Dual band phased array employing spatial second harmonics

Details Dual band phased array employing spatial second harmonics Dual band phased array employing spatial second harmonics

2002-11-08

2004-06-22

Ho, Tan (Department: 2821)

Communications: radio wave antennas

Antennas

Antenna with parasitic reflector

C343S833000, C342S372000

Reexamination Certificate

active

06753826

ABSTRACT:

BACKGROUND OF THE INVENTION
As wireless networks mature and become more widely used, higher data rates are offered. An example of such a wireless network is a wireless local area network (WLAN) using an 802.11 protocol. The 802.11 protocol specifies a 2.4 GHz ISM (Industrial, Scientific and Medical) band (802.11b) for the traditional service, and, for newer, higher data rate services, a 5 GHz UNII (Unlicensed National Information Infrastructure) band (5.15 GHz through 5.825 GHz in three subbands) (802.11a) and 2.4 GHz ISM band (802.11g), which uses different transmission coding from 802.11b.
As with other radios, a wireless network adapter includes a transmitter and receiver connected to an antenna. The antenna is designed to provide maximum gain at a given frequency. For example, if a monopole antenna were designed to operate most effectively at 2.4 GHz, it would not optimally support operation at 5 GHz. Similarly, if a directive antenna were designed to operate most effectively at 5 GHz, backward compatibility with 2.4 GHz 802.11 would be compromised.
SUMMARY OF THE INVENTION
To address the issue of having compatibility with multiple wireless network carrier frequencies, an inventive directive antenna provides high gain and directivity at multiple operating frequencies. In this way, a system employing the inventive directive antenna is compatible with multiple wireless systems, and, in the case of 802.11 WLAN systems, provides compatibility at the 2.4 GHz and 5 GHz carrier frequencies, thereby providing backward and forward compatibility.
A broad range of implementations of the directive antenna are possible, where spacing, length, antenna structure, reactive coupling to ground, and ground plane designs are example factors that are used to provide the multi-frequency support. Multiple spatial-harmonic current-distributions of passive element(s) that are parasitically coupled to at least one active antenna element are used to create multiple frequency bands of operation.
In one embodiment, the inventive directive antenna, operable in multiple frequency bands, includes an active antenna element and at least one passive antenna element parasitically coupled to the active antenna element. The passive antenna element(s) have length and spacing substantially optimized to selectively operate at (i) a fundamental frequency associated with the active antenna element or (ii) a higher resonant frequency related to the fundamental frequency. The higher resonant frequency may be a second harmonic of the fundamental frequency.
The directive antenna may also include a device(s) operatively coupled to the passive antenna element(s) to steer an antenna beam formed by applying a signal at the fundamental or higher resonant frequency to the active antenna element to operate in the multiple frequency bands.
The directive antenna may steer the antenna beams at the fundamental frequency and the higher resonant frequency simultaneously.
The directive antenna may further include reactive loading elements coupled by the switches between the passive antenna element(s) and a ground plane. The reactive loading element(s) may be operatively coupled to the passive antenna element(s) to make the associated passive antenna element(s) a reflector at the fundamental frequency. The same reactive loading may turn the associated passive antenna element into a director at the higher resonant frequency. The opposite conditions may also be achieved by the reactive loading element(s).
The antenna elements may be monopoles or dipoles. Further, the antenna elements may be two- and three-dimensional elements that support more than two resonances. The antenna elements may further have length and spacing to support more than two frequency bands. Additionally, the antenna elements may be elements that support higher resonant frequencies that are not integer multiples of the fundamental frequency.
The antenna elements may be arranged in the manner that the higher resonant frequency is a non-integer multiple of the fundamental frequency. The directive antenna may further include an input impedance coupled to the array across the desired bands and can be optimized using optimization techniques, including: addition of a folding arm of proper thickness to the active antenna elements, using lumped impedance elements, using transmission line segments, or a combination of optimization techniques.
The directive antenna may be used in cellular systems, handsets, wireless Internets, wireless local area networks (WLAN), access points, remote adapters, repeaters, and 802.11 networks.


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