A dual-mode nonlinear radar arranged for harmonic and intermodulation operation, as well as a corresponding method

Abstract

A dual-mode radar arranged for harmonic and intermodulation operation, said dual-mode radar comprising a transmitter system arranged for detecting an object, said transmitter system comprising a main transmitter arranged for transmitting a first signal towards said object, said first signal having a first frequency, at least one auxiliary transmitter arranged for transmitting a second signal, simultaneously with said first signal, towards said object, said second signal having a second frequency, said second frequency being different, but in a same order of magnitude, to said first frequency, and a receiver system, comprising a receiver arranged for simultaneously receiving a harmonic return signal corresponding to said first signal and receiving an intermodulated return signal corresponding to said first and second signal.

Description

[0001] Title

[0002] A dual-mode nonlinear radar arranged for harmonic and intermodulation operation, as well as a corresponding method.

[0003] Technical field

[0004] The present disclosure generally relates to the field of radars and, more specifically, to a nonlinear radar capable of both harmonic and intermodulation operation.

[0005] Background

[0006] Radar, short for “Radio Detection and Ranging,” is a versatile technology that has transformed the way we perceive and interact with our surroundings. It may play an important role in applications ranging from military defence, weather monitoring, air traffic control and detecting and tracking of objects in versatile environments. At its core, a radar is a system that uses radio waves to, for example, detect, locate, and track objects in the surrounding environment.

[0007] The principle of radar operation is founded on the transmission of radio waves towards an object and the measurement of the reflected signals. This information is then used to, for example, calculate the range, velocity, and sometimes even the size and shape of the object.

[0008] Nonlinear radar is widely used for detection and tracking of objects in cluttered environment. In contrast to conventional radar systems that are designed for tracking of targets producing linear, i.e. around the same central frequency, response when illuminated with an Radio Frequency, RF, signal, in nonlinear radar the target is nonlinear and it generates a return signal at a frequency different from that of the illuminating signal.

[0009] Harmonic return signals are a direct consequence of this nonlinearity. When the target interacts with the illuminating signal, it can produce additional signals at frequencies that are integer multiples of the illuminating frequency. These harmonic frequencies may manifest as discrete spikes or peaks in the radar’s received signal spectrum.

[0010] Intermodulation return signals arise when the nonlinear properties of the target or any nonlinear elements cause the mixing of different frequencies present in the radar system. As a result, the target can emit frequencies that are the sum or difference of the various radar frequencies involved.

[0011] Intermodulation products can introduce new frequencies into the return signal, which can complicate the radar’s data analysis. However, they can also be harnessed for specific applications, such as target discrimination or signature analysis.

[0012] Nonlinear radar, with its harmonic and intermodulation return signals, has found applications in a range of fields. It is particularly valuable in scenarios where traditional radar may struggle to provide accurate target information, such as in the presence of clutter or in complex electromagnetic environments. Nonlinear radar techniques can offer enhanced capabilities for target detection, identification, and characterization.

[0013] Summary

[0014] It would be advantageous to achieve a dual-mode nonlinear radar that is capable of both harmonic and intermodulation operation. It would further be advantageous to achieve a corresponding method.

[0015] In a first aspect of the present disclosure, there is provided a dual-mode radar arranged for harmonic and intermodulation operation, said dual-mode radar comprising: a transmitter system arranged for detecting an object, said transmitter system comprising: a main transmitter arranged for transmitting a first signal towards said object, said first signal having a first frequency; at least one auxiliary transmitter arranged for transmitting a second signal, simultaneously with said first signal, towards said object, said second signal having a second frequency, said second frequency being different, but in a same order of magnitude, to said first frequency; a receiver system, comprising a receiver arranged for simultaneously receiving a harmonic return signal corresponding to said first signal and receiving an intermodulated return signal corresponding to said first and second signal.

[0016] Intermodulation radar and harmonic radar are two nonlinear radar techniques, each with its unique advantages and applications. Intermodulation radar may have better properties with respect to target discrimination, as it may offer more precise differentiation of objects or materials due to the complex response patterns generated by intermodulation products. It may reduce frequency dependency and may provide clutter suppression capabilities by analyzing these products, making it suitable for complex electromagnetic environments.

