CN101273566A - Apparatus and method for simultaneous testing of multiple orthogonal frequency division multiplexed transmitters with single vector signal analyzer - Google Patents
Apparatus and method for simultaneous testing of multiple orthogonal frequency division multiplexed transmitters with single vector signal analyzer Download PDFInfo
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Abstract
A signal analyzer and method for measuring signal compression levels of one or more individual orthogonal frequency division multiplexed (OFDM) signals among a plurality of OFDM signals within a composite signal.
Description
The cross reference of related application
The application requires the U.S. Patent application No.11/533 of proposition on September 21st, 2006, the priority of the U.S. Provisional Patent Application 60/596,444 that on September 23rd, 971 and 2005 proposed.
Technical field
The present invention relates to the test of OFDM (OFDM) transmitter, relate in particular to and use vector signal analyzer (VSA) test OFDM transmitter.
Technical background
As everyone knows, multiple-input and multiple-output (MIMO) communication system uses many transmitter and receivers to strengthen the reliability and the signal volume of communication link.The test of every transmitter is normally by being connected to VSA with every separate unit transmitter, and finishes at every continuous duplicate measurements of transmitter.Alternatively, another method is every transmitter to be connected to its oneself VSA goes up and carry out test simultaneously.Therefore, first method only requires a VSA, but obviously needs the more time; And second method requires a plurality of VSA system, but obviously needs the less time.
The conventionally test of wireless device is included in the transmitter of testing an activity sometime.Even this device provides many transmitters, they usually can not parallel work-flow.Yet people attempt to improve data rate always.In the past by using more complicated modulation and higher bandwidth to realize this target.These methods have been used an independent transmitter, therefore can use an independent input test instrument to carry out and measure.
Along with the introducing of MIMO technology, make single transmitter carry the information of separating by utilizing identical frequency and bandwidth to be used to transmit, many parallel transmitters are used to improve the data rate of the permission in the given bandwidth.In normal operating process, a plurality of paths of system requirements are used for transmitting parallel data flow simultaneously reliably by identical bandwidth.This system relies on advanced signal processing method to separate different transmission signals in desired a plurality of receivers.The data that receiver separates and extraction sends by many transmitters.Therefore, need many parallel receivers intactly analyze a real MIMO signal, and who can not re-use an independent input test instrument and intactly analyze the signal that is transmitted.
There is being the people need obtain research and development (R﹠amp about the device in test (DUT) information as much as possible; D) especially true in the test.Yet in order to carry out product test, the someone may not need so many information because in fact whether he determine DUT correctly assembling in test, and all component whether function is intact.Suppose that all primary clusterings (for example, chip) have obtained test, and if assemble completely and correct, the design that is generated turns out to be correct running, thus the demand of just having avoided similar DCO to install.
From the viewpoint of product, the someone expects to have and satisfies the alap testing cost that covers the test that requires fully.Product test not only comprises the examination and test of products usually, usually also comprises even more important product calibration.In the product calibration process, the performance of equipment will be adjusted to and satisfy desirable performance.
The optimal cost of testing in the product comprises with the testing equipment of arm's length pricing guarantees the fast as far as possible testing time.Test MIMO launching opportunity is indicating have the people can utilize concurrent testing equipment, so that can every transmitter of concurrent testing.Compare with traditional device, this can increase the testing time hardly, but the cost that test will be installed doubles, and has increased total testing cost thus.
Because modern testing equipment provides obviously stronger signal handling capacity, carry out having other selection really all tests except walking abreast simply.As indicated, may be not necessary to measure all parameters of DUT in the production; Often be that the someone can measure the parameter that expection can change in the production equipment simply.This comprises identification faulty components and assembly problem, and the performance of separate unit transmitter is calibrated to the optimum ability that approaches.
Summary of the invention
According to the present invention, provide a kind of signal analyzer and method of Signal Compression level of the one or more independent ofdm signal that is used for measuring a plurality of OFDMs (OFDM) signal in the composite signal.
According to one embodiment of present invention, a kind of signal analyzer of Signal Compression level of the one or more single ofdm signals that are used for measuring a plurality of OFDMs (OFDM) signal in the composite signal comprises:
Be used to detect the first input apparatus, so that provide and corresponding first data detection signal of the envelope of described composite data signal, wherein via signal communication paths composite data signal that receive, that comprise at least the first and second ofdm signals
The described composite data signal that is derived from a remote signal sources has a plurality of associated signals transmissions, and described remote signal sources comprises a plurality of packets, and each packet all comprises the appropriate section of a plurality of transmission data, and
Each appropriate section of described a plurality of transmission data is with respect to corresponding one and the signal communication paths of described a plurality of signals transmissions, corresponding to the appropriate section of a plurality of given datas;
Be used at least in part according to a plurality of processes that are substantially similar to described a plurality of signals transmissions at least, handle composite data signal and described a plurality of given data, so that the signal processing apparatus corresponding at least the first and second reference signals of at least the first and second parts of described a plurality of given datas is provided respectively;
Be used to detect described at least the first and second reference signals so that the secondary signal detector means of at least the first and second control signals is provided respectively; And
Be used to respond described at least the first and second control signals, analyze described first data detection signal so that the signal analysis apparatus of at least the first and second analytic signals of at least the first and second power characteristics of indicating described at least the first and second ofdm signals is provided respectively.
