Circuit and method for signal generation for a ground penetrating radar

Abstract

According to various aspects, a circuit (100) for signal generation is provided, wherein the circuit (100) has: a first signal generator (102) for generating a first broadband signal (122); a second signal generator (104) for generating a second narrowband signal (124); a splitter (106) designed to receive the second signal (124) and to generate a third signal (126) and a fourth signal (128) which have a phase offset to one another; and a mixer (110) which is designed to: mix the first signal (122) and the third signal (126) with one another in order to generate a fifth signal (132); and mix the first signal (122) and the fourth signal (128) with one another in order to generate a sixth signal (134). The fifth signal and the sixth signal have the same phase offset to one another as the third signal and the fourth signal.

Description

[0001] P96572 1

[0002] Description

[0003] Circuit and method for signal generation

[0004] Various aspects concern a circuit and a method for signal generation, e.g. for use in a ground-penetrating radar system.

[0005] In general, ground-penetrating radar (GPR) is a type of detection system based on the emission and reception of electromagnetic waves to investigate the subsurface. Specifically, a ground-penetrating radar system relies on the fact that at an interface between materials with different electromagnetic properties (e.g., different dielectric permittivity, different electrical conductivity, etc.), at least some of the electromagnetic waves are reflected back to the radar system. The travel time of the waves, as well as variations in their amplitude, allow information about the composition of the subsurface to be obtained and the presence of objects or other geological formations to be detected. Ground-penetrating radar is thus a non-invasive technique with many different applications, e.g., for engineering studies (e.g.,(for structural evaluation), archaeological studies, geological studies, and the like. Therefore, developments in ground-penetrating radar systems can be of interest for further progress in many application areas.

[0006] For some ground-penetrating radar (GPR) applications, desirable characteristics for the underground radar signals may include a relatively low frequency and a relatively large bandwidth. The penetration depth of the radar signals can be inversely proportional to the frequency, so a lower frequency allows for deeper penetration into the ground. Furthermore, the resolution of the radar measurement is directly related to the bandwidth, so a larger bandwidth ensures better resolution for better differentiation of interfaces and objects.

[0007] However, it is not easy to generate signals that fulfill both desirable properties. For example, it is relatively easy to generate signals with a relatively large bandwidth, but only at relatively high frequencies, which do not allow for deep ground penetration. Similarly, it is relatively easy to generate signals with a low frequency, but only with a limited bandwidth, which therefore offers only limited resolution.

[0008] Current circuit topologies for quadrature transceivers can be broadly categorized into narrowband and broadband applications. For specialized communication applications, common narrowband topologies based on branch-line couplers, polyphase filters, injection-locked oscillators, and variations thereof are usually sufficient. For broadband applications such as radar and measurement systems or software-defined radio (SDR), quadrature local oscillator (LO) generator topologies based on fast logic gates are common. Frequency dividers or flip-flops are typically used for this purpose.

[0009] The aforementioned narrowband solutions cannot achieve a large bandwidth. Known broadband solutions based on logic gates require a way to reset the logic states to ensure a reproducible phase response of the output signals after reconfiguration or reactivation of the oscillator. Such a topology usually requires switching configurations or frequency paths to change to a different frequency and is therefore inherently slow.

[0010] Aspects of the present disclosure relate to a circuit which is adapted to receive signals with a low frequency and a wide bandwidth under P96572 3

[0011] The use of a simple circuit architecture provides this capability. In particular, the circuit topology can be based on the realization that phase-shifted signals having an initial frequency can be combined (e.g., mixed) with another signal having a large bandwidth to obtain phase-shifted signals that maintain the large bandwidth in a shifted frequency range.

[0012] By appropriately choosing the initial frequency of the phase-shifted signals and the frequencies of the subsequent signal, signals with a large bandwidth at a desired frequency, e.g. a low frequency, can be generated.

[0013] The circuit architecture can thus include a first circuit for generating the broadband signal and a second circuit for generating the (narrowband) phase-shifted signals. The circuit architecture can further include one or more mixers for mixing the phase-shifted signals and the broadband signal together to obtain broadband signals as output, which have a frequency determined by the combination of the frequency of the phase-shifted signals and the frequency of the broadband signal. In some cases, subtractive mixing (downmixing) can shift the frequency of the broadband signal into a lower frequency range.

[0014] In subtractive combination, the phase-shifted signals can therefore have a frequency equal to or higher than the upper frequency of the broadband signal's frequency band. For example, the frequency of the phase-shifted signals can be equal to the upper frequency of the frequency band to lower the lower frequency of the resulting signal to 0 Hz. Conversely, the frequency of the phase-shifted signals can be higher than the upper frequency to lower the lower frequency of the resulting signal to a desired frequency greater than 0 Hz. The frequencies can thus be adjusted to flexibly adapt the frequency of the resulting output signals.

[0015] Down-conversion is the most relevant application for the circuit architecture described here, for providing low-frequency, wide-bandwidth signals. However, it is understood that the circuit described herein can, in principle, also be configured to enable up-conversion of the signals, thereby shifting the broadband signal to a higher frequency.

[0016] In the configuration described herein, the phase shift prior to mixing ensures that the imposed phase shift is retained in the resulting broadband low-frequency signals. This configuration simplifies the provision of phase-shifted signals, which are commonly used for signal transmission (and signal reception).

[0017] In a preferred configuration, the phase-shifted signals can exhibit the in-phase component (I) and the quadrature component (Q) of a quadrature signal. Intuitively, a first phase-shifted signal can be the I signal, and a second phase-shifted signal can be the Q signal. For example, the first phase-shifted signal can have a phase of 0°, and the second phase-shifted signal can have a phase of 90°. For example, the circuit can include a quadrature coupler configured to generate the in-phase and quadrature components. Given their advantageous properties for signal transmission, the use of quadrature signals may be the most relevant scenario. However, it is understood that the strategy described here can, in principle, be applied to any suitable phase shift.

[0018] As is generally known in engineering, the in-phase signal (I) and the quadrature signal (Q) can be sinusoidal signals with the same frequency but 90° out of phase with each other (e.g., the I signal can be a cosine and the Q signal a sine). By varying the amplitude of the I signal and / or the Q signal and then adding the signals, modulation of the resulting waveform can be achieved, thereby adjusting the characteristics of the transmitted signal.

[0019] In various aspects, the signal generator can generate the broadband signal by means of a frequency sweep. Visually, the signal generator can be configured to perform a frequency sweep from a start frequency to an end frequency, and the signal frequency can increase (e.g., monotonically) from the start frequency to the end frequency, thus producing a wide-bandwidth signal. For example, the frequency sweep (in other words, the frequency sweep) can have a continuous ramp or frequency jumps. The use of a frequency sweep offers a solution that can be implemented with a compact and simple circuit. It is understood, however, that the broadband signal can be provided in any suitable way.

[0020] In some aspects, the circuit topology can therefore enable the generation of quadrature oscillator signals over a wide bandwidth and with a continuous frequency ramp or with fast frequency jumps.

[0021] Depending on various aspects, the generator topology can utilize two phase-locked loops (PLLs) as oscillators. One of the PLLs can generate a frequency sweep with a bandwidth of, for example, one octave, such as from 8 GHz to 13.99 GHz. Bandwidths significantly greater than one octave are difficult to achieve with commercially available voltage-controlled oscillators (VCOs). The second PLL can generate a constant local oscillator (LO) frequency greater than the maximum sweep frequency, for example, 14 GHz. The LO signal can be amplified by a quadrature coupler (such as a branch-line coupler) at 0° and 90°.

[0022] The components are split. The two quadrature LO signals are then each downmixed with the sweep signal. This results in two signals in the low frequency range (e.g., from 0.01 GHz to 6 GHz), with a bandwidth of just over 9 octaves. The phase difference of the two LO signals is superimposed on the downmixed signals, creating a broadband sweep as a quadrature signal.

[0023] Due to manufacturing tolerances, the quadrature coupler used may generate a phase difference of exactly 90° at a shifted frequency. Because both PLLs are adjustable, the LO frequency can be adjusted accordingly, thus calibrating the phase offset of the output signals. Furthermore, hardware-based phase calibration to compensate for manufacturing tolerances is possible if both oscillator components of the topology are controllable.

[0024] In various aspects, the circuit can also be coupled to a transmitter circuit to use the generated signals for signal transmission. Intuitively, the circuit can be part of a transmitter front end or coupled to one, and the resulting signals (e.g., the broadband low-frequency signals) can be used for signal transmission. In some aspects, the circuit can additionally or alternatively be coupled to a receiver circuit to use the generated signals for signal reception. For example, the circuit can be part of a receiver front end or coupled to one, and the resulting signals can be used for signal reception.

