WLAN_semi_RalinkLu°ìRF]-p°DPDJin LuoJin_luo@ralinktech.com.twSeptember 29, 2003The Concept of RF System¤b¤¤ug (°WH)[t¤GWvà (RF VCO)±i¤@Wvà (IF VCO)Pü¨¤ò°ax (P]-psy) (MAC,BB)Heterodyne Receiver StructureA DIAntenna Band Select Filter Image Reject Channel Select Filter RF Mixer Filter (SAW)IF VCOLNA VGA90oRF VCOQA DhAdvantage-Good Sensitivity (Good Image Suppression) -Good Channel Selectivity -Most of today’s RF SystemhDisadvantage-Need many off chip Components -Large Chip size -High Power ConsumptionHomodyne Receiver Structure (Zero-IF)Channel Select Filter RF MixerIAntenna VGA Preselect FilterA DRF VCOLNA90oQhAdvantage-No Image Filter Required -No need 50 matching of LNA output -No need IF Filter (Low Cost) -Monolithic Integration……