CN102255837A - Carrier leak elimination method for direct conversion transmitter - Google Patents
Carrier leak elimination method for direct conversion transmitter Download PDFInfo
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- CN102255837A CN102255837A CN2010106068048A CN201010606804A CN102255837A CN 102255837 A CN102255837 A CN 102255837A CN 2010106068048 A CN2010106068048 A CN 2010106068048A CN 201010606804 A CN201010606804 A CN 201010606804A CN 102255837 A CN102255837 A CN 102255837A
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Abstract
The invention belongs to the technical field of integrated circuit designing, and particularly relates to a carrier leak elimination method for a direct conversion transmitter. The method is used for estimating an optimal compensation value. In the method, a data collection, analysis and feedback system is involved, and comprises parts such as a data acquisition module, a calibration data generation module, a module to be detected, a data computing module and the like. In a compensation process, a two-point estimation method and a joint detection method are adopted to simultaneously compensate for DC offset between a path of in-phase differential signals and a path of orthogonal differential signals and greatly shorten an overall carrier leak calibration cycle compared with that of a conventional traversing method. By the method, the calibration time of the whole system can be greatly shortened, the complexity of the system can be reduced, system power consumption can be effectively reduced, and the running efficiency of the system in a calibration mode can be improved.
Description
Technical field
The invention belongs to the integrated circuit (IC) design technical field, be specifically related to the removing method of carrier leak in the Direct Conversion transmitter.
Background technology
In wireless communication transmitter, factor such as the Direct Conversion transmitter is simple because of it, performance is high and cost is low becomes the mainstream technology of design, but the DC maladjustment problem that this framework exists is one of its maximum defective.For instance, in Direct Conversion transmitter shown in Figure 1, comprise two digital to analog converters 110 and 120, two low pass filters 130 and 140, two up- conversion mixers 150 and 170, one RF variable gain amplifiers of 160, one local oscillator generators 180 and antenna 190.When transforming to radio frequency part, launches by homophase and the quadrature two paths of signals modulator by transmitter, because the existence of factors such as technology mismatch makes digital to analog converter 1 and 2.Low pass filter 3 and 4 and the differential signal of frequency mixer 5 and 6 between exist small direct current mismatch Δ V
IWith Δ V
QThis mismatch transforms to the transmitter carrier frequency after via the modulator conversion and makes and carrier component occurs at the output spectrum without any transmitter under the input signal, this component has directly influenced error vector magnitude (the Error Vector Magnitude of one of most important parameters of transmitter, EVM), also can have influence on simultaneously the gain controlling of transmitter, carrier leak will have influence on the power control of transmitter under low power output, therefore must eliminate carrier leak in transmitter.
Existing method of this having been carried out the compensation elimination in the prior art promptly compensates DC maladjustment to eliminate carrier leak by applying anti-phase small quantity.Its algorithm can be the traversal method, according to the traversal method homophase and quadrature two-way is carried out Calibration Method, need just can finish primary calibration through (N+1) power of 2; Efficiency of algorithm based on dichotomy (Binary Search) is higher, but the required precision of this method alignment time along with compensation increases and increases, and this method need apply respectively homophase and quadrature two-way, such as calibration steps is the N position, then need 2N calibration just can finish primary calibration, this also needs to consume the more time; Also have a kind of compensation mechanism that obtains based on four computational methods, calculate best offset then by four measured values and can satisfy system requirements, so this algorithm does not require to prolong the alignment time with calibration accuracy.
Summary of the invention
The object of the present invention is to provide the removing method of carrier leak in the few Direct Conversion transmitter of a kind of efficiency of algorithm height, alignment time.
The removing method of carrier leak in the Direct Conversion transmitter provided by the invention is a kind of method of estimating the optimal compensation value.This method only need adopt twice calculating and and detection combine i.e. decidable optimal compensation vector value.The advantage of this method is: the first, and the number of times of calibration is not subjected to the influence of calibration accuracy, and promptly calibration accuracy can not influence the time of calibration; The second, only need twice main amount of calculation, therefore both reduced operation times, also further saved the time of computing.
