Method and apparatus for blind range recovery in pulse compression radar - Patents.com

Abstract

A method, system, and non-transitory computer-readable medium for processing radar signals to recover signals within a blind area are disclosed. A transmit signal is transmitted from a radar system. The radar system receives a return signal. The return signal includes a first portion of the transmit signal that leaked during transmission and a second portion that is reflected from an object within the blind area. The return signal is partially decoded by zeroing out the first portion of the transmit signal to form a modified return signal. Pulse compression is performed on the modified return signal to form a compressed return signal. The compressed return signal is processed to calculate moment products. The moment products are calibrated using a calibration factor, where the calibration factor is multiplied only to the calculated moment products of the partially decoded range gate.

Description

[Technical field]

[0001] [CROSS REFERENCE TO RELATED APPLICATIONS] This patent application claims priority to a provisional patent application identified in U.S. Patent Application No. 62 / 798,287, filed on January 29, 2019, the entire contents of which are incorporated herein by reference. [Background technology]

[0002] Generally, solid-state radar requires the use of long transmit waveforms to recover the sensitivity loss due to the low peak transmit power of solid-state transmitters. Pulse compression techniques are usually used in tandem to restore range resolution. The drawback of using long transmit pulses is that it results in so-called blind regions at close ranges, where a first portion of the data set is blind due to the strong leak-through transmit signal in the radar system. This is an inherent problem when pulse compression waveforms are implemented in radars.

[0003] Existing techniques to mitigate the blind area use either a time-delayed or frequency-shifted short pulse followed by a long pulse to fill in the missing data. One such existing technique uses multiple transmit frequency bands (N. Bharadwaj, and V. Chandrasekar, "Wideband Waveform Design Principles for Solid-State Weather Radars", J. Atmos. Oceanic Technol., 29(1), pp 14-31, 2012). The technique achieved filling of the blind range by using a set of wideband waveforms concatenated together. This technique, of course, requires more frequency spectrum and has been demonstrated using the Wideband Experimental X-band Radar (WiBEX). A second similar technique uses closely spaced frequency divisions called time-code multiplexed (TFM) waveforms, presented in (BL Cheong, K. Redmond, RDPalmer, Y. Zhang, M. Yeary and T.-Y. Yu, "PX-1000: A Solid-State Polarimetric X-Band Weather Radar and Time-Frequency Multiplexed Waveform for Blind Range Mitigation," IEEE Trans. Instrum. Meas., 62(11), pp 3064-3072, 2013). The technique uses short pulses at slightly different frequencies from the long transmit waveform, and is demonstrated through a commercial off-the-shelf digital transceiver (Pentek). In this method, the radar hardware treats everything as a single waveform. Signal processing methods demultiplex the return signal into two streams of raw data, long and short range. Figure 1 shows an example reflectivity image with blind range filling using a time-code multiplexed (TFM) waveform. Note that the abrupt transition in radar sensitivity near Moore indicates the blind range of the waveform. However, these solutions are suboptimal because they require the transmission of more than one tone, i.e., a higher frequency bandwidth utilization, which increases operating costs.

[0004] Therefore, there is a need for an approach that does not rely on the use of filling pulses. [Brief description of the drawings]

[0005] Several embodiments of the present disclosure are now shown in the accompanying drawings. It should be noted, however, that the accompanying drawings only illustrate some typical embodiments and are therefore not intended to be considered limiting of the scope of the present disclosure. Furthermore, in the accompanying drawings, similar or identical reference numbers or letters may be used to identify common or similar elements, although not all such elements may be so numbered. The figures are not necessarily to scale, and certain features and certain views of the figures may be shown in scale or schematic form for clarity and conciseness.

[0006] [Figure 1] An example of reflectance imaging (from Cheong et al., 2013) is shown that includes blind range filling using a short-pulse time-code multiplexed (TFM) waveform where an abrupt sensitivity transition can be seen near Moore, Oklahoma.

[0007] [Figure 2A] 1 shows a reflectivity image from a pulse compression radar showing areas of blind range during a transmit cycle.

[0008] [Figure 2B] 13 illustrates reflectance data within a blind range region recovered through partial decoding according to the method of the present disclosure.

[0009] [Diagram 3] FIG. 1 is a block diagram of an exemplary radar system constructed in accordance with the present disclosure.

[0010] [Figure 4] 4 is a logic flow diagram of a sequential transmit and receive mode of the radar system shown in FIG. 3.

[0011] [Diagram 5] FIG. 1 is a block diagram of an exemplary computer system configured in accordance with the present disclosure.

[0012] [Figure 6] FIG. 2 is a block diagram of an example memory of a computer system that stores transmit / receive algorithms and radar processing algorithms according to the present disclosure.

[0013] [Figure 7] 4 is a flow chart illustrating steps of an embodiment of the partial decoding method of the present disclosure.

[0014] [Figure 8] Illustrates the conceptual steps of the presently disclosed blind range restoration method (right) compared to the conventional pulse compression method (left). In processing using the conventional method, target #1 is undetected, i.e., buried under the transmission leak-through. In processing using the presently disclosed method, target #1 is now restored.

[0015] [Figure 9A] 1 shows a complex time series of a non-LFM waveform.

[0016] [Figure 9B] A complex time series of LFM waveform is shown.

[0017] [Figure 9C] 1 shows a complex time series of a windowed LFM waveform.

[0018] [Figure 9D] The complex time series of Barker-13 biphase code waveform is shown.

[0019] [Figure 9E] The complex time series of the P4 polyphase code waveform is shown.

[0020] [Figure 10A] 1 shows the results of a simulation of the presently disclosed method using a non-LFM waveform. The top panel utilizes an ideal target. The center panel shows the reflectance from the received signal using a conventional pulse compression method. The bottom panel shows the reflectance from the received signal using the presently disclosed blind range restoration method.

[0021] [Figure 10B] 1 shows the results of a simulation of the presently disclosed method using an LFM waveform. The top panel utilizes an ideal target. The center panel shows the reflectance from the received signal using a conventional pulse compression method. The bottom panel shows the reflectance from the received signal using the presently disclosed blind range restoration method.

