Although applicable in principle to any radio frequency signal generating apparatus, the present invention and its underlying problem will be hereinafter described in combination with testing a wireless communication system. 
The use of wireless communication systems increases continuously with the advance of high speed wireless data communications.  During development and production of devices for communication systems it is necessary to thoroughly test devices for compliance with communication standards.  For this purpose, tests may be applied over an increasing frequency range.  Thus, testing modern communication systems may require broadband test signals extending over an increasing frequency range.  However, generating such broadband test signals with a wide bandwidth may be a big challenge.  In particular, the generation of such signals may require complex and expensive components. 
Against this background, a problem addressed by the present invention is to provide an improved and versatile generation of broadband signals.  In particular, the present invention aims to provide radio frequency signals with a baseband signal extending over a wide frequency range.