How to Improve Spurious Levels in Pulsed RF Amplifiers

Many modern applications like radar and electronic warfare (EW) need pulsed RF amplifiers.The accuracy of these systems relies on the fidelity of the pulsed RF signal. Think about it this way: a pulsed RF amplifier should behave as closely to an ideal amplifier as possible. Any signal found at the output of an amplifier that is not present at the input is considered a spurious signal. The result? Those spurious signals may show up as false targets or blurred images in radar and medical systems – or bit errors in communication systems. This compromises reliability and brings with it a host of other challenges.

Interestingly, some systems can tolerate spurs. But this depends on their amplitude and distance from the carrier. Design engineers can certainly determine the maximum level and frequency of spurs a particular system can accept. However, in many industries, designers must figure out how to reduce spurious levels in the first place. One way to do this is to examine the source of spurs in traveling wave tube amplifiers (TWTAs) and reduce them using either “nesting” or “pulse shaping.”

So how do design engineers figure out which method to use? It depends on the system. It also requires a delicate (but doable) balance between spurious output and duty cycle budget. Fortunately, our VP of Engineering, Jacob Thampan, wrote an article about this very subject. Read it here.