Recent stipulations surrounding the unpatentability of signal claims in Canada continue to create a need for improved guidelines.

The patent community continues to react to the statement of the Canadian Patent Office last August that claims to signals per se are not patentable because they are not “inventions”.16 Section 2 of the Patent Act defines “invention” to mean any new and useful “art”, “process”, “machine”, “manufacture” or “composition of matter”, or any improvement thereof.17 To be patentable, an invention must fall within one of these enumerated categories.18

The Canadian Patent Office concluded that claims to signals (e.g. electromagnetic and acoustic signals) do not meet this test. Specifically, a signal is not an "art" or a "process" because it is not an act or method of operation that results in a physical or chemical action. Furthermore, a signal is not a "machine" since it is not a mechanical embodiment of a function designed to accomplish a particular effect. Moreover, a signal is not a "composition of matter" since it is not a chemical compound or substance. Finally, a signal is not a "manufacture" since it is not a material product.

There is uncertainty about the accuracy of this position. For example, the Patent Act contains no explicit reference to "material products", and it is possible that signals could be considered to fall within the invention definition under "manufacture". Similarly, there is debate as to scope of the meaning of "composition of matter" that may leave the issue open to be challenged. The position also seems to conflict with the Manual of Patent Office Practice, which has yet to be updated, and lists a claim to a carrier wave (i.e. a transmission signal that can be encoded with information) as an acceptable claim.19

It is worth highlighting that this change is limited to the signals themselves, and does not apply to methods, apparatuses or other inventions related to signals that fall within the enumerated grounds. For example, a claim to "A method of generating an electromagnetic signal…" is not affected by this change.

The patentability of signal claims also continues to be debated in the United States with similar results. The United States Patent Office issued guidelines in 2005 stating that signal claims were not patentable.20 More recently, the U.S. Court of Appeals for Federal Circuit concluded in a split decision that signal claims related to digital watermarking were not patentable in part because of their transitory nature.21