| 摘要 |
In apparatus for generating the family of PSK (phase shift keyed) modulations, which include BPSK (binary PSK), QPSK (quaternary PSK), MSK (minimum shift keying) and the like, the carrier is generated in a phase-locked-loop (PLL) with the desired digital information already phase-modulated onto it. The proposed scheme differs from common practice approaches, which are usually implemented by linear synthesis (an AM technique); rather, it employs direct nonlinear synthesis (an FM technique). The invention yields good phase precision with arbitrary spectral shaping under the constraint of constant envelope signaling. It permits the connection of the output of a simple, inexpensive VCO (voltage controlled oscillator) directly to a system's antenna without the need for intervening circuit elements such as phase splitters, mixers, and the like. The resulting minimal implementation will lend itself well to the power, size and cost constraints of a microminiature radio transmitter as might be required, for example, for the up-link of a wrist-phone style communicator. <IMAGE>
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