Designing a low-cost high-performance 10 MHz – 15 GHz vector network analyzer

a year ago

Vector Network Analyzer (VNA) is a device used to measure scattering parameters (S-parameters) of high-frequency electrical circuits.
VNAs are expensive, especially at higher frequencies, with high-end models costing hundreds of thousands of dollars.
The author designed a homemade VNA to overcome cost limitations, achieving a frequency range of 10 MHz to 15 GHz.
The VNA features four receivers, enabling advanced calibration methods like unknown thru and TRL calibration.
Key components include LMX2594 PLL chips for signal generation, ADL5802 mixers for down-conversion, and AD9238 ADC for sampling.
Directional couplers were custom-designed for sampling incident and reflected waves, with good performance up to 15 GHz.
The VNA's isolation exceeds 120 dB, and it achieves excellent measurement accuracy, surpassing commercial low-cost alternatives.
Total prototype cost was around $475, including components, PCBs, and a CNC-machined aluminum case.
The VNA was tested with a bandpass filter and varactor diode, showing high accuracy and low noise in measurements.
Thermal stability and harmonic mixing were addressed, with the VNA performing well up to 15 GHz despite some limitations.

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