Boonton 4240 RF Power Meter - Manual (Page 112)

Boonton 4240 Series RF Power Meter
Frequenc
capaci
cannot
table f
Misma
nding on the
mismat
minim
Signal
calibrat
nal and second harmonic
combin
insigni
egion (Region C, Figure 6-3), the detector responds to the vector sum of the signal and
harmo mplitude a between the harmonics and the fundamental,
measu ntly degrad even-order harmonics can be reduced by using
balanc er sensor. Thi o the peak-to-peak amplitude of the signal, which
remains constant f e relationship between ven-order harmonics. Unfortunately, for odd-order
harmo cs, the peak-to-peak signal amplitude is sensitive to phasing, and balanced detectors provide no harmonic error
improvement.
Noise.
out. Balanced
detecto sensors i prove t ignal-to-noise ratio by 3 dB, because the signal is twice as large.
6.1.3
The 42
interna
•
• Digital Signal Processor provides fast processing for near real-time measurements.
h creates a unique calibration table for each sensor.
y Response. The carrier frequency response of a diode detector is determined mostly by the diode junction
tance and the device lead inductances. Accordingly, the frequency response will vary from detector to detector and
be compensated readily. Power measurements must be corrected by constructing a frequency response calibration
or each detector.
tch. Sensor impedance matching errors can contribute significantly to measurement uncertainty, depe
ch between the device under test (DUT) and the sensor input. This error cannot be easily calibrated out, but can be
ized by employing an optimum matching circuit at the sensor input.
Harmonics. Measurement errors resulting from harmonics of the carrier frequency are level-dependent and cannot be
ed out. In the square-law region of the detector response (Region A, Figure 6-3), the sig
e on a root mean square basis. The effects of harmonics on measurement accuracy in this region are relatively
ficant. However, in the linear r
nics. Depending on the relative a nd phase relationships
fica e ors caused by rement accuracy may be signi d. Err
diode d he pow ed etectors for t s design responds t
or any phas fundamental and e
ni
For low-level signals, detector noise contributes to measurement uncertainty and cannot be calibrated
r m he s
4240 Series Features
40 Series design incorporates several significant features to reduce measurement error, simplify operation, and speed
l processing. These features include:
Balanced diode sensors enhance error performance by increasing signal-to-noise and suppressing even-
order signal harmonics.
• Smart Sensors (sensor-mounted EEPROM) store sensor frequency calibration eliminating operator entry.
• A built-in programmable calibrator whic
Application Notes
6-4