Pulsed versus CW operation

Updated August 16, 2008

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New for September 2008! And of course under construction... Pulsed and CW (continuous wave) refer to transmitter operation. Typically a transmitter is pulsed on and off, at a specific duty cycle, this is especially true of radar systems.

Before we even get to this topic, let's discuss the word "versus". How many times must we see the word abbreviated "vs." before we lose our minds? This is a small word, it doesn't need to be shortened. Cut it out! And remember that "verses" is not the same as "versus". Learn how to use the English language good, like us does.

Back onto the topic.

In a radar, the transmitter is turned on for a short time, then shut off while the receiver looks for the return signal. The power amplifiers in the transmit chain are almost always turned on and off going from transmit to receive, this saves energy, reduces waste heat and minimizes temperature rise in solid-state and tube devices.

Time for a Microwaves101 Rule of Thumb!

When a solid state amplifier is pulsed on for 100 microseconds or longer (so-called "long" pulse), it reaches a quasi-steady-state junction or channel temperature, so for thermal and reliability analysis, this case can be considered the same as continuous wave. Under the same operating conditions, to get any reliability benefits from pulsed operation you need to operate with pulses of 10 us or less ("short" pulse)