[0022] [Figure 10C] 1 shows the results of a simulation of the presently disclosed method using a windowed LFM waveform. The top panel utilizes an ideal target. The center panel shows the reflectance from the received signal using a conventional pulse compression method. The bottom panel shows the reflectance from the received signal using the presently disclosed blind range restoration method.

[0023] [Figure 10D] Figure 1 shows the results of a simulation of the presently disclosed method using the Barker-13 biphase code. The side panels utilize an ideal target. The center panels show the reflectance from the received signal using a conventional pulse compression method. The bottom panels show the reflectance from the received signal using the presently disclosed blind range reconstruction method.

[0024] [Figure 10E]1 shows the results of a simulation of the presently disclosed method using a P4 polyphase code. The top panel utilizes an ideal target. The center panel shows the reflectance from the received signal using a conventional pulse compression method. The bottom panel shows the reflectance from the received signal using the presently disclosed blind range restoration method. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0025] The present disclosure is directed to a novel signal processing method and apparatus for restoring echoes in blind areas without using filler pulses. This is achieved through the use of signal processing and partial decoding based techniques. Solid-state transmitters usually have low transmission power, and to compensate for this, long pulses need to be transmitted and processed using pulse compression to maintain good range resolution. However, when this long pulse is transmitted, the return signal is hidden during the transmission period of the transmission pulse, which is called the blind area. A shorter filler pulse is an option to restore the blind area. However, the sensitivity in the blind area is lower. Meanwhile, this technique uses the basis of pulse compression to solve the problem.

[0026] As mentioned, due to the long transmission cycle, the radar receiver simultaneously receives echoes from the transmitted signal as well as interference from the broadcast of the transmit pulse. The interference from the broadcast of the transmit pulse is referred to in the art as "leak-through". It was generally believed that all targets within the range time of the transmission cycle are not recoverable due to the much higher power of the leakage of the transmit power. Compared to the return echo from the target, the transmission leakage, or "leak-through", is several orders of magnitude larger, making the radar blind at close range. However, in accordance with the present disclosure, it has been determined that the received samples from these targets are not completely hidden. Some of the returned signals arrive beyond the range time of the transmission cycle and are therefore unaffected, making the targets recoverable by the radar system if only the good parts are used.

[0027] Before describing various embodiments of the present disclosure in more detail with illustrative descriptions, examples, and results, it should be understood that the embodiments of the present disclosure are not limited in application to the details of the methods and apparatus as described in the following description. The embodiments of the present disclosure can be implemented in other embodiments or can be practiced or carried out in various ways. Thus, the words used in this specification are intended to be given the widest possible scope and meaning, and the embodiments are intended to be illustrative rather than comprehensive. It should also be understood that the words and terms used in this specification are for the purpose of description and should not be considered as limiting unless otherwise indicated. Furthermore, in the following detailed description, numerous specific details are described to provide a more complete understanding of the present disclosure. However, it will be apparent to one of ordinary skill in the art that certain embodiments of the present disclosure can be practiced without these specific details. In other instances, features well known to those of ordinary skill in the art have not been described in detail to avoid unnecessarily complicating the description.

[0028] Unless otherwise defined herein, scientific and technical terms used in connection with the embodiments of the present disclosure shall have the meanings commonly understood by those of ordinary skill in the art. Further, unless otherwise required by context, singular terms shall include the plural and plural terms shall include the singular.

[0029] All patents, published patent applications, and non-patent literature, including but not limited to the provisional patent application identified by U.S. Patent Application No. 62 / 798,287, referred to herein are indicative of the level of skill of those skilled in the art to which the embodiments of the present disclosure pertain. All patents, published patent applications, and non-patent literature referenced in any part of this application are expressly incorporated by reference in their entirety into this specification to the same extent as if each individual patent or publication was specifically and individually indicated to be incorporated by reference.

[0030] While the method and apparatus of the disclosed embodiments have been described in terms of specific embodiments, it will be apparent to those skilled in the art that variations may be applied therein and in the steps or sequence of steps of the method described herein without departing from the spirit and scope of the inventive concept. All such similar substitutions and modifications apparent to those skilled in the art are deemed to be within the spirit and scope of the system as defined herein.

[0031] As utilized in accordance with the method and apparatus of the presently disclosed embodiments, the following terms, unless otherwise indicated, shall be understood to have the following meanings:

[0032] The use of the word "a" or "an" when used in conjunction with the term "comprising" in the claims and / or specification may mean "one," which is further consistent with the meanings of "one or more," "at least one," and "one or more than one." While the disclosure supports a definition that refers only to alternatives and "and / or," the use of the term "or" in the claims is used to mean "and / or" unless expressly indicated to refer only to alternatives or where the alternatives are mutually exclusive. The use of the term "at least one" is understood to include not only 1, but any quantity greater than one, including but not limited to 2, 3, 4, 5, 6, 7, 8, 9, 10, 15, 20, 30, 40, 50, 100, or any integer contained therein. The term "at least one" may be expanded up to 100 or 1000 or more, depending on the term to which it is appended. Additionally, the quantity 100 / 1000 should not be considered limiting as higher limits may also provide satisfactory results. Additionally, use of the term "at least one of X, Y and Z" is understood to include any combination of X, Y and Z, not just X alone, Y alone, and Z alone.

[0033] As used in the specification and claims, the words "comprising" (and any form of comprising, such as "comprise" and "comprises"), "having" (and any form of having, such as "have" and "has"), "including" (and any form of including, such as "includes" and "include"), or "containing" (and any form of containing, such as "contains" and "contain") are inclusive or open-ended and do not exclude additional, unrecited elements or method steps.

[0034] As used herein, the term "or combinations thereof" refers to any permutation or combination of the listed items preceding the term. For example, "A, B, C, or combinations thereof" is intended to include at least one of A, B, C, AB, AC, BC, or ABC, and also includes BA, CA, CB, CBA, BCA, ACB, BAC, or CAB, if order is important in the particular context. Continuing with this example, combinations including repeats of one or more items or terms, such as BB, AAA, AAB, BBC, AAABCCCC, CBBAAA, CABABB, etc., are expressly included. One of ordinary skill in the art will appreciate that there is typically no limit to the number of items or terms in any combination, unless the context clearly dictates otherwise.

