| Q | quality factor | A measure of the loss properties of a resonant structure. |
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| QAM | Quadrature amplitude modulation | A form of RF modulation in communications systems |
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| QFN | quad flat-pack no-lead | A type of package for surface mount. Because it has no leads it is nearly impossible to hand solder. "Quad" refers to the geometry where connections are made on all four sides of the package; a "DFN" (dual) has leads only on two opposite sides. |
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| QPSK | quadrature phase shift keying | Also called 4-QAM, this is a method of modulating 2 bits of data at a time to indicate one of four possible states (or symbols), thus doubling the amount of data that can be transmitted over a given bandwidth. |
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