Boonton 4240 RF Power Meter Instrukcja Użytkownika Pobierz pdf (Strona 59)

Boonton 4240 Series RF Power Meter

Diode 20 dBm (-10 dBm and 0 dBm for attenuated models 51015 and

1033). This response characteristic is obtained because the sensors are dual diode types, and diodes respond in square-law

not an approximation, but rather an inherent effect. This effect results from the fact

s switches, but behave as signal dependent resistors instead. Even with no signal input,

e diodes have a finite conductance, and this conductance is modulated on a cycle by cycle basis to give a net DC offset

ponse can be seen in Figure 4-12, where a 100% amplitude modulated signal is shown to have virtually no

sensors are also RMS responding below about -

fashion at low and medium levels. This is

that the diodes do not turn on and off a

proportional to the power.

The square-law res

effect on the measured power at low levels. Of course, frequency modulated and phase modulated signals can be measured at

any level, since the envelope of these modulated signals is flat. Frequency shift keyed (FSK) and quadrature modulated

signals also have flat envelopes and can be measured at any power level.

Figure 4-1 Modulation (5102. Error Due to AM 13 Diode Sensor)

y -10 d detectors. The

odel 4 0 is so lculate the RF

pe. Ho ever, o RF si nals wi

ansition region from -20 dBm to -10 dBm.

the top

easured. The duty cycle in percent is set into the DUTY entry in the

HANNELS menu. For example, if the signal consists of pulses with a duty cycle of 25%, set DUTY to 25. This will add 6

B to the displayed power and turn on the "Pk" indicator following the units.

t higher power levels (above approximatel Bm for the 51013 sensor), the diodes operate as peakA

M 24 ftware calibrated to ca power based on a shaping transfer function (RF to DC) for each sensor

y measurements f e valid in this ty w nl o g th flat envelopes (CW, FM, PM, FSK, quadrature, etc.) ar

region and in the tr

r pulses where the duty cycle (on-time percentage) is known andA special provision is made for the case of rectangula

vel power of the pulse (pulse power) is to be mle

Operation

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Boonton 4240 RF Power Meter Instrukcja Użytkownika Strona 59