CN113608176A - Self-adaptive cancellation circuit of frequency modulation continuous wave radar - Google Patents
Self-adaptive cancellation circuit of frequency modulation continuous wave radar Download PDFInfo
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- CN113608176A CN113608176A CN202110970527.7A CN202110970527A CN113608176A CN 113608176 A CN113608176 A CN 113608176A CN 202110970527 A CN202110970527 A CN 202110970527A CN 113608176 A CN113608176 A CN 113608176A
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
- G01S7/00—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00
- G01S7/02—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00 of systems according to group G01S13/00
- G01S7/35—Details of non-pulse systems
Abstract
The invention discloses a self-adaptive cancellation circuit of a frequency modulation continuous wave radar, which comprises the following components: the power divider is used for averagely dividing the radar signal into two paths of signals to be output, wherein the two paths of signals are a first path of emission signal and a second path of signal LO respectively; the frequency mixer is used for receiving two paths of signals output by the power divider, wherein one path of signals is used as a local oscillator of the frequency mixer, and the other path of signals is used for receiving the frequency mixer; the self-coupling signal delay of the radio frequency input port of the mixer is the same as the delay of the second path of signal LO. According to the invention, the LO wiring delay is added, so that the LO wiring path delay is equal to the antenna self-coupling path delay, and the self-coupling intermediate-frequency signal obtained by mixing is close to zero frequency, so that the self-coupling intermediate-frequency signal can be easily filtered by a filter, and the signal-to-noise ratio deterioration caused by impulse response is greatly reduced.
Description
Technical Field
The invention relates to the technical field of radars, in particular to a self-adaptive cancellation circuit of a frequency modulation continuous wave radar.
Background
The frequency modulation continuous wave radar is a continuous wave radar with the transmitting frequency modulated by a specific signal. The frequency modulation continuous wave radar obtains the distance information of the target by comparing the difference between the frequency of the echo signal at any moment and the frequency of the transmitting signal at the moment, and the distance is proportional to the frequency difference between the two frequencies. The radial speed and the distance of the target can be obtained after the measured frequency difference between the radial speed and the distance is processed, and compared with other distance measuring and speed measuring radars, the frequency modulation continuous wave radar has a simpler structure.
The antenna is limited by the limited product size of the radar, and the antenna is difficult to achieve high isolation, so that the self-coupling problem exists, and the signal-to-noise ratio of the radar is difficult to improve. The following approaches currently exist to reduce the self-coupling problem to improve signal-to-noise ratio: 1. cancellation modes, such as software cancellation, intermediate frequency subtraction cancellation, and radio frequency adaptive cancellation; 2. high isolation antennas. However, by using software cancellation, the complicated software algorithm can prolong the calculation time, and even the signal-to-noise ratio is too low to extract the distance information under a certain condition; the intermediate frequency subtraction cancellation method needs to form a loop feedback link, the link is relatively complex, and the cost of devices is increased; the radio frequency self-adaptive cancellation scheme link is relatively complex, and the cost of devices and more layout space are required to be increased; the high isolation antenna is difficult to realize and limited in isolation due to size limitation, so that the intermediate frequency signal always remains as a self-coupling signal.
The background description provided herein is for the purpose of generally presenting the context of the disclosure. Unless otherwise indicated herein, the material described in this section is not prior art to the claims in this application and is not admitted to be prior art by inclusion in this section.
Disclosure of Invention
In view of the above technical problems in the related art, the present invention provides an adaptive cancellation circuit for a frequency modulated continuous wave radar, which includes the following components: the power divider is used for averagely dividing the radar signal into two paths of signals to be output, wherein the two paths of signals are a first path of emission signal and a second path of signal LO respectively;
the frequency mixer is used for receiving two paths of signals output by the power divider, wherein one path of signals is used as a local oscillator of the frequency mixer, and the other path of signals is used as a receiving RF of the frequency mixer;
the self-coupling signal delay of the radio frequency input port of the mixer is the same as the delay of the second path of signal LO.
Specifically, the delay of the second path of signal LO is implemented by microstrip routing.
Specifically, the microstrip routing is a serpentine routing.
Specifically, the microstrip routing is a cascade inductor capacitor.
Specifically, the cascade inductor capacitor is single or multiple.
Specifically, the cascade inductor capacitor is formed by connecting an inductor and a capacitor in series, and one end of the capacitor is grounded.
