Communications: radio wave antennas – Antennas – Active sleeve surrounds feed line
Reexamination Certificate
2001-10-30
2003-04-22
Nguyen, Hoang (Department: 2821)
Communications: radio wave antennas
Antennas
Active sleeve surrounds feed line
C343S791000
Reexamination Certificate
active
06552692
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to the field of antennas, more specifically to a dual band dipole antenna adapted to receive and transmit high frequency signals, such as cellular telephone signals.
BACKGROUND OF THE INVENTION
With the growth of wireless communications, there has been an increased growth in the use of cellular technology to receive and transmit information using high frequency signals. Concurrent with the wireless growth has been the emergence of different very high frequency signal bands that these wireless devices may use.
Prior antennas have been designed to effectively receive and transmit signals along a specific frequency band, such as the cellular band or the AM/FM bands associated with most radios. Often times, an antenna must be designated to a specific frequency band due to the design and orientation of the various components. Most commonly, an antenna has a radiating element that provides the carrier wave for the transmitted host information. The relationship of the radiating element to other components restricts an antenna from varying its frequency range beyond a minimum threshold.
Cellular transmissions oscillate at a frequency between 824.04 and 893.7 MHz. An early analog cellular standard was called Advanced Mobile Phone System (AMPS). Newer developments in technology allows for cellular transmission to be in digital format, providing for signal compression and easier signal manipulation, thus increasing the available transmission bandwidth. Cellular telephones are duplex devices, providing for the transmission of dual signals, thus allowing a user to simultaneously transmit and receive data, with each signal being on a different frequency.
A transmission band commonly used with cellular technology is Global System for Mobile Communications (GSM), which provides encryption to the signal making the transmission more secure. This standard was initially established within Europe in the mid-1980s. GSM operates in the frequency band of 0.9 GHz within the United States and is used in conjunction with the Personal Communication System (PCS) based system.
A PCS phone operates in a frequency range between 1.85 and 1.99 GHz. A standard cellular transmission may be in AMPS, GSM, PCS, or PCN. These various standards are not completely interchangeable, therefore, a device may need to switch between standards to work properly.
Cellular antennas used for transmitting information along the cellular band are most commonly used with mobile devices, such as a telephone or a personal digital assistance (PDA). One common antenna assembly is taught by U.S. Pat. No. 5,440,317 issued to Jalloul et al., teaching a known assembly for a half wavelength sleeve dipole antenna having a coaxial line section followed by a quarter wavelength choke for reducing interference with the housing. U.S. Pat. No. 5,440,317 further teaches the interconnection of the various antenna elements, wherein several elements have a length of one-fourth of the wavelength of the corresponding frequency.
Although, U.S. Pat. No. 5,440,317 only teaches a single sleeve element, wherein the antenna is equipped to transmit and receive communications along a single frequency band. It is also known within the art to produce an antenna capable of transmitting and receiving in certain multiple bands. Specifically, U.S. Pat. No. 5,079,562 issued to Yarsunas et al. teaches a multi-band antenna adapted to receive and transmit signals in two bands, one in the cellular band and the other in the AM/FM band.
U.S. Pat. No. 5,440,317 teaches an AM/FM band antenna coaxially aligned with a cellular band antenna. The AM/FM antenna is formed of tubular rods, wherein the cellular antenna is formed of a centered coaxial dipole. U.S. Pat. No. 5,440,317 also teaches of a choke placed between the antennas to reduce or eliminate any interference between the AM/FM transmission/reception and the cellular band reception/transmission. This patent teaches the transmission and reception of only a single cellular band in conjunction with an AM/FM band. Furthermore the antenna is explicitly designed to not be used in multiple cellular bands, but is rather exclusively limited to a multi-band antenna consisting of an AM/FM band and a cellular band due to poor isolation between the antenna portions.
As such, there currently exists a need in the art for an antenna assembly capable of receiving and transmitting signals in multiple cellular bands without these signals being subject to various degradations.
SUMMARY OF THE INVENTION
The present invention provides an antenna assembly capable of transmitting in a plurality of cellular bands, such as AMPS/PCS or GSM/PCN. The antenna comprises a center-fed coaxial dipole having a first and second element for radiating and receiving electromagnetic energy in a plurality of frequency bands. The second element includes a first portion and a second portion, wherein the first and second portions, and the first element, have a length equivalent to approximately one-quarter wavelength of approximately the mid-range of each frequency band.
The first element is configured as a whip. The first portion is configured as an inner conductive cylindrical sleeve coaxially aligned with the first element. The second portion is configured as an outer conductive cylindrical sleeve coaxially aligned with the inner sleeve and the first element.
The antenna further comprises a coaxial conductor having inner and outer conductors and being axially aligned with the center-fed coaxial dipole and extending through the second element of the dipole. The inner conductor of the coaxial conductor is electrically connected to the whip and the outer conductor of the coaxial conductor is electrically connected to the second element.
The antenna also has a coaxial choke, formed of a cylindrical sleeve of electrically conductive material, disposed about and axially aligned with the coaxial conductor. The coaxial choke has a length equivalent to approximately one-quarter wavelength of the frequency at approximately the mid-range of one of the frequency bands. The choke has a first end, which is remote from the dipole, being connected to the outer conductor of the coaxial conductor, and a second end which is disposed nearest the dipole, being spaced from the second element by a distance equivalent to approximately one-quarter wavelength of the frequency at approximately the mid-range of one of the frequency bands.
The antenna further comprises a housing consisting of a dielectric material, circumferentially encasing the dipole, a coaxial choke, and a portion of the coaxial conductor. The antenna also has a top insert that is fitted on the top of the housing and contactingly engages the whip portion of the dipole. Moreover, the antenna has a bottom insert which is fitted on the bottom of the housing and allows the coaxial conductor to pass therethrough. The bottom insert may then be attached to a mounting assembly.
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Zeilinger Steven
Zuniga Felipe
Andrew Corporation
Nguyen Hoang
Vedder Price Kaufman & Kammholz
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