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Duplex antenna system for MIMO application
Published in Yadwinder Kumar, Shrivishal Tripathi, Balwinder Raj, Multifunctional MIMO Antennas, 2022
D. Venkata Siva Prasad, Harsh Verdhan Singh, Punya P. Paltani, Shrivishal Tripathi
A directional coupler is a four-port waveguide, as shown in Figure 3.3, and it couples a small amount of power from the input signal for measurement purposes. In general, when port 1 is the input port, the applied signal is transmitted to port 2 (output port), and a small fraction of the power from the applied input signal at port 1, which is determined by the coupling factor of the directional coupler, is coupled to port 3 (coupled port). No signal appears (idle case) at port 4 which is known as the isolated or terminated port. However, in reality, a small portion of input signal power is obtained at the isolated port due to the mismatch of impedance at other ports, and that reflected power at the isolated port is called back power that depends on the directivity of the coupler.
D
Published in Philip A. Laplante, Comprehensive Dictionary of Electrical Engineering, 2018
directional coupler a passive, 3 or 4 port device used to sample a portion of the forward (incident) signal or the reverse (reflected) signal, or both (dual directional coupler) in an RF, microwave, or mmW circuit. Directional couplers are usually described in terms of coupling factor and directivity. The coupling factor describes what fraction of the incident (or reflected) power appears at the desired coupled port. Directivity describes the fraction of power coupled to the same port due to reverse power in the main arm of the coupler. directional overcurrent relay an overcurrent relay that operates only for overcurrents flowing in the tripping direction. Direction sensing is typically done with respect to a voltage or current signal, which is not affected by fault location. directional power relay a protective relay that operates for power flow in a given direction. Applications are in cases where normal power flow is in one direction, including anti-motoring protection on a turbine-generator and fault backfeed protection on parallel step-down transformers.
MF-UHF Directional Coupler Design Techniques
Published in Abdullah Eroglu, RF Circuit Design Techniques for MF-UHF Applications, 2017
where P1 is the input power and P3 is the output power at the coupled port. Isolation of a directional coupler can be defined as the difference in signal levels between the input port and the isolated port when the two output ports are matched loads. The requirement is to have high isolation between the input and isolated ports so that the signal purity can be maintained. Ideal couplers have infinite isolation. The isolation level can be then defined as () Isolation lavel(dB)=10log(P1P4)=−20log(|S14|)
It Is Time for Measuring Instruments to Report Measurement Uncertainty
Published in NCSLI Measure, 2018
Figure 3 shows the VNA in a power-measuring configuration. In this configuration, the VNA provides a load to dissipate the power from the device under test. The directional couplers are components that isolate the forward and reverse traveling waves. They serve to independently and simultaneously measure the voltage waves using the two detectors. Measurements using the power meter and the ECal module provide data to correct systematic errors associated with the directional couplers and the detectors inside the VNA.
Development of high power 20 dB directional coupler for Ion Cyclotron Resonance frequency system of Tokamak
Published in International Journal of Electronics Letters, 2022
Directional Couplers (DC) are passive microwave component often used in modern microwave electronics such as balanced amplifiers, balanced mixers, phase shifters, etc., also having widespread application in telecommunications, radar and information systems (Collin, 1992; Pozar, 1992). DC has an important application in radio frequency (RF) design circuits particularly for measurement of high power levels without making direct connection to the transmission line carrying the power (Mognia et al., 1999; Xue et al., 2011). Due to the growth of modern civilisation, the demand of energy resources are increasing worldwide. The need for producing endless supply of energy is the main concern. To harness the fusion energy using fusion energy reactor known as Tokamak can provide the sustainable energy supply for proper growth of civilisation. Basically, a Tokamak is an experimental reactor, which confines and control the gaseous plasma to produce thermonuclear power for future energy generation. Inside reactor, various heating methods are employed to maintain the plasma temperature to about 150 million degree centigrade to have controlled fusion reaction. Ion Cyclotron Resonance Frequency (ICRF) is a promising heating method, which uses electromagnetic waves (Radio frequency waves) to heat the plasma inside the Tokamak using RF antenna. The plasma has the property of continuously variable mismatched load. The antenna loading can also be affected and the changes occur in the antenna impedance. These fast changes in impedance can make the system inefficient to deliver power from source to plasma. For maximum power transfer from source to load, continuous plasma impedance variations has to be matched with antenna impedance with the help of online matching unit. The developed matching networks failed to cope with faster variation of the plasma load impedance. Therefore, a low power load resilient prototype ICRF system has been developed and emulated on a test bench. Schematic of the typical ICRF system (Bora et al., 2005, 2006; Jain et al., 2018) is shown in Figure 1. The prototype ICRF system consists of various components such as a 3 dB hybrid coupler (Jain et al., 2018), coaxial transmission lines, directional coupler, matching network (Bora et al., 2006), RF antenna (Jain et al., 2019), water load, etc. Here, to emulate the plasma load variation, a movable water tank-based variable load has been utilised. The developed prototype is to be utilised to achieve fast matching speed in ICRF system to improve the power transfer from source to load (Jain et al., 2018, 2019; Joshi et al., 2015). For this purpose, the forward and reflected power in the transmission line or Voltage Standing Wave Ratio (VSWR) is obtained/calculated with the help of directional coupler connected to automation unit. The automation unit in turns provide the feedback to the servo motors depending upon the VSWR, and adjusts the length of matching devices to provide maximum power transfer. Therefore, directional coupler is an essential part of the high power RF system.