Specifically, the adaptive cancellation circuit of the frequency modulated continuous wave radar further comprises a signal processor, and the signal processor is used for processing the signal output by the filter.
Specifically, the adaptive cancellation circuit of the frequency modulated continuous wave radar further comprises a filter, and the filter receives the output of the mixer.
In a second aspect, the present invention provides a frequency modulated continuous wave radar comprising an antenna and an adaptive cancellation circuit for a frequency modulated continuous wave radar as described in any one of the preceding.
According to the invention, the LO wiring delay is added, so that the LO wiring path delay is equal to the antenna self-coupling path delay, and the self-coupling intermediate-frequency signal obtained by mixing is close to zero frequency, so that the self-coupling intermediate-frequency signal can be easily filtered by a filter, and the signal-to-noise ratio deterioration caused by impulse response is greatly reduced.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings needed in the embodiments will be briefly described below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and it is obvious for those skilled in the art to obtain other drawings without creative efforts.
Fig. 1 is a schematic diagram of an adaptive cancellation circuit of an fm continuous wave radar according to an embodiment of the present invention;
FIG. 2 is a schematic diagram of a serpentine trace according to an embodiment of the present invention;
fig. 3 is a schematic diagram of a group delay obtained by the serpentine routing according to an embodiment of the present invention;
FIG. 4 is a schematic diagram of a series-parallel inductor-capacitor according to an embodiment of the present invention;
fig. 5 is a graph illustrating the group delay obtained by the series-parallel inductor capacitor according to an embodiment of the present invention;
fig. 6 is a schematic diagram of the S parameter obtained by the series-parallel inductor capacitor provided by the present invention.
In the figure, TX: transmitting; RX: receiving; ps is a useful echo signal; pj: a self-coupling signal; LO is the local oscillator input of the frequency mixer; RF: a mixer radio frequency input; IF: an intermediate frequency signal; l: microstrip line length from output port No. 1 of power divider to local oscillation input port of mixer; pj _ delay: the self-coupling signal from the output port No. 2 of the power divider to the radio frequency input port of the frequency mixer is delayed; LO _ delay: delaying the signal from the output port No. 1 of the power divider to the input port of the mixer LO; k: system frequency modulation coefficient
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments that can be derived by one of ordinary skill in the art from the embodiments given herein are intended to be within the scope of the present invention.
Example one
Referring to fig. 1, the present embodiment discloses an adaptive cancellation circuit for a frequency modulated continuous wave radar, which includes the following circuit devices:
a signal processing circuit: the signal processing circuit is used for processing radar signals and performing cancellation processing.
A power divider: the two-path power divider is used for averagely dividing radar signals into two paths or multiple paths of devices with equal power output, the two paths of power dividers are used for averagely dividing the radar signals into two paths of signals to be output, the two paths of signals are specifically output and are respectively a first path of transmitting signals, a second path of signals LO, the second path of signals LO is used as local oscillators of the frequency mixer, and the first path of transmitting signals are transmitted out through an antenna TX of a radar.
A mixer: the receiving RF of the mixer is that the signal is received by an antenna RX of a radar and is transmitted to the mixer.
And the filter is used for filtering the received radar signals and transmitting the filtered signals to the signal processor for processing.
The mixer is used for multiplying the received radio frequency signal RF by a signal generated by a local oscillator to generate an intermediate frequency signal. In this embodiment, the local oscillation signal of the frequency mixer is a path of signal output by the power divider, and the reception of the frequency mixer is also a path of signal output by the power divider.
Specifically, the second path of signal LO in this embodiment is used as a local oscillator input of the frequency mixer, and the first path of transmission signal is received by the radar and then used as a receiving RF of the frequency mixer.
Specifically, referring to fig. 1, Pj _ delay refers to self-coupling signal delay from the output port No. 2 of the power divider to the RF input port of the mixer, specifically, transmission time that a first path of transmission signal is transmitted from the output port of the power divider through a radar and received as a reception RF of the mixer to reach the RF port of the mixer.
The second path of signal delay LO _ delay refers to the signal delay from the output port of the power divider No. 1 to the input port of the mixer LO.
