A kind of method of mixing feedback compensation raising signal source port power-performance based on the multidimensional digital-to-analogue
Technical field
The present invention relates to a kind of measuring technology, especially mix the method that feedback improves signal source port power-performance based on the multidimensional digital-to-analogue.
Background technology
Have in the instrument of signal generation and output at vector network analyzer, synthetic source, amplifier etc.; In order to guarantee the index of signal source output power, usually can use the automatic electric-level control technology, in the automatic electric-level control loop, utilize the software and hardware compensation to guarantee that output power is in claimed range; Because the signal source output power is unit with dBm generally speaking; And wave detector is exported in the automatic electric-level control loop detecting circuit and the non-linear relation of power, in order to obtain the The optimal compensation effect, often earlier detecting circuit being carried out logarithm amplifies; Voltage and power after logarithm amplifies are linear, compensate then.
The automatic electric-level control technology is widely used in signal source, communication transmitter and multiple surveying instrument.Because of originally experience reasons such as instability, the characteristic of external interference and electronic devices and components be undesirable of signal source; Make signal source be difficult to the stable signal of output amplitude; And need be provided with automatically signal amplitude according to actual conditions sometimes, at this moment will adopt the automatic electric-level control technology to achieve the above object.The automatic electric-level control technology is in system, to adopt feedback loop that signal amplitude is automatically adjusted, and makes the signal of amplitude scintillation become more steady, and can be provided with arbitrarily signal amplitude within the specific limits.The quality of automatic electric-level control performance is directly connected to accuracy, degree of stability, flatness and the out-put dynamic range etc. of signal source power.
Basic functional principle based on the automatic electric-level control technology of the linear calibration method of power is: the power DAC value needs that come by CPU convert corresponding mimic channel to corresponding D/A change-over circuit, and send into the V/A circuit.The digital detection signal of wave detector output carries out logarithm through logarithmic amplifier and amplifies, and through further anti-phase; And another road main road detection output electric current and the former electric current behind logarithmic amplifier is superimposed jointly; And further be sent to integration, amplifying circuit; The signal one tunnel of output directly passes through the modulation signal 2 of reverse back conduct as the modulation signal 1, a tunnel of modulator.Modulator according to the size of modulation signal 1 and modulation signal 2 control the internal fet source leak between the variation of impedance, regulate the watt level of output signal with this.It mainly is corresponding with the power of representing with the dBm form in order to make logarithm amplify output voltage adopting the logarithm amplifying circuit, and rectified signal is carried out log-compressed, controls the scope of accessible signal to increase automatic electric-level.Because present the square law characteristic as the diode of wave detector core component when the small-signal detection, promptly output voltage is directly proportional with power input; Be linear characteristic during large-signal, promptly output voltage is directly proportional with the square root of power input.
Adopt the automatic electric-level control technology of the linear calibration method of power; Be to improve the power linearity through generation calibration constants after three different on Frequency point power points being carried out the power linear gauging; And the prerequisite of doing like this is to think to be that DAC value and voltage in oblique section of boundary is linear with these three power, thereby calculate corresponding slope and skew according to calibration constants.
In the automatic electric-level control technology based on the linear calibration method of power, after carrying out the power linear gauging, can produce calibration constants and improve the power linearity, calibration constants deposits in the corresponding memory.After complete machine is provided with power; Call corresponding calibration constants according to watt level; Produce corresponding D AC value, get into together through the detecting circuit of D/A change-over circuit and real output signal that logarithm amplifies, comparator circuit, generation two-way modulation voltage after integration, amplification; Be sent to the modulator in the switch frequency multiplication amplifier module, thereby realize the automatic control of power level.Owing in the linear calibration process of power, just measure to three power points, carry out the calculating of respective alignment constant then, then think approximately linear at a certain section.Therefore, with these 3 be the boundary, think that DAC value and voltage are linear in oblique section, and calculate corresponding slope and skew according to them.Thereby draw DAC value corresponding when on certain fixed frequency point, being set to different capacity.And for various reasons, in the whole frequency range of complete machine work, generally only choosing several points carries out such power linear gauging.And are the calibration constants according to these several points at other Frequency points, through what calculate.
