shlomo22
Member level 4
transformer coupling
You can define a coupling coefficient for a transformer:
K=M/sqrt(L1*L2)
where M is the mutual inductance and L1,L2 the inductance of each coil.
My experience with RF-CMOS transformers is that M and thus K increase as frequency increases, but L1 and L2 are constant (below the self resonant frequency of course). I have seen similar results for other people's transformers in published papers.
I cannot think of any physical explanation why M would increase while the individual inductance does not.
Constant individual inductance presumably indicates that the electromagnetic field pattern is not changing, but changing mutual inductance indicates that the fields are changing... no?
Anyone have an explanation?
You can define a coupling coefficient for a transformer:
K=M/sqrt(L1*L2)
where M is the mutual inductance and L1,L2 the inductance of each coil.
My experience with RF-CMOS transformers is that M and thus K increase as frequency increases, but L1 and L2 are constant (below the self resonant frequency of course). I have seen similar results for other people's transformers in published papers.
I cannot think of any physical explanation why M would increase while the individual inductance does not.
Constant individual inductance presumably indicates that the electromagnetic field pattern is not changing, but changing mutual inductance indicates that the fields are changing... no?
Anyone have an explanation?