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About adding a RF switch on the balun for CC2540

TS
Prodigy 20 points
Other Parts Discussed in Thread: CC2540

Dear All,

I found the post on the website(
e2e.ti.com/.../231315) that is relevant to my problem.

I would like to add a RF switch(PE4259, www.psemi.com/.../pe4259) on the pin1 of a balun (2450BM15A0002, www.ti.com/.../swra297b.pdf) of CC2540. As I am new to impedance matching and EM simulation, I do not know whether I need to add the matching network between the pin1 of balun and the extra RF switch? and between RF switch to chip antenna(www.johansontechnology.com/.../2450AT42A100_v2.pdf)? and how to make it ? Is there any reference design regarding adding RF switch with keeping the same Tx and Rx power efficiency?

I find the note in the post and think it is a good start to learn from scratch. First, I try to do ADS simulation on the first part of the note about differential matching network. As I do not how to fill MLIN microstrip model (W or L), I short it. I keep default values of Q= 50, Rdc=0 Ohm for INDQ and default values of R=1 Ohm, L=1nH for SRLC. The S11 (on the match common point of C252 and L261) of -18 dB occurs by 2.8nH and 0.8pF rather than 2.2nH and 0.8pF in the post. How do I correct my simulation result to meet the results in the post ?

Best Regards,

TS

  • 0
    TI__Mastermind 18780 points

    The balun you are reffering to has an 50 ohm ubal output, so if you choose a switch with a 50 ohm input (which they normally have) you will not need any matching components between the switch and balun, and thus no simulations to optimize performance. The losses in TX and RX will then be given by the insertion loss in the switch. And for the chip antenna and antenna matching, I recommend that you take a look at AN058 www.ti.com/.../swra161b.pdf and also discuss with the chip antenna producer. Add place holders for a series and a shunt comp before the antenna, or even better a shunt, series and shunt comp between the antenna and switch if you will need to match the antenna at a later point.

  • 0 in reply to CHS
    Expert 1445 points
    TS,

    I replied to the email you sent me. See that for your questions regarding the ADS simulation. For the benefit of others though, RF components need to be modeled very accurately as frequencies increase. You can use MFG information to model inductors, capacitors, etc if you want (as I did). But, if your college or company has Modelitics RF component models (http://www.modelithics.com/) then use those instead. If you use GENESYS to simulate your circuits, Modelithics has a special promotion now and you can use their complete library for 6 months at no cost. You can probably get a demo for ADS as well. They also have Microwave Office models.

    Regards,

    Eric Hooker
    RF Consultant