Non-linear transmission line device

A microwave frequency oscillator for producing an RF signal, said microwave frequency oscillator comprising:

• a non-linear transmission line containing at least one element of magnetic material having in use a magnetic bias field along a given axis, wherein:
• said magnetic element has opposed end regions spaced along said axis, and at least one of said end regions is profiled to at least reduce demagnetisation of said material in said end region;
• said magnetic element is of hollow cylindrical form, and at least one end region thereof is externally tapered, with wall thickness of the magnetic element decreasing towards a free end thereof;
• and
• said magnetic element has a height, width, and length, and the height and width are each less than 10% of the length;
• an input for applying an input signal to the transmission line for being modulated thereby;
• an output for the modulated signal;
• and
• a coaxial electrical conductor arrangement, with a first electrically conducting element passing through the hollow part of the magnetic element, and a concentric conductor element surrounding and spaced from said magnetic element, the coaxial conductor arrangement being adapted in use to receive an input pulse at one end and to deliver an output signal at another end, wherein the end of the magnetic element proximate said output end is externally tapered.