1 1 Lab. 9 Signal Analyzer  Signal/spectrum analyzer (SA): an equipment analyzing spectrum properties of signals.

2 2  Type of SA: –Swept (downconvert one carrier at a time) –Fourier (downconvert a band of carrier at a time)

3 3  Swept analyzer:

4 4  Resolution bandwidth: –The higher the resoultion, the slower the scan.

5 5  Vector signal analyzer: –A SA that can conduct demodulation

6  Fourier analyzer: 6

7  Agilent approach: Hardware Software 7

8 8  Software analyzer: –Analyze the signal recorded by hardware  Load recorded signal: –File  Recall  Recall demo  (Help  Signals)  QPSK  Four windows (traces) are usually used: –Time constellation –Spectrum –EVM (time) –EVM (average number)  Find the length of the recoded signal: –Window  Player  Find the properties of the recorded signal: –Help  Demo

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11  Use the label of each window to select what you want to see – Time – IQ measurement – Spectrum  Use the unit of y-axis to have more selections  Adjust the overlayed percentage: – MeasSetup  Frequency  Time – Change MaxOverlapp – The higher the percentage, the slow the time sweep.  Find out the demodulation properties: – MeasSetup  Digital demodulation properties

12  Use markers: – Add markers from the command bar – Marker  Calculation  select band power (set the center frequency and bandwidth) – Can also use mouse to draw the band. – Use OBW to select the band automatically.  The connect used for general equipment is BNC and that for RF transmission is SMA. For SA, we need to plug SMA into N type. We need some kind of connector transferring SMA to BNC.  The transmitter and receiver are not ideal in real-world. We have to give specifications for their performance so as to insure reliable communications.

13  Analog/RF Impairments: –DAC –Transmit IQ imbalance –Phase noise of the mixer –PA nonlinearity –Channel effect –Noise –Receive IQ imbalance –DC offset –Phase noise of the mixer –ADC –Carrier frequency offset  Digital processing: –Precision (fixed-point processing) –Receiver algorithms

14  How to test/specify a communication system? –Transmitter/receiver performance (separated) –Combine all impairments (combined)  Transmitter: –Transmit signal distortion (for receiver) –Spectrum characteristic (for interference control)  Indices for transmitter –Error vector magnitude (EVM) –Spectrum mask  Index for receiver: –Sensitivity –Interference performance * EVM is usually used for QAM signals.

15  EVM: –A signal sent by an ideal transmitter would have all constellation point at the ideal locations –For real-world transmitter, however, the constellation points will deviate from the ideal locations in a random fashion. –EVM is a measure of how far the constellation points are from the ideal locations * - 30dB~3.16% * - 40dB~1.00%

16  Spectrum mask: –Confine the spectrum used for transmission (interference control for the Bluetooth system) 20dB

17  Practice 1: –Choose at least two kind of signals and analyze the performance of the transmitters.