[0035] Throughout this application, the term "about" or "approximately" is used to indicate that a value includes an inherent variation of error. Furthermore, in this detailed description, each numerical value (e.g., time or frequency) should be read once as modified by the term "about" (unless already explicitly so modified) and thereafter read again as unmodified unless the context dictates otherwise. Use of the term "about" or "approximately" can mean a range that includes ±0.5%, or ±1%, ±2%, or ±3%, or ±4%, or ±5%, ±6%, or ±7%, or ±8%, or ±9%, or ±10%, or ±11%, or ±12%, or ±13%, or ±14%, or ±15%, or ±25% of the succeeding number, unless otherwise stated.

[0036] As used herein, the term "substantially" means that the subsequently described event or circumstance occurs entirely, or that the subsequently described event or circumstance occurs to a large extent or to a large extent. For example, the term "substantially" means that the subsequently described event or circumstance occurs at least 80% of the time, or at least 90% of the time, or at least 95% of the time, or at least 98% of the time.

[0037] Features of any of the embodiments described herein may be combined with any of the other embodiments to create new embodiments. As used herein, any reference to "one embodiment" or "an embodiment" means that a particular element, feature, structure, or characteristic described in connection with an embodiment is included in at least one embodiment. The appearances of the phrase "in one embodiment" in various places in this specification are not necessarily all referring to the same embodiment.

[0038] As used herein, all numerical values ​​or ranges include values ​​and integer fractions within such ranges, as well as integer fractions within such ranges, unless the context clearly indicates otherwise. Thus, for illustration purposes, a reference to a numerical range such as 1-10 includes 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, as well as 1.1, 1.2, 1.3, 1.4, 1.5, etc. Thus, a reference to a range of 1-50 includes 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, etc., up to and including 50. Similarly, fractions between any two consecutive integers are intended to be included herein, such as, but not limited to, .05, .1, .15, .2, .25, .3, .35, .4, .45, .5, .55, .6, .65, .7, .75, .8, .85, .9, and .95. For example, the range 3-4 includes, but is not limited to, 3.05, 3.1, 3.15, 3.2, 3.25, 3.3, 3.35, 3.4, 3.45, 3.5, 3.55, 3.6, 3.65, 3.7, 3.75, 3.8, 3.85, 3.9, and 3.95. Thus, whether or not a particular data point in a range is explicitly specified or specifically mentioned, any data point in the range is deemed to be specified, and the inventor should understand that he has knowledge of the entire range and points within the range. Reference to a series of ranges includes ranges combining the values ​​of the boundaries of the different ranges in the series. For example, a "range of 1 to 10" is read to indicate each possible number, particularly an integer, along a continuum between about 1 and about 10. Thus, whether or not a particular data point in a range is explicitly specified or specifically mentioned, any data point in the range is deemed to be specified, and the inventor should understand that he has knowledge of the entire range and points within the range.

[0039] Thus, to further illustrate reference to a series of ranges, for example, a range of 1-1000 includes, for example, 1-10, 10-20, 20-30, 30-40, 40-50, 50-60, 60-75, 75-100, 100-150, 150-200, 200-250, 250-300, 300-400, 400-500, 500-750, 750-1,000, and includes ranges of 1-20, 10-50, 50-100, 100-500, and 500-1,000. Thus, a range from 100 units to 2000 units refers to and includes all values ​​or ranges of units and fractions of units and integer values ​​within that range. Ranges include, but are not limited to, for example, 100 units to 1000 units, 100 units to 500 units, 200 units to 1000 units, 300 units to 1500 units, 400 units to 2000 units, 500 units to 2000 units, 500 units to 1000 units, 250 units to 1750 units, 250 units to 1200 units, 750 units to 2000 units, 150 units to 1500 units, 100 units to 1250 units, and 800 units to 1200 units. Thus, any two values ​​within the range of about 100 units to about 2000 units may be used to set the lower and upper boundaries of a range according to embodiments of the present disclosure.

[0040] The processes described in this disclosure can be performed using a computer system executing software adapted to perform the functions, and the resulting images and data are stored on one or more non-transitory computer readable media. Examples of non-transitory computer readable media include optical storage devices, magnetic storage devices, electronic storage devices, and the like. The term "computer system" as used herein means a system or systems capable of embodying and / or executing the logic of the processes described herein. Logic embodied in the form of software instructions or firmware can be executed on any suitable hardware, which may be a dedicated system or systems, or a specially programmed computer system, or a distributed processing computer system. When a computer system is used to execute the logic of the processes described herein, such computers and / or executions may be performed at the same geographic location or at multiple different geographic locations. Furthermore, the execution of the logic may be performed sequentially or at multiple separate times. Furthermore, such logic may be executed substantially simultaneously with the capture of the optical image, the thermal image, the RF information, or thereafter, or a combination thereof.

[0041] A circuit as used herein may be analog and / or digital components, or one or more appropriately programmed processors (e.g., microprocessors) and associated hardware and software, or hardwired logic. Also, a "component" may perform one or more functions. The term "component" may include hardware, such as a processor (e.g., microprocessor), an application specific integrated circuit (ASIC), a field programmable gate array (FPGA), a combination of hardware and software, and / or the like. The term "processor" as used herein means a single processor or multiple processors operating independently or together to collectively perform a task.

[0042] Returning now to the discussion of various embodiments of the present disclosure, consider a simple scenario in which a 10 km transmit waveform is used and there are two targets, one at 1 km and the other at 5 km. Typically, it is assumed that part of the range up to 10 km is completely blind, so the radar cannot detect these two targets at 1 km or 5 km. However, the first target at 1 km has a return signal that spans the range between 1 km and 11 km, so the last 1 km has been ignored as being good. Thus, the return signal from the last 1-km portion can be used to identify the 1 km target, even though the return signal has only one-tenth (1 / 10) of the return power left, since the signal from the first 10 km is unusable. By a similar analysis, the 5 km target will have one-half (50%) of its return signal arrive beyond 10 km. It can be seen that the completeness of the return from the target gradually increases as the range increases. Thus, the novel processing technique of the present disclosure produces a radar product that has no blind regions and a continuous sensitivity function. As such, this technique does not suffer from abrupt sensitivity changes compared to current state-of-the-art techniques such as TFM implementations.

