CN101268643A - 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
The invention provides an apparatus and method for simultaneous testing of multiple orthogonal frequency division multiplex (OFDM) signal. A vector signal analyzer (600) transforms multiplex signal that is received via a signal communication path and includes a plurality of OFDM signal for providing a plurality of transformed data signal, wherein, multiplex signal data source includes a remote signal source of a plurality of signal transmitting processes relatively, and includes a plurality of data groups, each data group includes respective parts of a plurality of preposing code data, and respective parts of a plurality of transmitting data, each respective parts of a plurality of transmitting data and each one of a plurality of data transmitting processes and respective parts of a plurality of known data relative to the signal communication path, and each one of a plurality of transformed data signal including respective parts of a plurality of data groups, and at least respective parts of receiving and processing a plurality of known data, a plurality of preposing code data, at least respective parts of a plurality of transmitting data for providing a plurality of detection data of error vector amplitude (EVM) associated with multiplex data signal.
Description
Related application
The application requires the priority of No. the 60/596th, 444, the U.S. Provisional Patent Application that proposed on September 23rd, 2005.
Technical field
The present invention relates to the test of OFDM (OFDM, orthogonal frequencydivision multiplexing) transmitter, relate in particular to and utilize vector signal analyzer (VSA, vector signal analyzer) to test the OFDM transmitter.
Background technology
As everyone knows, multiple-input and multiple-output (MIMO) communication system uses a plurality of transmitter and receivers to strengthen the reliability and the signal volume of communication link.Usually by with each separately transmitter be connected with VSA, and repeat measurement successively to each transmitter, finish the test of each transmitter.Alternately, another kind of method relates to each transmitter is connected with its VSA and tests simultaneously.Therefore, first method only needs a VSA, but the more time of significant need, and a plurality of VSA of second method needs system, but the less time of significant need.
The traditional test of wireless device relates to active transmitter of each test.Even equipment provides a plurality of transmitters, can not operate them concurrently usually yet.Yet people often attempt to improve data rate.In the past, this is by utilizing more complicated modulation and wideer bandwidth to realize.These methods have been used individual transmitter, therefore, can utilize single input test instrument to measure.
Along with the introducing of MIMO technology, transmitter utilizes identical transmission frequency and bandwidth to carry discrete information by allowing separately, uses a plurality of parallel transmitters to improve the interior permission data rate of given bandwidth.During normal running, system need send the mulitpath of parallel data stream reliably simultaneously on same band.System depends on and separate the different advanced signal processing that send signal in required a plurality of receiver.The data that receiver separates and extraction is sent by a plurality of transmitters.Therefore, need a plurality of parallel receivers come the real MIMO signal of multianalysis, and can not re-use single input test instrument and come multianalysis to send signal.
This obtains the research and development (R﹠amp of the information of relevant equipment under test (DUT, device undertest) as much as possible for needs; D) test is especially true.Then,, may not need so much information, because real test is in order to determine whether DUT is correctly assembled and whether all parts all work fully for production test.Suppose that all critical pieces (for example, chip) all tested, and if the hypothesis assembling be that complete sum is correct, just confirm that the model machine of producing can correctly work, thereby need not the detail knowledge test plan.
From the visual angle that produces, the possible testing cost that people wish to cover fully required test is minimum.Production test generally includes the examination and test of products and often prior product is calibrated both.Between the product alignment epoch, the performance of adjusting equipment is to satisfy desired properties.
The testing cost of optimizing in producing is included in the fastest possible testing time of assurance under the reasonable cost test request.Test MIMO transmitter shows, can utilize concurrent testing equipment, so that test each transmitter concurrently.Compare with legacy equipment, this increases the testing time hardly, but the cost of test equipment will be doubled, and has therefore improved total testing cost.
Because modern test equipment provides much bigger signal handling capacity, there is other option except only carrying out all tests concurrently really.As mentioned above, may not measure all parameters of DUT aborning; Often can only measure and be expected at the parameter that changes in the production equipment.This comprises and identifies trouble unit and packing problem, and the performance of transmitter is calibrated near best ability separately.
Summary of the invention
According to the present invention, provide and utilized single VSA to test apparatus and method simultaneously from the signal of two or more OFDM transmitters.
According to one embodiment of the present of invention, the vector signal analyzer that is used for testing simultaneously a plurality of OFDMs (OFDM) signal comprises:
Signal transformation part is used for conversion and receives and comprise the composite data signal of a plurality of ofdm signals via signal communication paths, so that the data-signal after a plurality of conversion is provided, wherein,
Described composite data signal is derived from the remote signal sources with a plurality of signal process of transmittings associated therewith, and comprises that a plurality of packets, each of a plurality of packets comprise the part separately of a plurality of preamble data and the part separately of a plurality of transmission data.
Each of a plurality of transmission data be relevant with signal communication paths part separately corresponding to a plurality of given datas separately of part and a plurality of data transmission procedure separately, and
Each of data-signal after a plurality of conversion comprises the part separately of a plurality of packets; And
Signal Processing Element, be used to receive and handle the part at least separately of a plurality of given datas, a plurality of preamble data and the part at least separately of a plurality of transmission data, so that a plurality of test datas of indicating the error vector magnitude (EVM, error vector magnitude) that is associated with composite data signal are provided.
