CN105824020A - Subcarrier-modulation-based continuous wave Doppler radar sensor and motion demodulation method - Google Patents

Abstract

The invention discloses a subcarrier-modulation-based continuous wave Doppler radar sensor and a motion demodulation method. A radio-frequency transceiver chip is connected with a control module; a clock distribution module is connected with the control module and the radio-frequency transceiver chip; and the radio-frequency transceiver chip has transmitting and receiving functions. After clock distribution of a crystal oscillator, two paths of low-frequency sinusoidal signals are generated and one path of signal is transmitted to the control module for digital modulation; the radio-frequency transceiver chip generates two paths of sinusoidal continuous wave radio-frequency carrier signals, one path of signal is a local oscillator signal, and the other path of signal and the low-frequency sinusoidal signals are mixed to generate a subcarrier signal for detection; after under sampling of an echo, the processed signal is transmitted to the control module; filter, mixing, and demodulation are carried and then an anti-trigonometric function is calculated to obtain phase information; a distance and relative displacement information are calculated based on a phase difference; and a motion track is recovered. According to the invention, defects of inherent direct-current excursion and scintillation noises of the traditional zero-intermediate-frequency architecture type receiver can be overcome. While the simple structure and low cost of the zero-intermediate-frequency receiver are kept, the image-frequency suppression function of which the traditional low-intermediate-frequency architecture type receiver is lack is also realized.

Description

The continuous wave Doppler radar sensor of subcarrier modulation and motion demodulation method

Technical field

The present invention relates to a kind of radar sensor and detection method, especially relate to continuous wave Doppler radar sensor and the motion demodulation method of the modulation of a kind of subcarrier.

Background technology

Subcarrier (subcarrier) is a kind of electrical communication signals carrier wave, and it is a kind of radio frequency electrical carrier wave by analog baseband signal premodulated.From frequency spectrum, it carries the upper end at another carrier wave or the left and right sides at carrier wave, thus two signals can have effect spread simultaneously.At receiving terminal, the subcarrier signal of double frequency-band demodulates respectively, and two frequency bands can be used in diverse purposes.In communication, channel subcarrier can be used in the various uses such as radio paging, stock transmission, traffic control light conversion and background music.

At radar sensing and Aerospace Tracking & Control, the double frequency velocity-measuring systems using similar subcarrier signal measure radial velocity more.Such as spacecraft sends two frequencies simultaneously and becomes the radio signal of certain multiple relation, when spacecraft and ground relative motion, the signal of two frequency bands all can produce Doppler frequency shift, this frequency displacement is proportional to the velocity component on tracking telemetry and command station spacecraft direction, extract two Doppler frequency shift amounts respectively and make relevant treatment, it is achieved with the target relative radial rate to tracking telemetry and command station, and the ionosphere impact on propagation velocity of electromagnetic wave can be eliminated, improve rate accuracy.

And continuous wave Doppler radar sensor framework mainly has two kinds: one to be Direct-conversion structure at present, its local oscillation signal is identical with the radio frequency signal frequency received, and therefore directly obtains baseband signal after mixing.The selection of channel and amplification adjust and carry out in base band.There is not image interference, beneficially single-chip integration in this structure.But Direct-conversion structure also exists the problems such as DC deviation, local-oscillator leakage and flicker noise.Two is super-heterodyne architecture, needs to carry out twice down coversion.Down coversion for the first time, produces the intermediate-freuqncy signal of fixed frequency.Then, neighbouring channel signals is removed by intermediate-freuqncy signal through if bandpas filter, then carries out second time down coversion and obtain required baseband signal.Owing to there being multiple converter stage, DC deviation and local-oscillator leakage problem do not interfere with the performance of receiver.But in order to suppress Image interference suppression and select channel, needing the band filter of high q-factor, they can only realize outside transceiver, thus increases cost and size.

Summary of the invention

The present invention is in order to simplify doppler radar system, reduce system cost, raising system stability, provide continuous wave Doppler radar sensor and the motion demodulation method of the modulation of a kind of subcarrier, can be widely applied to the systems such as in-plant motion measurement, ranging and range rate, tracing and positioning, it is achieved the non-contact measurement of the physical quantity under different occasions.

Therefore, during the present invention considers to sense subcarrier modulated applications to Doppler radar, in conjunction with the advantage of tradition doppler radar sensor structure, and motion demodulation method is used to obtain distance and the movable information of object under test.