[0043] The presently disclosed techniques are applicable to a variety of radar systems, including most solid-state pulse compression radars, and including, but not limited to, solid-state variations of single-polarization radars, wind profilers, and phase-stage radars. Improvements provided by the presently disclosed methods and systems over previously used methods and systems include, but are not limited to, the need for a lower frequency spectrum and the absence of abrupt sensitivity transitions.

[0044] Figure 2A shows an example of a conventional reflectivity image from a pulse compression radar that includes a blind range during a transmit cycle, but Figure 2B shows reflectivity data within the blind range that is recovered through partial decoding according to the method of the present disclosure.

[0045] Referring now to FIG. 3, shown therein and designated by reference numeral 10 is a radar system constructed in accordance with the present disclosure. In particular, the radar system 10 utilizes a pulsed architecture, operates at X-band frequencies, and may be designed and constructed for advanced solid-state weather radar. However, it should be understood that the radar system 10 may be operated at different frequencies and used for purposes other than weather radar. The radar system 10 may direct a transmit waveform to a radar antenna 12, where echoes from the transmit waveform may be received by the radar antenna 12 and converted into a return signal. The front-end architecture may allow the amplified transmit waveform at every pulse to be monitored in real time, demodulated from the carrier frequency and fed back to a computer system 16, and used as feedback to interpret the return signal, which is also demodulated from the carrier frequency, as described further herein.

[0046] In one embodiment, radar system 10 is provided with one or more computer systems 16, one or more intermediate frequency transceivers 18 (hereinafter referred to as “IF transceivers 18”), one or more microwave transceivers 20 (hereinafter referred to as “microwave transceivers 20”), one or more radar amplifiers 22 (hereinafter referred to as “radar amplifiers 22”), one or more front-end circuits 24 (hereinafter referred to as “front-end circuits 24”), one or more power sources 26 (hereinafter referred to as “power sources 26”), and one or more clocks 28 (hereinafter referred to as “clocks 28”). In accordance with the present disclosure, radar amplifiers 22 may have a relatively low power capacity compared to other radar amplifiers.

[0047] The computer system 16 is coupled to the IF transceiver 18 via a communication link 30, which may be in the form of a cable, for example, to allow bidirectional communication between the computer system 16 and the IF transceiver 18. The IF transceiver 18 is coupled to the microwave transceiver 20 by communication links 32 and 34 to allow bidirectional communication therebetween. In particular, the IF transceiver 18 directs a transmit signal to the microwave transceiver 20 via communication link 32, and the microwave transceiver 20 directs a demodulated return signal to the IF transceiver 18 via communication link 34. Although the communication links 32 and 34 are shown separately, it should be understood that the communication links 32 and 34 may be on a single physical communication link bundle. For example, the communication links 32 and 34 may be one or more cables. The microwave transceiver 20 is coupled to the radar amplifier 22 via communication link 36, which may be a cable and may be coupled to the front-end circuitry 24 via communication link 38. The radar amplifier 22 is provided with a low power side 40 configured to receive the transmit signal from the communication link 36 and a high power side 42 configured to provide an amplified transmit waveform on the communication link 38. The front end circuitry 24 receives the amplified transmit waveform and then directs the amplified transmit waveform to the radar antenna 12 via the communication link 44. The front end circuitry 24 also directs the transmit signal via link 38 to the microwave transceiver 20 and subsequently to the IF transceiver 18 via link 34 to sample the transmit waveform. The front end circuitry 24 otherwise directs the receive signal (low at 94, 96, and 98 in FIG. 3) from the antenna 12 to the microwave transceiver 20. The communication links 38 and 44 may be cables or any other suitable electrical conductors.

[0048] The clock 28 is coupled to the IF transceiver 18 and the microwave transceiver 20 via communication links 46 and 48 and serves to provide a reference signal for synchronizing the IF transceiver 18 and the microwave transceiver 20. The communication links 46 and 48 may be cables or any other suitable electrical conductors. The power supply 26 may provide power to various components in the radar system 10 as well as various control signals. For example, as shown in FIG. 1, the power supply 26 provides power to the microwave transceiver 20, the radar amplifier 22, and the front-end circuitry 24 via power lines 58, 60, and 62. Additionally, the power supply 26 is configured to receive transmit / receive logic signals from the IF transceiver 18 via communication link 64 and direct the transmit / receive logic signals to the front-end circuitry 24 via communication link 66.

[0049] Referring now to FIG. 4, shown therein is an exemplary logic flow diagram illustrating the function of the radar system 10 during a single pulse cycle. Generally, prior to a pulsing cycle, the transmit waveform is loaded into a wave table of the IF transceiver 20. At each pulse cycle, the transmit waveform is converted to analog form, as indicated by block 72. In this example, the transmit pulse is in digital form, where the transmit waveform is implemented as a series of numbers that can be interpreted by a predefined time sequence algorithm. The IF transceiver 18 receives the transmit pulse having the transmit waveform from the computer system 16, and then processes the transmit pulse using a predefined time sequence algorithm to convert the series of numbers into an analog waveform, as indicated by block 72. The IF transceiver 18 directs the analog waveform to the microwave transceiver 20 via the communication link 32, and also directs the transmit / receive signal to the power source 26. The direction of the analog waveform and the transmit / receive signal are synchronized, so that the amplified transmit waveform is sampled and fed back to the computer system 16, followed by the return signal as described above.

[0050] As indicated by block 74, the microwave transceiver 20 receives the transmit signal in the form of an analog waveform and then modulates the analog waveform onto a carrier frequency to generate a transmit signal. As indicated by block 75, the microwave transceiver 20 directs the transmit signal via communication link 36 to the radar amplifier 22, which then amplifies the transmit signal to form the amplified transmit waveform described above. The radar amplifier 22 may have any suitable gain and may, for example, operate in a nonlinear range. Thereafter, as indicated by block 76, the front-end circuitry 24 receives the amplified transmit waveform and the transmit / receive logic signal and then samples the amplified transmit waveform while also directing the amplified transmit waveform to the radar antenna 12 via communication link 44. As represented by block 77, the samples of the amplified transmit waveform and the return signal are then directed to computer system 16 by way of communications links 38, 34 and 30, microwave transceiver 20 and IF transceiver 18 where the samples of the amplified transmit waveform and the return signal are demodulated and converted from analog to digital form. In other words, in response to receiving the samples of the amplified transmit waveform and the return signal, microwave transceiver 20 demodulates the samples to remove the carrier frequency and form an analog waveform which is then converted to a digital waveform (i.e., a series of numbers) by IF transceiver 18.

