Communications: directive radio wave systems and devices (e.g. – Directive – Including a steerable array
Reexamination Certificate
1998-12-17
2001-06-05
Blum, Theodore M. (Department: 3662)
Communications: directive radio wave systems and devices (e.g.,
Directive
Including a steerable array
C330S12400D
Reexamination Certificate
active
06243038
ABSTRACT:
BACKGROUND OF THE INVENTION
It is common to utilize radio frequency (RF) signals, having particular characteristics, in conducting information communication such as voice and data communication. For example, wireless communications, including cellular, global system for mobile (GSM) and personal communication services (PCS), utilize RF signals of predefined frequencies of particular bandwidths, in order to transmit information between two communication nodes.
Multiple schemes have been developed to conduct a plurality of simultaneous communications without substantial interference there between. For example, frequency division has been utilized to divide available spectrum into channels assignable to particular ones of the communication nodes in order to provide for their intercommunication, such as is used in the Advance Mobile Phone Service (AMPS) and narrowband AMPS (N-AMPS). Likewise, code division multiple access (CDMA) has been utilized, such as provided for in Interim Standard 95 (IS-95), to assign chip codes to particular ones of the communication nodes in order to provide for their intercommunication over a broadband carrier simultaneously utilized by other ones of the communication nodes. Similarly, time division multiple access (TDMA) schemes have been utilized, such as provided for under the United States Digital Cellular System (USDC) standard IS-54, to distribute time bursts of available communication capacity among communication nodes. Additionally, in establishing a wireless communication infrastructure providing for multiple service providers, portions of available spectrum in the United States have been established to allow provision of wireless communication services, regardless of the particular scheme utilized for providing the communications, i.e., “A band” service provider and “B band” service provider in the same geographic area.
In providing the above described communications, it is often necessary to manipulate signals as they pass through, or are otherwise handled by, the communication system in order that they may be utilized in a desired manner. Typically in wireless communication systems, as well as other systems, signal amplification is necessary in order to provide a signal which exhibits proper characteristics, such as is provided to a receiving communication node with a desired signal magnitude or signal to noise (S/N) ratio. However, in order to provide a desired amplified signal without introducing distortion or other undesired characteristics it is often necessary to utilize costly equipment such as linear power amplifiers (LPA). Moreover, as such communications may include multiple nodes operating within a same area, although upon different assigned channels i.e., multiple subscriber units operating within a single sector of a cellular communication system cell, signal amplification associated with a particular antenna, or other common signal path, must provide linearity throughout a wide range of frequencies, further necessitating the use of costly equipment.
Accordingly, solutions in the past have included the disposing of various forms of LPAs in the signal paths of RF communication signals. For example, feed forward LPA amplifier technology has been utilized, although such technology is relatively expensive as typical feed-forward LPAs use internally generated pilot tones to assist in the adjustment of internal settings necessary for the linearization of multiple carrier or complex waveform signals. Moreover, where multiple LPAs are required, such as in a distributed amplifier configuration or where multiple antenna beams each have associated therewith a LPA, the replication of the above internal circuitry, and therefore its added expense, is required for each amplifier.
Therefore, a need exists in the art for a system and method for providing a signal in a desired condition without introducing distortion or other undesired characteristics through its manipulation. There is a further need in the art for the provision of the signal in a desired condition through the use of less complicated and less costly equipment. Moreover, there is a need in the art for providing such signals in the desired condition irrespective of the scheme, or schemes, utilized to allow multiple simultaneous communications.
SUMMARY OF THE INVENTION
These and other objects, features and technical advantages are achieved by a system and method which utilizes an externally generated signal or pilot signal, preferably in the form of an emulated CDMA (IS-95) carrier, injected at a pre-defined frequency into the signal path prior to the LPA, or LPAs, utilized to provide amplification. Accordingly, LPAs which do not include circuitry for generation, injection, and removal of an internal pilot signal, as well as their added expense and complexity, may be utilized in the provision of signals having a desired condition.
Preferably, the frequency of the emulated CDMA carrier is near that of RF signals of interest to be manipulated according to the present invention in order that the linearity of amplification of these signals of interest may be accurately controlled through use of the emulated pilot signal. For example, in a preferred embodiment, where the manipulated signals are cellular telephone communications, the frequency of the CDMA carrier is within the 25 MHZ cellular base transceiver station (BTS) transmit band, although not within the operator's licensed band. Alternatively, the frequency of the CDMA carrier is selected to be outside both the BTS transmit band and the operator's licensed band, i.e., where a BTS is operated within a cellular A band, the emulated CDMA carrier is within the cellular B band.
According to the present invention, use may be made of amplifiers having substantially less circuitry, and therefore expense, in order to provide signals having a desired magnitude. For example, multi-channel amplifiers (MCA) such as model NTGS 86A8, available from Powerwave Technologies, Inc., 2026 McGaw Avenue, Irvine, Calif. 92614, which provide linear power amplification through the use of digital signal processing (DSP) and the presence of a communicated CDMA signal as the basis of optimizing the MCA parameters.
A preferred embodiment of the present invention utilizes a plurality of amplifiers in a matrix in order to provide distributed amplification of signals of interest. As such, any signal provided at an input of the matrix will appear at each of the amplifiers. Accordingly, this embodiment of the present invention may further reduce the circuitry and costs involved by introducing the emulated pilot signal at a single input of the distributed amplifier matrix while still providing the pilot signal necessary for proper amplification of the signals of interest.
It is a technical advantage of the present invention that manipulation of signals of interest to provide a desired characteristic may be accomplished utilizing less expensive and less complicated circuitry than required in the prior art. Furthermore, a technical advantage is realized through the use of circuitry adapted for use with broadband signals, such as CDMA carriers, in providing manipulation of signals of interest although communicated utilizing narrowband channels or otherwise non-compatible signals.
A still further technical advantage is realized according to the present invention as the speed of adjustments necessary for desired operation of the amplifiers may be improved as the frequencies of the emulated pilot signal are pre-selected, and therefore known, and thus the circuitry would not be required to acquire the frequency, as it is known a priori.
The foregoing has outlined rather broadly the features and technical advantages of the present invention in order that the detailed description of the invention that follows may be better understood. Additional features and advantages of the invention will be described hereinafter which form the subject of the claims of the invention. It should be appreciated by those skilled in the art that the conception and specific embodiment
Butler Ray K.
Chesarek Richard H.
Posner Richard D.
Blum Theodore M.
Fulbright & Jaworski L.L.P.
Metawave Communications Corporation
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