Telecommunications – Transmitter and receiver at same station – Radiotelephone equipment detail
Utility Patent
1999-06-30
2001-01-02
Nguyen, Lee (Department: 2746)
Telecommunications
Transmitter and receiver at same station
Radiotelephone equipment detail
C455S025000, C455S422100, C455S447000, C342S011000, C343S753000
Utility Patent
active
06169910
ABSTRACT:
BACKGROUND OF THE INVENTION
(1) Field of the Invention
This invention relates to line-of-sight wireless communication systems for microwave and millimeter wave communication, and more particularly to a wireless communication system for point-to-point or point-to-multipoint communication which uses a dielectric material lens antenna to focus received or transmitted information carrying radio frequency (rf) signals.
(2) Description of Related Art
The design of many radio frequency (rf) communication systems is based on stationary reflective, parabolic antennas. Such antennas are capable of transmitting and receiving narrow beam rf signals. A major disadvantage of such antennas is that they are not directionally agile. Such antennas can only transmit signals in one direction. This means that a communication system based on parabolic antennas typically has a series of antenna arrays, each array comprising a plurality of antennas for receiving incoming signals, and another plurality of antennas for transmitting signals to the next antenna array. These systems are typically used for transmitting signals over long distances.
Another type of wireless communication system is cellular communication. For cellular communication between a first communication device and a second communication device within a cell, the communication devices broadcast and receive signals from and to a base station. The frequency of the signals broadcast from the base station and the frequency of the signals received by the base station are different. The different frequencies allow for simultaneous reception and transmission of information by a communication device. The ability to simultaneously receive and transmit information in one device is called duplex communication.
The base station of a cellular cell typically comprises an antenna array having circuitry and computer control for receiving incoming signals, for transforming the signals without losing the information carried by the received signals, and an array of transmit antennas for transmitting the transformed signals to another communication device. Typically, each antenna is a dipole antenna. A major disadvantage of the transmit antennas currently used is that the antennas broadcast omnidirectionally. A more efficient communication system can be established if the transmit antennas are capable of beaming a signal directly to a desired receiver or receivers.
In wireless communications, signal fading is a major problem. Minimizing or eliminating the effects of fading is important to successful free-space communication. Some methods for curing the fading problem are space diversity, frequency diversity, time diversity, and polarization diversity broadcasting.
In wireless communications it is also desirable to be able to accommodate a large number of simultaneous users without a loss in signal quality due to interference from other information signals. Several methods for increasing the number of users that can use a communication system at the same time have been developed. Among these methods are frequency division multiplexing, time division multiplexing, code division multiplexing, and space division multiplexing.
In wireless communication, it is desirable for a base station to have a beam forming antenna. A beam forming antenna is an antenna that has the capability to form multiple rf beams which can be directed beams in selected directions. With such a capability, the base station and adjacent base stations can employ frequency reuse. Frequency reuse is the ability of a base station and adjacent base stations to use the same frequency to communicatively connect different users in separate communication systems without interference due to the use of the same frequency. The ability to employ frequency reuse increases the number of users who can use a communication network. With current cellular communication systems, frequency reuse is employed in cells that are separated by a sufficient distance so that the signals from a first cell using a particular frequency will not interfere with the signals of another cell using the same frequency. With beam forming antenna, frequency reuse can be utilized within a cell and between adjacent cells.
U.S. Pat. No. 5,485,631, issued to Bruckert describes a multiple sectorized antenna system which achieves a low reuse factor. The reuse factor characterizes the proximity of the closest base station which can reuse a particular frequency. U.S. Pat. No. 5,260,968, issued to Gardner et al., describes a communication system which uses a multiple array antenna and space division multiplexing. U.S Pat. No. 4,819,227, issued to Rosen, shows beam forming for frequency reuse in satellite communication systems. Again, the system uses a multiple antenna array for beam forming. U.S. Pat. No. 4,730,310, issued to Acampora et al., shows a communication system which uses a large main reflector or a phased array antenna in conjunction with time division multiplexing to provide a communication system capable of frequency reuse within a communication cell.
A key aspect of the present invention is the use of a dielectric material lens in a communication system to focus received or transmitted rf signals which pass through the lens. Such lenses have been used in other arts for many years. The lenses have been used as passive reflectors, and as antennas in radar systems involving navigation and aircraft landing. U.S. Pat. No. 3,703,723, issued to Albanese et al., describes a Luneberg lens used as a passive reflector. U.S. Pat. No. 4,287,519, issued to Doi, describes a Luneberg lens used as an antenna system which takes the place of three separate high gain antennas. U.S. Pat. No. 4,031,535, issued to Isbister, describes a multiple frequency navigation radar system for determining the location and identification of navigational markers.
U.S. Pat. No. 4,806,932, issued to Bechtel, describes a radar-optical transponding system for use in aircraft landing systems. A transceiver on an aircraft sends a signal to a ground based lens. The lens focuses the signal onto a transponder array, which adds identifier information and meteorological data to the signal and re-transmits the signal back to the aircraft's transceiver. The signal transmitted to the aircraft is used to guide the aircraft.
SUMMARY OF THE INVENTION
(1) Progressive contribution to the art
We have invented a communication system for point-to-point or point-to-multipoint communication which uses a dielectric material lens antenna to focus received or transmitted rf energy. The communication system is capable of serving multiple users and of handling multiple simultaneous communication links between various users. The communication system can be designed so that the lens is used only to transmit rf signals. Alternatively, the communication system can be designed so that the lens is capable of simultaneously transmitting and receiving rf signals. The lens is directionally agile, and is capable of receiving and transmitting signals throughout a 360 degree area surrounding the lens.
When used to receive rf energy, the dielectric material lens focuses incoming rf signals onto signal processing equipment. When used to transmit rf energy, the dielectric material lens focuses outgoing rf signals into narrow beam signals which are transmitted directly to a desired receiver or receivers.
The lens and signal processing equipment can be directly connected to a communication device, or the lens and signal processing equipment can act as a repeater, also called a base station. If the lens and signal processing equipment are directly connected to a communication device, signals received by the lens are fed to the signal processing equipment, and the resulting signal is sent to a user interface. Output signals from the user interface are processed by the signal processing equipment and sent to the lens where the signals are broadcast as narrow beam rf signals directly to a second communication device or communication devices.
If the lens and signal processing equipment are used as repeate
Carey Douglas F.
Chapman Aubrey I.
Chapman Rita
Tamil Lakshman S.
Chapman Rita
Focused Energy Holding Inc.
Fulbright & Jaworski
Nguyen Lee
LandOfFree
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