CN101674087B - Method for obtaining channel mismatching error of time alternative ADC system - Google Patents

Method for obtaining channel mismatching error of time alternative ADC system Download PDF

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CN101674087B
CN101674087B CN200910167760A CN200910167760A CN101674087B CN 101674087 B CN101674087 B CN 101674087B CN 200910167760 A CN200910167760 A CN 200910167760A CN 200910167760 A CN200910167760 A CN 200910167760A CN 101674087 B CN101674087 B CN 101674087B
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amp
error
output sequence
channel
adc system
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CN200910167760A
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CN101674087A (en
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王志刚
田书林
张昊
王猛
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电子科技大学
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Abstract

The invention discloses a method for obtaining channel mismatching error of a time alternative ADC system; the time alternative ADC system samples a sine-input signal x(t) to obtain the actual output sequence Yi equaling to yi<0>, yi<1>, and the like, yi<N minus 1> of each channel, wherein i is equal to 0, 1, and the like, M minus 1; a certain channel s selected as a reference channel and an interpolation function is used for interpolating the actual output sequence thereof to obtain the output sequence without mismatching error of rest channels relative to the reference channel; a sine fitting method is respectively adopted to fit the output sequence without mismatching error of the rest channels and the actual output sequence; and the mismatching error of the rest channels relative to the reference channel is obtained according to the sampling model yi<n> equaling to gi multiplied by (nMT<s> plus iT<s> plus Delta t<i>) plus os<i> of the time alternative ADC system. The purposes of the invention are realized by adopting interpolation and sine fitting in the method for obtaining channel mismatching error of a time alternative ADC system; moreover, gain, deflection and time delay errors are considered, thus guaranteeing the precision of the obtained channel mismatching error.

Description

A kind of acquisition methods of channel mismatching error of time alternative ADC system

Technical field

The present invention relates to high-speed, high precision Sampling techniques field, specifically, relate to a kind of acquisition methods of channel mismatching error of time alternative ADC system.

Background technology

Many digital signal processing appts like radar base station or VDSL modulator-demodulator, need analog to digital converter (ADC) to have higher sampling rate.In order to obtain sufficiently high sample rate, can adopt time alternative ADC (TIADC) system to realize.

Time alternative ADC system is made up of the ADC sampling channel that the M group is parallel to each other; Each ADC operating frequency is the 1/M of the total sample frequency of TIADC system; Mode with alternating sampling is sampled to input signal; Therefore, the M that the sampling rate of TIADC system can reach the high sampling rate of single channel ADC doubly, this method can improve the sample rate of analog to digital converter simply and effectively.

Yet if does not wait at the interval between the TIADC system neighbouring sample point, when promptly each channel clock postponed not match, the output of system can produce error.When frequency input signal is systematic sampling rate one half, be in least significant bit (LSB) (LSB) half the with this ERROR CONTROL, then the error in sampling interval must be lower than the sampling period (π 2 n) -1Doubly, wherein n is the sampling system number of significant digit, and such as the system for a 6bit, the error in sampling interval must be lower than 0.5% of the sampling period, and when sample frequency was 4GHz, this error must be controlled in 1.2 psecs.

Except the clock delay mismatch error, gain between each passage of TIADC system and skew mismatch error also are that error is introduced in the output of system.Gain, skew and clock mismatch error are to the influence of TIADC system output; Show on the output spectrum it then is the distortion spectrum that produces except that frequency input signal; This type distortion spectrum has reduced the SFDR (SFDR) of TIADC system, makes the resolution of TIADC system be lower than single channel ADC.

If can calculate the mismatch error of each passage of TIADC system, just can calibrate or compensate the dateout of each passage according to these errors, reduce mismatch error, reduce the output spectrum distortion, improve the SFDR of system.The acquisition methods of present most mismatch errors all is to set up on one or both the basis in ignoring gain, skew and clock delay mismatch error, and just there is error in the mismatch error of obtaining through these methods itself; In addition, some acquisition methods also needs the cooperation of additional circuit such as digital filter to accomplish, and the adding of additional circuit not only can bring new error, and can't obtain the mismatch error of ultrahigh speed TIADC system channel.

Summary of the invention

The objective of the invention is to overcome the deficiency of prior art, a kind of acquisition methods of more precise time alternative ADC system channel mismatching error is provided.

For realizing above-mentioned purpose, the acquisition methods of channel mismatching error of time alternative ADC system of the present invention may further comprise the steps:

(1), uses sinusoidal signal generator to produce frequency and be f InSinusoidal input signal x (t), time alternative ADC system is sampled to this sinusoidal input signal x (t), obtains the actual output sequence Y of each passage i=[y i[0], y i[1] ..., y i[N-1]] i=0,1...M-1, wherein, M is the port number of time alternative ADC system;

(2), to choose certain passage be reference channel, utilizes interpolating function to its actual output sequence interpolation, obtains rest channels does not have mismatch error with respect to reference channel output sequence;

(3), output sequence and actual output sequence that rest channels is not had a mismatch error adopt sinusoidal fitting process to carry out match respectively, constructs the output sequence sinusoidal expression and the actual output sequence sinusoidal expression of no mismatch error of the rest channels of match;

(4), there are not the output sinusoidal expression of mismatch error and the sampling model y of actual output sinusoidal expression and time alternative ADC system according to the rest channels of match i[n]=g iX (nMT s+ iT s+ Δ t i)+os i, obtain the mismatch error of rest channels, wherein g with respect to reference channel i, Δ t iAnd c iThe gain, the sampling clock that are respectively time alternative ADC system i passage postpone and skew T sBe the sampling period of time alternative ADC system.

The objective of the invention is to realize like this, in the acquisition methods of channel mismatching error of time alternative ADC system, adopt interpolation, sinusoidal match, and considered gain, skew and clock delay error, guaranteed the precision of the channel mismatching error of acquisition; Interpolation to the reference channel sequence adopts interpolating function to carry out, and does not need actual filtering interpolation circuit, has guaranteed the accuracy of interpolating sequence, and can not introduce new error; Directly the time alternative ADC system output sequence of storing is handled, do not needed the taking into account system operating rate, therefore can measure the ultrahigh speed time alternative ADC system; Need in time alternative ADC system, not add extra circuit; Except that having reduced overhead; Also make obtaining of channel mismatching error of time alternative ADC system that this method can be used for having designed, and can not introduce new error, reached the purpose of accurate measurement.

Description of drawings

Fig. 1 is the electric theory diagram under a kind of embodiment of the acquisition methods of channel mismatching error of time alternative ADC system of the present invention;

Fig. 2 is the sampling model of i ADC passage of time alternative ADC system shown in Figure 1;

Fig. 3 is a time alternative ADC system shown in Figure 1 when having quantization error, the relative error curve chart of channel mismatching error that obtains and physical channel mismatch error;

Fig. 4 is a time alternative ADC system shown in Figure 1 when having quantization error and passage random error, the relative error curve chart of channel mismatching error that obtains and physical channel mismatch error;

Fig. 5 is that the sinusoidal input signal that sinusoidal signal generator shown in Figure 1 produces comprises harmonic distortion, when time alternative ADC system exists quantization error and passage random error, and the relative error curve chart of channel mismatching error that obtains and physical channel mismatch error;

Fig. 6 be the channel mismatching error that obtains according to the present invention to the output waveform figure before and after the high-speed digitization appearance passage output calibration, wherein, Fig. 6 a is the output waveform figure when not calibrating, Fig. 6 b is the output waveform figure after the calibration.

Embodiment

Describe below in conjunction with the accompanying drawing specific embodiments of the invention, so that understand the present invention better.What need point out especially is that in the following description, when perhaps the detailed description that adopts known function and design can desalinate main contents of the present invention, these were described in here and will be left in the basket.

