How to increase the field strength of RF amplifier?

[sjx01]

RF Amplifier

I'm a freshie in the RF field.
My antenna's field strenght is insufficient for some of the card so I plan to add in an amplifier to the design. Theproblem I'm facing now is I do not know how to increase the field strenght without introduce the noise, phase shifted and losses into the signal? Is there any reference design i can refer or any advices for me from the expert in this Forum?

thanks.

 

[Borber]

Re: RF Amplifier

What card you are talking about. Does it communicate to the world two ways or it is only a transmitter.

 

[sjx01]

Re: RF Amplifier

There are some type B (ISO14443) contactless card which need higher field strenght to work.
It's two way communication. half duplex.

Thanks.

 

[dsjomo]

RF Amplifier

There is little chance to build LNA or RF Amp on Type B PICC card because their large power consumption.

 

[Borber]

Re: RF Amplifier

The only way to use LNA or TX Amplifier is to connect it before duplexer circuit. It can not be connected directly to antenna because duplex communication. Use antenna with higher gain.

 

[sjx01]

Re: RF Amplifier

Is that posisble that I add the amplifier on the TX pin before the receiver part? How to add the amplifier in without affect the matching circuit?
I can't use Higher gain antenna is because it will increase the Q factor which will trade off transmission speed.

 

[springf2000]

Re: RF Amplifier

like the satellite receiver,add a LNA after the antenna

 

[thisnot]

Re: RF Amplifier

razavi has a great book on rf design. its used in many classes so you can probably find a lot of lectures online.

 

[sjx01]

Re: RF Amplifier

Thanks. I'll try to get them online. :wink: