Half-wavelength Transmission Lines Research Articles

Energization of a Half-Wavelength Transmission Line - Pre-Operational Transients Studies

In the present paper the main results of the pre-operational studies related to the energization maneuver of a Half-Wavelength Transmission Line (AC-Link), are presented. The simulations were performed in PSCAD with actual Brazilian system data. Specifically the following studies were performed: electromagnetic transient studies of energization maneuver considering no fault and the occurrence of fault along the trunk; dynamic analysis of generator units that will energize the AC-Link; TRV on the circuit-breaker that will energize the trunk. The main conclusion is that the AC-Link energization experiment can be implemented without jeopardizing or causing time-life reduction of the equipment involved in the experiment, which comprises the generator unit that will energize the trunk, the step-up transformer, the arresters that will be kept during the experiments, as well as the circuit-breaker that will energize and then trip the AC-Link.

FACTS for Tapping and Power Flow Control in Half-Wavelength Transmission Lines

This paper presents a solution for transmission of bulk power over long distances. It allows the interconnection between remote power plants and power grids, which is a common situation in countries with continental dimensions, such as China, Russia, Brazil, and Canada, and also special projects like supergrids in Europe and Asia. This paper also presents an analytical analysis of series and shunt FACTS applications for tapping and power flow control in half-wavelength transmission lines. The proposed FACTS devices are able to drain or inject fractional active power in the half-wavelength line and simultaneously to control the main power flow through the line by means of reactive power compensation, without mischaracterizing its particular principle of half-wavelength operation. Simulation results from a frequency-dependent model of transmission line and the complete models of the series and the shunt FACTS devices were obtained in the PSCAD/EMTDC to demonstrate the feasibility of the proposed systems.

A Compact and Embedded Balanced Bandpass Filter With Wideband Common-Mode Suppression on Wireless SiP

A compact balanced bandpass filter is proposed using a novel circuit topology, which includes a differential resonator and a common resonator in the conventional quasi-lumped coupled-line circuit, instead of adopting quarter-wavelength or half-wavelength transmission lines in the filter design. Based on this circuit topology, the balanced bandpass filter can support bandpass filtering function under differential-mode operation and exhibit bandstop filtering function under common-mode noise. By employing the advantage of the low-temperature co-fired ceramic fabrication technology, a compact balanced bandpass filter is centered at 3.42 GHz with fractional bandwidth 10.4% for differential signals and rejection band is from 1.48 to 7.4 GHz for the common-mode noise. Moreover, the proposed filter is able to introduce a transmission zero with excellent common-mode suppression (>;40 dB) within the differential-mode passband. The electrical size of this filter is 5.6 × 5.4 mm with the corresponding electrical size 0.113 × 0.109 λ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">g</sub> , where λ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">g</sub> is the guided wavelength at the center frequency 3.42 GHz. This compact balanced bandpass filter is suitable to be applied to the system-in-package technology for wireless application.

Superconducting Multiplexer Filter Bank for a Frequency-Selective Power Limiter

This work proposes a superconducting multiplexer filter bank configuration to be used as a frequency-selective power limiter. The proposed configuration limits narrowband high-power signals within a single frequency band without degrading the signal performance in the rest of the frequency bands. To accomplish this, we need to calculate the limiting power of superconducting filters implemented by means of half-wavelength transmission line resonators. The limiting power is obtained as a function of the resonator geometry, filter bandwidth, and filter order. Practical issues occurring in superconducting filters operating at high power, such as the reduction of the quality factors and de-tuning, are also analyzed and shown to not adversely affect the overall multiplexer power limiter performance.

A 32‐channel lattice transmission line array for parallel transmit and receive MRI at 7 tesla

Transmit and receive RF coil arrays have proven to be particularly beneficial for ultra-high-field MR. Transmit coil arrays enable such techniques as B(1) (+) shimming to substantially improve transmit B(1) homogeneity compared to conventional volume coil designs, and receive coil arrays offer enhanced parallel imaging performance and SNR. Concentric coil arrangements hold promise for developing transceiver arrays incorporating large numbers of coil elements. At magnetic field strengths of 7 tesla and higher where the Larmor frequencies of interest can exceed 300 MHz, the coil array design must also overcome the problem of the coil conductor length approaching the RF wavelength. In this study, a novel concentric arrangement of resonance elements built from capacitively-shortened half-wavelength transmission lines is presented. This approach was utilized to construct an array with whole-brain coverage using 16 transceiver elements and 16 receive-only elements, resulting in a coil with a total of 16 transmit and 32 receive channels.

Novel Implementation of Transversal Filters in Multilayered Microstrip Technology

This paper presents novel and compact implementations of bandpass filters using transversal topologies. The structures presented implement different transfer functions of order three in multilayered microstrip technology. In order to allow for easy implementation of the required coupling, multilayered broadside configurations are proposed. We demonstrate that with the proposed configurations, both dualband and quasi-elliptic responses can be easily synthesized, by only changing the sign of certain entries in the coupling matrix. To easily adjust the sign of the coupling, novel resonators are proposed, including simple half-wavelength transmission line resonators, meander line resonators and shortcircuited resonators. Experimental validations for both prototypes are presented, demonstrating the validity and usefulness of the proposed configurations.

