Testing Broadband CATV Amplifiers
Application Notes
Simple test system saves time and enhances amplifier characterization
Since the mid-1990s, cable access television (CATV) providers have been pushing to offer more services and greater bandwidth. Within any such CATV system, bidirectional broadband amplifiers are the key to carrying high quality video and audio signals to and from every subscriber.
A typical CATV amplifier provides the following functions:
– Supports multi-channel transmission by amplifying signals over a wide bandwidth
– Ensures signal quality by minimizing distortion and frequency fluctuation
– Provides variable gain to compensate for changing conditions
These amplifiers must be capable of handling both analog and digital signals. For digital signals that carry complex modulation schemes, the key measures of signal quality are either error vector magnitude (EVM) or the closely related modulation error ratio (MER)1. The most efficient way to measure amplifier EVM or MER is to apply a complex wideband signal and measure the resulting output with a signal analyzer and vector signal analysis (VSA) software. Creating highly realistic input signals requires the use of an arbitrary waveform generator (AWG) such as the 12 GSa/s Keysight Technologies, Inc. M8190A.