Design And Characterization Of Compact, High Performance, Planar Couplers And Filters For Rf And Wireless Applications.: In Recent Times, The Rapid Advancement Of Wireless Technology Has Been Mainly Driven By The Demands Of The Cellular Industry. Taking This Demand As A Cue A Number Of High Performance Passive Components Having New Topologies Have Been Developed. The Development And Research Into New Component Topologies Requires Numerical Characterization And Modeling Of Basic Structures. The Finite Difference Time Domain (Fdtd) Technique And Also Commercial Full Wave Electromagnetic Simulator Ie3dtm Have Been Used To Analyze Microstrip Line And Defected Ground Structures (Dgs). Firstly, Compact Branch-Line Couplers Using Two New Approaches Are Presented. One Of Them Is Designed To Suppress The Odd Harmonics. Next A Dual Band Hybrid Ring Operating At 900 Mhz & 1900 Mhz Is Presented. Conventional Low Pass Filter (Lpf) Using Stepped Impedances, Open Stubs Etc. Suffers From Narrow Stop Band And Poor Cutoff Characteristics Due To The Frequency Distributed Behavior Of Finite Extended Transmission Line. To Overcome These Drawbacks, Three Novel Lpfs Having Compact Size, Sharp Transition Knee And Wide Stop Band Are Developed Using Dgs, Spurline, Compact Microstrip Resonant Cell (Cmrc), And Complementary Split Ring Resonator (Csrr). Finally, A Novel Compact Ultra Wideband (Uwb) Bandpass Filter (Bpf) Is Presented Using Parallel Coupled Microstrip Line (Pcml) And Dgs.