The 8981A Vector Modulation Analyzer includes a calibrated baseband analyzer which connects to the I and Q outputs of your receiver's demodulator and adds a vector demodulator for IF measurements as well. It connects to the IF output of your transmitter and to the coherent reference. It measures signal magnitude and phase of standard digital communication and radar signals. The instrument performs constellation analysis of quadrature error, lock angle error and closure. The design provides for quick, visual, intuitive measurements as well as giving quantitative data about a signal's modulation. These features allow a user to quickly identify problem sources and measure their magnitude