[0025] For example, a modulator or transmitter can follow the signal generation circuit to send signals. In this scenario, the topology can thus be a broadband and quickly adjustable P96572 7.

[0026] Representing the quadrature transceiver frontend. The quadrature LO signals can also be used for further circuitry on the transmitter side, such as vector modulators, antenna beamforming, and circularly polarized antenna radiation.

[0027] The broadband quadrature signals can also be used as a local oscillator (LO) for a quadrature downconverter. Conversely, the broadband sweep can be used as an LO signal for the mixers of the receiver stage to generate quadrature baseband signals.

[0028] In some aspects, the circuit topology can therefore be set up to generate a very wideband quadrature signal using a narrowband quadrature LQ generator and a wideband useful signal generator, which can then in turn be used as an LO for the mixers on the receiver side.

[0029] The topology could also be applied to higher frequency ranges, for example by using frequency multipliers to further increase the absolute bandwidth before downmixing.

[0030] On the one hand, component selection is simpler than with the logic module topology, since PLLs, mixers, and quadrature couplers are standard modules that are available or can be designed for various frequency ranges. On the other hand, this topology also works for broadband signals with amplitude information, which is not usually possible with frequency dividers. Additionally, there is no problem of phase inversion due to incorrect initial states of the frequency dividers. Finally, the phase can be calibrated as described previously.

[0031] In a preferred configuration, a ground-penetrating radar system may include the signal generation circuitry described herein. For example, the ground-penetrating radar system may have a transmitter front-end and / or a receiver front-end, P96572 8, which includes or is coupled to the signal generation circuitry. For example, a processing circuitry of the ground-penetrating radar system may be configured to control the transmission of low-frequency signals to the ground and to process a reflected signal to obtain information about the subsurface.

[0032] The circuit topology can thus, in some aspects, represent a high-frequency frequency sweep generator for a very wide bandwidth FMCW ground-based radar. The signal can be present as quadrature components (two signals of the same instantaneous frequency with 0° and 90° phase shifts) to enable IQ demodulation in the receiver front end and, on the other hand, to transmit a circularly polarized signal using two broadband linearly polarized antennas in a cross configuration.

[0033] The use in a ground-penetrating radar system may be the most relevant application for the circuit architecture described herein. However, it is understood that the circuit can be used in any suitable system or application, e.g., in any system where broadband low-frequency signals may be advantageous. Further examples of the approach described here include its implementation in test equipment, signal generators, signal analyzers, and oscilloscopes.

[0034] The term "signal" can be used here in its usual sense to describe a time-varying voltage, a time-varying current, or a time-varying electromagnetic wave. For example, a "signal" can have a time-varying electric current or a time-varying voltage that generates electromagnetic waves that propagate in a transmission medium (e.g., the ground). The term "signal" can therefore be used to describe the signal during processing in a circuit as well as during propagation in the P96572 9

[0035] to describe the transmission medium. For example, the term "signal" can describe the signal in the form of alternating current or alternating voltage in a circuit, as well as in the form of an electromagnetic wave propagating in the transmission medium. The term "signal" can also describe a digital signal that is processed by a digital processor, for example, a digital signal that is then converted into an analog signal for transmission as an electromagnetic wave, or a digital signal that is converted from an analog signal that originates from an electromagnetic wave.

[0036] The term "phase-shifted" can be used here in its usual sense to describe signals that have a phase difference with each other. For example, a first signal and a second signal can be described as "phase-shifted" signals if they have a phase difference greater than 0°. Specifically, the first signal and the second signal can have a phase difference other than 0°, 180°, or any integer multiple thereof. Thus, the first signal and the second signal can be phase-shifted. Visually, the first phase of the first signal can differ from the second phase of the second signal by a value (a phase shift) that is not 0°, 180°, or any integer multiple of 180°. "Phase-shifted" signals can also be referred to as "phase-displaced" signals.

[0037] The term "broadband" can be used here to describe a signal that has or can traverse a multitude of frequencies distributed across a frequency band. A broadband signal can intuitively have a large bandwidth; for example, the frequency band can have a bandwidth above a predefined threshold. In general, the term "broadband" can be used to distinguish a signal from another signal that has a single frequency or, more generally, a much smaller bandwidth.

[0038] Compare to a "broadband" signal. For example, the term "broadband" can describe a signal where the ratio of bandwidth to center frequency is at least 30%, at least 40%, or at least 50%. For example, the term "broadband" can describe a signal with a bandwidth of at least one octave, at least two octaves, at least three octaves, or more than five octaves. For example, the term "broadband" can describe a signal where the ratio of bandwidth to center frequency is 100%. As a numerical example, such a signal could have a center frequency of 10 GHz and a bandwidth of 10 GHz, corresponding to a range from a lower frequency of 5 GHz to an upper frequency of 15 GHz.

[0039] In some aspects, the term "broadband" can be used to distinguish a signal from another signal with a smaller bandwidth, e.g., another signal with a single frequency or another signal where the ratio of the bandwidth size to the center frequency is less than 30%, for example, less than 10%, for example, less than 5%. Such a different signal can, for example, be described as a "narrowband" signal.

[0040] The term "low frequency" can be used here to describe a (low-frequency) signal that has at least one frequency close to 0 Hz, e.g., at least one frequency below a predefined threshold. In general, the term "low frequency" can be used to distinguish a signal from another signal that has a frequency in a higher frequency range. For example, the term "low frequency" can describe a signal with a single frequency or a signal with a multitude of frequencies, where at least the lowest frequency is close to 0 Hz or below the predefined threshold. As a numerical example, the term P96572 11

[0041] “Low frequency” describes a signal with at least one frequency below 100 MHz, for example below 10 MHz, for example below 1 MHz.

[0042] The term "sweep" can be used here to describe a signal whose frequency sweeps through a predetermined range. For example, a frequency sweep (or frequency sweep) can be a signal that exhibits a multitude of frequencies which increase (e.g., periodically and continuously) from a starting frequency to a final frequency. A frequency sweep can also be referred to as a frequency sweep in this context.

[0043] Exemplary versions of the invention are shown in the figures and are explained in more detail below.

[0044] They show:

[0045] Figure 1 shows a circuit for signal generation in a schematic view, according to various aspects;

[0046] Figures 2A and 2B show exemplary configurations of the circuit for signal generation in a schematic view, according to various aspects;

[0047] Figure 3 shows exemplary signals for use in signal generation, according to various aspects;

[0048] Figures 4A and 4B show exemplary broadband signals for use in signal generation, according to various aspects;

[0049] Figures 5A and 5B show exemplary components of the signal generation circuit in a schematic view, according to various aspects;

[0050] Figure 6A shows a system comprising the signal generation circuit and a transmitter circuit in a schematic view, according to various aspects; P96572 12

[0051] Figure 6B shows an exemplary implementation of the system of

[0052] Figure 6A in a schematic view, according to various aspects;

[0053] Figure 7 shows a ground-penetrating radar system comprising the signal generation circuit in a schematic view, according to various aspects; and

[0054] Figure 8 shows a schematic flow diagram of a signal generation process, according to various aspects.

[0055] The following detailed description refers to the accompanying drawings, which illustrate specific details and embodiments in which the invention can be implemented. It is understood that other embodiments may be used and structural or logical modifications may be made without deviating from the scope of protection of the present invention. It is understood that the features of the various exemplary embodiments described herein may be combined with one another, unless specifically stated otherwise. The following description is therefore not to be interpreted restrictively, and the scope of protection of the present invention is defined by the attached claims.

[0056] FIG. 1 illustrates a circuit 100 for signal generation in a schematic view, according to various aspects. It is understood that the representation in FIG. 1 may be simplified and the circuit 100 may have additional components.

[0057] In some aspects, circuit 100 can be an analog circuit, and the components of circuit 100 (e.g., signal generators 102, 104, splitter 106, mixer 110, etc.) can be analog components. Similarly, the signals generated / processed in circuit 100 can be analog signals. Analog signals can be the P96572 13

[0058] Processing is facilitated by circuit 100. However, it is understood that circuit 100 can be a digital circuit in other aspects, and that the components of circuit 100 can be configured as digital components that operate with digital signals. In other aspects, circuit 100 can have a combination of analog and digital components.

