Background technique
In actual operation, it is often necessary to detect the phase difference between two signals, this is also research network phase-frequency characteristic
In indispensable importance.In certain fields, the phase difference accurately measured between two signals has critically important meaning
Justice, such as: in electrical instrument, the synchronous data processing and Experiment of Electrical Engineering detected, it is often necessary to measure two column homogenous frequency signals
Phase difference.But there are many defects for traditional phase tester, and the frequency range such as its work is narrow, can only generally measure low frequency or in
Frequency signal, the precision of measurement be not also high.
Integrated phase discriminator AD8302 is the release in 2001 of ADI company of the U.S. for RF/IF (radio frequency/
Intermediate frequency) amplitude and phase measurement first monolithic die, mainly examined by wideband phase
Wave device, two wide band logarithmic wave detectors, a bias unit, output amplifier group and output reference voltage (1.8V) buffering
The part such as device forms.
The phase Difference Measuring System constructed using integrated phase discriminator AD8302 can be measured to degree of precision two and independent be penetrated
Frequently the phase difference of (RF), intermediate frequency (IF) signal, the frequency of measured signal can be up to 2.7GHz.
The equation of integrated phase discriminator AD8302 measurement phase difference is as follows:
Vphs=VΦ(Φ(V1)-Φ(V2)) formula (1)
In formula, V1And V2Respectively two-way input signal amplitude (unit is millivolt), Φ (V1) and Φ (V2) it is respectively two-way
Input signal phase (unit degree of being), VΦFor the phase response characteristic slope of curve (unit is millivolt/degree), VphsFor phase bit comparison
It exports (unit is millivolt).
By formula (1) it is found that the output voltage of integrated phase discriminator AD8302 is divided by VΦIt can be obtained by two input signals
Phase difference.
The integrated ideal resonse characteristic of phase discriminator AD8302 is as shown in Figure 1.
But when in a practical situation, carrying out phase difference measurement using integrated phase discriminator AD8302, actual phase response is special
Linearity curve as shown in Fig. 2, its there are following some problems:
(1) nonlinear area problem: phase when near 0 ° ,+180 ° and -180 °, deposit by phase response characteristic curve
Serious non-linear, as shown in Fig. 3 encircled, the transaxial width of inelastic region is about 40 °, if not to nonlinear area
Phase difference value make specially treated, then the measurement error of this region phase value can be bigger.
(2) two-value problem: the measurement range of integrated phase discriminator AD8302 is 0 °~+180 ° and 0 °~-180 °, by integrating
The ideal phase response characteristic curve of phase discriminator AD8302 is it can be found that the same voltage value corresponds to two phase differences, just
It is negative for one positive one, singly it cannot differentiate that its is positive and negative from output voltage, so measurement range can not be expanded to 0 °~360 °.
(3) problem of inconsistency: integrating phase discriminator AD8302 to multi-disc and test, and finds per a piece of integrated phase discriminator
Actual phase resonse characteristic all having differences property of AD8302, the slope for showing as curve of output is different, if using same
Set coefficient will be unable to obtain compared with high measurement accuracy, it is therefore desirable to calibrate, can obtain more quasi- to every suit measuring circuit
True slope value.
Summary of the invention
To solve the deficiencies in the prior art, the purpose of the present invention is to provide a kind of height based on integrated phase discriminator AD8302
Accurate phase detection circuit and its method for self-calibrating, wherein the phase detecting circuit can effectively solve the problem that phase response characteristic song
The nonlinear area problem and two-value problem of line, can in 0MHz~60MHz frequency range 0 °~360 ° phases of precise measurement
Potential difference, method for self-calibrating can effectively solve the problem that problem of inconsistency, greatly reduce the workload of actual measurement circuit debugging, from
And automatic measurement level can be improved.
