CN208488545U - A kind of difference frequency signal generation device and system - Google Patents
A kind of difference frequency signal generation device and system Download PDFInfo
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Abstract
The utility model embodiment provides a kind of difference frequency signal generation device and system.Device includes terahertz transmitter, the first local vibration source, the first mixing detector, the first power amplifier and signal processing link；Terahertz transmitter emits the first THz wave to measured target；The second THz wave that first mixing detector generates the back wave reflected by measured target and the first local vibration source carries out mixing and obtains the first difference frequency signal；First power amplifier carries out power amplification to the first difference frequency signal；Frequency multiplier in signal processing link receives and amplified first difference frequency signal of frequency multiplication obtains the second difference frequency signal, and the radiofrequency signal that the second mixing detector generates the second difference frequency signal and the second local vibration source carries out mixing and obtains third difference frequency signal and export third difference frequency signal.The third difference frequency signal that the utility model obtains improves temporal resolution and velocity resolution under short period window when carrying out time frequency analysis.
Description
Technical Field
The utility model relates to a signal analysis technical field particularly, relates to a difference frequency signal produces device and system.
Background
Terahertz waves (THz waves) have an oscillation frequency of 1012The terahertz electromagnetic wave and the terahertz wave have the characteristics of good penetrability on nonpolar materials, high carrier frequency, no ionization damage and the like, and have great application potential in the fields of national and public safety, military, high-speed communication, biological research and the like. The terahertz wave technology is developed rapidly in recent years, wherein the terahertz wave is used for Doppler interference speed measurement, the characteristic and the advantage of good penetrability of a nonpolar material are achieved, and the terahertz wave dynamic response speed measurement method has important application value in the field of dynamic response research under material loading.
The Doppler interference velocity measurement technology is realized based on the Doppler effect. The doppler effect is a phenomenon in which an electromagnetic wave (frequency f) is irradiated onto a moving object and the frequency of the electromagnetic wave reflected by the electromagnetic wave changes to some extent. The frequency variation of the electromagnetic wave is called doppler shift (the frequency variation Δ f is proportional to the object speed u, and Δ f ═ 2uf/c where c is the speed of light). In the doppler interference velocity measurement technique, an electromagnetic wave is divided into two beams, one beam is irradiated onto a moving object to be reflected, the reflected electromagnetic wave interferes with the other beam, and the frequency of the two beams of electromagnetic waves is different, so that the recorded time domain interference signal is an oscillation signal with doppler shift as frequency (i.e., s (t) ═ Asin (2 pi Δ ft)). If the motion speed of the object is varied, i.e., u ═ u (t), then the oscillation frequency of the oscillation signal is also varied over time, Δ f ═ Δ f (t). And performing time-frequency analysis on the signal to obtain the change history u (t) of the speed of the moving target along with the time.
Generally, a short-time fourier transform technique is adopted for time-frequency analysis of a doppler interference velocity measurement signal, an interference signal obtained by interference between a reflected electromagnetic wave and another electromagnetic wave is directly and equally divided into a plurality of time segments (width Δ t), fourier spectrum analysis is performed in each time segment to obtain an oscillation frequency (i.e., doppler frequency shift) in the time segment, and thus, the average velocity of a moving target in the time segment is calculated. Under the condition that the motion speed of an object is stable, the time-frequency analysis is directly carried out on the interference signal, so that high-precision speed historical information can be obtained, and under the condition that the speed change is fast, the time-frequency analysis has the defect of insufficient speed resolution. Therefore, the current method for directly performing time-frequency analysis on signals obtained by the doppler interference velocity measurement technology cannot simultaneously achieve the effect of high time resolution and high velocity precision. Fig. 1(a) is a schematic diagram of a velocity curve provided by the prior art, fig. 1(b) is a schematic diagram of a terahertz doppler interference signal provided by the prior art, fig. 1(c) is a schematic diagram of a time-frequency analysis of a doppler signal under a large time window provided by the prior art, and fig. 1(d) is a schematic diagram of a time-frequency analysis of a doppler signal under a small time window provided by the prior art, as shown in fig. 1(a) - (d), it can be seen that, for the same signal, if a large time window is adopted, the velocity accuracy is higher, but the time resolution is weaker; whereas if a shorter time window is used, the time resolution is higher but the speed resolution is lower.
