CN109995344A - A kind of numerical control attenuation circuit and its adjusting method - Google Patents
A kind of numerical control attenuation circuit and its adjusting method Download PDFInfo
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- CN109995344A CN109995344A CN201910387366.1A CN201910387366A CN109995344A CN 109995344 A CN109995344 A CN 109995344A CN 201910387366 A CN201910387366 A CN 201910387366A CN 109995344 A CN109995344 A CN 109995344A
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- H—ELECTRICITY
- H03—ELECTRONIC CIRCUITRY
- H03H—IMPEDANCE NETWORKS, e.g. RESONANT CIRCUITS; RESONATORS
- H03H11/00—Networks using active elements
- H03H11/02—Multiple-port networks
- H03H11/24—Frequency-independent attenuators
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
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- Y02D30/00—Reducing energy consumption in communication networks
- Y02D30/70—Reducing energy consumption in communication networks in wireless communication networks
Abstract
The present invention is a kind of numerical control attenuation circuit and its adjusting method.The main attenuator circuit of this numerical control attenuation circuit is concatenated first, second master fader, there are also the first and second decaying trimming circuits for including multiple triodes and resistance, the base stage of each triode is connect through resistance with decoding control circuit, the analog signal output of the fine-tuned resistance connection first or second master fader of collector.It selects that semifixed resistor is suitble to finely tune the pad value of circuit, improves the precision of decaying stepping.The adjusting method of this numerical control attenuation circuit is that the output of main attenuator circuit terminates vector network analyzer, first disconnect decaying trimming circuit, attenuation, the attenuated error of winner's attenuator circuit at this time are detected, the semifixed resistor value of decaying trimming circuit needed for supplementing this error is calculated as.The present invention improves the stepping attenuation accuracy of the attenuator of 2 pieces of chips concatenation, reaches 0.2dB.And the composite design of dual chip and decaying trimming circuit network, it is easy to accomplish, it can easily be accommodated.
Description
Technical field
The present invention relates to the amplitude adjusted technology of analog signal, specially a kind of numerical control attenuation circuit and its adjusting method.
Background technique
The original existing signal of nature is all analog signal, such as sound, image, brightness, radio wave, these simulations
Signal radio subscriber using when largely need to change its amplitude.Low, analog intermediate frequency signal amplitude control field, it is common
Application includes short wave radio signals, radar intermediate frequency signal and other low, Mid Frequency analog signals.These signals exist
Using when be required to the adjusting of carry out amplitude size, meet the signaling interface requirement of circuit thereafter.
The amplitude adjusted of analog signal is broadly divided into mechanical adjustment and electrical adjustment two ways.Mechanical adjustment mode is logical
Mechanical force is crossed on variable resistance, changing variable resistance, intrinsic standoff ratio realizes that signal amplitude changes in circuit, such as
The volume knob for rotating radio-tape recorder changes output musical sound size.Electrical adjustment mode is using in electric signal control circuit
Electronic component parameter change signal amplitude size.Electrical adjustment mode is divided into analog control mode and digital control approach again.Mould
The control signal of quasi- control mode is analog electrical signal, and analog electrical signal voltage is consecutive variations, the decaying of analog attenuator
Value is also consecutive variations.Digital control scheme is then to utilize " 0 " and " 1 " two kinds of digital level control attenuator attenuations, attenuation
Be it is discrete discontinuous, digital control scheme provides great convenience for remote control.
Currently used numerical-control attenuator is classified by control data bits, mainly there is 1~6bit, numerical-control attenuator
The step number that decays is 21~26；Classify by decaying stepping (dB) size, there are commonly 0.125,0.25,0.5,1.0,
2.0,3.0,6.0 etc.；Classify by numerical control attenuation range (dB), there are commonly 0~3,0~6 ... 0~31.5 etc..
There are two main classes for currently marketed numerical-control attenuator device, and one kind is amplitude fading stepping small (0.125dB) essence
High (0.1dB) is spent, but total attenuation range is small；It is another kind of for big (such as 3dB) precision of decaying stepping it is low (0.5dB), but complete attenuation model
It encloses big.
