A　compact　quadrangular　prism-shaped　slot　helix　antenna　with　wide　axial　ratio　(AR)　bandwidth　using　a　spiral　microstrip　coupling　feedline　is　presented.　The　proposed　antenna　is　constructed　with　FR4　substrate　copper-clad　plate　with　four　slots　symmetrically　etched　on　the　substrate　exterior　surface　and　a　spiral　microstrip　coupling　feedline　printed　on　the　substrate　inner　surface.　The　electric　field　and　equivalent　magnetic　current　excited　by　the　spiral　microstrip　feedline　in　slots　are　analyzed.　The　wide　AR　bandwidth　is　obtained.　The　proposed　antenna　has　a　small　dimension　of　0.156　lambda(0)　x　0.156　lambda(0)　x　0.182　lambda(0)　(lambda(0)　is　the　free-space　wavelength　at　the　center　frequency).　Its　measured　-10　dB　|S-11|　bandwidths　and　3　dB　AR　bandwidths　are　1525-1662　and　1497-1630　MHz,　respectively.　It　generates　right-hand　circular　polarization　(RHCP)　without　a　complicated　feeding　network.　It　promises　a　good　use　in　Global　Navigation　Satellite　Systems.