The invention provides a kind of combination and calculate the method for the The optimal compensation direct current vector of eliminating with the Fast estimation carrier leak that detects, is the implementation process of schematic view illustrating the inventive method with Fig. 2.The DC compensation vector value of an inphase/orthogonal of data processing module 240 initial settings at first, calibration data generation module 210 is converted into the direct current offset vector value corresponding with side circuit with this vector value, and this value can be a magnitude of voltage, also can be current value.Calibration data generation module 210 is given module 220 to be measured by applying this voltage (perhaps current value), module 220 to be measured can produce a corresponding carrier leakage power value under this direct current offset vector, the carrier power of this leakage detects through data acquisition module 230, this module is converted into a magnitude of voltage with performance number, and this magnitude of voltage is converted to digital signal feeds back to data processing module 240, data processing module 240 has obtained the carrier leak information under specific inphase/orthogonal DC compensation vector thus.Then data processing module 240 is set the compensating direct current vector value of another group inphase/orthogonal, through having obtained the carrier leak information under this vectorial offset behind the foregoing feedback procedure.Obtained the outgoing carrier leakage situation under two kinds of different input offset direct current vectors thus, data processing module can calculate needed best DC compensation vector value in the actual alignment process by an equation group.In addition, owing in the group process of solving an equation, can produce the situation that a plurality of vectors are separated, need to set a detection threshold that satisfies calibration requirements this moment, these vectors that meet equation group are separated by calibration data generation module 210 generate corresponding virtual voltages or current value is sent in the module 220 to be measured, detection module 230 detects these vectors simultaneously and separates corresponding carrier leakage power and convert actual voltage to, data processing module 240 judges whether this voltage reaches the detection threshold that alignment requirements is set, if satisfy then current vector separated and be set at optimal compensation direct current offset vector, other vector is separated and is given up, and finishes to this calibration process.
Among the present invention, as shown in Figure 1, the position of compensation is not limited to the digital to analog converter 110 and 120 in the transmitter, also can be modulator 150 and 160 or baseband filter 130 and 140; Can be wherein a kind of, also can be wherein several combinations.
Among the present invention, actual crucial compensation calculation process is twice, but does not comprise by other because of calculation times that needs produced such as judgement, checkings.
Among the present invention, can be applied to GSM, GPRS, EDGE, also can be applied to TD-SCDMA, WCDMA, CDMA2000 and LTE, the WiMax etc. of 3G (Third Generation) Moblie transmitter system based on the Direct Conversion framework.
Among the present invention, during the carrier leak information of each compensation vector correspondence of Practical Calculation, two specific vector values that are not limited among the present invention to be mentioned are not limited in the real process simultaneously to the sequential processing method in processing methods such as the required close approximation of carrying out of crucial calculating formula and the implementation process.
Description of drawings
Fig. 1 is a Direct Conversion transmitter schematic diagram.
Fig. 2 is the schematic diagram that the carrier leak calibration is implemented.
Fig. 3 is based on a kind of specific algorithm schematic diagram of the inventive method.
Number in the figure: 110,120 digital to analog converters, 130,140 low pass filters, 150,160 up-conversion mixers,
170 local oscillation signal generators, 180 RF variable gain amplifiers, 190 antennas, 210 calibration data generation modules, 220 modules to be measured, 230 data acquisition modules, 240 data computation module.
Embodiment
Below by shown in Figure 2, the present invention is described in further detail with an instantiation.
The The optimal compensation direct current vector of supposing inphase/orthogonal branch road in the Direct Conversion emission be (X0, Y0), for inphase/orthogonal branch road direct current vector arbitrarily (X, Y), the performance number P that outgoing carrier leaks
LeakCan be expressed as:
Here considered that at load impedance be situation under 50 ohm, performance number unit is dBm.The process of whole calibration algorithm exactly by detect and Calculation Method find certain vector (X, Y), make this vector under certain calibration target level very approaching optimum DC compensation vector value (X0, Y0).
