Squid control apparatus with non-cryogenic flux-locked loop disposed in close proximity to the squid
First Claim
1. SQUID control apparatus, for use with a SQUID probe having a voltage output, comprising:
- a head unit having electrical conductors to receive said voltage output of said probe, said head unit having, in conjunction with said probe, a non-cryogenic flux-locked loop having an analog output indicative of the magnetic flux applied externally to said probe;
a base unit having means for converting said analog output to a digital signal; and
cable means for carrying said analog output from said head unit to said base unit, said cable means distancing said base unit from said head unit.
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Accused Products
Abstract
SQUID control apparatus for controlling multiple SQUID probes includes a plurality of head units each corresponding to a respective SQUID probe, each of the head units including a non-cryogenic modulated flux-locked loop feedback circuit operating at a respective modulation frequency. The apparatus also includes a base unit coupled to all of the head units, the base unit providing control signals to control the multiple head units. Means are also provided, such as through the use of a daisy chain topology, for synchronizing the modulation frequency of all of the modulated flux-locked loop feedback circuits. The head units may also contain a phase shifter coupled to phase shift the modulation frequency oscillator signal for provision to the local oscillator input of a demodulator, and the phase shifter may include a shifting filter for filtering the oscillator signal to reduce all frequency components except a fundamental frequency component, and for phase shifting the fundamental frequency component by a desired amount, and shaping means for shaping the filtered and shifted signal into a square wave.
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Citations
26 Claims
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1. SQUID control apparatus, for use with a SQUID probe having a voltage output, comprising:
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a head unit having electrical conductors to receive said voltage output of said probe, said head unit having, in conjunction with said probe, a non-cryogenic flux-locked loop having an analog output indicative of the magnetic flux applied externally to said probe; a base unit having means for converting said analog output to a digital signal; and cable means for carrying said analog output from said head unit to said base unit, said cable means distancing said base unit from said head unit. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8)
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9. A non-cryogenic head unit for a SQUID control system, for use with a base unit and with a SQUID probe, said base unit providing remote control signals for said head unit, said SQUID probe having a SQUID, a feedback coil and leads for applying a bias current to said SQUID, for providing a voltage output from said SQUID, and for applying a feedback current to said feedback coil, said head unit comprising:
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a flux-locked loop feedback circuit having an input lead for receiving said voltage output from said SQUID, a feedback output lead for providing said feedback current to said feedback coil of said probe, and an analog output indicating the magnitude of said feedback current; means for receiving said remote control signals from said base unit and applying them to said head unit; and means for disposing said head unit in close proximity to said probe relative to said base unit. - View Dependent Claims (10, 11, 12, 13, 14, 15, 16, 17)
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18. A non-cryogenic head unit for a SQUID control system, for use with a base unit and with a SQUID probe, said SQUID probe having a SQUID, a feedback coil and leads for applying a bias current to said SQUID, for providing a voltage output from said SQUID, for applying a feedback current to said feedback coil, and for receiving a DC offset current for application as a DC offset flux to said SQUID, said head unit comprising:
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an internal oscillator having an output; a lead for receiving an external oscillator signal; means for selecting said output of said internal oscillator or said external oscillator signal, to provide a selected oscillator signal; a phase shifter coupled to phase shift said selected oscillator signal to provide a phase shifted oscillator signal; a flux-locked loop feedback circuit having an input lead for receiving said voltage output from said SQUID, a feedback output lead for providing said feedback current to said feedback coil of said probe, and an analog output indicating the magnitude of said feedback current, said flux-locked loop feedback circuit further having a range selection input port; means for applying said selected oscillator signal to said probe to modulate the flux applied to said SQUID, said flux-locked loop feedback circuit further having a demodulator for demodulating said voltage output from said SQUID in response to an oscillator input coupled to receive said phase shifted oscillator signal; and means for receiving a range selection signal from said base unit and applying said range selection signal to said range selection input port of said flux-locked loop feedback circuit, said head unit further comprising means for receiving a bias determination signal from said base unit; a bias output lead for providing said bias current to said probe; and means for applying said bias current to said bias output lead in response to said bias determination signal, said head unit further comprising means for receiving a DC offset determination signal from said base unit; means for applying said DC offset current in response to said DC offset determination signal to said lead of said SQUID probe for receiving a DC offset current; and means for disposing said head unit in close proximity to said probe relative to said base unit.
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19. SQUID control apparatus, for use with a plurality of SQUID probes, comprising:
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a plurality of head units, including a master head unit, each of said head units corresponding to a respective one of said SQUID probes, each of said head units including a non-cryogenic modulated flux-locked loop feedback circuit operating at a respective modulation frequency; and a base unit coupled to all of said head units, said base unit providing control signals for controlling said head units, wherein said master head unit generates a modulation frequency signal, and wherein the modulation frequency of all of said modulated flux-locked loop feedback circuits is synchronized in response to said modulation frequency signal.
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20. SQUID control apparatus, for use with a plurality of SQUID probes, comprising:
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a plurality of head units, including a master head unit, each of said head units corresponding to a respective one of said SQUID probes, each of said head units including a non-cryogenic modulated flux-locked loop feedback circuit operating at a respective modulation frequency, wherein said master head unit generates a modulation frequency signal; a base unit coupled to all of said head units, said base unit providing control signals for controlling said head units; and synchronizing means for synchronizing the modulation frequency of all of said modulated flux-locked loop feedback circuits in response to said modulation frequency signal. - View Dependent Claims (21, 22)
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23. SQUID control apparatus, for use with a plurality of SQUID probes, comprising:
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a plurality of head units, including a master head unit, each of said head units corresponding to a respective one of said SQUID probes, each of said head units including a non-cryogenic modulated flux-locked loop feedback circuit operating at a respective modulation frequency, wherein said master head unit generates a modulation frequency signal; a base unit coupled to all of said head units, said base unit providing control signals for controlling said head units; and synchronizing means for synchronizing the modulation frequency of all of said modulated flux-locked loop feedback circuits in response to said modulation frequency signal, wherein said synchronizing means comprises; a master modulation oscillator having an output coupled to all of said head units, deriving means in each of said head units for deriving the modulation frequency of the respective head unit from said output of said master modulation oscillator, wherein said master modulation oscillator is disposed in said base unit, said base unit further comprising means for transmitting said control signals to said head units in a form including the transmission of a digital bit stream carrying at least some of said control signals and operating at a frequency responsive to said output of said master modulation oscillator, said deriving means in each of said head units including means for deriving the modulation frequency of said respective head unit from said digital bit stream.
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24. SQUID control apparatus, for use with a plurality of SQUID probes, comprising a master head unit corresponding to one of said probes and a slave head unit corresponding to each of the others of said probes, said master head unit comprising:
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a master modulated flux-locked loop feedback circuit operating at a master modulation frequency; a master modulation oscillator coupled to provide said master modulation frequency to said master modulated flux-locked loop feedback circuit; and a slave output coupled to carry said master modulation frequency from said master modulation oscillator, each of said slave head units comprising; a slave modulated flux-locked loop feedback circuit operating at a slave modulation frequency; and a master input coupled to provide said slave modulation frequency to said slave modulated flux-locked loop feedback circuit, said SQUID control apparatus further comprising a cable network coupling said slave output of said master head unit to said master input of a first one of said slave head units so that said master head unit controls said slave head units. - View Dependent Claims (25, 26)
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Specification