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PubMed · 5012035

An electrometer amplifier with low input capacitance and large input dynamic range.

N G Holmer·K Lindström
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N G Holmer, K Lindström. 1972. An electrometer amplifier with low input capacitance and large input dynamic range.. https://doi.org/10.1109/tbme.1972.324061

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PURPOSE: To improve preamplifier decoupling in a quadrature phased-array coil using a new quadrature combiner configuration. MATERIALS AND METHODS: A commercial six-element quadrature cervical-thoracic-lumbar (CTL) coil was used on a 1.5 T GE Signa Lx Scanner. The new combiner configuration is designed based on the fact that when one compares the amount of flux linkage of two loops with butterfly elements separated by the same distance, the loop elements have much higher coupling than the butterfly elements. RESULTS: The results are demonstrated using an imaging-based element coupling measurement method. The new quadrature combiner configuration has introduced an approximately -8dB improvement in preamplifier decoupling. CONCLUSION: One-dimensional quadrature phased arrays can be built even if the preamplifier is not integrated in the coil. If the combiner is placed between the coil and the preamplifiers, the butterflies should be on the high impedance side of the quadrature combiner. The loops should see the low input impedance of the preamplifiers.

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