SUMMERY OF THE UTILITY MODEL
In view of the above, an object of the present invention is to provide a differential frequency signal generating apparatus and system, so as to solve the above technical problem that higher time resolution and higher speed resolution cannot be achieved simultaneously.
In a first aspect, an embodiment of the present invention provides a differential frequency signal generating apparatus, including: the terahertz transmitter, the first local vibration source, the first mixing detector, the first power amplifier and the signal processing link are sequentially in communication connection; wherein,
the terahertz transmitter is used for transmitting a first terahertz wave to a target to be detected;
the first local vibration source is used for generating second terahertz waves;
the first frequency mixing detector is used for mixing a reflected wave corresponding to the first terahertz wave reflected by the measured object with the second terahertz wave to obtain a first difference frequency signal;
the first power amplifier is used for performing power amplification on the first difference frequency signal;
the signal processing link comprises a frequency multiplier, a second local vibration source and a second frequency mixing detector; the frequency multiplier is configured to receive and multiply the amplified first difference frequency signal to obtain a second difference frequency signal, the second local oscillator is configured to generate a radio frequency signal, and the second mixing detector is configured to mix the second difference frequency signal and the radio frequency signal to obtain a third difference frequency signal and output the third difference frequency signal.
Further, the device also comprises an oscilloscope connected with the signal processing link;
and the oscilloscope receives the third difference frequency signal sent by the second mixing detector and displays the third difference frequency signal.
Further, the signal processing chain further comprises a first filter and a second filter;
the first filter is connected with the frequency multiplier and is used for filtering the amplified first difference frequency signal sent by the first power amplifier;
and the second filter is connected with the second mixing detector and is used for filtering the third difference frequency signal sent by the second mixing detector.
Further, the signal processing chain also comprises a second power amplifier connected with the second mixing detector;
the second power amplifier is used for amplifying the power of the third difference frequency signal.
Further, the frequency multiplier is a transistor frequency multiplier, a varactor diode frequency multiplier or a step recovery diode frequency multiplier.
Further, the frequency of the first terahertz wave is f0The frequency of the second terahertz wave is f0-FcWherein F isc>NΔf1N is the frequency multiplication frequency of the frequency multiplier, Δ f1For a first Doppler shift, the first difference frequency signal is S1(t)＝A1sin[2π(Fc+Δf)t]，A1And t is the amplitude of the first difference frequency signal and time.
Further, the second difference frequency signal is: s2(t)＝A2sin[2πN(Fc+Δf)t]，A2Is the amplitude of the second difference frequency signal.
Further, the frequency of the radio frequency signal is: fLOWherein, NF isc-FLO>N Δ f; the third difference frequency signal is: s3(t)＝A3sin[2π(NFc-FLO+NΔf)t]，A3Is the amplitude of the third difference frequency signal.
Furthermore, the signal processing links are multiple, and the multiple signal processing links are connected in a cascading manner.
In a second aspect, an embodiment of the present invention provides a differential frequency signal generating system, including a terminal device connected in communication and the differential frequency signal generating apparatus of the first aspect;
the difference frequency signal generating device is used for generating a third difference frequency signal, and the terminal equipment is used for carrying out time-frequency analysis on the third difference frequency signal.
The embodiment of the utility model provides a carry out the doubling to first difference frequency signal through the frequency multiplier, obtain second difference frequency signal for Doppler's frequency shift in the second difference frequency signal has enlarged N times, and second difference frequency signal carries out the mixing through second mixing detector, has reduced the carrier frequency in the second mixing detector, thereby the third difference frequency signal that obtains when carrying out time frequency analysis, under short time window, can improve time resolution and speed resolution.
Additional features and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the embodiments of the invention. The objectives and other advantages of the invention will be realized and attained by the structure particularly pointed out in the written description and claims hereof as well as the appended drawings.
Drawings
In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings that are required to be used in the embodiments will be briefly described below, it should be understood that the following drawings only illustrate some embodiments of the present invention, and therefore should not be considered as limiting the scope, and for those skilled in the art, other related drawings can be obtained according to the drawings without inventive efforts.
