Rectification and smoothing are associated with which processing stage?

Rectification and smoothing are associated with which processing stage?

• A. Amplification
• B. Decompensation
• C. Compression
• D. Demodulation

Answer: (D)

Rectification and smoothing are used to pull out the envelope of the received RF signal, which is the essence of the demodulation stage. In ultrasound, the echoes arrive as a high-frequency carrier signal whose amplitude carries the image information. To form a usable image, this RF signal is first rectified to convert all negative parts to positive, then smoothed with a low-pass filter to remove the carrier frequency and leave a slowly varying envelope that reflects echo amplitude. This envelope is what is subsequently processed (often compressed) to produce the display grayscale. So rectification and smoothing serve envelope detection, a core part of demodulation.

Rectification and smoothing are used to pull out the envelope of the received RF signal, which is the essence of the demodulation stage. In ultrasound, the echoes arrive as a high-frequency carrier signal whose amplitude carries the image information. To form a usable image, this RF signal is first rectified to convert all negative parts to positive, then smoothed with a low-pass filter to remove the carrier frequency and leave a slowly varying envelope that reflects echo amplitude. This envelope is what is subsequently processed (often compressed) to produce the display grayscale. So rectification and smoothing serve envelope detection, a core part of demodulation.