Radar System Engineering

416 R-F COMPONENTS [SEC. 11.8
early, hurries the oscillation and increases the frequency. Reflectorvoltage
tuning ranges of 30 to 50 Me/see between the half-power points
are normal, and the tuning rate may lie between 1 and 4 Me/see per volt.
Electrical tuning is the basis of automatic-frequency-control systems.
Figure 11.24 shows an exterior and an x-ray view of a 2K25, a widely
used local oscillator for the 3-cm band. The coaxial output line ends in a
probe which is inserted in the waveguide to form a matched transition
like that shown in Fig. ll”12a.
11.8. The Mixer.-The mixer’ contains the crystal. It has two sets
of input terminals, one for the received signal and one for the local oscillator;
the output signal goes to the first stage of the i-f amplifier. The
requirements to be met are as follows: (1) the crystal must be made to
appear as a matched load to the incoming signal; (2) there must be
1MicrowaveMizers,
Vol. 16, Radiation Laboratory Series