A spectrum analyzer measures the magnitude of an input signal versus its frequency over the full frequency range of the instrument to determine the power of signals. Spectrum analyzers enable tests like noise figure and signal-to-noise ratio (SNR) to characterize the performance of a device and its contribution to overall system performance. For more information, refer to this Spectrum Analysis Basics application note for more information.

A signal analyzer measures both the magnitude and phase of an input signal at a single frequency. A signal analyzer combines the superior dynamic range of a swept tuned spectrum analyzer with vector signal analyzer (VSA) capabilities and enables in-channel measurements like error vector magnitude (EVM) that requires both magnitude and phase information.

Spectrum analyzers are used in a wide range of applications across various industries. Spectrum analyzers are important for analyzing and characterizing radio frequency (RF) signals in wireless communication systems, including Wi-Fi and cellular networks. Other applications include electronic design and testing, broadcasting and telecommunications, and aerospace and defense.

Spectrum analyzers measure the magnitude of an input signal versus signal frequency. Signal analyzers measure both the magnitude and phase of an input signal at a single frequency. Refer to this Spectrum Analyzer and Signal Analyzer technical overview for more information.

Our normal frame of reference is time. We note when certain events occur. This includes electrical events. An oscilloscope enables you to view the instantaneous value of a particular electrical event (or some other event converted to volts through an appropriate transducer) as a function of time. In other words, we use the oscilloscope to view the waveform of a signal in the time domain. Fourier theory tells us any time-domain electrical phenomenon consists of one or more sine waves of appropriate frequency, amplitude, and phase. In other words, it is possible to transform a time-domain signal into its frequency-domain equivalent. Spectrum analyzers and signal analyzers perform measurements in the frequency domain to measure energy at each particular frequency.

A complex signal in the time domain looks vastly different than in the frequency domain. The time-domain measurement shows an impure sine wave. Without measuring in the frequency domain, the source and frequency of the second harmonic remain unknown. A spectrum analyzer uncovers sources of interference by displaying the spectral components independently. The time-domain still provides useful information, such as the pulse rise and fall times of a signal, but the frequency domain allows you to determine the harmonic content of a signal, such as out-of-band emissions and distortion. For more information refer to this blog: Spectrum Analysis Basics, Part 1 – What is a Spectrum Analyzer?

A real-time spectrum analyzer first gathers data in the time domain and then translates it into the frequency domain by means of the Fast Fourier Transform (FFT). A real-time spectrum analyzer captures transient and fast signals quickly.

There are two broad categories of spectrum analyzers: swept-tuned analyzers and real-time analyzers. Modern spectrum analyzers use digital signal processing to provide additional measurement capability and let you interpret measurement results much more easily. Both swept-tuned and real-time spectrum analyzers display amplitude versus frequency. How they process and display this information, however, varies with the specific type of analyzer. A real-time spectrum analyzer displays the energy at all frequency components simultaneously. A swept-tuned spectrum analyzer displays measurement results sequentially, in other words, not in ''real-time''. This is because a swept-tuned analyzer uses a single narrow filter that is tuned across a range of frequencies to produce a spectrum display. Learn more about the different types of spectrum analyzers here.

Keysight’s U9361 RCal receiver calibrator enables you to perform an accurate and reliable calibration for your spectrum analyzer / signal analyzers using the following steps:

1. Connect the RCal to your signal analyzer via a high-power USB port.
2. Connect the signal analyzer’s 10 MHz reference signal to the U9361 RCal’s Reference In port.
3. Set the RCal options reference status as EXT (external).
4. Connect RCal’s RF Out to RF In of the signal analyzer.
5. The Keysight signal analyzer preconfigures the interface. The screen displays type of calibration, frequency range, attenuation range, and number of points.
6. Connect the RCal’s RF Out to the point in the path where the device under test (DUT) is when you take your actual measurements.
7. Click on “Calibrate checked rows” to initiate the receiver calibrator and the signal analyzer to generate correction data.
8. Disconnect the RCal and reconnect the signal path. This action moves the measurement plane. The X-Series signal analyzer dynamically tracks your measurements and only applies corrections to the states where needed.

Read more about How to Calibrate a Spectrum Analyzer.