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Design >> RF Design >> multistandard lna
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Message started by chris2312 on Jul 7^th, 2011, 3:33am

Title: multistandard lna
Post by chris2312 on Jul 7^th, 2011, 3:33am

hello,

I want to design a multistandard LNA for 2.4GHz and 5.8GHz. Does anybody have an idea how I can design a matching network which is broadband and covers the desired frequency range or a network, which only works for theese two frequencies well ? Is there a special literature you can suggest ? Thanks for answers.

Title: Re: multistandard lna
Post by loose-electron on Jul 10^th, 2011, 12:49pm

its not too commonly done due to the optimization at the two frequencies being pretty different. However I know of some places it was tried, with some success.

As with anything multipurpose, you are going to end up with compromises. Consider dedicated LNA's for each band as a possibility.

Title: Re: multistandard lna
Post by chris2312 on Jul 12^th, 2011, 1:29am

Yes I studied some papers about this topic. There are some possibilities to realize it. First, you design a broadband amplifier. Second, you design an amplifier with a switchable matching network and third is you design an amplifier where your matching network works well for two frequencies. In the last case you could not calculate the matching network because the input impedance of the transistor is changing for the two frequencies of interest, so you couldn't calculate it. Has somebody an idea, how i could calculate it ?

Title: Re: multistandard lna
Post by vp1953 on Jul 18^th, 2011, 7:02pm

Hi Chris,

Not too commonly done but these days more and more companies are trying to do this esp. in GaAs. If you google on "dual band LNA" you should find several approaches.

Title: Re: multistandard lna
Post by inductioner on Jul 26^th, 2011, 4:13am

2 ways to do multi-standard frontend :
Either going broadband or narrowband. Broadband design needs very high linearity to handle strong signals. Narrowband design needs multiple LNAs for different bands. In your case, 2.4G/5.8G is too wide band to consider one single narrowband circuit. The compromise is too large to be acceptable.