who can tell me some hot topics in rf ic design?

design linear PA with high efficiency
duplex filter are extremely big and bulky, come up with a scheme to shrink it

why linear PA? Doesn't polar transmitter technique handle this? Lots of modulation techniques such as GSM use phase but not envelop, so isn't nonlinear PA enough?

nonlinear PA is the problem, it's the nonlinearity that makes it more complex and expensive to build. More than often that nonlinearity will broaden your spectrum and thus causing problems. Sure there are tricks to reduces it but adding those tricks to your mobile device requires +++ ckts = increase cost of power and SSS to build

till now , the PA's in the market are done in GaAs , or InP , only Silabs has the Si PA ,
u can work in PA , till now linear PA with high effeciny is required

khouly