In order to achieve the above objectives, the present invention adopts the following technical scheme that:
High-precision phase position detection circuit based on integrated phase discriminator AD8302, comprising: integrated phase discriminator AD8302, aforementioned collection
Two paths of signals input channel is connected at the input terminal of phase discriminator AD8302, which is characterized in that wherein any signal all the way inputs
On channel installation is there are two radio-frequency relay, and both of the aforesaid radio-frequency relay can carry out ledger line and ledger line two states are not cut
Change, integrated under ledger line and not ledger line two states phase discriminator AD8302 output valve at least one be in phase response characteristic bent
The length L of the linear region of line, jumper line is calculated by the following formula to obtain:
In formula, v is spread speed of the signal in cable, and f is frequencies of propagation of the signal in cable, and △ φ is to add
The phase difference that long cable introduces, the size of △ φ is by integrating the inelastic region of the phase response characteristic curve of phase discriminator AD8302
Transaxial width determine.
High-precision phase position detection circuit above-mentioned based on integrated phase discriminator AD8302, which is characterized in that aforementioned integrated mirror
The actual phase resonse characteristic of phase device AD8302 are as follows:
In formula, U is the voltage of integrated phase discriminator AD8302 output,For the corresponding phase of voltage U, f is signal in cable
Frequencies of propagation in line, k1、k2It is undetermined coefficient with b, is determined by self calibration.
High-precision phase position detection circuit above-mentioned based on integrated phase discriminator AD8302, which is characterized in that method for self-calibrating
The following steps are included:
(1) two calibrations are respectively connected to the 1st tunnel input signal port and the 2nd tunnel input signal port with cable;
(2) same-phase signal source is accessed to the other end of calibrated cable, changes the frequency of input signal, then records number
According to (fi, Ui,), wherein fiFor the frequency of signal source, UiTo integrate the voltage that phase discriminator AD8302 is exported,For calibration
With cable in fiPhase difference under frequency;
(3) the 6 of the left side linear region for being evenly distributed on phase response characteristic curve are chosen from the data of test record
Group data, go out the k in formula (6) using least square method the Fitting Calculation11、k21And b1, wherein the expression formula of formula (6) is as follows:
(4) the 6 of the right linear region for being evenly distributed on phase response characteristic curve are chosen from the data of test record
Group data, go out the k in formula (7) using least square method the Fitting Calculation12、k22And b2, wherein the expression formula of formula (7) is as follows:
The invention has the beneficial effects that:
(1) phase detecting circuit:
By adding prolonging for specific length to signal on any signal input channel all the way in two paths of signals input channel
Slow cable changes phase difference when two paths of signals reaches integrated phase discriminator AD8302, so that former phase difference is skipped phase and rings
Characteristic inelastic region is answered, solves the problems, such as nonlinear area, and former phase difference can be determined and be in output characteristics
The left area of curve or right half area, so as to make its measurement range be transformed into and can be surveyed by 0 °~+180 ° and 0 °~-180 °
0 °~360 °, solves the problems, such as two-value.
(2) method for self-calibrating:
Data acquisition and matched curve are all integrated into program, is solved using least square method and obtains actual phase
Resonse characteristic not only improves measurement accuracy, but also reduces workload, while also reducing circuit design difficulty.
Specific embodiment
Specific introduce is made to the present invention below in conjunction with the drawings and specific embodiments.
One, phase detecting circuit
Referring to Fig. 3, the high-precision phase position detection circuit of the invention based on integrated phase discriminator AD8302 includes: integrated phase demodulation
Device AD8302, the input terminal of the integrated phase discriminator AD8302 are connected with two paths of signals input channel and (it is defeated to be denoted as the 1st road signal respectively
Enter channel, the 2nd road signal input channel), any signal input channel (the present embodiment all the way in the two paths of signals input channel
In be the 1st road signal input channel) on installation (be denoted as radio-frequency relay A and radio-frequency relay respectively there are two radio-frequency relay
B), radio-frequency relay A and radio-frequency relay B can carry out ledger line and the not switching of ledger line two states, ledger line and not ledger line two
Integrated under kind of state phase discriminator AD8302 output valve at least one be in the linear region of phase response characteristic curve.
