CN109995344B - Numerical control attenuation circuit and adjusting method thereof - Google Patents
Numerical control attenuation circuit and adjusting method thereof Download PDFInfo
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- H—ELECTRICITY
- H03—ELECTRONIC CIRCUITRY
- H03H—IMPEDANCE NETWORKS, e.g. RESONANT CIRCUITS; RESONATORS
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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 invention relates to a numerical control attenuation circuit and an adjusting method thereof. The main attenuator circuit of the numerical control attenuator circuit is a first main attenuator and a second main attenuator which are connected in series, and the main attenuator circuit also comprises a first attenuation trimming circuit and a second attenuation trimming circuit which comprise a plurality of triodes and resistors, wherein the base electrode of each triode is connected with a decoding control circuit through the resistor, and the collector electrode is connected with the analog signal output end of the first main attenuator or the second main attenuator through the trimming resistor. And the attenuation value of the circuit is finely adjusted by selecting a suitable fine adjustment resistor, so that the attenuation stepping precision is improved. The method for adjusting the digital control attenuation circuit is that the output end of the main attenuation circuit is connected with a vector network analyzer, the attenuation trimming circuit is disconnected firstly, the attenuation quantity at the moment is detected, the attenuation error of the main attenuation circuit is calculated as the trimming resistance value of the attenuation trimming circuit required for supplementing the error. The invention improves the stepping attenuation precision of the attenuator with 2 chips connected in series and reaches 0.2dB. And the composite design of the double chips and the attenuation fine tuning circuit network is easy to realize and easy to adjust.
Description
Technical Field
The invention relates to an amplitude adjusting technology of an analog signal, in particular to a numerical control attenuation circuit and an adjusting method thereof.
Background
The signals originally present in nature are analog signals, such as sound, images, brightness, radio waves, etc., which mostly require changing their amplitude when used by the radio user. In the field of amplitude control of low and medium frequency analog signals, common application objects include short wave radio signals, radar medium frequency signals and other low and medium frequency analog signals. The signals are required to be adjusted in amplitude during application, and the signal interface requirements of the subsequent circuits are met.
Amplitude adjustment of analog signals is mainly divided into two modes of mechanical adjustment and electronic adjustment. The mechanical adjustment is performed by applying a mechanical force to the variable resistor to change the voltage division ratio of the variable resistor in the circuit to change the amplitude of the signal, for example, by rotating the volume knob of the radio-recorder to change the size of the output music sound. The electronic regulation mode is to utilize the parameters of electronic elements in the electric signal control circuit to change the amplitude of the signal. The electronic regulation mode is divided into an analog control mode and a digital control mode. The control signal of the analog control mode is an analog electric signal, the voltage of the analog electric signal is continuously changed, and the attenuation value of the analog attenuator is also continuously changed. The numerical control mode utilizes two digital levels of 0 and 1 to control the attenuation of the attenuator, the attenuation is discrete and discontinuous, and the numerical control mode provides great convenience for remote control.
The current common numerical control attenuator is classified according to the number of control data bits, mainly comprises 1-6 bits, and the attenuation stepping number of the numerical control attenuator is 2 1 ～2 6 The method comprises the steps of carrying out a first treatment on the surface of the Classified by the attenuation step (dB) size, commonly used are 0.125, 0.25, 0.5, 1.0, 2.0, 3.0, 6.0, etc.; the attenuation ranges are classified according to the numerical control attenuation range (dB), and commonly used attenuation ranges are 0-3, 0-6, 0-31.5 and the like.
The numerical control attenuator devices in the current market mainly have two types, one type is small in amplitude attenuation step (0.125 dB) and high in precision (0.1 dB), but the total attenuation range is small; the other is that the attenuation step is large (such as 3 dB) and the accuracy is low (0.5 dB), but the total attenuation range is large.
