CN101257466B - Apparatus and method for performing attenuation to direct current offset of equipment output - Google Patents
Apparatus and method for performing attenuation to direct current offset of equipment output Download PDFInfo
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- CN101257466B CN101257466B CN2008101030070A CN200810103007A CN101257466B CN 101257466 B CN101257466 B CN 101257466B CN 2008101030070 A CN2008101030070 A CN 2008101030070A CN 200810103007 A CN200810103007 A CN 200810103007A CN 101257466 B CN101257466 B CN 101257466B
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Abstract
The invention provides a device for attenuating the output DC offset of the device and a method thereof. The device is connected with the input end and the output end of the device to be gaged, and forms a servo loop with the device to be gaged, which attenuates the e output DC offset of the device to be gaged through the servo loop, wherein the device includes an integrator for detecting and receiving the DC offset signals to be gaged by the device, after the integral process on the DC offset signals, then the signals are fed back to the input end of the device to be gaged. The invention can automatically and effectively calibrate the output DC offset by the device without test and calibration, thereby calibrating the carrier leakage of the device.
Description
Technical field
The present invention relates to the electrical application technology field, relate in particular to a kind of apparatus and method that the direct current offset of equipment output is decayed.
Background technology
A kind of Wideband Code Division Multiple Access (WCDMA) inserts (WCDMA, Wideband Code Division MultipleAccess) structure of zero intermediate frequency transmitter as shown in Figure 1, in this zero intermediate frequency transmitter, digital to analog converter (DAC, Digital To Analog Converter), variable gain amplifier (VGA, variablegain amplifier), lowpass function filter (LPF, Low Pass Filter) there is direct current offset (DC offset) in, DC offset among above-mentioned DAC, VGA and the LPF exports to multiplier after superposeing in LPF.The DC offset of LPF output just becomes radio frequency output after modulating through multiplier, thus the carrier leak of causing.Therefore, in the design of WCDMA zero intermediate frequency transmitter, it is little that the DC offset that requires LPF to export will try one's best.
The method of the DC offset of the LPF output of a kind of WCDMA of minimizing zero intermediate frequency transmitter of the prior art is: the equivalence input DC offset penalty method of amplifier.Because the equivalence of usually employed with it operational amplifier of DCoffset (OP-amp, Operational amplifier) among DAC, VGA and LPF input DC offset is directly proportional.This method is given the variable difference tail current in DAC, VGA and the employed operational amplifier input of the LPF certain limit, by changing the difference tail current of DAC, VGA and the employed operational amplifier of LPF, change the equivalence input DC offset of operational amplifier, and then change the DC offset of LPF output.
In realizing process of the present invention, the inventor finds that there is following shortcoming at least in the method for above-mentioned prior art: this method need travel through each the possible difference tail current in the certain limit, measure the value of DC offset of the LPF output of each difference tail current correspondence, determine best difference tail current according to the value of minimum DC offset, need carry out detection calibration.Therefore, this method needs long time to the calibration process of DC offset.Because there are not absolute linear corresponding relation in the equivalence of operational amplifier input DC offset and difference tail current, therefore, be difficult to accurately to control the scope of the difference tail current of DAC, VGA and the employed operational amplifier of LPF, the design of DAC, VGA and LPF has been brought difficulty according to the calibration accuracy of DC offset.
Summary of the invention
The purpose of the embodiment of the invention provides a kind of apparatus and method that the direct current offset of equipment output is decayed, thereby can solve the prior art scheme calibration process of DC offset is needed long time, device design is brought the problem of difficulty.
The purpose of the embodiment of the invention is achieved through the following technical solutions:
A kind of device that the direct current offset of equipment output is decayed, described device links to each other with output with the input of the equipment of needs calibration, form servo loop with the described equipment of calibration that needs, by described servo loop the described direct-flow shifted signal of the equipment output of calibration that needs is decayed, comprises in the described device:
Integrator is used to detect and receive the direct-flow shifted signal of the equipment output of described needs calibration, this direct-flow shifted signal is carried out integral processing after, feed back to the described input that needs the equipment of calibration;
Transconductance cell is connected with the output of described integrator, the described input of the equipment of calibration that needs, the integral voltage of described integrator output is converted to integration current after, be transferred to the described equipment that calibrate of needing.