FIG. 1(a) is a schematic diagram of a velocity profile provided by the prior art;
FIG. 1(b) is a schematic diagram of a terahertz Doppler interference signal provided by the prior art;
FIG. 1(c) is a schematic diagram of Doppler signal time-frequency analysis under a large time window provided by the prior art;
FIG. 1(d) is a schematic diagram of Doppler signal time-frequency analysis under a small time window provided by the prior art;
fig. 2 is a schematic structural diagram of a differential frequency signal generating apparatus according to an embodiment of the present invention;
fig. 3 is a schematic structural diagram of a difference frequency signal generating device according to another embodiment of the present invention;
fig. 4 is a schematic flow chart of a method for generating a differential frequency signal according to an embodiment of the present invention;
fig. 5(a) is a schematic diagram of doppler shift before frequency doubling according to an embodiment of the present invention;
fig. 5(b) is a schematic diagram of the doppler shift after frequency multiplication according to the embodiment of the present invention;
fig. 6(a) is a schematic speed history diagram of a measured object according to an embodiment of the present invention;
fig. 6(b) is a terahertz interference signal provided by an embodiment of the present invention;
fig. 7(a) is a schematic diagram of a time-frequency analysis result before frequency doubling provided by an embodiment of the present invention;
fig. 7(b) is a schematic diagram of a time-frequency analysis result after frequency doubling provided by the embodiment of the present invention;
fig. 8 is a schematic structural diagram of a system for generating a differential frequency signal according to an embodiment of the present invention.
Detailed Description
The technical solutions in the embodiments of the present invention will be described clearly and completely with reference to the accompanying drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only some embodiments of the present invention, not all embodiments. The components of embodiments of the present invention, as generally described and illustrated in the figures herein, may be arranged and designed in a wide variety of different configurations. Thus, the following detailed description of the embodiments of the present invention, presented in the accompanying drawings, is not intended to limit the scope of the invention, as claimed, but is merely representative of selected embodiments of the invention. Based on the embodiment of the present invention, all other embodiments obtained by the person skilled in the art without creative work belong to the protection scope of the present invention.
It should be noted that: like reference numbers and letters refer to like items in the following figures, and thus, once an item is defined in one figure, it need not be further defined and explained in subsequent figures. Meanwhile, in the description of the present invention, the terms "first", "second", and the like are used only for distinguishing the description, and are not to be construed as indicating or implying relative importance.
Fig. 2 is a schematic structural diagram of a differential frequency signal generating apparatus according to an embodiment of the present invention, as shown in fig. 2, the differential frequency signal generating apparatus includes a terahertz transmitter 201, a first local vibration source 202, a first mixing detector 203, a first power amplifier 204, and a signal processing link 205, which are sequentially connected in a communication manner; wherein,
the terahertz transmitter 201 is used for transmitting a first terahertz wave to a target to be detected; the terahertz transmitter 201 transmits a first terahertz wave with a certain power and an oscillation frequency, and emits the first terahertz wave to a target to be measured, and the target to be measured reflects the first terahertz wave, thereby generating a reflected wave.
The first local vibration source 202 is used for generating a second terahertz wave with certain power; it should be noted that the frequency of the second terahertz wave needs to satisfy a preset requirement.
The first mixing detector 203 is configured to mix a reflected wave corresponding to the first terahertz wave reflected by the target to be measured with the second terahertz wave to obtain a first difference frequency signal; since the first terahertz wave generated by the terahertz generator has a very high vibration frequency (the vibration frequency is in the order of 12 times of 10), and the vibration frequency of the corresponding reflected wave is also very high, the doppler shift information carried by the terahertz generator cannot be directly measured. The first mixing detector is required to mix the reflected wave and the local oscillation signal and output a signal with a lower frequency for detection. The reflected wave and the second terahertz wave are both input into the first mixing detector 203 for mixing, and a first difference frequency signal with a lower vibration frequency is obtained.
The first power amplifier 204 is configured to perform power amplification on the first difference frequency signal, so that the amplified first difference frequency signal meets a power requirement of a signal processing link on an input signal, and input the amplified first difference frequency signal into the signal processing link.