[0017] Harmonic radar is typically, from a conceptual point of view, simpler, relying solely on the generation of harmonics, and may offer an identification process. It may feature lower system complexity, making it cost-effective and easier to implement, with greater signal isolation. Harmonic radar may be preferred in scenarios where simplicity, affordability, and ease of operation are of importance, and where distinct harmonic frequencies can be effectively utilized for target detection and identification.

[0018] The inventors have found that it may be beneficial to provide for a dualmode radar that is capable of both harmonic and intermodulation operation. The advantages of harmonic radar may then be combined with the advantages of intermodulation radar.

[0019] In order to accomplish the above, the inventors have found that it may be beneficial if the transmitter system comprises two transmitters. A main transmitter that is arranged for transmitting a first signal towards the object, wherein the first signal has a first frequency. At least one auxiliary transmitter arranged for transmitting a second signal, simultaneously with the first signal, towards the object, wherein the second signal has a second frequency, but wherein the second frequency differs from the first frequency.

[0020] The above allows the object to provide multiple return signals. A first return signal is a harmonic return signal that corresponds to the first signal. For example the frequency of the harmonic return signal equals an integer times the first frequency of the first signal. More specifically, the harmonic return signal may have a frequency of two times the first frequency, or three time the first frequency, etc. Further, the above allows the object to provide an intermodulated return signal. The intermodulated return signal is a signal that is a combination of the first signal and the second signal. The frequency of the intermodulated return signal may equal an integer times the first frequency of the first signal plus / minus an integer times the second frequency of the second signal.

[0021] Following the above, the first signal is thus used for both the generation of the harmonic return signal but also as a component in the generation of the intermodulated return signal.

[0022] The receiver of the dual-mode radar is arranged for simultaneously receiving the harmonic return signal corresponding to the first signal and for receiving the intermodulated return signal corresponding to the first and second signal.

[0023] The inventors have realized that this may be accomplished by ensuring that the first frequency and the second frequency are in a same order of magnitude. This enables that the frequency of the harmonic return signal and the frequency of the intermodulated return signal to be approximately in the same frequency range, such that the receiver is able to be tuned to that frequency range.

[0024] Same order of magnitude may mean that the frequency of the harmonic return signal and the frequency of the intermodulated return signal will not differ more than a factor 10 from one another.

[0025] The present disclosure is directed to nonlinear radar systems, which may be utilized for object detection and tracking, especially in complex and cluttered environments. Unlike conventional radar systems that track linear responses at the same central frequency when illuminated with RF, signals, nonlinear radar may operate with nonlinear targets that generate return signals at frequencies different from the illuminating signal.

[0026] This frequency difference between the transmit and receive signals allows for effective clutter suppression, as linear clutter mostly remains at the transmit frequency. Nonlinear behaviour in radar systems can be induced intentionally, for example, by placing nonlinear tags on the target or may result from processes like corrosion in metals or parasitic nonlinearities in electronic devices.

[0027] Nonlinear radar can take on different forms, with harmonic radar , HR, and intermodulation radar, IR, being the two most common varieties. In HR, the radar unit transmits a signal at a fundamental frequency, i.e. f 1 , and receives the harmonic return signal at a harmonic frequency, n*f1 , where n is an integer.

[0028] HR systems typically receive the return signal at 2*f1 , as the second harmonic often has the highest power. In IR, the nonlinear target is illuminated by two signal sources at different frequencies, i.e. f1 and f2, resulting in a intermodulated return signal at m * f1 ± n * f2.

[0029] Historically, HR has dominated nonlinear radar systems, with applications including insect tracking, electronic surveillance, and search and rescue. However, IR has gained attention as an alternative, as it avoids issues related to receiver linearization and provides more flexibility in system design. Multitone IR systems are developed, where multiple tone signals are transmitted from a single transceiver, and various-order intermodulation products are detected at the receiver.

[0030] The present disclosure introduces a dual-mode radar system that combines harmonic and intermodulation operation, incorporating the concept of an auxiliary helper transmitter. This system may operate as an Frequency Modulated Continuous Wave, FMCW, harmonic radar without separate auxiliary transmitter or as a combined harmonic and intermodulation radar with the auxiliary transmitter.

