Figure 66. High-Level Modulator With
Reverse-Current Diode.
3. So you see, when reflections occur because of impedance mismatch, the
voltage on the PFN does not remain constant and the applied voltage to the
pulse transformer varies.
Also, if the PFN voltage is not constant from
pulse to pulse, the applied voltage to the magnetron is not constant either.
Likewise, magnetron power output varies, causing frequency modulation.
Therefore, the PFN voltage must be held constant from pulse to pulse. This
is the job of the reverse-current diode.
Learning Event 8:
REVERSE-CURRENT DIODE
1. Part B of Figure 66 shows the action of the reverse-current diode, V4.
At the end of the discharge cycle, a negative pulse is reflected into the
pulse transformer primary because of impedance mismatch.
This negative
pulse makes V4 conduct and a reverse current flows from ground, through the
pulse
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