What numerical-control attenuator single-chip devices numerical control amplitude fading range was big currently on the market has 0~-31.5dB, decaying step
Into for 0.25dB (or 0.5dB)；Multi-chip combination product (the decaying chip that two panels attenuation is 0~-31.5dB concatenates) amplitude
For attenuation range up to 0~-63dB, decaying stepping is 0.25dB.Discovery is measured to these products, in 0~-63dB attenuation range
It is interior, do not ensure that each stepping attenuation accuracy reaches 0.25dB.When attenuation is smaller, attenuation accuracy is able to satisfy index and wants
It asks, but attenuation accuracy becomes very poor when attenuation is big, attenuated error maximum reaches 0.6dB, and main cause is the shadows such as circuit noise
It rings.Usual numerical-control attenuator nominal signal input range is 0dBm, and when attenuation is big, (such as -60dB), signal exports after decaying
Amplitude is too small (- 60dBm), and signal is influenced by circuit noise interference and signal cross-talk it is obvious that circuit noise and train of signal
It disturbs and is superimposed upon on the small signal of output, cause output signal accuracy not high, nominal 0.25dB is not achieved in attenuation accuracy difference.Mesh
Before, the 6bit attenuator of 0~-31.5dB of attenuation range, decay stepping 0.5dB, the nominal 0.1dB of attenuation accuracy, surveys only 0.1dB
~0.3dB, amplitude fading is bigger, and attenuation accuracy is poorer.It concatenates to obtain with the numerical-control attenuator of 2 0~-31.5dB attenuation ranges
0~-63dB of attenuation range, decay stepping 0.5dB attenuation module, attenuation accuracy due to second level attenuator error be superimposed,
Surveying attenuation accuracy is only 0.1dB~0.65dB, cannot reach 0.25dB precision in entire attenuation range (0~-63dB) and want
It asks, is difficult to meet required precision the chip of 0.1dB is nominally reached even if using attenuation accuracy.In order to improve attenuation accuracy, need
In addition increase decaying trimming circuit to be modified the attenuator circuit.
Mainly using short wavelength emissions, reception electric signal as the analogue signal amplitude numerical control attenuation technical applications of object,
It is required that amplitude fading numerical control range is 0~-62dB, stepping 1dB, stepping accuracy 0.2dB.Existing numerical-control attenuator chip is full
While sufficient significantly attenuation range, it is unable to satisfy attenuation accuracy index.General numerical-control attenuator carries out input signal
Since many factors such as circuit noise influence when big numerical reduction, cause the small Signal-to-Noise of the output after decaying low, decays
Error increases, and is not able to satisfy requirement of the current technology development to attenuation accuracy.
Summary of the invention
The purpose of the present invention is designing a kind of numerical control attenuation circuit, including main attenuator circuit and decoding control circuit, in addition
It further include decaying trimming circuit.Main attenuator circuit is concatenated first master fader and the second master fader, and first and second decline
Subtracting trimming circuit respectively includes 5 triodes and 10 resistance.The base stage (B) of each triode is through 1 resistance and decoding control circuit
Corresponding control signal output connection, collector (C) connect the first master fader or the second master through a semifixed resistor respectively
The analog signal output of attenuator.The resistance value of the semifixed resistor of the suitable each triode concatenation of selection, to this numerical control attenuation electricity
The pad value on road is finely adjusted, and improves the attenuation accuracy of each decaying stepping of this numerical control attenuation circuit in attenuation range.
It is another object of the present invention to design the adjusting method of aforementioned present invention numerical control attenuation circuit.The main decaying electricity of this method
The output end connected vector Network Analyzer on road first disconnects decaying trimming circuit, detects attenuation when undamped trimming circuit；
Calculate the actual attenuation amount of main attenuator circuit at this time and its theoretical value error；It is calculated as supplementing this attenuated error, decaying fine tuning electricity
Semifixed resistor value required for road, decaying trimming circuit connection calculate resulting semifixed resistor, detect and adjust output again
Analog signal attenuation, the semifixed resistor of a step section of going forward side by side decaying trimming circuit.
A kind of numerical control attenuation circuit that the present invention designs includes main attenuator circuit and decoding control circuit, the main decaying electricity
Road includes the first master fader and the second master fader.First master fader and the second master fader are identical attenuator core
Piece includes digit-control resistance device network, has 5 numeric data code input ports, the resistance value of digit-control resistance device network is by numeric data code control
System, the resistance value determine that the external analog signal of input passes through the attenuation amplitude of master fader.
External analog signal inputs the input end of analog signal of the first master fader, and the analog signal of the first master fader is defeated
Outlet connect the input end of analog signal of the second master fader, the second master fader through the first isolation capacitance with the second isolation capacitance
Analog signal output be this numerical control attenuation circuit output end.