The signal processing link 205 comprises a frequency multiplier 2051, a second local oscillator 2052 and a second mixing detector 2053; the frequency multiplier 2051 is configured to receive and multiply the amplified first difference frequency signal to obtain a second difference frequency signal, where a frequency of a doppler shift signal in the second difference frequency signal is expanded by N times, and it should be noted that the expanded times are related to frequency multiplication times of the frequency multiplier 2051. Since the carrier frequency of the second difference frequency signal is increased by N times after the second difference frequency signal is frequency-multiplied by the frequency multiplier 2051, which may exceed the recording bandwidth of a signal recording system (oscilloscope), the second difference frequency signal needs to be frequency-mixed, the second local oscillator 2052 is configured to generate a radio frequency signal with a certain frequency, input the second difference frequency signal and the radio frequency signal into the second frequency mixing detector 2053, and the second frequency mixing detector 2053 is configured to frequency-mix the second difference frequency signal and the radio frequency signal, so that the carrier frequency in the second difference frequency signal is reduced, and a third difference frequency signal is obtained and output. It should be noted that the third difference frequency signal may be used as the base data for performing the time-frequency analysis.
It should be noted that the frequency multiplier may be a transistor frequency multiplier, a varactor frequency multiplier, or a step recovery diode frequency multiplier, and may also be other types of frequency multipliers, which is not specifically limited in the embodiments of the present invention. The embodiment of the utility model provides a terahertz transmitter, first this vibration source, first mixing detector, first power amplifier, frequency multiplier, second this vibration source and second mixing detector are the equipment that has existed among the prior art, and its specific model and inner structure are no longer repeated.
The embodiment of the utility model provides a carry out the doubling to first difference frequency signal through the frequency multiplier, obtain second difference frequency signal for Doppler's frequency shift in the second difference frequency signal has enlarged N times, and second difference frequency signal carries out the mixing through second mixing detector, has reduced the carrier frequency in the second mixing detector, thereby the third difference frequency signal that obtains when carrying out time frequency analysis, under short time window, can improve time resolution and speed resolution.
On the basis of the above embodiment, the apparatus further includes an oscilloscope 206 connected to the signal processing link;
the oscilloscope 206 receives and displays the third difference frequency signal sent by the second mixing detector 2053.
In a specific implementation process, fig. 3 is a schematic structural diagram of a difference frequency signal generating apparatus according to another embodiment of the present invention, as shown in fig. 3, the signal processing link 205 is connected to the oscilloscope 206 in communication, and the oscilloscope 206 receives a third difference frequency signal sent from the second mixing detector 2053 and displays the third difference frequency signal on a screen.
The embodiment of the utility model provides a show on sending the third difference frequency signal to oscilloscope, convenience of customers looks over.
On the basis of the above embodiment, the signal processing chain 205 further includes a first filter 2054 and a second filter 2055;
the first filter 2054 is connected to the frequency multiplier 2051, and is configured to perform filtering processing on the amplified first difference frequency signal sent by the first power amplifier 204; after the first power amplifier 204 amplifies the first difference frequency signal, the amplified first difference frequency signal needs to be sent to the signal processing link 205, and after the signal link 205 receives the amplified first difference frequency signal, the signal link 205 first performs filtering processing to filter out spurious signals and noise in the amplified first difference frequency signal.
The second filter 2055 is connected to the second mixer probe 2053, and is configured to perform filtering processing on the third difference frequency signal sent by the second mixer probe 2053. The second filter filters the spurious signals and noise in the third difference frequency signal in the same way as the first filter, and the third difference frequency signal with better signal quality is obtained.
On the basis of the above embodiment, the signal processing chain 205 further includes a second power amplifier 2056 connected to the second mixing detector 2053;
the second power amplifier 2056 is configured to amplify the power of the third difference frequency signal, and after the amplified third difference frequency signal is input to the filter, the third difference frequency signal is convenient for a user to observe.
On the basis of the above embodiment, the frequency of the first terahertz wave is f0The frequency of the second terahertz wave is f0-FcWherein the frequency of the second terahertz wave should satisfy Fc>NΔf1N is the frequency multiplication frequency of the frequency multiplier, Δ f1For the first Doppler frequency shift generated by the movement of the target to be measured, correspondingly, the reflected wave corresponding to the first terahertz wave and the second terahertz wave are input into a frequency multiplier for frequency multiplication to obtain a first difference frequency signal S1(t)＝A1sin[2π(Fc+Δf)t]，A1And t is the amplitude of the first difference frequency signal and time.