According to another embodiment of the invention, a kind of method of Signal Compression level of the one or more single ofdm signals that are used for measuring a plurality of OFDMs (OFDM) signal in the composite signal comprises:
Detection is via signal communication paths composite data signal that receive, that comprise at least the first and second ofdm signals, so that first data detection signal corresponding to the envelope of described composite data signal is provided, wherein
The described composite data signal that is derived from remote signal sources has a plurality of associated signals transmissions, and described remote signal sources comprises a plurality of packets, and each packet all comprises the appropriate section of a plurality of transmission data, and
The described appropriate section of each of described a plurality of transmission data is with respect to corresponding one and the described signal communication paths of described a plurality of signals transmissions, corresponding to the appropriate section of a plurality of given datas;
At least be substantially similar to a plurality of processes of described a plurality of signals transmissions to the small part basis, handle described composite data signal and described a plurality of given data, so that at least the first and second reference signals corresponding at least the first and second parts of described a plurality of given datas are provided respectively;
Detect described at least the first and second reference signals so that at least the first and second control signals are provided respectively; And
Respond described at least the first and second control signals, analyze described first data detection signal so that at least the first and second analytic signals of at least the first and second power characteristics of described at least the first and second ofdm signals of indication are provided respectively.
Description of drawings
Fig. 1 describes the signal graph that is applicable to the typical MIMO ofdm signal burst configuration of together using with method according to an embodiment of the invention;
Fig. 2 describes to be used to put into practice the block diagram of the receiver system of method according to an embodiment of the invention;
Fig. 3 is the block diagram of the receiver subsystem of Fig. 2;
Fig. 4 A and 4B are the block diagrams of optional embodiment of describing interface/computer of Fig. 2;
Fig. 5 describes many block diagrams with tested OFDM transmitter according to an embodiment of the invention;
Fig. 5 A is the block diagram of an example embodiment the processing stage of describing the emission of Fig. 5;
Fig. 6 is a block diagram of describing the process that relates to the method for testing of putting into practice different embodiment according to the subject invention;
Fig. 6 A and 6B have described among Fig. 6 the selected signal that identifies in its time domain and frequency domain;
Fig. 7 describes to be used for the block diagram of technology that characterization causes the non-linear behavior of Signal Compression;
Fig. 8 A-8C describes the block diagram that is used to put into practice testing equipment configuration of the present invention;
Fig. 9 A-9B has graphically described the result that signal EVM measures;
Figure 10 A-10B has graphically described the result that signal correction is measured;
Figure 11 A-11B has graphically described the CCDF curve;
Figure 12 A-12B, 13A-13B, 14A-14C and 15A-15D have graphically described various unpressed, compression and compound MIMO signals; And
Figure 16 describes to be used to block diagram that compare and measure and technology reference signal according to an aspect of the present invention.
Embodiment
The following detailed description is an exemplary embodiment of the present invention with reference to the accompanying drawings.These descriptions are for exemplary purposes, are not to be to limit the scope of the invention.These embodiment have been carried out abundant detailed description so that those of ordinary skill in the art can put into practice the present invention, and should be appreciated that and to change the embodiment that puts into practice other and can not depart from the spirit or scope of the present invention with some.
The traversal present disclosure lacks the obvious indication opposite with context, should be appreciated that described single circuit element may be quantitatively for one or more.For example, term " circuit " and " circuit " may comprise single component or a plurality of assembly, and it may be active and/or passive, and connect or otherwise be coupled (for example, as one or more integrated circuit (IC) chip) so that described function to be provided.In addition, the one or more electric currents of term " signal " possibility acute pyogenic infection of finger tip, one or more voltages, or data-signal.In the accompanying drawings, identical or relevant element can have identical or relevant letter, numeral or alphanumeric identifier.
Method of testing according to the present invention is provided for using separate unit VSA to test two or many OFDM transmitters simultaneously.This method has been utilized the following fact: typical MIMO OFDM transmitter is its output signal of emission in burst, has customizing messages during beginning of happening suddenly is preamble, and this helps the reliable reception and the demodulation of the remainder of signal burst.
With reference to figure 1, according to one embodiment of present invention, an example of employed one group of signal comprises two signal bursts when two transmitters of test, as shown in the figure.In this example, used three preambles, each all has its oneself cyclic shift (CS).Except cyclic shift, the preamble of second transmitter is identical with the preamble of first transmitter.For example, preamble 1,2 and 3 cyclic shift were respectively 400,3100 and 1600 nanoseconds.Yet should be appreciated that for MIMO moves the preamble that designs other also be possible.
With reference to figure 2, be applicable to that an embodiment 200 who puts into practice system of the present invention comprises receiver 202, controller 204, and the interface 206 that may comprise computer.Input radio frequency (RF) signal 201 (discussing in more detail below) comes the control signal 205 of self-controller 204 to handle by receiver 202 bases.The data vector 203 of result's sampling is provided for interface 206.If interface 206 comprises computer, then Cai Yang data vector 203 can obtain in this locality handling.Otherwise the data vector 203 of sampling may be delayed, and for example, handles to outer computer via network (as Ethernet) interface 209.Along with on network interface 209, receiving, control data 207 or offer controller 204 via interface 206 by the inner computer of interface 206 or by outer computer.
