Reconfigurable Signal Generator and Simulator for Testing the Digital Transmission Circuits

In this article is presented the implementation of a new type of reconfigurable signal generator and simulator used for testing digital transmission circuits that requires complex modulated waveforms. In our experiments we choose as an example the quadrature amplitude modulation or quadrature phase shift keying (QAM/QPSK) signals. The proposed solution is based on a high-speed NI-USB-6251M data acquisition board connected to a computer running a LabVIEW application. The analog outputs of the board are used for applying the predefined test signals to the circuits that are under test. The response of the tested circuit is monitored using the inputs of the data acquisition board. The novelty of the proposed system is given by the association between a very flexible and user friendly graphical programming environment such as LabVIEW and a general purpose data acquisition board which lead to an attractive implementation solution for a virtual instrument capable to simulate, generate, and also test a multitude of circuits using various signals. Compared with the classical approaches, the system presented in this paper represents a versatile platform, with large spectrum of applications because, with proper configuration of the software application, can be generated a broad range of modulated signals, including arbitrary waveforms, the only limitation being the speed of the data acquisition/generation module.