A kind of method that the direct current offset of equipment output is decayed, described method comprises:
Integrator receives the described direct-flow shifted signal that needs the equipment output of calibration, after this direct-flow shifted signal carried out integral processing, feed back to the described input that needs the equipment of calibration, described integrator links to each other with output with the input of the equipment of needs calibration, forms servo loop with the described equipment of calibration that needs;
After the integral voltage that transconductance cell is exported described integrator is converted to integration current, be transferred to the described equipment that needs calibration, described transconductance cell is connected with the output of described integrator, the described input of the equipment of calibration that needs.
The technical scheme that is provided by the invention described above embodiment as can be seen, the embodiment of the invention decays to the direct-flow shifted signal of equipment output by the servo loop that utilizes the integrator composition, thereby can carry out under the situation of detection calibration not needing, automatically the DC offset to equipment output calibrates effectively.
Description of drawings
Fig. 1 is the structural representation of prior art WCDMA zero intermediate frequency transmitter;
Fig. 2 is the embodiment of the invention two described a kind of application schematic diagrames of device in WCDMA zero intermediate frequency transmitter that the DC offset of LPF output is calibrated;
Fig. 3 is the logical spectrum curve schematic diagram of the band of the embodiment of the invention two described servo loops;
Fig. 4 is the structural representation of the operational amplifier in the embodiment of the invention two described integrators;
Fig. 5 is the structural representation of the transconductance cell in the embodiment of the invention two described integrators;
The application schematic diagram of device in WCDMA zero intermediate frequency transmitter that the DC offset to LPF output that Fig. 6 provides for the embodiment of the invention three calibrates;
A kind of direct current offset to equipment output that Fig. 7 provides for the embodiment of the invention carries out the process chart of Calibration Method.
Embodiment
Describe the embodiment of the invention in detail below in conjunction with accompanying drawing.
In the embodiment of the invention one, the input of integrator with the equipment of needs calibration linked to each other with output, described integrator and the described equipment of calibration that needs are formed servo loop, described integrator receives the described direct-flow shifted signal that needs the equipment output of calibration, after this direct-flow shifted signal carried out integral processing, feed back to the described input that needs the equipment of calibration.And the described direct-flow shifted signal of the equipment output of calibration that needs is decayed by described servo loop.
In described integrator, be provided with to have and be lower than the equivalence input direct current offset of setting numerical value, the operational amplifier that is higher than the gain of setting numerical value, by the equivalence input direct current offset and the gain of described operational amplifier, control attenuation and attenuation range that described servo loop is decayed to the direct-flow shifted signal of the described equipment output that need calibrate.
A kind of application schematic diagram of device in WCDMA zero intermediate frequency transmitter that the DC offset of LPF output is calibrated that the embodiment of the invention two provides as shown in Figure 2.
The device that the DC offset to LPF output that the foregoing description two provides calibrates comprises integrator and transconductance cell (Gm-cell), link to each other with output with the input of LPF respectively and LPF forms a servo loop (servo loop) with the logical function of band together.This servo loop can detect and receive the low frequency signal (comprising DC offset) of LPF output automatically, this low frequency signal is carried out integral processing after, feed back to the input of LPF, realize the DC offset of LPF output is carried out very big decay.
The logical spectrum curve of the band of above-mentioned servo loop as shown in Figure 3, in Fig. 3, abscissa represent frequency, the ordinate represents frequency response, i.e. the ratio of output frequency and incoming frequency, frequency response is low more, attenuation is just big more, f
1Be the output frequency of LPF, f
hBe high pass cut off frequency, as can be seen from Figure 3, f
hThe attenuation of following low frequency part is bigger, and the frequency part of this low frequency part and DC offset is corresponding, f
hNeed be provided with lowlyer, because in the zero intermediate frequency transmitter architecture, signal is distributed between the DC-f1 equally, big f
hThe signal of having decayed equally causes transmitter performance to descend.