According to an alternative embodiment of the invention, the method for testing a plurality of OFDMs (OFDM) signal simultaneously comprises:
Conversion receives and comprises the composite data signal of a plurality of ofdm signals by signal communication paths, so that the data-signal after a plurality of conversion is provided, wherein,
Described composite data signal is derived from the remote signal sources with a plurality of signal process of transmittings associated therewith, and comprises that a plurality of packets, each of a plurality of packets comprise the part separately of a plurality of preamble data and the part separately of a plurality of transmission data,
Each of a plurality of transmission data be relevant with signal communication paths part separately corresponding to a plurality of given datas separately of part and a plurality of data transmission procedure separately, and
Each of data-signal after a plurality of conversion comprises the part separately of a plurality of packets; And
Receive and handle the part at least separately of a plurality of given datas, a plurality of preamble data and the part at least separately of a plurality of transmission data, so that a plurality of test datas of indicating the error vector magnitude (EVM) that is associated with composite data signal are provided.
Description of drawings
Fig. 1 is the signal graph of describing to be suitable for use in according to the typical MIMO ofdm signal burst configuration in the method for one embodiment of the invention;
Fig. 2 is the calcspar of describing to implement according to the receiver system of the method for one embodiment of the invention;
Fig. 3 is the calcspar of the receiver subsystem of Fig. 2;
Fig. 4 A and 4B are the calcspars of alternate embodiments of the interface/computer of depiction 2;
Fig. 5 is that describe will be according to the calcspar of a plurality of OFDM transmitters of one embodiment of the present of invention tests;
Fig. 5 A is the calcspar of an one exemplary embodiment in the process of transmitting stage of depiction 5;
Fig. 6 is the calcspar that is described in the process that relates in the method for testing of enforcement according to various embodiment of the present invention;
Fig. 6 A and 6B they time domain and frequency domain in described in Fig. 6, to discern signals selected;
Fig. 7 is a calcspar of describing to characterize the technology of the non-linear behavior that causes Signal Compression;
Fig. 8 A-8C is a calcspar of describing to implement test equipment configuration of the present invention;
Fig. 9 A-9B has described the result that signal EVM measures with figure;
Figure 10 A-10B has described the result that signal association is measured with figure;
Figure 11 A-11B has described the CCDF curve with figure;
Figure 12 A-12B, 13A-13B, 14A-14C and 15A-15D with figure described variously not compress, compression and compound MIMO signal; And
Figure 16 describes to compare and measure calcspar with the technology of reference signal according to one aspect of the present invention.
Embodiment
Describe one exemplary embodiment of the present invention with reference to the accompanying drawings in detail.Such description is intended to illustration the present invention, rather than limits the scope of the invention.Fully describe such embodiment in detail and be in order to make those of ordinary skill in the art can implement the present invention, and can utilize some variants that do not depart from the spirit or scope of the present invention to implement other embodiment.
In disclosure full text,, should be understood that described circuit element separately can be odd number or plural number in context unless clear indication is arranged in addition.For example, term " circuit " can comprise active and/or passive and connect or otherwise the single parts that are coupled or a plurality of parts (for example, becoming one or more integrated circuit (IC) chip), so that required function to be provided.In addition, term " signal " can refer to one or more electric currents, one or more voltage or data-signal.In accompanying drawing, identical or relevant element has identical or relevant letter, numeral or alphanumeric indicator.
Created condition according to method of testing of the present invention for utilizing single VSA to test two or more OFDM transmitters simultaneously.Such method has been utilized the beginning of typical MIMO OFDM transmitter in burst, promptly during the preamble of the reliable reception of the remainder of being convenient to signal burst and demodulation, sends the fact of its output signal with the burst that has customizing messages.
With reference to Fig. 1, as shown in the figure, an example of the one group of signal that uses during two transmitters when test according to one embodiment of the present of invention comprises two signal bursts.In this example, used three preambles, each all has the cyclic shift (CS, cyclic shift) of itself.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 are respectively 400,3100 and 1600 nanoseconds.But, should understand that other preamble of operating appointment for MIMO also is fine.
With reference to Fig. 2, be applicable to that an embodiment 200 who implements system of the present invention comprises receiver 202, controller 204 and can comprise the interface 206 of computer.Input radio frequency (RF) signal 201 (more going through as following) is handled according to the control signal 205 of coming self-controller 204 by receiver 202.Gained sampled data vector 203 is offered interface 206.If interface 206 comprises computer, then can handle sampled data vector 203 in this locality.Otherwise, can sampled data vector 203 be transmitted to outer computer by for example network (such as Ethernet) interface 209 and be handled.Control data 207 is offered controller 204 or offered controller 204 by outer computer by interface 206 such as what receive on network interface 209 by the inner computer of interface 206.
With reference to Fig. 3, an one exemplary embodiment 202a of receiver 202 comprises basically as shown in the figure, in a conventional manner many traditional element of Lian Jieing.Input rf signal 201 is amplified according to the control signal 205a that comes self-controller 204 by variable gain amplifier 302.LO signal down-conversion gained signal 303, the one LO 304 that utilize first local oscillator (LO) 304 to be provided in frequency mixer 306 are come the control signal 205b of self-controller 204 to control.Gained down-conversion signal 307 is by band pass filter 308 filtering.Utilize another variable gain amplifier 310 according to the control signal 205c that comes self-controller 204, the signal 309 after the amplification filtering.