The decoding control circuit is programmable chip, there is 62 system control code input terminals, numeric data code output end point
The numeric data code input terminal of the first, second master fader is not connected.
In the present invention program further include decaying trimming circuit, the decaying trimming circuit for respectively with the first master fader
With the first decaying trimming circuit and the second decaying trimming circuit of the cooperation of the second master fader.
First and second decaying trimming circuit structures are identical.Each decaying trimming circuit includes 5 triodes and 10 electricity
Resistance.Corresponding with decoding control circuit to control signal defeated through resistance for the base stage (B) of each triode of first decaying trimming circuit
Outlet connection, the collector (C) of each triode concatenate a semifixed resistor respectively, and five semifixed resistors are through the first isolation capacitance
Connect the output end of the first master fader, each transistor emitter (E) ground connection.Each triode of second decaying trimming circuit
The connection of base stage (B) and emitter (E) is identical as first decaying each triode of trimming circuit, the collector (C) of each triode
A semifixed resistor is concatenated respectively, and five semifixed resistors connect the output end of the second master fader through the 4th isolation capacitance.
The decoding control circuit has 4 groups of numeric data code output ends, every group of 5 numeric data code output ends, and each group is separately connected
One master fader, first decaying trimming circuit, the second master fader and second decaying trimming circuit 5 numeric data codes or NC codes
Input terminal.
When the received NC codes of triode (QAA/QBB) of the first, second decaying trimming circuit are " 0 ", triode base
Extremely 0 level, triode cut-off, the AC impedance between collector and emitter are approximately ∞, the fine tuning electricity of collector series connection
Resistance is hanging, and the triode and semifixed resistor do not influence the output valve for the master fader that it is connect.As the numeric data code (QAA/ of triode
QBB) when being " 1 ", transistor base is high level, triode saturation conduction, and the semifixed resistor ground connection of collector series connection, i.e., this is micro-
Adjust resistance in parallel with the load resistance for the master fader that it is connect, the analog signal voltage of master fader output will be by fine tuning electricity
Resistance partial pressure decaying.
The resistance value of the digit-control resistance device network of the received numeric data code control master fader of master fader, determines the outer of input
Portion's analog signal passes through the attenuation amplitude of master fader.But since its performance indicator of different chips can not identical, group
At the technical indicator that obtains of circuit be also impossible to completely the same, add inevitable interference noise and signal cross-talk, it is main
The amplitude fading of attenuator is unable to reach the requirement of stepping accuracy, this i.e. existing attenuator there are the problem of.The present invention is
One, the decaying trimming circuit of the second master fader configuration, can be debugged according to specific chip and physical circuit, be selected suitable
The resistance value of the semifixed resistor of each triode concatenation, is finely adjusted the pad value of this numerical control attenuation circuit, so that this numerical control attenuation
The attenuation accuracy of each decaying stepping of the circuit in attenuation range reaches 0.2dB.
The resistance value and their connections of digit-control resistance device network in first master fader and the second master fader of the invention
First decaying trimming circuit and second decaying trimming circuit in be connected transistor collector concatenation semifixed resistor value determine
The load resistance of this numerical control attenuation circuit also just determines the attenuation amplitude of this numerical control attenuation circuit.According to this numerical control attenuation circuit
The actual conditions of master fader chip are to each transistor collector string in the first decaying trimming circuit and the second decaying trimming circuit
The semifixed resistor value connect is selected, and the accurate stepping decaying to input analog signal can be realized in this numerical control attenuation circuit.
The control digit 6bit of first, second master fader, amplitude fading 0~-31.5dB of range, decay stepping
0.5dB, chip interior integrates input resistance impedance and output resistance impedance is 50 Ω.
The triode of 2 decaying trimming circuit is high-frequency triode, characteristic frequency fT≥1000MHz。
It is described first, second decaying trimming circuit each triode base stage (B) through the resistance of 8.2k Ω~12k Ω with translate
The corresponding control signal output connection of code control circuit.
