Barretter
C. Barretter Integration-Differentiation Pulse Power Meter
The basis of this technique is that any waveform may be integrated and the resulting shape differentiated to restore the original wave shape. A special barretter is used to integrate the input pulse of power, and the resulting wave shape is amplified and differentiated by an RC network. The resulting voltage pulse is thus proportional to the power envelope of the RF input pulse. The amplitude of the pulse is measured with a peak reading voltmeter calibrated in watt. A special calibration generator is included within commercial instruments as shown in Fig3. In calibrating these instrument, it is also necessary that the barretter sensitivity in terms of voltage output per mW of RF power input be known.
Sources of uncertainty in the baretter integration-differentiation technique include the calibration generator and the calibration factor or effective efficiency of the barretter mount. The effective efficiency of the mount can be determined using CW power. However, bridges employing audio substitution power should not be used because the time constant of the barrater is such that it will tend to follow the audio voltage. Manufacturers’claims for the uncertainty limit of peak pulse power measuring instruments employing the barretter integration-differentiation technique are 5 to 10 percent. Barretter mounts are available for and to 18 GHz in wave guide. Typically, the power range extends from 5 mW to 300 mW and the measurement are not sensitive to duty factor over a wide range of PRR (50 to 10000) and pulse duration (0.25 to 10 Us).
A new instrument based on this principle has recently been developed in the U.S.S.R.[5].