In addition, because various reasons such as the instability of electronic devices and components, ambient temperature variation cause the instability of signal source output power, adopt the linear calibration steps of power also can't revise.Therefore, in some practical application, be difficult to satisfy the needs of on-the-spot test, be unfavorable for interior applying on a large scale.
Summary of the invention
To above-mentioned shortcoming, the present invention provides a kind of and mixes the method that feedback compensation improves signal source port power-performance based on the multidimensional digital-to-analogue.
One of the object of the invention is realized through following technical scheme:
Automatic electric-level control based on multidimensional Digital Analog Hybrid Circuits and multichannel feedback compensation calibration method; Mainly form, and can increase and decrease the corresponding compensation circuit module according to actual needs by the digital circuit and the mimic channel of modules such as logarithm amplifying circuit, temperature-compensation circuit, main power DAC circuit, slope off-centre circuit, slope equalizer.Ultimate principle is signal source is exported certain power under the control of modulator a signal, and rectified signal is input to the logarithm amplifying circuit together with the detection shifted signal.It mainly is corresponding with the power of representing with the dBm form in order to make logarithm amplify output voltage adopting the logarithm amplifying circuit, and rectified signal is carried out log-compressed, controls the scope of accessible signal to increase automatic electric-level.Because present the square law characteristic as the diode of wave detector core component when the small-signal detection, promptly output voltage is directly proportional with power input; It during large-signal linear characteristic; Be that output voltage is directly proportional with the square root (voltage) of power input; Realize Linear Control to signal power; Make the power index of output signal in whole dynamic range, evenly distribute, need in the logarithm amplifying circuit, introduce square law linear compensation signal and detection migration signal, make the detection in different qualities zone after this logarithm amplifies adjustment, be the identical voltage signal of slope.
The digital circuit part is at the different frequency point; The DAC value that respectively compensating circuit settings such as main power DAC, slope skew, detection skew, logarithm skew, square law linearity is met the demands; Through corresponding D/A change-over circuit, convert the output of corresponding simulating voltage to.Wherein, logarithm amplification artificial circuit part is the emphasis of this multi-channel compensating system circuit.
Purpose to number conversion is that the output voltage of wave detector is changed, and makes voltage and input radio frequency power (is unit with dBm) after the conversion linear.Used here logarithm amplifying circuit is a diclinic logarithm amplifying circuit, mainly operational amplifier and two pipe and peripheral circuit thereof is made up of.
Main power DAC signal is the signal that is used for the signalization source power that primary control program produces after digital-to-analog conversion; This signal and logarithm amplify output, temperature compensation, slope skew, slope-compensation and superpose, and this signal and compare with another road input of integrator is not when the two voltage waits; The output voltage of integrator changes; Thereby the damping capacity of control modulator make the output power of signal source change, and the variation of output power can cause the variation of rectified signal; So cycle control; When another input terminal voltage of superposed signal and integrator equated, integrator reached steady state (SS), made the signal source output power finally be stabilized on the power of requirement.
In addition, adopted preparatory fixed ampllitude technology among the present invention, promptly when power changes, preset a damping capacity through D/A to modulator, the automatic electric-level control loop only need carry out adjusting among a small circle, to accelerate the control to output signal power.
Utilization is based on the automatic electric-level control technology of multidimensional Digital Analog Hybrid Circuits and the realization of multichannel feedback compensation calibration method; Have broadband, great dynamic range, characteristics such as simple and practical; And can be applied to because of originally experience reasons such as instability, the characteristic of external interference and electronic devices and components be undesirable of signal source; Make signal source be difficult to the output amplitude situation of signal stably; Adopt feedback loop and signal amplitude is automatically adjusted, make the signal of amplitude scintillation become more steady, and can be provided with arbitrarily signal amplitude within the specific limits according to actual conditions.And can several multi-channel compensating system circuit be carried out cascade according to actual conditions, further improve flatness, accuracy, degree of stability, the linearity and the dynamic range of port output power.