[0059] In some aspects, circuit 100 can be an integrated circuit; for example, the components of circuit 100 (e.g., signal generators 102, 104, splitter 106, mixer 110, etc.) can be integrated on the same circuit board, such as the same printed circuit board, or on the same substrate of an integrated circuit. In other aspects, circuit 100 can have discrete and separate components that are combined and coupled to implement the functionalities of circuit 100. In this scenario, the discrete components can, for example, be detachably coupled to each other, such as being detachably coupled to a circuit board.

[0060] Depending on various aspects, the circuit 100 can include a first signal generator 102, which is configured to generate (in other words, produce) a first signal 122. The first signal generator 102 can therefore be, or include, a first circuit configured to provide the first signal 122.

[0061] The first signal 122 can be a broadband signal. Therefore, the first signal 122 can have a multitude of first frequencies, which lie within a first frequency band. Visually, the first signal 122 can cover the first frequency band, for example, continuously or discretely. The multitude of first frequencies can thus be distributed within the first frequency band, for example, from a first lower frequency to a first upper frequency. The first lower frequency can be the lowest frequency of the first frequency band (the lower frequency value), and the first upper frequency can be the highest frequency of the first frequency band (the upper frequency value).

[0062] In general, the first signal 122 can have any suitable waveform. For example, the first signal 122 can have a sinusoidal waveform whose frequency varies from the lower frequency to the upper frequency. In some aspects, the first signal 122 can be a modulated signal. For example, the first signal 122 can have amplitude modulation to encode information within the first signal 122.

[0063] The parameters of the first signal 122, e.g. the bandwidth, the first lower frequency, the first upper frequency, the signal amplitude, any modulation (e.g. amplitude modulation), etc., can be adjusted according to the requirements of the specific application and the desired characteristics of the signals 132, 134 output by the circuit 100.

[0064] As already mentioned, the first signal 122 can be a broadband signal. For example, the first signal generator 102 can be configured such that the bandwidth ratio to the center frequency of the first signal 122 is at least 30%, for example at least 40%, for example at least 50%, for example at least 100%. For example, the first signal 122 can have a bandwidth of one octave, which can be achieved with commercially available components.

[0065] As numerical examples, the first frequency band can have an initial bandwidth in a range from 1 GHz (as the lower frequency) to 50 GHz (as the upper frequency). For example, the first bandwidth can be in a range from 2 GHz (as the lower frequency) to 20 GHz (as the upper frequency), for example, in a range from 5 GHz to 15 GHz, or for example, in a range from 6 GHz to 14 GHz (e.g., up to 13.99 GHz). A bandwidth of 6 GHz to 14 GHz can be easily achieved with commercially available components (e.g., a P96572 or a standard VCO) and thus offers an inexpensive implementation of the proposed topology.

[0066] According to various aspects, the circuit 100 can further comprise a second signal generator 104, which is configured to generate (in other words, to produce) a second signal 124. The second signal generator 104 can thus comprise a second circuit, which is configured to provide the second signal 124.

[0067] The second signal 124 can be a narrowband signal. Ideally, the second signal can have a single second frequency. In another scenario, the second signal 124 can have a second bandwidth that is much smaller than the first bandwidth. For example, the second signal 124 can have a frequency that deviates by less than 5% from the center frequency of the second signal 124, e.g., less than 1%. The second bandwidth can be, for example, less than 10% of the first bandwidth, e.g., less than 5%, e.g., less than 1%.

[0068] In general, the second signal 124 can have any suitable waveform. For example, the second signal 124 can have a sinusoidal waveform, oscillating at a single frequency (the second frequency). In some aspects, alternatively or in addition to the first signal 122, the second signal 124 can be a modulated signal. For example, the second signal 124 can have amplitude modulation to encode information within it.

[0069] The parameters of the second signal 124, e.g., the second frequency, the signal amplitude, any modulation (e.g., amplitude modulation), can be adjusted according to the requirements of the specific application and the desired characteristics of the signals 132, 134 output by the circuit 100. In a preferred configuration, the second P96572 16

[0070] The frequency can be greater than any of the first frequencies. For example, the second frequency can be equal to or greater than the first upper frequency. This can make it possible to obtain low-frequency, wide-bandwidth signals as output signals via a down-conversion process, which may be the most relevant application for the circuit topology.

[0071] It is understood, however, that in other types of applications the second frequency can be lower than one of the first frequencies, e.g., the second frequency can be lower than the first lower frequency. As another example, the second frequency can lie within the first frequency band. These configurations can be used, for example, in the case of upmixing to shift the signals into higher frequency ranges.

[0072] As numerical examples, the second frequency can be equal to the first frequency plus an additional delta, and the additional delta can be in the range of 0 GHz to 10 GHz, for example, in the range of 0.1 GHz to 5 GHz, or in the range of 1 GHz to 2 GHz. For example, the second frequency can be 14 GHz (e.g., if the first frequency is 13.99 GHz).

[0073] The first signal generator 102 and the second signal generator 104 can have any suitable configuration to provide the desired first signal 122 and the desired second signal 124. In a preferred configuration, the first signal generator 102 can have a first phase-locked loop and / or the second signal generator 104 can have a second phase-locked loop (see also FIG. 5B).

[0074] Phase-locked loops offer a robust and reproducible generation of signals with a desired frequency or bandwidth, thus enabling an efficient and accurate implementation of the strategy described herein. It is understood, however, that the first P96572 17

[0075] Signal generator 102 and / or the second signal generator 104 can be implemented according to any suitable technique to provide signals with a desired frequency or bandwidth, e.g. any technique that provides a stable frequency for the generated signal.

[0076] The circuit 100 can further comprise a splitter 106, which is configured to receive the second signal 124 and to generate a plurality of phase-shifted signals based on the second signal 124. Intuitively, the splitter 106 can output a plurality of signals that are copies of the second signal 124, each with a phase shift imposed upon it. As shown in FIG. 1, the splitter 106 can be configured to generate a third signal 126 and a fourth signal 128 based on the second signal 124, wherein the third signal 126 and the fourth signal 128 can be phase-shifted relative to each other. The splitter 106 can also be referred to here as a phase shifter.

[0077] Visually, the third signal 126 can have the second frequency and a third phase, and the fourth signal 128 can have the second frequency and a fourth phase, with the third and fourth phases exhibiting a phase shift from each other. The signals output by the splitter 106 (e.g., the third signal 126 and the fourth signal 128) can thus retain the frequency (and waveform) of the original second signal 124, and the splitter 106 can impose a predefined phase difference on the output signals 126 and 128.

[0078] It is understood that the output of the splitter 106 may, in some aspects, include further signals with additional phase shifts besides the third and fourth signals. It is also understood that the combined functions of the second signal generator 104 and the splitter 106 can be implemented as a single component (e.g., a single integrated circuit) and not with separate discrete components. P96572 18

[0079] The splitter 106 can thus be configured such that each of the output signals 126, 128 has a unique phase that differs from the phase of the other output signals. In this respect, the phase shift between the output signals can be freely adjusted depending on the desired application or the desired characteristics of the signals 132, 134 output by the circuit 100. In general, the splitter 106 can be configured such that the output signals 126, 128 have a phase difference to each other that differs from 0°, 180°, and integer multiples of 180°.

[0080] In a preferred configuration, the splitter 106 can be configured such that the signals 126 and 128 output by the splitter 106 have a phase difference of 90° to each other. Specifically, the splitter 106 can be configured such that the third phase of the third signal 126 is 0° and the fourth phase of the fourth signal 128 is 90° (or vice versa). In this scenario, the signals output by the splitter 106 can thus define a quadrature signal, where one signal (e.g., the third signal 126) is the in-phase component and another signal (e.g., the fourth signal 128) is the quadrature component. Such a configuration can represent the most relevant use case for the circuit topology by providing signals with suitable properties for use in signal transmission (e.g., for radar applications).

[0081] The splitter 106 can be implemented in any suitable way. In a preferred configuration, the splitter 106 can be a quadrature coupler or incorporate a quadrature coupler (see also FIG. 5A). The quadrature coupler can be tuned to the second frequency of the second signal 124 (e.g., to the center frequency of the second signal 124). In some aspects, the signal generator 104 (e.g., the PLL) can be adapted to the quadrature coupler. For example, the second frequency of the second signal 124 can be matched to the P96572 19

[0082] The frequency must be adjusted so that the quadrature coupler provides the 90° phase difference. For example, a calibration process can be performed to adjust the second frequency of the second signal 124 to obtain a frequency that matches the characteristics of the quadrature coupler. This eliminates potential manufacturing tolerances and inaccuracies.

[0083] It is understood, however, that the splitter 106 can be implemented according to any suitable technology. For example, the splitter 106 can contain several signal paths, each configured to receive a copy of the second signal 124. The splitter 106 can furthermore include a corresponding phase-shifting element along each signal path to impose a desired phase on the signal propagating along that path. For example, a phase-shifting element can impose a delay in the time domain on the signal to obtain a corresponding phase shift in the frequency domain.

