Abstract: Methods and apparatus for enhancing the clarity of and the diagnostic information in real-time B-mode and M-mode ultrasound displays including a beamformer for acquiring ultrasound receive signals for each ultrasound scan line of a two-dimensional image and processing the receive signals for each ultrasound scan line into detected and filtered video signals for storage in scan line acquisition memory with programmable dynamically variable non-linear filters for processing the video signals with continuously and automatically varying filter responses over a range of low and high pass responses followed by scan converting and display of the non-linearly processed video signals. The non-linear filters may process video signals in range along each ultrasound scan line or azimuthally along multiple ultrasound scan lines of a two-dimensional B-mode image.

Abstract: The jitter tracker of the present invention uses a decision-directed error signal as an input to a feedback loop. The error signal is filtered and coupled to a phase locked loop centered at the center of the jitter tracking frequency range, which in the preferred embodiment is 55 Hz. The frequency width and center track and lock frequencies are set by a loop filter. A second order loop is used to acquire the frequency and phase jitter within an acceptable range. Once within this range, a first order loop is used to lock the amplitude to the input signal. The amplitude and phase values are subtracted from the incoming signal so that a new error may be calculated. In the preferred embodiment, the jitter tracker of the present invention is implemented in a digital signal processor. The jitter tracker of the preferred embodiment of the present invention comprises two filter loops. The first loop is used to generate the magnitude of the jitter error. The second loop generates the phase of the jitter error.

Abstract: The present invention is a method and apparatus for implementing a two stage AGC circuit. In the preferred embodiment, the present invention is used as part of a receive channel in a modem. The first stage of the AGC is a "coarse" AGC and is used to track large signal transients of an input signal. The coarse AGC locks on to transient signals without excessive settling time. In operation, the coarse AGC acquires a new signal by using a nonlinear clipped feedback loop technique supported by a linearized feedback loop. The coarse AGC stage uses an error signal derived from the noncoherent power fluctuations of the incoming signal. The second stage of the AGC circuit is a "fine" AGC using a decision-directed coherent amplitude error signal and a quick linear feedback loop to correct for finer signal level fluctuations. The fine AGC has a high pass characteristic which decouples its response from that of the equalizer for stability reasons.

Abstract: The present invention is directed to a digital non-coherent pattern detection scheme in which spectral analysis of phase encoded signals is utilized to provide pattern recognition. The present invention is relatively insensitive to the power level of incoming signals. Since the power level is easily detected and determined, the present invention allows the various algorithms to operate quickly. Further, utilizing the magnitude samples of the incoming signal result in a pattern detection scheme that is independent of modulation technique. The present invention utilizes the concept of spectral analysis to determine spectral lines which are present in phase encoded signals. A phase encoded signal such as a DPSK or QAM having an implicit pattern contained therein, which results in unique spectral lines. By detecting the spectral lines in certain combinations, the phase encoded pattern being sent may be identified.