[0031] In an example, the radar may use a 9.3GHz transmitter for a chirp signal and a separate auxiliary transmitter generating a tone signal at 9.5GHz. This approach provides increased flexibility and coverage while maintaining the benefits of both harmonic and intermodulation radar modes. A specific implementation of the radar is further discussed with respect to the figures.

[0032] In an example, the receiver is arranged for simultaneously receiving said harmonic return signal, said harmonic return having a harmonic frequency equal to two times said first frequency, and for receiving said intermodulated return signal, said intermodulated return signal having an intermodulated frequency equal to said first frequency plus said second frequency.

[0033] The preference for utilizing the second harmonic return signal, which is twice the frequency of the illuminating signal, i.e. the first signal, may be attributed to several practical advantages. Firstly, the second harmonic tends to exhibit higher signal strength compared to other harmonic components. This improved signal strength may simplify the detection process and enhances the radar's ability to discern targets, especially over longer distances. Secondly, the second harmonic may offer improved signal clarity. Its distinct and easily identifiable frequency component may streamline the radar's design and signal processing. This reduces the likelihood of signal confusion and may ensure cleaner and more dependable return signal.

[0034] Additionally, selecting the second harmonic may minimize the risk of interference from higher-order harmonics, which could otherwise introduce unwanted complexity and noise into the return signal, potentially compromising the radar's accuracy.

[0035] The intermodulated return signal may have an intermodulated frequency equal to said first frequency plus said second frequency. This enables that the frequency of the intermodulated return signal and the frequency of the harmonic return signal are close to one another, thereby enabling a single receiver to receive both signals simultaneously.

[0036] In a further example, the receiver system comprises: one receiving antenna, said receiving antenna being arranged to receive both said harmonic signal and said intermodulated signal, and said one receiving antenna being connected to said receiver.

[0037] The antenna may be designed to operate over the frequency range that encompasses the harmonic and intermodulation frequencies. This means the antenna may be capable of efficiently receiving signals at the harmonic frequencies of the first signal as well as one or more of the intermodulation products.

[0038] When, for example, the second harmonic and the intermodulation product are close in frequency, the antenna can be optimized to receive signals within a narrower bandwidth. This can result in improved signal reception and sensitivity, as the antenna's design can be more precisely tuned to the specific frequencies of interest.

[0039] A narrower frequency range for the antenna may allow for a more efficient and focused antenna design, which can lead to better gain and directivity for the targeted frequencies.

[0040] Further, having closely aligned frequencies can make it easier to distinguish between the desired second harmonic signal and the intermodulation product. This reduces the risk of interference and may simplify signal processing. In a further example, the first signal comprises a carrier frequency at said first frequency and having a bandwidth B, wherein said second frequency is different to said first frequency ± 31 * bandwidth B.

[0041] It is advantageous is the second frequency is not within the frequency range of the first signal. This may cause conflicts w.r.t. the harmonic return signal and the intermodulation return signal.

[0042] In a further example, the main transmitter and at least one auxiliary transmitter are collocated in space.

[0043] Both transmitters may, for example, be placed on the same carrier. In a specific example, multiple auxiliary transmitters are provided.

[0044] In another example, said radar system comprises one transmitting antenna connected to both said main transmitter and said auxiliary transmitter.

[0045] In yet another example, the main transmitter and said at least one auxiliary transmitter are distributed in space.

[0046] In yet another example, the receiver comprises: a mixer for down converting said received harmonic signal and said received intermodulated signal; a diplexer arranged for separating said down converted received harmonic signal from said down converted received intermodulated signal for further processing.

[0047] Firstly, the receiver may incorporate a mixer, which may play a role in down-converting the received harmonic signal and the received intermodulated signal. This down-conversion process may be of importance as it transforms the initially high- frequency signals into lower-frequency versions, which are more amenable to subsequent analysis and processing.

[0048] Secondly, the receiver features a diplexer, strategically positioned to fulfill the task of segregating the down-converted received harmonic signal from the down-converted received intermodulated signal. This separation may be of importance, as it ensures that each signal is channeled to the appropriate pathway for further processing and examination. The diplexer's role in guiding these signals accurately facilitates the efficient and distinct analysis of the harmonic and intermodulated components within the radar system.