Embodiment

Fig. 1 is the electric theory diagram under a kind of embodiment of the acquisition methods of channel mismatching error of time alternative ADC system of the present invention

In the present embodiment, as shown in Figure 1, the hardware that the acquisition methods of channel mismatching error of time alternative ADC system relates to comprises three parts: the time alternative ADC system 2 of sinusoidal signal generator 1, M passage and the computer 3 of software for mathematical computing MATLAB is housed.The passage label of the time alternative ADC system 2 of M passage is followed successively by 0,1 from top to bottom ..., M-1, clock signal directly provides passage ADC 0, delay time 1,2 successively then ..., after M-1 sampling period, offer passage ADC respectively 1, passage ADC 2..., passage ADC M-1

The operating frequency of M channel time alternative ADC system 2, promptly the frequency of clock signal is f s, the sampling period of time alternative ADC system is T s, T s=1/f sUse sinusoidal signal generator 2 to produce frequency and be f In=Jf s/ N<f sThe sinusoidal input signal x (t) of/2M; Wherein N is single channel sample point number; J and N are relatively prime, satisfy the input signal of the sinusoidal signal x (t) of said frequencies requirement as M channel time alternative ADC system 2, can make sinusoidal input signal x (t) obtain phase place [0; 2 π] go up even distribution N different sampled point, help improving computational accuracy.

Sample with time alternative ADC system 2 pairs of inputs sinusoidal signal x (t), each passage is got N=3000 sampled point, with the actual output sequence Y of each passage i=[y i[0], y i[1] ..., y i[N-1]] i=0,1 ... M-1 deposits in and treats down step processing, wherein y in the computer 3 that software for mathematical computing MATLAB is housed i[n]=g iX (nMT s+ iT s+ Δ t i)+os iChoosing the 0th passage is reference channel, with the actual output sequence Y of 0 passage 0=[y 0[0], y 0[1] ..., y 0[N-1]] import among the software for mathematical computing MATLAB, with int erp (Y 0, M) function is to the actual output sequence Y of 0 passage 0=[y 0[0], y 0[1] ..., y 0[N-1]] do M times of interpolation, obtain the output sequence that there is not channel mismatching error in M channel time alternative ADC system 2 rest channels Y ^ i = [ y ^ i [ 0 ] , y ^ i [ 1 ] , &CenterDot; &CenterDot; &CenterDot; , y ^ i [ N - 1 ] ] , i = 1,2 &CenterDot; &CenterDot; &CenterDot; M - 1 .

With SIN function Acos (2 π f Int n)+Bsin (2 π f Int nThe actual output of)+C match rest channels respectively and do not have the output sequence of channel mismatching error, the sinusoidal expression parameter that A wherein, B, C need confirm during for match.If The output sequence that does not have channel mismatching error for passage i The sinusoidal expression parameter, A i, B i, C iBe the actual output sequence Y of passage i iThe sinusoidal expression parameter.Sampling model y according to time alternative ADC system i[n]=g iX (nMT s+ iT s+ Δ t i)+os i, can obtain:

g i { cos ( 2 &pi; f in t n ) [ A ^ i cos ( 2 &pi; f in &Delta; t i ) + B ^ i sin ( 2 &pi; f in &Delta;t i ) ]

- sin ( 2 &pi; f in t n ) [ A ^ i sin ( 2 &pi; f in &Delta; t i ) - B ^ i cos ( 2 &pi; f in &Delta;t i ) ] } + C ^ i + os i

= A i cos ( 2 &pi; f in &Delta; t i ) + B i sin ( 2 &pi; f in &Delta;t i ) + C i

At last, obtaining passage i with respect to the mismatch error of passage 0 is:

&Delta; t i = a tan ( A i B ^ i - A ^ i B i A i A ^ i + B ^ i B i ) / 2 &pi; f in , g i = A i A ^ i cos ( 2 &pi; f in &Delta;t ) + B ^ i sin ( 2 &pi; f in &Delta;t ) , os i = C i - C ^ i

Time alternative ADC system 2 offset of sinusoidal input signal x (t) sample, and each passage is got N=3000 sampled point again, repeat above-mentioned steps repeatedly, with the channel mismatching error Δ t that repeatedly obtains i, g i, os iAverage respectively, to reduce the influence of quantization error in the system, random error the channel mismatching error precision obtained.

Fig. 2 is the sampling model of i ADC passage of time alternative ADC system shown in Figure 1

As shown in Figure 2, the sampling model of the single passage of time alternative ADC system, the gain of its i ADC passage, skew and clock delay error are respectively g i, os i, Δ t i, the actual output sequence of i ADC channel sample acquisition is:

y i[n]=g ix(nMT s+iT s+Δt i)+os i

In this enforcement, the computational accuracy of the channel mismatching error of acquisition is used the relative error formula:

E ^ - E E &times; 100 %

Represent; Wherein the channel mismatching error of method acquisition of the present invention is adopted in expression, and E is the physical channel mismatch error.