The numerical control amplitude attenuation range of a single-chip device of a numerical control attenuator in the current market is 0 to minus 31.5dB, and the attenuation step is 0.25dB (or 0.5 dB); the amplitude attenuation range of the multi-chip combined product (the series connection of two attenuation chips with the attenuation amount of 0 to-31.5 dB) reaches 0 to-63 dB, and the attenuation step is 0.25dB. Measurements of these products found that in the 0 to-63 dB attenuation range, it was not guaranteed that the attenuation accuracy of each step reached 0.25dB. The attenuation precision can meet the index requirement when the attenuation is smaller, but the attenuation precision becomes poor when the attenuation is large, and the attenuation error is up to 0.6dB at most, mainly due to the influence of circuit noise and the like. Normally, the nominal signal input amplitude of the numerical control attenuator is 0dBm, when the attenuation amount is large (for example, -60 dB), the output amplitude of the signal is too small (-60 dBm) after attenuation, the signal is obviously affected by circuit noise interference and signal crosstalk, the circuit noise and the signal crosstalk are superposed on the output small signal, the output signal precision is low, and the attenuation precision difference is less than the nominal 0.25dB. At present, the attenuation range of the 6-bit attenuator is 0 to minus 31.5dB, the attenuation step is 0.5dB, the attenuation precision is 0.1dB nominally, the actual measurement is only 0.1dB to 0.3dB, and the greater the amplitude attenuation, the poorer the attenuation precision. The attenuation modules with the attenuation ranges of 0 to-63 dB and the attenuation stepping of 0.5dB are obtained by connecting 2 numerical control attenuators with the attenuation ranges of 0 to-31.5 dB, the attenuation precision is only 0.1dB to 0.65dB due to the error superposition of the two-stage attenuators, the precision requirement of 0.25dB can not be met in the whole attenuation range (0 to-63 dB), and even if a chip with the attenuation precision of 0.1dB is adopted, the precision requirement can not be met. In order to improve the attenuation accuracy, an attenuation fine adjustment circuit needs to be additionally added to correct the attenuation circuit.
In the application field of the digital control attenuation technology of the amplitude of the analog signal mainly taking the short wave transmitting and receiving electric signals as objects, the digital control range of the amplitude attenuation is required to be 0 to minus 62dB, the step is 1dB, and the step precision is 0.2dB. The existing numerical control attenuator chip can not meet the attenuation precision index while meeting the large attenuation range. When the general numerical control attenuator carries out large-value attenuation on an input signal, the signal to noise ratio of the attenuated output small signal is low due to the influence of various factors such as circuit noise, and the attenuation error is increased, so that the requirement of the current technical development on the attenuation precision can not be met.
Disclosure of Invention
The invention aims to design a numerical control attenuation circuit which comprises a main attenuation circuit, a decoding control circuit and an attenuation fine tuning circuit. The main attenuation circuit is a first main attenuator and a second main attenuator which are connected in series, and each of the first attenuation trimming circuit and the second attenuation trimming circuit comprises 5 triodes and 10 resistors. The base electrode (B) of each triode is connected with the corresponding control signal output end of the decoding control circuit through 1 resistor, and the collector electrode (C) is connected with the analog signal output end of the first main attenuator or the second main attenuator through a trimming resistor respectively. And selecting the resistance value of a trimming resistor connected with each triode in series, trimming the attenuation value of the numerical control attenuation circuit, and improving the attenuation precision of each attenuation step of the numerical control attenuation circuit in the attenuation range.
Another object of the present invention is to devise the above-mentioned method for adjusting the digitally controlled attenuator circuit of the present invention. The output end of the main attenuation circuit is connected with a vector network analyzer, the attenuation fine tuning circuit is disconnected firstly, and the attenuation amount of the attenuation fine tuning circuit is detected; calculating the error between the actual attenuation of the main attenuation circuit and the theoretical value of the main attenuation circuit; and calculating a trimming resistance value required by the attenuation trimming circuit for supplementing the attenuation error, connecting the attenuation trimming circuit with the calculated trimming resistance, detecting and adjusting the attenuation of the output analog signal again, and further adjusting the trimming resistance of the attenuation trimming circuit.
The invention designs a numerical control attenuation circuit which comprises a main attenuation circuit and a decoding control circuit, wherein the main attenuation circuit comprises a first main attenuator and a second main attenuator. The first main attenuator and the second main attenuator are the same attenuator chip, a numerical control resistor network is contained, the numerical control resistor network is provided with 5 data code input ports, the resistance value of the numerical control resistor network is controlled by the data code, and the resistance value determines the attenuation amplitude of an input external analog signal passing through the main attenuator.
The external analog signal is input into the analog signal input end of the first main attenuator, the analog signal output end of the first main attenuator is connected with the analog signal input end of the second main attenuator through the first isolation capacitor and the second isolation capacitor, and the analog signal output end of the second main attenuator is the output end of the digital control attenuation circuit.
The decoding control circuit is a programmable chip and is provided with a 6-bit 2-system control code input end, and the data code output end of the decoding control circuit is respectively connected with the data code input ends of the first main attenuator and the second main attenuator.