This method compensates the detecting circuit of wave detector output through necessary software and hardware, the signal after handling is used for controlling the damping capacity of modulator, thereby reaches the purpose of conditioning signal output power real-time.And, make its extensibility on software and hardware good because this method has adopted preparatory fixed amplitude circuit, and flexible configuration, basis is own required easily to utilize this method user, and the signal that will compensate inserts the corresponding compensation circuit.
Owing in this method temperature compensation is arranged, so the temperature stability of the output power of signal source is all less with drift.
Description of drawings
Below in conjunction with accompanying drawing specific embodiment of the present invention is done further detailed explanation.
Fig. 1 is based on the automatic electric-level control main circuit block diagram of the linear calibration method of power;
Fig. 2 is based on the ultimate principle block diagram of the automatic electric-level control of multidimensional Digital Analog Hybrid Circuits and multichannel feedback compensation calibration method;
Fig. 3 amplifies the theory diagram of compensated part based on logarithm in multidimensional Digital Analog Hybrid Circuits and the multichannel feedback compensation calibration method
Embodiment
Below will combine accompanying drawing, the preferred embodiments of the present invention will be carried out detailed description; Should be appreciated that preferred embodiment has been merely explanation the present invention, rather than in order to limit protection scope of the present invention.
Mix the method that feedback improves signal source port power-performance based on the multidimensional digital-to-analogue, the ultimate principle of this method is to adopt multidimensional Digital Analog Hybrid Circuits and multichannel feedback compensation calibration method to improve the performances such as flatness, accuracy, degree of stability, the linearity and dynamic range of signal source port output power.
This method is made up of the digital circuit and the mimic channel of modules such as logarithm amplifying circuit, temperature-compensation circuit, main power DAC circuit, slope off-centre circuit, slope equalizer, and can increase and decrease the corresponding compensation circuit module according to actual needs.Ultimate principle is signal source is exported certain power under the control of modulator a signal, and rectified signal is input to the logarithm amplifying circuit together with the detection shifted signal.It mainly is corresponding with the power of representing with the dBm form in order to make logarithm amplify output voltage adopting the logarithm amplifying circuit, and rectified signal is carried out log-compressed, controls the scope of accessible signal to increase automatic electric-level.Because present the square law characteristic as the diode of wave detector core component when the small-signal detection, promptly output voltage is directly proportional with power input; It during large-signal linear characteristic; Be that output voltage is directly proportional with the square root (voltage) of power input; Realize Linear Control to signal power; Make the power index of output signal in whole dynamic range, evenly distribute, need in the logarithm amplifying circuit, introduce square law linear compensation signal and detection migration signal, make the detection in different qualities zone after this logarithm amplifies adjustment, be the identical voltage signal of slope.
The digital circuit part is at the different frequency point; The DAC value that respectively compensating circuit settings such as main power DAC, slope skew, detection skew, logarithm skew, square law linearity is met the demands; Through corresponding D/A change-over circuit, convert the output of corresponding simulating voltage to.Wherein, logarithm amplification artificial circuit part is the emphasis of this multi-channel compensating system circuit.
Purpose to number conversion is that the output voltage of wave detector is changed, and makes voltage and input radio frequency power (is unit with dBm) after the conversion linear.Used here logarithm amplifying circuit is a diclinic logarithm amplifying circuit, mainly operational amplifier and two pipe and peripheral circuit thereof is made up of.
