RF Power Measurements | Average, Pulse, Peak Envelope Power PEP | Electronics Notes
The duty cycle is used to calculate both the peak power and average power of a. Duty Cycle. average power. pulse power. pulse width. pulse repetition time. Note that power meters often provide crest factor or peak-to-average has a strong linear relationship to the square of the applied RF voltage. If you always wanted to learn how to measure the real pulse temporal shape of your laser – and use it to calculate the peak power – this is the.
RF Power Measurements: average, pulse & peak envelope power, PEP
Peak and Average Measurements of a Pulse Modulated Signal The first term, Instantaneous power, P tis the actual power of the signal at any given time.
On a test instrument, it would look like a reproduction of the waveform. Capturing instantaneous power requires instrumentation that can react fast enough to capture the rapid changes in the signal. Envelope power, Pe tis the amplitude change due to modulation, or sometimes distortion, and is another measurement as a function of time. Envelope power is not a re-creation of the waveform itself, but a representation of the average power over the sensor aperture interval at any point in time see Figure 2 for another example of the relationship between envelope power and instantaneous power.
The peak envelope power, PEP, is the highest single power measurement from within the envelope power readings. Note that power meters often provide crest factor or peak-to-average power ratios PAPR.
In this case, the peak power is actually PEP, rather than instantaneous, peak power.
- RF pulse power or peak power
- RF average power
More on video bandwidth and crest factor later, though. The burst average power, PBAvg, simply is the average power from within just the burst. Another Example of Instantaneous vs. Average Powers The last value in our list is the average power, Pavg represented by the purple line in Figure 1which is the average power taken over a specified period of time.
In our example, it is during the period from the beginning of one burst to the next also known as the pulse repetition interval, or PRI. These particular diode-based sensors are sometimes referred to as true-RMS sensors, because they are designed to keep the measured signal within the square-law region of the diode — where the DC output of the sensor circuit has a strong linear relationship to the square of the applied RF voltage.
This allows them to accurately measure the average power of most signals, including modulated, multi-tone, or pulsed signals. For unmodulated signals i. Note that, although the average sensor cannot measure the peak power of the modulation, in some cases you can still use it to determine certain characteristics of the burst. 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.
As the pulse is likely to include some overshoot and ringing, the most accurate term for the power is the pulse power.
Peak power would imply that the value of any overshoot would need to be taken, whereas the actual power measurement required is that of the overall pulse. Called peak envelope power, PEP, it is used to measure the power of some varying waveforms.
There are many instances where a power measurement that takes the peak of the envelope is needed. Many digitally modulated waveforms may require this, and also transmissions such as AM and Single Sideband may also need this type of RF power measurement.
The envelope power is measured by making the averaging time greater than the period of the modulating waveform, i. This means that the averaging time of the RF power measurement must fall within a window: It must be large when compared to the period of the highest modulation frequency.
Radar Basics - Peak- and average power
It must be small compared to the period of the carrier waveform 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. It is the most convenient to make, and often expressed the value that needs to be known.
However pulse power, sometimes referred to as peak power, and also the peak envelope power also need to be known on many occasions. However the techniques and equipment needed to make peak envelope power and pulse power are different to those needed for average power. Accordingly it is necessary to understand the differences between the different types of RF power measurement and the equipment needed.