The technical solution used in the present invention is:

One, the continuous wave Doppler radar sensor of a kind of subcarrier modulation:

Including radio frequency transceiver chip, control module and clock generation module, clock generation module includes clock distribution block and crystal oscillator, radio frequency transceiver chip is connected with control module through analog-digital converter, one outfan of clock distribution block is connected with control module, and another outfan of clock distribution block is connected with radio frequency transceiver chip through low frequency bandpass filter；The transmitting terminal of radio frequency transceiver chip connects through power amplifier launches antenna, and the most filtered device of receiving terminal of radio frequency transceiver chip, low-noise amplifier connect reception antenna.

Described radio frequency transceiver integrated chip has phaselocked loop and frequency mixer.

The Low Frequency Sine Signals that described crystal oscillator produces is divided into two-way through clock distribution block: a road is sent to radio frequency transceiver chip in order to produce subcarrier signal, and another road is sent to control module and carries out digital demodulation；Radio frequency transceiver chip produces two-way with the synchronous sinusoidal continuous wave radio-frequency carrier signal of frequency: generates subcarrier signal after the Low Frequency Sine Signals mixing that a road and crystal oscillator produce, then exports after power amplifier amplifies, in order to target acquisition；Another road carries out down coversion demodulation as local oscillator for chip internal；Radio frequency transceiver chip receives echo-signal, carries out lack sampling by analog digital conversion again and be transferred to control module after low noise amplification, demodulation by filter.

Control module regulation is launched and the power of receiver module signal, control A/D converter and gather signal, double frequency-band for subcarrier signal each carries the feature of object under test difference doppler information, use demodulation method to calculate object distance and relative displacement according to the phase meter of two frequency bands in the control module, show the most in real time or be transferred to other terminals such as PC.

Described demodulation method includes direct current biasing and the flicker noise filtering baseband signal, and dual band signal carries out phase extraction respectively, it is thus achieved that the doppler information of object of which movement thus obtain object space and recover its movement locus.

Described sinusoidal continuous wave radio-frequency carrier signal and Low Frequency Sine Signals are mixed with frequency and phase place phase add mode.

The described crystal oscillator with radiofrequency signal mixing uses the frequency active crystal oscillator of sine wave far below carrier frequency, is preferably with less than the active crystal oscillator of sine wave of one of percent frequency carrier frequency.

Described A/D converter uses and carries out lack sampling far below the sample frequency of nyquist frequency.

Two, the motion demodulation method of the continuous wave of a kind of subcarrier modulation, including step in detail below:

Being produced Low Frequency Sine Signals by crystal oscillator, be divided into two-way, a road to be sent to radio frequency transceiver chip in order to produce subcarrier signal after clock distribution, another road is sent to control module and carries out digital demodulation；Radio frequency transceiver chip produces two-way with the synchronous sinusoidal continuous wave radio-frequency carrier signal of frequency, one tunnel carries out down coversion demodulation as local oscillator for chip internal, subcarrier signal is generated after the Low Frequency Sine Signals mixing that another road and crystal oscillator produce, then after power amplifier amplifies, output carries out target acquisition, after radio frequency transceiver chip reception target reflection echo-signal successively after low noise amplification, demodulation by filter, carry out lack sampling and be transferred to control module again.

Control module receives the echo-signal after Low Frequency Sine Signals and lack sampling, first at numeric field, the echo-signal after digital-to-analogue conversion is carried out succinct low-pass filtering, filter direct current biasing and flicker noise, then two signals carry out digital mixing demodulation, making the signal frequency after mixing is zero frequency, it is easy to process subsequently, then negate trigonometric function method, obtain the phase information of object under test, finally according to the phase contrast between the echo-signal after Low Frequency Sine Signals and lack sampling, distance and the relative displacement of object under test is calculated by formula, recover its movement locus, complete detection and motion demodulation.

