US5072183A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Rf generator for magnetic resonance imaging apparatus
Assignee: US Philips Corp
•
Filing: 1990-09-26
•
Granted: 1991-12-10
•
Expires: 2010-09-26
Abstract
Abstract An rf generator for magnetic resonance imaging apparatus including a modulator in which a carrier is modulated with an envelope signal, and a transmitter stage which is connected subsequent to the modulator generator in which the implementation of the modulating signal enables the expenditure for the transmitter stage be substantially reduced in that the modulator comprises a first modulator section in which the envelope signal is converted into a series of equally long digital pulses whose density corresponds to the amplitude of the envelope signal, in that k different kinds of pulses are provided, in that during each pulse of a given kind the carrier is always switched on with a given phase position which deviates from the phase positions of the carrier which are associated with the pulses of the other kinds by 360°/k or an integer multiple thereof, and in that the resultant pulse-wise switched, preferably square-wave carrier acts as a switching signal for the transmitter stage.
Inventors
- 👤 Graeme McKinnon
- 👤 Roland Proksa
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-07 14:13
CPC Classifications
G; G01; G01R; G01R33/00; G01R33/20; G01R33/28; G01R33/32; G01R33/36; G01R33/3614
Claims Analysis
Total Claims: 20
Claim 1
Independent Claim
121 words
A rf generator for magnetic resonance tomography apparatus, comprising a modulator in which a carrier is modulated with an amplitude of an envelope signal, and also comprising a transmitter stage which is connected subsequent to the modulator, characterized in that the modulator (9) comprises a first modulator section (91) in which the envelope signal (e) is converted into a series of equally long digital pulses (p) having values and density corresponding to the amplitude of the envelope signal, in that the first modulator section controls a second modulator section (92) so that the transmitter stage (8) operating in the switching mode supplies carrier oscillations only during the pulses, said carrier oscillations having a phase determined by the value of each pulse.
Claim 2
Dependent Claim
121 words
A rf generator for magnetic resonance tomography apparatus, comprising a modulator in which a carrier is modulated with an amplitude of an envelope signal, and also comprising a transmitter stage which is connected subsequent to the modulator, characterized in that the modulator (9) comprises a first modulator section (91) in which the envelope signal (e) is converted into a series of equally long digital pulses (p) having values and density corresponding to the amplitude of the envelope signal, in that the first modulator section controls a second modulator section (92) so that the transmitter stage (8) operating in the switching mode supplies carrier oscillations only during the pulses, said carrier oscillations having a phase determined by the value of each pulse.
Claim 3
Dependent Claim
105 words
An rf generator as claimed in claim 1, characterized in that the pulses have only two different values, one of which is assigned to a positive polarity while the other is assigned to a negative polarity of the envelope signal, in that the carrier is generated with a first phase (c) and a second phase (c') which has been shifted through 180° with respect to the first phase, and in that the transmitter stage produces the carrier having the first phase for one of said different values of a pulse, and produces the carrier with the second phase for the other of said different values.
Claim 4
Dependent Claim
38 words
An rf generator as claimed in claim 1, characterized in that during a pulse the carrier performs exactly one or more complete oscillations, a spacing between two successive pulses amounting to mT where m is a positive integer.
Claim 5
Dependent Claim
21 words
An rf generator as claimed in claim 1, characterized in that the transmitter stage comprises a pushpull switching stage (81, 82).
Claim 6
Dependent Claim
37 words
An rf generator as claimed in claim 1, characterized in that it comprises a filter (83) which is connected to the output of the transmitter stage in order to reduce the higher harmonics of the carrier frequency.
Claim 7
Dependent Claim
36 words
An rf generator as claimed in claim 5, characterized in that the transmitter stage comprises an output transformer (83) which is proportioned so that it at least partly suppresses the higher harmonics of the carrier frequency.