[0049] In yet another example, the radar further comprises: said object being a non-linear tag arranged for producing said harmonic return signal and said intermodulated return signal based on said first signal and said second signal.

[0050] The above described an example of a radar having an object being a non-linear tag, which is responsible for generating both a harmonic return signal and an intermodulated return signal. These signals are produced in response to two specific input signals, referred to as the first signal and the second signal.

[0051] The non-linear tag is a component of the radar system and exhibits a unique property of non-linearity, meaning that its response is not directly proportional to its input signals. When the radar system transmits the first signal and the second signal toward the non-linear tag, the tag reacts by producing two distinct types of return signals.

[0052] The first of these return signals is the harmonic return signal, which is generated at, for example, twice the frequency of the first signal. The second signal, known as the intermodulated return signal, is created based on the interaction between the first signal and the second signal. This intermodulated signal is produced at a frequency that results from the mixing or modulation of the two input signals.

[0053] In a second aspect of the present disclosure, there is provided a method of operating a dual-mode radar in accordance with any of the previous examples, wherein said method comprises the steps of: transmitting, by said main transmitter, said first signal towards said object; transmitting, by said at least one auxiliary transmitter, simultaneously with said first signal, said second signal towards said object; simultaneously receiving, by said receiver, said harmonic return signal and said intermodulated return signal.

[0054] It is noted that the advantages as explained with respect to the first aspect of the present disclosure, being the dual-mode radar, are also applicable to the second aspect of the present disclosure, being the method of operating such a dualmode radar.

[0055] In an example, the step of simultaneously receiving further comprises: simultaneously receiving said harmonic return signal, said harmonic return having a harmonic frequency equal to two times said first frequency, with receiving of said intermodulated return signal, said intermodulated return signal having an intermodulated frequency equal to said first frequency plus said second frequency.

[0056] In a further example, the receiver system comprises one receiving antenna, said step of simultaneously receiving further comprises: simultaneously receiving both said harmonic signal and said intermodulated signal using said one receiving antenna.

[0057] In yet another example, the first signal comprises a carrier frequency at said first frequency and having a bandwidth B, wherein said second frequency is different to said first frequency ± 31 * bandwidth B.

[0058] In a further example, the method further comprises the steps of; down converting, by a mixer, said received harmonic signal and said received intermodulated signal; separating, by a diplexer, said down converted received harmonic signal from said down converted received intermodulated signal for further processing.

[0059] In an even further example, the radar further comprises a non-linear tag, said method comprising the step of: producing, by said non-linear tag, said harmonic return signal and said intermodulated return signal based on said first signal and said second signal.

[0060] The present disclosure is described in conjunction with the appended figures. It is emphasized that, in accordance with the standard practice in the industry, various features are not drawn to scale. In fact, the dimensions of the various features may be arbitrarily increased or reduced for clarity of discussion.

[0061] In the appended figures, similar components and / or features may have the same reference label. Further, various components of the same type may be distinguished by following the reference label by a dash and a second label that distinguishes among the similar components. If only the first reference label is used in the specification, the description is applicable to any one of the similar components having the same first reference label irrespective of the second reference label.

[0062] The above and other aspects of the disclosure will be apparent from and elucidated with reference to the examples described hereinafter.

[0063] Brief description of the drawings Fig. 1 discloses a schematic example of dual-mode radar in accordance with the present disclosure;

[0064] Fig. 2 discloses an example of a non-linear tag in accordance with the present disclosure;

[0065] Fig. 3 discloses an example of the first signal and the second signal;

[0066] Fig. 4 discloses an example of the harmonic return signal and the intermodulated return signal;

[0067] Fig. 5 discloses a block diagram of a dual-mode radar in accordance with the present disclosure.

[0068] Detailed description

[0069] It is noted that in the description of the figures, same reference numerals refer to the same or similar components performing a same or essentially similar function.