The embodiment of the utility model provides a second terahertz wave through satisfying the condition carries out the mixing to the reflected wave to can obtain the requirement that accords with the signal processing link to input signal.
On the basis of the above embodiment, the second difference frequency signal obtained after the first difference frequency signal is input to the frequency multiplier for frequency multiplication is: s2(t)＝A2sin[2πN(Fc+Δf)t]，A2Other parameters for the amplitude of the second difference signal and the above implementationConsistent among the examples, the description is omitted here.
The embodiment of the utility model provides a carry out the doubling to first difference frequency signal through the frequency multiplier, obtain second difference frequency signal for Doppler's frequency shift in the second difference frequency signal has enlarged N times, and second difference frequency signal carries out the mixing through second mixing detector, has reduced the carrier frequency in the second mixing detector, thereby the third difference frequency signal that obtains when carrying out time frequency analysis, under short time window, can improve time resolution and speed resolution.
On the basis of the foregoing embodiment, since the doppler shift signal of the second difference frequency signal obtained by frequency doubling by the frequency multiplier is N times larger, and the carrier frequency is also N times larger, which may exceed the recording bandwidth of the signal recording system (oscilloscope), the second difference frequency signal needs to be mixed again, and the radio frequency signal (frequency F) is obtained from the second local oscillation sourceLO) And the RF signal should satisfy NFc-FLO>N Δ f; when the second difference frequency signal S is added2(t)＝A2sin[2πN(Fc+Δf)t]And FLOAfter being input into the second mixing frequency detector, the third difference frequency signal is S3(t)＝A3sin[2π(NFc-FLO+NΔf)t]，A3For the amplitude of the third difference frequency signal, other parameters are the same as those in the above embodiment, and are not described herein again.
The embodiment of the utility model provides a carry out the doubling to first difference frequency signal through the frequency multiplier, obtain second difference frequency signal for Doppler's frequency shift in the second difference frequency signal has enlarged N times, and second difference frequency signal carries out the mixing through second mixing detector, has reduced the carrier frequency in the second mixing detector, thereby the third difference frequency signal that obtains when carrying out time frequency analysis, under short time window, can improve time resolution and speed resolution.
On the basis of the above embodiments, the signal processing links are multiple, and the multiple signal processing links are connected in a cascade manner.
In a specific implementation procedure, the signal processing chain in the difference frequency signal generating device may be multiple, and the multiple signal processing chains are connected in a cascade manner, that is, the multiple signal processing chains are connected in series.
The embodiment of the utility model provides a thereby carry out frequency multiplication and mixing many times through cascading a plurality of signal processing links, can increase the third Doppler frequency shift signal and enlarge the multiple.
Fig. 4 is a schematic flow chart of a method for generating a differential frequency signal according to an embodiment of the present invention, as shown in fig. 4, the method includes:
step 401: transmitting a first terahertz wave to a measured target through a terahertz transmitter, wherein the measured target reflects a reflected wave;
in a specific implementation process, a terahertz transmitter emits a first terahertz wave to irradiate a measured target, the measured target reflects a reflected wave, and the reflected wave needs to be input into a first mixing detector for mixing because the vibration frequency of the reflected wave is too large.
Step 402: sending a second terahertz wave generated by a first local vibration source and the reflected wave to a first mixing detector for mixing to obtain a first difference frequency signal, and sending the first difference frequency signal to a first power amplifier;
in a specific implementation process, a first local vibration source generates second terahertz waves, the second terahertz waves are required to be added when the reflected waves are mixed, the first mixing detector mixes the input second terahertz waves and the reflected waves to obtain a first difference frequency signal, and the first difference frequency signal is sent to a first power amplifier to be amplified.
Step 403: the first power amplifier amplifies the power of the first difference frequency signal and sends the amplified first difference frequency signal to a signal processing link, and the signal processing link comprises a frequency multiplier, a second local vibration source and a second frequency mixing detector;
in a specific implementation process, the first power amplifier amplifies the power of the first difference frequency signal to obtain an amplified first difference frequency signal, and sends the amplified first difference frequency signal to the signal processing link, so that the signal processing link continues to process the amplified first difference frequency signal. It should be noted that, the signal processing chain includes a frequency multiplier, a second local oscillator, and a second mixing detector, and it should be noted that, other devices may also be included in the signal processing chain, for example: any one or a combination of the first filter, the second filter, and the second power amplifier, which is not particularly limited in the embodiments of the present invention.
