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Home < Products < Precision Calibration Standards & Accessories < Open Circuit Terminations - General Information |
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Open Circuit Terminations Shielded, coaxial open circuit terminations ("opens") are used in the calibration of both scalar and vector network analyzers (SNA and VNA, respectively). In both applications, they are used to provide a nominal 180 degree phase offset from a compatible reference short circuit over a broad range of frequencies. |
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In SNA applications, the open is used in conjunction with a short to establish an average for a 100% reflection effectively halving the error due to reflection phase interactions. It is a practical impossibility to build a perfect open circuit at microwave frequencies. Shielding the open essentially eliminates radiation losses; however, this creates a residual requency-sensitive capacitance. For VNA applications, an accurate knowledge of the open circuit effective capacitance is essential to an accurate calibration of the analyzer. Maury opens are generally characterized for effective capacitance versus frequency by means of a fourth order polynomial curve fit, and the nominal capacitance coefficients are provided with each unit. We offer several innovative designs that improve the consistency and repeatability of the open circuit termination capacitance coefficients resulting in improved effective source match of the calibrated VNA 1 . One design (seen in the 14mm and 7mm models (2416D1 and 2416D3 respectively) uses a beadless captivated dielectric rod in place of the center conductor contact. This rod depresses the spring-loaded contact of the test port connector so that is is flush with the outer conductor mating plane. This creates highly accurate, precisely repeatable open circuit conditions which improve the calibration effectiveness and measurement accuracy of the open. Another design (seen in most of the sexed models offered by Maury) uses a center contact that is captivated and set at the factory to be essentially flush with the outher conducctor mating plane, thereby eliminating dependence on test port connector tolerances and adding a high degree of performance consistency to the open. the 371N1/P1, 8585A/B and 8885A/B models are designed for limited frequency ranges as determined by their connector types (50 ohm BNC, 75 ohm BNC, and type N respectively). These models have shielded shells without center conductors or supporting dielectric rods. MORE INFORMATION ABOUT MAURY OPEN CIRCUIT TERMINATIONS: |
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