpose computer or similar special-purpose electronic computing device). Thus, in the context of this specification, a special-purpose computer or similar special-purpose electronic computing device is capable of manipulating or transforming signals that are typically represented as physical, electronic, electrical, or magnetic quantities in a memory, register, or other information storage device, transmission device, or display device of the special-purpose computer or similar special-purpose electronic computing device.

[0085] The terms "and" and "or" as used herein may include a variety of meanings, which are also expected to depend at least in part on the context in which these terms are used. Additionally, the term "one or more" as used herein may be used to describe any feature, structure, or characteristic in the singular or may be used to describe some combination of features, structures, or characteristics. However, it should be noted that this is merely an illustrative example and the claimed subject matter is not limited to this example. Further, if used to relate to a list such as A, B, or C, the term "at least one of..." may be interpreted to mean any combination of A, B, and / or C, such as A, AB, AA, AAB, AABBCCC, etc.

[0086] Several embodiments have been described, and various modifications, alternative constructions, and equivalents may be used without departing from the spirit of the disclosure. For example, the above elements may be merely components of a larger system, where other rules may take precedence over or otherwise modify the application of the various embodiments. Additionally, multiple steps may be taken before, during, or after considering the above elements. Thus, the above description does not limit the scope of the disclosure.

Claims

1. A method for radio frequency (RF) sensing using spatio-temporal frequency multiplexing (STFM): Execute a transmission sequence, which includes: Wirelessly transmit the first sequence in the first complementary sequence pair using a first frequency; After wirelessly transmitting the first sequence in the first complementary sequence pair, wirelessly transmit the first sequence in the second complementary sequence pair using a second frequency; After wirelessly transmitting the first sequence in the second complementary sequence pair, wirelessly transmit the second sequence in the first complementary sequence pair using the first frequency; And After wirelessly transmitting the second sequence in the first complementary sequence pair, wirelessly transmit the second sequence in the second complementary sequence pair using the second frequency; Execute a reception sequence, which includes: Receive the first complementary sequence pair, and Receive the second complementary sequence pair; and Wherein the first complementary sequence pair is wirelessly transmitted along a first direction, and the second complementary sequence pair is wirelessly transmitted along a second direction; executing the transmission sequence further includes: Wirelessly transmit the first sequence in a third complementary sequence pair along a third direction using the first frequency; After wirelessly transmitting the first sequence in the third complementary sequence pair, wirelessly transmit the first sequence in a fourth complementary sequence pair along a fourth direction using the second frequency; After wirelessly transmitting the first sequence in the fourth complementary sequence pair, wirelessly transmit the second sequence in the third complementary sequence pair along the third direction using the first frequency; and After wirelessly transmitting the second sequence in the third complementary sequence pair, wirelessly transmit the second sequence in the fourth complementary sequence pair along the fourth direction using the second frequency, Wherein the method further includes: Determine the distance of an object based on the received first complementary sequence pair, the received second complementary sequence pair, the received third complementary sequence pair, and the received fourth complementary sequence pair.

2. The method according to claim 1, wherein the first complementary sequence pair is the same as the second complementary sequence pair.

3. The method according to claim 1, further including continuously executing the transmission sequence and the reception sequence multiple times.

4. The method according to claim 1, wherein executing the transmission sequence further includes: Wirelessly transmit a third complementary sequence pair using a third frequency, and Wirelessly transmit a fourth complementary sequence pair using a fourth frequency; And Wherein wirelessly transmitting the first sequence in the third complementary sequence pair and wirelessly transmitting the first sequence in the fourth complementary sequence pair occur after wirelessly transmitting the first sequence in the second complementary sequence pair and before wirelessly transmitting the second sequence in the first complementary sequence pair.

5. The method according to claim 1, wherein the transmission sequence is executed using a transmission circuit having a single digital-to-analog converter (DAC).

6. The method according to claim 1, wherein the reception sequence is executed using a reception circuit having a single analog-to-digital converter (ADC).

