wide band on chip slab transformer, is it possible?

Hi,

I read from some artical, the CMOS on chip slab transformer can already achieve very high passive efficiency(80%) at 2.4 GHz. (Aoki I, DAT)

Can anyone tell me, is it easy to enhance the bandwidth of the transformer to e.g. 200 MHz-2 GHz?

I haven't done any EM simulation yet. If it is easy, I will have a try.

Thanks!