Design of a broadband microwave sampler applied to VNA

A broadband microwave sampler applied to vector network analyzer is presented in this paper. In vector network analyzer, the sampler is an important part of phase-locked system and S parameters measurement system. It converts high frequency microwave signals into low frequency signals, while amplitude and phase information of microwave signals are kept. Firstly, the principle of microwave sampler is introduced. Then realization circuits including RF matching & amplifying circuit, sampling pulse processing circuit, switch-sampling circuit and IF filter & amplifying circuit are described. Finally, measurement results of the broadband microwave sampler are given. The measurement results show that the sampler works from 30 kHz to 6 GHz, return loss of RF port could reach -10dB, and frequency conversion loss is better than -9 dB (IF amplifier with 15dB gain is included in test process). In the future, Low-frequency capacitor can be substituted by high-frequency multilayer capacitors to improve RF port´s return loss characteristic. This sampler could fit well for VNA´s application requirements.