The invention also provides an attenuation fine tuning circuit, which is a first attenuation fine tuning circuit and a second attenuation fine tuning circuit respectively matched with the first main attenuator and the second main attenuator.
The first and second attenuation trimming circuits are identical in structure. Each attenuation trimming circuit comprises 5 triodes and 10 resistors. The base electrode (B) of each triode of the first attenuation trimming circuit is connected with the corresponding control signal output end of the decoding control circuit through a resistor, the collector electrode (C) of each triode is respectively connected with one trimming resistor in series, the five trimming resistors are all connected with the output end of the first main attenuator through a first isolation capacitor, and the emitter electrode (E) of each triode is grounded. The base (B) and the emitter (E) of each triode of the second attenuation trimming circuit are connected with the same triode of the first attenuation trimming circuit, the collector (C) of each triode is respectively connected with one trimming resistor in series, and the five trimming resistors are all connected with the output end of the second main attenuator through a fourth isolation capacitor.
The decoding control circuit is provided with 4 groups of data code output ends, each group of 5 data code output ends is respectively connected with 5 data code or numerical control code input ends of the first main attenuator, the first attenuation fine tuning circuit, the second main attenuator and the second attenuation fine tuning circuit.
When the numerical control code (QAA/QBB) received by the audions of the first and second attenuation trimming circuits is 0, the audion base is 0 level, the audion is cut off, the alternating current impedance between the collector and the emitter is approximately +.. When the data code (QAA/QBB) of the triode is '1', the triode base is high level, the triode is saturated and conducted, and the trimming resistor connected in series with the collector is grounded, namely, the trimming resistor is connected with the load resistor of the main attenuator in parallel, and the analog signal voltage output by the main attenuator is attenuated by the trimming resistor in a voltage dividing way.
The data code received by the main attenuator controls the resistance value of the numerical control resistor network of the main attenuator, and determines the attenuation amplitude of the input external analog signal passing through the main attenuator. However, the performance indexes of different chips cannot be identical, the technical indexes obtained by the composed circuits cannot be identical, and the amplitude attenuation of the main attenuator cannot meet the requirement of stepping precision, namely the existing attenuator has the problems of unavoidable interference noise and signal crosstalk. The invention provides an attenuation trimming circuit configured for a first main attenuator and a second main attenuator, which can be debugged according to a specific chip and a specific circuit, select the resistance value of a trimming resistor connected in series with proper triodes, and trim the attenuation value of the digital control attenuation circuit so that the attenuation precision of each attenuation step of the digital control attenuation circuit in an attenuation range reaches 0.2dB.
According to the invention, the resistance values of the numerical control resistor network in the first main attenuator and the second main attenuator and the trimming resistance values connected in series with the collector electrodes of the triodes conducted in the first attenuation trimming circuit and the second attenuation trimming circuit are used for determining the load resistance of the numerical control attenuation circuit, and the attenuation amplitude of the numerical control attenuation circuit is determined. According to the actual condition of the main attenuator chip of the digital attenuation circuit, the trimming resistance value of each triode collector in the first attenuation trimming circuit and the second attenuation trimming circuit is selected, and the digital attenuation circuit can realize accurate stepping attenuation of an input analog signal.
The control bit number of the first main attenuator and the second main attenuator is 6bit, the amplitude attenuation range is 0-31.5 dB, the attenuation steps are 0.5dB, and the impedance of the input resistor and the impedance of the output resistor integrated in the chip are 50 omega.
The triodes of the 2 attenuation fine tuning circuits are all high-frequency triodes, and the characteristic frequency f T ≥1000MHz。
The base electrode (B) of each triode of the first attenuation trimming circuit and the second attenuation trimming circuit is connected with the corresponding control signal output end of the decoding control circuit through the resistor of 8.2k omega-12 k omega.