Comprise operational amplifier, electric capacity and resistance in the above-mentioned integrator, the value of the equivalence input DC offset of this operational amplifier is low more, and above-mentioned servo loop is just big more to the attenuation of DC offset, and the DC offset of LPF output is just more little.The schematic diagram of the operational amplifier in the integrator that the embodiment of the invention two provides as shown in Figure 4, in order to reduce the equivalence input DC offset of the operational amplifier in the above-mentioned integrator, this operational amplifier is adopted the two-layer configuration of stratification, first order amplifier is for adopting the first order prime amplifier of ohmic load, because the matching of passive device is better, therefore, this first order amplifier can obtain less equivalence input DC offset, second level amplifier is for adopting the amplifier of accordion structure, when obtaining high output impedance, also obtain high gain.Therefore, the operational amplifier of this two-layer configuration has low-down equivalence input DC offset, very high output impedance, very high gain.The value of the resistance capacitance of described integrator (R-C) constant also is provided with greatlyyer.
In actual applications, for the sensitivity that guarantees transient response and the consistency of high pass cut off frequency, the resistance of above-mentioned integrator can be made switched circuit array (variable resistor).
The structure of above-mentioned transconductance cell as shown in Figure 5, this transconductance cell is connected the output of above-mentioned operational amplifier, i.e. the output of integrator.This transconductance cell has the very high input linearity, and high resistant is imported, the characteristic of high resistant output.Because what LPF adopted is the electric current input, the main effect of this transconductance cell is that the output voltage with integrator is converted to integration current, can not influence the gain and the load characteristic of the operational amplifier in the integrator simultaneously again.Because transconductance cell is the output of high resistant current-mode, so its output common mode level can be along with input common mode electrical level free floating in certain scope of LPF, the input and output common mode electrical level of transconductance cell can be inconsistent, thereby realized level conversion.
The feature of the characteristic of the high-gain of the operational amplifier in the above-mentioned integrator and the height of the above-mentioned transconductance cell input linearity, guaranteed that whole servo loop has very high gain, can tolerate the scope of the DC offset of the LPF output that bigger needs are calibrated.Simultaneously, the characteristic of the low-down equivalence input DC offset of the operational amplifier in the above-mentioned integrator has guaranteed that the DC offset of the LPF output after the calibration is very low, almost is equal to the equivalence input DC offset of the operational amplifier in the above-mentioned integrator.DC current gain by the operational amplifier in the described integrator, control the attenuation that described servo loop is decayed to the described direct-flow shifted signal that needs the equipment output of calibration, the value of resistance capacitance (R-C) constant by described integrator is controlled the attenuation range of described servo loop to the direct-flow shifted signal of the described equipment output that needs calibration.
The application schematic diagram of device in WCDMA zero intermediate frequency transmitter that the DC offset to LPF output that the embodiment of the invention three provides calibrates as shown in Figure 6.In this embodiment, with having lower output impedance, the operational amplifier that still must have low-down equivalence input DC offset replaces above-mentioned operational amplifier shown in Figure 4.Under this embodiment, do not need above-mentioned transconductance cell.The operation principle of this embodiment and the foregoing description two are basic identical, the DC offset of LPF output can be calibrated to lower scope.But the scope of the DC offset of the LPF output of the needs calibration that can tolerate and embodiment two-phase are than smaller.
Present embodiment is that the equipment that need calibrate is the example explanation with LPF, and in actual applications, the device that needs described in the embodiment of the invention to calibrate can also be the equipment in other analogue transmission passages such as VGA, DAC.In actual applications, the described attenuating device of a plurality of embodiment of the invention can also be linked to each other with equipment such as VGA, LPF, DAC respectively, the DC offset that respectively equipment such as VGA, LPF, DAC is exported calibrates simultaneously, perhaps more than two devices in the equipment in a described attenuating device of the embodiment of the invention and the analogue transmission passages such as VGA, LPF, DAC is linked to each other, carry out DC offset calibration.