7. A radar system for performing radio frequency (RF) sensing using spatio-temporal frequency multiplexing (STFM): A transmission circuit configured to execute a transmission sequence, which includes: Wirelessly transmit the first sequence in the first complementary sequence pair using a first frequency; After wirelessly transmitting the first sequence in the first complementary sequence pair, wirelessly transmit the first sequence in the second complementary sequence pair using a second frequency; After wirelessly transmitting the first sequence in the second complementary sequence pair, wirelessly transmit the second sequence in the first complementary sequence pair using the first frequency; and After wirelessly transmitting the second sequence in the first complementary sequence pair, wirelessly transmit the second sequence in the second complementary sequence pair using the second frequency; a receiving circuit configured to perform a receiving sequence, comprising: receiving the first complementary sequence pair, and receiving the second complementary sequence pair; and a processing circuit communicatively coupled to the transmitting circuit and the receiving circuit, wherein the transmitting circuit is further configured to: wirelessly transmit the first complementary sequence pair in a first direction, and wirelessly transmit the second complementary sequence pair in a second direction, the transmitting circuit is further configured to: wirelessly transmit the first sequence in a third complementary sequence pair in a third direction using the first frequency; after wirelessly transmitting the first sequence in the third complementary sequence pair, wirelessly transmit the first sequence in a fourth complementary sequence pair in a fourth direction using the second frequency; after wirelessly transmitting the first sequence in the fourth complementary sequence pair, wirelessly transmit the second sequence in the third complementary sequence pair in the third direction using the first frequency; and after wirelessly transmitting the second sequence in the third complementary sequence pair, wirelessly transmit the second sequence in the fourth complementary sequence pair in the fourth direction using the second frequency, wherein the processing circuit is configured to determine the distance of an object based on the received first complementary sequence pair, the received second complementary sequence pair, the received third complementary sequence pair, and the received fourth complementary sequence pair.

8. The radar system according to claim 7, wherein the transmitting circuit includes a multi-band pulse generator, a digital-to-analog converter DAC, a mixer, an amplifier, a phase shift array, and one or more antennas.

9. The radar system according to claim 7, wherein the transmitting circuit and the receiving circuit are configured to perform the transmitting sequence and the receiving sequence continuously multiple times.

10. The radar system according to claim 7, wherein the transmitting circuit is further configured to: transmit the third complementary sequence pair using a third frequency, and transmit the fourth complementary sequence pair using a fourth frequency; and wherein the transmitting circuit is further configured to wirelessly transmit the first sequence in the third complementary sequence pair and wirelessly transmit the first sequence in the fourth complementary sequence pair after wirelessly transmitting the first sequence in the second complementary sequence pair and before wirelessly transmitting the second sequence in the first complementary sequence pair.

11. The radar system according to claim 8, wherein the receiving circuit includes one or more antennas, a phase shifter array, an amplifier, a mixer, an analog-to-digital converter ADC, and a bandpass filter bank.

12. The radar system according to claim 11, wherein the processing circuit includes: correlators for each sequence in the first complementary sequence pair and each sequence in the second complementary sequence pair, A summation module for each of the first complementary sequence pair and the second complementary sequence pair, and a processing unit.

13. A device for radio frequency (RF) sensing using spatial-time frequency multiplexing (STFM): Components for performing a transmission sequence, including: Components for wirelessly transmitting a first sequence in a first complementary sequence pair using a first frequency; Components for wirelessly transmitting a first sequence in a second complementary sequence pair using a second frequency after wirelessly transmitting the first sequence in the first complementary sequence pair; Components for wirelessly transmitting a second sequence in the first complementary sequence pair using the first frequency after wirelessly transmitting the first sequence in the second complementary sequence pair; and and Components for wirelessly transmitting a second sequence in the second complementary sequence pair using the second frequency after wirelessly transmitting the second sequence in the first complementary sequence pair; Components for performing a reception sequence, including: Components for receiving the first complementary sequence pair, and Components for receiving the second complementary sequence pair; and The device further includes: Components for wirelessly transmitting the first complementary sequence pair in a first direction, and components for wirelessly transmitting the second complementary sequence pair in a second direction; Components for wirelessly transmitting a first sequence in a third complementary sequence pair in a third direction using the first frequency; Components for wirelessly transmitting a first sequence in a fourth complementary sequence pair in a fourth direction using the second frequency after wirelessly transmitting the first sequence in the third complementary sequence pair; Components for wirelessly transmitting a second sequence in the third complementary sequence pair in the third direction using the first frequency after wirelessly transmitting the first sequence in the fourth complementary sequence pair; and Components for wirelessly transmitting a second sequence in the fourth complementary sequence pair in the fourth direction using the second frequency after wirelessly transmitting the second sequence in the third complementary sequence pair, wherein the device further includes: Components for determining the distance of an object based on the received first complementary sequence pair, the received second complementary sequence pair, the received third complementary sequence pair, and the received fourth complementary sequence pair.