The invention relates to a method for adjusting a numerical control attenuation circuit, which comprises a main attenuation circuit, a decoding control circuit and an attenuation fine adjustment circuit. The output end of the numerical control attenuation circuit is connected with a vector network analyzer, and the attenuation of the analog signal at the output end is detected. The adjusting method is to adjust the resistance value of trimming resistors connected with the collector electrodes of all triodes of the 2 attenuation trimming circuits, and mainly comprises the following steps:
i, detecting attenuation amount of non-attenuation fine tuning circuit
2 attenuation fine tuning circuits are disconnected, 000001, 000011, 000110, 001101, 011010, 100000, 100010, 100101, 101011 and 111000 control codes are respectively input into a decoding control circuit, analog signals are input, and a vector network analyzer detects the analog signal intensity output by a main attenuation circuit and calculates attenuation values at the moment;
II, calculating the error of the attenuation of the main attenuation circuit
Step I, the difference between the theoretical attenuation value corresponding to the control code input by the decoding control circuit and the attenuation value obtained in the step I when the attenuation fine tuning circuit is not used is the error of the attenuation value of the main attenuation circuit;
III, calculating trimming resistance value needed by attenuation trimming circuit
Calculating a trimming resistance value required by the attenuation trimming circuit according to the error of the attenuation quantity of the main attenuation circuit obtained in the step II, wherein the trimming resistance value is connected with an output resistor of the main attenuation circuit in parallel, and further trimming and attenuating the amplitude of the analog signal output by the main attenuator after attenuation;
IV, detecting and adjusting again
The attenuation trimming circuit is connected with the trimming resistor obtained in the step III and is connected with the main attenuator, the control code in the step I is input into the decoding control circuit, an analog signal is input, the vector network analyzer detects the intensity of the analog signal output by the main attenuation circuit again, calculates the attenuation value at the moment, compares the attenuation value with the attenuation theoretical value corresponding to the control code, and if the precision is still more than 0.2dB, further adjusts the trimming resistor of the attenuation trimming circuit until the error of the attenuation value of the output analog signal and the attenuation theoretical value corresponding to the control code is less than or equal to 0.2dB.
Compared with the prior art, the numerical control attenuation circuit and the adjusting method thereof have the advantages that: 1. the attenuation fine tuning circuit is configured, so that the attenuation precision of the attenuator formed by connecting 2 attenuation chips in series is improved when the attenuator attenuates greatly, and the stepping attenuation precision of the digital control attenuation circuit in the whole attenuation range is reduced as much as possible; compared with the existing single-chip and 2-chip attenuation circuits, the attenuation precision in the short-wave frequency band is improved by 0.3-0.5 dB, the attenuation reaches 0.2dB, the digital control attenuation of the amplitude of the analog signal is completed in high fidelity, and the application requirements of users are met; 2. the composite design of two attenuator chips and an attenuation fine tuning circuit network is adopted, so that the method is easy to realize and easy to adjust.
Drawings
FIG. 1 is a schematic diagram of the overall structure of an embodiment of the digital attenuation circuit;
fig. 2 is a schematic diagram of an attenuation trimming circuit according to the embodiment of the digital attenuation circuit.
Detailed Description
The overall structure diagram of the embodiment of the digital control attenuation circuit is shown in fig. 1, and comprises a main attenuation circuit, a decoding control circuit and an attenuation fine tuning circuit. The solid line connection in the figure represents the analog signal, and the broken line connection represents the control signal.
The main attenuator circuit of this example includes a first main attenuator and a second main attenuator. The first main attenuator and the second main attenuator are the same PE4302 attenuator chip, and the PE4302 attenuator chip contains a numerical control resistor network which is provided with 5 data code input ports, wherein the resistance value of the numerical control resistor network is controlled by a data code, and the resistance value determines the attenuation amplitude of an input external analog signal passing through the main attenuator. Each PE4302 attenuator chip controls the bit number to be 6bit, the amplitude attenuation range is 0-31.5 dB, the attenuation steps are 0.5dB, and the impedance of the input resistor and the impedance of the output resistor integrated in the chip are 50 omega.
External analog signal S in An analog signal input end of the first main attenuator is input, and an analog signal output end of the first main attenuator passes through a first isolation capacitor C 1 And a second isolation capacitor C 2 The analog signal output end of the second main attenuator is output as an output analog signal S of the digital control attenuation circuit through a third isolation capacitor out 。
The decoding control circuit is a programmable chip, adopts a general FPGA/CPLD chip, has a 6-bit 2-system control code input end, has 4 groups of data code output ends, each group of 5 data code output ends is respectively connected with the first main attenuator, the first attenuation fine tuning circuit, the second main attenuator and 5 data code or numerical control code input ends of the second attenuation fine tuning circuit.
The attenuation fine tuning circuit in the scheme of the invention is a first attenuation fine tuning circuit and a second attenuation fine tuning circuit which are respectively matched with the first main attenuator and the second main attenuator.
