In a method of forming a device so as to include a reflective surface at a specific angle to an incident optical axis, a region of a first major surface of a substrate is exposed to an anisotropic etchant to form a surface having the specific angle with respect to the first major surface, but the etched surface is then used as a mounting surface. Numerous other aspects are provided. A non-linear replica signal of non-linear transmission signal components that are created in the transceiver by a transmit signal DAC, and imposed onto the receive signal, is generated. The covering also includes a series of parallel binder threads for attaching the first layer to the second layer. Either the second device is arranged to perform a function based on its location other than providing its location as an estimate of the location of the first device, or the location of the second device is provided to the first device using a wireless communications link. The active trench can include a second shield electrode made of conductive material disposed below the first shield electrode.