The dynamic range of the six-port type of automatic network analyzer is typically limited to measuring two-port devices with a transmission coefficient S12 in the range of 0 to -60 dB. The following describes a subcarrier approach for extending the dynamic range of the dual six-port network analyzer. The subcarrier is generated by inserting a 10-kHz, biphase modulator ahead of one of the six-ports. With the subcarrier approach, measurements of S12 in the range of -60 to -100 dB can be made. Test results are presented showing measurements of S12 = -80 dB with a precision of ±0.05 dB or better, and an accuracy of ±0.16 dB or better at 3 GHz. Measurement results are also presented showing the dynamic range achievable with thermistor and barretter detectors.
John R. Juroshek, Cletus A. Hoer, "A technique for extending the dynamic range of the dual six-port network analyzer," IEEE Transactions on Microwave Theory and Techniques, vol. 33, no. 6, pp. 453-459, June 1985.
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