[0084] For illustration, the first signal generator 102 can be configured to produce a broadband signal 122. The second signal generator 104 and the splitter 106 can be configured to produce a multitude of narrowband signals 126, 128 (e.g., a multitude of signals with a single frequency) that have a phase shift relative to each other. For example, the signal generator 104 and the splitter 106 can be configured to produce a narrowband quadrature signal (with a single frequency or, more generally, with a smaller bandwidth compared to the broadband signal 122).

[0085] The circuit 100 can further include a mixer 110, which is configured to receive the (broadband) signal 122 output by the first signal generator 102 and the phase-shifted (narrowband) signals 126, 128 output by the splitter 106 (e.g., the quadrature signal output by the splitter 106 P96572 20). Visually, inputs of the mixer 110 can be coupled to the first signal generator 102 and to the splitter 106 in order to receive the signals.

[0086] Mixer 110 can be configured to mix the signal 122 output by the first signal generator 102 and the signals 126 and 128 output by splitter 106. For example, mixer 110 can be configured to mix the first signal 122 and the third signal 126 to generate a fifth signal 132, and to mix the first signal 122 and the fourth signal 128 to generate a sixth signal 134. If splitter 106 outputs more than two signals 126 and 128, mixer 110 can be configured to mix these additional output signals with the first signal 122.

[0087] As shown in FIG. 1, in some aspects the mixer 110 can be understood as a mixer arrangement which has a first mixer 112 for mixing the first signal 122 with the third signal 126 and a second mixer 114 for mixing the first signal 122 with the fourth signal 128.

[0088] In some aspects, mixer 110 may only have the two mixers 112 and 114. In other aspects, mixer 110 may have additional mixers to mix further signals output by splitter 106 with the first signal 122.

[0089] In general, the mixer 110 can be configured to mix the signals such that the frequency of the resulting signals 132, 134 is defined by the mixture of the frequencies of the input signals 122, 126, 128. Intuitively, the mixer 110 can be configured such that the frequency of the fifth signal 132 and the frequency of the sixth signal 134 are defined by mixing the first frequencies with the second frequency.

[0090] In a preferred configuration (see also FIG. 3) the mixer 110 can be configured such that the frequency P96572 21 of the fifth signal 132 and the frequency of the sixth signal

[0091] 134 can be defined by subtracting the first frequencies from the second frequency. This allows the large bandwidth of the first signal 122 to be shifted into a lower frequency range, which is of particular importance for ground-penetrating radar applications.

[0092] In other aspects, the mixer 110 can be configured such that the frequency of the fifth signal 132 and the frequency of the sixth signal 134 are defined by a sum of the first frequencies and the second frequency. This allows the large bandwidth of the first signal 122 to be shifted into a higher frequency range.

[0093] The resulting signals 132 and 134 can thus maintain the phase relationship of the signals output by the splitter 106, and furthermore, their frequency can be shifted towards a desired frequency range, thereby providing a compact and resource-efficient architecture for signal generation. The resulting signals 132 and 134 can have the same frequencies within the same frequency band, where the frequency band has the same bandwidth as the first signal 122, but shifted into the desired frequency range.

[0094] Visually, the fifth signal 132 and the sixth signal 134 can have multiple (fifth) frequencies in a (fifth) frequency band that has the same bandwidth as the first frequency band of the first signal. The (fifth) frequency band can thus extend from a (fifth) lower frequency to a (fifth) upper frequency, which is defined by mixing the frequencies of the first signal 122 with the third signal 126 and with the fourth signal 128. The difference between the fifth upper frequency and the fifth lower frequency can be the same as the difference between the first upper frequency and the first lower frequency. P96572 22

[0095] Furthermore, the fifth signal 132 can have the same phase as the corresponding input signal, e.g., the third phase of the third signal 126. Similarly, the sixth signal 134 can have the same phase as the corresponding input signal, e.g., the fourth phase of the fourth signal 128. The fifth signal 132 and the sixth signal 134 can thus have the same phase shift as the third signal 126 and the fourth signal 128, e.g., 90°. In some respects, the fifth signal 132 and the sixth signal 134 can therefore define a quadrature signal, which has a large bandwidth in a desired (e.g., low) frequency range.

[0096] For illustration, the mixer 110 can be set up in such a way that it mixes the broadband signal 122 and the narrowband signals 126, 128 (e.g. the narrowband quadrature signal) together to obtain resulting broadband signals 132, 134 (e.g. a resulting broadband quadrature signal).

[0097] The aspects discussed in relation to a fifth signal 132 and a sixth signal 134 may apply accordingly to further signals output by splitter 106.

[0098] The signals output by mixer 110 can then be used for any suitable application, e.g., for signal transmission and signal reception (see also FIG. 6A and FIG. 6B). For example, circuit 100 can have a plurality of output terminals which are coupled to mixer 110, so that mixer 110 provides (e.g., supplies) the resulting signals 132, 134 to the output terminals. Other circuits that can use the signals can be coupled to circuit 100 at the output terminals.

[0099] According to various aspects, the circuit 100 can have more than two signal generators 102, 104, as shown in FIG. 2A and FIG. 2B. The use of additional signal generators can extend the capabilities of the P96572 circuit 23 to provide signals with different characteristics (e.g., different frequency ranges, different bandwidths, different phase shifts, etc.). It is understood that the aspects discussed with regard to FIG. 2A and 2B also apply accordingly to additional signal generators and additional signals.

[0100] For example, the circuit 200a, as shown in FIG. 2A, can include additional components to generate additional narrowband signals (e.g., an additional narrowband quadrature signal). For example, the circuit 200a can have a third signal generator 204 and a second splitter 206, which are configured to provide further phase-shifted signals, e.g., an eighth signal 226 and a ninth signal 228.

[0101] The third signal generator 204 can be configured to generate a seventh signal 224 with a seventh frequency, and the splitter 206 can be configured to generate, based on the seventh signal 224, the eighth signal 226 and the ninth signal 228 with the seventh frequency and a phase shift relative to each other (e.g. 90°).

[0102] The third signal generator 204 and the second splitter 206 can generally be configured in the same way as the second signal generator 104 and the (first) splitter 106. The frequency of the additional signals 224, 226, 228 can be flexibly adjusted relative to the second frequency. For example, the seventh frequency can be the same as the second frequency. The seventh frequency can also differ from the second frequency in other aspects, thus providing a frequency shift in a different range.

[0103] Visually, the eighth signal 226 can have the seventh frequency 224 and an eighth phase, and the ninth signal 228 can have the seventh frequency 224 and a ninth phase. For example, the eighth phase can be 0° and the ninth phase 90°, so that the eighth signal 226 and the ninth signal 228 have a phase shift of 90° and define another narrowband quadrature signal. As explained with reference to FIG. 1, other phase shifts can also be provided. For example, the phase shift between the eighth signal 226 and the ninth signal 228 can be the same as the phase shift between the third signal 126 and the fourth signal 128. In other aspects, the phase shift between the eighth signal 226 and the ninth signal 228 can differ from the phase shift between the third signal 126 and the fourth signal 128.

[0104] In this scenario, the circuit 200a can include a further mixer 210 (e.g., separate from mixer 110 or as part of mixer 110) which is configured to mix the first signal 122 and the eighth signal 226, and to mix the first signal 122 and the ninth signal 228. For example, the further mixer 210 can be a mixer arrangement that includes a third mixer 212 for mixing the first signal 122 with the eighth signal 226 and a fourth mixer 214 for mixing the first signal 122 with the ninth signal 228.

[0105] The additional mixer 210 can be configured to perform the same mixing as mixer 110, thereby shifting the first signal 122 in the same direction as mixer 110. Alternatively, the additional mixer 210 can be configured to perform the opposite mixing with respect to mixer 110, thereby shifting the first signal 122 in the opposite direction. For example, mixer 110 can perform a downward mix and the additional mixer 210 an upward mix, or vice versa.

[0106] As output, the further mixer 210 can provide resulting signals 232, 234 (e.g. a tenth signal 232 and an eleventh signal 234), which represent the phase difference as the input signals 226, 228 and the large bandwidth of the first P96572 25

[0107] Signal 122, which has been shifted into the desired frequency range, is retained. The tenth signal 232 and the eleventh signal 234 can thus exhibit a multitude of frequencies in a tenth frequency band that has the same bandwidth as the first signal 122 and is shifted in the frequency range defined by the mixing.

