Abstract: An apparatus and method for improving stability in a transmitter receiving a staggered pulse train includes maintaining a constant temperature of the transmitter at the start of each pulse of the pulse train. Such maintenance may be accomplished by inserting "false", "phantom" or "synthetic" pulses into the pulse train. These pulses may be inserted between pulses, prior to a cooler pulse, or after a hotter pulse. The inserted pulses are then gated out prior to the final RF transmission.

Abstract: A tunable narrow-band filter is described incorporating a phase-locked loop that includes a phase detector, amplifier, loop filter, and voltage controlled oscillator wherein the loop filter transfer function is derived or extracted from the desired closed-loop transfer function that is of order n=3 or greater. The loop filter may furthermore have finite transmission zeros or peak attenuation at specific frequencies close to the passband which also appear in the characteristics of the narrow-band filter.The invention overcomes the problem of providing peak attenuation close to the passband of an electronically tunable narrow-band filter.