A kind of adjusting method of numerical control attenuation circuit of the present invention, the numerical control attenuation circuit includes main attenuator circuit, decoding
Control circuit and decaying trimming circuit.The output end connected vector Network Analyzer of numerical control attenuation circuit, detection output simulation
The attenuation of signal.This adjusting method is the resistance for adjusting the semifixed resistor of each transistor collector connection of 2 decaying trimming circuits
Value, adjusting method key step are as follows:
I, attenuation when undamped trimming circuit is detected
Disconnect 2 decaying trimming circuits, input 000001 respectively in decoding control circuit, 000011,000110,
001101,011010,100000,100010,100101,101011,111000 control code inputs analog signal, vector network
Analyzer detects the analog signal intensity of main attenuator circuit output, and calculates pad value at this time；
II, the error of main attenuator circuit attenuation is calculated
Step I the corresponding attenuation theoretical value of control code that decoding control circuit inputs with it is undamped micro- obtained by step I
The difference of attenuation when tune circuit is the error of main attenuator circuit attenuation；
III, semifixed resistor value required for decaying trimming circuit is calculated
According to the error of the resulting main attenuator circuit attenuation of step II, fine tuning electricity required for decaying trimming circuit is calculated
Resistance value, the semifixed resistor value is in parallel with main attenuator circuit output resistance, to the analog signal width exported after master fader decaying
Degree further fine tuning decaying；
IV, it detects and adjusts again
The decaying resulting semifixed resistor of trimming circuit Connection Step III, and connect with master fader, in decoding control circuit
The control code of input step I, inputs analog signal, and vector network analyzer detects the simulation letter of the output of main attenuator circuit again
Number intensity, and calculate pad value at this time, compared with attenuation theoretical value corresponding with control code, if precision is still greater than 0.2dB, to declining
The semifixed resistor for subtracting trimming circuit is further adjusted, until the attenuation attenuation corresponding with the control code of the analog signal of output
The error of theoretical value is less than or equal to 0.2dB.
Compared with prior art, the advantages of a kind of numerical control attenuation circuit and its adjusting method of the invention are as follows: 1, configuration decaying
Trimming circuit improves attenuation accuracy of the attenuator of 2 pieces of decaying chip concatenation compositions when significantly decaying, this numerical control attenuation
Stepping attenuation accuracy of the circuit in entire attenuation range reduces as far as possible；With the attenuator circuit of existing single-chip, 2 chips
It compares, attenuation accuracy improves 0.3~0.5dB in shortwave frequency range, reaches 0.2dB, and high-fidelity is completed to analogue signal amplitude
Numerical control attenuation, meet user's application requirement；2, using two pieces of attenuator chips and decay trimming circuit network composite design,
It is easily achieved, can easily be accommodated.
Detailed description of the invention
Fig. 1 is the overall structure diagram of this numerical control attenuation circuit embodiment；
Fig. 2 is the decaying trimming circuit structural schematic diagram of this numerical control attenuation circuit embodiment.
Specific embodiment
The overall structure diagram of this numerical control attenuation circuit embodiment is as shown in Figure 1, include main attenuator circuit, encoded control
Circuit and decaying trimming circuit.Figure inside solid line indicates analog signal, and dotted line line indicates control signal.
The main attenuator circuit of this example includes the first master fader and the second master fader.First master fader and the second main decaying
Device is identical PE4302 attenuator chip, includes digit-control resistance device network, has 5 numeric data code input ports, numerical control
The resistance value of resistor network is controlled by numeric data code, which determines external analog signal the declining by master fader of input
Amount of decrease degree.Each PE4302 attenuator chip controls digit 6bit, amplitude fading 0~-31.5dB of range, decay stepping 0.5dB,
Chip interior integrates input resistance impedance and output resistance impedance is 50 Ω.
External analog signal SinInput the input end of analog signal of the first master fader, the analog signal of the first master fader
Output end is through the first isolation capacitance C1With the second isolation capacitance C2The input end of analog signal of the second master fader is connected, second is main
The analog signal output of attenuator is the output analog signal S of this numerical control attenuation circuit through the output of third isolation capacitanceout。
This example decoding control circuit has 62 system control codes defeated for programmable chip using general FPGA/CPLD chip
Enter end, and there are 4 groups of numeric data code output ends, every group of 5 numeric data code output ends, each group is separately connected the first master fader, and first declines
Subtract trimming circuit, 5 numeric data codes or NC codes input terminal of the second master fader and the second decaying trimming circuit.
The decaying trimming circuit in the present invention program is to cooperate respectively with the first master fader and the second master fader
First decaying trimming circuit and second decaying trimming circuit.
