Method for sampling ultra-wideband signals

Abstract

A method for sampling an ultra-wideband signal, the method comprising the steps of pre-arranging a GPR antenna comprising at least one transmitter and one receiver, a variable gain amplifier or VGA, an A / D converter and a control unit. Then, the method comprises the steps of transmitting and receiving a primary ultra-wideband signal by the GPR antenna, and sampling a value of the primary ultra-wideband signal by the A / D converter with respect to a first full-scale portion. The method further comprises the steps of transmitting and receiving at least one secondary ultra-wideband signal by the GPR antenna, amplifying the secondary ultra-wideband signal by the variable gain amplifier, and sampling a value of the secondary ultra-wideband signal by the A / D converter with respect to a full-scale portion different from the first portion.

Description

Technical Field

[0001] This invention relates to the field of surveying using GPR (Ground Penetrating Radar) technology.

[0002] Specifically, the present invention relates to a method for sampling ultra-wideband signals. Background Technology

[0003] As is well known, signals transmitted and received by GPR (Ground Penetrating Radar) sensors are of the ultra-wideband (UWB) type, meaning they are characterized by a -10 dB frequency band of at least 500 Hz, or -10 dB equal to at least 20% of the center frequency of that band. The -10 dB frequency band is the difference between the highest frequency (for which the power spectral density is 10 dB lower than the maximum value) and the lowest frequency.

[0004] The main limitation of existing techniques for sampling UWB signals in the time domain is given by the sampling rate of the analog-to-digital converter (ADC). In fact, to receive the signal correctly, the converter must have a sampling rate at least twice the maximum frequency of the signal (Nyquist sampling theorem). Therefore, very high-speed A / D converters must be used for UWB signals, i.e., sampling frequencies that can be several GHz and analog bandwidths sufficient to satisfy the Nyquist condition.

[0005] refer to Figure 2 Below are some existing solutions in the prior art.

[0006] The first solution in the prior art provides signal acquisition by means of so-called "equivalent time sampling" or "stroboscopic sampling." This first solution involves sending multiple consecutive pulses, and for each of these pulses, collecting only one sample at a time. An example of this method is shown in US2010195699.

[0007] The typical characteristics of this acquisition method are high sensitivity or dynamic range. DR (That is, the ratio between the maximum and minimum signal that the system can receive).

[0008] Specifically, the dynamic range can be limited as follows:

[0009]

[0010] in,

[0011] - It is a factor that indicates sampling efficiency (usually approximately equal to 1).

[0012] - This gain is due to the possible application of "superposition" technology, which involves averaging continuously acquired signals in order to reduce the noise power of the received signal.

[0013] It is the dynamic range represented solely by the A / D converter, that is, by... The dynamic range represented by the number (“significant digits”).

[0014] The greater dynamic range results in a greater ability for the GPR to detect very weak signals. Because the returned signal is strongly attenuated, the receiver's high sensitivity essentially indicates the GPR's ability to locate objects at greater depths.

[0015] However, the drawback of stroboscopic sampling is that it requires a large number of continuous transmissions to correctly acquire and reconstruct the signal.

[0016] Specifically, the number of samples that must be obtained As defined by the Nyquist condition:

[0017]

[0018] in,

[0019] - This is the maximum instrument full scale or width of the receiving window. If the received window exceeds this maximum instrument full scale or width, GPR will ignore any returned signals.

[0020] - It is the maximum frequency of the UWB signal reaching the receiver.

[0021] Since stroboscopic sampling in the existing technology involves acquiring only one sample at a time, the total time required to sample the received signal is given by the following formula:

[0022]

[0023] in,

[0024] - It is the "pulse repetition interval," that is, the time between sending and successive sending;

[0025] - It is the "pulse repetition frequency", that is, the repetition frequency of the transmission.

[0026] Therefore, to achieve good sensitivity, the above sampling method involves a very long signal acquisition and reconstruction time, that is, at least equal to the pulse transmission time. N S times.

[0027] An alternative method existing in the art is so-called "real-time sampling," which allows for acquisition much faster than the equivalent time because it uses an A / D converter with sufficiently high speed to correctly sample the UWB signal in a single transmit-receive cycle of the radar pulse, thus ensuring compliance with the Nyquist condition, such as at the maximum frequency of the received signal.

[0028] However, due to technological limitations, as the sampling rate increases, the A / D converter's... ENOB The value (and therefore the dynamic range) is reduced. Therefore, the sensitivity of GPR using this technique is much lower than the sensitivity achievable by sampling within an equivalent time.