In this embodiment, the mixer can obtain two intermediate frequency signals with respective frequency points of IF1 ═ FLO-FPjAnd IF2 ═ FLO-FPs. Where IF1 is a self-coupled intermediate frequency signal that needs to be eliminated. In the fm continuous wave radar system, the IF frequency is proportional to the delay time duration of the signal, i.e., IF1 ═ K (Pj _ delay-LO _ delay), in order to achieve the purpose of eliminating the self-coupled IF signal, IF1 is required to be 0Hz, i.e., Pj _ delay-LO _ delay is 0.
In this embodiment, the purpose of changing LO _ delay can be achieved by controlling the length of the LO routing winding line during board distribution, and IF1 can be made 0Hz by controlling L so that Pj _ delay-LO _ delay is 0. Namely, the intermediate frequency interference introduced by the self-coupling signal is zero frequency, the self-coupling interference can be effectively filtered through the IF filter, and large impact response is not generated.
Referring to the schematic diagram of the serpentine trace in fig. 2, in this embodiment, the transmission of the signal from the output port of the power divider No. 1 to the local oscillation input port of the mixer is implemented by a PCB trace, and the specific PCB trace may be a microstrip trace. In the embodiment, the signal delay LO _ delay from the output port No. 1 of the power divider to the input port of the mixer LO is increased by the serpentine routing.
The length of the microstrip line between the starting end and the stopping end is increased by bending the microstrip line in the PCB with the limited size to and fro, so that the local oscillator delay LO _ delay is increased, and Pj _ delay-LO _ delay is realized to be 0.
Referring to fig. 3, the group delay corresponding to the serpentine trace is shown. Assuming that the radar signal operates at 2GHz, the microstrip line is delayed by 0.14 ns.
Referring to fig. 4, the present embodiment also provides a method for greatly increasing the trace delay through the series-parallel inductor capacitance. Fig. 4 is a layout wiring manner for increasing the delay by using the series-parallel inductor capacitor, and the size of the distance between the start point and the stop point is the same as that of the snake-shaped wiring in fig. 3. Fig. 5 shows the group delay result corresponding to the trace of fig. 4, which shows that when the microstrip line operates at 2GHz, the delay of the microstrip line is 0.54 ns. The comparison shows that under the condition of the same size, the time delay of the series-parallel inductance and capacitance mode is about 3.8 times of that of the snake-shaped routing, and the time delay is greatly improved.
Referring to fig. 4, in the present embodiment, the inductor and the capacitor are connected in series, the capacitor is grounded, one end of the inductor close to the capacitor is an output port, and one end of the inductor far from the capacitor is an input port, and the inductor and the capacitor form a basic inductor-capacitor unit.
Specifically, the input port is configured to receive the output port of the power divider 1, and the output port is configured to receive a local oscillation port of the mixer. The above description is for the purpose of illustrating an lc cell.
The number of the cascaded inductor-capacitor in the present embodiment may be single or plural. The present embodiment is not particularly limited, and a plurality of inductors and capacitors may be cascaded according to specific delay requirements.
When the number of the cascaded inductance capacitors is multiple, the input port is used for receiving the output port of the power divider No. 1 or the output port of the previous inductance capacitor, and the output port is used for being connected with the local oscillator port of the frequency mixer or the input port of the next inductance capacitor.
In the embodiment, the series-parallel inductor-capacitor mode not only increases the routing delay, but also can synchronously realize filtering. Low-pass filtering is preferably achieved with reference to fig. 6, which is an S-parameter curve of db (S (6,5)) for the S-parameter obtained for the trace layout shown in fig. 5, where the solid line is db (S (6,5)), and the dashed line is db (S (5, 5)).
According to the invention, the local oscillator signal delay of the frequency mixer is increased to be equal to the self-coupling signal delay, so that the self-coupling intermediate-frequency signal is zero frequency. The purpose of changing LO _ delay can be achieved by controlling the length of the LO wiring winding wire during board distribution, and the IF1 can be made to be 0Hz by controlling L to enable Pj _ delay-LO _ delay to be 0. Namely, the intermediate frequency interference introduced by the self-coupling signal is zero frequency, the self-coupling interference can be effectively filtered through the IF filter, and large impact response is not generated. In addition, the filtering effect can be realized while the high-frequency wiring delay is increased by connecting the inductive capacitors in series and parallel in the high-frequency wiring.