The handling process of a kind of direct current offset to equipment output carries out Calibration Method that the embodiment of the invention provides comprises the steps: as shown in Figure 7
Step 71, the equipment that integrator and needs are calibrated link to each other, and form servo loop.
The input of integrator with the equipment of needs calibration linked to each other the transconductance cell of between the input of described integrator and the described equipment that need calibrate, can also contacting with output.Described integrator and the described equipment that needs calibration, and transconductance cell is formed servo loop.
Comprise operational amplifier, electric capacity and resistance in the above-mentioned integrator, this operational amplifier adopts the two-layer configuration of stratification, and first order amplifier has low-down equivalence input DC offset, and second level amplifier has very high gain.Therefore, the operational amplifier of this two-layer configuration has low-down equivalence input DC offset, very high output impedance, very high gain.
Above-mentioned transconductance cell has the very high input linearity, and high resistant is imported, the characteristic of high resistant output.The main effect of this transconductance cell is that the output voltage with integrator is converted to integration current.
Step 72, the described direct-flow shifted signal of the equipment output of calibration that needs is decayed by above-mentioned servo loop.
Integrator in the above-mentioned servo loop receives the described direct-flow shifted signal that needs the equipment output of calibration, this direct-flow shifted signal is carried out integral processing after, feed back to the described input that needs the equipment of calibration.
Described servo loop has the function of band pass filter, attenuation to the low frequency part of the frequency part of the DC offset that comprises equipment output is bigger, by the equivalence input direct current offset and the gain of described operational amplifier, control attenuation and attenuation range that described servo loop is decayed to the direct-flow shifted signal of the described equipment output that need calibrate.
After having passed through the attenuation processing of described servo loop, the DC offset of the equipment output after the calibration is very low, almost is equal to the equivalence input DC offset of the operational amplifier in the above-mentioned integrator.The characteristic of the high-gain of the operational amplifier in the above-mentioned integrator and above-mentioned feature of striding the height input linearity of unit, guaranteed that whole servo loop has very high gain, can tolerate the scope of the DC offset of equipment (such as the LPF) output that bigger needs are calibrated.
In sum, the embodiment of the invention can take multiple measurements in the value of the DC offset that does not need equipment such as LPF are exported, promptly do not need to carry out under the situation of detection calibration, automatically the DC offset to the output of equipment such as LPF calibrates effectively, realizes carrier wave leakage control performance preferably.
The embodiment of the invention can be tolerated bigger DC offset calibration range, thereby the DC offset requirement of having relaxed equipment such as LPF has reduced the design difficulty of equipment such as LPF.
The above; only for the preferable embodiment of the present invention, but protection scope of the present invention is not limited thereto, and anyly is familiar with those skilled in the art in the technical scope that the present invention discloses; the variation that can expect easily or replacement all should be encompassed within protection scope of the present invention.Therefore, protection scope of the present invention should be as the criterion with the protection range of claim.
Claims (7)
1. device that the direct current offset of equipment output is decayed, it is characterized in that, described device links to each other with output with the input of the equipment of needs calibration, form servo loop with the described equipment of calibration that needs, by described servo loop the described direct-flow shifted signal of the equipment output of calibration that needs is decayed, comprises in the described device:
Integrator is used to detect and receive the direct-flow shifted signal of the equipment output of described needs calibration, this direct-flow shifted signal is carried out integral processing after, feed back to the described input that needs the equipment of calibration;
Transconductance cell is connected with the output of described integrator, the described input of the equipment of calibration that needs, the integral voltage of described integrator output is converted to integration current after, be transferred to the described equipment that calibrate of needing.
2. the device that the direct current offset of equipment output is decayed according to claim 1 is characterized in that the linearity of described transconductance cell is higher than the numerical value of setting.
3. according to each described device that the direct current offset of equipment output is decayed of claim 1 to 2, it is characterized in that, comprise in the described integrator:
Operational amplifier adopts two-layer configuration, comprising: adopt the first order amplifier of ohmic load, this first order amplifier has the equivalence input direct current offset that is lower than setting numerical value; Adopt the second level amplifier of accordion structure, this second level amplifier has and is higher than the gain of setting numerical value.