[0029] To overcome the above drawbacks, a hybrid solution (“pseudo-strobe” or “pseudo-real-time sampling”) is described in US8884807 and US9057782, which utilizes an A / D converter that is faster than the A / D converter used in equivalent-time sampling, but acquires multiple samples for each received signal.

[0030] However, even this hybrid solution requires a certain number of repetitions of the pulse transmission, making it slower than real-time sampling in any case. Summary of the Invention

[0031] Therefore, the object of the present invention is to provide a method for sampling ultra-wideband signals that allows the signal to be reconstructed in a much shorter time than equivalent time sampling or pseudo-stroboscopic sampling, while ensuring that the dynamic range is not less than that of these methods, so as to guarantee the detection of objects at great depths.

[0032] Another object of the present invention is to provide a method that allows for the possibility of further increasing the dynamic range of a system by means of a "superposition" technique.

[0033] Another object of the present invention is to provide a method that allows for multi-channel GPR acquisition (i.e., through multiple GPR antennas) while maintaining the same efficiency for each individual channel.

[0034] The purposes described herein are achieved through the methods disclosed in this specification. Attached Figure Description

[0035] Further features and / or advantages of the invention will become more apparent from the following description of exemplary embodiments of the invention, with reference to the accompanying drawings, which illustrate, but are not limited to, the following:

[0036] - Figure 1 The flowchart illustrates the subsequent steps of the method for sampling ultra-wideband signals according to the present invention;

[0037] - Figure 2This illustrates the various types of signal sampling existing in the prior art;

[0038] - Figure 3 The steps for sampling values ​​relative to the first full-scale portion are shown;

[0039] - Figure 4 The steps for sampling values ​​relative to the second full-scale portion are shown;

[0040] - Figure 5A and Figure 5B The operating principle of a first embodiment of a method for sampling ultra-wideband signals is schematically illustrated, in which a transmitter and a receiver are used;

[0041] - Figure 6A and Figure 6B The operating principle of a second embodiment of a method for sampling ultra-wideband signals is schematically illustrated, wherein two transmitters and two receivers are used to transmit / receive two primary ultra-wideband signals and two secondary ultra-wideband signals;

[0042] - Figure 7A and Figure 7B The operating principle of a third embodiment of a method for sampling ultra-wideband signals is schematically illustrated, in which two transmitters and three receivers are used. Detailed Implementation

[0043] refer to Figure 1 A method for sampling ultra-wideband signals includes a first step of pre-arranging an apparatus comprising a GPR antenna, a variable gain amplifier or VGA, an A / D converter and a control unit

[301] .

[0044] Also refer to Figure 3 , Figure 5A and Figure 5B The following steps are then performed: transmitting and receiving the main ultrawideband signal via a GPR antenna

[302] ; and sampling the value of the main ultrawideband signal relative to a first full-scale portion via an A / D converter

[303] . In such a step, the VGA is thus deactivated, as... Figure 3 and Figure 5A As illustrated in the diagram.

[0045] Also refer to Figure 4 Then, the VGA is activated, and the method provides the following steps: transmitting and receiving at least one secondary ultrawideband signal via a GPR antenna

[304] , amplifying the secondary ultrawideband signal via a VGA

[305] , and sampling the value of the secondary ultrawideband signal relative to a second full-scale portion different from the first portion via an A / D converter

[306] .

[0046] Based on the dynamic range and sampling requirements of the signal, steps

[304] ,

[305] and

[306] can be repeated again using more than one secondary ultrawideband signal to divide the full scale of the signal into corresponding parts.

[0047] Then, according to the method of the invention, the full scale of the signal is divided into two or more parts so that the first part is sampled without amplification, and then amplification and sampling of subsequent parts are continued.

[0048] This allows for sampling of UWB signals in a very short time compared to existing methods, while maintaining a high dynamic range. In particular, the time required by the above method is proportional to the number of times the signal is transmitted / received, and therefore proportional to the number of parts into which the full scale of the signal is divided.

[0049] Furthermore, the method according to the invention provides the steps of repeatedly transmitting and receiving the primary ultrawideband signal and each secondary ultrawideband signal, as well as the possibility of subsequently averaging the signals, thereby enabling the "superposition" technique to further increase the dynamic range.

[0050] Specifically, at least two sampling steps of the value of the primary ultrawideband signal and at least two sampling steps of the value of each secondary ultrawideband signal can be provided to achieve a "pseudo-strobe" mode.

[0051] Furthermore, the method according to the invention can provide a pre-arranged layout including One transmitter and The receiver has a GPR antenna to allow the transmitter / receiver to transmit / receive signals in superposition.

