Bridge Coupler Research Articles

Микрополосковое устройство перекрестного резервирования 2 × 3 (3 × 2) для бортовой аппаратуры командно-измерительной системы

The paper considers the types of microstrip devices of cross redundancy with the dimension 2 × 3 (3 × 2) for onboard equipment of a command and measurement system from the point of view of meeting the basic requirements applied to them. The new type of a microstrip power divider based on combination of the Lange bridge and directional Lange coupler and Wilkinson power divider is offered. The principle of its action is considered and design characteristics are given. The advantages over the known devices of this class are shown: the maximum transmission factor is −4.76 dB, isolation between the inputs is not less than 28 dB, VSWR of the inputs and outputs is not more than 1.4 dB in a frequency band of 12 %, and compactness and relative simplicity of a design.

A Packaged 0.01–26-GHz Single-Chip SiGe Reflectometer for Two-Port Vector Network Analyzers

This article presents a packaged SiGe BiCMOS reflectometer for 0.01–26-GHz two-port vector network analyzers (VNAs). The reflectometer chip is composed of a resistive bridge coupler and two wideband heterodyne receivers for coherent magnitude and phase detection. In addition, a high-linearity receiver channel is designed to accommodate ~20 dBm of RF input power to the reflectometer. External sources are used to provide stimulus over the entire bandwidth, and a high-linearity shunt 50- $\Omega $ switch is placed at the input of each reflectometer chip to provide a matched condition for better measurement accuracy. The measured dynamic range (DR) of the heterodyne receiver is 129±3 dB at 0.01–26 GHz at an IF resolution bandwidth (RBW) of 10 Hz. The reflectometer chip is packaged on a low-cost printed circuit board (PCB) and connectorized for repeatable measurements. Several passive and active device-under-test (DUTs), such as filters and amplifiers, are measured in single- and dual-port complex $S$ -parameter setup at 0.01–26 GHz. The single-chip reflectometer results in excellent agreement with commercially available test equipment and with minimal magnitude and phase difference. Several definitions (mean deviation and error vector) are used to quantify the measurement accuracy. A measured $S_{21}$ of −80 dB is obtained using high-rejection filters. An in-depth DR analysis of possible limiting factors in the measurement setup is also presented. This article shows that silicon-based highly integrated reflectometers can be used in low-cost VNAs with excellent DR and accuracy.

Optimization of the S-band side-coupled cavities for proton acceleration

The proton beam with energy around 100 MeV has seen wide applications in modern scientific research and in various fields. However, proton sources in China fall short for meeting experimental needs owing to the vast size and expensive traditional proton accelerators. The Institute of Nuclear Science and Technology of Sichuan University proposed to build a 3 GHz side-coupled cavity linac (SCL) for re-accelerating a 26 MeV proton beam extracted from a CS-30 cyclotron to 120 MeV. We carried out investigations into several vital factors of S-band SCL for proton acceleration, such as optimization of SCL cavity geometry, end cell tuning, and bridge coupler design. Results demonstrated that the effective shunt impedance per unit length ranged from 22.5 to 59.8 MΩ/m throughout the acceleration process, and the acceleration gradient changed from 11.5 to 15.7 MV/m when the maximum surface electric field was equivalent to Kilpatrick electric field. We obtained equivalent circuit parameters of the biperiodic structures and applied them to the end cell tuning; results of the theoretical analysis agreed well with the 3D simulation. We designed and optimized a bridge coupler based on the previously obtained biperiodic structure parameters, and the field distribution un-uniformness was < 1.5% for a two-tank module. The radio frequency power distribution system of the linac was obtained based on the preliminary beam dynamics design.

Bridge coupled drift tube linacs

Modern linac designs for treating radioactive waste achieve high proton currents through funneling at low energy, typically around 20 MeV. The resulting switch to a high-frequency accelerating structure poses severe performance and fabrication difficulties below 100 MeV. Above 100 MeV, proven coupled-cavity linacs (CCLs) are available. However, at 20 MeV one must choose between a high-frequency drift-tube linac (DTL) or a coupled-cavity linac with very short cells. Potential radiation damage from the CW beam, excessive RF power losses, multipactoring, and fabricability all enter into this decision. At Los Alamos, we have developed designs for a bridge-coupled DTL (BCDTL) that, like a CCL, uses lattice focusing elements and bridge couplers, but that unlike a CCL, accelerates the beam in simple, short, large aperture DTL modules with no internal quadrupole focusing. Thus, the BCDTL consumes less power than the CCL linac without degrading beam performance and is simpler and cheaper to fabricate in the 20 to 100 MeV range.

Energy recovery in the Los Alamos free electron laser

Experiments to demonstrate recovery in conjunction with the Los Alamos free electron laser are reported in this paper. Deceleration of the electron beam greater than 70% has been observed. Beam transport through the system down to 3.5 MeV has been obtained and power flow measurements have been made that demonstrate the conversion of beam energy back into rf power. The resonant bridge couplers appear to function as designed. Predicted instabilities in the beam transport system have been observed.