CHANNEL FILTER, IN PARTICULAR FOR A DIGITAL TELEVISION RECEIVER

• US 20100134700A1
• Filed: 06/24/2008
• Published: 06/03/2010
• Est. Priority Date: 06/28/2007
• Status: Active Grant

• Current Assignee: Thomson Licensing (Vantiva SA)
• Original Assignee: Thomson Licensing (Vantiva SA)
• Inventors: Lababidi, Raafat, Lo Hine Tong, Dominique, Robert, Jean-Luc
• Granted Patent: US 8,390,745 B2
• Time in Patent Office: Days
• US Class Current: 348/731
• CPC Class Codes: H03H 7/01 Frequency selective two-port networks
• CPC Class Codes: H04B 1/1027 assessing signal quality or detecting noise/interference for the received signal
• CPC Class Codes: H04L 25/03012 operating in the time domain H04L25/03165, H04L25/03178 take precedence
• CPC Class Codes: H04L 25/03133 with a non-recursive structure H04L25/03127 takes precedence

Abstract

The channel filter includes at a least one basic bandpass filter centred on the frequency of the channel, in series with two cascade-connected reflective filters whose bandwidths are located either side of the basic bandpass filter encompassing the channels adjacent to the channel. A reflective filter can include a 90° directional coupler combined with a bandpass filter designed to ensure transfer matched to the load impedance of the coupler with the input of the bandpass filter connected to a directional coupler output port, the input of the directive filter being formed by input port of the coupler and the output of the directive filter being formed by a port recovering the bandpass filter reflection coefficient. The invention applies in particular to the implementation of the DVB-T and DVB-H standards aimed at receiving digital television programmes from fixed or mobile multistandard terminals such as mobile telephones, PDAs or other multimedia receivers.

Claims

1. A channel filter wherein it includes at least one basic bandpass filter, centred on the frequency of channel N, in series with two reflective filters cascade-connected and whose bandwidths are located either side of the frequency of channel N and encompass at least the frequencies of the channels of adjacent to channel N.

2. A channel filter according to claim 1, wherein a reflective filter includes a 90°

directional coupler loaded by a bandpass filter designed to ensure transfer matched to the load impedance of the coupler with the input of the bandpass filter connected to a directional coupler output port, the input of the reflective filter being formed by input port of the coupler and the output of the reflective filter being formed by a port recovering the bandpass filter reflection coefficient.

3. A filter according to claim 1, centred on the frequency of channel N, the bandwidth of a first bandpass filter occupying the bands of channels N−

1 to N−

3, while being centred on the intermediate frequency of channel N−

2, with the bandwidth of the second bandpass filter occupying the bands of channels N+1 to N+3, while being centred on the intermediate frequency of channel N+2.

4. A filter according to claim 1 wherein an amplifier is placed between two reflective filters to compensate for losses due to these filters.

5. A filter according to claim 1 wherein the bandpass filters are of the Tchebychev 5 pole types.

6. A filter according to claim 1 wherein it is used in a digital television receiver.

7. A filter according to claim 6 wherein it includes a microprocessor equipped with an analogue-digital converter to seek an optimum of the carrier-to-noise C/N ratio supplied by DVB demodulator of the receiver connected to the output of said filter with searching carried out by working alternately on the poles of the bandpass filters.

8. A filter according to claim 1 wherein basic bandpass filter is a Surface Acoustic Wave filter.