RF is known to be quite challenging, but what makes it so challenging? There are external influences, which originate outside the product’s design, such as other transmitters on the same frequency. There are internal influences that originate within the design itself, such as crystals, high speed logic, or switching power supplies. There are design issues, such as a parasitic reactance, coupling, and matching. The equipment required for RF design, including signal generators, spectrum analyzers, and network analyzers, can cost tens of thousands of dollars each. Engineers who are trained to do RF design and deal with the challenges are specialized. Finally, there are the legal issues associated with wireless devices. Different countries have different legal regulations for wireless communication. All of these challenges present a significant burden for entry into wireless design. RF modules can bypass most of these challenges, offering a much lower cost and much faster time to market.