[0070] A more detailed description is made with reference to particular examples, some of which are illustrated in the appended drawings, such that the manner in which the features of the present disclosure may be understood in more detail. It is noted that the drawings only illustrate typical examples and are therefore not to be considered to limit the scope of the subject matter of the embodiments. The drawings are incorporated for facilitating an understanding of the disclosure and are thus not necessarily drawn to scale. Advantages of the subject matter as claimed will become apparent to those skilled in the art upon reading the description in conjunction with the accompanying drawings.

[0071] The ensuing description above provides preferred exemplary embodiment(s) only, and is not intended to limit the scope, applicability or configuration of the disclosure. Rather, the ensuing description of the preferred exemplary embodiment(s) will provide those skilled in the art with an enabling description for implementing a preferred exemplary embodiment of the disclosure, it being understood that various changes may be made in the function and arrangement of elements, including combinations of features from different embodiments, without departing from the scope of the disclosure. Unless the context clearly requires otherwise, throughout the description and the embodiments, the words "comprise," "comprising," and the like are to be construed in an inclusive sense, as opposed to an exclusive or exhaustive sense; that is to say, in the sense of "including, but not limited to." As used herein, the terms "connected," "coupled," or any variant thereof means any connection or coupling, either direct or indirect, between two or more elements; the coupling or connection between the elements can be physical, logical, electromagnetic, or a combination thereof. Additionally, the words "herein," "above," "below," and words of similar import, when used in this application, refer to this application as a whole and not to any particular portions of this application. Where the context permits, words in the Detailed Description using the singular or plural number may also include the plural or singular number respectively. The word "or," in reference to a list of two or more items, covers all of the following interpretations of the word: any of the items in the list, all of the items in the list, and any combination of the items in the list.

[0072] These and other changes can be made to the technology in light of the following detailed description. While the description describes certain examples of the technology, and describes the best mode contemplated, no matter how detailed the description appears, the technology can be practiced in many ways. Details of the system may vary considerably in its specific implementation, while still being encompassed by the technology disclosed herein. As noted above, particular terminology used when describing certain features or aspects of the technology should not be taken to imply that the terminology is being redefined herein to be restricted to any specific characteristics, features, or aspects of the technology with which that terminology is associated. In general, the terms used in the following embodiments should not be construed to limit the technology to the specific examples disclosed in the specification, unless the Detailed Description section explicitly defines such terms. Accordingly, the actual scope of the technology encompasses not only the disclosed examples, but also all equivalent ways of practicing or implementing the technology under the embodiments.

[0073] Fig. 1 discloses a schematic example 1 of dual-mode radar in accordance with the present disclosure.

[0074] The dual-mode radar arranged for harmonic and intermodulation operation, said dual-mode radar comprising: a transmitter system 3 arranged for detecting an object, said transmitter system comprising: a main transmitter 3 arranged for transmitting a first signal towards said object, said first signal having a first frequency; at least one auxiliary transmitter 4 arranged for transmitting a second signal, simultaneously with said first signal, towards said object, said second signal having a second frequency, said second frequency being different, but in a same order of magnitude, to said first frequency; a receiver system 5, comprising a receiver 6, 7 arranged for simultaneously receiving a harmonic return signal corresponding to said first signal and receiving an intermodulated return signal corresponding to said first and second signal.

[0075] Fig. 2 discloses an example of a non-linear tag 11 in accordance with the present disclosure.

[0076] Nonlinear radar systems are a specialized class of radar systems designed for detecting and tracking objects in cluttered environments. Unlike conventional radar systems, which primarily deal with linear targets that respond to incident radiofrequency, RF, signals by producing echoes at the same central frequency, nonlinear radar systems operate with nonlinear targets. These targets produce return signals at frequencies different from the illuminating signal. This unique frequency separation between the transmit and receive signals provides an advantage in filtering out linear clutter, which typically remains concentrated at the transmit frequency.

[0077] Nonlinearity in radar can occur intentionally by attaching nonlinear tags to the target, as a result of processes like corrosion in metals, or due to inherent parasitic nonlinearities present in electronic devices. Depending on the specific implementation, nonlinear radar can take on several forms, with the two most common being harmonic radar, HR, and intermodulation radar, IR.

