A constellation diagram plots a quadrature amplitude modulation (QAM) signal’s in-phase and quadrature components. The EE World article “Should I use a spectrum, signal, or vector network analyzer?” in part 3 mentioned that vector-signal analyzers (VSAs) can display modulation-domain and frequency-domain information. Other instruments incorporating digital signal processing (DSP) capabilities, including oscilloscopes, can provide insights into […]
Should I use a spectrum analyzer, signal analyzer, or vector network analyzer? Part 4
A vector network analyzer can fully characterize components by deriving their scattering parameters. In earlier parts of this series, we looked at analog spectrum analyzers (part 1 and part 2) and vector signal analyzers (part 3), both of which monitor unknown signals, whether emanating from a system, device under test (DUT), or an enemy’s transmitter […]
Should I use a spectrum, signal, or vector network analyzer? part 3
In part 2 of this series, we looked at a swept-tuned spectrum analyzer and how it could sweep a frequency span of interest from 1 MHz to 1.1 MHz with a sweep time of 50 msec. As Figure 1 shows, the analyzer readily identifies a signal at 1.03 MHz but misses the intermittent signals shown […]
Should I use a spectrum, signal, or vector network analyzer? part 2
An analog spectrum analyzer’s sweep time can hide intermittent unwanted signals. In part 1 of this series, we examined a simplified block diagram of a traditional analog spectrum analyzer, which includes an RF frontend, mixer, voltage-controlled oscillator (VCO), intermediate-frequency (IF) stage, sweep generator, envelope detector, and display. We also looked at resolution bandwidth (RBW), the […]
Should I use a spectrum, signal, or vector network analyzer? part 1
Signal analysis is invaluable for applications ranging from amplifier characterization to signal intelligence. In a recent series, we discussed specs such as 1-dB compression and third-order intercept points. At the end, I pointed to some application notes that explain how to use specific spectrum, signal, and vector network analyzers to make these measurements. These instruments’ […]
How can I quantify a device’s nonlinearity? part 3
A higher third-order intercept point results in lower intermodulation products at any given input power level below compression. In part 1 of this series, we discussed the 1-dB compression point as a figure of merit for device linearity. In part 2, we examined a circuit that adds two fundamental input signals of frequencies f1 = […]
How can I quantify a device’s nonlinearity? part 2
A figure of merit called the third-order intercept point indicates how well an RF device minimizes third-order intermodulation products. In part 1, we looked at the 1-dB compression point, which serves as a figure of merit for devices such as RF power amplifiers. An additional specification, the third-order intercept point, abbreviated IP3 or TOI, is […]
How can I quantify a device’s nonlinearity? part 1
You can specify nonlinearity in parts per million or, especially for RF components, in terms of the 1-dB compression point or third-order intercept point.
What is intermodulation, and is it good or bad? part 4
Nonlinearities in active circuits and passive components can add harmonic and nonharmonic distortion. This series has investigated intermodulation, the process by which the application of two frequencies to a nonlinear system results in the system generating frequencies that equal the sum and difference of the input frequencies. In Part 1 and Part 2, we looked […]
What is intermodulation, and is it good or bad? part 3
Excel’s charting function adds nonharmonic frequency components to a cosine wave. In Part 1 and Part 2 of this series, we looked at intermodulation — what it is and how to apply it to frequency-translation tasks. We concluded Part 2 with an image like Figure 1. We had begun with a 1,200-kHz carrier with two […]
