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Voltage Standing Wave Ratio Bridge Measuring
Circuit. William E. Herzog 1988. US Pat.# 4739515, April 19th 1988. Filed Sept. 27th 1985 Abstract: A method and apparatus for measuring the VSWR on a radio-frequency transmission line. The bandwidth of RF signals over which the apparatus accurately operates is improved by the use of a filter to unload terminating resistors at low frequencies and by the use of an inductive element in the measuring circuit to compensate for phase lag induced by elements of the measuring circuit. The current transformer load resistor is made up of two resistors in parallel, one having a series capacitor, the other having a series inductance. The effect of the inductance is to introduce a leading phase shift at high frequencies to compensate for the transformer propagation delay. The effect of the capacitor is to unload the current transformer at low frequencies, thereby compensating for the shunting effect of the transformer secondary inductance. |
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Cited and related documents: US Pat. 2588390, Jones 1952. US Pat. 2734169, Douma 1956. US Pat. 2797387. Adams, Horvath, Parzen 1957. US Pat. 2808566. Douma 1957. US Pat. 3020529. Turner 1962. US Pat. 3145338. Downs 1964. US Pat. 3683274. Martin 1972. US Pat. 4075554. Mecklenberg 1978. US Pat. 4110685. Leenerts 1978. "VSWR Bridges", Will Herzog K2LB, Ham Radio, March 1986, p37-40. Analysis of Herzog's LF phase compensation method for current-transformers. Analysis, evaluation and optimisation of RF current-transformer bridges (including analysis and testing of Herzog's HF phase-compensation scheme). |
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Test bridge with HF phase neutralisation using Herzog's method.
The inductance of the secondary load resistor is increased by
proxmity to a dust-iron slug. For discussion see Appendix 6.4. |
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