Fig. 3 is a time alternative ADC system shown in Figure 1 when having quantization error, the relative error curve chart of channel mismatching error that obtains and physical channel mismatch error

In this enforcement; When only there is the 8bit quantization error in time alternative ADC system; Can find out that by Fig. 3 channel mismatching error that the present invention calculates can be controlled in 4% with respect to the deviation of physical channel mismatch error; And along with increasing of the number of times of the channel mismatching error that repeats to obtain, deviation is further dwindled.

Fig. 4 is a time alternative ADC system shown in Figure 1 when having quantization error and passage random error, the relative error curve chart of channel mismatching error that obtains and physical channel mismatch error

In the present embodiment; Have 8bit quantization error and passage random error in the time alternative ADC system, and random error to obey average be 0 variance when being 0.01 Gaussian distribution, the precision of the channel mismatching error of acquisition; Can find out by Fig. 4; Deviation with respect to the actual error channel mismatching error can be controlled in 5%, and along with the increasing of the number of times of the channel mismatching error that repeats to obtain, deviation is further dwindled.

Fig. 5 is that the sinusoidal input signal that sinusoidal signal generator shown in Figure 1 produces comprises harmonic distortion, when time alternative ADC system exists quantization error and passage random error, and the relative error curve chart of channel mismatching error that obtains and physical channel mismatch error

In the present embodiment; Have harmonic distortion among the sinusoidal input signal x (t), existing 8bit quantization error and passage random error to obey average in the time alternative ADC system is 0 variance when being 0.01 Gaussian distribution, the precision of the channel mismatching error of acquisition; Can find out by Fig. 5; Deviation with respect to the physical channel mismatch error can be controlled in 7%, and along with the increasing of the number of times of the channel mismatching error that repeats to obtain, deviation is further dwindled.

Fig. 6 be the channel mismatching error that obtains according to the present invention to the output waveform figure before and after the high-speed digitization appearance passage output calibration, wherein, Fig. 6 a is the output waveform figure when not calibrating, Fig. 6 b is the output waveform figure after the calibration.

The channel mismatching error of time alternative ADC system that the present invention is obtained is applied in actual 12bit, the calibration of 400MSPs high-speed digitization appearance.This digitizer mainly is made up of two channel time alternative ADC systems; Because high-speed digitization appearance channel mismatching error is unknown; In order effectively to verify the high accuracy of the channel mismatching error that the present invention obtains; The channel mismatching error that can obtain according to the present invention is exported digitizer and is calibrated, and observes the performance that whether can improve the high-speed digitization appearance.Fig. 6 has shown the channel mismatching error that obtains according to the present invention to the output waveform before and after the high-speed digitization appearance passage output calibration, can find out calibration by Fig. 6 a before because the influence of channel mismatching error, the sinusoidal waveform of output is unsmooth jagged; Can find out the channel mismatching error that obtains according to the present invention by Fig. 6 b, after system calibration, the sinusoidal waveform of output is more level and smooth, explains that channel mismatching error has reduced, and therefore verifies validity of the present invention.

Although above the illustrative embodiment of the present invention is described; So that the technical staff of present technique neck understands the present invention, but should be clear, the invention is not restricted to the scope of embodiment; To those skilled in the art; As long as various variations appended claim limit and the spirit and scope of the present invention confirmed in, these variations are conspicuous, all utilize innovation and creation that the present invention conceives all at the row of protection.

Claims (2)

