RF transmission circuit, complex digital synthesizer, and MRI apparatus
First Claim
Patent Images
1. An RF transmission circuit comprising:
- a system interface which receives control data from outside;
a complex digital synthesizer which releases a reference carrier frequency signal in accordance with the command from said system interface;
an RF envelope mixer which combines the reference carrier frequency signal and an RF envelope waveform signal and releases a resulting reference RF pulse signal in the complex form;
a digital frequency up-converter which up-converts the carrier frequency of the reference RF pulse signal to a resonant frequency necessary at an intended static magnetic field strength and converts the resulting signal into an analog RF pulse signal; and
an analog rousing circuit which filters out alias harmonics emerging in the analog RF pulse signal and adjusts the amplitude of the resulting signal.
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Abstract
An RF transmission circuit, complex digital synthesizer and MRI apparatus are intended to enhance the stability of signal quantity and reduce the cost, wherein a complex digital synthesizer generates reference carrier frequency signal data directly in the digital domain, RF envelope mixers combine the resulting data and RF envelope signal data in the digital domain, and a digital frequency up-converter up-converts the resulting signal data in the digital domain and converts into an analog RF pulse signal.
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Citations
14 Claims
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1. An RF transmission circuit comprising:
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a system interface which receives control data from outside;
a complex digital synthesizer which releases a reference carrier frequency signal in accordance with the command from said system interface;
an RF envelope mixer which combines the reference carrier frequency signal and an RF envelope waveform signal and releases a resulting reference RF pulse signal in the complex form;
a digital frequency up-converter which up-converts the carrier frequency of the reference RF pulse signal to a resonant frequency necessary at an intended static magnetic field strength and converts the resulting signal into an analog RF pulse signal; and
an analog rousing circuit which filters out alias harmonics emerging in the analog RF pulse signal and adjusts the amplitude of the resulting signal. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13)
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14. A complex digital synthesizer comprising:
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a center frequency accumulator for calculating by summing cumulatively data which determines the center frequency of a reference carrier frequency signal;
an offset frequency accumulator for calculating by summing cumulatively data which offsets the center frequency of the actual reference carrier frequency signal from the said center frequency;
an initial phase register for holding data which determines the initial phase of the reference carrier frequency with respect to an RF envelope waveform;
an adder which adds the above-mentioned data;
a cosine lookup table which has a record of cosine waveform data, and reads out cosine waveform data by being addressed by data resulting from the summation by said adder and releases as inphase component data; and
a sine lookup table which has a record of sine waveform data, and reads out sine waveform data by being addressed by data resulting from the summation by said adder and releases as quadrature component data.
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Specification