A novel pulse swallow based frequency divider circuit for a phase-locked loops

A new and unique frequency divider circuit has been proposed for this work. In this paper, we have implemented a fractional-N PLL using a proposed pulse swallow based frequency divider and a programmable prescaler divider circuit. Advantages of the proposed pulse swallow based frequency divider circuit have been illustrated and its usefulness are described in details. This novel pulse swallow based frequency divider technique does not include any reset or reload signal for the swallow counter as it is normally triggered by the SR latch output signal in conventional pulse swallow based frequency divider circuit. Insertion of a variable delay element at the output of the program counter can be eliminated which is normally used to settle the problem of arrival of the falling edge of the swallow counter pulse. In addition, preset enable signal can be generated without any frequency dependent delay generation block and in few cases without selection of any frequency dependent RC network block. The residual phase noise output of the divider at 1 MHz offset frequency is dBc/Hz for a carrier signal frequency of 4.7 GHz and power consumption is 9 mW from a 1.2 V power supply. The design of the fractional-N PLL has been carried out in 130 nm standard CMOS process. There is no zero division in the proposed frequency divider's swallow counter for any counting state due to the novel mathematical calculating algorithm for the pulse swallow divider circuit.