| 摘要 |
A communication device (100) includes mixers (104 and 108) which mix a local oscillator (112, 106) with a received signal to produce in-phase (i) and quadrature (q) components. The direction of the phase of the signal is detected as it crosses the i and q axes. The direction of the phase rotation is kept track of by a bi-directional counter (123) in order to demodulate multi-level digital signals. A positive rotation increments the bi-directional counter (123). Conversely, a negative direction decrements the counter (123). The final count of the counter (123) is used by a decision device (124) to establish the content of the received information signal.
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