14. The device according to claim 13, further including components for causing the device to perform the transmission sequence and the reception sequence continuously multiple times.

15. The device according to claim 13, further including: Components for wirelessly transmitting a third complementary sequence pair using a third frequency and wirelessly transmitting a fourth complementary sequence pair using a fourth frequency, such that the first sequence in the third complementary sequence pair and the first sequence in the fourth complementary sequence pair are wirelessly transmitted after wirelessly transmitting the first sequence in the second complementary sequence pair and before wirelessly transmitting the second sequence in the first complementary sequence pair.

16. The device according to claim 13, wherein the components for performing the transmission sequence include a single digital-to-analog converter (DAC).

17. The device according to claim 13, wherein the components for performing the reception sequence include a single analog-to-digital converter (ADC).

18. A non - transitory computer - readable medium storing instructions for performing radio - frequency (RF) sensing using spatio - temporal frequency multiplexing (STFM), wherein the instructions, when executed by one or more processing units, cause the one or more processing units to: Execute a transmission sequence, which includes: Wirelessly transmit a first sequence in a first complementary sequence pair using a first frequency; After wirelessly transmitting the first sequence in the first complementary sequence pair, wirelessly transmit a first sequence in a second complementary sequence pair using a second frequency; After wirelessly transmitting the first sequence in the second complementary sequence pair, wirelessly transmit a second sequence in the first complementary sequence pair using the first frequency; And After wirelessly transmitting the second sequence in the first complementary sequence pair, wirelessly transmit a second sequence in the second complementary sequence pair using the second frequency; Execute a reception sequence, which includes: Receive the first complementary sequence pair, and Receive the second complementary sequence pair; and Wherein the instructions further include instructions for causing the one or more processing units to perform the following operations: Wirelessly transmit the first complementary sequence pair in a first direction and wirelessly transmit the second complementary sequence pair in a second direction; Wirelessly transmit a first sequence in a third complementary sequence pair in a third direction using the first frequency; after wirelessly transmitting the first sequence in the third complementary sequence pair, wirelessly transmit a first sequence in a fourth complementary sequence pair in a fourth direction using the second frequency; After wirelessly transmitting the first sequence in the fourth complementary sequence pair, wirelessly transmit a second sequence in the third complementary sequence pair in the third direction using the first frequency; and After wirelessly transmitting the second sequence in the third complementary sequence pair, wirelessly transmit a second sequence in the fourth complementary sequence pair in the fourth direction using the second frequency, Wherein the instructions, when executed by the one or more processing units, further cause the one or more processing units to: Determine the distance of an object based on the received first complementary sequence pair, the received second complementary sequence pair, the received third complementary sequence pair, and the received fourth complementary sequence pair.

19. The non - transitory computer - readable medium according to claim 18, wherein the instructions further include instructions for causing the one or more processing units to execute the transmission sequence and the reception sequence multiple times continuously.

20. The non - transitory computer - readable medium according to claim 18, wherein the instructions further include instructions for causing the one or more processing units to perform the following operations: Wirelessly transmit a third complementary sequence pair using a third frequency and wirelessly transmit a fourth complementary sequence pair using a fourth frequency, such that the first sequence in the third complementary sequence pair and the first sequence in the fourth complementary sequence pair are wirelessly transmitted after wirelessly transmitting the first sequence in the second complementary sequence pair and before wirelessly transmitting the second sequence in the first complementary sequence pair.

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