In frequency mixer 314i, 314q, be used to be come the control signal 205d of self-controller 204 to control from signal 311, the two LO 312 of further down-conversion process down-conversion of the quadrature LO of the 2nd LO 312 signal 313i, 313q and filtering.Utilize low pass filter 316i, 316q filtering gained base band orthogonal signalling 315i, 315q (should understand easily, replace, can carry out the single down-conversion, for example, provided under the situation of orthogonal signalling 315i, 315q with the frequency that is fit to low pass filter 316i, 316q by 310 amplifications of a variable gain amplifier and the 2nd LO 312 at input rf signal 201).
Filtered signal 317i, 317q are the orthogonal data signals of analog form, and convert digital data signal 319i, 319q to by analogue-to-digital converters (ADC) 318i, 318q, ADC 318i, 318q are come the control signal 205e of self-controller 204,205f to control.According to the control signal 205g that comes self-controller 204, these data-signals 319i, 319q are stored in the memory 320, so that as in-phase data signal 321i and quadrature phase data-signal 321q.
With reference to Fig. 4 A, meet an embodiment 206a of 206 and comprise the computer that utilizes Survey Software 402 and Control Software 404 programmings.User's operation is undertaken by graphic user interface 406, and graphic user interface 406 is communicated by letter with Control Software 404 with Survey Software 402 with control information 405 by data message 403.
With reference to Fig. 4 B, when using outer computer, such computer 400 comprises interface 440, by this interface, Survey Software 402 and Control Software 404 by network is connected 209 and this locality connect 206 mutual.Exchange data information 441m and control information 441c between interface 440 and Survey Software 402 and Control Software 404.
With reference to Fig. 5, utilize the RF signal of testing according to the method for one embodiment of the invention 201 is from two or more (two the in this example) combination of transmission signals with the quantity transmitter.In this example, the emission unit 500 that test comprises two signal sending systems.The data 501a that sends, 501b are handled according to process of transmitting 502a, 502b.Gained signal 503a, 503b utilize amplifier 504a, 504b to amplify, and produce time domain data signal 505a, 505b, and time domain data signal 505a, 505b be through filter 506a, 506b filtering, time domain data signal 507a, 507b that generation will send. Filter 506a, 506b provide the simulation of linear distortion, and additive error signal 551a, the 551b simulation of the distortion of other form (for example, amplifier noise, nonlinear amplifier and frequency mixer distortion, I/Q is unbalance, phase noise etc.) by introducing via signal combiner 552a, 552b.Addition gained signal 553a, 553b are to produce RF signal 201 in signal combiner 554.
With reference to Fig. 5 A, the one exemplary embodiment of process of transmitting 502a, 502b can be described below. Handle input data 501a, 501b by process 510 at first, wherein import data and be encoded, interweave, shine upon from serial conversion to parallel form and according to quadrature amplitude modulation (qam).Handle orthogonal signalling U1 (k) 511i, the 511q of gained according to invert fast fourier transformation (IFFT) 512, then in transfer process 514, gained signal 513i, 513q are become series form from parallel formal transformation.Gained serial signal 515i, 515q are added into Cyclic Prefix in next process 516, thereby produce orthogonal data signal 517i, the 517q that will send.
With reference to Fig. 6, according to one embodiment of the present of invention, Survey Software 402 carries out being expressed as the many tests and the operation of process stream 600.Input sampled data vector 321i/321q is used in the many processes that comprise spectrum calculating 602, matched filtering detection 604 and frequency correction 606.Spectrum is calculated 602 and is asked on average by for example result to the fast Fourier transform (FFT) process, and the data 603 of the power spectrum of representing composite signal are provided.
Matched filtering testing process 604 is starting point, character boundary and the frequency error of input signal 321i/321q detection signal.Frequency error information 605a is offered frequency correction process 606, and the starting point 605b and the character boundary 605c information of signal is offered parallel transfer process 608.
The nominal frequency of input signal 321i/321q is corrected according to frequency error information 605a in frequency correction process 606.Signal message 607 after the correction converts parallel signal information to by the origin information 605b and the character boundary information 605c of transfer process 608 according to signal that walk abreast.
Utilize FFT process 610 to handle parallel signal information 609, send signal 201 corresponding frequency domain information Y1 (k) to produce with initial data
*+ Y2 (k)
*611.This information 611 is offered preamble processing procedure 612 (following discussion).In addition, additive process 616 is further handled this information 611 by deducting broadcast reference signal information 615 (following discussion), is present in initial data with generation and sends error signal in the frequency domain 617 in the signal 201.
For test purpose, the initial data that tested transmitting system 500 is sent is known, and provides as given data 501aa, 501ba, is used for repetition process of transmitting 502aa, 502ba in the Survey Software 402.Gained repeats frequency domain data signal U1 (k)
*503aa, U2 (k)
*503ba by filtering 506aa, the 506ba of the original filter 506a, the 506b that are intended to imitate transmitting system 500 according to filtering control data 613a, 613b filtering.Addition gained filtering data S1 (k) in anabolic process 614
*507aa, S2 (k)
*507ba sends signal 615 with the ideal that produces reconstruct, and the ideal that deducts this reconstruct from received signal 611 sends signal 615, to produce composite error signal E1 (k)
*+ E2 (k)
*617.Utilize normalized form, can from this composite error signal 617, calculate EVM.
