Boots – shoes – and leggings
Patent
1988-10-31
1990-03-20
Heyman, John S.
Boots, shoes, and leggings
328145, 36471501, G06F 906, G06F 7544, G01R 2500
Patent
active
049104659
ABSTRACT:
This invention relates to a circuit for detecting the phase of an AC signal of frequency f. The signal is applied to two mixers one of which mixes the AC signal with a first signal of frequency f to generate a signal I and the other of which mixes the AC signal with a second signal of frequency f which is 90 degrees out of phase with the first signal to generate a signal Q. The I and Q signals are digitized and the log of the absolute value of each of the digitized signals is generated. The log generating function may for example be performed with a table-look-up memory. One log value, for example log I, is substracted from the other log value and the Arctan of the antilog of this difference is then generated. The Arctan function may also be generated using a table-look-up memory. The resulting Arctan value is indicative of the phase of the AC signal. The quadrant for the AC signal is determined by saving the sign of the digitized I and Q signals before taking the logrhythm of the absolute values of these signals and applying these signs along with the Arctan signal to a qradrant circuit. For a preferred embodiment, the phase detector is utilized as a part of a color flow Doppler system, the AC signal being the output from an ultrasonic Doppler transducer system and the determined phase being utilized to control the Doppler color flow display.
REFERENCES:
patent: 4373191 (1983-02-01), Fette et al.
patent: 4568978 (1986-02-01), Cosh
patent: 4680721 (1987-07-01), Pluddemann
patent: 4710892 (1987-12-01), Fling
patent: 4715000 (1987-12-01), Premerlani
patent: 4721904 (1988-01-01), Ozaki et al.
patent: 4745309 (1988-05-01), Waller
patent: 4807171 (1989-02-01), Gale
Hewlett--Packard Company
Heyman John S.
Perillo Frank R.
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