[0051] Thereafter, as represented by block 78, computer system 16 match filters the demodulated return signal with the demodulated samples of the amplified transmit waveform, and then processes the radar signal having the information generated by match filtering the demodulated return signal with the demodulated samples of the amplified transmit waveform using radar processing algorithms, as further described herein, to convert the information into data, such as weather data indicative of one or more features within the Earth's atmosphere.

[0052] 5, computer system 16 includes a processor 100 configured to execute processor-executable code, one or more memories 102 capable of storing the processor-executable code, input devices 104, one or more communication interfaces 106, and output devices 108. Computer system 16 may be partially or fully network-based or cloud-based, and need not necessarily be located at a single physical location.

[0053] The processor 100 may be implemented as a single processor or multiple processors working together to execute the logic described herein. Exemplary embodiments of the processor 100 include a digital signal processor (DSP), a central processing unit (CPU), a field programmable gate array (FPGA), a microprocessor, a multi-core processor, and combinations thereof. The processor 100 may communicate with one or more memories 102 via a path 110, which may be implemented, for example, as a data bus. The processor 100 may communicate with an input device 104 and an output device 108 via paths 112 and 114, respectively. The paths 112 and 114 may be implemented similarly or differently than the path 110. The processor 100 may further interface and / or communicate with one or more user terminals (not shown) via a network 420 via one or more communication interfaces 106, paths 122 and 124, such as by exchanging electronic, digital and / or optical signals via one or more physical or virtual ports using a network protocol such as TCP / IP. It should be understood that in particular embodiments, if processor 100 includes more than one processor, such processors may be remotely located from one another, co-located, or comprise a single multi-core processor (not shown). Processor 100 is capable of reading and / or executing processor-executable code and / or creating, manipulating, modifying, and storing computer data structures in one or more memories 102.

[0054] The one or more memories 102 store the processor executable code and may be implemented as non-transitory memory such as, for example, random access memory (RAM), CD-ROM, hard drive, solid state drive, flash drive, memory card, DVD-ROM, floppy disk, optical drive, and combinations thereof. Although the one or more memories 102 are shown to be located in the same physical location as the computer system 16, it should be understood that the one or more memories 102 may be located remotely from the computer system 16 and communicate with the processor 100 via the network 120. Additionally, if more than one memory 102 is used, the one or more memories 102 may be located in the same physical location as the computer system 16, and the one or more memories 102 may be located in a physical location remote from the computer system 16. The physical location of the one or more memories 102 may vary, and the one or more memories 102 may be implemented as "cloud memory," i.e., one or more memories 102 that are partially or completely based on or accessed using the network 120.

[0055] The input devices 104 send data to the processor 100 and can be implemented as, for example, a keyboard, a mouse, a touch screen, a camera, a cell phone, a tablet, a smart phone, a PDA, a microphone, a network adapter, and combinations thereof. The input devices 104 may be located in the same physical location as the computer system 16, or may be located remotely and / or partially or fully network-based. The input devices 104 communicate with the processor 100 via a path 112, which may be a data bus as described above.

[0056] Output device 108 transmits information from processor 100 to a user so that the information may be perceived by the user. For example, output device 108 may be implemented as a server, a computer monitor, a cell phone, a tablet, a speaker, a website, a PDA, a fax, a printer, a projector, a laptop monitor, and combinations thereof. Output device 108 may be physically co-located with computer system 16 or may be remotely located from computer system 16 and may be partially or fully network-based (e.g., a website hosted by one or more servers and accessible over the Internet using, for example, HTML, XHTML, Secure HTML, and / or TCP / IP). Output device 108 communicates with processor 100 via path 114.

[0057] Network 120 preferably allows for bidirectional communication of information and / or data between computer system 16 and one or more user terminals and / or other devices (not shown). Network 120 may interface with computer system 16 in a variety of ways, such as by optical and / or electronic interfaces, and may use a number of network topographies and protocols, such as, for example, Ethernet, TCP / IP, circuit-switched paths, and combinations thereof. For example, network 120 may be implemented as the World Wide Web (or Internet), a local area network (LAN), a wide area network (WAN), a metropolitan network, a wireless network, a cellular network, a GSM-network, a CDMA network, a 3G network, a 4G network, a satellite network, a radio network, an optical network, a cable network, a public switched telephone network, an Ethernet network, and combinations thereof, and may use a variety of network protocols to allow for bidirectional interfacing and communication of data and / or information between processor 100 and network 120.

[0058] 6, one or more memories 102, which may be referred to herein as a “non-transitory computer readable medium,” preferably store processor executable code and / or information comprising radar transmit / receive algorithm 130 and radar processing algorithm 132. The processor executable code may be written in any suitable programming language, such as, for example, C++. Radar transmit / receive algorithm 130 and radar processing algorithm 132 may be stored as data structures. In alternative embodiments, the logic described above with respect to processor 100, radar transmit / receive algorithm 130, and radar processing algorithm 113 may be performed by hardware, such as an application specific integrated circuit or a field programmable gate array.

[0059] FIG. 7 is a flow chart showing the general sequence of steps in the implementation of a radar processing algorithm 132 for the reconstruction of the blind range of a target, as will be described more fully below.