With reference to figure 3, an exemplary embodiment 202a of receiver 202 comprises many conventional components and parts that connect in a conventional manner, substantially as shown in the figure.Input rf signal 201 is amplified by variable gain amplifier 302 according to the control signal 205a that comes self-controller 204.Consequential signal 303 use local oscillator (LO) signal that the LO304 by the control signal 205b that is controlled by to come self-controller 204 provides in frequency mixer 306 to down-conversion.The down-conversion signal 307 that produces is by band pass filter 308 filtering.Filtered signal 309 utilizes another variable gain amplifier 310 to amplify according to the control signal 205c that comes self-controller 204.
Down-conversion and filtered signal 311 are used to quadrature LO signal 313i, the further down-conversion of 313q of the 2nd LO 312 from the control signal 205d that is controlled by to come self-controller 204 at frequency mixer 314i, 314q.Base band orthogonal signalling 315i, the 315q that produces uses low pass filter 316i, 316q filtering.(should be appreciated that and can carry out the single down-conversion, for example, wherein input rf signal 201 is amplified by a variable gain amplifier 310, and the 2nd LO 312 is that low pass filter 316i, 316q provide quadrature LO signal 313i, 313q with suitable frequency.)
Filtered signal 317i, 317q are the orthogonal data signals of analog form, and analog-digital converter (ADC) 318i, the 318q of their control signal 205e, 205f by being controlled by to come self-controller 204 are converted into digital data signal 319i, 319q.These data-signals 319i, 319q are according to coming the control signal 205g of self-controller 204 to be stored in the memory 320, as the availability as homophase 321i and quadrature phase 321q data-signal.
With reference to figure 4A, an embodiment 206a of interface 206 comprises the computer that utilizes Survey Software 402 and Control Software 404 programmings.User's operation is carried out by graphic user interface 406, and this graphic user interface is communicated by letter with Survey Software 402 and Control Software 404 with control information 405 by data 40.
With reference to figure 4B, when using outer computer, this computer 400 comprises interface 440, by this interface Survey Software 402 and Control Software 404 via network is connected 209 and local interface 206 mutual.Data message 441m and control information 441c change between interface 440 and Survey Software 402 and Control Software 404.
With reference to figure 5, the RF signal 201 that use method according to an embodiment of the invention to test is two or more (being two) combination from the transmission signals of the transmitter of equal number in this example.In this example, the emission unit 500 that test comprises two signal transmission systems.The data 501a that sends, 501b handle according to process of transmitting 502a, 502b.Signal 503a, the 503b that generates amplifies by amplifier 504a, 504b so that produce time domain data signal 505a, 505b, time domain data signal 507a, 507b that this signal is used to transmit with generation by filter 506a, 506b filtering.Filter 506a, 506b provide the simulation of linear distortion, and other forms of distortion (for example, amplifier noise, nonlinear amplifier and frequency mixer distortion, the I/Q imbalance, phase noise etc.) by additional error signal 551a, the 551b simulation of introducing via signal combiner 552a, 552b.Result's signal 553a, 553b generated RF signal 201 mutually in signal combiner 554.
With reference to figure 5A, a exemplary embodiment that can following description emission process 502a, 502b.Input data 501a, 501b carry out preliminary treatment by processor 510, and in 510, the input data are encoded, interlacing scan, be parallel form and shine upon according to quadrature amplitude modulation (QAM) from serial conversion.Orthogonal signalling U1 (k) 511i, the 511q that produce handle according to inverse fast Fourier transform (IFFT) 512, and signal 513i, the 513q of Chan Shenging is converted to serial form from walking abreast in conversion process 514 subsequently.Serial signal 515i, 515q have the Cyclic Prefix that adds in next process 516 as a result, thereby generate orthogonal data signal 517i, the 517q that is used to transmit.
Preamble maker 518 generates quadrature preamble signal 519i, 519q.Data 517i, 517q and preamble 519i, 519q signal are provided for signal router, for example, and transducer 520.According to control signal 521c, router five 20 selects the back with preamble signal 519i, 519q that data-signal 517i, 517q are arranged.Selected signal 521i, 521q are entering into buffer amplifier 522i, 522q buffer memory, and in signal mixer 524i, 524q with before quadrature switching signal 531i, 531q mix, be converted to analog signal 533i, 533q (following will going through) by D-A converter (DAC) 532i, 532q, along with consequential signal 525i, 525q addition in signal combiner 526, generate output signal 503a, 503b.
Local oscillator circuit 528 provides quadrature local oscillator signal 529i, 529q, they mix with orthogonal signalling 531a, the 531b of the quadrature imbalance that is used for the analog signal transmission path in signal mixer 530i, 530q, generate quadrature local oscillator signal 531i, 531q thus.The signal gain Gi of buffer amplifier 522i, 522q, Gq are used for the amplitude imbalance of analogue orthogonal signal transmission path.
With reference to figure 6, according to one embodiment of present invention, Survey Software 402 can be carried out many tests and operation shown in technological process 600.Input sampling data vector 321i/321q uses in a plurality of processes that comprise frequency spectrum calculating 602, matched filtering detection 604 and frequency correction 606.Frequency spectrum calculates the data 603 that 602 results by for example average fast Fourier transform (FFT) processing provide the power spectrum of the signal of representing combination.
