Читать книгу Handbook of Microwave Component Measurements - Joel P. Dunsmore - Страница 49

There are two variants of the 1.85 mm connectors, designed originally by Anritsu and Agilent. The Anritsu variety is called the V connector, and the Agilent variety is called the 1.85 mm connector. They are mechanically compatible and were originally designed for 67 GHz operation, usable to above 75 GHz. These connectors are mechanically compatible with the 2.4 mm connector. Figure 1.27 shows the wideband response to 85 GHz of the 1.85 mm connector in the upper plot and a zoomed‐in view of the first mode in the lower plot. This first mode is a “bead‐mode” and is caused by the increased dielectric constant of the bead, which holds the center pin, lowering the first mode of the 1.85 mm coaxial line. In general, this mode is non‐propagating (since it is contained in the bead) and may be calibrated out in some circumstances. For example, if this connector is used with an on‐wafer probe and the coax from the connector to the probe‐tip is mode free, then the bead mode will act like a small, stationary resonance that can be removed with a calibration. If the mode is propagating, then changes in the termination impedance change the effects of the mode, and it cannot be calibrated out (it is not stationary with respect to an external impedance); but if it is non‐propagating and there is a sufficient length of mode‐free line (such a cable) between this bead mode and the reference plane, the evanescent fields associated with the mode will die off before arriving at the reference plane and thus will not couple to the terminating impedance. As this first mode is less than 0.2 dB, in many cases it is not significant. The 1.85 mm connector has been used out past 75 GHz.

Figure 1.27 Response of mated pair of male‐to‐male and female‐to‐female 1.85 mm connectors (upper), with zoomed‐in view of the first mode (lower).