A spectrum analyzer and a network analyzer are both important pieces of testing equipment and instrument for an engineer. Although they sound similar, however, they pose some major differences. In this article, you will be having a close look at how each device works and what differentiates them from each other.
What is a Spectrum Analyzer?
A spectrum analyzer is testing equipment used to measure the strength of a signal (amplitude) in the frequency domain. The amplitude is measured within the frequency range of the signal, which is also the main purpose of this device and that is to make sure that the desired signal is within the frequency range of our choosing. It also shows us the harmonics, distortion, and bandwidth of a signal which are very difficult to detect in the time domain.
Working of A Spectrum Analyzer
The signal to be evaluated is first fed into the RF attenuator, which then feeds the best signal to the mixer. The mixer combines the input signal with the signal from the local oscillator to produce an intermediate frequency signal.
The signal is then fed into the IF filter, whose output is fed into the detector, allowing the signal to be detected at the tuned frequency. The voltage at the detector’s output indicates the amplitude of the signal and drives the plot’s y-axis.
The frequency response is provided by the synchronization of the sweep generator and the Local Oscillator. This results in the production of amplitude vs frequency plot on the analyzer’s LCD display.
Applications of A Spectrum Analyzer
- To measure amplitude of a signal in the frequency domain
- To measure harmonic distortion for the quality of the signal
- To measure intermodulation distortion
- To measure the frequency of the signal
- To measure Spectral masks
What is A Network Analyzer?
A network analyzer is used to test the network parameters of electrical networks. A network analyzer is used to detect unusual traffic of a network. It is widely used in the radio frequency industry by communication engineers for troubleshooting and designing. A network analyzer provides a detailed capture of which device is communicating and with whom. It can also detect the type of protocol or port being used in the communication.
Working of A Network Analyzer
A network analyzer unit contains both source and receiver signals. Changes in the output signal of a device or a network are detected by receivers when compared to the source signals input to the device. A network analyzer can measure the amplitude and phase responses induced by the device by comparing how the device affects current and voltage. Transmission measurements (transmission coefficient, insertion loss, gain), reflection measurements (reflection coefficient, VSWR, return loss), impedance, and the S parameters are the results.
Applications of A Network Analyzer
- Characterization of a two-port network, such as a filter or an amplifier, by measuring the S, Y & H parameters
- High-frequency measurements
- Sound and Vibration measurements
Key Differences Between Spectrum and Network Analyzer
- The obvious difference between the two as stated before was that a spectrum analyzer measures the characteristic of a signal, meaning it measures signal power, harmonics, sidebands, etc. A network analyzer is used to measure S-parameters, reflection coefficient, insertion, and return losses.
- A network analyzer utilizes vector error correction feature to provide accurate measurements, while a spectrum analyzer does not offer such feature making its readings less accurate.
- Interpreting results in a spectrum analyzer can be very difficult since a lot of noise in the signal can make it difficult for a user to differentiate between a signal and noise. In a network analyzer, it is easier to interpret results.
- A spectrum analyzer only uses frequency sweep for measurement while a network analyzer uses both frequency and power sweep for analysis.
- Both the equipment however do come in different form factors but the most widely used are the benchtop standalone versions. A benchtop spectrum analyzer is more compact and easy to install than a network analyzer which takes more space and is heavy.
Both the devices come in multiple form factors:
- PC USB Based: PC-based network and spectrum analyzers are meant for light testing and do not offer higher specifications, what makes them so interesting is the ease of use and their portability. For a student or a hobbyist on a budget, a USB-based option would be sufficient.
- Handheld: compared to the PC-USB based versions, the handheld variant of the two devices comes with an integrated screen that allows the users to analyze the signals without needing a laptop or a monitor. The compact size allows the users to carry them easily and allows to use them anywhere since they do not require a direct power source other than while being charged.
- Benchtop: A benchtop standalone version is mostly recommended as they offer complete features for both spectrum and network analyzers. However, they are very costly and might not be an easy purchase for a hobbyist or a student.
Both devices offer a unique set of features required for testing in their respective fields.
However, one must keep in mind that these devices are very complex for a beginner or someone with zero to no engineering background. The devices are meant for engineering professionals.
Both the devices can perform functions of each other but to a limited extent. A network analyzer can be used as a spectrum analyzer since the more recent versions of the device do offer this feature; the same way an oscilloscope is used as a spectrum analyzer by using its FFT (Fast Fourier Transform) function.
In the end, it’s always up to the requirements of the user and their personal preferences. But, it is wise to start with an affordable or cheaper option like a USB-based version (either spectrum analyzer or network analyzer) if a user is unsure of their requirements and would like to try them out on a budget.