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yousuf

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Impedance Matching Portable Digital TV tuner Large Inductance
Oct 11^th, 2010, 11:06am

Hi,

I was wondering how to design the integrated Impedance matching network for Portable DTV tuner (400MHz to 900MHz) (Inductors in micro Henry range), without using large inductors.

Some possible solutions maybe the use of active inductors. But I just want to use passive devices for matching.

How do they incorporate large inductors in portable or mobile devices for DTV tuning?

Regards

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rfmagic Community Member Offline Posts: 64	Re: Impedance Matching Portable Digital TV tuner Large Inductance Reply #1 - Oct 12^th, 2010, 2:02am what is the LNA topology used in your design? what is the reauired NF for your receiver? I asking that because you can consider using a CG input stage which does not require any inductors in the matching network
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aaron_do

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Re: Impedance Matching Portable Digital TV tuner Large Inductance
Reply #2 - Oct 12^th, 2010, 9:30pm

Hi,

Is this for the input stage? I don't think you would want to use active inductors, since they will add noise directly to the input. You can also forget about integrated inductors since as you say they are too large. For such low frequency you probably have to use common-gate, resistive shunt-feedback, or simply an off-chip matching network.

cheers,
Aaron

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yousuf

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Re: Impedance Matching Portable Digital TV tuner Large Inductance
Reply #3 - Oct 12^th, 2010, 11:12pm

Actually its a variable gain amplifier. So since its the middle block of the receiver, its NF, Linearity are not great concern to me. Only its resolution or gain step

I am just considering putting a resistor parallel to the input that will I guess give me my impedance match.

I was only wondering how do they get portable Digital TV tuners like the ones they use in mobile phones to be so miniaturized without using any external bulky inductors in the design.

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aaron_do Senior Fellow Offline Posts: 1398	Re: Impedance Matching Portable Digital TV tuner Large Inductance Reply #4 - Oct 13^th, 2010, 12:10am Hi, I don't have any experience in that area, but for your own design, you can terminate with a resistor as you say, but why do you need impedance matching in the first place? Is this VGA to be a chip on its own? regards, Aaron
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pancho_hideboo

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Re: Impedance Matching Portable Digital TV tuner Large Inductance
Reply #5 - Oct 13^th, 2010, 9:36am

yousuf wrote on Oct 11^th, 2010, 11:06am:

I was wondering how to design the integrated Impedance matching network for Portable DTV tuner (400MHz to 900MHz) (Inductors in micro Henry range), without using large inductors.

See http://www.designers-guide.org/Forum/YaBB.pl?num=1207009725/2#2

Usually common-gate stage or common-base stage is used.

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rfcooltools.com

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Re: Impedance Matching Portable Digital TV tuner Large Inductance
Reply #6 - Oct 19^th, 2010, 10:12am

Yousuf,

At 400-900MHz matching inductors will probably only need to be in the 1's to 10's of nH's depending on the value of inductor needed you can make some fairly good inductors on chip or even higher Q ones on the pcb board.

I have a crazy idea why don't you post your circuit 2-port unmatched s-parameters on this site and we can have a small contest to see who can match it with the most area effective match?

http://rfcooltools.com

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