Example two
The embodiment provides a frequency modulation continuous wave radar which comprises an antenna, wherein the specific antenna can respectively comprise a receiving antenna and a transmitting antenna, or the receiving antenna and the transmitting antenna share one antenna. Furthermore, the frequency modulated continuous wave radar comprises an adaptive cancellation circuit of the frequency modulated continuous wave radar as mentioned in the first embodiment.
According to the embodiment, the LO wiring delay is increased, so that the LO wiring path delay is equal to the antenna self-coupling path delay, the self-coupling intermediate-frequency signal which is mixed out is close to zero frequency, the self-coupling intermediate-frequency signal can be easily filtered by a filter, and the signal-to-noise ratio deterioration caused by the impact response is greatly reduced.
The above description is only for the purpose of illustrating the preferred embodiments of the present invention and is not to be construed as limiting the invention, and any modifications, equivalents, improvements and the like that fall within the spirit and principle of the present invention are intended to be included therein.
Claims (10)
1. An adaptive cancellation circuit of a frequency modulated continuous wave radar comprises the following components:
the power divider is used for averagely dividing the radar signal into two paths of signals to be output, wherein the two paths of signals are a first path of emission signal and a second path of signal LO respectively;
the frequency mixer is used for receiving two paths of signals output by the power divider, wherein one path of signals is used as a local oscillator of the frequency mixer, and the other path of signals is used as a receiving RF of the frequency mixer;
the self-coupling signal delay of the radio frequency input port of the mixer is the same as the delay of the second path of signal LO.
2. The adaptive cancellation circuit for frequency modulated continuous wave radar as claimed in claim 1, wherein said second LO signal is a local oscillator of said mixer.
3. The adaptive cancellation circuit for frequency modulated continuous wave radar according to claim 1, wherein the second signal LO is delayed by microstrip routing.
4. An adaptive cancellation circuit for frequency modulated continuous wave radar according to claim 3, wherein said microstrip trace is a serpentine trace.
5. The adaptive cancellation circuit for frequency modulated continuous wave radar as claimed in claim 3, wherein said microstrip trace is a cascaded inductor-capacitor.
6. An adaptive cancellation circuit for frequency modulated continuous wave radar as claimed in claim 5, wherein said cascaded inductor capacitors are single or plural.
7. The adaptive cancellation circuit for frequency modulated continuous wave radar as claimed in claim 6, wherein said cascaded inductor capacitor is an inductor connected in series with a capacitor, and one end of said capacitor is grounded.
8. An adaptive cancellation circuit for a frequency modulated continuous wave radar according to any one of claims 1 to 7 further comprising a filter receiving the output of the mixer.
9. An adaptive cancellation circuit for a frequency modulated continuous wave radar according to any one of claims 1 to 7, further comprising a signal processor for processing the signal output by the filter.
10. A frequency modulated continuous wave radar comprising an antenna and an adaptive cancellation circuit for a frequency modulated continuous wave radar as claimed in any one of claims 1 to 9.
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| CN202110970527.7A CN113608176A (en) | 2021-08-23 | 2021-08-23 | Self-adaptive cancellation circuit of frequency modulation continuous wave radar |
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| CN103634002A (en) * | 2013-12-23 | 2014-03-12 | 北京无线电计量测试研究所 | Real-time calibration system and method for broadband VCO (Voltage Controlled Oscillator) linearity |
| CN111638504A (en) * | 2019-03-01 | 2020-09-08 | 北京聚利科技有限公司 | Continuous wave radar front end |
| CN112747878A (en) * | 2020-10-19 | 2021-05-04 | 上海交通大学 | Non-contact sound barrier structure monitoring method and system based on microwave radar |
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- 2021-08-23 CN CN202110970527.7A patent/CN113608176A/en active Pending
Patent Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| KR20070059861A (en) * | 2005-12-07 | 2007-06-12 | 한국전자통신연구원 | Rf transceiver module and millimeterwave fmcw radar sensor using the same |
| CN103634002A (en) * | 2013-12-23 | 2014-03-12 | 北京无线电计量测试研究所 | Real-time calibration system and method for broadband VCO (Voltage Controlled Oscillator) linearity |
| CN111638504A (en) * | 2019-03-01 | 2020-09-08 | 北京聚利科技有限公司 | Continuous wave radar front end |
| CN112747878A (en) * | 2020-10-19 | 2021-05-04 | 上海交通大学 | Non-contact sound barrier structure monitoring method and system based on microwave radar |
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