1_230 Lab Manual Winter2016.pdf

Vi experiment 22 lossy and lossless lines on the

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VI. Experiment 2.2: Lossy and Lossless Lines on the Smith Chart In this experiment, you will use the network analyzer in the Smith Chart display format to show graphically how a wave behaves on a lossy and a lossless line. At low frequencies, it is very difficult to make a lossy line. In this lab, you will be using a lossy line simulator (see Fig . 2N3) that has been made to demonstrate the response of a lossy line on a network analyzer. The lossy line simulator consists of a piece of wire soldered to a BNC connector and is housed in a metal box . Carbon absorber has been placed in the box to make the system more lossy. The wire acts essentially as a small antenna element . The impedance of the antenna element changes with frequency . In addition, the line radiates energy into the carbon absorber where the energy is converted to heat (a tiny amount) . These two effects give the lossy line simulator the same characteristic response as a lossy line. Fig. 2N3: The lossy line simulator
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38 Setup This experiment uses the network analyzer, a patch cord and the lossy line simulator. Procedure 1. Using the Smith Chart (R + jX) network analyzer settings as previously used, connect the patch cord (lossless line) to channel 1 of the network analyzer leaving its other end open . Capture the resulting display. 2 . Connect the lossy line simulator to the end of the patch cord using an N jack to BNC plug adapter (shown below) . Capture the resulting display. Measured Data There were no measurements made for this section, only the two printouts. Analysis 1 . Qualitatively comment on the display produced by the lossless patch cord . Why do you see a series of circles as the response? Are the circles relatively stationary in their position on the Smith Chart, that is, do they overlap each other or is there a “spiral” pattern? Why? 2 . Qualitatively comment on the display produced by the lossy line simulator. Are the circles relatively stationary in their position on the Smith Chart, that is, do they overlap each other or is there a “spiral” pattern? Why? Questions 1 . If the lossy transmission line was nearly infinite in length, to where would the response spiral? Why? Explain in terms of reflected power.
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39 VII. Experiment 2.3: Impedance Measurements using the Smith Chart In this experiment you will use the network analyzer in the Smith Chart display format to make load impedance measurements. Setup This experiment uses the network analyzer and various loads. Connect the patch cord to channel 1 of the network analyzer. Press PRESET and OK . Set the start frequency to 200 MHz. Set the stop frequency to 1.2 GHz. Set the display format to Smith Chart. Perform a oneNport calibration following the procedure outlined in Exercise 1. Procedure 1 . Connect the short termination to the end of the patch cord using an N to N adapter . Capture the resulting display . Record the values of the impedances at 400 MHz, 600 MHz, 800 MHz, and 1.0 GHz, as shown in the table in the Measured Data section that follows . ( Hint : To speed up the
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  • Winter '08
  • RAND
  • BNC

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