[0078] In HR systems, the radar transmitter emits an RF signal at a central frequency (f 1 ), and the receiver detects and processes a harmonic return at an integer multiple (n*f1), usually at the second harmonic (2*f1) due to its higher power. The choice of the second harmonic is a strategic one, as it often has the highest amplitude compared to other harmonic components. The mathematical representation of nonlinear target response suggests that at low incident power levels, where the signal magnitude (A) is small, the second harmonic (n = 2) dominates the response. The primary harmonic response can be simplified to a form that is directly proportional to the square of the input signal, making it easier to analyse and detect.

[0079] In IR systems, nonlinear targets are illuminated by a combination of two RF signals at different frequencies (f1 and f2). Here, the frequency f1 is used as this frequency is already presently used for the harmonic return signal. The above described interaction leads to a return signal with not only harmonic components but also intermodulation products at frequencies of m*f1 ± n*f2, where m and n are integers.

[0080] The second-order intermodulation product, corresponding to the frequencies f1 + f2 and |f2 - f1 |, may be of particular interest. When the amplitudes of the incident signals are roughly equal, the intermodulation cross-products may produce signals with a 6dB higher reflected power than the harmonic ones, making intermodulation radar particularly advantageous in such scenarios.

[0081] The above is disclosed in figures 3 and 4 of the present disclosure. Here, figure 3 shows the two transmitting signals, i.e. signal f1 and signal f2. Signal f1 may have a bandwidth “B”. Signal f2 may be a transmit tone.

[0082] The received signals are shown in figure 3. Here, figure 4 shows 22 the intermodulated return signal, i.e. f1 + f2, and shows the harmonic return signal, i.e. 2f 1. The harmonic return signal may have a bandwidth of 2 times B. The intermodulated return signal may have a bandwidth of B.

[0083] Fig. 5 discloses a block diagram of a dual-mode radar in accordance with the present disclosure.

[0084] The present disclosure is directed to an example of a dual-mode Frequency Modulated Continuous Wave, FMCW, harmonic radar. This radar system is designed to operate in both harmonic and intermodulation modes, allowing it to reap the benefits of both while accommodating the concept of an auxiliary helper transmitter.

[0085] Before diving into the specifics of the dual-mode system, it may be beneficial to discuss the principle of FMCW radar. FMCW radar, which stands for Frequency Modulated Continuous Wave radar, operates by transmitting a chirp waveform. This chirp is a continuous wave whose frequency changes linearly over time.

[0086] When this chirp signal is sent out and subsequently reflected by a target, it returns as a chirp with a frequency shift. The time delay between the transmitted and received chirps may be used to calculate the distance to the target, while the frequency shift provides velocity information. One of the advantages of FMCW radar is its ability to achieve high range resolution and system sensitivity with minimal signal processing requirements.

[0087] The dual-mode FMCW harmonic radar example of this disclosure is directed to a versatile radar system that combines the advantages of both harmonic and intermodulation operation. The system may, in a specific example, consist of an FMCW nonlinear radar unit equipped with a 9.3GHz transmitter that generates an 80MHz chirp. Additionally, it may feature a dual-branch receiver capable of receiving harmonic return signals at 18.6GHz and second-order intermodulation signals at 18.8GHz. To produce the intermodulation signal, a separate auxiliary transmitter may generate a tone signal at 9.5GHz.

[0088] This dual-mode system offers great flexibility. When the auxiliary transmitter is introduced, the system can harness the benefits of both harmonic and intermodulation modes. This innovative approach significantly enhances the radar's adaptability and target detection capabilities.

[0089] The auxiliary transmitter concept may play an important role in this system. It may enable the spatial separation of the main radar module and the auxiliary transmitter. This spatial flexibility offers various advantages. For instance, the auxiliary transmitter can be made compact and lightweight since it only needs to transmit an unmodulated carrier signal. This portability allows for the deployment of the auxiliary transmitter on mobile platforms, expanding the radar's coverage area. Furthermore, the present disclosure is directed to the concept that multiple auxiliary helper transmitters can be used to boost the system's coverage or increase the tag output incrementally.

