III. Gm-C Filtering - Epublications - Université de Limoges
III. Gm-C Filtering - Epublications - Université de Limoges
III. Gm-C Filtering - Epublications - Université de Limoges
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I.4 Technological Trend of RF Selectivity<br />
I.4.a RF filtering integration history<br />
Since the beginning of TV, TV tuners have known several technological evolutions.<br />
Up to the years 2000, they were referred as can tuners. [I.10] In<strong>de</strong>ed, they were ma<strong>de</strong> of<br />
active components as well as hundreds of passive external components, mounted together on<br />
a board [I.11]. The whole was encapsulated insi<strong>de</strong> a metal shield enclosure, the can, in or<strong>de</strong>r<br />
to protect the tuner from the electromagnetic fields present in the environment. Furthermore,<br />
these can tuners had an architecture making use of several bandpass filtering stages,<br />
associated to a very selective Surface Acoustic Wave (SAW) filter located in the IF path.<br />
These features strongly immunize can tuners from all kinds of interferers and provi<strong>de</strong> a very<br />
important adjacent filtering before the LNA. As illustrated in Figure 34, RF filtering was<br />
handled by means of several air coils, manually tuned, in parallel of high voltage varicaps.<br />
Figure 34. Can tuner (a) and its RF filtering (b)<br />
In 2007, first silicon tuners were <strong>de</strong>signed, like the NXP TDA 18271 (see Figure 35).<br />
As explained in [I.10], the <strong>de</strong>velopment lag of TV tuners behind all other TV <strong>de</strong>velopments<br />
highlights that silicon tuners have difficult challenges to overcome. This major technological<br />
step allowed the emergence of new functionalities and applications. In<strong>de</strong>ed, a silicon tuner has<br />
become multi-standard while can tuners were aimed at receiving only one single standard. In<br />
addition, silicon tuners show higher integration, lower power consumption, better thermal<br />
behaviour and better reliability. The emergence of multiple tuners integrated on a same chip<br />
also allows digital vi<strong>de</strong>o recording or picture-in-picture applications. [I.12]<br />
Silicon tuners integrate almost all TV tuner functions on silicon. However, RF filtering<br />
was still handled by discrete inductors in parallel of discrete varactors. The whole was<br />
integrated within a package as it may be seen in Figure 35 [I.13].<br />
Figure 35. NXP TDA18271 (a) and its RF filtering (b)<br />
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