[0108] The frequency of the tenth signal 232 and the eleventh signal 234 can thus be defined by the combination of the seventh frequency of the seventh signal 224 and the first frequency of the first signal 122, e.g. by subtracting the first frequencies from the seventh frequency or by summing the first frequencies and the seventh frequency.

[0109] As another example, as shown in FIG. 2B, the circuit 200b can include further signal generators for generating broadband signals. For example, the circuit 200b can include a fourth signal generator 202, which is configured to generate another broadband signal 222, e.g., a twelfth signal 222 with a plurality of twelfth frequencies in a twelfth frequency band. In this scenario, the further mixer 210 can be configured to mix the twelfth signal 222 with the third signal 126 and the fourth signal 128 to generate resulting signals 236, 238 (e.g., a thirteenth signal 236 and a fourteenth signal 238) (e.g., another broadband quadrature signal).

[0110] The plurality of twelfth frequencies and the twelfth frequency band can be identical to the first frequencies and the first frequency band. Alternatively, the plurality of twelfth frequencies and the twelfth frequency band can differ from the first frequencies and the first frequency band, e.g., to provide resulting signals 236, 238 with a different bandwidth and / or in a different frequency range.

[0111] As explained in relation to FIG. 2A, the further mixer can

[0112] 210 performs the same type of mixing as mixer 110 or a P96572 26 performs a different type of mixing, depending on the desired properties of the resulting signals 236, 238. The frequency of the twelfth signal 236 and the thirteenth signal 238 can thus be defined by combining the second frequency and the twelfth frequency, e.g. by subtracting the twelfth frequencies from the second frequency or by summing the twelfth frequencies and the second frequency.

[0113] FIG. 3 shows various diagrams 300a, 300b, 300c, which illustrate an exemplary mixing of a first signal 302 and a second signal 304 to obtain a resulting third signal 306. For illustration, FIG. 3 shows an exemplary operation of a mixer, e.g., mixer 110, 210.

[0114] The first signal 302 can be an example of the first signal 122, and the second signal 304 can be an example of the second signal 124 or its phase-shifted versions 126 and 128. The aspects discussed with respect to signals 302, 304, and 306 of FIG. 3 can therefore apply to signals 122, 124, 126, 128, 132, and 134 of FIG. 1 (and corresponding signals in FIG. 2), and vice versa. The resulting third signal 306 can be an example of the mixer output signals, e.g., the fifth signal 132 and the sixth signal 134. The example in FIG. 3 shows a downward mix, which may be the preferred configuration for the circuit topology.

[0115] As shown in FIG. 3, the first signal 302 can be a broadband signal having a plurality of first frequencies in a frequency band B, ranging from a first lower frequency f u up to a first upper frequency f oextends, and that a first center frequency f m exhibits. The second signal 304 can be a narrowband signal; for example, the second signal 302 can have a single second frequency f2 or, in general, a very narrow bandwidth compared to the first signal 302. P96572 27

[0116] In a downmix, the resulting third signal 306 can retain the bandwidth B of the first signal 302, which is shifted to a lower frequency range. The frequency band of the third signal 306 can thus be derived from a third lower frequency (f2-f1). o ) , which is determined by the difference between the second frequency f2 and the first upper frequency f o is given, up to a third upper frequency (f2-f u ) extend, which are defined by the difference between the second frequency f2 and the first lower frequency f u is given. Accordingly, the center frequency (f2— f) can be m) of the third signal 306 by the difference between the second frequency f2 and the first center frequency f m result.

[0117] In this scenario, the second frequency f2 can be equal to or greater than the highest frequency of the first signal 302, i.e., the second frequency f2 can be equal to or greater than the first upper frequency f. o be.

[0118] FIG. 4A and FIG. 4B show exemplary diagrams 400a, 400b, illustrating an example of a broadband signal 402, 404 according to various aspects. The broadband signals 402, 404 can be examples of the first signal 122 provided by the first signal generator 102. The aspects described with respect to the broadband signals 402, 404 can apply to the first signal 122 (and corresponding signals in FIG. 2A and FIG. 2B) and vice versa.

[0119] As mentioned, the first signal generator 102 can be configured in any suitable way to generate the broadband signal. In a preferred configuration, the first signal generator 102 can be configured to perform a frequency sweep (in other words, a frequency scan) to generate the first signal 122.

[0120] Referring to FIG. 4A and 4B, the first signal generator 102 can be configured to perform a frequency sweep from the first lower frequency f u to the first upper frequency f o executes, e.g. by generating a P96572 28 time-variable signal whose frequency varies over time t from the first lower frequency f u to the first upper frequency f o increases. The difference between the first upper frequency f o and the first lower frequency f u defines the bandwidth, B, of the signal 402, 404.

[0121] In some aspects, as shown in FIG. 4A, the frequency sweep can exhibit a continuous frequency ramp. Visually, the frequency of signal 402 can increase continuously over the period in which the signal is generated. Signal 402 can thus be a continuous-time signal containing a multitude of frequencies, which define the bandwidth from the first lower frequency f. u up to the first upper frequency f o cover in a continuous manner.

[0122] In some aspects, as shown in FIG. 4B, the frequency sweep can exhibit a multitude of frequency jumps. Visually, the frequency of signal 404 can increase stepwise over the period in which the signal is generated. Signal 404 can thus be a discrete signal containing a multitude of frequencies, which define the bandwidth from the first lower frequency f. u up to the first upper frequency f ocovering a wide range of discrete frequency values.

[0123] As explained with reference to FIG. 1, the signal generators 102, 104 and the splitter 106 can have any suitable configuration for generating the signals and imposing the desired phase shift. In a preferred configuration, the splitter 106 can be configured as a quadrature coupler and the signal generators 102, 104 can be configured as a phase-locked loop. In this context, FIG. 5A shows an exemplary quadrature coupler 500, which can be an exemplary implementation of the splitter 106. FIG. 5B shows an exemplary phase-locked loop 550, which can be an exemplary implementation of the signal generators 102, 104, 202, 204. P96572 29

[0124] The operating principles of quadrature couplers and phase-locked loops are generally known. A brief description is given to discuss aspects that may be relevant to the present disclosure. It is understood that the representation in FIGS. 5A and 5B is exemplary and that a quadrature coupler and a PLL may have additional or alternative components.

[0125] As shown in FIG. 5A, a quadrature coupler 500 can generally be configured to receive an input signal 124 and split it into two output signals 126, 128, which are phase-shifted by 90 degrees. The output signals 126, 128 can thus have the same amplitude and a phase difference of 90° to each other. The quadrature coupler 500 can have any suitable configuration. For example, the quadrature coupler 500 can be a hybrid coupler, a branch-line coupler, a superheterodyne coupler, or a coupling-line coupler.

[0126] The quadrature coupler 500 can have multiple terminals, e.g., an input terminal 502 where the coupler 500 receives the input signal 124, a first output terminal 506 (also called a pass-through terminal) where the coupler 500 provides the in-phase component 126 of the quadrature signal, and a second output terminal 508 (also called a coupled terminal) where the coupler 500 provides the quadrature component 128 of the quadrature signal. The coupler 500 can further have an isolated terminal 504, which ensures separation between the input signal 124 and a reflected signal. In some configurations, the isolated port 504 may be located inside the coupler 500 and not accessible from the outside.

[0127] In short, the input signal 124 can enter through the input terminal 502 and is split at the output terminals 506 and 508 into two signals of equal power (e.g., half the input power). The signal 128 at the second output terminal 508 is phase-shifted by 90° relative to the first output signal 126 at output terminal 506. The terminals 502, 504, 506, and 508 of the coupler 500 can be connected to each other via transmission lines, e.g., four transmission lines in a square configuration, which allows for power division and phase shifting.

[0128] As shown in FIG. 5B, a phase-locked loop 550 can contain three main components: a phase detector 552, a loop filter 554, and a voltage-controlled oscillator 556, coupled in a feedback configuration. The phase detector 552 can compare the phase of an input signal 562 (a reference signal) with the phase of the output signal 564 and generate an error signal proportional to the phase difference. The loop filter 554 can, for example, be a low-pass filter to smooth the error signal output by the phase detector 552. The voltage-controlled oscillator 556 can be controlled by the error signal from the loop filter 554 and provide the output signal 564.

