| 摘要 |
A circuit for providing phase shifted I and Q output signals from a received FSK modulated signal and the method of its operation. The circuit includes apparatus for receiving an FSK modulated signal, first, second and third mixers, to which the received FSK modulated signal is applied, a local oscillator, generating an oscillator signal and phase shifters providing first, second and third phase shifted versions of the oscillator signal to the first, second and third mixers to produce first, second and third mixer output signals which are likewise phase shifted. The mixer output signals are provided to summing circuits providing an I output signal corresponding to the difference between the first and second mixer output signals, a Q output signal corresponding to the difference between the second and third mixer output signals. The second version of the oscillator signal may be shifted 90 degrees relative to the first version of the oscillator signal and the third version of the oscillator signal may be shifted 90 degrees relative to the second version of the oscillator signal. Preferably the first, second and third mixers are all fabricated on the same integrated circuit chip.
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