[0090] The dual-mode FMCW harmonic radar prototype is depicted in Fig. 4. It is comprised of a radar transceiver, consisting of both transmitting and receiving modules. The transmit module generates a chirp signal that spans a frequency range from 9.3GHz to 9.38GHz, having a carrier frequency of 9.34 GHz, with a sweeping bandwidth of 80MHz. This chirp may be designed to operate with a duty cycle <100%, meaning that it transmits for only a part of the duty cycle and remain off the rest of it.

[0091] An aspect of this radar is the integration of an external transmitter, referred to as a "helper transmitter." This external transmitter plays a role in producing intermodulation responses from nonlinear targets. It generates a stable tone signal at a frequency of 9.5GHz (f2).

[0092] The helper transmitter's signal results in the creation of two distinct chirps - a harmonic return chirp extending from 18.60GHz to 18.76GHz and an upperband intermodulation chirp ranging from 18.80GHz to 18.88GHz. These frequency selections are deliberate, as they ensure that both the harmonic and intermodulation chirps are close enough in frequency to share the same receive antenna and be processed together up to the intermediate frequency, IF. However, there's sufficient separation to distinguish them at a later stage of processing.

[0093] In the receiving section of the radar, the signal received from the target contains both the harmonic and intermodulation chirps. The initial step is to mix this received signal with a 18.60GHz to 18.76GHz sweep signal generated by the local oscillator, LO, of the transmitter. This initial mixing isolates the harmonic beat frequency, which is the difference in frequency between the transmit and receive chirps due to the propagation delay, preparing it for amplification, filtering, and further processing by the digitizer.

[0094] The next step involves a diplexer, which serves the purpose of segregating the harmonic beat frequency output from the signal that contains the intermodulation components. However, the signal with intermodulation components is now a mixture of the harmonic frequency sweep and the linear sweep. To extract the intermodulation beat frequency, additional down-conversion steps may be necessary.

[0095] This down-conversion process occurs in two stages. In the first stage, the mixed signal is combined with the 9.30GHz to 9.38GHz sweep signal from the transmitter's LO. This action removes the linear sweep and shifts the beat frequency output to 9.5GHz. Subsequently, in the second stage, it is further down-converted to its original frequency using an additional 9.5GHz LO.

[0096] Two separate 9.5GHz LOs may be used, one at the helper transmitter and another at the radar receiver. Ensuring the precise synchronization of these LOs may be of importance, as any frequency difference between them directly affects the accuracy of the estimated beat frequency. Finally, the two beat frequency outputs are digitized and processed.

[0097] It is noted that multiple auxiliary transmitters may be comprised by the dual-mode radar in accordance with the present disclosure. At least one of those auxiliary transmitters is arranged for transmitting the second signal, simultaneously with said first signal. However, the present disclosure also encompasses the situation wherein, on top of that, auxiliary transmitter(s) are present that transmit the first signal.

[0098] To reduce the number of claims, certain aspects of the technology are presented below in certain claim forms, but the applicant contemplates the various aspects of the technology in any number of claim forms. For example, while some aspect of the technology may be recited as a computer-readable medium claim, other aspects may likewise be embodied as a computer-readable medium claim, or in other forms, such as being embodied in a means-plus-function claim.

[0099] In the description above, for the purposes of explanation, numerous specific details are set forth in order to provide a thorough understanding of implementations of the disclosed technology. It will be apparent, however, to one skilled in the art that embodiments of the disclosed technology may be practiced without some of these specific details.

[0100] Other variations to the disclosed embodiments can be understood and effected by those skilled in the art in practicing the claimed invention, from a study of the drawings, the disclosure and the appended claims. In the claims, the word “comprising” does not exclude other elements or steps, and the indefinite article “a” or “an” does not exclude a plurality. The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measures cannot be used to advantage. Any reference signs in the claims should not be construed as limiting the scope thereof.

