Shortened wideband decoupled sleeve dipole antenna
AssigneeMotorola, Inc.
InventorsJames P. Phillips, Henry L. Kazecki
Life of this patent
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Abstract
A shortened wideband decoupled sleeve dipole antenna is disclosed in which a helically wound upper radiating element and an inductively loaded lower radiating sleeve element reduce the linear size of the antenna. Substantial decoupling is provided by a helically wound feed coaxial transmission line within the sleeve element. A matching network at the antenna feed point provides capacitive reactance above the antenna resonant frequency and inductive reactance below the antenna resonant frequency such that an impedance match between the feed coaxial transmission line is obtained at frequencies above and below the resonant frequency and dual-band performance may be obtained.
Claims14
A wideband shortened decoupled sleeve dipole antenna comprising:
- a helically wound first radiating element tuned to a center resonant frequency and having first and second opposing ends and a central axis;
- a cylindrical second radiating element tuned to said center resonant frequency and having first and second opposing ends and a central axis, said first end of said second radiating element disposed adjacent to said first end of said first radiating element and said second radiating element central axis essentially collinear with said first radiating element central axis;
- a coaxial transmission line of a predetermined impedance disposed within said second radiating element, said transmission line helically wound about said second radiating element axis, and having first and second opposing ends, the outer conductor of said coaxial transmission line at said first end coupled to said first end of said first radiating element and the inner conductor of said coaxial transmission line at said first end coupled to said first end of said first radiating element, and said second end of said coaxial transmission line, adapted to couple to an antenna utilization means, emanating from said second end of said second radiating element;
- and
- a matching network, coupled to said coaxial transmission line at said first end, tuned to said center resonant frequency, and having reactive impedance components at frequencies above and below said center resonant frequency, to substantially impedance match said coaxial transmission line impedance to the impedance of said first and second radiating elements at said center resonant frequency and at frequencies a predetermined amount above and below said center resonant frequency.
A dual-hand shortened decoupled sleeve dipole antenna especially adapted for duplex portable transceiver use and having two hands of frequencies at which the antenna return loss is optimized, comprising:
- a helically wound first radiating element of a length producing an electrical quarter wavelength at a center frequency and having first and second opposing ends and a central axis;
- a slotted cylindrical second radiating element of a length producing an electrical quarter wavelength at said center frequency and having first and second opposing ends and a central axis, said first end of said second radiating element disposed adjacent to said first end of said first radiating element and said second radiating element central axis essentially collinear with said first radiating element central axis;
- a coaxial transmission line of a predetermined impedance disposed within said second radiating element and helically wound about said second radiating element axis to decouple the antenna from said coaxial transmission line, said coaxial transmission line having first and second opposing ends, the outer conductor of said coaxial transmission line at said first end coupled to said first end of said first radiating element and the inner conductor of said coaxial transmission line at said first end coupled to said first end of said first radiating element, and said second end of said coaxial transmitting line, adapted to couple to an antenna utililzation means, emanating from said second end of said second radiating element;
- and
- parallel tuned matching network, coupled between said coaxial transmission line inner conductor and outer conductor at said first end, tuned to said center frequency, and having a capacitive reactance above said center frequency and inductive reactance below said center frequency to substantially impedance match said coaxial transmission line to said first and second radiating elements at a first band of frequencies above said center frequency and at a second band of frequencies below said center frequency.
Dependencies are inferred from the claim text.