Should understand easily, given data 501aa, 501ba may be handled by the scrambler (for example, in process of transmitting 502a, 502b) of initial state the unknown in emission unit 500.In receiver 600, can utilize and from input signal 321i/321q, data retrieved to solve such uncertainty with the process that all possible scrambler initial state is associated.
According to the discussion of front, as the signal measurement that is depicted among Fig. 6 can be summarized as follows: be used for preamble by for example matched filter, detect the beginning and the character boundary of input signal.The output of matched filter is used to derive the signal(-) carrier frequency skew, in time domain, can from this signal(-) carrier frequency skew, calculate and use suitable frequency correction and (should understand easily, other well-known technology also can be used to reach this purpose, for example, power envelope detects or auto-correlation).
Utilize fast Fourier transform (FFT) to handle the remainder of input signal, for example, be connected on the data of preamble back, a symbol is represented in each FFT output.For each the FFT output with N value, the subclass N1 representative of these values comprises OFDM (OFDM) signal carrier of information.Usually, value N is that 2 power and N1 are approximately equal to N-10.The MIMO preamble structure that is used for M transmitter allows to set up for being present in M the equation that each the OFDM carrier wave N1 that sends signal Y1 (k), Y2 (k) has M unknown number.Find the solution these equations provide amplitude and phase response H1, H2 for each carrier wave that sends in these signals Y1 (k), Y2 (k) estimated value.Amplitude response H1, H2 by filter determine the channel flatness, and determine power level by the power that addition sends each carrier wave among signal Y1 (k), the Y2 (k), and it is unbalance to calculate I/Q by the relevance between near the positive negative carrier of each centre frequency of assessment transmission signal Y1 (k), Y2 (k).
Because the content of preamble is in advance known, and,, can separate signal from various transmitters for each carrier signal because the input preamble has different cyclic shifts.Realize for different multiple-input and multiple-output (MIMO), can use different preambles, such preamble is designed to basic at least quadrature.If initial data is known, then, can allow scrambling ground operate transmitters 500 owing to can utilize matched filter to derive the scrambler setting, and, if the scrambler setting is known, can derive required reference signal.
As the result of preamble, can set up power level from each carrier signal of each transmitter, can therefrom determine available power from each transmitter, and spectrum flatness, the i.e. uniformity of signal power on entire spectrum.The power of each carrier signal of each transmitter and phase place are the indications as the channel response of each transmitter of simulating in filtering 506aa, 506ba.
By comparing the transmitter signal of these separation, the quadrature (I/Q) that can derive each transmitter is unbalance.
If picture in test condition (as mentioned above, take into account the uncertainty of scrambler) expection is such down, data content is known, then can come error of calculation vector magnitude (EVM) by the output of FFT process is compared with the desirable FFT output after using channel correction.The calculating of phase noise can similarly be carried out.By FFT output being asked average, power spectrum that can the calculation combination signal.
Can determine relative timing according to the output peak of matched filter 60.
With reference to Fig. 6 A and 6B, by with frequency domain data signal U1 (k)
*503aa is as an example, and time domain between the signal and frequency domain relation can be described below.With reference to Fig. 6 A, signal U1 (k) is the column vector sequence, and each column vector has N FFT unit, and every row are represented the symbol that divides into groups in the frequency domain.For example, for IEEE 802.11a/g signal, quantity N normally 64, and IFFT and FFT functions are carried out in 64 yuan of vector inputs.Signal U1 (k) is the column vector of k symbol in the grouping.With reference to Fig. 6 B, signal u1 (t) is and the corresponding time-domain signal of U1 (k) (length of preamble is disproportionate).For example, frequency domain vector U1 (2) is corresponding to the time-domain signal u1 (t) on the following time interval t:
T
0+T
CP+2.T
s＜t＜T
0+3.T
s
Frequency-region signal U1 (k) can derive from time-domain signal u1 (t) by following:
U1(k)＝FFT(u1(t)·e
-jωt)
Wherein: t=mT
Sa-kT
s+ T
0+ T
CP
ω=2 π f
c, f
cIt is the frequency of local oscillated signal 529i, 529q
T
SaThe sampling clock frequency of=1/ digital-analog convertor
T
sSymbol duration comprises Cyclic Prefix
T
0The starting point of first symbol after=preamble
T
CPThe duration of=Cyclic Prefix
The k=symbolic number
The m=hits is (for example, for IEEE802.11a/g, m=0:63)
As mentioned above, can test the MIMO transmitter concurrently, wherein, for example, make up the output of transmitter separately, so that the composite signal feed-in can be carried out in the single tester of real signal analysis by power combiner.By utilizing the advanced signal Processing Algorithm, can utilize composite signal to extract many each autoregressive parameters for transmitter separately.This analysis is based on the data of known transmission and the standing part of MIMO packet (for example, data packet header).This ability is extremely beneficial to production system, because it allows only to utilize single tester concurrent testing MIMO transmitting system, thereby provides fast test speed and low cost, has therefore satisfied the minimum requirement that may produce cost.