The phase information that described trigonometric function method of negating obtains object under test is specifically represented by below equation:

φ₁(t)=(4 π d₀+x(t))/λ_high+2k₁π

φ₂(t)=(4 π d₀+x(t))/λ_low+2k₂π

Due to trigonometric function all with 2 π as cycle, and trigonometric function gained of negating is monodrome solution, therefore in above two formulas, and k₁, k₂Represent the compensation cycle number of first, second phase information, i.e. k₁, k₂For known integer and unequal, d₀For the initial position of target object, x (t) is displacement or the change of other measured physical quantity, the λ of object under test motion_highAnd λ_lowIt is respectively frequency f_LO+f₁And f_LO-f₁The wavelength corresponding to double frequency electromagnetic wave, f_LOFor the frequency of sinusoidal continuous wave radio-frequency carrier signal, f₁For the frequency of low-frequency sine crystal oscillation signal, φ₁(t) and φ₂T () represents that the echo-signal medium frequency received is f respectively_LO+f₁And f_LO-f₁The respective phase information of double frequency electromagnetic wave.

The movement locus of described object under test is calculated to describe by following formula and obtains:

$d_0+x\left(t\right)=\frac{1}{4\mathrm{\π}\left(1/{\mathrm{\λ}}_{high}-1/{\mathrm{\λ}}_{low}\right)}\[\left({\mathrm{\φ}}_1\left(t\right)-{\mathrm{\φ}}_2\left(t\right)\right)-2\mathrm{\π}\left(m-n\right)\]=\frac{{\mathrm{\φ}}_1\left(t\right)-{\mathrm{\φ}}_2\left(t\right)}{4\mathrm{\π}\left(1/{\mathrm{\λ}}_{high}-1/{\mathrm{\λ}}_{low}\right)}-\frac{\left(m-n\right)}{2\left(1/{\mathrm{\λ}}_{high}-1/{\mathrm{\λ}}_{low}\right)}$

Described sinusoidal continuous wave radio-frequency carrier signal and Low Frequency Sine Signals are mixed with frequency and phase place phase add mode.

Described lack sampling uses and carries out far below the sample frequency of nyquist frequency.

The double frequency-band that the present invention is directed to subcarrier signal each carries the feature of object under test difference doppler information, extracts the phase information of baseband signal, and the demodulation method using the present invention to propose calculates object distance and relative displacement according to the phase meter of two frequency bands.

The invention have the advantages that:

The present invention is modulated by subcarrier and motion demodulating algorithm, overcome the intrinsic direct current offset of tradition zero-intermediate-frequency architecture receiver and flicker noise theoretically, keep zero intermediate frequency reciver simple in construction, cheap while, have again traditional Low Medium Frequency framework receiver be short of image frequency suppression function.

The composite can be widely applied to the systems such as in-plant motion measurement, ranging and range rate, tracing and positioning, it is achieved the non-contact measurement of the physical quantity under different occasions.

Accompanying drawing explanation

Fig. 1 is the structured flowchart of hardware system of the present invention.

Detailed description of the invention

The present invention is further described below in conjunction with the accompanying drawings.

As shown in Figure 1, the present invention includes radio frequency transceiver chip, control module and clock generation module, clock generation module includes clock distribution block and crystal oscillator, radio frequency transceiver chip is connected with control module through analog-digital converter, one outfan of clock distribution block is connected with control module, and another outfan of clock distribution block is connected with radio frequency transceiver chip through low frequency bandpass filter；The transmitting terminal of radio frequency transceiver chip connects through power amplifier launches antenna, and the most filtered device of receiving terminal of radio frequency transceiver chip, low-noise amplifier connect reception antenna, and radio frequency transceiver integrated chip has phaselocked loop and frequency mixer.

Radio frequency transceiver chip produces two-way and generates subcarrier signal after chip internal is mixed with frequency synchronous sine continuous wave radiofrequency signal, the Low Frequency Sine Signals that a road and crystal oscillator produce, and exports, in order to target acquisition after power amplifier amplification；Another road sine continuous wave radiofrequency signal is as local oscillator.After radio frequency transceiver chip receives echo-signal, after low noise amplification, demodulation by filter, carry out lack sampling by A/D converter, be transferred to control module.Control module regulation is launched and the power of receiver module signal, and controls A/D converter collection signal, processes and is calculated object under test distance and relative displacement, shows the most in real time or be transferred to other terminals such as PC.

In being embodied as, control module can include signal processing and serial communication unit, control module is connected with transceiver chip, controls output continuous print subcarrier signal, is converted to analogue signal through A/D converter and is transmitted by serial communication unit after the echo-signal down coversion received.

A/D converter uses the A/D converter far below Nyquist sampling frequency.

