INTRODUCTION

When simulating a complete subsystem such as a wireless communication device or radar receiver, the quality of measurement data becomes essential to ensure that the fi nished product meets or exceeds the demands the system will encounter in service. The measurement data can be used to make changes to the system early in the design process, when those changes can be realized in the least amount of time and at the lowest cost. However, this can be accomplished only if there is a direct link between the system being simulated and the measurement equipment itself—that is, when there is “hardware in the loop.”AWR’s Visual System Simulator™ (VSS) combined with its TestWave™ software provides an end-to-end communications system simulation environment that makes this possible.

The TestWave software physically connects VSS to actual test and measurement equipment through VISA, GPIB, LAN, or RS-232 connections. This level of integration enables system simulation, test signal generation, and measurement verifi cation to become an integral part of the entire design fl ow process. Designers can perform trade-off studies to optimize a circuit using data obtained from actual test equipment. The VSS/TestWave user interface imports signals, manages data, and directly controls the test equipment, sending commands and receiving responses. During the simulation, the block confi gures the test equipment, passes variables to the instruments, and takes measurement data from the instruments for use in the analysis.

For example, a baseband I/Q waveform data generated by a transmitter with VSS software can be sent to an external vector signal generator to stimulate a device used in the circuit. The output of the device can then be passed to a vector signal analyzer and the results compared with those in the VSS simulation. Using these results as a guide, values of the device or other elements of the circuit can be modifi ed to achieve a specifi c level of performance. The signals from the device under test can also be sent back into the VSS simulation as a stimulus to determine how they affect performance.