Claims

CLAIMS1. A dual-mode radar arranged for harmonic and intermodulation operation, said dual-mode radar comprising: a transmitter system arranged for detecting an object, said transmitter system comprising: a main transmitter arranged for transmitting a first signal towards said object, said first signal having a first frequency, f1 ; at least one auxiliary transmitter arranged for transmitting a second signal, simultaneously with said first signal, towards said object, said second signal having a second frequency, f2, said second frequency being different, but in a same order of magnitude, to said first frequency; wherein said first signal comprises a carrier frequency at said first frequency and having a bandwidth B, wherein said second frequency is a tone signal, wherein said second frequency is not within a frequency range of the first signal having said bandwidth B; a receiver system, comprising a receiver arranged for simultaneously receiving a harmonic return signal corresponding to said first signal and receiving an intermodulated return signal corresponding to said first and second signal.

2. A dual-mode radar in accordance with claim 1 , wherein said receiver is arranged for simultaneously receiving said harmonic return signal, said harmonic return having a harmonic frequency equal to two times said first frequency, and for receiving said intermodulated return signal, said intermodulated return signal having an intermodulated frequency equal to said first frequency plus said second frequency.

3. A dual-mode radar in accordance with any of the previous claims, wherein said receiver system comprises: one receiving antenna, said receiving antenna being arranged to receive both said harmonic signal and said intermodulated signal, and said one receiving antenna being connected to said receiverwherein said one receiving antenna is arranged to receive said hormonic signal ranging from a frequency 2*f1-B to 2*f1+B; wherein said one receiving antenna is further arranged to receive said intermodulated signal ranging from a frequency f 1 +f2-B / 2 to f1+f2+B / 2.

4. A dual mode radar in accordance with any of the previous claims, wherein said dual mode radar is a dual-mode Frequency Modulated Continuous Wave, FMCW, harmonic radar, wherein said first signal is a chirp waveform whose frequency changes linearly over time,Wherein the receiver system is arranged to calculate a distance to the object based on a time delay between the transmitted and received chirps.

5. A dual-mode radar in accordance with any of the previous claims, wherein said main transmitter and said at least one auxiliary transmitter are collocated in space.

6. A dual-mode radar in accordance with claim 5, wherein said radar system comprises one transmitting antenna connected to both said main transmitter and said auxiliary transmitter.

7. A dual-mode radar in accordance with any of the claims 1 - 4, wherein said main transmitter and said at least one auxiliary transmitter are distributed in space.

8. A dual-mode radar in accordance with any of the previous claims, wherein said receiver comprises: a mixer for down converting said received harmonic signal and said received intermodulated signal; a diplexer arranged for separating said down converted received harmonic signal from said down converted received intermodulated signal for further processing.

9. A dual-mode radar in accordance with any of the previous claims, wherein said radar further comprises: said object being a non-linear tag arranged for producing said harmonic return signal and said intermodulated return signal based on said first signal and said second signal.

10. A method of operating a dual-mode radar in accordance with any of the previous claims, wherein said method comprises the steps of: transmitting, by said main transmitter, said first signal towards said object; transmitting, by said at least one auxiliary transmitter, simultaneously with said first signal, said second signal towards said object; simultaneously receiving, by said receiver, said harmonic return signal and said intermodulated return signal.

11. A method in accordance with claim 10, wherein said step of simultaneously receiving further comprises: simultaneously receiving said harmonic return signal, said harmonic return having a harmonic frequency equal to two times said first frequency, with receiving of said intermodulated return signal, said intermodulated return signal having an intermodulated frequency equal to said first frequency plus said second frequency.

12. A method in accordance with any of the claims 10 - 11 , wherein said receiver system comprises one receiving antenna, said step of simultaneously receiving further comprises: simultaneously receiving both said harmonic signal and said intermodulated signal using said one receiving antenna.

13. A method in accordance with any of the claims 10 - 12, wherein said first signal comprises a carrier frequency at said first frequency and having a bandwidth B, wherein said second frequency is different to said first frequency ± 31 * bandwidth B.

14. A method in accordance with any of the claims 10 - 13, wherein said method further comprises the steps of; down converting, by a mixer, said received harmonic signal and said received intermodulated signal; separating, by a diplexer, said down converted received harmonic signal from said down converted received intermodulated signal for further processing.

15. A method in accordance with any of the claims 10 - 14, wherein said radar further comprises a non-linear tag, said method comprising the step of: producing, by said non-linear tag, said harmonic return signal and said intermodulated return signal based on said first signal and said second signal.

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