1. the acquisition methods of a channel mismatching error of time alternative ADC system is characterized in that, may further comprise the steps:
(1), uses sinusoidal signal generator to produce frequency and be f InSinusoidal input signal x (t), time alternative ADC system is sampled to this sinusoidal input signal x (t), obtains the actual output sequence Y of each passage i=[y i[0], y i[1] ..., y i[N-1]] i=0,1 ... M-1, wherein, N is single channel sample point number, M is the port number of time alternative ADC system;
(2), choosing certain passage is reference channel; Utilize interpolating function to its actual output sequence interpolation, obtain rest channels does not have mismatch error with respect to reference channel output sequence
(3), output sequence and actual output sequence that rest channels is not had a mismatch error adopt sinusoidal fitting process to carry out match respectively, constructs the output sequence sinusoidal expression and the actual output sequence sinusoidal expression of no mismatch error of the rest channels of match;
The SIN function that described sinusoidal fitting process adopts is: Acos (2 π f Int n)+Bsin (2 π f Int nThe sinusoidal expression parameter that)+C, A wherein, B, C need confirm during for match;
(4), there are not the output sequence sinusoidal expression of mismatch error and the sampling model y of actual output sinusoidal expression and time alternative ADC system according to the rest channels of match i[n]=g iX (nMT s+ iT s+ Δ t i)+os i, obtain:
g i { cos ( 2 &pi; f in t n ) [ A ^ i cos ( 2 &pi; f in &Delta; t i ) + B ^ i sin ( 2 &pi; f in &Delta;t i ) ]
( 2 &pi; f in t n ) [ A ^ i ( 2 &pi; f in &Delta; t i ) - B ^ i cos ( 2 &pi; f in &Delta; t i ) ] } + C ^ i + os i
= A i cos ( 2 &pi; f in &Delta; t i ) + B i sin ( 2 &pi; f in &Delta; t i ) + C i
At last, obtaining passage i with respect to the mismatch error of reference channel is:
&Delta; t i = a tan ( A i B ^ i - A ^ i B i A i A ^ i + B ^ i B i ) / 2 &pi; f in , g i = A i A ^ i cos ( 2 &pi; f in &Delta; t i ) + B ^ i sin ( 2 &pi; f in &Delta; t i ) , os i = C i - C ^ i ;
G wherein i, Δ t iAnd os iThe gain, the sampling clock that are respectively time alternative ADC system i passage postpone and skew T sBe the sampling period of time alternative ADC system, The output sequence that does not have mismatch error for passage i The sinusoidal expression parameter, A i, B i, C iBe the actual output sequence Y of passage i iThe sinusoidal expression parameter.
2. the acquisition methods of channel mismatching error of time alternative ADC system according to claim 1 is characterized in that, described sinusoidal input signal x (t) frequency is f In=Jf s/ N and f In≤1/ (2MT s), J and N are relatively prime, f sFrequency for clock signal.
CN200910167760A 2009-09-27 2009-09-27 Method for obtaining channel mismatching error of time alternative ADC system CN101674087B (en)

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CN102075464A (en) * 2011-01-18 2011-05-25 电子科技大学 Joint estimation and real-time correction method for channel error of TIADC system
CN102291141B (en) * 2011-04-22 2014-03-12 合肥工业大学 Time-interleaved split ADC (Analog-to-Digital Converter) calibration structure without redundant channel and adaptive calibration method thereof
CN103067006B (en) * 2012-11-22 2015-07-29 北京工业大学 A kind of real-time correction method for time-interleaved A/D conversion system time error
CN103312329B (en) * 2013-05-23 2016-08-10 电子科技大学 Bearing calibration and corrector for time-interleaved ADC sampling time mismatch
CN103647554A (en) * 2013-12-16 2014-03-19 电子科技大学 Method for measuring bias and gain errors of time alternative ADC acquisition system
CN104753534A (en) * 2013-12-27 2015-07-01 中兴通讯股份有限公司 Device and method for expanding the bandwidth of ADC sampling
CN109361393A (en) 2014-12-26 2019-02-19 华为技术有限公司 A kind of analog-digital converter and D conversion method
CN104993828B (en) * 2015-08-13 2019-04-09 无锡比迅科技有限公司 Time-interleaved analog-digital converter sample time offsets calibration method
CN105656834A (en) * 2015-12-21 2016-06-08 武汉虹信通信技术有限责任公司 Digital correction method for IQ channel mismatch of novel broadband receiver
CN105933005A (en) * 2016-04-19 2016-09-07 中国电子科技集团公司第四十研究所 Time-domain alternation analog to digital converter mismatch calibration method based on equivalent sampling
CN106444216B (en) * 2016-08-31 2019-07-30 上海交通大学 Multichannel optical analog to digital conversion system middle width strip signal sampling channel mismatch repair method

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CN1947341A (en) * 2004-04-21 2007-04-11 罗斯蒙德公司 Analog-to-digital converter with range error detection

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