document: Fast frequency acquisition phase-frequency detectors for Gsamples/s phase-locked loops This paper describes two techniques for designing phase-frequency detectors -LRB- PFDs -RRB- with higher operating frequencies -LSB- periods of less than 8 * the delay of a fan-out-4 inverter -LRB- FO-4 -RRB- -RSB- and faster frequency acquisition . Prototypes designed in 0.25 - mu m CMOS process exhibit operating frequencies of 1.25 GHz -LSB- = 1 / -LRB- 8.FO-4 -RRB- -RSB- and 1.5 GHz -LSB- = 1 / -LRB- 6.7.FO-4 -RRB- -RSB- for two techniques , respectively , whereas a conventional PFD operates at < 1 GHz -LSB- = 1 / -LRB- 10.FO-4 -RRB- -RSB- . The two proposed PFDs achieve a capture range of 1.7 * and 1.4 * the conventional design , respectively
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