Helical antenna for portable phones and manufacturing method thereof

A dual band helical antenna comprising:

• a first dielectric core having a substantially cylindrical shape with an outer circumferential surface on which a first spiral groove is formed;
• a first conductive strip deposited on the first spiral groove and having a length of one-fourth of a first wavelength;
• a second dielectric core, positioned under said first dielectric core, having a substantially cylindrical shape with an outer circumferential surface on which a second spiral groove is formed;
• a second conductive strip deposited on the groove of said second dielectric core, electrically connected to said first conductive strip, and having a length of one-fourth of a second wavelength;
• a feeding conductor, placed under said second dielectric core, for providing an electrical connection between said second conductive strip and an external circuit;
• and
• an antenna cover for enclosing said first and said second dielectric cores and said feeding conductor.