With vector network analyzers, the commercial offerings seem to come in two flavors: relatively inexpensive but limited capabilities, and full-featured but scary expensive. There doesn’t seem to be much middle ground, especially if you want something that performs well in the microwave bands.

Unless, of course, you build your own vector network analyzer (VNA). That’s what [Henrik Forsten] did, and we’ve got to say we’re even more impressed by the results than we were with his earlier effort. That version was not without its problems, and fixing them was very much on the list of goals for this build. Keeping the build affordable was also key, which resulted in some design compromises while still meeting [Henrik]’s measurement requirements.

The Bill of Materials includes dual-channel broadband RF mixer chips, high-speed 12-bit ADCs, and a fast FPGA to handle the torrent of data and run the digital signal processing functions.

Designing a low-cost high-performance 10 MHz – 15 GHz vector network analyzer
https://hforsten.com/designing-a-low-cost-high-performance-10-mhz-15-ghz-vector-network-analyzer.html

We are all taught the importance of bypass or decoupling capacitors, but mostly through rules-of-thumb we ought to follow, such as: “each IC should have a 0.1 µF capacitor”, “add one 1 µF for every eight ICs”, place decoupling capacitors “as close as possible”, and so on. There’s very little about experimentally measuring and verifying the effect of capacitor networks.

The standard for measuring PDN impedance is a vector network analyzer (VNA) in a 2-port shunt-thru connection. VNAs are very expensive, and most VNAs are designed for communications applications instead of general impedance analysis (frequency ranges into the 10s of gigahertz, but bottoming out at hundreds of kilohertz or the low single-digit megahertz range). I’ve been exploring using a more humble setup of a spectrum analyzer with tracking generator to get good results, as long as some reasonable assumptions are guaranteed.

Scattering parameters (S-parameters), which describe the fundamental characteristics of RF networks, come in many flavors, including small signal, large signal, pulsed, cold, and mixed mode. They quantify how RF energy propagates through a system and thus contain information about its fundamental characteristics.

Using S-parameters, we can represent even the most complex RF device as a simple N-port network. Figure 1 shows an example of a two-port unbalanced network, which can be used to represent many standard RF components such as RF amplifiers, filters, or attenuators, to name a few.

LiteVNA current has two versions: LiteVNA 62 and LiteVNA 64. Besides LCD screen sizes (2.8 inch for the 62 model versus 3.95 inch for the 64 model) and battery capacities (1.3 Ah for the 62 model versus 2 Ah for the 64 model), all other technical aspects are identical. The model I got here is the LiteVNA 62.

Unlike the NanoVNA-F V2 which is enclosed in a metal case, the LiteVNA comes in a plastic case with no additional shielding. But the build quality looks quite decent.

https://eleshop.eu/litevna.html

The LiteVNA is a portable 50 kHz – 6.3 GHz vector network analyzer which design is based on the NanoVNA and SAA2. This vna is designed to measure equipment reflection and transmission coefficients without the need for a large analyzer. The LiteVNA uses one mixer which enables S11 and S21 measurements through RF switching and TDR/DTF measurements through IFFT calculations.
The analyser has a 2.8″ touch-screen display that can show the measurements in 10-1001 data points. Furthermore, the analyser has a built-in 1300 mAh battery and can be connected to an android phone or PC. Connecting to a phone or PC allows for controlling the analyser and displaying the measurements.

In this video, I did a comprehensive teardown of a S-A-A-2 NanoVNA (50kHz – 3GHz). Since the design of the S-A-A-2 is open-sourced, you can easily identify all the sub-circuits. You can get one from https://ban.ggood.vip/11peX High resolution pictures can be found at
http://www.kerrywong.com/2022/04/03/nanovna-saa-2n-teardown-pictures/

NanoVNA V2 Plus4
4GHz 4 inch 90dB dynamic range vector network analyzer
https://www.tindie.com/products/hcxqsgroup/nanovna-v2-plus4/?utm_source=hackaday&utm_medium=link&utm_campaign=fromstore

NanoVNA V2 Plus4
https://nanorfe.com/nanovna-v2.html

4GHz second generation NanoVNA vector network analyzer, our own design.

The V2 Plus4 is a new design not based on the original NanoVNA, and uses 4GHz synthesizers instead of harmonics. The latest hardware version with 4″ display, aluminum case, higher dynamic range, and 4 times the sweep speed of the original V2.
Features:

up to 90dB dynamic range, can measure duplexers (see comparisons and specifications below)
4 inch display
4x faster sweep speed (400 points/s)
50kHz – 4GHz frequency range
1024 point sweep (with NanoVNA-QT software)
if DHL shipping is selected, includes 3200mAh 18650 battery
Accepts standard flat-top 18650 lithium-ion battery, includes on-board protection and charging

Note: All NanoVNA V2 versions switch on and off the test signal rapidly, can not measure crystals and can not be used as a signal generator.