[0129] The phase of the output signal 564 is thus synchronized with the phase of the input signal 562 via the feedback loop. The signal from the phase detector 552 causes an adjustment of the frequency of the oscillator 556 to minimize the phase difference until a match is achieved. The PLL can therefore enable very precise control of the output signal 564, which can be particularly relevant for combined operation with a quadrature coupler. For example, the frequency of the output signal 564 can be precisely controlled to match the frequency at which the quadrature coupler provides the 90° phase shift. In this scenario, the phase-locked loop 550 can further include a controllable element (not shown) in the feedback loop, which is configured such that the frequency of the output signal 564 can be adjusted with a finer resolution than the reference frequency. For example, the P96572 31

[0130] Phase control loop 550 has a controllable fractional frequency divider (as a controllable element) in the feedback.

[0131] The output signal 564 can thus be an example of the first signal 122 or the second signal 124 (and of the further signals in FIG. 2), whose frequency can be defined by controlling the frequency of the oscillator 556.

[0132] As already mentioned, the broadband signals generated according to the strategy described herein can then be used for any suitable application. The most relevant application is their use for signal transmission and signal reception. In this context, FIG. 6A shows a communication arrangement 600, which includes a signal generation circuit configured as described herein, e.g., circuit 100, and a transmitter circuit 602 coupled to circuit 100. It is understood that the signal generation circuit can have any of the configurations described herein.

[0133] The transmitter circuit 602 can thus receive the signals 132 and 134 output by the circuit 100 and can be configured to perform signal transmission using these signals 132 and 134. In particular, in such a configuration, the signals 132 and 134 can define a quadrature signal, and the circuit 100 can be configured such that the signals 132 and 134 are in a low frequency range.

[0134] The transmitter circuit 602 can have one or more antennas 604, 606 or be coupled to one or more antennas 604, 606 and can be configured to supply the signals 132, 134 output by the circuit 100 to the antennas 604, 606 for the transmission of corresponding electromagnetic waves. P96572 32

[0135] For example, the transmitter circuit 602 can have a plurality of antennas 604, 606. In a preferred configuration, the transmitter circuit 602 can have a first antenna 604 and a second antenna 606 (e.g., only the two antennas 604, 606) that are linearly polarized. For example, the first antenna can have a first linear polarization with a first phase, and the second antenna can have a second linear polarization with a second phase. The first phase and the second phase can have the same phase offset from each other as the signals 132, 134 output by the circuit 100 (e.g., 90°).

[0136] In some aspects, the first antenna 604 and the second antenna 606 can be set up in a cross configuration.

[0137] A cross-configuration for antennas 604 and 606 offers advantageous properties for signal transmission, e.g., in terms of data throughput, signal diversity, reduction of crosstalk, improved detection in radar applications, etc. The signals generated according to the topology described here can enable efficient utilization of such an antenna configuration.

[0138] In some aspects, in addition to or as an alternative to signal transmission, the signals 132, 134 output by the circuit 100 can be used for signal reception. The communication arrangement 600 can therefore, in addition to or as an alternative to the transmitter circuit 602, include a receiver circuit 612, which is coupled to the circuit 100 and configured to receive the output signals 132, 134 and use them for signal reception.

[0139] The receiver circuit 612 can be configured to receive signals using the signals 132 and 134 (e.g., the fifth signal 132 and the sixth signal 134) output by the circuit 100. (See P96572 33)

[0140] For illustration, the receiver circuit 612 can have or be coupled to one or more antennas 614, 616 configured for receiving electromagnetic waves, and can be configured to process the received signals from the antennas 614, 616 using the signals 132, 134 output by the circuit 100. For example, the receiver circuit 612 can have a plurality of antennas 614, 616, e.g., a first antenna 614 and a second antenna 616 (e.g., linearly polarized) in a cross configuration.

[0141] In particular, the receiver circuit 612 can be configured to perform a frequency downconversion of a received signal using the signals 132, 134 output by the circuit 100. The signals 132, 134 can thus reduce the frequency of the signals received at the antennas 614, 616 to a baseband frequency range for further processing.

[0142] FIG. 6B shows a communication arrangement 650 in a schematic representation. The communication arrangement 650 can be an exemplary implementation of the communication arrangement 600, e.g. with an exemplary implementation of the circuit 100, the transmitter circuit 602 and the receiver circuit 604.

[0143] The communication arrangement 650 can thus include a signal generation circuit 651, which has a first phase-locked loop 652 configured to generate a broadband signal, and a second phase-locked loop 654 configured to generate a narrowband signal. For example, the first phase-locked loop 652 can be a sweep PLL. For example, the second phase-locked loop 654 can be a continuous-wave local oscillator.

[0144] The signal generation circuit 651 can further include a quadrature coupler 656 to generate a quadrature signal based on the narrowband signal from the second P96572 34

[0145] Phase-locked loop 654 is provided. The quadrature signal can be supplied to a mixer arrangement comprising a first mixer 662 for down-mixing the in-phase component with the broadband signal and a second mixer 664 for down-mixing the quadrature component with the broadband signal. The output signal of the circuit 651 can thus be a broadband quadrature signal in a low frequency range.

[0146] The communication arrangement 650 can further comprise a transmitter circuit 670, which receives the broadband quadrature signal from the circuit 651. The transmitter circuit 670 can comprise a filter stage for filtering the quadrature signal, e.g., a low-pass filter stage 672, 674 for filtering the in-phase component and the quadrature component. Optionally, the transmitter circuit 670 can comprise a modulator 676 to impose any desired modulation (e.g., amplitude modulation) on the signal before transmission. The transmitter circuit 670 can further comprise transmission components 678 (e.g., one or more antennas, one or more amplifiers, etc.) for generating and transmitting electromagnetic waves from the quadrature signal.

[0147] On the receiver side, the communication arrangement 650 can further comprise a receiver circuit 680, which receives electromagnetic waves by means of receiving components 686 (e.g., one or more antennas, one or more amplifiers, etc.). The receiver circuit 680 can further receive the quadrature signal from the circuit 651 (e.g., after filtering by the filter stage on the transmitter side) and use this signal to down-convert the frequency of the signals received at the antennas. For example, the receiver circuit 680 can have a first mixer 684 and a second mixer 686 for down-mixing the received signal with the quadrature signal, thereby shifting the frequency of the signal received at the antennas to a lower frequency range, e.g., the baseband range. P96572 35

[0148] Mixers 684 and 686 can supply their output signal to a processing circuit 690 for further processing. The processing circuit 690 can be, or include, any suitable front-end circuit for signal processing. For example, the processing circuit 690 can include an analog-to-digital converter for converting the signal into a digital signal and enabling digital processing.

[0149] As already mentioned, ground-penetrating radar (GPR) applications are the most relevant use case for the circuit topology described here. In this context, FIG. 7 shows a GPR device 700 that uses the broadband signal to perform a GPR measurement.

[0150] The ground-penetrating radar device 700 can thus include a signal generation circuit 720, which can be configured as circuit 100 of FIG. 1 (or as circuits 200a, 200b, 651 of FIG. 2A, FIG. 2B, FIG. 6B). In particular, the signal output by circuit 720 can be a quadrature signal in a low-frequency range during ground-penetrating radar measurements. The mixer of circuit 720 can thus perform a subtractive combination of the broadband signal (from the first signal generator) with the narrowband quadrature signal (from the second signal generator) to obtain suitable characteristics for the resulting quadrature signal output by circuit 720.

[0151] The ground-penetrating radar device 700 may further comprise a transmitter circuit 730, which is configured to receive the signal output by the circuit 720 and to perform signal transmission using this signal. The ground-penetrating radar device 700 may further comprise a receiver circuit 740, which is configured to receive the signal output by the circuit 720 and to perform signal reception using this signal. The transmitter circuit 730 may be configured like the transmitter circuits 602 and 670, and the P96572 36

[0152] Receiver circuit 740 can be set up like receiver circuits 612 and 680.

[0153] In general, the ground radar device 700 can have one or more transmitting antennas 732 and one or more receiving antennas 742. The transmitting antennas 732 can be used for transmitting ground radar signals and the receiving antennas 742 for receiving ground radar signals. A ground radar signal transmitted by a transmitting antenna 732 may be referred to herein as a transmitted signal, and a ground radar signal received by a receiving antenna 742 may be referred to herein as a received signal or reflected signal.

[0154] The general operating principle of ground-penetrating radar (GPR) detection is known in engineering. A brief overview is given here to present the aspects relevant to the present disclosure. In general, GPR detection can be characterized by the emission of electromagnetic waves 734 towards a subsurface and the reception of electromagnetic waves 744, which are reflected back to the GPR device 700. Processing the reflected electromagnetic waves 744 makes it possible to provide an understanding of the subsurface.

