Specifications

Description of the Beatnote Calibration Method
Beatnote Frequencies Less Than 1 kHz
To determine the Phase Detector Constant from a beatnote, the calibration
source is adjusted to create a beatnote between the two sources. For
beatnote frequencies less than 1 kHz the system uses the slope of the
beatnote waveform as it passes through the zero crossing as the Phase
Detector Constant (or sensitivity of the detector to variations in phase).
If slope of the beatnote waveform differs by less than 10% on two
consecutive zero crossings, as in a sine wave or a triangle wave, then
the system's ability to determine the Phase Detector Constant is very
good. The Phase Detector Constant is valid for variations in phase up
to 0.2 radians (the small angle criteria).
Beatnote Frequencies Greater than 1 kHz
Beatnotes greater than 1 kHz require that the system determine the Phase
Detector Constant by measuring the beatnote fundamental and its odd
harmonics. The odd harmonics of the beatnote are measured to determine
how much the beatnote departs from a sine wave. This measurement
corrects the measured amplitude of the beatnote to determine an accurate
Phase Detector Constant for non-sinusoidal beatnotes.
If the first odd harmonic is less than —30 dBc, the system assumes the
beatnote is a sine wave. The Phase Detector Constant is a function of the
amplitude of the fundamental (a sine wave's peak amplitude is equal to
the phase slope). If, however, the first odd harmonic of the beatnote is
greater in amplitude than —30 dBc but beyond the range of the analyzer
configured in the system, the system will incorrectly assume that the
beatnote is a sine wave. In this case, a small error in the Detector Constant
is introduced (maximum, worst case error is f^ 1 dB). For this reason, the
beatnote frequency should be less than one third of the full scale frequency
range of the system analyzer. (As an example, the HP 3561A has a
maximum frequency span of 100 kHz, therefore, a beatnote frequency
Calibr Process: $N w/o PLL 2-65