What is a power sensor?
Answer:
*Power sensor is used :
-to measure the peak and average power of CDMA signals.
-to measure peak and average power of wide band, third-genration CDMA signals over an 80 dB range.
- measure the average power of amplitude modulated, burst modulated and other complex modulated signals -- such as TDMA signals -- at bandwidths up to 40kHz.
-measure the instantaneous peak power level of a pulse modulated signal. Use the "sample delay" function to set the desired measurement point on the waveform. And an external scope can be used to view the profile and see the exact measurement point on the pulse.
-measure CW power from 10 MHz to 40GHz at more than 1,750 readings per second over GPIB.
[Thermal power Sensor :
In an thermo sensor the incoming RF signal is absorbed in a small dummy load. A standard 50 Ohms chip resistor (e.g. 0603) can be used up to 5-10GHz with very good results. Due to the power dissipation from the RF signal, the resistor warms up. The change in temperature can be used to determine the power of the RF signal. If we glue a NTC (a resistor that changes its resistance depending on its temperature) on the dummy load and include it in an measurement bridge, we get a voltage difference that is equivalent to the input power. A second NTC of the same kind in the bridge can be used, to eliminate the ambient temperature influence.
The nice thing about this principle is that it is basically independent of the frequency of the input signal. The resistor does not care if it is warmed up by a noble 10GHz beacon signal or by a cheap DC signal that can also be measured by a standard multimeter. Therefore every amateur can calibrate his homemade thermal sensor by applying different DC voltages to the input and writing down the resulting bridge voltage. Whenever you see the same DC output voltage as with a certain DC input level, you know that the power of your measured signal is the same, independent on the frequency or waveform of your signal. ]
in the world of communication electronics, we often need to know the power level of an RF signal. A special device that measures accurately the power level of an RF signal is a power sensor. Usually, this is done by converting to heat, and then measuring temperature rise, which is proportional to power, assuming that thermal resistance is known.
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