[0155] With reference to the configuration of FIG. 7, the ground radar device 700 can be configured to transmit signals 734 (using the transmitting antennas 732 and the signal output by the circuit 720) and to receive reflected signals 744 (using the receiving antennas 742). A reflected signal 744 can be understood as a transmitted signal 734 reflected from a target 760 back to the ground radar device 700.

[0156] Within the scope of this disclosure, the term "target" can be used to describe any type of entity that can be detected by ground-penetrating radar. For example, a "target" could be a P96572 37

[0157] The object can be located underground. As another example, a "target" can be an interface between regions with different electromagnetic properties. The processing of the reflected signals 744 received by the ground-penetrating radar device 700 enables the determination of various properties of the target 706, such as its position, size, orientation, etc.

[0158] The processing circuit 710 can be configured to control the operation of the ground-penetrating radar device 700, e.g., to control the operation of the transmitting circuit 730 and the receiving circuit 740. In particular, the processing circuit 710 can be configured to receive a measurement signal from the receiving circuit 740 and to process the measurement signal to determine the characteristics of the target 706 (e.g., distance, size, etc.). A measurement signal can correspond to a reflected signal 744 after processing in the receiving circuit 740. For example, a measurement signal can be a reflected signal 744 that has been converted into a digital signal. In various aspects, the processing circuit 710 can be a digital front end of the ground-penetrating radar device 700. Intuitively, the processing circuit 710 can be configured to perform digital signal processing.

[0159] The characteristics of the 734 transmitted signals can be selected according to the desired ground-penetrating radar (GPR) detection strategy. For example, the 734 transmitted signals can be frequency-modulated continuous wave (FMCW) signals. This configuration has been shown to enable a simple and efficient implementation of GPR detection.

[0160] FIG. 8 shows a schematic flowchart of a method 800 for generating a signal from various perspectives. It is understood that the aspects described with respect to method 800 also apply to circuits 100, 200a, 200b, 651, and 720, and vice versa. P96572 38

[0161] Method 800 may include, in 810, generating a first signal, wherein the first signal has a plurality of first frequencies lying in a first frequency band. Intuitively, Method 800 may include generating a first broadband signal. For example, Method 800 may include performing a frequency sweep to generate the first signal (e.g., a frequency sweep with a continuous ramp or with frequency jumps). For example, Method 800 may include using a first PLL to generate the first signal.

[0162] Method 800 may further include in 820 the generation of a second signal with a second frequency. For example, the second signal may have a single frequency or, more generally, a much smaller bandwidth compared to the first signal. For example, Method 800 may include the use of a second PLL to generate the second signal.

[0163] Method 800 may further include in 830 the generation of a third and a fourth signal based on the second signal. The third and fourth signals may be phase-shifted relative to each other, for example by 90°. The third and fourth signals may have the same frequency as the second signal. For example, Method 800 may include the use of a quadrature coupler to generate the third and fourth signals. For illustration, Method 800 may, in some aspects, include the generation of a narrowband quadrature signal.

[0164] Method 800 can further include, in 840, mixing the first signal and the third signal together to generate a fifth signal, and mixing the first signal and the fourth signal together to generate a sixth signal. The fifth signal can have the third phase and a plurality of fifth frequencies in a frequency band with the same bandwidth as the first signal. The sixth signal can have the fourth phase and the plurality of fifth frequencies. In other words, the method can include mixing a narrowband quadrature signal with the (first) broadband signal to generate a broadband quadrature signal which has the same frequency bandwidth as the first broadband signal.

[0165] For example, Method 800 may include downmixing the third signal with the first signal and the fourth signal with the first signal, thereby shifting the (wide) frequency band to a lower frequency range. Optionally, Method 800 may further include using the generated signal(s) for signal transmission and / or signal reception, e.g., for conducting ground-penetrating radar measurements.

[0166] The foregoing description is given only as an example, and the person skilled in the art will understand that modifications can be made without deviating from the broader scope of the invention as set out in the claims. The description and drawings are therefore to be understood in an illustrative rather than a restrictive sense.

[0167] Example 1 is a circuit. The circuit comprises a first signal generator configured to generate a first signal, wherein the first signal has a plurality of first frequencies, the plurality of first frequencies being in a first frequency band extending from a lower first frequency to an upper first frequency; a second signal generator configured to generate a second signal, wherein the second signal has a second frequency; a splitter configured to receive the second signal and to generate a third signal and a fourth signal based on the second signal, wherein the third signal has the second frequency and a third phase, and wherein the fourth signal has the second frequency and a fourth phase, the third phase and the fourth phase being phase-off from each other.and a mixer set up for: mixing the first signal and the third signal together to generate a fifth signal; and mixing the first signal and the fourth signal together to generate a sixth signal, wherein the fifth signal has the third phase and a plurality of fifth frequencies, wherein the plurality of fifth frequencies lies in a fifth frequency band extending from a lower fifth frequency to an upper fifth frequency, wherein the sixth signal has the fourth phase and the plurality of fifth frequencies, and wherein the fifth frequency band has the same frequency bandwidth as the first frequency band.

[0168] In Example 2, the circuit according to Example 1 can optionally further feature that the second frequency is equal to or greater than the upper first frequency.

[0169] In Example 3, the circuit according to Example 1 or 2 may optionally further include the mixer being configured such that the lower fifth frequency results from a difference between the second frequency and the upper first frequency, and that the upper fifth frequency results from a difference between the second frequency and the lower first frequency.

[0170] In Example 4, the circuit according to any one of Examples 1 to 3 may optionally further have that the third phase is 0° and that the fourth phase is 90°.

[0171] In Example 5, the circuit according to any one of Examples 1 to 4 may optionally further include the first signal generator being configured to perform a frequency sweep from the lower first frequency to the upper first frequency in order to generate the first signal. P96572 41

[0172] In Example 6, the circuit according to Example 5 can optionally further include the first signal generator being configured such that the frequency sweep has a continuous frequency ramp, or wherein the first signal generator is configured such that the frequency sweep has a plurality of frequency jumps.

[0173] Example 7 is a communication arrangement. The communication arrangement comprises the circuit according to any one of Examples 1 to 6; and a transmitter arrangement coupled to the circuit and configured to perform a signal transmission using the fifth signal and the sixth signal.

[0174] In Example 8, the communication arrangement can be set up according to Example 1.

[0175] 7 optionally further comprising that the transmitter arrangement has one or more antennas or is coupled to one or more antennas, and wherein the transmitter arrangement is configured to supply the fifth signal and the sixth signal to the one or more antennas in order to carry out signal transmission by means of the one or more antennas.

[0176] In Example 9, the communication arrangement can be set up according to Example 1.

[0177] 8 optionally further feature that the one or more antennas have a first antenna with a first linear polarization with a first phase and a second antenna with a second linear polarization with a second phase, and wherein the first phase and the second phase have the same phase offset to each other as the third phase and the fourth phase.

[0178] In this embodiment, the first antenna and the second antenna can be arranged to generate linearly polarized waves, wherein the waves generated by the first antenna have a first fixed direction of the electric field vector and the waves generated by the second antenna have a second fixed direction of the electric field vector, wherein the first fixed direction and the second fixed direction are at right angles to each other.

[0179] In this configuration, two antennas, each with linear polarization, can be used to construct a device that emits circularly polarized waves through targeted control. Visually, the first antenna can have horizontal polarization and the second antenna vertical polarization. The two linearly polarized antennas can be arranged such that their field vectors (in other words, polarization planes) are geometrically at right angles (visually, 90°) to each other. These two antennas can then be driven with a 90° phase shift of the electrical signal. Linearly polarized antennas can be built with very wide bandwidths, thus enabling wideband circularly polarized radiation. In contrast, antenna geometries that inherently emit circularly polarized waves are generally very limited in their frequency bandwidth.

[0180] In Example 10, the communication arrangement according to Example 9 can optionally further include the first antenna and the second antenna being set up (visually arranged) in a cross configuration.

[0181] In this configuration, the first and second antennas can be arranged at a geometric angle of 90° to each other, i.e., in a cross configuration. This means that the polarization planes of the waves radiated by the antennas are also at a geometric angle of 90° to each other, allowing for the generation of broadband circularly polarized radiation.

[0182] In Example 11, the communication arrangement according to one of Examples 7 to 10 may optionally further include: a receiver arrangement coupled with the circuit and P96572 43 configured to perform signal reception using the fifth signal and the sixth signal.

[0183] Example 12 is a ground-penetrating radar device comprising: the communication arrangement according to any one of Examples 7 to 11; and a processing circuit configured to control the communication arrangement for performing a ground-penetrating radar measurement by transmitting ground-penetrating radar signals using the fifth signal and the sixth signal.