According to physics knowledge, when signal is propagated in cable, the relationship of spread speed v and wavelength X and frequency f
Are as follows:
V=λ f formula (2)
The phase change that the length of jumper line introduces are as follows:
According to the calculation formula of formula (2) and the length L of the available jumper line of formula (3):
In formula (4), v is spread speed (unit m/s) of the signal in cable, and f is biography of the signal in cable
It broadcasts frequency (unit Hz), △ φ is the phase difference that jumper line introduces (unit is degree).
The size of △ φ is true by the transaxial width for integrating the inelastic region of the phase response characteristic curve of phase discriminator AD8302
Fixed, since the transaxial width of inelastic region is about 40 °, rule of thumb the value range of △ φ is 40 °~120 ° more appropriate, examples
Such as take φ=120 ° △, signal frequency f=30Mhz, v=3.0 × 108M/s can calculate to obtain L=3.3m using formula (4).
We are by adding specific length to signal on any signal input channel all the way in two paths of signals input channel
Delay cable, change phase difference when two paths of signals reaches integrated phase discriminator AD8302, former phase difference enable to skip phase
The inelastic region of position resonse characteristic, and former phase difference can be determined and be in the left area of output characteristic curve still
Right half area can survey 0 °~360 ° so as to be transformed into its measurement range by 0 °~+180 ° and 0 °~-180 °.
It is specific as follows:
(1) for nonlinear area problem:
If phase to be measured is almost fallen in the inelastic region of the lower-left Fig. 2, after increasing cable (length L), phase difference
It will increase, point will move up, and leave inelastic region;
If phase to be measured is almost fallen in the inelastic region on the top Fig. 2, after increasing cable (length L), point will
It moves down or first moves still further below upwards, leave inelastic region;
If phase to be measured is almost fallen in the inelastic region of the bottom right Fig. 2, after increasing cable (length L), phase difference
It will increase, point will be moved down first, be then jumped in the inelastic region of the lower-left Fig. 2, then be moved up, and inelastic region is left.
So, as long as the length L of increased cable is suitable, which inelastic region don't-care point falls in, and can jump out
Inelastic region measures exact value.
(2) for two-value problem:
After increasing cable, if phase almost moves up, put just in 0 °~-180 ° sections, if phase
It almost moves down, then putting just in 0 °~+180 ° sections.
So, with regard to solving the problems, such as two-value, so as to measure 0 °~360 ° phase differences.
After increasing cable, if phase almost falls in inelastic region, subtracted with the phase difference measured after ledger line increased
The introduced phase difference of cable, using this difference as the phase difference measurement between input signal;If phase is not fallen within almost
Inelastic region, then phase difference before using ledger line is as the phase difference measured value between input signal.
It can be seen that phase detecting circuit of the invention is effectively solved by ledger line and the not switching of ledger line two states
The nonlinear area problem and two-value problem of phase response characteristic curve, so as in 0MHz~60MHz frequency range
0 °~360 ° phase differences of interior precise measurement.
Two, method for self-calibrating
Phase discriminator AD8302 is integrated to multi-disc to test, it is found that the output characteristics per a piece of integrated phase discriminator AD8302 is bent
Line all having differences property show that the slope of output characteristic curve is different.This inconsistency shows each to integrate phase discriminator
The phase response characteristic curve of AD8302 be it is different, theoretical phase response characteristic curve can not be directlyed adopt.According to
The method fit phase resonse characteristic that manual testing calculates, will expend a large amount of manpower and time.
In addition, need in phase Difference Measuring System to each phase detecting circuit progress ledger line, and increased cable
Per se with absolute error, this part absolute error is eventually transferred on the phase difference measured by us.
Therefore, we devise the method for self-calibrating of phase detecting circuit, and data acquisition and matched curve are fully integrated
Into program, actual phase response characteristic curve is solved using least square method, allows to be used at any time to calculate phase
The phase response characteristic curve of potential difference is adjusted to best.
The main thought of method for self-calibrating of the invention is: changing the phase difference relationship of two-way input signal, rings in phase
Characteristic linear region is answered to obtain 12 groups of frequency input signals and corresponding integrated phase discriminator AD8302 output voltage data,
Least square method is used to carry out linear fit to obtain the actual phase response characteristic curve of integrated phase discriminator AD8302.
