When an RF burst is applied to the input of a demodulating log amp, the output will be a voltage pulse.
The type of jitter shown previously is typically the result of improper input interfacing to the demodulating log amp.
Note especially that the product of the sin(2[pi][f.sub.1]t) demodulating
carrier with the leading cos(2[pi][f.sub.1]t) interferer term in the right hand side of Equation 4 produces identically zero output from the zonal low pass filter that routinely completes the demodulation process.
The error vector is the vector difference between the measured and reference vectors, and the reference position is determined from a reference signal that is synthesized by demodulating
the data bits from the received signal and remodulating these bits "perfectly."
The instrument is also capable of demodulating
both AM and FM signals for a wide range of communications applications.
Figure 4 shows the receiver demodulating
the input signal into I and Q components.
Several methods for generating and demodulating
Walsh functions are described.
In essence, the demodulating logarithmic amplifier is an RF-to-DC converter.
The architecture is similar to a classic demodulating logarithmic amplifier but adds some flexibility at the output to allow for operation as a controller.
In conjunction with the optional vector signal analyzer, the instruments are capable of demodulating
and measuring digitally modulated signals.
Therefore, frequency can only be measured by demodulating
the data and mathematically calculating the signal trajectory.
For example, assume that one particular RF pulse has a phase that leads the phase of the reference oscillator (RO) by 35[degrees], then 35[degrees] are added to the phase of the demodulating
oscillator before the reflected pulse returns.