The present invention is based on subcarrier modulation and motion demodulation method, dual band signal it is demodulated the most simultaneously and filters, need not as conventional superheterodyne structure utilizes down-conversion technique and high-speed high-performance analog/digital conversion technology that radiofrequency signal is converted into digital signal, simplified RF front-end circuit, cost-effective while improve the stability of system.

Embodiments of the invention are as follows:

As shown in Figure 1, embodiment is applied to, as a example by the doppler radar sensor based on subcarrier modulation of 802.11a/g frequency range (covering 2.4GHz to 2.5GHz and 4.9GHz to 5.875GHz full band range), introduce hardware configuration and motion demodulation method by one.Embodiment utilizes this Circuits System, can measure ohject displacement or the physical quantity such as life signal heart beating to be measured and breathing.The most all systems share a 6MHz sinusoidal clock to realize Phase synchronization, and are realized generation and the distribution of control signal by control module.

Transceiver chip selects the single chip radio frequency transceiver chip Max2829 of Maxim, realize all circuit such as the radio-frequency signal source required for radio-frequency receiving-transmitting function, receiver and frequency mixer, fully-integrated reception passage, sendaisle, VCO, frequency synthesizer and base band/control interface are provided, realize the significantly reduction of cost, and save space.Transmitting chain uses PLL PHASE-LOCKED LOOP PLL TECHNIQUE that to 5.86G ± 6MHz, the system clock frequency multiplication of 6MHz is carried out subcarrier modulation, and this subcarrier signal is launched through power amplifier.Power amplifier uses the AWL6951 chip of ANADIGICS company, this chip is a double frequency-band InGaPHBT power amplifier, support 2.4GHz Yu 5.8GHz two-band, footprints is little, only need two external capacitors, input and output have realized 50 ohm of couplings, it is not necessary to outside coupling, enormously simplify design.After reception link receives echo-signal, the BFCN-5750+ wave filter filtering clutter of Mini-Circuits company selected by radio-frequency filter, amplify entrance Max2829 chip through low-noise amplifier HMC320 and carry out down coversion demodulation, obtain the baseband signal of 6MHz, again after the SFSKA6M00CF ceramic filter of muRata company, the AD7357 A/D converter using AnalogDevice company carries out lack sampling, and sample frequency is 90Hz, and after sampling, baseband bandwidth is 30Hz.

Control module uses the STM32 low speed micro-control unit of ST Microelectronics, and the power of radiofrequency signal and the sample rate of A/D converter can be carried out accurately and effectively controlling by this micro-control module.

Below for embodiment, the generation of subcarrier signal and the step of motion demodulation method are expanded on further: consider that an initial phase is zero and low-frequency sine crystal oscillation signal cos (the 2 π f of amplitude normalization₁T), wherein t is the time, and π is pi, f₁Being crystal oscillator frequency, t is the time.Utilizing a frequency is f_LOThe radio-frequency carrier signal of amplitude normalization be mixed with it, the signal produced after mixing is subcarrier signal.This signal can be expressed as:

$\begin{array}{c}T\left(t\right)=cos\left(2{\mathrm{\πf}}_{1}t\right)*\[cos\left(2{\mathrm{\πf}}_{LO}t\right)-sin\left(2{\mathrm{\πf}}_{LO}t\right)\]=cos\left(2{\mathrm{\πf}}_{1}t\right)*\sqrt{2}cos(2{\mathrm{\πf}}_{LO}t+\frac{\mathrm{\π}}{4})\\ =\frac{\sqrt{2}}{2}\left\{\cos \[2\mathrm{\π}\left(f_{LO}+f_1\right)t+\frac{\mathrm{\π}}{4}\]+\cos \[2\mathrm{\π}\left(f_{LO}-f_1\right)t+\frac{\mathrm{\π}}{4}\]\right\}\end{array}---\left(1\right)$

From above-mentioned (1) formula, this signal can see that working frequency is respectively f_LO+f₁And f_LO-f₁The subcarrier signal that is formed by stacking of two-band sinusoidal signal.By this subcarrier signal from antenna emission detection target object, do not consider decay and amplification that signal transmits, according to Doppler's frequency principle receiver to echo-signal be represented by:

$\begin{array}{c}R\left(t\right)=\frac{\sqrt{2}}{2}\left\{\cos \[2\mathrm{\π}\left(f_{LO}+f_1\right)t-\frac{4{\mathrm{\πd}}_0+x\left(t\right)}{{\mathrm{\λ}}_{high}}\]+\cos \[2\mathrm{\π}\left(f_{LO}-f_1\right)t-\frac{4{\mathrm{\πd}}_0+x\left(t\right)}{{\mathrm{\λ}}_{low}}\]\right\}\\ +a*\cos \[2\mathrm{\π}\left(f_{LO}-f_1\right)t\]+noise\end{array}---\left(2\right)$

Wherein, d0 is the initial position of target object, and x (t) is displacement or the change of other measured physical quantity of object of which movement.λ_highAnd λ_lowIt is respectively frequency f_LO+f₁And f_LO-f₁The wavelength corresponding to electromagnetic wave.A is the amplitude (the least) of image frequency position interference signal, and the size of a represents the order of severity of Image interference, and a is the biggest, and then Image interference is the most serious.Noise represents other the various noises including flicker noise, and c is the light velocity.

From above-mentioned (2) formula, movable information x (t) of object is included in the phase place of echo-signal, and is concurrently present among the phase information of the subcarrier signal of two frequency ranges, i.e. [4 π d₀+x(t)]/λ_highWith [4 π d₀+x(t)]/λ_low.If using the information of a frequency range, as used f_LO+f₁The phase information of frequency band, then the frequency in image interference is also f_LO-f₁, identical with another frequency band.Due to the amplitude (i.e. a in above formula) of image frequency frequency more much smaller than signal amplitude (one of percentage is following), after amplifier amplifies, as the image interference a*cos [2 π (f of small-signal_LO-f₁) t] be the equal of to be submerged in effective information, negligible in Practical Calculation, in terms of this respect, image interference has obtained effective suppression.

Use frequency is f_LOLocal oscillation signal carry out quadrature demodulation after to obtain frequency be f₁Baseband signal, f in an embodiment₁For 6MHz, after carrying out lack sampling with the analog-digital converter of sample frequency 90Hz, the baseband signal obtaining its I, Q two-way is respectively as follows:

$\begin{array}{c}{B}_I\left(t\right)=\frac{\sqrt{2}}{4}\{cos\[2{\mathrm{\πf}}_{2}t-\frac{4{\mathrm{\πd}}_0+x\left(t\right)}{{\mathrm{\λ}}_{high}}\]+cos\[2\mathrm{\π}(-f_2)t-\frac{4{\mathrm{\πd}}_0+x\left(t\right)}{{\mathrm{\λ}}_{low}}\]\}\\ +\frac{1}{2}a*\cos \[2\mathrm{\π}\left(-f_2\right)t+{\mathrm{\φ}}_{imag}\left(t\right)\]+noise\end{array}---\left(3\right)$

$\begin{array}{c}{B}_Q\left(t\right)=-\frac{\sqrt{2}}{4}\{\sin \[2{\mathrm{\πf}}_{2}t-\frac{4{\mathrm{\πd}}_0+x\left(t\right)}{{\mathrm{\λ}}_{high}}\]+\sin \[2\mathrm{\π}(-f_2)t-\frac{4{\mathrm{\πd}}_0+x\left(t\right)}{{\mathrm{\λ}}_{low}}\]\}\\ +\frac{1}{2}a*\sin \[2\mathrm{\π}\left(-f_2\right)t+{\mathrm{\φ}}_{imag}\left(t\right)\]+noise\end{array}---\left(4\right)$

Wherein f₂For 30Hz.

Finally according to the phase contrast of two frequency bands, calculate object distance and relative displacement by the formula of motion demodulation method, recover its movement locus.

Next motion demodulation method is specifically introduced according to formula: first carry out succinct low-pass filtering at numeric field and filter direct current biasing and the flicker noise of noise (noise) part in (3) (4) two formula, i.e. in (3) (4), deducted noise section.

Then IQ two paths of signals is carried out digital mixing again so that signal moves to direct current frequency range, now a*sin [2 the π (-f in image interference such as Q road₂) t] move on to direct current frequency range, obtain effective suppression.