A kind of test of hope is to measure to be used in the compression separately of the different transmitters in the mimo system and quality metric is assigned to each transmitter.When the transmitter compression sent signal, this had reduced quality of signals, and this can be expressed as the difference that sends signal and ideal signal by EVM great tolerance.For ofdm signal, EVM is expressed as the planisphere of each carrier wave and for example EVM of IEEE.11a/g standard requires difference between the described ideal constellation.Is to measure CCDF (CCDF with compression level with sending a kind of method that chain is associated separately, complementary cumulative distribution function), CCDF is well-known characteristics (this method will more go through below).
With reference to Fig. 7, another kind of method is to characterize the non-linear behavior that causes compression.Can be expressed as follows with its input signal y (t) from output x (t) such as the non-linear element of power amplifier:
x(t)＝a
1 *y(t)+a
3 *y
3(t)+a
5 *y
5(t)+...
Wherein, a
3And a
5It is the non linear coefficient of determining the power of the 3rd and the 5th rank response.Can be always from the compression property of each transmitter of compound signal, i.e. coefficient a
3And a
5In, derive signal quality about each transmitter of its EVM.
By IFFT process 702a, 704a, 704b separately, whenever next symbol ground transforms to time domain with 617, the first local generated ideal transmitter signal 507aa of the composite error signal in the frequency domain and the second local generated ideal transmitter signal 507ba.Handle the first transmitter time-domain signal 705a according to the 3rd rank (706a) and the 5th rank (708a) non-linear process.With 707a, 709a and composite error signal 703e as a result
1(t)
*+ e
2(t)
*Be associated.First correlator output 711a
Be a for first transmitter of each symbol
3The estimated value of item, and second correlator output 711b
Be a for first transmitter of each symbol
5The estimated value of item.Similarly, the 3rd correlator output 711c
Be a for second transmitter of each symbol
3The estimated value of item, and the 4th correlator output 711d
Be a for second transmitter of each symbol
5The estimated value of item.EVM computational process 712 is asked these estimated values on average to grouping, and mean estimates is used for the addressing look-up table, with the expection EVM difference 713a between definite transmitter with based on the EVM estimated value 713b, the 713c that compress.
With reference to Fig. 8 A, test configurations 800a comprises DUT 802, signal combiner 806, VSA 808 and the computer 810 that has a plurality of (for example, two) transmitter 804a, 804b.Computer 810 comprise and move by interface 813 to/provide/receive the DUT Control Software 812 of instruction and data and mutually and by VSA Control Software 814 and the analysis software 816 of another interface 815 from DUT 802 with VSA808 swap data and instruction.
With reference to Fig. 8 B, in alternative test configurations 800b, switch 820a, 820b are inserted between transmitter 804a, 804b and the signal combiner 806, and are subjected to the commands for controlling from VSA in the computer 810 and switch Control Software 814b.
With reference to Fig. 8 C, in alternative test configurations 800c, signal combiner 806 is removed, and directly measures each transmitter output 805a, 805b by its VSA 808a, 808b.
Referring again to Fig. 8 A,, in the compression that changes the second transmitter 804b, compress with constant output signal 805a and to operate the first transmitter 804a, thereby produce the EVM of 32dB according to a kind of test configurations.Utilize single VSA 808 to measure the EVM of the second transmitter 804b.In order to obtain the EVM benchmark, utilize the VSA808 that only is connected with the second transmitter 804b, that is, do not add the signal 805a of the first transmitter 804a, directly measure EVM from the second transmitter 804b.
With reference to Fig. 9 A and 9B, can compare the EVM of two kinds of measurements.Trunnion axis illustrates the EVM of the second transmitter 804b when utilizing reference software to analyze.Vertical axis illustrates the error (being unit with dB) of EVM when using the duplex measurement technology.Be intended to the fc-specific test FC used for the IEEE802.a/g system for this, because the limit accepted of peak data rate is-25dB, so interested especially EVM scope is between-24 to-27dB.Fig. 9 A illustration two transmitters be configured to situation about sending with equal power (before the compression), and Fig. 9 B illustration the first transmitter 804a be in than the situation on the high 1 decibel level of the second transmitter 804b.In interested scope, error presents little positively biased, and Fig. 9 A has+/-error range of 1dB, and Fig. 9 B has+/-error range of 1.5dB.These tests are to carry out at the short relatively grouping of having only 24 symbols.The length that increases grouping will improve precision.
With reference to Figure 10 A and 10B, the EVM of each transmitter 804a, 804b can be subjected to the influence in other harmful source.By relatively sending the interrelation level of chain, can monitor the compression of each transmitter from difference.With the ratio of trunnion axis as the 3rd rank incidence coefficient
Function, and with vertical axis poor as the EVM between transmitter 804a, the 804b, Figure 10 A illustration transmitter output signal 805a, the 805b situation that (not being non-linear) equates on power before compression, and Figure 10 B illustration the first transmitter 804a be in than the situation on the high 1 decibel level of the second transmitter 804b.
The another kind of test of wishing is to measure the compression separately that is used in the different transmitters in the mimo system.At the high signal of peak-to-average force ratio, for example in the ofdm signal, often measure compression, and the important information that can help to examine transmitter performance is provided with the form of CCDF.In well-designed system, will send signal power and adjust on certain compression level, make to satisfy to send quality requirement.Reduce output signal power the power supply power consumption will be increased, will make system become dark output signal compression, send on the point that quality drops to the transmission quality limitations that systematic function may be differed from thereby make but improve power.