[0184] Example 13 is a circuit. The circuit comprises a first signal generator configured to generate a first broadband signal; a second signal generator configured to generate a second narrowband quadrature signal, wherein the second narrowband quadrature signal has a smaller frequency bandwidth than the first broadband signal; a mixer configured to downmix the first broadband signal with the second narrowband quadrature signal to generate a third broadband quadrature signal, wherein the third broadband quadrature signal has the same frequency bandwidth as the first broadband signal.

[0185] In Example 14, the circuit according to Example 13 may optionally further include the first signal generator being set up to perform a frequency sweep in order to generate the first broadband signal.

[0186] In Example 15, the circuit according to Example 14 may optionally further include the first signal generator being configured such that the frequency sweep has a continuous frequency ramp, or wherein the first signal generator is configured such that the frequency sweep has a plurality of frequency jumps.

[0187] In Example 16, a circuit according to one of Examples 13 to 15 can further exhibit that the first broadband signal has a bandwidth of one octave. P96572 44

[0188] Example 17 is a method for signal generation. The method comprises: generating a first signal, wherein the first signal has a plurality of first frequencies, the plurality of first frequencies lying in a first frequency band extending from a lower first frequency to an upper first frequency; generating a second signal with a second frequency; generating a third signal and a fourth signal based on the second signal, wherein the third signal has the second frequency and a third phase, and the fourth signal has the second frequency and a fourth phase, the third phase and the fourth phase being phase-shifted from each other; and mixing the first signal and the third signal together to generate a fifth signal.and mixing the first signal and the fourth signal together to generate a sixth signal, wherein the fifth signal has the third phase and a plurality of fifth frequencies, wherein the plurality of fifth frequencies lies in a fifth frequency band extending from a lower fifth frequency to an upper fifth frequency, wherein the sixth signal has the fourth phase and the plurality of fifth frequencies, and wherein the fifth frequency band has the same frequency bandwidth as the first frequency band.

[0189] In Example 18, the method according to Example 17 can optionally further include the first signal being generated by performing a frequency sweep.

[0190] In Example 19, the method according to Example 18 may optionally further include that the frequency sweep has a continuous frequency ramp, or that the frequency sweep has a large number of frequency jumps.

[0191] Example 20 is a method for generating a broadband quadrature signal. The method comprises: generating a first broadband signal; generating a second narrowband quadrature signal; wherein the second narrowband quadrature signal has a smaller frequency bandwidth than the first broadband signal; downmixing the first broadband signal with the second narrowband quadrature signal to generate a third broadband quadrature signal, wherein the third narrowband quadrature signal has the same frequency bandwidth as the first broadband signal.

[0192] In Example 21, the method according to Example 20 can optionally further include the fact that the first signal is generated by performing a frequency sweep.

[0193] In Example 22, the method according to Example 21 may optionally further feature that the frequency sweep has a continuous frequency ramp, or that the frequency sweep has a large number of frequency jumps.

Claims

P96572 46 Patent claims 1. Circuit (100) comprising: a first signal generator (102) configured to generate a first signal (122), wherein the first signal (122) has a plurality of first frequencies, the plurality of first frequencies being in a first frequency band extending from a lower first frequency to an upper first frequency; a second signal generator (104) configured to generate a second signal (124), wherein the second signal has a second frequency; a splitter (106) configured to receive the second signal (124) and to generate a third signal (126) and a fourth signal (128) based on the second signal, wherein the third signal (126) has the second frequency and a third phase, and wherein the fourth signal (128) has the second frequency and a fourth phase, the third phase and the fourth phase being phase-shifted from each other; and a mixer (110) configured to: Mixing the first signal (122) and the third signal (126) together to generate a fifth signal (132); and Mixing the first signal (110) and the fourth signal (128) together to generate a sixth signal (134), wherein the fifth signal (132) has the third phase and a plurality of fifth frequencies, the plurality of fifth frequencies being in a fifth frequency band extending from a lower fifth frequency to an upper fifth frequency, wherein the sixth signal (134) has the fourth phase and the plurality of fifth frequencies, and wherein the fifth frequency band has the same frequency bandwidth as the first frequency band. P96572 47 2. Circuit (100) according to claim 1, wherein the second frequency is equal to or greater than the upper first frequency.

3. Circuit (100) according to claim 1 or 2, wherein the mixer (110) is configured such that the lower fifth frequency results from a difference between the second frequency and the upper first frequency, and that the upper fifth frequency results from a difference between the second frequency and the lower first frequency.

4. Circuit (100) according to one of claims 1 to 3, wherein the third phase is 0°, and wherein the fourth phase is 90°.

5. Circuit (100) according to any one of claims 1 to 4, wherein the first signal generator (102) is configured to perform a frequency sweep from the lower first frequency to the upper first frequency in order to generate the first signal (122).

6. Circuit (100) according to claim 5, wherein the first signal generator (102) is configured such that the frequency sweep has a continuous frequency ramp, or wherein the first signal generator (102) is configured such that the frequency sweep has a plurality of frequency jumps.

7. Communication arrangement (600) comprising: the circuit (100) according to any one of claims 1 to 6; and a transmitter arrangement (602) coupled to the circuit (100) and configured to perform a signal transmission using the fifth signal (132) and the sixth signal (134).

8. Communication arrangement (600) according to claim 7, P96572 48 wherein the transmitter arrangement (602) has one or more antennas (604, 606) or is coupled to one or more antennas (604, 606), and wherein the transmitter arrangement (602) is configured to deliver the fifth signal (132) and the sixth signal (134) to the one or more antennas (604, 606) in order to carry out a signal transmission by means of the one or more antennas (604, 606).

9. Communication arrangement (600) according to claim 8, wherein the one or more antennas (604, 606) comprise a first antenna (604) with a first linear polarization with a first phase and a second antenna (606) with a second linear polarization with a second phase, and wherein the first phase and the second phase have the same phase offset to each other as the third phase and the fourth phase.

10. Communication arrangement (600) according to claim 9, The first antenna (604) and the second antenna (606) are set up in a cross configuration.

11. Communication arrangement (600) according to one of claims 7 to 10, further comprising: a receiver arrangement (610) coupled to the circuit (100) and configured to perform signal reception using the fifth signal (132) and the sixth signal (134).

12. Ground radar device (700) comprising: the communication arrangement (600) according to any one of claims 7 to 11; and a processing circuit (710) configured to control the communication arrangement (600) for performing a ground radar measurement by transmitting ground radar signals using the fifth signal (132) and the sixth signal (134). P96572 49 13. Circuit (100) comprising: a first signal generator (102) configured to generate a first broadband signal (122); a second signal generator (104, 106) configured to generate a second narrowband quadrature signal (126, 128); wherein the second narrowband quadrature signal (126, 128) has a smaller frequency bandwidth than the first broadband signal (122); a mixer (110) configured to downmix the second narrowband quadrature signal (126, 128) with the first broadband signal (122) to generate a third broadband quadrature signal (132, 134), wherein the third broadband quadrature signal (132, 134) has the same frequency bandwidth as the first broadband signal (122).

14. Circuit (100) according to claim 13, wherein the first broadband signal (122) has a bandwidth of one octave.

15. Method (800) for signal generation, comprising the method (800): Generating (810) a first signal, wherein the first signal has a plurality of first frequencies, the plurality of first frequencies being in a first frequency band extending from a lower first frequency to an upper first frequency; Generating (820) a second signal with a second frequency, Generating (830) a third signal and a fourth signal based on the second signal, wherein the third signal has the second frequency and a third phase, wherein the fourth signal has the second frequency and a fourth phase, wherein the third phase and the fourth phase have a exhibit phase shifts relative to each other; and P96572 50 Mixing (840) the first signal and the third signal together to generate a fifth signal; and Mixing (840) the first signal and the fourth signal together to generate a sixth signal, wherein the fifth signal has the third phase and a plurality of fifth frequencies, wherein the plurality of fifth frequencies are in a fifth frequency band extending from a lower fifth frequency to an upper fifth frequency, wherein the sixth signal has the fourth phase and the plurality of fifth frequencies, and wherein the fifth frequency band has the same frequency bandwidth as the first frequency band.

16. Method (800) for generating a broadband quadrature signal, comprising the method (800): generating a first broadband signal; generating a second narrowband quadrature signal; wherein the second narrowband quadrature signal has a smaller frequency bandwidth than the first broadband signal; Downmixing the second narrowband quadrature signal with the first broadband signal to generate a third broadband quadrature signal, where the third narrowband quadrature signal has the same frequency bandwidth as the first broadband signal.

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