Then, the echo-signal medium frequency using trigonometric function algorithm of negating to obtain receiving is f_LO+f₁And f_LO-f₁The respective phase information of double frequency electromagnetic wave respectively as follows:

φ₁(t)=(4 π d₀+x(t))/λ_high+2k₁π(5)

φ₂(t)=(4 π d₀+x(t))/λ_low+2k₂π(6)

Due to trigonometric function all with 2 π as cycle, and trigonometric function gained of negating is monodrome solution, therefore in above two formulas, and k₁, k₂Represent the compensation cycle number of first, second phase information, wherein k₁, k₂For known integer and unequal.Now due to d₀、λ_highAnd λ_lowThe most constant, the phase information (5) the most thus recovered and (6) obtain the track of target object motion and can be described by following formula:

$d_0+x\left(t\right)=\frac{1}{4\mathrm{\π}(1/{\mathrm{\λ}}_{high}-1/{\mathrm{\λ}}_{low})}\[\left({\mathrm{\φ}}_1\right(t)-{\mathrm{\φ}}_2(t\left)\right)-2\mathrm{\π}\left(k_1-k_2\right)\]=\frac{{\mathrm{\φ}}_1\left(t\right)-{\mathrm{\φ}}_2\left(t\right)}{4\mathrm{\π}(1/{\mathrm{\λ}}_{high}-1/{\mathrm{\λ}}_{low})}-\frac{(k_1-k_2)}{2(1/{\mathrm{\λ}}_{high}-1/{\mathrm{\λ}}_{low})}---\left(7\right)$

The Section 2 of formula (7) can bring certain fuzziness.According to k in mathematical theory₁And k₂Value different, the distance of object has unlimited positive integer value and these values mutually with λ_highλ_low/2(λ_low-λ_high) for being spaced, but only one of which value is actual value.After bringing wavelength analog value in the present embodiment into, λ can be spaced apart_highλ_low/2(λ_low-λ_high)=12 meter, this interval is quite big for closer object motion measurement, the most easily judges its actual distance.

Finally, measuring the scope of ambient As distance according to reality, such as actual target of measuring is within 12 meters or in the range of 12 meters to 24 meters, and be i.e. easy to get k₁And k₂Occurrence, therefore the distance (i.e. formula (7)) of object has unique real value.

As can be seen here, the technology of the present invention effect is the most prominent, continuous wave wireless measurement is carried out innovatively with subcarrier modulation, use low speed A/D converter (ADC) and low speed arithmetic center control and regulation process, the problem of suppression conventional superheterodyne structure image interference, and overcome the intrinsic direct current offset of Direct-conversion structure and flicker noise shortcoming by motion demodulation method, and simplify circuit structure, reduce circuit cost, especially can realize the non-contact measurement of physical quantity under different occasion.

Claims (10)

1. the continuous wave Doppler radar sensor of a subcarrier modulation, it is characterized in that: include radio frequency transceiver chip, control module and clock generation module, clock generation module includes clock distribution block and crystal oscillator, radio frequency transceiver chip is connected with control module through analog-digital converter, one outfan of clock distribution block is connected with control module, and another outfan of clock distribution block is connected with radio frequency transceiver chip through low frequency bandpass filter；The transmitting terminal of radio frequency transceiver chip connects through power amplifier launches antenna, and the most filtered device of receiving terminal of radio frequency transceiver chip, low-noise amplifier connect reception antenna.

The continuous wave Doppler radar sensor of a kind of subcarrier the most according to claim 1 modulation, it is characterised in that: described radio frequency transceiver integrated chip has phaselocked loop and frequency mixer.

The continuous wave Doppler radar sensor of a kind of subcarrier the most according to claim 1 modulation, it is characterized in that: the Low Frequency Sine Signals that described crystal oscillator produces is divided into two-way through clock distribution block: a road is sent to radio frequency transceiver chip in order to produce subcarrier signal, and another road is sent to control module and carries out digital demodulation；Radio frequency transceiver chip produces two-way with the synchronous sinusoidal continuous wave radio-frequency carrier signal of frequency: generates subcarrier signal after the Low Frequency Sine Signals mixing that a road and crystal oscillator produce, then exports after power amplifier amplifies, in order to target acquisition；Another road carries out down coversion demodulation as local oscillator for chip internal；Radio frequency transceiver chip receives echo-signal, carries out lack sampling by analog digital conversion again and be transferred to control module after low noise amplification, demodulation by filter.

The continuous wave Doppler radar sensor of a kind of subcarrier the most according to claim 1 modulation, it is characterized in that: the described crystal oscillator with radiofrequency signal mixing uses the frequency active crystal oscillator of sine wave far below carrier frequency, is preferably with less than the active crystal oscillator of sine wave of one of percent frequency carrier frequency.

