lambda/12 Transmission line at higher frequencies

Hi,

Can I use lamda/12 length transmission line while designing matching circuits for high frequencies.

When I calculate the length of transmission line using c/f I get 49mm. Can I use 5mm 0r 4mm transmission line.

Regards,
Praveen

Sure - you can use whatever lengths you like (provided the circuit parasitics don't swamp whatever effect you're trying to achieve with lengths of transmission line). There's nothing magical, prescribed or fixed about your choice of line lengths :)
ANY length of transmission line will perform an impedance transformation (provided the load impedance differs from the line impedance) that can be exploited.