Step 404: the frequency multiplier is used for multiplying the frequency of the amplified first difference frequency signal to obtain a second difference frequency signal;
in a specific implementation process, a frequency multiplier in the signal processing link multiplies the frequency of the doppler frequency shift signal in the amplified first difference frequency signal, so that the frequency of the doppler frequency shift signal is expanded by N times to obtain a second difference frequency signal.
Step 405: and inputting the radio frequency signal generated by the second local vibration source and the second difference frequency signal into the second frequency mixing detector for frequency mixing to obtain a third difference frequency signal.
In a specific implementation process, after the second difference frequency signal is frequency-multiplied by the frequency multiplier, the carrier frequency of the second difference frequency signal is also increased by N times, which may exceed a recording bandwidth of a signal recording system (oscilloscope), so that the second difference frequency signal needs to be frequency-mixed, the second local oscillator is used to generate a radio frequency signal with a certain frequency, the second difference frequency signal and the radio frequency signal are input into a second frequency-mixing detector, and the second frequency-mixing detector is used to frequency-mix the second difference frequency signal and the radio frequency signal, so that the carrier frequency in the second difference frequency signal is reduced, a third difference frequency signal is obtained, and the third difference frequency signal is output. It should be noted that the third difference frequency signal may be used as the base data for performing the time-frequency analysis.
The embodiment of the utility model provides a carry out the doubling to first difference frequency signal through the frequency multiplier, obtain second difference frequency signal for Doppler's frequency shift in the second difference frequency signal has enlarged N times, and second difference frequency signal carries out the mixing through second mixing detector, has reduced the carrier frequency in the second mixing detector, thereby the third difference frequency signal that obtains when carrying out time frequency analysis, under short time window, can improve time resolution and speed resolution.
Additionally, the embodiment of the utility model provides a to the difference frequency signal that produces through difference frequency signal generating device as time frequency analysis's data basis, can improve time resolution and speed resolution and carry out theoretical analysis and numerical simulation, specifically as follows:
assuming that the motion speed history of the measured target is u (u) (t), the frequency of the terahertz wave reflected by the measured target is changed from the original frequency f0Is changed into f0+Δf＝f0+2u(t)f0C, the signal is mixed with a frequency f in the first mixing detector0-FcThe second terahertz wave is mixed and a first difference frequency signal of the two is output as
The first difference frequency signal is input into a frequency multiplier to obtain a second difference frequency signal
The second difference frequency signal is input to a second mixer detector and has a frequency FLOThe first difference frequency signal is obtained by mixing and filtering the signals through a second filter, and the third difference frequency signal is output, wherein the third difference frequency signal is:
as can be seen, the above equation converts the Doppler-shifted signal from the original 2u (t) f0Increased by N times to 2Nu (t) f0/c。
The MatLAB is used to perform numerical simulation on the above process, the first terahertz wave generated according to the velocity history of the moving object is inputted into the differential frequency signal generating device of the present invention for processing, and the outputted third differential frequency signal and the first terahertz wave are respectively subjected to time-frequency analysis, FIG. 5(a) is a schematic diagram of Doppler frequency shift before frequency doubling provided by the embodiment of the present invention, FIG. 5(b) is a schematic diagram of Doppler frequency shift after frequency doubling provided by the embodiment of the present invention, FIG. 6(a) is a schematic diagram of velocity history of the object to be measured provided by the embodiment of the present invention, FIG. 6(b) is a schematic diagram of terahertz interference signal provided by the embodiment of the present invention, wherein the original interference signal is the first terahertz wave, the signal after 16 frequency doubling is a second differential frequency signal obtained after frequency doubling by the frequency multiplier, and FIG. 7(a) is a schematic diagram of the result of time-frequency analysis provided by the embodiment of the present invention, fig. 7(b) is a schematic diagram of a time-frequency analysis result after frequency doubling provided by the embodiment of the present invention.
From the time-frequency analysis results (fig. 7(a) - (b)), it can be seen that the speed resolution (longitudinal) is greatly improved even with a shorter time window (3.3 times to 30ns shorter from 100 ns) after 16 frequency multiplications compared to the original signal without frequency multiplication.