Matched filtering testing process 604 is beginning, character boundary and the frequency error of input signal 321i, 321q detection signal.Frequency error information 605a is provided for frequency correction process 606, and signal begins 605b and character boundary 605c information is provided for parallel transfer process 608.
For the purpose of test, the initial data that is sent by the transmission system in the test 500 is known, and offers two transmission course 502aa, 502ba as given data 501aa, 501ba in Survey Software 402.The double frequency numeric field data signal U1 (k) that generates
*503aa, U2 (k)
*503ba is according to FILTER TO CONTROL data 613a, 613b filtering 506aa, the 506ba filtering by the original filter 506a, the 506b that are intended to emulation transmission system 500.Filtering data S1 (k) as a result
*507aa, S2 (k)
*507ba is produced mutually the desirable transmission signals 615 of reconstruct in anabolic process 614, signal 615 by from received signal 611 cut to produce composite error signal E1 (k)
*+ E2 (k)
*617.Utilize normalized form, can calculate EVM according to this compound error signal 617.
Should be appreciated that given data 501aa, 501ba may use the initial condition an of the unknown to handle by scrambler (for example, in process of transmitting 502a, 502b) in emission unit 500.This uncertainty can will be resolved from the process that all possible relatively scrambler initial condition of the data that input signal 321i/321q obtains is again proofreaied and correct in receiver 600 in utilization.
Based on aforementioned discussion, to describe as Fig. 6, signal measurement can be summarized as follows: the beginning and the character boundary that for example utilize the filter detection input signal that mates with preamble.The output of the filter of coupling is used to derive the signal(-) carrier frequency skew, and skew can calculate suitable frequency correction and use in time domain according to signal(-) carrier frequency.(should be appreciated that and also can use other known technology to realize these functions, for example power envelope detect or from dynamic(al) correction).
Utilize fast Fourier transform (FFT) to handle the remainder of input signal, the data of preamble back for example, a symbol is represented in each FFT output.Each FFT output has N value, and a subclass N1 of these values represents to comprise OFDM (OFDM) signal carrier of information.Usually, value N has 2 power, and N1 approximates N-10.The MIMO preamble structure that is used for M platform transmitter allows for each the OFDM carrier wave N1 that occurs at the signal Y1 (k) that is transmitted, Y2 (k) and sets up the M formula, M the unknown.Finding the solution these formula is the estimation that middle each carrier wave that transmits of these signals Y1 (k), Y2 (k) provides amplitude and phase response H1, H2.The channel glacing flatness is by amplitude response H1, the H2 decision of filter, and power level is determined by the power phase Calais with each carrier wave among the transmission signals Y1 of institute (k), the Y2 (k), and I/Q is uneven to calculate by the correlation between the positive and negative carrier wave around the intermediate frequency of estimation each transmission signals Y1 (k), Y2 (k).
Because the content of preamble is that priori is known, and because the input preamble has tangible cyclic shift, just can be from the signal of each transmitter to each carrier signal separation.Use different multiple-input and multiple-outputs (MIMO) to realize, then can use different preambles, this preamble is designed to basic at least quadrature.If initial data is known, then transmitter 500 can be operated to have realized scramble because the scrambler setting can use matched filter to derive, and if scrambler be provided with knownly, just can derive desirable reference signal.
As aforesaid result, can set up power level from each carrier signal of each transmitter, therefrom can determine available power from each transmitter, and the frequency spectrum glacing flatness, that is, pass the uniformity of the signal power of frequency spectrum.Be used for the power of each carrier signal of every transmitter and the channel response of every transmitter of phase place representative, as what in filter process 506aa, 506ba, simulated.
By comparing the transmitter signal of these separation, can derive quadrature (I/Q) imbalance of every transmitter.
If data content is known, as desired during test condition, (consider the scrambler uncertainty simultaneously, as mentioned above), error vector value (EVM) can calculate by the output of FFT process is compared with the desirable FFT output after channel correction is used.The calculating of phase noise can be carried out in a similar fashion.By average FFT output, can calculate the power spectrum of the signal of combination.
Relative timing can be determined according to the position of the output peak value of matched filter 604.
With reference to figure 6A and 6B, utilize frequency domain data signal U1 (k)
*503aa is an example, and time domain between the signal and frequency domain relation can be as described below.With reference to figure 6A, signal U1 (k) is the sequence of column vector, and each has the FFT element that quantity is N, and each row is all represented a symbol of the grouping in the frequency domain.For example, for IEEE 802.11a/g signal, numerical value of N typically is 64 and IFFT and FFT function use the input of 64 vectors units to carry out.Signal U1 (k) is used for dividing into groups the column vector of k symbol.With reference to figure 6B, signal u1 (t) is the time-domain signal (length of preamble is disproportionate) corresponding to U1 (k).For example, frequency domain vectors U1 (2) is corresponding to the time-domain signal u1 (t) on the time interval t, and is as follows:
T
0+T
CP+2.T
s＜t＜T
0+3.T
s
Frequency-region signal U1 (k) can be according to the following derivation of time-domain signal u1 (t):
U1(k)＝FFT(u1(t).e
-jωt)
Wherein: t=mT
Sa-kT
s+ T
0+ T
CP
ω=2 π f
c, f
cFrequency for local oscillator signals 529i, 529q
T
SaThe sampling clock frequency of=1/ D-A converter
T
s=symbol duration comprises Cyclic Prefix
T
0The beginning of first symbol behind the=preamble
T
CPThe duration of=Cyclic Prefix
The k=symbolic number
M=hits (for example, for IEEE 802.11a/g m=0:63)
As discussed above, the MIMO transmitter can be tested with parallel mode, and wherein the output of separate unit transmitter is for example made up so that the signal of combination is presented to finishing the signal testing instrument that actual signal is analyzed via power combiner.By using advanced signal processing algorithm, many single parameters can both utilize the signal pin of combination that every individual transmitter is extracted.This analysis is based on knowing the data that are sent out, and the standing part of MIMO packet (for example, header of the data packet).This ability has very big advantage in production system, because it allows only to use the separate unit tester to carry out the concurrent testing of MIMO transmitting system, therefore provide test speed and lower cost faster, thereby satisfied the requirement of alap production cost.
