Abstract: Signals of interest in magnetic resonance imaging (MRI) systems comprise narrowband, circularly polarized (CP) radio-frequency magnetic fields from rotating atomic nuclei. Background “body noise” may comprise broadband, linearly polarized (LP) magnetic fields from thermally-activated eddy currents, and may exceed the signal in a band of interest, limiting the imaging resolution and requiring excessive averaging times. Noise may be selectively detected and substantially suppressed, while enhancing the signal of interest, using appropriate digital time-domain algorithms. At least two quadrature receiving antennas may be employed to distinguish and separate the LP noise from the CP signal. At least one broadband receiver may be used to identify and localize fast noise sources and to digitally filter the representation of their radio-frequency magnetic fields in the signal.

Abstract: A broadband multibit digital radio-frequency (RF) signal is synthesized digitally. to convert the digital signal to a high-power analog signal for RF transmission. Each bit (or cluster of bits) of the digital signal is first separately amplified using a fast switching amplifier with a controlled dc power supply voltage. The DC voltages are weighted to match the significance of the bits, and controlled by a set of calibrated DC reference sources to maintain high precision. The amplified digital signals from the various bits are then combined and passed through an appropriate analog filter to generate the RF signal to be transmitted. Such a signal can exhibit broad bandwidth, high dynamic range, excellent linearity, and low noise. Preferred embodiments of this system can incorporate superconducting electronic elements. For ultimate precision, a set of primary or secondary DC voltage standards can be used to regulate the switching amplifier supply voltages.

Abstract: A broadband multibit digital radio-frequency (RF) signal is synthesized digitally. to convert the digital signal to a high-power analog signal for RF transmission. Each bit (or cluster of bits) of the digital signal is first separately amplified using a fast switching amplifier with a controlled dc power supply voltage. The DC voltages are weighted to match the significance of the bits, and controlled by a set of calibrated DC reference sources to maintain high precision. The amplified digital signals from the various bits are then combined and passed through an appropriate analog filter to generate the RF signal to be transmitted. Such a signal can exhibit broad bandwidth, high dynamic range, excellent linearity, and low noise. Preferred embodiments of this system can incorporate superconducting electronic elements. For ultimate precision, a set of primary or secondary DC voltage standards can be used to regulate the switching amplifier supply voltages.

Abstract: A circuit for converting an n-bit number to a serial stream of single-bit pulses includes circuitry for generating n different sets of pulses; each set of pulses corresponding to a bit of the n-bit binary number; the number of pulses in a set of pulses corresponding to a bit “j” being equal to 2(j−1) pulses, where “j” is an integer which varies from one (1) for the LSB to n for the MSB. The circuit also includes n switches each switch having an input port, an output port and a control port. Each different bit is applied to the control port of a switch and the set of pulses corresponding to the bit is applied to the control port of that switch. The output ports of the n switches are coupled to a common point for combining the signals at the output ports and producing a serial stream of single-bit pulses at the common point which is equivalent to the n-bit binary number.

Abstract: A circuit for converting an n-bit number to a serial stream of single-bit pulses includes circuitry for generating n different sets of pulses; each set of pulses corresponding to a bit of the n-bit binary number; the number of pulses in a set of pulses corresponding to a bit “j” being equal to 2(j−1) pulses, where “j” is an integer which varies from one (1) for the LSB to n for the MSB. The circuit also includes n switches each switch having an input port, an output port and a control port. Each different bit is applied to the control port of a switch and the set of pulses corresponding to the bit is applied to the control port of that switch. The output ports of the n switches are coupled to a common point for combining the signals at the output ports and producing a serial stream of single-bit pulses at the common point which is equivalent to the n-bit binary number.

Abstract: A coated article, for example an architectural transparency, including a vehicular transparency, or a reflecting article, as a decorative article. The article has a substrate, e.g., a substantially transparent or substantially opaque substrate. The substrate has an optical coating on it, that is a coating having a thin film of an oxide of a transition metal, the thin film having a thickness corresponding to a constructively interfering function of a wavelength of interest. The optical coating, having a thin film of a transition metal, enhances the reflectivity of some wavelengths of the visible portion of the electromagnetic spectrum and the reflectivity of other wavelengths of the visible portion of the electromagnetic spectrum.