4. the device that the direct current offset of equipment output is decayed according to claim 3 is characterized in that, also comprises in the described integrator: the switched circuit array.
5. the device that the direct current offset of equipment output is decayed according to claim 1, it is characterized in that, the described equipment that needs calibration comprises the equipment in the analogue transmission passage, and the equipment in the described analogue transmission passage comprises one of variable gain amplifier VGA equipment in the transmitter, lowpass function filter LPF equipment, digital to analog converter DAC equipment at least.
6. method that the direct current offset of equipment output is decayed is characterized in that described method comprises:
Integrator receives the direct-flow shifted signal of the equipment output that needs calibration, after this direct-flow shifted signal carried out integral processing, feed back to the described input that needs the equipment of calibration, described integrator links to each other with output with the input of the equipment of needs calibration, forms servo loop with the described equipment of calibration that needs;
After the integral voltage that transconductance cell is exported described integrator is converted to integration current, be transferred to the described equipment that needs calibration, described transconductance cell is connected with the output of described integrator, the described input of the equipment of calibration that needs.
7. the method that the direct current offset of equipment output is decayed according to claim 6 is characterized in that described method also comprises:
DC current gain by the operational amplifier in the described integrator, control the attenuation that described servo loop is decayed to the described direct-flow shifted signal that needs the equipment output of calibration, the value of the resistance capacitance constant by described integrator is controlled the attenuation range of described servo loop to the direct-flow shifted signal of the described equipment output that needs calibration; Described operational amplifier has the equivalence that is lower than setting numerical value and imports direct current offset, is higher than the gain of setting numerical value.
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| CN2008101030070A CN101257466B (en) | 2008-03-28 | 2008-03-28 | Apparatus and method for performing attenuation to direct current offset of equipment output |
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| CN2008101030070A CN101257466B (en) | 2008-03-28 | 2008-03-28 | Apparatus and method for performing attenuation to direct current offset of equipment output |
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| CN101257466B true CN101257466B (en) | 2011-12-28 |
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Families Citing this family (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US8073406B2 (en) * | 2008-12-16 | 2011-12-06 | Mediatek Inc. | Amplitude modulation circuit in polar transmitter and method for calibrating amplitude offset in polar transmitter |
| CN101860323B (en) * | 2010-05-11 | 2013-09-18 | 广州市广晟微电子有限公司 | Device, system and method for correcting direct current offset |
| CN103973249B (en) * | 2014-05-09 | 2017-01-25 | 华为技术有限公司 | Variable gain amplifier |
| CN106849892B (en) * | 2017-03-15 | 2023-08-25 | 浙江集速合芯科技有限公司 | Common-mode voltage regulating circuit of operational amplifier input end in switched capacitor circuit |
| CN113721129B (en) * | 2021-08-27 | 2023-11-17 | 厦门优迅高速芯片有限公司 | Testing method and related equipment for direct current offset compensation circuit of optical transceiver driving chip |
| CN114629560B (en) * | 2022-02-10 | 2023-08-01 | 江苏科大亨芯半导体技术有限公司 | On-line DC offset calibration system and method |
Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN1266262A (en) * | 1999-02-17 | 2000-09-13 | 松下电器产业株式会社 | Displacement control circuit and control method |
| US20050110550A1 (en) * | 2003-11-24 | 2005-05-26 | Qian Shi | DC offset cancellation in a direct-conversion receiver |
| CN101179543A (en) * | 2006-11-09 | 2008-05-14 | 财团法人工业技术研究院 | DC offset cancellation circuit |
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- 2008-03-28 CN CN2008101030070A patent/CN101257466B/en active Active
Patent Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN1266262A (en) * | 1999-02-17 | 2000-09-13 | 松下电器产业株式会社 | Displacement control circuit and control method |
| US20050110550A1 (en) * | 2003-11-24 | 2005-05-26 | Qian Shi | DC offset cancellation in a direct-conversion receiver |
| CN101179543A (en) * | 2006-11-09 | 2008-05-14 | 财团法人工业技术研究院 | DC offset cancellation circuit |
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