Izumi Fukasaku

Development of edge-on type CdTe detector module for gamma camera

The detector module using CdTe with edge-on configuration was developed. The pixel pitch is 1.4 mm, and 1024 pixels constitute the field of view of 45 mm square. The CdTe crystals sandwich thin circuit boards to form CdTe cards, and 16 CdTe cards are mounted on the module. The intrinsic energy resolution of 4.4% (FWHM) was achieved with Tc-99m at CdTe temperature of 25 °C. It remains 5.1% at 40 °C, which implies the possibility of air-cooling system. Uniformity and count-rate performance were also evaluated.

High-speed transmission copper cable for 25Gbit/s/lane

The conventional copper cable has the intra-pair skew about 10ps/m, and it makes using the copper cable for the 25Gbit/s/lane difficult. For the purpose of reducing intra-pair skew, we analyzed the generation factor of the intra-pair skew about some cables. For this analysis, we converted the S-parameters of cables into the impulse responses and the step responses of each mode. As a result, in the conventional copper cable, it became clear that the intra-pair skew was caused by the propagation time difference between differential mode and common mode, and that the reduction of the intra-par skew is difficult structurally. On the other hand, the new structure cable, “OMNIBIT®”, which has one batch extruded insulator covering two wires, does not have the propagation time difference between differential mode and common mode. It was confirmed that the new structure was hardly to increase the intra-pair skew structurally. As a result of the trial manufacturing with the new structure cable, it was confirmed that the intra-pair skew was less than or equal to 6ps/m.

Estimation of mode-conversion of differential copper cables using lumped circuit parameters

Relationship between an S-parameter component corresponding to mode conversion and lumped parameters is investigated for high-speed differential copper cables using the theory of multi-conductor transmission lines. Experimentally observed frequency dependence of Scd21 is reproduced by analytical theories. Small fabrication tolerance is clarified.