As shown in fig. 2, the first and second attenuation fine tuning circuits are identical in structure. Each attenuation trimming circuit comprises 5 triodes and 10 resistors. The triodes are high-frequency triodes with characteristic frequency f T ≥1000MHz。
The base electrodes (B) of the 5 triodes Q10, Q12, Q14, Q16 and Q18 of the first attenuation fine tuning circuit are connected with the corresponding control signal output ends of the decoding control circuit through 10kΩ resistors, and are used for receiving numerical control codes QAA0, QAA1, QAA2, QAA3 and QAA4; the collector electrode (C) of each triode is respectively connected in series with one trimming resistor R10, R12, R14, R16 and R18, and the five trimming resistors are all connected with the output end of the first main attenuator through a first isolation capacitor, and the emitter electrode (E) of each triode is grounded. The base (B) and the emitter (E) of the 5 triodes of the second attenuation trimming circuit are connected similarly to the triodes of the first attenuation trimming circuit, and the base (B) of the triodes Q20, Q22, Q24, Q26 and Q28 are connected with the corresponding control signal output ends of the decoding control circuit through 10kΩ resistors to receive numerical control codes QBB0, QBB1, QBB2, QBB3 and QBB4; the collector (C) of each triode is respectively connected in series with a trimming resistor R20, R22, R24, R26 and R28, and the five trimming resistors are all connected with the output end of the second main attenuator through a fourth isolation capacitor C4.
When the numerical control code obtained by the triode bases of the first and second attenuation trimming circuits is 0, the triode base is 0 level, the triode is cut off, the alternating current impedance between the collector and the emitter is approximately +.. When the numerical control code of the triode is '1', the base of the triode is high level, the triode is saturated and conducted, and the trimming resistor connected in series with the collector is grounded, namely, the trimming resistor is connected with the load resistor of the main attenuator connected with the trimming resistor in parallel, and the analog signal voltage output by the main attenuator is attenuated by the trimming resistor in a voltage dividing way.
Method embodiment of adjusting digital control attenuation circuit
The embodiment of the method for adjusting the numerical control attenuation circuit adjusts the embodiment of the numerical control attenuation circuit. The output end of the main attenuation circuit is connected with the vector network analyzer, and when the input analog signal is detected, the attenuation of the output end is achieved. The method for adjusting the trimming resistor connected with the collector electrode of each triode of the attenuation trimming circuit mainly comprises the following steps:
i, detecting attenuation amount of non-attenuation fine tuning circuit
2 attenuation fine tuning circuits are disconnected, control codes 000001, 000011, 000110, 001101, 011010, 100000, 100010, 100101, 101011 and 111000 are respectively input into a decoding control circuit, analog signals are input, and a vector network analyzer detects the analog signal intensity of the output of a main attenuation circuit and calculates attenuation values at the moment;
II, calculating the error of the attenuation of the main attenuation circuit
Step I, the difference between the theoretical attenuation value corresponding to the control code input by the decoding control circuit and the attenuation value obtained in the step I when the attenuation fine tuning circuit is not used is the error of the attenuation value of the main attenuation circuit;
the theoretical attenuation values of the two main attenuators of the main attenuation circuit of the numerical control attenuation circuit are shown in table 2, table 1 shows control codes input by the decoding control circuit corresponding to 63 attenuation steps of the numerical control attenuation circuit of the example, the data codes obtained by the first main attenuator and the second main attenuator and the numerical control codes obtained by the first attenuation fine tuning circuit and the second attenuation fine tuning circuit, and the corresponding theoretical attenuation values are given in the last column. D5 to D0 in table 1 represent D5, D4, D3, D2, D1 and D0, and QA4 to QA0 represent QA4, QA3, QA2, QA1 and QA0, and others are similar.
In this example, when the control codes D5 to D0 are 011010, see the sequence number 26 in table 1, the data codes QA4 to QA0 obtained by the corresponding first main attenuator are 11010, the data codes QB4 to QB0 obtained by the second main attenuator are 00000, and the corresponding theoretical attenuation value is-26 dB. The attenuation of the non-attenuation fine tuning circuit obtained in the step I is-25.82 dB, and then the error is-0.18 dB.
Table 1 theoretical attenuation value table for the embodiment of the present digitally controlled attenuation circuit for different control codes
III, calculating trimming resistance value needed by attenuation trimming circuit
And D, calculating a trimming resistance value required by the attenuation trimming circuit according to the error of the attenuation quantity of the main attenuation circuit obtained in the step II, connecting the trimming resistance value with the output resistance of the main attenuation circuit in parallel, and trimming the analog signal output after the attenuation of the main attenuator.
