Telecommunications – Receiver or analog modulated signal frequency converter – Modulation distortion or cross talk correction or elimination
Reexamination Certificate
1998-12-21
2002-05-28
Chang, Vivian (Department: 2682)
Telecommunications
Receiver or analog modulated signal frequency converter
Modulation distortion or cross talk correction or elimination
C455S207000, C455S296000, C455S313000
Reexamination Certificate
active
06397051
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to the field of radio systems. More particularly, the present invention relates to a system and a method for simultaneously receiving and processing multiple radio frequency (RF) channels.
2. Description of the Related Art
A separate receive path is required in a conventional RF receiver system for each channel carrier frequency so that each desired channel frequency band can be down-converted by a mixer and an associated local oscillator (LO). Consequently, for a single receiver system to simultaneously process multiple RF channels, a corresponding number of receive paths are required, thus increasing the complexity and cost of such a multi-channel receiver over that of a single channel receiver. In view of this drawback, many wireless services attempt to carry as much data as possible on a single RF carrier to avoid using a multi-channel receiver having a separate receive path for each RF channel. Unfortunately, the capacity of a single RF channel is limited and some wireless services provided over a single channel, such as a wireless video service, are severely hampered.
Therefore, what is needed is a technique that can be used for receiving a multi-channel RF signal using a single receive path, thereby avoiding the complexity and costs associated with receiving a multi-channel RF signal using conventional techniques.
SUMMARY OF THE INVENTION
The present invention provides a low-cost, efficient technique for simultaneously receiving and processing multiple RF channels in which each channel has different data rates using a single receive path. The advantages of the present invention are provided by a system and method in which a dual image-reject mixer arrangement receives an RF signal having at least one channel and a local oscillator signal having a frequency component corresponding to each channel of the RF signal. The dual image-reject mixer arrangement generates first and second signals corresponding to each channel of the RF signal, such that the first and second signal corresponding to each channel is substantially equal, and includes a desired signal and an image frequency signal. A feed-forward arrangement receives the first and second signals corresponding to each channel and outputting a third signal that is formed by constructively combining the desired signals corresponding to each channel and substantially cancelling the intermodulation signals corresponding to each channel. An in-phase and quadrature hybrid network receives the third signal and outputs an in-phase baseband signal and a baseband signal corresponding to each channel of the RF signal. According to the invention, a controller coupled to the dual image-reject mixer arrangement and monitors the first and second signals. The controller controls an amplitude and a phase of the image frequency signals so that the image frequency signals are collectively minimized based on the monitored first and second signals. The controller is also coupled to the feed-forward arrangement and monitors the third signal. Based on the monitored third signals, the controller controls the amplitude and the phase of the intermodulation signals so that the intermodulation signals are collectively optimally cancelled.
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Abbasi Salman Yousef
Barzegar Farhad
Okoro Jeremiah
Appiah Charles N.
AT&T Corporation
Chang Vivian
Morgan & Finnegan , LLP
Redmond, Jr. Joseph C.
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