Data acquisition module 230 is to have comprised that one is converted to the circuit and the analog to digital converter of voltage with performance number in Fig. 2, and voltage becomes digital signal and gives data computation module 240 through after the analog-to-digital conversion.
The transfer characteristic of data acquisition module 230 satisfies relational expression:
Equation (2)
V wherein
LeakBe the numerical value voltage of data converter output, V
SlopeBe the rate of change of power and voltage transitions, its unit is V/dBm, P
MinBe the desired carrier leak desired value that reaches of calibration system, V
MinBe that data conversion module 230 is at input P
MinFollowing corresponding voltage value.(X1, Y1) the feasible detection voltage of the carrier leakage power correspondence that examining system 220 is exported for the treatment of is less than V when one group of DC compensation vector
MinThe time, this compensation vector is exactly the one group of compensating direct current vector that meets the calibration expection.
At first select the starting point of a calibration, for simplicity, might as well select initial point, its inphase/orthogonal direct current vector point is (0,0), and the carrier leak power output is exactly like this:
If P
1Be a constant, equation (2) is exactly the equation of a circle, so apart from the The optimal compensation vector (X0, Y0) any one on same distance point all satisfies equation (3), and supposes that this radius is R1, then R1 satisfies:
By equation (2) as can be known, the relation of R1 and data acquisition module 230 output voltages is:
Equation (5)
Here V
1Be P
1Corresponding output detects voltage, and the unit of R1 is V.
Then select second test point (X1 Y1), for the convenience of calculating, gets Y1=0, and X1=R1 promptly as shown in Figure 3, has following formula to set up so:
So have second radius R 2 to set up again, its expression formula is:
According to equation (2), have the pass of R2 and data acquisition module 230 output voltages to be equally:
Here V
2Be P
2Corresponding output detects voltage, and the unit of R2 is V.In order to guarantee that equation group has real solution, data computation module 240 needs to judge the value of V2 and the size of V1, if V2, then can reselect the process that (R1,0) point repeats second test point greater than V1.
So solve an equation (3) and (6) can obtain (X0, Y0) about (R1, R2) equational separating:
Wherein R1 and R2 are determined by equation (5) and (8), Pmin is predefined value, Vmin is the detection magnitude of voltage corresponding with Pmin, Vslope is the transfer characteristic of data acquisition module 230 itself, these three parameters all are known, and V1 and V2 are the values that data detection module 230 obtains in the calibration process, so can obtain the value of R1 and R2 by equation (5) and (8), thereby obtain (X0, value Y0) by equation (9).
But equation (9) has two situations of separating, and actual conditions generally can only have a requirement of satisfying calibration accuracy in the two, so also need last step to this: calibration data generation module 210 can generate and (X0 according to equation (9), + Y0) corresponding DC compensation magnitude of voltage, and it is sent in the module 220 to be measured, therefore module 220 to be measured can respond a carrier leakage value, if the carrier leakage power corresponding voltage value of data detection module output 230 this moment is less than target voltage Vmin, (X0 then, + Y0) this calculated value is exactly a The optimal compensation direct current vector, and another meets (the X0 that separates of design conditions in the equation (7),-Y0) do not satisfy condition, should give up; Otherwise (X0 ,-Y0) be exactly qualified The optimal compensation direct current vector.
To sum up, in Fig. 2, concrete steps of the present invention are, data computation module 240 is set certain inphase/orthogonal DC compensation vector point (X, Y), this vector value generates the bucking voltage value corresponding with this vector by calibration data generation module 210, and (Vx Vy) gives module 220 to be measured, and therefore module 220 to be measured produces corresponding carrier leakage power P
Leak, then data acquisition module 230 is converted to magnitude of voltage V by equation (2) with this performance number
LeakAnd digitlization feeds back to data computation module 240, after twice above-mentioned circulation, data computation module 240 obtains twice carrier leak corresponding voltage value V1 and V2, in view of the above data computation module 240 directly by equation (9) comprise equation (5) and equation (8) calculate optimal compensation direct current vector (X0, Y0).Because the separating of optimal vector has two and separates, then will be wherein one to separate and be updated in the module 220 to be measured, data detection module 230 detects corresponding power and is converted to voltage, if this voltage is less than predefined magnitude of voltage V
Min, then this to separate be exactly optimum DC compensation vector, another is separated and need give up; Otherwise another is separated is exactly optimum DC compensation vector.