The digital control code obtained by the attenuation fine tuning circuit is different from the data code of the main attenuator corresponding to the digital control code, the digital control code received by the attenuation fine tuning circuit is 6, the on-off of 5 triodes of the digital control code is controlled, and 6 compensation values are provided. The numerical control codes received by the attenuation fine tuning circuit correspond to the highest bits of the corresponding main attenuator data codes respectively, and the specific details are shown in table 1. The numerical control code of the attenuation fine tuning circuit is 6 kinds of 00000, 00001, 00010, 00100, 01000 and 10000, and the five triodes are respectively controlled to be totally closed or one of Q1, Q2, Q3, Q4 and Q5 is conducted to six working states, and the working states respectively compensate six attenuation sections of main attenuator data codes 00000, 00001, 00010 and 00011, 00100-00111, 01000-01111 and 10000-11111. Because the attenuation value error value of the main attenuator in the same attenuation section is gradually changed slowly, the attenuation section can be compensated by using the collector trimming resistor of one triode.
Under the control of the control codes with the serial numbers of 0 to 31 in table 1, the data codes obtained by the second main attenuator are 00000, the analog signals pass through the second main attenuator without attenuation, and only the attenuation error of the first main attenuator needs to be considered. A main attenuator is in an attenuation range of 0 to minus 31.5, and the maximum precision error is smaller than 0.35dB. Therefore, one trimming resistor R18 of the transistor Q18 of the first attenuation trimming circuit can compensate the errors of the first main attenuators with the numbers 16 to 31 in the table 1.
Under the control of the control codes numbered 32-63 in table 1, the first main attenuator data codes are 11111, i.e., in the maximum attenuation state, and although the errors are compensated, it is impossible to completely eliminate the errors. Therefore, the amplitude attenuation error of the analog signal output by the main attenuation circuit at the moment is the sum of the errors of the first main attenuator and the second main attenuator, and the second attenuation fine tuning circuit compensates the sum of the errors of the first main attenuator and the second main attenuator. The error of the first main attenuation circuit after being compensated in the maximum attenuation state is generally +0.1.
And (2) calculating in the step (II), when the data codes QA 4-QA 0 obtained by the first main attenuator are 11010, the data codes QB 4-QB 0 obtained by the second main attenuator are 00000, the theoretical attenuation value is-26 dB, the attenuation amount of the non-attenuation fine tuning circuit obtained in the step (I) is-25.82 dB, and the attenuation amount required to be compensated is-0.18 dB.
To facilitate selection of the trimming resistor, the trimming resistor R of the trimming circuit is attenuated by referring to Table 2 i A table of comparison with the attenuation values. R is R i R10, R12, R14, R16, R18, R20, R22, R24, R26 and R28.
Table 2 resistance R of attenuation trimming circuit i Comparison table of (omega) and attenuation (dB) thereof
| R i (Ω) | Attenuation (dB) | R i (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 data code obtained by the first main attenuator is 11010, the numerical control codes QAA 4-QAA 0 of the first attenuation trimming circuit are 10000, the triode Q18 is controlled to be conducted, and the value of the trimming resistor R18 connected in series with the triode collector is the resistance value of the first attenuation trimming circuit. Referring to table 2, the attenuation amount is-0.18 dB when the attenuation trimming circuit r18=1500Ω.
The first attenuation fine tuning circuit R18 in this example takes a value of 1500Ω.
IV, detecting and adjusting again
The attenuation trimming circuit is connected with the trimming resistor obtained in the step III and is connected with the main attenuator, the control code in the step I is input into the decoding control circuit, an analog signal is input, the vector network analyzer detects the intensity of the analog signal output by the main attenuation circuit again, calculates the attenuation value at the moment, compares the attenuation value with the attenuation theoretical value corresponding to the control code, if the precision is still more than 0.2dB, further adjusts the trimming resistor of the attenuation trimming circuit until the attenuation value of the analog signal is output, and the error of the attenuation theoretical value corresponding to the control code is less than or equal to 0.2dB.
And (3) connecting the R18=1500Ω calculated in the step III of the example to a first attenuation fine tuning circuit, and connecting the first attenuation fine tuning circuit with the output end of the first main attenuator.
For sequence number 26 of Table 1, the target attenuation value is-26 dB. The attenuation of the first main attenuator is-25.82 dB, the attenuation of the first attenuation fine tuning circuit is-0.18 dB, the attenuation of the output analog signal of the digital control attenuation circuit is-26 dB, and the error is 0.