A kind of test of expectation will be to measure the compression of the unit of employed different transmitters in the mimo system and be every transmitter assignment mass measurement.When transmitter compresses the signal that is transmitted, so just reduced quality of signals, this can have great EVM to show via the signal that is transmitted as measurement and the difference of ideal signal.For ofdm signal, EVM is expressed as the planisphere of each carrier wave and the difference between the ideal constellation, for example, is stated in the EVM requirement as IEEE 802.11a/g standard.A kind of method that compression level is associated with single transmission link is by measuring CCDF (CCDF), and this function is well-known feature (following this method will be discussed in further detail).
With reference to figure 7, another kind of method is that characterization will cause the non-linear behavior that compresses.From can following input signal y (t) expression according to it such as the output x (t) of the non-linear element of power amplifier:
x(t)＝a
1*y(t)+a
3*y
3(t)+a
5*y
5(t)+...
A wherein
3And a
5It is the non linear coefficient that determines the power of the 3rd and the 5th rank response.Can be always from the compression property of every transmitter of compound signal, i.e. coefficient a
3And a
5, derive signal quality according to every transmitter of its EVM.
With reference to figure 8A, test configurations 800a comprises the DUT 802 with a plurality of (for example, two) transmitter 804a, 804b, signal combiner 806, and VSA 808, and computer 810.Computer 810 comprises and moves via interface 813 provides instruction and data to receive the DUT Control Software 812 of data to DUT 802 and from DUT 802, and each other and via VSA Control Software 814 and the analysis software 816 of another interface 815 with VSA 808 swap datas and instruction.
With reference to figure 8B, in an optional test configurations 800b, between transmitter 804a, 804b and signal combiner 806, put into transducer 820a, 820b, and be controlled by instruction from the switching controls software 814b in VSA and the computer 810.
With reference to figure 8C, but in an arrangement 800c, removed signal combiner 806, and the output of every transmitter 805a, 805b are measured by its oneself VSA 808a, 808b directly.
Refer again to Fig. 8 A, according to a test configurations, first transmitter 804a is with output fixing signal 805a compression operation, thus the EVM of generation 32dB, and the compression of second transmitter 804b changes.Utilize single VSA 808 to measure the EVM of second transmitter 804b.In order to obtain the EVM reference value, utilize the VSA 808 direct EVM that measure from second transmitter 804b that only are connected to second transmitter 804b, promptly do not increase by the signal 805a of first transmitter 804a.
With reference to figure 9A and 9B, can compare the EVM of two measurements.Transverse axis has shown the EVM of second transmitter 804b when using reference software to analyze.The longitudinal axis has shown the error among the EVM when using the duplex measurement technology (being unit with dB).At this specific test, if use IEEE 802.11a/g system, when the maximum data rate that can accept limit during for-25dB, the scope of interested especially EVM be-24 and-27dB between.Fig. 9 A has illustrated two transmitters to be set to the situation (precommpression) that sends with identical power, and Fig. 9 B has illustrated first transmitter 804a to be in the situation that exceeds one decibel level than second transmitter 804b.In the interested scope of institute since Fig. 9 A have+/-error range of 1dB, and Fig. 9 B has+/-error range of 1.5dB, error demonstrates a little positive bias.These tests are to use the relatively short grouping that 24 symbols are only arranged to finish.The length that increases grouping will improve accuracy.
With reference to figure 10A and 10B, the EVM of every transmitter 804a, 804b may be subjected to the influence in other infringement source.From the degree of correlation of different transmission links, can monitor the compression of every transmitter by relatively.Transverse axis is the function of the ratio of third-order correlation coefficient
And the longitudinal axis is the difference among the EVM between transmitter 804a, the 804b, Figure 10 A has illustrated that wherein transmitter output signal 805a, 805b are compressing the situation that (not being non-linear) power before equates, and Figure 10 B has illustrated that wherein first transmitter 804a is in the situation that exceeds one decibel level than second transmitter 804b.
The test of another hope is the single compression of measuring employed different transmitters in the mimo system.Compression is often measured the form of the CCDF in the signal of average ratio to have higher peak, ofdm signal for example, and provide the important information of the performance that helps to check transmitter.In the good system of design, the power that is transmitted is adjusted to certain compression level so that can satisfy the launch mass requirement.Reduce output signal power and will cause increasing source current consumption, thereby but increasing power will bring system into darker output signal compression and cause launch mass to be downgraded on the point of restriction that systematic function may be subjected to relatively poor transmission quality.