The continuous wave Doppler radar sensor of a kind of subcarrier the most according to claim 1 modulation, it is characterised in that: described A/D converter uses and carries out lack sampling far below the sample frequency of nyquist frequency.

6. the motion demodulation method of the continuous wave of a subcarrier modulation, it is characterized in that including step in detail below: produced Low Frequency Sine Signals by crystal oscillator, two-way it is divided into after clock distribution, one tunnel is sent to radio frequency transceiver chip in order to produce subcarrier signal, and another road is sent to control module and carries out digital demodulation；

Radio frequency transceiver chip produces two-way with the synchronous sinusoidal continuous wave radio-frequency carrier signal of frequency, one tunnel carries out down coversion demodulation as local oscillator for chip internal, subcarrier signal is generated after the Low Frequency Sine Signals mixing that another road and crystal oscillator produce, then after power amplifier amplifies, output carries out target acquisition, after radio frequency transceiver chip reception target reflection echo-signal successively after low noise amplification, demodulation by filter, carry out lack sampling and be transferred to control module again；

Control module receives the echo-signal after Low Frequency Sine Signals and lack sampling, first at numeric field, the echo-signal after analog digital conversion is carried out succinct low-pass filtering, filter direct current biasing and flicker noise, then two signals carry out digital mixing demodulation, the signal frequency after mixing is made to reduce to zero-frequency, then trigonometric function of negating this signal obtains the phase information of object under test, distance and the relative displacement of object under test is calculated finally according to the phase meter between the echo-signal after Low Frequency Sine Signals and lack sampling, recover its movement locus, complete detection and motion demodulation.

The motion demodulation method of continuous wave of a kind of subcarrier the most according to claim 6 modulation, it is characterised in that: described use trigonometric function method of negating obtains the phase information of object under test and is specifically represented by below equation:

φ₁(t)=(4 π d₀+x(t))/λ_high+2k₁π

φ₂(t)=(4 π d₀+x(t))/λ_low+2k₂π

Wherein, k₁, k₂Represent the compensation cycle number of first, second phase information, k respectively₁, k₂For known integer and unequal, d₀For the initial position of target object, x (t) is displacement or the change of other measured physical quantity, the λ of object under test motion_highAnd λ_lowIt is respectively frequency f_LO+f₁And f_LO-f₁The wavelength corresponding to double frequency electromagnetic wave, f_LOFor the frequency of sinusoidal continuous wave radio-frequency carrier signal, f₁For the frequency of low-frequency sine crystal oscillation signal, φ₁(t) and φ₂T echo-signal medium frequency that () is respectively received is f_LO+f₁And f_LO-f₁The respective phase information of double frequency electromagnetic wave.

The motion demodulation method of the continuous wave of a kind of subcarrier the most according to claim 6 modulation, it is characterised in that: the movement locus of described object under test is calculated to describe by following formula and obtains:

$d_0+x\left(t\right)=\frac{1}{4\mathrm{\π}\left(1/{\mathrm{\λ}}_{high}-1/{\mathrm{\λ}}_{low}\right)}\[\left({\mathrm{\φ}}_1\left(t\right)-{\mathrm{\φ}}_2\left(t\right)\right)-2\mathrm{\π}\left(m-n\right)\]=\frac{{\mathrm{\φ}}_1\left(t\right)-{\mathrm{\φ}}_2\left(t\right)}{4\mathrm{\π}\left(1/{\mathrm{\λ}}_{high}-1/{\mathrm{\λ}}_{low}\right)}-\frac{\left(m-n\right)}{2\left(1/{\mathrm{\λ}}_{high}-1/{\mathrm{\λ}}_{low}\right)}$

Wherein, φ₁(t) and φ₂T () represents that the echo-signal medium frequency received is f respectively_LO+f₁And f_LO-f₂The respective phase information of double frequency electromagnetic wave.

The motion demodulation method of the continuous wave of a kind of subcarrier the most according to claim 6 modulation, it is characterised in that: described sinusoidal continuous wave radio-frequency carrier signal and Low Frequency Sine Signals are mixed with frequency and phase place phase add mode.

The motion demodulation method of the continuous wave of a kind of subcarrier the most according to claim 6 modulation, it is characterised in that: described lack sampling uses and carries out far below the sample frequency of nyquist frequency.