Entity

Time filter

Source Type


Ren H.,Tsinghua University | Zhang X.,Tsinghua University | Chen Y.,Tsinghua University | Wang Y.,Syniverse | And 5 more authors.
Cryogenics | Year: 2012

In this article we elucidate the design and fabrication of a P-band cryogenic low noise amplifier (CLNA) with built-in limiter circuit, and further studied the characteristics of PIN diode limiter at different temperature. Measurements at 75 K shows the P-band CLNA with build-in limiter has a good performance with noise figure lower than 0.5 dB, the input and output voltage standing wave ratio (VSWR) less than 1.5 and input 1 dB power compression point -4 dBm within the band width 300 MHz. The variation of the gain within ±0.1 dB under the impact of 20 dBm input power level signals. In addition, the maximum allowed input power of the CLNA has increased from 13 dBm to 22 dBm. © 2011 Elsevier Ltd. All rights reserved.


Li B.,Tsinghua University | Cao B.,Tsinghua University | Guo X.,Tsinghua University | Zhang X.,Tsinghua University | And 3 more authors.
Physica C: Superconductivity and its Applications | Year: 2015

Abstract A four-pole superconducting tunable filter at VHF-band with constant absolute bandwidth is proposed. The resonator consists of a spiral-in-spiral-out (SISO) resonator with one end shorted to ground and the other end loaded with a varactor diode. Both combline and interdigital constructions for coupling are introduced, and tuned to meet the constant bandwidth requirement. The fabricated device has a compact size, a tuning range of 7.3% from 247.28 to 266.58, a 3-dB bandwidth of 2.32 ± 0.03 MHz. The insertion loss ranges from 0.5 to 1.6 dB, yielding a high unloaded Q of 1600-5500. The simulated and measured results show an excellent agreement. © 2015 Elsevier B.V.


Song X.K.,Tsinghua University | Zhang X.P.,Tsinghua University | Cao B.S.,Tsinghua University | Wei B.,Tsinghua University | And 6 more authors.
Physica C: Superconductivity and its Applications | Year: 2014

This article proposes an effective tuning method based on the time domain for improving the performance of high-temperature superconducting (HTS) bandpass filters with interdigital capacitor resonators (ICRs). Analysis of the causes of HTS filter performance deterioration reveal that such deterioration is primarily caused by the resonant frequency deviation of the resonator of the HTS filter; this deviation results from fabrication errors and from the non-uniformity of the thickness and dielectric constant of the substrate. The sensitivity of the filter, which arises from the non-uniformity of the substrate thickness and dielectric constant, is related to the type of the resonator and the group delay characteristic of the filter. A 0.4% fractional bandwidth HTS filter with ICRs at the UHF band is fabricated and tuned using mechanical rods in the time domain. By applying this method, the resonant frequency deviation of each resonator and the coupling coefficient between resonators can be measured and tuned individually. The insertion loss of the HTS filter is improved from 1.06 dB to 0.43 dB, whereas the return loss is improved from 9.57 dB to 15.1 dB. © 2014 Elsevier B.V. All rights reserved.


Li B.,Tsinghua University | Zhang X.,Tsinghua University | Chen Y.,Superconductor Technology Co. | Zhang G.,Superconductor Technology Co. | And 3 more authors.
Physica C: Superconductivity and its Applications | Year: 2013

In this article, both an 8-pole High Temperature Superconductor (HTS) filter and a cryogenic low noise amplifier (LNA) with high performance are fabricated. The HTS filter subsystem is realized by installing the HTS filter in front of the cryogenic LNA. Although the HTS filter has been fine tuned specially, the return loss performance of the HTS filter subsystem is often deteriorated due to the mismatch with the LNA. In order to improve the return loss performance of the HTS filter subsystem, we discuss and analyze the phase-matching effect between the HTS filter and the LNA. The article also proposes that tuning of the cryogenic LNA's phase by adjusting its drain current is a helpful and relatively easy method to improve the HTS filter subsystem's return loss performance in cryogenic environments. © 2013 Elsevier B.V. All rights reserved.

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