As shown in the sequence number 24 of table 1, when the input control codes D5 to D0 of the decoding control circuit are 011200, the data codes QA4 to QA0 obtained by the first main attenuator are 11000, and the actual attenuation is-23.82 dB; the data codes QB 4-QB 0 obtained by the second main attenuator are 00000, and the analog signals pass through without attenuation; the digital control codes QAA 4-QAA 0 obtained by the first attenuation fine tuning circuit are 10000, and the compensated attenuation is still-0.18 dB; the numerical control codes QBB4 to QBB0 obtained by the second attenuation fine tuning circuit are 00000, and all triodes are cut off and do not act on the attenuation of the circuit. The attenuation value of the output analog signal of the numerical control attenuation circuit is detected to be-24.00 dB again, the sum of the attenuation values of the first main attenuator and the first attenuation fine tuning circuit is detected, the error between the attenuation value and the theoretical attenuation value of-24 dB is 0.0dB, and the requirements are met.
When the input control code of the decoding control circuit is 010000 (as shown as sequence number 16 of table 1), the data code obtained by the first main attenuator is 10000, and the actual attenuation is-15.9 dB; the data code obtained by the second main attenuator is 00000, and the analog signal passes through without attenuation; the numerical control code obtained by the first attenuation fine tuning circuit is 10000, and the compensated attenuation is-0.18 dB; the numerical control code obtained by the second attenuation fine tuning circuit is 00000, and the circuit attenuation is not influenced. The total attenuation of the numerical control attenuation circuit is-16.08 dB. The error with the theoretical attenuation value of-16 dB is 0.08dB, which meets the requirements.
When the control code input by the decoding control circuit is 01111 (such as the sequence number 31 of the table 1), the data code obtained by the first main attenuator is 11111, and the actual attenuation is-30.65 dB; the data code obtained by the second main attenuator is 00000, and the analog signal passes through without attenuation; the numerical control code obtained by the first attenuation fine tuning circuit is 10000, and the compensated attenuation is-0.18 dB; the numerical control code obtained by the second attenuation fine tuning circuit is 00000, and the circuit attenuation is not influenced. The total attenuation of the numerical control attenuation circuit is-30.83 dB, and the error is-0.17 dB.
When the numerical control code of the first attenuation fine tuning circuit is 10000, the actual attenuation compensation can be carried out on the first main attenuator with the data code of 10000-11111 (namely, the serial numbers of 16-31 in the table 1), so that the stepping precision of the total attenuation of the numerical control attenuation circuit is less than 0.2dB.
The other trimming resistances of the first and second attenuation trimming circuits are sequentially determined as described above.
The trimming resistances of the first and second attenuation trimming circuits selected according to the embodiment of the adjusting method of the digital attenuation circuit are shown in table 3.
Table 3 list of trim resistors for the selected attenuation trim circuits of this example
The trimming resistors of the 2 attenuation trimming circuits are configured as shown in the table 3, the digital control attenuation circuit has the attenuation range of 0 to minus 62dB, the error between the attenuation of each attenuation step and the target attenuation is smaller than 0.2dB, the attenuation step precision is obviously improved, and the requirements of the digital control attenuation range of 0 to minus 62dB and the step precision of 0.2dB of the analog signal amplitude digital control attenuation technology aiming at short wave transmission and reception of electric signals can be completely met.
The above embodiments are merely specific examples for further detailed description of the object, technical solution and advantageous effects of the present invention, and the present invention is not limited thereto. Any modification, equivalent replacement, improvement, etc. made within the scope of the present disclosure are included in the scope of the present invention.
