1_230 Lab Manual Winter2016.pdf

4 measure the input return loss of the system at the

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4. Measure the input return loss of the system at the resonant frequency of the 9 cm loop for coupling distances from 2 cm to 16 cm in 2 cm increments with the loops axially aligned. Press MEAS and S11 Press FORMAT Press the Log Mag softkey Press MARKER Insert a marker at the resonant frequency of the 9 cm loop
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113 For our purposes, a good input return loss is at least 10 dB. If the return loss is lower than this at ! ! , check all connections. 5. Measure ! !" (in dB) of the system at the resonant frequency of the 9 cm loop for coupling distances from 2 cm to 16 cm in 2 cm increments with the loops axially aligned. Press MEAS and S21 Press FORMAT Press the Log Mag softkey Press SCALE Press the Autoscale softkey Press MARKER Insert a marker at the resonant frequency of the 9 cm loop 6. Move the loops away from the matching distance and observe the behavior of the input reflection coefficient. Measured Data Copy the following into your lab notebook and fill in the measured data. If you are missing any data, please repeat the necessary parts of this experiment before proceeding. Output impedance at ! ! (Ω) Rectifier matching network Loop matching network #1 Loop matching network #2 Input return loss of matched rectifier _____ (dB) Distance (cm) Input return loss (dB) ! !" (dB) (constant frequency) 2 4 6 8 10 12 14 16 Analysis (PreNLab) 1. Using eq. (6.15), determine the theoretical power transfer efficiency ! ! ! for coupling distances of 2 cm to 16 cm, in 2 cm steps. The mutual inductance was calculated in Experiment 5.1, the
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114 load resistance was calculated in Experiment 6.1 for 9 cm loops, and the loop resistance was found in Experiment 4.3. Questions 1. Why shouldn’t we use a length of cable between the matching networks and the loops or the rectifier and its matching network? 2. Plot the theoretical and measured ! = ! !" ! efficiencies on the same graph for the constant frequency system. How do they compare? 3. Does the coupling distance with the minimum return loss correspond to the coupling distance with maximum ! !" for the constant ! ! system? VII. Experiment 6.3: [email protected] System Setup 1. If the network analyzer is not already calibrated for reflection and transmission measurements, perform the necessary calibration as described in the Setup of Experiment 6.2. 2. If the system of matched loops (without the rectifier) is not connected to the network analyzer, connect it. Procedure Find the strong coupling resonances: 1. Align the loops axially for maximum coupling. For coupling distances of 2 cm to 18 cm (2 cm increments), find the resonant frequency of the coupled system, i.e. the frequencies with the lowest input reflection coefficient. For strong coupling, there will be three resonant frequencies. The even and odd mode frequencies will have the lowest input reflection coefficient, so record both of these frequencies. When in weak coupling, these two resonant frequencies merge into the selfNresonant frequency !
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  • Winter '08
  • RAND
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