Claim 8
Dependent Claim
75 words
An rf generator as claimed in claim 1, characterized in that the transmitter stage is connected to a non-stabilised supply voltage (U), in that there is provided an analog-to-digital converter which digitises a signal which is proportional to the supply voltage, and in that the pulse density is controlled in dependence on the output signal of the analog-to-digital converter so that the pulse density varies in the opposite sense with respect to the supply voltage.
Claim 9
Dependent Claim
68 words
An rf generator as claimed in claim 1, characterized in that the first modulator section comprises an accumulator circuit for forming a control signal (51) which depends on the difference (F) between the pulses and the envelope signal, the control signal being applied to a logic circuit (912) which generates a pulse having a positive or a negative polarity so that the integral remains within a given range.
Claim 10
Dependent Claim
38 words
An rf generator as claimed in claim 2, characterized in that during a pulse the carrier performs exactly one or more complete oscillations, a spacing between two successive pulses amounting to mT wherein m is a positive integer.
Claim 11
Dependent Claim
21 words
An rf generator as claimed in claim 2, characterized in that the transmitter stage comprises a pushpull switching stage (81, 82).
Claim 12
Dependent Claim
21 words
An rf generator as claimed in claim 9, characterized in that the transmitter stage comprises a pushpull switching stage (81, 82).
Claim 13
Dependent Claim
37 words
An rf generator as claimed in claim 2, characterized in that it comprises a filter (83) which is connected to the output of the transmitter stage in order to reduce the higher harmonics of the carrier frequency.
Claim 14
Dependent Claim
37 words
An rf generator as claimed in claim 11, characterized in that it comprises a filter (83) which is connected to the output of the transmitter stage in order to reduce the higher harmonics of the carrier frequency.
Claim 15
Dependent Claim
36 words
An rf generator as claimed in claim 12, characterized in that the transmitter stage comprises an output transmitter (83) which is proportioned so that it at least partly suppresses the higher harmonics of the carrier frequency.
Claim 16
Dependent Claim
36 words
An rf generator as claimed in claim 13, characterized in that the transmitter stage comprises an output transmitter (83) which is proportioned so that it at least partly suppresses the higher harmonics of the carrier frequency.
Claim 17
Dependent Claim
75 words
An rf generator as claimed in claim 2, characterized in that the transmitter stage is connected to a non-stabilized supply voltage (U), in that there is provided an analog-to-digital converter which digitises a signal which is proportional to the supply voltage, and in that the pulse density is controlled in dependence on the output signal of the analog-to-digital converter so that the pulse density varies in the opposite sense with respect to the supply voltage.
Claim 18
Dependent Claim
75 words
An rf generator as claimed in claim 15, characterized in that the transmitter stage is connected to a non-stabilized supply voltage (U), in that there is provided an analog-to-digital converter which digitises a signal which is proportional to the supply voltage, and in that the pulse density is controlled in dependence on the output signal of the analog-to-digital converter so that the pulse density varies in the opposite sense with respect to the supply voltage.
Claim 19
Dependent Claim
68 words
An rf generator as claimed in claim 2, characterized in that the first modulator section comprises an accumulator circuit for forming a control signal (51) which depends on the difference (F) between the pulses and the envelope signal, the control signal being applied to a logic circuit (912) which generators a pulse having a positive or a negative polarity so that the integral remains within a given range.
Claim 20
Dependent Claim
68 words
An rf generator as claimed in claim 17, characterized in that the first modulator section comprises an accumulator circuit for forming a control signal (51) which depends on the difference (F) between the pulses and the envelope signal, the control signal being applied to a logic circuit (912) which generators a pulse having a positive or a negative polarity so that the integral remains within a given range.
References Cited (Backward Citations)
US3581191A
Cited
US3681680A
Cited
US3909705A
Cited
US3786341A
Cited
US3968424A
Cited
US4327327A
Cited
US4656424A
Cited
US4682106A
Cited
US4694254A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1994-12-09 | 1995-06-10 | 1995-12-10 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1998-12-09 | 1999-06-10 | 1999-12-10 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2002-12-09 | 2003-06-10 | 2003-12-10 | $7700.00 | Window Closed / Lapsed |