With reference to figure 11A, the typical CCDF curve display of IEEE 802.11a/g (OFDM) transmitter the probability of the relative average power of signal with X-dB or higher instantaneous power.The CCDF of the measurement of the transmitter that the typical design of curve 1102 representatives is good is not and if curve 1104 representatives have the theoretical CCDF of Signal Compression.Transverse axis is the skew with respect to average power, and the longitudinal axis is a probability.The terminal point 1106 of the CCDF curve of compression can be represented compression level, because it has indicated the compression degree of the peak-peak of input signal.In this example, output signal has been compressed about 3dB with respect to theory signal.Terminal point 1106 can have some variations along with shorter packet, because packet content (unpressed) possibility can be just in time along theoretical curve 1104 owing to the relatively low probability of the peak value that reaches this level.Therefore, though terminal point 1106 also should only be regarded the indication of compression as through being usually used in the actual identification compression.
CCDF itself is the simple relatively function of deriving.Problem is that someone for example can seek usually in product is installed, the signal with higher compression that is caused by the circuit unit that breaks down.In the single-shot transmitter system, someone will accomplish to identify compression (Figure 11 A) in the place of higher curvature indication compression easily.Signal can show with respect to the peak power of absolute power up to 10dB, but the transmitter of measuring output may only show the peak value of about 7dB; Therefore, transmitter will compress peak-peak to about 7dB.Because these peak level are rare relatively, this compression generally speaking can too not influence data that transmitter performance sent to the obstruction degree based on the recovery of normal performance range and error correction.If two transmitters demonstrate identical compression, then this also is like this for mimo system.
Yet the mimo system with the transmitter that has fault may not only produce compressed signal but also produce non-compressed signal, thereby demonstrates different signal transmission characteristicses.If signal peak is uncorrelated,, then measures compression and may compare difficulty by the signal of checking combination such as for many signal flows MIMO signal.If two kinds of signals all show not compression, then absolute peak will exceed the peak value 3dB of each signal.Yet RMS power also exceeds 3dB, has therefore kept the peak of maximum 10dB to mean value.If a signal shows that another shows some compressions less than compressing, the peak-peak of 7dB as discussed above (CCDF can stop at 7dB) for example, when these two signals of combination, CCDF is with the approximately reduction of 1.3dB (for the rms signal power that equates) on the peak value display.If compression increases to 5dB, then compound CCDF will only show the compression with respect to theory signal 1.8dB, and if further be reduced to the peak value of 3dB, then CCDF will show the compression with respect to theory signal 2.2dB.Usually, the performance that compression will limit transmitter is to the peak value scope between 6.5dB and the 7dB, and if one of them of two transmitters fault has taken place, the whole M IMO system fault that just becomes.
With reference to figure 11B, Figure 11 B is the compound CCDF curve of dual transmitter MIMO signal and the comparison between the single CCDF curve.Curve 1108 is theoretical curves of MIMO ofdm signal, and curve 1110 is compound (combination) CCDF.The curve of the unpressed input of one of them of two MIMO transmitters is in fact consistent with theoretical curve 1108.Curve 1112 is at other MIMO transmitter, and indication is near the significant compression of the curve of the transmitter that is used for optimum calibration.Can obviously find out thus, on the signal of combination, use the CCDF measurement that considerably less information is provided.Someone almost can not distinguish the signal and the theory signal of combination, and one of them transmitter has arrived at utmost at a good system compresses simultaneously.Therefore, the traditional instrument that someone can not use separate unit can measure CCDF is probably fully measured CCDF, because often require product test to install.Yet CCDF is the desirable analysis tool that can often help to improve product test speed, because it is simple analysis and important insight to signal component is provided.
By measuring composite signal EVM, can discern other part of compound EVM, also known compression property till that time, it can determine whether the EVM part is similar for different signal transmission paths, or whether the influence of a signal transmission path has controlled compound EVM.
With reference to figure 12A and Figure 12 B, the CCDF characteristic of the curve 1102 that relatively announcement is similar to Figure 11 A of the compressed version (Figure 12 B) of the time sampling of desirable not compressed signal (Figure 12 A) and identical time sampling in the time domain, and compression do not influence peak, and to the decay of big peak value greater than to the fact than the decay of small leak.
With reference to figure 13A and 13B, for the composite signal of two MIMO signals, Figure 13 A has described the result when two signals all are not compressed, and Figure 13 B described when one of them of two signals be compressed to as Figure 11 A 1102 shown in level the time the result.Find out that from this compression is can be descried in some cases, and signal continues to show complete peak value in other cases.As desired, compressed signal (Figure 13 B) peak value reduces, but is not easy to identify compression (Figure 13 A) with reference to unpressed signal comparison the time.
With reference to figure 14A-14C, two signals (Figure 14 A and 14B) that transmit have separately produced composite signal (Figure 14 C), wherein as can be seen in some instances a signal in peak value, preponderate, other signal is preponderated in other example, thereby and in the another one example two signal peaks take place simultaneously to cause composite signal bigger to peak value.
With reference to figure 15A-15D, there is shown the signal (Figure 15 A and 15B) of identical independent transmission, but a Signal Compression (Figure 15 A), and the not compression (Figure 15 B) of another signal produces another composite signal (Figure 15 C).For relatively, do not carry out Signal Compression, also produced another composite signal (Figure 15 D).