With reference to Figure 11 A, the typical CCDF curve representation signal of IE EE 802.11a/g (OFDM) transmitter has X-dB or higher instantaneous power with respect to average power probability.The measurement CCDF of the typical well-designed transmitter of curve 1102 representatives, and the theoretical CCDF that curve 1104 is represented when not having Signal Compression.On trunnion axis, and probability is on vertical axis with respect to the skew of average power.The end points 1106 of compression CCDF curve can be represented compression level, because it has pointed out the compression degree at the top of input signal.In this example, output signal is compressed about 3dB with respect to theory signal.This point 1106 may have some to change with the grouping of short data more because because to reach the probability of this summit level relatively low, packet content (compression) may not can follower theory curve 1104 accurately.Therefore, though this point 1106 usually is used to visually discern compression, should only be counted as the indication of compressing.
CCDF is the relative simple function that can derive separately.Problem is, in producing equipment, people seek the signal that for example has the high compression that is caused by bad circuit block usually.In the single-shot transmitter system, people can easily identify the compression (Figure 11 A) that higher curvature is the indication of compression.Signal can present with respect to the peak power of absolute power up to 10dB, but the transmitter of measuring output may only illustrate the summit of about 7dB; Therefore, transmitter is compressed to about 7dB with the top.Because these peak levels are rare relatively, such compression generally can not influence transmitter performance to being enough to prevent that normal performance tolerance limit of basis and error correction from recovering to send data.If two transmitters show identical compression, this also is like this for mimo system.
But the mimo system that has the imperfection transmitter may produce compressed signal and non-compressed signal, thereby presents different signal transfer characteristics.If as for multithread MIMO signal, signal peak is uncorrelated, then may be difficult to measure compression by observing composite signal.If two signals demonstrate not compression, then absolute peak will be than the peak value of each signal high 3dB.But, the also high 3dB of RMS power, therefore the peak to average of maximum 10dB is held.If a signal demonstrates not compression, and another has demonstrated some compressions, for example, and aforesaid 7dB peak-peak (CCDF will stop at 7dB), when two signals of combination, CCDF will demonstrate summit and reduce about 1.3dB (for the rms signal power that equates).If compression increases to 5dB, compound CCDF will only illustrate the 1.8dB compression with respect to theory signal, if further be reduced to the 3dB summit, then CCDF will show the 2.2dB with respect to theory signal.Usually, compression with the performance limitations of transmitter to the summit scope between 6.5dB and the 7dB, if fault has taken place in one of two transmitters, the whole M IMO system imperfection that becomes.
With reference to Figure 11 B, Figure 11 B shows the comparison between the CCDF curve compound and CCDF separately of dual transmitter MIMO signal.Curve 1108 is theoretical curves of MIMO ofdm signal, and curve 1110 is compound (combination) CCDF.The curve of the not compression input of one of two MIMO transmitters is almost identical with theoretical curve 1108.Curve 1112 is about another MIMO transmitter, and pointed out the obvious compression approaching with the best alignment transmitter.Therefrom can know and find out, utilize CCDF measurement that considerably less information is provided composite signal.People almost can not distinguish composite signal and theory signal, and one of transmitter are compressed to the maximum that is used for better systems simultaneously.Therefore, to measure CCDF fully be impossible to the utilization single traditional instrument that can measure CCDF as production test equipment is usually desirable.But CCDF is the hope analysis tool that usually can help to improve production test speed, because it is simple analysis and the important insight compound to signal is provided.
By measuring composite signal EVM, can identify other contributor to compound EVM, then, also by understanding compression property, can determine whether the EVM contribution is similar for the unlike signal transmission path, or whether a kind of effect of signal transmission path arranges compound EVM.
With reference to Figure 12 A and 12B, the compressed format (Figure 12 B) of desirable not time samples of compressed signal (Figure 12 A) and identical time samples relatively will disclose in time domain do not influence peak with the curve 1102 similar CCDF characteristics of Figure 11 A and compression and decays than peak value greatly greater than the fact than small leak.
With reference to Figure 13 A and 13B, for the composite signal of two MIMO signals, result when Figure 13 A has described that two signals do not compress, and Figure 13 B described one of two signals be compressed to as be depicted in Figure 11 A 1102 in level the time the result.Therefrom as can be seen, in some cases, can see compression, and in other cases, signal continues to present whole summit.As expected, the peak value of compressed signal (Figure 13 B) is less, but not with benchmark not compressed signal (Figure 13 A) relatively be difficult for identifying compression.
With reference to Figure 14 A-14C, two send signal (Figure 14 A and 14B) respectively and produce composite signal (Figure 14 C), wherein as can be seen, in some cases, a signal domination summit, in other cases, another signal accounts for mainly, and under other situation, two signals reach peak value simultaneously, thereby make the peak value of composite signal higher.
With reference to Figure 15 A-15D, the identical signal of transmission respectively (Figure 15 A and 15B) has produced another composite signal (Figure 15 C), but a Signal Compression (Figure 15 A) and another signal does not compress (Figure 15 B).In order not compare, also produced another composite signal (Figure 15 D) with there being Signal Compression.
