A new Binary Number Code and a Multiplier, based on 3 as semi-primitive root of 1 mod 2^k

The powers of 3 generate half of the odd residues mod 2^k (k>2), and a sign change yields the other half. In other words: 3 is a semi-primitive root of 1 mod 2^k (k>2). Hence each k-bit residue is n = +/- 3^i.2^j mod 2^k, with unique non-neg exponent pair: i