Patexia is looking for descriptions of a radio frequency modulation method that improves the multipath performance by modifying the orthogonal codes used as symbols with a complementary code.

This complementary code is specifically designed to:

• reduce the autocorrelation sidelobes of a symbol by at least one-half the symbol length
• while maintaining the cross-correlation properties of the symbol.

Submitted documents describing this system must be:

• filed or published before 07/30/1996
• not on the known references list

When a radio signal is transmitted, the path between sender to receiver is a mix of different paths: some a direct line, others a mixture of different paths as the signal is scattered and reflected across a number of physical objects. This scattering and reflection can cause signal delays that make decoding the data more difficult. Fixing this is called optimizing the multipath performance.

The entire submission should describe a method of improving multipath performance by:

• using data symbols that are made from (1) an orthogonal code that is modified with (2) a complementary code
• the data symbols’ autocorrelation sidelobes should be equal or less than one-half the symbols’ length respectively
• the orthogonal code should be a Walsh code
• the complementary code should be derived via the equation below
• each modified code’s length (in number of chips or data bits) should be less than the number of available modified codes (i.e. for M number of modified codes, each with N chips, M N)

c = {ei(Φ1+Φ2+Φ3+Φ4), ei(Φ1+Φ3+Φ4), ei(Φ1+Φ2+Φ4), −ei(Φ1+Φ4), ei(Φ1+Φ2+Φ3), ei(Φ1+Φ3), −ei(Φ1+Φ2), eiΦ1}
Equation for a complementary code, where c is the complementary code, and Φi is the phase angles of the code bits.

This contest is for a prior art search for US Patent 7,583,582, with a focus on independent claims 1, 2, 4, and 14.

Contest icon by Matt Wasser from The Noun Project.