As shown in Fig. 2, the first and second decaying trimming circuit structures are identical.Each decaying trimming circuit includes 5 three poles
Pipe and 10 resistance.The triode is high-frequency triode, characteristic frequency fT≥1000MHz。
The base stage (B) of 5 triodes Q10, Q12, Q14, Q16 and Q18 of first decaying trimming circuit are through 10k Ω resistance
Control signal output connection corresponding with decoding control circuit, receives NC codes QAA0, QAA1, QAA2, QAA3 and QAA4；Respectively
The collector (C) of triode concatenates semifixed resistor R10, R12, R14, R16 and a R18 respectively, and above-mentioned five semifixed resistors are equal
The output end of the first master fader, each transistor emitter (E) ground connection are connected through the first isolation capacitance.Second decaying trimming circuit
5 triodes base stage (B) and emitter (E) connection with first decay each triode of trimming circuit it is similar, triode
The base stage (B) of Q20, Q22, Q24, Q26 and Q28 are through 10k Ω resistance control signal output corresponding with decoding control circuit
Connection receives NC codes QBB0, QBB1, QBB2, QBB3 and QBB4；The collector (C) of each triode concatenates a fine tuning respectively
Resistance R20, R22, R24, R26 and R28, above-mentioned five semifixed resistors are through the 4th isolation capacitance C4 the second master fader of connection
Output end.
When the resulting NC codes of transistor base of the first, second decaying trimming circuit are " 0 ", transistor base 0
Level, triode cut-off, AC impedance is approximately ∞ between collector and emitter, and the semifixed resistor of collector series connection is hanging,
The triode and semifixed resistor do not influence the output valve for the master fader that it is connect.When the NC codes of triode are " 1 ", three poles
Pipe base stage is high level, and triode saturation conduction, the semifixed resistor ground connection of collector series connection, the i.e. semifixed resistor are connect with it
The load resistance of master fader is in parallel, and the analog signal voltage of master fader output will be divided by the semifixed resistor decays.
The adjusting method embodiment of numerical control attenuation circuit
The adjusting method embodiment of this numerical control attenuation circuit is adjusted in above-mentioned numerical control attenuation circuit embodiment.Master declines
The output end connected vector Network Analyzer on powered down road, when detection inputs analog signal, the attenuation of output end.Decaying fine tuning electricity
The adjusting method key step of the semifixed resistor of each transistor collector connection in road is as follows:
I, attenuation when undamped trimming circuit is detected
Disconnect 2 decaying trimming circuits, decoding control circuit difference input control code 000001,000011,000110,
001101,011010,100000,100010,100101,101011 and 111000, input analog signal, vector network analyzer
The analog signal intensity of the output of main attenuator circuit is detected, and calculates pad value at this time；
II, the error of main attenuator circuit attenuation is calculated
Step I the corresponding attenuation theoretical value of control code that decoding control circuit inputs with it is undamped micro- obtained by step I
The difference of attenuation when tune circuit is the error of main attenuator circuit attenuation；
The theoretical attenuation value of two master faders of the main attenuator circuit of the numerical control attenuation circuit of this example is as shown in table 2, table 1
The control code of the corresponding decoding control circuit input of numerical control attenuation circuit 63 decaying steppings of this example is given, first and second is main
The obtained numeric data code of attenuator and the first and second decaying obtained NC codes of trimming circuit, and correspondence is provided in last column
Theoretical attenuation value, target pad value of this law using theoretical attenuation value as this numerical control attenuation circuit.D5~D0 in table 1 is indicated
D5, D4, D3, D2, D1 and D0, QA4~QA0 indicates QA4, QA3, QA2, QA1 and QA0, other similar.
This example is 011010 as decoding control circuit input control code D5~D0, is shown in Table 1 serial number 26, and corresponding first master declines
Subtracting the resulting numeric data code QA4~QA0 of device is 11010, and the resulting numeric data code QB4~QB0 of the second master fader is 00000, corresponding
Theoretical attenuation value be -26dB.Attenuation when undamped trimming circuit obtained by step I is -25.82dB, then error be -
0.18dB。
Theoretical attenuation value table of the table 1 for this numerical control attenuation circuit embodiment of different control codes
III, semifixed resistor value required for decaying trimming circuit is calculated
Decayed according to the error calculation of the resulting main attenuator circuit attenuation of step II and finely tunes electricity required for trimming circuit
Resistance value, the semifixed resistor value is in parallel with main attenuator circuit output resistance, carries out to the analog signal exported after master fader decaying
Fine tuning.
