A current source modulator (202; 302, 502) provides power to radar transmitters.
The modulator comprises a power supply (210, 310, 510) providing, when enabled,
a known current to a storage capacitor (145). A comparator circuit (220)
provides a signal (V220) when voltage (VC) across the storage
capacitor (145) falls a reference voltage, and an enable circuit (225)
responds to the comparator signal (V220) and an ON command signal to enable
the power supply (210, 310, 510). The modulator (202, 302, 502) further
includes a network (220N) associated with the comparator circuit (220)
to retain the value of the signal (provide hysteresis) when the voltage across
the storage capacitor is above the reference voltage. The modulator (202, 302,
502) may include a second network (320N) associated with a second comparator
circuit, operable to retain a second signal when capacitor (145) voltage
VC is above a reference voltage. In this aspect, there is a rapid charge
and a trickle charge that reduces any charging overshoot.