| 摘要 |
A precision transmission line in the form of a short air line, and calibration of a network analyzer using the short air line, are disclosed. The short air line is approximately one-quarter wavelength at the middle frequency of the measurement frequency range. One embodiment comprises a very short coaxial air line. The inner conductor is threaded onto a mating inner conductor, such as the inner conductor of the network analyzer test port. For reliable interface at the other end of the inner conductor, a precision coaxial connector is preferably provided for connection to a device under test. The outer conductor is then attached coaxially to the inner conductor between the network analyzer test port and the device under test. Another embodiment comprises a waveguide for calibrations at higher measurment frequencies. In the case of the waveguide, locating structure is provided for properly orienting the waveguide with respect to the network analyzer test port and the device under test. The invention further provides a one-port calibration method for enhancement of the accuracy of a network analyzer using the short air line. An offset-load calibration in accordance with the invention comprises the following measurements: (a) a fixed load (stable but not necessarily any better than 30 dB return loss); (b) the short air line terminated with the same load; (c) a short circuit; and, (d) the short air line terminated with the same short circuit. The electrically short air line provides a very precise element for use in the offset-load, as well as other calibrations of network analyzers.
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