Tektronix AWG 2021 Manual de usuario Pagina 1

Signals and Measurements forWireless Communications Testing

10The 11 tone equation was thenmodified so that the last 5 tones(71 through 75 MHz) areinverted. The two differentmulti-tone results are shown inFigur

11Frequency modulation introducescontrol of the phase argument,Φ, in the basic carrier equation:A sin (ωct + Φ ).FM is implemented by varyingΦ in dire

12While basic single-tone FM is abuilt-in function of virtually allconventional signal generators,dual-tone FM modulation clearlycontrasts the flexibi

13Figure 13. The TDS 744A shows the intermodu-lation performance with expanders disabled andenabled. There is no distortion with the expanderdisabled.

14A final example of conventionalanalog modulation combinesmost of the above techniques tosimulate the stereo modulationused in broadcast FM. Themodul

15The resulting 455 kHz signal ismixed up to the broadcast bandand inserted into a stereoreceiver. The stereo indicator isturned on, and the resulting

16Although the removal of noise isa common design goal, a noisesource can be an extremelyuseful test stimulus or signalimpairment. The AWG 2041provide

17the AWG’s 10 MHz low-passfilter (middle trace). TheTDS 744A FFT spectra for thetwo signals are overlaid belowthe time domain waveforms. Thesalient c

18The AWG’s graphical waveformeditor provides a variety ofmathematical operators for exist-ing waveforms. Waveforms canbe combined with otherwaveforms

19Digital Phase Modulation — PSK8The modulating signals in theforegoing examples have beensinusoidal or continuous wave-forms. A simple step to digita

2Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1Analog Carriers and Modulation1 Basic Sine Wave Amplitude Modulatio

20The record length of 1024 pointsand a waveform period of 1 µsrequires a sampling rate of1.024 GHz. The resulting carrierfrequency is 50 MHz. Since e

21Baseband Digital Patterns9Before continuing with exam-ples of digital modulation, it isimportant to establish a methodof creating arbitrary test dat

22The simplest example of digitalmodulation is to turn the carrieron or off, depending on the stateof the modulation data. On-offkeying (OOK) can be d

23The modulating data alters thecarrier frequency infrequency-shift keying (FSK). Adigital modulation index of 0.5is used in this example; that is,the

24As previously mentioned, theAWG’s two binary markeroutput signals can be modulatedwith a data pattern. Figure 30shows how this can be used as atool

25Multi-level data modulationsplits the amplitude, frequency,or phase of the carrier into morethan two discrete states. 8-PSKpreviously demonstrated d

26Figure 32. Quadrature amplitude modulated(QAM) signal generated by combining anamplitude modulated cosine carrier (upper) andan amplitude modulated

27One effect of the edge transitionsin digital modulation patterns isa wider than desired occupiedspectrum of the transmittedsignal. The solution is t

28The convolution result is 30,000points long. Note that theimpulse response is 2000 pointslong, which is longer than the1000 points per data bit. Thi

29Figure 36 compares the originaland filtered data patterns. Theupper two traces are the unfil-tered data pattern and its spec-trum. The lower two tra

3One of the most challenging tasks in designingwireless communications products is the develop-ment of a rational approach to characterizing andtestin

30The final example of digitalmodulation spreads the energyin a BPSK signal by amplitudemodulating the carrier with aspreading pattern. In the sameway

31For More Information on Tektronix InstrumentationTektronix offers a broad line of signal sources and electronic measurement products for engineering

32Tektronix AWG ArbitraryWaveform Generators give themost extensive capabilities forediting waveforms, with 8 or 12bits of vertical resolution andwave

33The TDS 744A represents thenext generation of digitizingscope performance. This versa-tile general-purpose instrumentintroduces Tek’s new InstaVu™ac

34

35

364/97 WCI 76W–10555–1Copyright © 1997, Tektronix, Inc. All rights reserved. Tektronix products are covered by U.S. and foreign patents, issued and

4

5The best introduction to theAWG is to parallel the procedureof generating a carrier with aconventional signal generator.With a signal generator, ones

6A record length must be selectedthat has an adequate number ofpoints to reconstruct the desiredwaveform. The waveform periodis 1 ms and there are 100

7A simple addition to the AMsignal demonstrates the flexibilityof equation-based waveformdescriptions. A common task inevaluating receiver performance

8Frequency (kHz-90-80-70-60-50-40-30-20-100980 985 990 995 1000 1005 1010 1015 1020Figure 6. Spectrum analyzer plot of the 3 carriers.There are 3 kHz

9Multi-Tone Testing3The logical extension of adjacentcarrier testing is multi-tone test-ing. In addition to simulatingmultiple carriers in a multi-cha