Digital Loop-Preset Frequency Synthesizer

A new high-speed frequency switching PLL synthesizer is presented that employs a digital loop-preset (DLP) technique. Its DLP function is realized by using a digital to analog converter (DAC), an analog to digital converter (ADC) and a resettable prescaler. These rapidly preset the PLL to a new frequency. The frequency switching time is analyzed according to preset voltage error and preset phase error. The resulting 1.4 GHz-band digital loop-preset frequency synthesizer (DLPS) with a frequency step of 25 kHz is demonstrated to achieve a switching time of less than Ims. This switching time value is about 1/100th that for conventional PLL frequency synthesizers.