The resulting NC codes of trimming circuit of decaying are different with the numeric data code of corresponding master fader, trimming circuit of decaying
The NC codes of receiving are 6 kinds, control the on-off of its 5 triodes, provide 6 kinds of offsets.The numerical control that trimming circuit of decaying receives
Code respectively corresponds the highest order of corresponding master fader numeric data code, please specifically be shown in Table 1.This example decaying trimming circuit
NC codes be 6 kind 00000,00001,00010,00100,01000 and 10000, control respectively its five triodes close entirely or Q1,
Six kinds of working conditions of one in Q2, Q3, Q4 and Q5 conducting, each working condition compensate respectively master fader numeric data code 00000,
00001,00010 and 00011,00100~00111,01000~01111,10000~11,111 6 decaying section.Because same
As soon as the pad value error amount of master fader is slow gradual change in section of decaying, with the collector semifixed resistor of a triode
One decaying section can be compensated.
Under the control code control of serial number 0~31 in table 1, the second master fader the data obtained code is 00000, simulation letter
It is number undamped to pass through the second master fader, it is only necessary to consider the attenuated error of the first master fader.One master fader 0~-
In 31.5 attenuation ranges, maximal accuracy error is less than 0.35dB.A therefore fine tuning of the triode Q18 of the first decaying trimming circuit
Resistance R18 can take into account the error of the first master fader of serial number 16~31 in compensation table 1.
Under the control code control of serial number 32~63 in table 1, the first master fader numeric data code is 11111, i.e., in most
Big attenuation state can not completely eliminate its error although being compensated its error.So when main attenuator circuit it is defeated
The amplitude fading error of analog signal is the sum of the first master fader and the second master fader error, the second decaying trimming circuit out
The sum of the two error will be compensated.General first main attenuator circuit in the error after the maximum attenuation state compensation is+
0.1。
If step II calculate, when the resulting numeric data code QA4~QA0 of the first master fader be 11010, the second master fader institute
Numeric data code QB4~QB0 be 00000, theoretical attenuation value is -26dB, attenuation when undamped trimming circuit obtained by step I
For -25.82dB, the attenuation of required compensation is -0.18dB.
For the ease of selecting the resistance value of semifixed resistor, table 2 can refer to, the semifixed resistor R for trimming circuit of decayingiDecay with it
The table of comparisons of value.RiFor R10, R12, R14, R16, R18, R20, R22, R24, R26 and R28.
The resistance value R of the decaying trimming circuit of table 2iThe table of comparisons of (Ω) and its attenuation (dB)
| Ri(Ω) | Attenuation (dB) | Ri(Ω) | Attenuation (dB) |
| 270 | 0.79 | 680 | 0.33 |
| 300 | 0.72 | 750 | 0.30 |
| 330 | 0.65 | 820 | 0.28 |
| 360 | 0.60 | 910 | 0.26 |
| 390 | 0.56 | 1000 | 0.23 |
| 430 | 0.51 | 1500 | 0.18 |
| 470 | 0.47 | 2000 | 0.13 |
| 510 | 0.44 | 3300 | 0.09 |
| 560 | 0.40 | 4700 | 0.07 |
| 620 | 0.36 | 5600 | 0.06 |
When the resulting numeric data code of the first master fader be 11010, first decaying trimming circuit NC codes QAA4~QAA0
It is 10000, controls its triode Q18 conducting, the value of the semifixed resistor R18 of this transistor collector concatenation declines at this time first
Subtract the resistance value of trimming circuit.Reference table 2 it is found that decaying trimming circuit R18=1500 Ω when attenuation be -0.18dB.
The decaying of this example first 1500 Ω of trimming circuit R18 value.
IV, it detects and adjusts again
The decaying resulting semifixed resistor of trimming circuit Connection Step III, and connect with master fader, in decoding control circuit
The control code of input step I, inputs analog signal, and vector network analyzer detects the simulation letter of the output of main attenuator circuit again
Number intensity, and calculate pad value at this time, compared with attenuation theoretical value corresponding with control code, if precision is still greater than 0.2dB, to declining
The semifixed resistor for subtracting trimming circuit is further adjusted, until the attenuation of the analog signal of output, decaying corresponding with the control code
The error for measuring theoretical value is less than or equal to 0.2dB.
