Array for wired testing of multi-input and multi-output signals

An electronic device, comprising:

• N input connectors;
• M output connectors, wherein N and M are non-zero integers and M is greater than N;
• and
• phase-shift elements configured to provide predefined phases between the N input connectors and the M output connectors, wherein the electronic device is configured to provide a modified Butler matrix in which:
• N input electrical signals provided to the N input connectors result in N output electrical signals corresponding to the N input electrical signals on N of the M output connectors, wherein the N output electrical signals are orthogonal to each other;
• and
• the N input electrical signals result in P output electrical signals corresponding to the N input electrical signals on P of the M output connectors, wherein the P output electrical signals are orthogonal to each other, but are not orthogonal to the N output electrical signals, wherein P is a non-zero integer, wherein the P output electrical signals are linear combinations of the N input electrical signals in which the N input electrical signals have corresponding second phases, and wherein a dot product of a given one of the N output electrical signals with a given one of the P output electrical signals equals a non-zero predefined value.