Specific simulation parameters:
target object movement speed:
frequency f of first terahertz wave emitted by terahertz transmitter0220GHz, corresponding doppler shift Δ f 14.7 MHz;
the frequency multiplier frequency multiplication number N is 16;
frequency f of second terahertz wave emitted by first local vibration source0+Fc220.630GHz, Fc > N Δ f;
the frequency of the signal emitted by the second local vibration source is 9GHz, which meets the NFc-FLO>Condition of N Δ f;
in time-frequency analysis, for an un-multiplied frequency signal, a time window of short-time Fourier transform is equal to 100ns in Δ t1, and for a multiplied frequency signal, is equal to 30ns in Δ t 2;
the oscilloscope sample rate is 40 GS/s.
Fig. 8 is a schematic structural diagram of a system for generating a difference frequency signal according to an embodiment of the present invention, as shown in fig. 8, the system includes a difference frequency signal generating apparatus 801 and a terminal device 802, wherein,
the difference frequency signal generating device 801 is communicatively connected to the terminal device 802, and the difference frequency signal generating device 801 is any one of the above embodiments, and is configured to generate a third difference frequency signal. The terminal device 802 may be a computer or other portable handheld device, and the terminal device 802 is configured to receive the third difference frequency signal generated by the difference frequency signal generating apparatus 801 and perform time-frequency analysis on the third difference frequency signal. It should be noted that the process of analyzing the time frequency of the third difference frequency signal by the terminal device 802 is the prior art, and is not protected by the present invention.
The embodiment of the utility model provides a carry out the doubling to first difference frequency signal through the frequency multiplier, obtain second difference frequency signal for Doppler's frequency shift in the second difference frequency signal has enlarged N times, and second difference frequency signal carries out the mixing through second mixing detector, has reduced the carrier frequency in the second mixing detector, thereby the third difference frequency signal that obtains when carrying out time frequency analysis, under short time window, can improve time resolution and speed resolution.
In the embodiments provided in the present application, it should be understood that the disclosed apparatus and method can be implemented in other ways. The apparatus embodiments described above are merely illustrative, and for example, the flowchart and block diagrams in the figures illustrate the architecture, functionality, and operation of possible implementations of apparatus, methods and computer program products according to various embodiments of the present invention. In this regard, each block in the flowchart or block diagrams may represent a module, segment, or portion of code, which comprises one or more executable instructions for implementing the specified logical function(s). It should also be noted that, in some alternative implementations, the functions noted in the block may occur out of the order noted in the figures. For example, two blocks shown in succession may, in fact, be executed substantially concurrently, or the blocks may sometimes be executed in the reverse order, depending upon the functionality involved. It will also be noted that each block of the block diagrams and/or flowchart illustration, and combinations of blocks in the block diagrams and/or flowchart illustration, can be implemented by special purpose hardware-based systems which perform the specified functions or acts, or combinations of special purpose hardware and computer instructions.
In addition, the functional modules in the embodiments of the present invention may be integrated together to form an independent part, or each module may exist alone, or two or more modules may be integrated to form an independent part.
The functions, if implemented in the form of software functional modules and sold or used as a stand-alone product, may be stored in a computer readable storage medium. Based on such understanding, the technical solution of the present invention may be embodied in the form of a software product, which is stored in a storage medium and includes instructions for causing a computer device (which may be a personal computer, a server, or a network device) to perform all or part of the steps of the method according to the embodiments of the present invention. And the aforementioned storage medium includes: a U-disk, a removable hard disk, a Read-Only Memory (ROM), a Random Access Memory (RAM), a magnetic disk or an optical disk, and other various media capable of storing program codes.
The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention, and various modifications and changes may be made by those skilled in the art. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention. It should be noted that: like reference numbers and letters refer to like items in the following figures, and thus, once an item is defined in one figure, it need not be further defined and explained in subsequent figures.
The above description is only for the specific embodiments of the present invention, but the protection scope of the present invention is not limited thereto, and any person skilled in the art can easily think of the changes or substitutions within the technical scope of the present invention, and all should be covered within the protection scope of the present invention. Therefore, the protection scope of the present invention shall be subject to the protection scope of the claims.