This example step III is calculated into gained R18=1500 Ω access the first decaying trimming circuit, and the first decaying is finely tuned
Circuit is connect with the output end of the first master fader.
For the serial number 26 of table 1, target pad value is -26dB.First master fader attenuation -25.82dB, the first decaying
Trimming circuit attenuation is -0.18dB, and it is -26dB, error 0 that this numerical control attenuation circuit, which exports analog signal attenuation,.
Such as 1 serial number 24 of table, when decoding control circuit input control code D5~D0 is 011000, the first master fader is resulting
Numeric data code QA4~QA0 is 11000, and actual attenuation amount is -23.82dB；The resulting numeric data code QB4~QB0 of second master fader is
00000, analog signal is undamped to be passed through；The first decaying resulting NC codes QAA4~QAA0 of trimming circuit is 10000, compensation
Attenuation be still -0.18dB；The second decaying resulting NC codes QBB4~QBB0 of trimming circuit is 00000, three all poles
Pipe cut-off, does not work to the decaying of circuit.Detect again this numerical control attenuation circuit output analog signal pad value be-
24.00dB is the sum of the first master fader and the first decaying trimming circuit pad value, and the error with theoretical attenuation value -24dB is
0.0dB meets the requirements.
When decoding control circuit input control code is 010000 (such as 1 serial number 16 of table), the resulting data of the first master fader
Code is 10000, and practical attenuation is -15.9dB；The resulting numeric data code of second master fader is 00000, and analog signal is without declining
Subtract and passes through；The first decaying resulting NC codes of trimming circuit are still 10000, and the attenuation of compensation is -0.18dB；Second decaying is micro-
Adjusting the resulting NC codes of circuit is 00000, on circuit decay without influence.The overall attenuation of this numerical control attenuation circuit be-
16.08dB.Error with theoretical attenuation value -16dB is 0.08dB, is met the requirements.
When decoding control circuit input control code is 011111 (such as 1 serial number 31 of table), the resulting data of the first master fader
Code is 11111, and practical attenuation is -30.65dB；The resulting numeric data code of second master fader is 00000, and analog signal is without declining
Subtract and passes through；The first decaying resulting NC codes of trimming circuit are still 10000, and the attenuation of compensation is still -0.18dB；Second decaying
The resulting NC codes of trimming circuit are 00000, on circuit decay without influence.The overall attenuation of this numerical control attenuation circuit be-
30.83dB, error are -0.17dB.
It can be 10000~11111 (sequences i.e. in table 1 to numeric data code when first decaying trimming circuit NC codes are 10000
Numbers 16~31) the first master fader carries out the compensation of actual attenuation amount, makes the stepping essence of the overall attenuation of this numerical control attenuation circuit
Degree is less than 0.2dB.
Other semifixed resistors of first, second decaying trimming circuit, successively determine according to the above method.
By the semifixed resistor of the first, second selected decaying trimming circuit of the adjusting method embodiment of this numerical control attenuation circuit
As shown in table 3.
The semifixed resistor list of the selected decaying trimming circuit of 3 this example of table
Each semifixed resistor of 2 decaying trimming circuits is configured as shown in table 3, this numerical control attenuation circuit is in 0~-62dB
Attenuation range in, each attenuation of decaying stepping and the error of target attenuation are less than 0.2dB, hence it is evident that improve decaying
Stepping accuracy is can satisfy completely using short wavelength emissions, reception electric signal as the analogue signal amplitude numerical control attenuation technology of object
The requirement of 0~-62dB of numerical control attenuation amplitude and stepping accuracy 0.2dB.
Above-described embodiment is only further described the purpose of the present invention, technical scheme and beneficial effects specific
A example, present invention is not limited to this.All any modifications made within the scope of disclosure of the invention, change equivalent replacement
Into etc., it is all included in the scope of protection of the present invention.
