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Active low-pass filter

A low-pass filter, filter technology, applied in the direction of single-port active network, impedance network, analog negative resistance network, etc., can solve the deterioration of insertion loss, insertion loss and selectivity reduction, reduce the quality factor of inductors, etc. problem, to achieve the effect of reducing cost and power consumption

Inactive Publication Date: 2009-11-18
THOMSON LICENSING SA
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  • Description
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AI Technical Summary

Problems solved by technology

[0014]In fact, if parasitic elements are considered, the insertion loss is severely worsened in the neighborhood of FC
This reduction is mainly due to the parasitic series resistance of the inductor (typically around 1 ohm for wound SMC inductors), which reduces the quality factor of the inductor and results in an increase in insertion loss and selectivity. aspect degrades the performance of the filter

Method used

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Embodiment Construction

[0035] In order to simplify the description, the same reference numerals will be used in these subsequent figures to refer to elements performing the same function.

[0036] The most critical parasitic resistances are those of the inductor Lr, which allow to generate close to F C The transmission zero of , more specifically, Lr1 connected in series with Cr1 produces the closest F C The transmission zeros of , as already stated previously.

[0037] The design proposed here is based on the use of active filtering techniques, which, due to a pseudo-elliptic low-pass type response, allow the suppression of the transmitted unwanted GSM frequency band and thus the entire DVB frequency band from 470 to 862 MHz from potential interference .

[0038] An active filter is defined as a filter comprising active components such as mainly transistors. It is clear that active filters have higher performance in terms of insertion loss and selectivity to be achieved compared to passive filte...

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Abstract

The invention relates to a selective active low-pass filter and to a method for improving the selectivity of such a filter. The method consists in centring, in the centre of the network, the resonant element whose frequency is closest to the cut-off frequency of the filter and in inserting in series with this element a negative resistance of higher value than the parasitic resistance of the filter.

Description

technical field [0001] The present invention relates to a selective active low pass filter and a method for improving the selectivity of an active low pass filter. It falls under the framework of the Multi-Radio-Front-End (MRFE, Multi-Radio-Front-End) project for the design of multi-mode, multi-standard fixed / mobile terminals that integrate systems such as cellular telephones (GSM, UMTS, etc.) , terrestrial digital television receiver (DVB-H / T) systems and systems for accessing local networks (WLAN a / b / g). Background technique [0002] From a technical point of view, the concentration of various access modes into a single communication object involves problems of coexistence especially due to the proximity of the operating frequency bands of each mode. [0003] The present invention is specifically concerned with the coexistence of DVB-H / T and GSM standards, such as figure 1 As shown, it is clear that the GSM signal transmitted in the frequency band 890-915 MHz will undoub...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): H03H7/03H03H7/12
CPCH03H11/52H03H7/1758H03H7/03H03H7/0115Y10T29/49002H03H7/12
Inventor 多米尼克·洛海因唐弗朗索瓦·巴伦拉法特·拉巴比迪阿里·洛齐尔
Owner THOMSON LICENSING SA
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