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Balanced transversed I, Q filter for quadrature modulators

A transversal filter, balanced technology, applied in the modulated carrier system, phase modulated carrier system, multi-carrier system and other directions, can solve problems such as difficult DSP30

Inactive Publication Date: 2004-04-21
UNWIRED PLANET
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

[0011] Unfortunately, it is difficult to generate a reference voltage from the DSP 30 that is exactly equal to the voltage provided by the DA converter with an input digital value of zero

Method used

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  • Balanced transversed I, Q filter for quadrature modulators
  • Balanced transversed I, Q filter for quadrature modulators
  • Balanced transversed I, Q filter for quadrature modulators

Examples

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Embodiment Construction

[0039] Fig. 3 shows an alternative of the invention to the combination of inverter 42 and balanced filter 44 of Fig. 2 for implementing a balanced filter.

[0040] The I-bit stream or the Q-bit stream from the (delta-sigma) converter 41 is applied to filters 30 constructed broadly according to FIG. 3 , ie one filter 30 for each I- and Q-bit stream. In other words, one balanced transversal filter of FIG. 3 is used for the I signal and the other is used for the Q signal.

[0041] The I or Q bit stream enters the shift register 50, which has a shift register (50 1 , 50 2 ,..50 N ) in the form of stage chains, each including flip-flops (51 1 , 51 2 ,..51 N ). by a set of different resistor values ​​R 1 , R 2 ,..R N resistance (60 1 , 60 2 ,..60 N ) composed of a first resistor network 60a is connected to the output of the flip-flop, use the q output to get a positive weighted value, use the q output if you want a negative weighted value, as in the shift register stage ...

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Abstract

Radio transmissions are spectrally contained to reduce adjacent channel interference by a method and apparatus for I,Q filtering of signals before quadrature modulation in digital cellular radio transmission systems such as communications systems following the GSM TDMA, IS-54 or IS-95 standards. The filtering is accomplished by multiple stage registers connected at their complementary outputs to identical resistor networks. The outputs of the resistor networks are summed to represent a smoothly transitioning analog representation of the digital voice or data transmission. The analog representation may be additionally low pass filtered to remove higher frequency components before quadrature modulation. Because rapid transmissions in the transmittal signal are avoided, adjacent channel interference is reduced.

Description

technical field [0001] The present invention relates to methods and apparatus for achieving spectral constraints on radio frequency transmissions so as not to cause adjacent channel interference, and in particular to methods and apparatus for achieving spectral constraints on high bit rate digital transmissions such as TDMA or CDMA cellular telephone signals equipment. Background technique [0002] Advances in technology have enabled continued improvements in cellular portable telephone battery life while reducing size and cost. This makes cellular phones even more popular. Accordingly, cellular telephone systems need to be expanded to provide service to a greater number of users. [0003] Pressure on channel availability has prompted the development of digital cellular technologies, eg, the European GSM TDMA system, the US IS-54 digital TDMA cellular standard, and the US IS-95 CDMA standard. All of the above systems are characterized in that the speech is first converted...

Claims

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Application Information

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IPC IPC(8): H04L27/00H04B1/04H04B1/707H04L25/03H04L27/20
CPCH04L25/03834H04B1/7097H04L27/2017H04L27/2064Y02D30/70H04L25/03
Inventor P·W·登特
Owner UNWIRED PLANET
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