As discussed above, if the data that send via the MIMO signal are known, might estimate desirable composite signal and estimate EVM according to it.This process extracts the signal that is received, and aims at ideal reference signal in frequency with in the time, and itself and reference signal are compared, and signal that is extracted and reference signal are similar to the signal of describing among Figure 15 C and the 15D respectively.There are two independent reference signals as can be seen from the individual signals measurement, therefore also have independent signal.Therefore, can identify the different peak points of two signals, and they are how with compound (combination) signal correction.Utilize these knowledge just may on this aspect of other signal of domination on the power, analyze composite signal at one of them signal as the part of preponderating, desirable composite signal can be compared with the signal of actual measurement at that point, and the compression of the signal of can determining to preponderate.
With reference to Figure 16, as shown in the figure, be used to obtain the signal of measurement and an example of the circuit 1600 of itself and reference signal comparison is comprised: signal envelope testing circuit 1602,1614a, 1614b, IFFT circuit 1612a, 1612b, threshold value comparison circuit 1616a, 1616b, switching circuit 1604a, 1604b, power calculation circuit 1606a, 1606b, and histogram calculation circuit 1608a, 1608b.Detect the data vector signal 321i/321q of envelope input sample, and as definite accomplishing can be used for switching (following discussion) according to control signal 1617a, 1617b.Consequential signal power data 1607a, the 1607b that use is used to every transmitter to calculate the CCDF curve determines the power level of switching signal 1605a, 1605b.
Desirable transmitter signal 507aa, 507ba in the local frequency domain that generates is sent to time domain by their corresponding IFFT process 1612a, 1612b.The envelope of transmitter time- domain signal 1613a, 1613b tested and with separately threshold to determine the lower-wattage point of transmitter signal.Control signal 1617a, 1617b are used to change as mentioned above or realize the envelope of the composite signal envelope 1603 that detected as a result.
Optionally technology comprises other variation of using alternative manner and the actual derivation of CCDF curve at corresponding transmitter, the all different based on the comparison signal of all these is understood the relative power of signal, then the basic skills that this result is compared with measured compound CCDF curve.
For those skilled in the art obvious be in structure of the present invention and the method various other modification and substitute and do not depart from scope and spirit of the present invention.Described the present invention although combined specific preferred embodiment, should be understood that, as desired, the present invention should exceedingly not be subject to such specific embodiment.Following claim intention defines scope of the present invention, and therefore is intended to cover the interior structure and the method for scope of these claims and their equivalent.
Claims (10)
1. equipment comprises comprising the signal analyzer of the Signal Compression level of the one or more independent ofdm signal that is used for measuring a plurality of OFDMs (OFDM) signal in the composite signal:
Be used to detect the first input apparatus, so that provide and corresponding first data detection signal of the envelope of described composite data signal, wherein via signal communication paths composite data signal that receive, that comprise at least the first and second ofdm signals
The described composite data signal that is derived from remote signal sources has a plurality of associated signals transmissions, and remote signal sources comprises a plurality of packets, and each packet all comprises the appropriate section of a plurality of transmission data, and
The described appropriate section of each of described a plurality of transmission data is with respect to corresponding one and the described signal communication paths of described a plurality of signals transmissions, corresponding to the appropriate section of a plurality of given datas;
Be used at least in part according to a plurality of processes that are substantially similar to described a plurality of signals transmissions at least, handle described composite data signal and described a plurality of given data, so that the signal processing apparatus corresponding at least the first and second reference signals of at least the first and second parts of described a plurality of given datas is provided respectively;
Be used to detect described at least the first and second reference signals, so that the secondary signal detector means of at least the first and second control signals is provided respectively; And
Be used in response to described at least the first and second control signals, analyze described first data detection signal, so that the signal analysis apparatus of at least the first and second analytic signals of at least the first and second power characteristics of indicating described at least the first and second ofdm signals is provided respectively.
2. according to the equipment of claim 1, wherein said at least the first and second power characteristics one of them comprises CCDF (CCDF) at least.
3. according to the equipment of claim 1, each in wherein said a plurality of packets also comprises the appropriate section of a plurality of preamble data, and described signal processing apparatus comprises:
Be used to handle the described at least appropriate section of described a plurality of preamble data, so that the preamble processing unit of a plurality of at least control datas is provided; And
Be used to receive described a plurality of given data and described a plurality of control data, and, handle described a plurality of given data, so that the data processing equipment of described at least the first and second reference signals is provided according to described a plurality of processes in response to this.
4. according to the equipment of claim 1, wherein said secondary signal detector means comprises:
Be used to detect described at least the first and second reference signals, so that provide respectively and the corresponding envelope corresponding at least the second of described first and second reference signals and the signal envelope detector device of the 3rd data detection signal; And
Be used to detect the described at least the second and the 3rd data detection signal, so that the signal threshold value detector means of described at least the first and second control signals is provided respectively.
5. according to the equipment of claim 1, wherein said signal analysis apparatus comprises:
Be used in response to described at least the first and second control signals, select the part of the differentiation of part-time at least of described first data detection signal, so that the converter apparatus of at least the first and second signals of selecting is provided;
Be used to the described at least the first and second corresponding power levels of selecting of input, so that the power detection apparatus of at least the first and second power signals is provided respectively; And
Be used to handle described at least the first and second power signals, so that the processor device of described at least the first and second analytic signals is provided respectively.