Claims (3)
1. carrier leak removing method in the Direct Conversion transmitter is characterized in that concrete steps are:
The DC compensation vector value of an inphase/orthogonal of data processing module (240) initial setting at first, calibration data generation module (210) is converted into the direct current offset vector value corresponding with side circuit with this vector value, and this value is magnitude of voltage or current value; Calibration data generation module (210) is given module to be measured (220) by applying this voltage or current value, module to be measured (220) produces a corresponding carrier leakage power value under this direct current offset vector, the carrier power of this leakage detects through data acquisition module (230), performance number is converted into a magnitude of voltage, and this magnitude of voltage is converted to digital signal feeds back to data processing module (240; Data processing module (240) obtains the carrier leak information under specific inphase/orthogonal DC compensation vector thus;
Then data processing module (240) is set the compensating direct current vector value of another group inphase/orthogonal, through having obtained the carrier leak information under this vectorial offset behind the foregoing feedback procedure; Obtain two kinds of outgoing carrier leakage situation under the different input offset direct current vectors thus, data processing module (240) calculates needed best DC compensation vector value in the actual alignment process by an equation group;
These vectors that meet equation group are separated by calibration data generation module (210) generate corresponding virtual voltage or current value is sent in the module to be measured (220), detection module (230) detects these vectors simultaneously and separates corresponding carrier leakage power and convert actual voltage to, data processing module (240) judges whether this voltage reaches the detection threshold that alignment requirements is set, if satisfy then current vector separated and be set at optimal compensation direct current offset vector, other vector is separated and is given up, and finishes to this calibration process.
2. method according to claim 1 is characterized in that the position that compensates is a kind of in the digital to analog converter, modulator, baseband filter in the Direct Conversion transmitter, or wherein several combinations.
3. method according to claim 1 is characterized in that: the The optimal compensation direct current vector of supposing inphase/orthogonal branch road in the Direct Conversion emission be (X0, Y0), for inphase/orthogonal branch road direct current vector arbitrarily (X, Y), the performance number P that outgoing carrier leaks
LeakBe expressed as:
Performance number unit is dBm; The process of entire method is exactly by detecting and calculate, find certain vector (X, Y), make this vector under certain calibration target level very near optimum DC compensation vector value (X0, Y0);
Data acquisition module (230) comprises that one is converted to the circuit and the analog to digital converter of voltage with performance number, and voltage becomes digital signal and gives data computation module (240) through after the analog-to-digital conversion;
The transfer characteristic of data acquisition module (230) satisfies relational expression:
V wherein
LeakBe the numerical value voltage of data converter output, V
SlopeBe the rate of change of power and voltage transitions, its unit is V/dBm, P
MinBe the desired carrier leak desired value that reaches of calibration system, V
MinBe that data conversion module (230) is at input P
MinFollowing corresponding voltage value; (X1 Y1) makes the detection voltage of carrier leakage power correspondence of module to be measured (220) output less than V when one group of DC compensation vector
MinThe time, this compensation vector is exactly the one group of compensating direct current vector that meets the calibration expection;
At first select an initial point as first test point, its inphase/orthogonal direct current vector point is (0,0), and the carrier leak power output is exactly like this:
P
1Be a constant, equation (2) is the equation of a circle, so apart from the The optimal compensation vector (X0, Y0) any one on same distance point all satisfies equation (3), and supposes that this radius is R1, then R1 satisfies:
By equation (2) as can be known, the relation of R1 and data acquisition module (230) output voltage is:
Here V
1Be P
1Corresponding output detects voltage, and the unit of R1 is V;
Then select second test point (X1 Y1), gets Y1=0, and X1=R1 has following formula to set up so:
Equation (6)
So have second radius R 2 to set up again, its expression formula is:
Equation (7)
According to equation (2), have the pass of R2 and data acquisition module (230) output voltage to be equally:
Here V
2Be P
2Corresponding output detects voltage, and the unit of R2 is V; Data computation module (240) needs to judge the value of V2 and the size of V1, if V2, then can reselect the process that (R1,0) point repeats second test point greater than V1;
Solve an equation (3) and (6), obtain (X0, Y0) about (R1, R2) equational separating:
Equation (9);
Wherein R1 and R2 are determined by equation (5) and (8), Pmin is predefined value, Vmin is the detection magnitude of voltage corresponding with Pmin, Vslope is the transfer characteristic of data acquisition module 230 itself, these three parameters all are known, and V1 and V2 are the values that data detection module in the calibration process (230) obtains; Obtain the value of R1 and R2 by equation (5) and (8), thereby obtain (X0, value Y0) by equation (9);
At last, (210 according to equation (9) generation and (X0 for the calibration data generation module, + Y0) corresponding DC compensation magnitude of voltage, and it is sent in the module to be measured (220), module to be measured (220) can respond a carrier leakage value, if the carrier leakage power corresponding voltage value of data detection module (230) output this moment is less than target voltage Vmin, (X0 then, + Y0) be exactly The optimal compensation direct current vector, and another meets (the X0 that separates of design conditions in the equation (7),-Y0) do not satisfy condition, should give up; Otherwise (X0 ,-Y0) be exactly qualified The optimal compensation direct current vector.
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Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
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| CN103457616A (en) * | 2013-09-03 | 2013-12-18 | 广州润芯信息技术有限公司 | Orthogonal mismatch calibration method and device of direct frequency conversion transmitter |
| CN105629274A (en) * | 2015-12-25 | 2016-06-01 | 中国电子科技集团公司第五十四研究所 | Carrier suppression measurement method of short burst spread spectrum signal |
| CN107819712A (en) * | 2016-09-12 | 2018-03-20 | 中兴通讯股份有限公司 | Local-oscillator leakage automatic calibrating method and device |
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| CN101072040A (en) * | 2007-06-13 | 2007-11-14 | 鼎芯通讯（上海）有限公司 | Method and device for suppressing carrier leakage |
| CN101189812A (en) * | 2005-04-22 | 2008-05-28 | Ttpcom有限公司 | Assessing the performance of radio devices |
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| US20040230393A1 (en) * | 2003-05-14 | 2004-11-18 | Peter Andersson | Fast calibration of electronic components |
| CN1649334A (en) * | 2004-01-30 | 2005-08-03 | 日本电气株式会社 | Apparatus and method for adjusting quadrature modulator, communication apparatus and program |
| CN101189812A (en) * | 2005-04-22 | 2008-05-28 | Ttpcom有限公司 | Assessing the performance of radio devices |
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Cited By (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN103457616A (en) * | 2013-09-03 | 2013-12-18 | 广州润芯信息技术有限公司 | Orthogonal mismatch calibration method and device of direct frequency conversion transmitter |
| CN103457616B (en) * | 2013-09-03 | 2015-05-27 | 广州润芯信息技术有限公司 | Orthogonal mismatch calibration method and device of direct frequency conversion transmitter |
| CN105629274A (en) * | 2015-12-25 | 2016-06-01 | 中国电子科技集团公司第五十四研究所 | Carrier suppression measurement method of short burst spread spectrum signal |
| CN105629274B (en) * | 2015-12-25 | 2017-11-14 | 中国电子科技集团公司第五十四研究所 | A kind of carrier suppression measuring method of short burst spread-spectrum signal |
| CN107819712A (en) * | 2016-09-12 | 2018-03-20 | 中兴通讯股份有限公司 | Local-oscillator leakage automatic calibrating method and device |
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Application publication date: 20111123 |