[0060] When the system 10 emits a transmit signal from the antenna 12, waves from the transmit signal reflect off objects and are returned to and received by the antenna 12. These reflected signals are referred to herein as returned signals or returned waves. The system 10 may be provided with range gates (not shown) that open and close sequentially to allow the returned signal to pass through each successive range gate within a given period of time. The signal passing through each gate is referred to as a sample and represents a given range increment from the antenna 12. The transmit signal is emitted for a predetermined amount of time, often referred to as the pulse width. Depending on the frequency of the transmitted signal, the transmitted wave at the beginning of the transmit signal will reach a certain distance from the antenna 12 before the transmission of the transmit signal ends. For example, in Figures 2A and 2B, circles 4 and 6 respectively represent the distance that a first wave transmitted from a transmitter, such as the antenna 12 of the radar system 10 located at the center of the circles 4 and 6, will reach before the end of the transmit signal. The area inside the circles 4 and 6 represents the so-called blind area referred to above. When described in terms of distance, the blind region may also be referred to as the blind range. In other words, for the example waveforms depicted in Figures 2A and 2B, the blind region is a circle having a radius of 10 kilometers from the transmitter, or a blind range of 10 kilometers.

[0061] When waves from a transmitted signal reflect off an object in the blind region, or before the transmission of the transmitted signal is completed, the reflected and transmitted waves interfere with each other, creating what is referred to in the art as "leakage" or "leak-through," which combines with the reflected signal to produce a composite signal that effectively cancels the reflected signal. In an exemplary embodiment of the system 10, the returned signals are in-phase / quadrature (I / Q) and some of the returned signals are samples affected by leakage from the transmitted signal. As described herein, the system 10 removes the portion of the samples affected by the leakage and compensates for the effects of the leakage in the radar processing algorithm 132 to generate a new compressed signal and moment product. To accomplish this, the radar processing algorithm 132 performs a partial decoding process as described herein. A first stage 202 of the partial decoding process removes the reflected signal, e.g., I / Q samples, affected by the transmit waveform leakage. This may be achieved by discarding all return signals received during the transmission cycle, which effectively nulls out any signals returned from the object or interference caused by the transmitted signal. To suppress leakage from the transmitted pulse, the encoded input x(n) is modified by multiplying it by a window (w(n)). See FIG. 8 for a representation of the window. The encoded input x(n) may be a digital version of the return signal being processed by the computer system 16. The window w(n) is a function that serves to null out the return signals received during the transmission of the transmitted signal. The new encoded input may then be expressed as:

number

number

[0062] In the second stage 204 of partial decoding, a new encoded input (e.g., uncompressed I / Q samples) is pulse compressed. This new encoded input, when passed through the decoder, will produce a different decoded output, but will not require the same template for decoding.

number

number

[0063] The new pulse compressed I / Q data is then processed for moment products in a manner well known in the art in step 206. For example, in one non-limiting embodiment, moment products are calculated as they normally are in weather radars. This calculation is no different from that used in conventional implementations.

[0064] In step 207, the radar processing algorithm 132 determines whether there is data, i.e., a signal returned from an object within the blind range in the processed output. If there is no data in the processed output, the radar processing algorithm 132 ends and the processed output is used to perform the radar product calculations.

[0065] However, if the radar processing algorithm 132 determines in step 207 that data exists in the blind range, for example if it finds an incomplete return as shown in FIG. 8, the processing algorithm 132 causes the computer 16 of the system 10 to perform partial decoding and calibration. Due to the window (zeroed portion) at the beginning of the uncompressed I / Q received signal, the signal returned from a target or object in the blind range is only partially decoded and has a relatively small signal strength (i.e., on the order of 1 / 2 to 1 / 10 of the normal signal strength of the return signal). It may be necessary to compensate for this effect in order to properly detect the return signal from a target or object in the blind range. In step 208, the radar processing algorithm 132 applies a calibration or scaling factor as a multiplied weight to the calculated moment products from the radar in the processed output. The weight of the scaling factor depends on two factors: how close the affected range gate is to the transmitter and which waveform was transmitted. An approximation of the scaling factor is presented in the following equation:

number

[0066] In some embodiments, the calibration coefficients s(n) may be applied prior to computation of the moment products to form a data set, which are then computed using the data set. For example, the calibration coefficients s(n) may be applied to the new encoded input

number

[0067] Once the processed output is multiplied once by the scaling factor, the new decoded output may be written as:

number

[0068] 8 illustrates a comparison between a conventional pulse compression method ("Conventional Method") and the novel blind range restoration method disclosed herein ("New Method"). This non-limiting example is based on two targets, one (Target #2) that is normally located within the usable range, and the other (Target #1) that is the subject of the blind range restoration of the present disclosure, that is located within the blind region. [example]

[0069] Several non-limiting experiments were performed to demonstrate the effectiveness of the new technique using various waveforms. During the experiments, the returned signal was processed using two techniques: traditional pulse compression and a new blind range restoration method, and the performance of both was evaluated.

[0070] To perform the experiment, four targets were used, two of which were located within the blind range and two were located outside the blind range. The transmitted waveforms included were: a nonlinear frequency modulation (Non-LFM) waveform shown in FIG. 9A, a linear frequency modulation (LFM) waveform shown in FIG. 9B, a windowed LFM waveform shown in FIG. 9C, a Barker-13 biphasic code waveform shown in FIG. 9D, and a P4 polyphase code waveform shown in FIG. 9E (see, for example, BL Lewis and FF Kretschmer JR., "Linear Frequency Modulation Derived Polyphase Pulse Compression Codes," IEEE Trans. Aerosp. Electron. Syst., Vol. AES-18. NO. 5, pp 637-641, 1982). Simulations were performed using each waveform. The results in terms of reflectivity from both techniques, as well as the response of an ideal target, are presented in FIG. 10A to FIG. 10E (corresponding to the waveforms shown in FIG. 9A to FIG. 9E, respectively). Although phase-encoded waveforms were implemented in the simulations, they are not typically used in radar applications and radar systems.

[0071] As shown by these results, targets within the blind area are now visible using the methods and systems disclosed herein and are not hidden as in results obtained using conventional methods. It is noteworthy that not only are targets within the blind area recovered, but the reflectance values ​​from the targets are correct even when recovered from only a portion of the returned waveform. This was achieved due to the inclusion of calibration coefficients. Furthermore, the targets are recovered independently of the transmitted waveform, at the correct range spot.

