Exam B-IQFILT

Exam 6.0.3


The RF data is low-pass filtered in the base band after down mixing. The order of filter (number of taps) is proportional to IQ Window Factor (see here). The Cutoff Frequency is in percent of the sampling frequency/2.
 * IQ Window Factor
 * Cutoff Frequency

To account for the downshifting of the center frequency of the RF signal as a function of depth, the carrier frequency used in the IQ demodulation is not constant but is sliding. More accurately it changes linearly with depth. The frequency used at the top of the image (depth zero) is Top Frequency. The frequency used at the Bottom Frequency Depth is Bottom Frequency.
 * Top Frequency
 * Bottom Frequency
 * Bottom Frequency Depth

When doing PIH imaging, the carrier frequency is double the frequency of the transmitted pulses. Therefore another set of values are needed for harmonic imaging:
 * Top Frequency Base
 * Bottom Frequency Base
 * Bottom Frequency Depth Base