Method for self-calibrating of the invention is described in detail below.
By analysis it is found that integrating phase discriminator AD8302 in Fig. 3 to test the phase difference output of circuit includes following sections:
(1) theoretical value of two cables phase difference to be measured;
(2) Fig. 3 tests circuit and introduces error related with frequency;
(3) error unrelated with pull-in frequency.
Therefore actual phase resonse characteristic can indicate are as follows:
In formula (5):
U is the voltage of integrated phase discriminator AD8302 output;
For the corresponding phase of voltage U;
k2F indicates the error for a variety of and frequency dependence that measuring system is introduced, and specifically includes: the absolute error of delay line,
The error of the not identical introducing of the transmission path of two input signals on circuit boards;
B is the constant term unrelated with signal frequency.
k1、k2It is undetermined coefficient with b, can be determined by self calibration.
It is learnt from Fig. 2, phase response characteristic curve has two sections of left and right, so corresponding, there are two equations:
Formula (6) and formula (7) respectively indicate left section of phase response characteristic curve and right section of phase response characteristic curve.U
It is known quantity, k with f11、k21、b1、k12、k22And b2For unknown quantity (can by least square method be fitted calculate, behind illustrate).
Step 1
By two calibrations, with cable, (every phase has been measured by High-precision Vector Network Analyzer, it is believed that is true
Value) it is respectively connected to the 1st tunnel input signal port and the 2nd tunnel input signal port.
Step 2
Same-phase signal source is accessed to the other end of calibrated cable, changes the frequency of input signal, records data (fi,
Ui,), wherein fiFor the frequency of signal source, UiTo integrate the voltage that phase discriminator AD8302 is exported,For calibrated cable
In fiPhase difference (being measured by High-precision Vector Network Analyzer) under frequency.
Step 3
6 groups of numbers for being evenly distributed on the left side linear region of phase response characteristic curve are chosen from the data of test record
According to going out the k in formula (6) using least square method the Fitting Calculation11、k21And b1。
Step 4
6 groups of numbers for being evenly distributed on the right linear region of phase response characteristic curve are chosen from the data of test record
According to going out the k in formula (7) using least square method the Fitting Calculation12、k22And b2。
In this way, we have obtained the actual phase resonse characteristic expression formula of integrated phase discriminator AD8302.
Method for self-calibrating of the invention has the advantages that
(1) measurement accuracy is high
Due to being fitted using measurement data and reasonable comprehensive rational formula to phase response characteristic curve, examine simultaneously
All error patterns of hardware system bring are considered, so that measurement accuracy improves.
(2) workload is few
Existing measurement method is very sensitive to the variation of condition, once input signal variation is greatly, will do a large amount of experiment
Test, but these work can all be simplified, automate using method for self-calibrating of the invention, the workload of people subtracts significantly
Few, the effect of people is weakened, and service efficiency increases, and the time is greatly saved.
(3) circuit design difficulty reduces
Requirement in circuit design to the cabling of two input signals reduces, it is not necessary to it is required that the circuit of two-way input signal is walked
Line is just the same.
Three, it applies
Phase detecting circuit based on integrated phase discriminator AD8302 of the invention, be successfully applied to frequency be 3MHz~
Phase difference measurement between signal within the scope of 30MHz, measurement range are 0 °~360 °, and most of measuring result error is within 0.5 °.
To measure the phase difference of more broadband signal, part change only need to be carried out on hardware circuit, software section is several
It can be multiplexed completely.
To measure the phase difference between more radiofrequency signals, it is only necessary to replicate hardware module.
In conclusion the phase detecting circuit of the invention based on integrated phase discriminator AD8302, favorable expandability, multiplexing effect
Rate is high, and measurement accuracy is high, and method for self-calibrating is reliable and practical.
It should be noted that the above embodiments do not limit the invention in any form, it is all to use equivalent replacement or equivalent change
The mode changed technical solution obtained, falls within the scope of protection of the present invention.