6. the method for the Signal Compression level of an one or more independent ofdm signal that is used for measuring a plurality of OFDMs (OFDM) signal in the composite signal comprises:
Detection is via signal communication paths composite data signal that receive, that comprise at least the first and second ofdm signals, so that first data detection signal corresponding to the envelope of described composite data signal is provided, wherein
The described composite data signal that is derived from remote signal sources has a plurality of associated signals transmissions, and described remote signal sources comprises a plurality of packets, and each packet all comprises the appropriate section of a plurality of transmission data, and
The described appropriate section of each of described a plurality of transmission data is with respect to corresponding one and the described signal communication paths of described a plurality of signals transmissions, corresponding to the appropriate section of a plurality of given datas;
At least in part according to a plurality of processes that are substantially similar to described a plurality of signals transmissions at least, handle described composite data signal and described a plurality of given data, so that at least the first and second reference signals corresponding at least the first and second parts of described a plurality of given datas are provided respectively;
Detect described at least the first and second reference signals, so that at least the first and second control signals are provided respectively; And
In response to described at least the first and second control signals, analyze described first data detection signal, so that at least the first and second analytic signals of at least the first and second power characteristics of described at least the first and second ofdm signals of indication are provided respectively.
7. according to the method for claim 6, wherein said at least the first and second power characteristics one of them comprises CCDF (CCDF) at least.
8. according to the method for claim 6, each in wherein said a plurality of packets also comprises the appropriate section of a plurality of preamble data, and described processing comprises:
Handle the described at least appropriate section of described a plurality of preamble data, so that a plurality of at least control datas are provided; And
Receive described a plurality of given data and described a plurality of control data, and,, handle described a plurality of given data, so that described at least the first and second reference signals are provided according to described a plurality of processes in response to this.
9. according to the method for claim 6, wherein detect described at least the first and second reference signals and comprise:
Detect described at least the first and second reference signals, so that at least the second and the 3rd data detection signal corresponding to the corresponding envelope of described first and second reference signals is provided respectively; And
Detect the described at least the second and the 3rd data detection signal, so that described at least the first and second control signals are provided respectively.
10. according to the method for claim 6, wherein said analysis comprises:
In response to described at least the first and second control signals, select the part of the differentiation of part-time at least of described first data detection signal, so that at least the first and second signals of selecting are provided;
For the described at least the first and second corresponding power levels of selecting of input, so that at least the first and second power signals are provided respectively; And
Handle described at least the first and second power signals, so that described at least the first and second analytic signals are provided respectively.
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| CN200680034963.7A Expired - Fee Related CN101268643B (en) | 2005-09-23 | 2006-09-22 | Apparatus and method for simultaneous testing of multiple orthogonal frequency division multiplexed transmitters with single vector signal analyzer |
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Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
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| CN104321979A (en) * | 2012-05-09 | 2015-01-28 | 莱特普茵特公司 | System and method for testing a radio frequency (RF) multiple-input-multiple-output (MIMO) device under test (DUT) |
| CN106911351A (en) * | 2015-12-17 | 2017-06-30 | 德克萨斯仪器股份有限公司 | Power effectively wraps detection |
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| CN101312389B (en) * | 2008-05-23 | 2011-11-16 | 北京创毅视讯科技有限公司 | Test data generation unit, generating method, test system and test method |
| US8780745B2 (en) * | 2011-01-31 | 2014-07-15 | Intel Mobile Communications GmbH | Communication terminal, communication device, method for measuring a signal and method for requesting a measurement |
| US8774745B2 (en) * | 2012-12-10 | 2014-07-08 | Qualcomm Incorporated | Reconfigurable receiver circuits for test signal generation |
| CN107809404B (en) * | 2016-09-09 | 2021-09-03 | 中兴通讯股份有限公司 | Method and device for estimating symbol offset |
| CN107508642B (en) * | 2017-07-07 | 2020-09-11 | 湖北大学 | Nonlinear evaluation system and method of high-order modulation communication system |
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| US6628923B1 (en) * | 2000-05-03 | 2003-09-30 | Nokia Networks Oy | Adaptive phase and amplitude linearization method and apparatus |
| US7099266B2 (en) * | 2001-03-26 | 2006-08-29 | Victor Company Of Japan, Limited | Orthogonal frequency division multiplexed signal transmitting apparatus, orthogonal frequency division multiplexed signal receiving apparatus, and orthogonal frequency division multiplexed signal transmitting/receiving system |
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| Publication number | Priority date | Publication date | Assignee | Title |
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| CN104321979A (en) * | 2012-05-09 | 2015-01-28 | 莱特普茵特公司 | System and method for testing a radio frequency (RF) multiple-input-multiple-output (MIMO) device under test (DUT) |
| CN104321979B (en) * | 2012-05-09 | 2017-10-24 | 莱特普茵特公司 | System and method for testing radio frequency (RF) multiple-input and multiple-output (MIMO) measurement equipment (DUT) |
| CN106911351A (en) * | 2015-12-17 | 2017-06-30 | 德克萨斯仪器股份有限公司 | Power effectively wraps detection |
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