Quadrature Sampling for Phased Array Application
Receiver beam-forming in ultrasonic phased array systems typically demands very wide-band delay systems, having wide dynamic range and often complicated electronics. Sampled approaches to these delay lines generally employ sampling rates at least twice the highest frequency component in the returned RF signal. However, since the RF is bandlimited about some center frequency, by sampling in quadrature with respect to this center frequency the actual sampling rate may be substantially lowered. This produces two channels of information — the in-phase or “real” component, and the quadrature or “imaginary” component. This “complex video” from each array element may be delayed and added to that from the other elements to provide receiver focusing. In addition to lowering the sampling rate, this technique retains all phase information for Doppler processing as well.
KeywordsDelay Line Phase Array Video Display Quadrature Sampling Complex Video
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