Main power DAC signal is the signal that is used for the signalization source power that primary control program produces after digital-to-analog conversion; This signal and logarithm amplify output, temperature compensation, slope skew, slope-compensation and superpose, and this signal and compare with another road input of integrator is not when the two voltage waits; The output voltage of integrator changes; Thereby the damping capacity of control modulator make the output power of signal source change, and the variation of output power can cause the variation of rectified signal; So cycle control; When another input terminal voltage of superposed signal and integrator equated, integrator reached steady state (SS), made the signal source output power finally be stabilized on the power of requirement.
In addition, adopted preparatory fixed ampllitude technology among the present invention, promptly when power changes, preset a damping capacity through D/A to modulator, the automatic electric-level control loop only need carry out adjusting among a small circle, to accelerate the control to output signal power.
Fig. 3 is the theory diagram that amplifies compensated part based on logarithm in multidimensional Digital Analog Hybrid Circuits and the multichannel feedback compensation calibration method.Wherein, V
INBe the wave detector output voltage, constant current source I
B1And I
B2Approximately equal is that infinitely-great characteristic can obtain triode Q according to operational amplifier input impedance
1ACollector current I
1Ac=I
IN=V
IN/ R
IN(1).
Characteristic according to triode:
I
C=-αI
E=-αI
ES[exp(qV
eb/kT-1)]=-αI
ES[exp(V
eb/V
T)-1](2)
Wherein: I
ESEmitter current for base stage and collector short circuit; α is the amplification coefficient of common base DC current;
K=1.38 * 10
-23J/K, Boltzmann constant; Q=1.6 * 10
-19C is the charged value in electron institute; T is absolute temperature (unit K °), V
TBe the temperature voltage equivalent, under normal temperature (300K °) situation, V
T=26mV;
Because Q
L4Base earth, and can get according to formula (2)
V
IAe=V
IAeb+V
IAb=V
IAeb+0=V
IAeb
=V
Tln[-I
IAc/(α
1A*I
ES-1A)+1]=V
Tln[-I
IN/(α
1A*I
ES-LA)+1](3)
And triode Q
2ADo diode usefulness, the electric current of flowing through is:
I
2Ac=I
1Ae+I
B1≈I
1Ac+I
B1=I
LN+I
B1
Because triode Q
2ABase stage and triode Q
1AEmitter links to each other, and can obtain according to formula (2) and (3):
V
2Ae=V
2Aeb+V
2Ab=V
2Aeb+V
IAe
=V
Tln[-I
2Ac/(α
2A*I
ES-2A)+1]+V
T1n[-I
IN/(α
1A*I
ES-1A)+1]
≈V
T1n[-(I
IN+I
B1)/(α
2A*I
ES-2A)+1]+V
Tln[-I
IN/(α
1A*I
ES-LA)+1](4)
During miniwatt, I
IN<<I
B1, I
IN+ I
B1≈ I
B1, wave detector is operated in " square law district ", V
IN∝ P
MW,
V
2Ae≈V
Tln[-I
B1/(α
2A*I
ES-2A)+1]+V
Tln[-I
IN/(α
1A*I
ES-LA)+1]
∝V
Tln(I
IN)∝V
Tln(P
mW) (5)
When high-power, I
IN>>I
B1, I
IN+ I
B1≈ I
IN, wave detector is operated in " linear zone ",
V
2Ae≈V
Tln[-I
IN/(α
2A*I
ES-2A)+1]+V
Tln[-I
IN/(α
1A*I
ES-LA)+1]
∝V
Tln(I
IN)+V
Tln(I
IN)∝V
Tln(P
mW) (6)
Because, P
DBm=20logP
MW, Q
1BWith Q
2BAs diode usefulness, and current constant is constant, and tube voltage drop is invariable, no matter therefore miniwatt or high-power, the output voltage of detecting circuit after logarithm amplifies is directly proportional with power (is unit with dBm) all the time:
V
OUTT∝V
2Ae∝V
Tln(P
mW)∝V
TP
dBm (7)。