Amplitude and phase error normalization of subcarrier generator

DETAILED DESCRIPTION A subcarrier generator under a preferred form of the present invention includes a bandpass finite impulse response (FIR) filter determined by a set of FIR coefficients.
Under the present invention, a first set of FIR coefficients corresponds to an ideal subcarrier signal shape and center frequency.
The subcarrier generator operates initially with this first set of FIR coefficients to produce a subcarrier signal.
A calibration device monitors the subcarrier signal and calculates a second set of FIR coefficients to de-convolve the output of the analog filter and other frequency-dependent amplitude and phase distortion devices.
This corrects for distortion introduced in the output stage of the subcarrier signal generator by predistorting the output of the bandpass FIR filter as a function of the frequency-dependent characteristics of the analog output stage of the subcarrier generator.
As a result, the subcarrier signal produced more closely matches the desired shape and center frequency.
Calibration under the present invention may be conducted at least once at the time of subcarrier generator device manufacture or installation, and subsequently, on an intermittent or demand basis, to the extent that frequency-dependent characteristics of the subcarrier generator output stage devices change.
The subject matter of the present invention is particularly pointed out and distinctly claimed in the concluding portion of this specification.
However, both the organization and method of operation of the invention, together with further advantages and objects thereof, may best be understood by reference to the following description taken with the accompanying drawings wherein like reference characters refer to like elements.