It is noted that, herein, relational terms such as first and second, and the like may be used solely to distinguish one entity or action from another entity or action without necessarily requiring or implying any actual such relationship or order between such entities or actions. Also, the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising an … …" does not exclude the presence of other identical elements in a process, method, article, or apparatus that comprises the element.
Claims (10)
1. A differential frequency signal generating apparatus, comprising: the terahertz transmitter, the first local vibration source, the first mixing detector, the first power amplifier and the signal processing link are sequentially in communication connection; wherein,
the terahertz transmitter is used for transmitting a first terahertz wave to a target to be detected;
the first local vibration source is used for generating second terahertz waves;
the first frequency mixing detector is used for mixing a reflected wave corresponding to the first terahertz wave reflected by the measured object with the second terahertz wave to obtain a first difference frequency signal;
the first power amplifier is used for performing power amplification on the first difference frequency signal;
the signal processing link comprises a frequency multiplier, a second local vibration source and a second frequency mixing detector; the frequency multiplier is configured to receive and multiply the amplified first difference frequency signal to obtain a second difference frequency signal, the second local oscillator is configured to generate a radio frequency signal, and the second mixing detector is configured to mix the second difference frequency signal and the radio frequency signal to obtain a third difference frequency signal and output the third difference frequency signal.
2. The apparatus of claim 1, further comprising an oscilloscope connected to the signal processing chain;
and the oscilloscope receives the third difference frequency signal sent by the second mixing detector and displays the third difference frequency signal.
3. The apparatus of claim 1, wherein the signal processing chain further comprises a first filter and a second filter;
the first filter is connected with the frequency multiplier and is used for filtering the amplified first difference frequency signal sent by the first power amplifier;
and the second filter is connected with the second mixing detector and is used for filtering the third difference frequency signal sent by the second mixing detector.
4. The apparatus of claim 1, wherein the signal processing chain further comprises a second power amplifier connected to the second mixing detector;
the second power amplifier is used for amplifying the power of the third difference frequency signal.
5. The apparatus of claim 1, wherein the frequency multiplier is a transistor frequency multiplier, a varactor frequency multiplier, or a step recovery diode frequency multiplier.
6. The device of claim 1, wherein the frequency of the first terahertz wave is f0The frequency of the second terahertz wave is f0-FcWherein F isc>NΔf1N is the frequency multiplication frequency of the frequency multiplier, Δ f1For a first Doppler shift, the first difference frequency signal is S1(t)＝A1sin[2π(Fc+Δf)t]，A1And t is the amplitude of the first difference frequency signal and time.
7. The apparatus of claim 6, wherein the second difference frequency signal is: s2(t)＝A2sin[2πN(Fc+Δf)t]，A2Is the amplitude of the second difference frequency signal.
8. The apparatus of claim 7, wherein the radio frequency signal has a frequency of: fLOWherein, NF isc-FLO>N Δ f; the third difference frequency signal is: s3(t)＝A3sin[2π(NFc-FLO+NΔf)t]，A3Is the amplitude of the third difference frequency signal.
9. The apparatus according to any one of claims 1-8, wherein said signal processing chain is plural, and said plural signal processing chains are connected in a cascade manner.
10. A difference frequency signal generation system comprising a terminal device and the difference frequency signal generation apparatus of any one of claims 1-9 communicatively connected;
the difference frequency signal generating device is used for generating a third difference frequency signal, and the terminal equipment is used for carrying out time-frequency analysis on the third difference frequency signal.
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Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
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| CN110716193A (en) * | 2019-12-12 | 2020-01-21 | 深圳市迈测科技股份有限公司 | Signal generation method and device |
| US11747474B2 (en) | 2019-11-18 | 2023-09-05 | Shenzhen Mileseey Technology Co., Ltd. | Systems and methods for laser distance measurement |
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Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US11747474B2 (en) | 2019-11-18 | 2023-09-05 | Shenzhen Mileseey Technology Co., Ltd. | Systems and methods for laser distance measurement |
| CN110716193A (en) * | 2019-12-12 | 2020-01-21 | 深圳市迈测科技股份有限公司 | Signal generation method and device |
| CN110716193B (en) * | 2019-12-12 | 2020-05-08 | 深圳市迈测科技股份有限公司 | Signal generation method and device |
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