rf conditioning and breakdown analysis of a traveling wave linac with collinear load cells

Huazhong University of Science and Technology (HUST) has built a compact linac-based terahertz free electron laser (THz-FEL) prototype. In order to achieve compact structure, the linac uses collinear load cells instead of conventional output coupler to absorb remanent power at the end of linac. The new designed structure is confronted with rf breakdown problem after a long time conditioning process, so we tried to figure out the breakdown site in the linac. Without transmitted signal, we propose two methods to analyze the breakdown site mainly based on the forward and the reflected power signals. One method focuses on the time relationship of the two signals while the other focuses on the amplitude. Both the two methods indicate the breakdown events happened at the end of the linac and more likely in the first or the second load cell

A 2.4 mW, 11.7±0.4dB, 3 to 5 GHz wide-band LNA for super-regenerative IR-UWB receiver

This paper presents a low-power wideband LNA for the Super-Regenerative IR-UWB receiver. To meet the LNA figures of merit, which are the wideband gain flatness, low power and low noise figure, we have proposed an improved input matching network, combined with the current-reuse technique and the power-constrained simultaneous noise and input matching (PCSNIM). Designed with CMOS 0.18 ??m technology, this 3-5 GHz LNA demonstrates the power-gain of 11.8dB with only ??0.4dB variation, a minimum NF of 3.5 dB and an input impedance matching lower than -10 dB across the 3-5 GHz band. The LNA core consumes only 2.4 mW from 1.2 V supply voltage and 2 mA current. ? 2013 IEEE.EI