John’s list of interesting radio patents
Radio Patents relating to signal propagation along a wire
- Interference attenuating power conductor utilizing intensified skin effect to attenuate high frequencies
- US3219951, 3 May 1963
Radio Patents relating to mitigating Passive Intermodulation (PIM) products in ferromagnetic materials
The next two patents describe a technique whereby passing a strong static magnetic field through a PIM prone ferrous material, such as a nickel plated RF connector, reduces the generation of PIM. This technique is likely in the public domain by now, but the recent Purdue patent application is an interesting read nonetheless.
- Method of reducing spurious signal generation in passive microwave components
- US4156857, 2 May 1977
- This patent showcases prior art to the patent application US20120139656 below. It doesn’t patent the method of using a magnetic field to mitigate PIM in ferrous materials specifically, but does describe the method in its descriptive wording as if it is common knowledge.
- Magnetic field system and method for mitigating passive intermodulation distortion
- US20120139656, Application 4 Jun 2009 – Purdue University IDEAS Lab
- This patent application’s first claim describes a method that seems to already exist in Prior Art above.
The folks at Purdue have a spiffy video demonstrating the effect…