Design and Performance of an Electrically Small Slot Loop Antenna With a Miniaturized Superconducting Matching Circuit

In order to realize a small superconducting receiver, we designed an electrically small slot loop antenna with a miniaturized impedance matching circuit. The area of the slot loop antenna is 4 mm /spl times/ 4 mm on MgO substrate at a frequency of 2.4 GHz. By applying 2-pole bandpass filter technique, we propose a design theory of the miniaturized impedance matching circuit that consists of coplanar waveguide (CPW) quarter and half wavelength transmission lines of meandering geometry and the impedance inverting circuits (J inverters). By using electromagnetic field simulator, we realized the circuit which matches the small radiation resistance R/sub a/=0.776 /spl Omega/ of the electrically small slot loop antenna to the feeder impedance Z/sub 0/=50 /spl Omega/, and attained the normalized bandwidth of 3%. We also made a preliminary experiment on this miniaturized antenna using a YBCO thin film on MgO substrate.

Compact microstrip bandpass filter with two transmission zeros using a stub-tapped half-wavelength line resonator

A compact microstrip bandpass filter is developed using a half-wavelength (/spl lambda//2) transmission line resonator with a pair of tap-connected open-ended stubs. Such paired stubs with total length of about /spl lambda//2 constructs an equivalent line resonator. Together with two separated /spl lambda//4 line resonators, the three transmission poles can be achieved inside the passband. Meanwhile, two stub lengths are adjusted slightly longer and shorter than /spl lambda//4 to realize the two transmission zeros at both low and high rejection bands. Further, the long tapped-stub is kept wider than its short counterpart to improve the low rejection behavior. A filter sample is designed and fabricated to provide an experimental verification on the proposed filter.

Planar transmission line resonators from YBa/sub 2/Cu/sub 3/O/sub 7-x/ thin films and epitaxial SIS multilayers

The authors have grown c-axis-oriented YBa/sub 2/Cu/sub 3/O/sub 7-x/ (YBCO) thin films and epitaxial YBCO/NdAlO/sub 3//YBCO trilayers by sputtering. From the YBCO films, coplanar half-wavelength transmission line resonators were patterned. At 77 K the unloaded quality factors of coplanar stripline resonators were up to 2570 at 5.6 GHz. The attenuation constant of such a line was evaluated to be 0.6 dB/m at 77 K and at 5.6 GHz. Coplanar waveguide resonators yielded quality factors up to 1200 at 77 K and at 6.2 GHz resulting in an attenuation constant of 1.8 dB/m. From these measurements the surface resistance values R/sub S/ of the films were determined. The lowest R/sub S/ was 105 mu Omega at 77 K and at 6.2 GHz. Trilayer structures with a dielectric as thick as 800 nm were patterned into microstrip resonators. At 50 K the authors measured a quality factor of 85 at 4.7 GHz, resulting in an attenuation of 26 dB/m and a surface resistance of 340 mu Omega . For thick dielectrics the upper YBCO film already contains significant portions of polycrystalline material.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Broadband branchline coupler for S band

The design of an S-band, broadband, microstrip 3 dB, 90 degrees branchline coupler is described and measured results for a prototype version are given. The design uses broadbanding stubs and three branches, with the central branch split into two of twice the characteristic impedance and separated by half wavelength transmission lines. This is a new technique to improve the bandwidth of which a theoretical account was given by Mayer (see ibid., vol.26, no.18, p.1477-8, 1990). Measured results for the prototype coupler show return loss greater than 17 dB and isolation greater than 16.5 dB, over a percentage bandwidth of 45%. >

Analysis of half-wavelength transmission lines with simulation of corona losses

The growing interest in very-long-distance transmission (2-3000 km) and the state of the art of half-wavelength transmission lines are briefly discussed. A model for the numerical simulation of corona losses at high electric gradients is proposed. Then an analysis is made of the steady-state and transient operation of an 800 kV, 60 Hz, 2500 km double circuit line. Results show that corona losses drastically limit the sustained overvoltages, but also place a limit on transmissible power and can affect transient stability. Possible schemes for interconnection of two half-wavelength lines at intermediate switching stations are also examined in order to attain acceptable system reliability.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

High temperature microphone system

Apparatus for measuring pressure fluctuations in air or other gases in an area of elevated temperature. A condenser microphone is located in the area of elevated temperature and electronics for processing changes in the microphone capacitance is located outside the area and connected to the microphone by means of a high-temperature cable assembly. The microphone includes apparatus for decreasing the undesirable change in microphone sensitivity at high temperatures. The high-temperature cable assembly operates as a half-wavelength transmission line in an AM carrier system and maintains a large temperature gradient between the two ends of the cable assembly. The processing electronics utilizes a voltage controlled oscillator for automatic tuning thereby increasing the sensitivity of the measuring apparatus.

Rf-biased SQUID with half-wavelength transmission line

Rf-biased SQUID with half-wavelength transmission line

Two-element Phase-switched Interferometers for Radio Star Scintillation Studies at 110 and 74 MHz

We describe here two-element phase-switched interferometers built for the study of ionospheric irregularities by recording the amplitude scintillations in the flux of the radio stars, Cas A and Cyg A. Two interferometers have been built. The 110 MHz interferometer has been operating at Ahmedabad and the 74 MHz one, which is an improved version of Ahmedabad unit, has been operating at Gulmarg. The 110 MHz interferometer has been described in some detail and improvements incorporated in the 74 MHz interferometer are briefly discussed. The 110 MHz interferometer consists of two Yagi antennas, spaced ten wavelengths apart, connected to a superhet receiver. A half wavelength transmission line is switched in and out, at the rate of 340 Hz, between one of the antennas and the input of the receiver, which modulates the signal received from a radio source of small angular size. The fringe pattern of such an interferometer is relatively insensitive to the cosmic noise background, because it is an extended radio sou...