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Device and method for detecting and readucing intermodulation distortion

An amplitude, digital signal technology, applied in the field of detecting intermodulation distortion and reducing intermodulation distortion, to achieve the effect of reducing IMD interference

Inactive Publication Date: 2003-04-09
NOKIA CORP
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

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  • Device and method for detecting and readucing intermodulation distortion
  • Device and method for detecting and readucing intermodulation distortion
  • Device and method for detecting and readucing intermodulation distortion

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Embodiment Construction

[0066] The following detailed description of the preferred embodiment illustrates the application of the method and apparatus of the present invention to a CDMA mobile phone. It should be noted that because intermodulation distortion creates interference in many RF systems, and is a significant problem in mobile phones, the methods described here are equally applicable to other broadband-based mobile phones, including PCS1900 mobile phones.

[0067] The detailed description that follows utilizes a number of acronyms that are generally known in the art. Table 1 below gives a list of acronyms and their respective definitions, although these definitions, for convenience, only give examples of the first use of each acronym.

[0068] Acronym Definition

[0069] A / D Analog to Digital (Converter)

[0070] AGC Automatic Gain Control

[0071] AMPS Advanced Mobile Phone System

[0072] ASIC application specific integrated circuit

[0073...

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Abstract

In the front end of a CDMA cellular or broadband PCS mobile phone receiver, a switched bypass connection is provided to bypass the low noise amplifier, sending the received signal through an amplifier bypass connection. The amplifier bypass connection may include an attenuator. The switched bypass is activated by a control signal generated by a digital signal processor. The digital signal processor analyzes the received signal to detect and determine the relative contribution of the IMD interference to the total received signal power and, when the IMD interference exceeds a predetermined level, sends a control signal to bypass the low noise amplifier. Identification of the presence of IMD interference is by spectral estimation to discern when the mobile phone is in the presence of large near-band signals from an AMPS or other narrow-band base station which causes in- band IMD. In a preferred embodiment, the spectral estimation is performed by collecting a series of data samples from the received signal and, using a digital signal processor (DSP), computing a Discrete Fourier Transform (DFT) to generate frequency domain data, passing the data through a filter bank, then using a decision algorithm to determine whether or not there is sufficient IMD present in the received signal to bypass the LNA. If the IMD level is high enough to warrant bypass of the LNA, the DSP will provide a signal to an automatic gain control (AGC) block for controlling a variable gain amplifier (VGA) to compensate for gain loss due to bypass of the LNA.

Description

field of invention [0001] The present invention generally relates to methods and apparatus for detecting and reducing intermodulation distortion (IMD) in code division multiple access (CDMA) mobile telephone systems. Background technique [0002] The rapid growth rate of cellular mobile telephone subscribers, the need for cellular telephones not only for voice but also for data transmission, and the limited capacity of analog cellular systems are driving the implementation of digital cellular systems to provide increased capacity and higher quality Signal. In some respects, there may be a complete transition from analog to digital systems. Until then, however, both systems must coexist, and since there will be no additional spectrum allocated to digital cellular, digital and analog cellular systems must share the same spectrum -- 869-894MHZ for receive signals and 824-849MHZ for to send a signal. [0003] Digital cellular systems using CDMA (Code Division Multiple Access)...

Claims

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Application Information

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Patent Type & Authority Patents(China)
IPC IPC(8): H04B1/10
CPCH04B1/7102H04B1/1027H04B7/26
Inventor T·J·肯莱I·尼瓦S·D·格莱J·道宁
Owner NOKIA CORP