Claims (5)
1. The digital control attenuation circuit comprises a main attenuation circuit and a decoding control circuit, wherein the main attenuation circuit comprises a first main attenuator and a second main attenuator; the first main attenuator and the second main attenuator are the same attenuator chip, a numerical control resistor network is contained, the numerical control resistor network is provided with 5 data code input ports, and the resistance value of the numerical control resistor network is controlled by the data codes;
the external analog signal is input into the analog signal input end of the first main attenuator, the analog signal output end of the first main attenuator is connected with the analog signal input end of the second main attenuator through the first isolation capacitor and the second isolation capacitor, and the analog signal output end of the second main attenuator is the output end of the digital control attenuation circuit;
the decoding control circuit is a programmable chip and is provided with a 6-bit 2-system control code input end, and a data code output end of the decoding control circuit is respectively connected with the data code input ends of the first main attenuator and the second main attenuator;
the method is characterized in that:
the damping fine tuning circuit is also included; the attenuation fine tuning circuit is a first attenuation fine tuning circuit and a second attenuation fine tuning circuit which are respectively matched with the first main attenuator and the second main attenuator;
the first attenuation fine tuning circuit and the second attenuation fine tuning circuit have the same structure; each attenuation trimming circuit comprises 5 triodes and 10 resistors; the base electrode of each triode of the first attenuation trimming circuit is connected with the corresponding control signal output end of the decoding control circuit through a resistor, the collector electrode of each triode is respectively connected with one trimming resistor in series, the five trimming resistors are all connected with the output end of the first main attenuator through a first isolation capacitor, and the emitter electrode of each triode is grounded; the base electrode and the emitter electrode of each triode of the second attenuation trimming circuit are connected with the triodes of the first attenuation trimming circuit in the same way, the collector electrodes of the triodes are respectively connected with a trimming resistor in series, and the five trimming resistors are connected with the output end of the second main attenuator through a fourth isolation capacitor;
the decoding control circuit is provided with 4 groups of data code output ends, each group of 5 data code output ends is respectively connected with 5 data code or numerical control code input ends of the first main attenuator, the first attenuation fine tuning circuit, the second main attenuator and the second attenuation fine tuning circuit;
when the numerical control code received by the triodes of the first and second attenuation fine tuning circuits is 0, the base of the triode is 0 level, and the triode is cut off; when the data code of the triode is '1', the base of the triode is high level, the triode is saturated and conducted, and the trimming resistor connected in series with the collector is grounded, namely, the trimming resistor is connected with the load resistor of the main attenuator connected with the trimming resistor in parallel, and the analog signal voltage output by the main attenuator is divided and attenuated by the trimming resistor.
2. The digitally controlled attenuation circuit of claim 1, wherein:
the control bit number of the first main attenuator and the second main attenuator is 6bit, the amplitude attenuation range is 0-31.5 dB, the attenuation steps are 0.5dB, and the impedance of the input resistor and the impedance of the output resistor integrated in the chip are 50 omega.
3. The digitally controlled attenuation circuit of claim 1, wherein:
the triodes of the first attenuation trimming circuit and the second attenuation trimming circuit are high-frequency triodes, and the characteristic frequency f T ≥1000MHz。
4. The digitally controlled attenuation circuit of claim 1, wherein:
the base electrodes of the triodes of the first attenuation trimming circuit and the second attenuation trimming circuit are connected with the corresponding control signal output ends of the decoding control circuit through the resistors of 8.2k omega-12 k omega.
5. The method for adjusting a digitally controlled attenuation circuit according to any one of claims 1 to 4, wherein the method adjusts the value of the trimming resistor connected to the collector of each transistor of the 2 attenuation trimming circuits, and is characterized by comprising the steps of:
the output end of the numerical control attenuation circuit is connected with a vector network analyzer, and the attenuation of the analog signal at the output end is detected;
i, detecting attenuation amount of non-attenuation fine tuning circuit
2 attenuation fine tuning circuits are disconnected, control codes 000001, 000011, 000110, 001101, 011010, 100000, 100010, 100101, 101011 and 111000 are respectively input into a decoding control circuit, analog signals are input, and a vector network analyzer detects the analog signal intensity output by the numerical control attenuation circuits and calculates attenuation values at the moment;
II, calculating the error of the attenuation of the main attenuation circuit
Step I, the difference between the theoretical attenuation value corresponding to the control code input by the decoding control circuit and the attenuation value obtained in the step I when the attenuation fine tuning circuit is not used is the error of the attenuation value of the main attenuation circuit;
III, calculating trimming resistance value needed by attenuation trimming circuit
Calculating a trimming resistance value required by the attenuation trimming circuit according to the error of the attenuation quantity of the main attenuation circuit obtained in the step II, wherein the trimming resistance value is connected with an output resistor of the main attenuation circuit in parallel, and further trimming and attenuating the amplitude of the analog signal output by the main attenuator after attenuation;
IV, detecting and adjusting again
The attenuation trimming circuit is connected with the trimming resistor obtained in the step III and is connected with the main attenuator, the control code in the step I is input into the decoding control circuit, an analog signal is input, the vector network analyzer detects the intensity of the analog signal output by the main attenuation circuit again, calculates the attenuation value at the moment, compares the attenuation value with the attenuation theoretical value corresponding to the control code, and if the precision is still more than 0.2dB, further adjusts the trimming resistor of the attenuation trimming circuit until the error of the attenuation value of the output analog signal and the attenuation theoretical value corresponding to the control code is less than or equal to 0.2dB.
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