[0072] At least one embodiment of the present disclosure is directed to a method of processing a radar signal to recover a signal reflected by an object in a blind region, the method comprising: transmitting a transmission signal from a radar system; receiving a return signal at the radar system, the return signal including a portion of the transmission signal that leaked during transmission and a portion that was reflected from an object in the blind region; partially decoding the return signal by zeroing out the received return signal during transmission of the transmission signal to form a modified return signal; performing pulse compression of the modified return signal to form a compressed return signal; processing the compressed return signal and calculating moment products therefrom; and forming a data set comprising data representative of an object in the blind region by calibrating moment products of range gates that received the return signal during the duration of the transmission signal with a calibration factor, where the calibration factor is proportional to a power loss due to an effect of partial decoding of the return signal received at a particular range gate, the calibration factor being based on a waveform of the transmission signal and a proximity of the radar to a range covered by the particular range gate. The method may comprise the further step of generating an image based on the dataset, where the image includes the target in the blind range. The dataset may comprise weather data, where the image is a weather image.

[0073] Below is a numbered list of non-limiting exemplary embodiments of the inventive concepts disclosed herein. [Item 1] 1. A method for processing a radar signal to recover a signal in a blind region, the method comprising: transmitting a transmission signal from a radar system; receiving a return signal at the radar system, the return signal including a first portion of the transmitted signal that leaked during transmission and a second portion that is reflected off an object in the blind region; partially decoding the return signal by zeroing out a first portion of the transmit signal that leaked during transmission of the transmit signal, forming a modified return signal, and performing pulse compression on the modified return signal to form a compressed return signal; processing the compressed return signal to calculate moment products therefrom; forming a data set comprising data recovered from the blind region by calibrating the moment products of range gates within the blind range with a calibration factor, the calibration factor being multiplied only to calculated moment products of partially decoded range gates, the calibration factor being proportional to the power loss due to the effect of the partial decoding in a particular range gate, the calibration factor being based on the waveform of the transmitted signal and the proximity of the radar to the range covered by the particular range gate; A method comprising: [Item 2] 2. The method of claim 1, further comprising the step of generating an image based on the data set, the image including a target in the blind range. [Item 3] 3. The method of claim 2, wherein the dataset comprises meteorological data and the images are meteorological images. [Item 4] 4. The method according to any one of claims 1 to 3, wherein the return signal is an I / Q signal. [Item 5] A non-transitory computer-readable medium storing computer-executable logic that, when executed by one or more processors, receiving a return signal from the radar system, the return signal including a first portion of the transmitted signal that leaked during transmission and a second portion that is reflected from an object in the blind region; partially decoding the return signal by zeroing out a first portion of the transmit signal that leaked during transmission of the transmit signal, forming a modified return signal, and performing pulse compression on the modified return signal to form a compressed return signal; processing the compressed return signal to calculate moment products therefrom; forming a data set comprising data recovered from the blind region by calibrating the moment products of range gates within the blind range with a calibration factor, the calibration factor being multiplied only to calculated moment products of partially decoded range gates, the calibration factor being proportional to the power loss due to the effect of the partial decoding in a particular range gate, the calibration factor being based on the waveform of the transmitted signal and the proximity of the radar to the range covered by the particular range gate; By A non-transitory computer-readable medium that causes the one or more processors to process radar signals to recover signals within the blind regions. [Item 6] 6. The non-transitory computer-readable medium of claim 5, wherein the computer-executable logic, when executed by the one or more processors, causes the one or more processors to generate an image based on the dataset, the image including a target in the blind range. [Item 7] 7. The non-transitory computer-readable medium of claim 6, wherein the dataset comprises meteorological data and the images are meteorological images. [Item 8] 8. The non-transitory computer-readable medium of any one of items 5 to 7, wherein the return signal is an I / Q signal. [Item 9] A computer system comprising one or more processors, the one or more processors comprising: receiving a return signal from a radar system, the return signal including a first portion of a transmitted signal that leaked during transmission and a second portion that is reflected off an object in the blind region; partially decoding the return signal by zeroing out a first portion of the transmit signal that leaked during transmission of the transmit signal, forming a modified return signal, and performing pulse compression on the modified return signal to form a compressed return signal; processing the compressed return signal to calculate moment products therefrom; forming a data set comprising data recovered from the blind region by calibrating the moment products of range gates within the blind range with a calibration factor, the calibration factor being multiplied only to calculated moment products of partially decoded range gates, the calibration factor being proportional to the power loss due to the effect of the partial decoding in a particular range gate, the calibration factor being based on the waveform of the transmitted signal and the proximity of the radar to the range covered by the particular range gate; A computer system that performs the above steps. [Item 10] 10. The computer system of claim 9, wherein the one or more processors generate an image based on the dataset, the image including a target in the blind range. [Item 11] Item 11. The computer system of item 10, wherein the dataset comprises meteorological data and the images are meteorological images. [Item 12] 12. The computer system of any one of claims 9 to 11, wherein the return signal is an I / Q signal. [Item 13] A computer system comprising one or more processors, the one or more processors comprising: receiving a return signal from the radar system, the return signal including a first portion of the transmitted signal that leaked during transmission and a second portion that is reflected from an object in the blind region; partially decoding the return signal by zeroing out a first portion of the transmit signal that leaked during transmission of the transmit signal to form a modified return signal, calibrating the modified return signal with one or more calibration factors to form a calibrated modified return signal, and performing pulse compression on the calibrated modified return signal to form a compressed return signal; processing said compressed return signal to calculate moment products therefrom; Do the following: Calibrating the modified return signal with the one or more calibration factors forms a data set. [Item 14] 14. The computer system of claim 13, wherein the calibration factor is multiplied only to the modified return signal of a partially decoded range gate, the calibration factor being proportional to the power loss due to the effect of the partial decoding in a particular range gate, and the calibration factor being based on the waveform of the transmitted signal and the proximity of the radar to the range covered by the particular range gate. [Item 15] Item 14. The computer system of item 13, wherein the one or more processors generate an image based on the dataset, the image including a target in the blind range. [Item 16] Item 16. The computer system of item 15, wherein the dataset comprises meteorological data and the images are meteorological images. [Item 17] 17. The computer system of any one of claims 13, 14, 15 or 16, wherein the return signal is an I / Q signal. [Item 18] receiving a return signal from the radar system, the return signal including a first portion of the transmitted signal that leaked during transmission and a second portion that is reflected from an object in the blind region; partially decoding the return signal by zeroing out a first portion of the transmit signal that leaked during transmission of the transmit signal, forming a modified return signal, and performing pulse compression on the modified return signal to form a compressed return signal; processing said compressed return signal to calculate moment products therefrom; Equipped with A calibration factor is applied to at least one of the modified return signal, the compressed return signal, and the moment product to form a data set comprising recovered data from the blind region. method. [Item 19] 20. A non-transitory computer-readable medium storing computer-executable code that, when executed by a processor, causes the processor to perform the method of claim 18. [Item 20] 20. A computer system comprising one or more processors for executing the method according to item 18. Although several embodiments have been provided in this disclosure, it will be understood that the disclosed systems and methods may be embodied in many other specific forms without departing from the spirit or scope of the disclosure. The examples should be considered as illustrative rather than restrictive, and are not intended to be limited to the details provided herein. For example, various elements or components may be combined or integrated in another system. Or, certain features may be omitted or not implemented. Additionally, in various embodiments, techniques, systems, subsystems, and methods described and shown as separate or distinct may be combined or integrated with other systems, components, techniques, or methods without departing from the scope of the present disclosure. Other items shown or described as being coupled may be directly coupled, or indirectly coupled, or communicate electrically, mechanically, or otherwise through some interface, device, or intermediate component. Other examples of changes, substitutions, and alterations will be ascertainable by one of ordinary skill in the art and may be made without departing from the spirit and scope of the inventive concepts disclosed herein.

