Microstrip hairpin filter for cryogenic high sensitive measurement systems

We have studied and analyzed the new structures of band-pass filters for microwave frequency range 9 kHz- 6 GHz. These filters can be used as a part of superconducting quantum bit measurement equipment. The filter operation temperature is 4,2 K. Unlike other types of filters the suggested structures have broad suppressed frequency band with more than 40 dB attenuation, significantly small dimensions and opportunity to operate at low temperatures. The main idea of the filter structure is to use band-pass hair pin filter in a combination with non-regular transmission lines. The measurements were performed at 298 K and 77.4 K in 9 kHz- 6 GHz frequency range. The filters dissipations in a pass band (from 2.55 GHz to 2.667 GHz) are 5 dB. The stop band attenuation (9 kHz- 6 GHz) is more than 40 dB. The results of the experiments confirm the lack of parasitic pass bands at higher frequency range. All experiments were performed in the laboratory of the quantum detection at Institute of the Photonic Technology (IPHT, Jena, Germany).