Claims (5)
1. a kind of numerical control attenuation circuit, including main attenuator circuit and decoding control circuit, the main attenuator circuit includes first main
Attenuator and the second master fader；First master fader and the second master fader are identical attenuator chip, include numerical control electricity
Device network is hindered, there are 5 numeric data code input ports, the resistance value of digit-control resistance device network is controlled by numeric data code；
External analog signal inputs the input end of analog signal of the first master fader, the analog signal output of the first master fader
The input end of analog signal of the second master fader, the mould of the second master fader are connect with the second isolation capacitance through the first isolation capacitance
Quasi- signal output end is the output end of this numerical control attenuation circuit；
The decoding control circuit is programmable chip, has 62 system control code input terminals, numeric data code output end connects respectively
Connect the numeric data code input terminal of the first, second master fader；
It is characterized by:
It further include decaying trimming circuit；The decaying trimming circuit is to cooperate respectively with the first master fader and the second master fader
First decaying trimming circuit and second decaying trimming circuit；
First and second decaying trimming circuit structures are identical；Each decaying trimming circuit includes 5 triodes and 10 resistance；The
The base stage of each triode of one decaying trimming circuit is connected through resistance control signal output corresponding with decoding control circuit,
The collector of each triode concatenates a semifixed resistor respectively, and five semifixed resistors decline through the first master of the first isolation capacitance connection
Subtract the output end of device, each transistor emitter ground connection；The base stage and emitter of each triode of second decaying trimming circuit
Connection decays with first, and each triode of trimming circuit is identical, and the collector of each triode concatenates a semifixed resistor respectively, and five
A semifixed resistor connects the output end of the second master fader through the 4th isolation capacitance；
The encoded control has 4 groups of numeric data code output ends, every group of 5 numeric data code output ends, and each group is separately connected the first main decaying
Device, first decaying trimming circuit, the second master fader and second decaying trimming circuit 5 numeric data codes or NC codes input terminal；
When first and second decaying trimming circuits the received NC codes of triode be " 0 " when, transistor base be 0 level, three
Pole pipe cut-off；When the numeric data code of triode is " 1 ", transistor base is high level, triode saturation conduction, collector series connection
Semifixed resistor ground connection, i.e., the semifixed resistor is in parallel with the load resistance for the master fader that it is connect, master fader export mould
Quasi- signal voltage will be divided by the semifixed resistor decays.
2. numerical control attenuation circuit according to claim 1, it is characterised in that:
The control digit 6bit of first, second master fader, amplitude fading 0~-31.5dB of range, decay stepping 0.5dB,
Chip interior integrates input resistance impedance and output resistance impedance is 50 Ω.
3. numerical control attenuation circuit according to claim 1, it is characterised in that:
The triode of 2 decaying trimming circuit is high-frequency triode, characteristic frequency fT≥1000MHz。
4. numerical control attenuation circuit according to claim 1, it is characterised in that:
The base stage of each triode of the first, second decaying trimming circuit is through the resistance of 8.2k Ω~12k Ω and encoded control
The corresponding control signal output connection of circuit.
5. the adjusting method of numerical control attenuation circuit according to any one of claim 1 to 4, this adjusting method is adjusting 2
The value of the semifixed resistor of a each transistor collector connection of decaying trimming circuit, it is characterised in that key step is as follows:
The output end connected vector Network Analyzer of the numerical control attenuation circuit, the attenuation of detection output analog signal；
I, attenuation when undamped trimming circuit is detected
Disconnect 2 decaying trimming circuits, decoding control circuit difference input control code 000001,000011,000110,
001101,011010,100000,100010,100101,101011 and 111000, input analog signal, vector network analyzer
The analog signal intensity of the numerical control attenuation circuit output is detected, and calculates pad value at this time；
II, the error of main attenuator circuit attenuation is calculated
Step I undamped fine tuning electricity obtained by the corresponding attenuation theoretical value of control code and step I that decoding control circuit inputs
The difference of attenuation when road is the error of main attenuator circuit attenuation；
III, semifixed resistor value required for decaying trimming circuit is calculated
According to the error calculation of the resulting main attenuator circuit attenuation of step II decay trimming circuit required for semifixed resistor value,
The semifixed resistor value is in parallel with main attenuator circuit output resistance, to the analogue signal amplitude that exports after master fader decaying into one
Step fine tuning decaying；
IV, it detects and adjusts again
The decaying resulting semifixed resistor of trimming circuit Connection Step III, and connect with master fader, it is inputted in decoding control circuit
The control code of step I, inputs analog signal, and the analog signal that vector network analyzer detects the output of main attenuator circuit again is strong
Degree, and pad value at this time is calculated, it is micro- to decaying if precision is still greater than 0.2dB compared with attenuation theoretical value corresponding with control code
The semifixed resistor of circuit is adjusted further to adjust, until the attenuation of the analog signal of output attenuation corresponding with the control code is theoretical
The error of value is less than or equal to 0.2dB.
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