[0052] In particular, Figure 6A and Figure 6B In an exemplary embodiment, the method provides a pre-arranged GPR antenna comprising two transmitters and two receivers for transmitting / receiving and sampling two primary UWB signals and two secondary UWB signals, which are then superimposed to achieve a superposition technique.

[0053] Specifically, in time There are steps involving transmitting and receiving the main UWB signal from the first transmitter / receiver, followed by sampling the value of the main UWB signal, and in time... There is a step where a second transmitter / receiver transmits and receives an auxiliary primary UWB signal, and then samples the value of the auxiliary primary UWB signal.

[0054] In time There are steps involving a first transmitter / receiver transmitting and receiving a secondary ultra-wideband signal, followed by amplification and sampling of the value, and in time... There is a step where a second transmitter / receiver transmits and receives auxiliary secondary ultra-wideband signals, and then amplifies and samples the values.

[0055] In this way, the sampling steps of the primary and secondary UWB signals can be repeated, thus obtaining multiple overlapping signals for more accurate sampling, thereby utilizing the PRI delay between the transmission / reception of the two signals performed by the transmitter / receiver pair. Typically, in practice, the time between one pulse and the next pulse (PRI) is several orders of magnitude larger than the maximum delay (full scale) that radar can detect. Therefore, multiple channels can be used for transmission and reception, thus separating them in time.

[0056] refer to Figure 7A and Figure 7B Another possibility is that it has more transmitters than the number of transmitters ( It has a larger number of receivers and can simultaneously acquire signals generated by a single transmitter using multiple receiving elements.

[0057] This can be achieved by using a common time base for each transmitter or receiver element that makes up the system, and by setting separate programmable delays for receiving the same signal between two or more different receivers.

Claims

1. A method for sampling ultra-wideband signals, the method comprising the following steps: - Pre-arrangement: - A GPR antenna, which includes at least one transmitter and one receiver; - Variable gain amplifier VGA; - A / D converter; - Control unit; - Transmit and receive main ultrawideband signals via the GPR antenna; - The value of the main ultrawideband signal is sampled by the A / D converter relative to the first full-scale portion; The method is characterized in that it further includes the following steps: - To transmit and receive at least one secondary ultra-wideband signal via the GPR antenna; - The secondary ultra-wideband signal is amplified by the variable gain amplifier; - The value of the secondary ultrawideband signal is sampled by the A / D converter relative to a full-scale portion that is different from the first full-scale portion.

2. The method for sampling an ultra-wideband signal of claim 1, wherein, The method provides an iteration of the steps of transmitting and receiving a primary ultra-wideband signal and at least one secondary ultra-wideband signal, and further provides a step of superimposing and modulating the received primary ultra-wideband signal and the received secondary ultra-wideband signal to reduce noise.

3. The method for sampling an ultra-wideband signal of claim 1, wherein, The method provides at least two steps for sampling the value of the primary ultrawideband signal and at least two steps for sampling the value of the secondary ultrawideband signal.

4. The method for sampling ultra-wideband signals according to claim 1, wherein, The GPR antenna comprises n transmitters and m receivers, wherein , .

5. The method for sampling an ultra-wideband signal of claim 4, wherein, Provide the following steps: - in time , transmitting and receiving the primary ultra-wideband signal by the first transmitter / receiver pair; - The value of the main ultrawideband signal is sampled by the A / D converter relative to the first full-scale portion; - in time , by at least one second transmitter / receiver pair, an auxiliary primary ultra-wideband signal is transmitted and received, wherein PRI denotes the "pulse repetition interval", i.e. the time between a transmission and a successive transmission, and PRF denotes the "pulse repetition frequency", i.e. the repetition frequency of the transmissions; - The value of the auxiliary main ultrawideband signal is sampled by the A / D converter relative to the first full-scale portion; - at a time by said first transmitter / receiver pair, at least one secondary ultra-wideband signal is transmitted and received; - The secondary ultra-wideband signal is amplified by the variable gain amplifier; - The value of the secondary ultrawideband signal is sampled from the A / D converter relative to a full-scale portion that is different from the first full-scale portion; - in time The second transmitter / receiver pair is used to transmit and receive at least one auxiliary secondary ultra-wideband signal; - The auxiliary secondary ultra-wideband signal is amplified by the variable gain amplifier; - The value of the auxiliary secondary ultra-wideband signal is sampled from the A / D converter relative to a full-scale portion that is different from the first full-scale portion.

Images