He holds a Bachelor of Science in Electrical Engineering from the University of Utah and a Master of Business Administration from Arizona State University.Get the latest RF/microwave industry news, insights, and analysis delivered to your inbox.This website uses cookies to ensure you get the best experience on our website. This is the measurement you will get from average power sensors, like Anritsu’s MA24208A/18A Universal USB Power Sensors. EXAMPLE#1. For communication signals, engineers may want to know that the signals are transmitting at correct power levels in order to avoid distortion, or to comply with regulatory demands.Average power readings will suffice for any CW signal or in settings where the modulated signal has been characterized well enough that an average power reading will provide sufficient information to verify proper operation. 1/fThis means that the averaging time of the RF power measurement must fall within a window:The peak envelope power is therefore the peak value obtained using this method.Of all the forms of RF power measurement, the average power is the most widely used. However pulse power, sometimes referred to as peak power, and also the peak envelope power also need to be known on many occasions. (with no DC component) A lot of people have a hard time converting between power and voltage in 50 Ω systems. In this way the RF or microwave power meter is able to cater for the majority of waveforms encountered.In a number of applications, it is necessary to measure the power of a pulse of energy. As mentioned earlier, some sensors will provide a crest factor, which is the ratio of average power to peak envelope power. Figure 1: Trace 1 shows the in-phase (I) component and Trace 2 the quadrature (Q) component of a 16 QAM signal. This varies in amplitude over many RF cycles, and the RF power must be averaged over many periods of the modulating waveform to achieve a meaningful result.To achieve the required results, the averaging period for RF power meters may range from several hundredths of a second up to several seconds. If you’re using an average or RMS sensor, the video bandwidth is mostly irrelevant to its ability to make the measurement you need.With a better understanding of the definitions, it’s time to ask yourself which measurements you need for your specific application. As the signal is a single frequency steady state waveform, the average power is obvious.For other waveforms the averaging parameters may be of greater importance. In this case, the PBAvg is equal to Pavg divided by the duty cycle, where the duty cycle is the pulse width divided by the pulse repetition interval. Most power meters/sensors are not fast enough, so a high-speed digitizer or digital storage oscilloscope (DSO) would be required. In order to measure the power of the pulse itself, a method of defined exactly what must be measured.As the name pulse power implies, the power of the actual pulse itself is measured.


It’s also possible to damage test instruments with a high enough peak power, even if the average power is within the specified limits.One last important term to remember when choosing between peak and average sensors is video bandwidth. The burst average power, PBAvg, simply is the average power from within just the burst. For instance, in the pulse signal example used in the diagram, the burst average power can be determined, as long as you know the duty cycle of your signal.

On a test instrument, it would look like a reproduction of the waveform. So, if for example, your laser is 10 kW, and it pulses for 1 ns at 1 kHz … Crest factor is a parameter of a waveform, such as alternating current or sound, showing the ratio of peak values to the effective value. A common misconception is that the video bandwidth must always match the modulation frequency in order to make an accurate power measurement. Can you take a peek?”  And the sensor responds, “No sorry, I’m only an average power sensor.” Ba-dum-ching! The full derivation requires a little extra work because of the use of the root-mean-square value of a sinewave, based on its peak voltage value.
Crest factor 1 indicates no peaks, such as direct current or a square wave.Higher crest factors indicate peaks, for example sound waves tend to have high crest factors.