Claims

1. 1. A method for processing a radar signal to recover a signal in a blind region, the method comprising: transmitting a transmission signal from a radar system; receiving a return signal at the radar system, the return signal including a first portion of the transmitted signal that leaked during transmission and a second portion that is reflected off an object in the blind region; partially decoding the return signal by zeroing out a first portion of the transmit signal that leaked during transmission of the transmit signal to form a modified return signal and performing pulse compression on the modified return signal to form a compressed return signal; processing the compressed return signal to calculate moment products therefrom; forming a data set comprising data recovered from the blind region by calibrating the moment products of range gates within the blind region with a calibration factor, the calibration factor being multiplied only to the moment products of partially decoded range gates, the calibration factor being proportional to the power loss due to the partial decoding effect in a particular range gate, the calibration factor being based on the waveform of the transmitted signal and the proximity of the radar system to the range covered by the particular range gate; A method comprising:

2. The method of claim 1 , comprising the further step of generating an image based on the data set, the image including a target in the blind region.

3. The method of claim 2 , wherein the data set comprises meteorological data and the images are meteorological images.

4. The method according to claim 1 , wherein the return signal is an I / Q signal.

5. 1. A program for processing a radar signal to recover a signal in a blind area, the program comprising: receiving a return signal from a radar system, the return signal including a first portion of a transmitted signal that leaked during transmission and a second portion that is reflected off an object in the blind region; partially decoding the return signal by zeroing out a first portion of the transmit signal that leaked during transmission of the transmit signal to form a modified return signal, and performing pulse compression on the modified return signal to form a compressed return signal; processing the compressed return signal to calculate moment products therefrom; forming a data set comprising data recovered from the blind region by calibrating the moment products of range gates within the blind region with a calibration factor, the calibration factor being multiplied only to the moment products of partially decoded range gates, the calibration factor being proportional to the power loss due to the effect of the partial decoding in a particular range gate, the calibration factor being based on the waveform of the transmitted signal and the proximity of the radar system to the range covered by the particular range gate; A program that executes the following.

6. The program of claim 5 , further comprising causing the processor to perform the steps of: generating an image based on the dataset, the image including a target in the blind region.

7. The program of claim 6 , wherein the data set comprises meteorological data and the images are meteorological images.

8. The program according to claim 5 , wherein the return signal is an I / Q signal.

9. 1. A computer system comprising one or more processors, the one or more processors comprising: receiving a return signal from a radar system, the return signal including a first portion of a transmitted signal that leaked during transmission and a second portion that is reflected from an object in a blind region; partially decoding the return signal by zeroing out a first portion of the transmit signal that leaked during transmission of the transmit signal to form a modified return signal and performing pulse compression on the modified return signal to form a compressed return signal; processing the compressed return signal to calculate moment products therefrom; forming a data set comprising data recovered from the blind region by calibrating the moment products of range gates within the blind region with a calibration factor, the calibration factor being multiplied only to the moment products of partially decoded range gates, the calibration factor being proportional to the power loss due to the partial decoding effect in a particular range gate, the calibration factor being based on the waveform of the transmitted signal and the proximity of the radar system to the range covered by the particular range gate; A computer system that performs the above steps.

10. The computer system of claim 9 , wherein the one or more processors generate an image based on the dataset, the image including a target in the blind region.

11. The computer system of claim 10 , wherein the data set comprises meteorological data and the images are meteorological images.

12. 12. The computer system of claim 9, wherein the return signal is an I / Q signal.

13. 1. A computer system comprising one or more processors, the one or more processors comprising: receiving a return signal from a radar system, the return signal including a first portion of a transmitted signal that leaked during transmission and a second portion that is reflected from an object in a blind region; partially decoding the return signal by zeroing out a first portion of the transmit signal that leaked during transmission of the transmit signal to form a modified return signal, calibrating the modified return signal with one or more calibration factors to form a calibrated modified return signal, and performing pulse compression on the calibrated modified return signal to form a compressed return signal; processing the compressed return signal to calculate moment products therefrom; Do the following: a step of calibrating the modified return signal with the one or more calibration coefficients forming a data set, the return signal being an I / Q signal, the one or more calibration coefficients being multiplied only to the modified return signal of partially decoded range gates, the one or more calibration coefficients being proportional to power loss due to the effect of the partial decoding in a particular range gate.

14. 14. The computer system of claim 13, wherein the one or more calibration coefficients are based on a waveform of the transmitted signal and the proximity of the radar system to a range covered by the particular range gate.

15. 14. The computer system of claim 13, wherein the one or more processors generate an image based on the dataset, the image including a target in the blind region, the dataset comprising weather data, and the image is a weather image.

Images