As mentioned above, if the data that send via the MIMO signal are known, then can estimate desirable composite signal and therefrom estimate EVM.This process is extracted received signal, in frequency with on the time it is aimed at the ideal basis calibration signal, and it is compared with reference signal, the signal of extraction and reference signal respectively be depicted among Figure 15 C and the 15D those class signals seemingly.From seeing the signal measurement separately, there are two reference signals separately, therefore, also there is signal separately.Therefore, can discern the different peak maximums of two signals, and they how with compound (combination) signal association.Utilize this knowledge, can at this point, desirable composite signal can be compared with actual measured signal, and can determine the compression of main signal as one of signal of main contributor another point analysis composite signal of domination on power.
With reference to Figure 16, basically as shown in the figure, obtain measuring-signal and an example of circuit 1600 that it is compared with reference signal comprises: signal envelope testing circuit 1602,1614a, 1614b; IIFT circuit 1612a, 1612b; Threshold value comparison circuit 1616a, 1616b; Switching circuit 1604a, 1604b; Power calculation circuit 1606a, 1606b; With histogram calculation circuit 1608a, 1608b.Detected envelope input sampled data vector signal 321i/321q, and make them can be used for switch as control signal 1617a, 1617b are determined (following discussion).The power level of switching signal 1605a, 1605b utilizes gained signal power data 1607a, 1607b to determine that gained signal power data 1607a, 1607b are used to calculate the CCDF curve of each transmitter.
By they IFFT process 1612a, 1612b separately, local generated ideal transmitter signal 507aa, the 507ba that will be in the frequency domain transform to time domain.Detect the envelope of transmitter time-domain signal 1613a, 1613b, and with separately threshold, to determine the low-power point of transmitter signal.As mentioned above, gained control signal 1617a, 1617b are used for switch or enable the envelope of the composite signal envelope 1603 of detection.
Alternative technology comprises that utilization iterates means and other mutation of the actual derivation of the CCDF curve of transmitter separately, all technology all based on the comparison unlike signal to know the relative power of signal, the basic means that the result is compared with the compound CCDF curve of measurement then.
Various other modifications and changes of structure of the present invention and method of operation are conspicuous for the person of ordinary skill of the art, and they do not depart from scope and spirit of the present invention.Although the present invention is described, should be understood that desired invention should exceedingly not be confined to such specific embodiment in conjunction with certain preferred embodiment.Appending claims is intended to define scope of the present invention, thereby is encompassed in structure and method within the scope of equivalent of these claims and they.
Claims (12)
1. device that comprises the vector signal analyzer that is used for testing simultaneously a plurality of OFDMs (OFDM) signal comprises:
Signal transformation part is used for conversion and receives and comprise the composite data signal of a plurality of ofdm signals via signal communication paths, so that the data-signal after a plurality of conversion is provided, wherein,
Described composite data signal is derived from the remote signal sources with a plurality of signal process of transmittings associated therewith, and comprises that a plurality of packets, each of a plurality of packets comprise the part separately of a plurality of preamble data and the part separately of a plurality of transmission data,
Relevant with described signal communication paths part separately separately of the described part separately of each of described a plurality of transmission data and described a plurality of signal process of transmittings corresponding to a plurality of given datas, and
Each of data-signal after described a plurality of conversion comprises the part separately of described a plurality of packets; And
Signal Processing Element, be used to receive and handle the described at least part separately of described a plurality of given data, described a plurality of preamble data and the described at least part separately of described a plurality of transmission data, so that a plurality of test datas of indicating the error vector magnitude (EVM) that is associated with described composite data signal are provided.
2. device according to claim 1, wherein, described signal transformation part comprises:
Signal detecting part, be used to detect a plurality of characteristics of described composite data signal, so that provide and one the time started separately of the frequency of described composite data signal, described a plurality of packets and the corresponding a plurality of control datas of character boundary of the data in described a plurality of packet;
The signal frequency correcting unit is used for responding by the frequency of proofreading and correct described composite data signal the part of described a plurality of control datas, so that the corresponding data signal with expectation nominal frequency is provided;
Signal conversion part is used for described corresponding data conversion of signals is become a plurality of parallel data signals; And
The fast Fourier transform (FFT) parts are used for the described a plurality of parallel data signals of conversion, so that the data-signal after described a plurality of conversion is provided.
3. device according to claim 1, wherein, described Signal Processing Element comprises:
The preamble processing unit is used to handle the described at least part separately of described a plurality of preamble data, so that a plurality of at least control datas are provided;
Data processor is used for responding described a plurality of control data, so that a plurality of reconstruction signals are provided by according to handling described a plurality of given data to the similar substantially a plurality of processes of described a plurality of signal process of transmittings at least; And
The signal plus parts are used for data-signal and described a plurality of reconstruction signal after the described a plurality of conversion of addition, so that described a plurality of test data is provided.
4. device according to claim 3, wherein, described preamble processing unit is further used for handling the described at least part separately of described a plurality of preamble data, so that a plurality of additional datas of one or more signal transfer characteristics of the described a plurality of ofdm signals of indication are provided.
5. device according to claim 4, wherein, described one or more signal transfer characteristics comprise one or more in the unbalance and spectrum flatness of each power level, orthogonal signalling of described a plurality of ofdm signals.
6. device according to claim 1 further comprises the signal spectra analysis component, is used to analyze one or more spectral properties of described composite data signal, so that at least one a plurality of spectrum data of the described one or more spectral properties of indication are provided.
