Connectors and Adapters

Connectors are needed to join different lines, devices, and circuit blocks together. An ideal connector is matched and lossless. Practical connectors cause small discontinuities. Therefore, unnecessary use of connectors should be avoided. The quality of connectors gets more and more important as the frequency gets higher.

Figure 6.22 shows some common coaxial connectors used at RF and microwave frequencies. An APC-7 connector is a precision connector that is used in measurements requiring good accuracy and repeatability. It is a sexless connector whose inner diameter of its outer conductor is 7 mm. SMA and N connectors are good enough for most cases. These connectors can be either male or female type. BNC connectors work best at frequencies below 1 GHz; at higher frequencies they may radiate. Waveguide components have flanges at their ports. Alignment pins on the flanges ensure accurate connection.

Figure 6.22 Some common coaxial connectors.

Adapters are needed to connect components having connectors of different types or of the same sex. Figure 6.23(a) shows a transition from a coaxial line to a microstrip line. Coaxial and waveguide components can be connected using the adapter illustrated in Figure 6.23(b).


[1] Collin, R. E., Foundations for Microwave Engineering, 2nd ed., New York: IEEE Press, 2001.

[2] Pozar, D. M., Microwave Engineering, 2nd ed., New York: John Wiley & Sons, 1998.

[3] Rodrigue, G. P., "A Generation of Microwave Ferrite Devices,'' Proc. IEEE, Vol. 76, No. 2, 1988, pp. 121-137.

[4] Fay, C. E., and R. L. Comstock, "Operation of the Ferrite Junction Circulator," IEEE Trans. on Microwave Theory and Techniques, Vol. 13, No. 1, 1965, pp. 15-27.

[5] Lahey, J., "Junction Circulator Design,'' Microwave Journal, Vol. 32, No. 11, 1989, pp. 26-45.

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