Textbook in PDF format Recently, wireless LAN standards have emerged in the market. Those standards operate in various frequency ranges. To reduce component count, it is of importance to design a multi-mode frequency synthesizer that serves all wireless LAN standards including 802.11a, 802.11b and 802.11g standards. With different specifications for those standards, designing integer-based phase-locked loop frequency synthesizers can not be achieved. Fractional-N frequency synthesizers offer the solution required for a common multi-mode local oscillator. Those fractional-N synthesizers are based on delta-sigma modulators which in combination with a divider yield the fractional division required for the desired frequency of interest