7. method that is used for testing simultaneously a plurality of OFDMs (OFDM) signal comprises:
Conversion receives and comprises the composite data signal of a plurality of ofdm signals via signal communication paths, so that the data-signal after a plurality of conversion is provided, wherein,
Described composite data signal is derived from the remote signal sources with a plurality of signal process of transmittings associated therewith, and comprises that a plurality of packets, each of a plurality of packets comprise the part separately of a plurality of preamble data and the part separately of a plurality of transmission data,
Relevant with described signal communication paths part separately separately of the described part separately of each of described a plurality of transmission data and described a plurality of signal process of transmittings corresponding to a plurality of given datas, and
Each of data-signal after described a plurality of conversion comprises the part separately of described a plurality of packets; And
Receive and handle the described at least part separately of described a plurality of given data, described a plurality of preamble data and the described at least part separately of described a plurality of transmission data, so that a plurality of test datas of indicating the error vector magnitude (EVM) that is associated with described composite data signal are provided.
8. method according to claim 7, wherein, described conversion comprises:
Detect a plurality of characteristics of described composite data signal, so that provide and one the time started separately of the frequency of described composite data signal, described a plurality of packets and the corresponding a plurality of control datas of character boundary of the data in described a plurality of packet;
Respond the part of described a plurality of control datas by the frequency of proofreading and correct described composite data signal, so that the corresponding data signal with expectation nominal frequency is provided;
Described corresponding data conversion of signals is become a plurality of parallel data signals; And
Come the described a plurality of parallel data signals of conversion according to fast Fourier transform (FFT), so that the data-signal after described a plurality of conversion is provided.
9. method according to claim 7, wherein, described reception and processing comprise:
Handle the described at least part separately of described a plurality of preamble data, so that a plurality of at least control datas are provided;
By according to handling described a plurality of given data to the similar substantially a plurality of processes of described a plurality of signal process of transmittings at least, respond described a plurality of control data, so that a plurality of reconstruction signals are provided; And
Data-signal after the described a plurality of conversion of addition and described a plurality of reconstruction signal are so that provide described a plurality of test data.
10. method according to claim 9, wherein, described processing further comprises: handle the described at least part separately of described a plurality of preamble data, so that a plurality of additional datas of one or more signal transfer characteristics of the described a plurality of ofdm signals of indication are provided.
11. method according to claim 10, wherein, described one or more signal transfer characteristics comprise one or more in the unbalance and spectrum flatness of each power level, orthogonal signalling of described a plurality of ofdm signals.
12. method according to claim 7 further comprises: analyze one or more spectral properties of described composite data signal, so that at least one a plurality of spectrum data of the described one or more spectral properties of indication are provided.
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| US59644405P | 2005-09-23 | 2005-09-23 | |
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| US11/533,971 US7822130B2 (en) | 2005-09-23 | 2006-09-21 | Apparatus and method for simultaneous testing of multiple orthogonal frequency division multiplexed transmitters with single vector signal analyzer |
| US11/533,971 | 2006-09-21 | ||
| PCT/US2006/036995 WO2007038279A2 (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 (6)
| Publication number | Priority date | Publication date | Assignee | Title |
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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 |
| CN102624469A (en) * | 2011-01-31 | 2012-08-01 | 英特尔移动通信有限公司 | Communication terminal, communication device, method for measuring a signal and method for requesting a measurement |
| CN104885388A (en) * | 2012-12-10 | 2015-09-02 | 高通股份有限公司 | Reconfigurable receiver circuits for test signal generation |
| CN107508642A (en) * | 2017-07-07 | 2017-12-22 | 湖北大学 | A kind of Nonlinear Evaluation System and method for of high order modulation communication system |
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| Publication number | Priority date | Publication date | Assignee | Title |
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| US9002290B2 (en) * | 2012-05-09 | 2015-04-07 | Litepoint Corporation | System and method for testing a radio frequency (RF) multiple-input-multiple-output (MIMO) device under test (DUT) |
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| Publication number | Priority date | Publication date | Assignee | Title |
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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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2006
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| Publication number | Priority date | Publication date | Assignee | Title |
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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 |
| CN102624469A (en) * | 2011-01-31 | 2012-08-01 | 英特尔移动通信有限公司 | Communication terminal, communication device, method for measuring a signal and method for requesting a measurement |
| CN102624469B (en) * | 2011-01-31 | 2014-09-24 | 英特尔移动通信有限公司 | Communication terminal, communication device, method for measuring a signal and method for requesting a measurement |
| CN104885388A (en) * | 2012-12-10 | 2015-09-02 | 高通股份有限公司 | Reconfigurable receiver circuits for test signal generation |
| CN104885388B (en) * | 2012-12-10 | 2017-07-28 | 高通股份有限公司 | Method and apparatus for receiving radiofrequency signal |
| CN107809404A (en) * | 2016-09-09 | 2018-03-16 | 中兴通讯股份有限公司 | A kind of method and apparatus of estimate symbol skew |
| 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 |
| CN107508642A (en) * | 2017-07-07 | 2017-12-22 | 湖北大学 | A kind of Nonlinear Evaluation System and method for of high order modulation communication system |
| CN107508642B (en) * | 2017-07-07 | 2020-09-11 | 湖北大学 | Nonlinear evaluation system and method of high-order modulation communication system |
| CN115361076A (en) * | 2022-08-10 | 2022-11-18 | 深圳市极致汇仪科技有限公司 | MIMO radio frequency channel test method |
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