Balanced Transmission-Line Measurements Using Coaxial Equipment (Correspondence)

Osteoporosis represents a major health problem, resulting in substantial increases in health care costs. There is an unmet need for a cost-effective technique that can measure bone properties without the use of ionizing radiation. The present study reports design, construction, and testing of a safe, and easy to use radiofrequency device to detect osteoporotic bone conditions. The device uses novel on-body antennas contacting the human wrist under an applied, operator-controlled pressure. For the dichotomous diagnostic test, we selected 60 study participants (23–94 years old, 48 female, 12 male) who could be positively differentiated between healthy and osteopenic/osteoporotic states. The band-limited integral of the transmission coefficient averaged for both wrists, multiplied by age, and divided by BMI has been used as an index. For a 100 MHz frequency band centered about 890–920 MHz, the maximum Youden’s J index is 81.5%. Both the sensitivity and specificity simultaneously reach 87% given the calibration device threshold tolerance of ±3%. Our approach correlates well with the available DXA measurements and has the potential for screening patients at risk for fragility fractures, given the ease of implementation and low costs associated with both the technique and the equipment. The inclusion of radiofrequency transmission data does add supplementary useful information to the available clinical risk factors.

show abstract

“…via a 180° power splitter. A similar antiphase feeding mechanism for two dipole wings is otherwise known as the Dyson balun [68][69][70] .…”

Section: Methodsmentioning

confidence: 99%

Concept of a Radiofrequency Device for Osteopenia/Osteoporosis Screening

Makarov

Noetscher

Arum

et al. 2020

Sci Rep

View full text Add to dashboard Cite

show abstract

“…Although both have been widely used in measuring the radiation patterns and gains of balanced antennas, a literature survey shows that only a few studies have been reported on the removal of their effects in measuring the impedances of balanced antennas [11]- [13]. There seems no information on the measurement of the efficiency of a balanced antenna with a balun.…”

Section: Balun Methodsmentioning

confidence: 99%

“…The required unknowns and are solved from the two equations of (7) as (10) The remaining equation of (7) can be rewritten as (11) Any two measurements of two different two-port standards yield two equations for (9), then and can be solved. As all required unknowns and have been solved from the fourth step, the S-parameter of the DUT can be obtained from (12) The impedance of the differentially driven DUT is calculated by (13) where is reference impedance of 50 .…”

Section: A Balun Methods Using a 3-port 180 Power Dividermentioning

confidence: 99%

See 1 more Smart Citation

Measuring the Impedance and Efficiency of Differentially Driven Microstrip Antenna by Two Balun Methods

Zhang

2014

IEEE Trans. Antennas Propagat.

View full text Add to dashboard Cite

Two balun methods for measuring the impedance and efficiency of a differentially driven microstrip antenna with a twoport vector network analyzer are evaluated. It is shown that the non-ideal nature of real baluns will cause measurement errors. This paper proposes and describes the new calibration techniques for the removal of the effects of actual baluns. The balun methods and obtained experimental results are discussed and validated.

show abstract

“…The difference in measured and simulated return loss values is due to the presence of Teflon material in the fabricated model. Dyson balun topology feeds the antenna with balanced currents in both arms and generates acceptable level of circularly polarised radiation pattern with moderate gain . A gain of 5 dB along the boresight axis is achieved both in simulated and measured results, and deep back nulls can be seen in Figure B.…”

Section: The Quadrifilar Helix Antennamentioning

confidence: 99%

Ground plane impact on quadrifilar helix antenna performance with respect to deployment heights

Ahmad

Khan

Amin³

et al. 2019

Int J Communication

View full text Add to dashboard Cite

Quadrifilar helix antenna (QHA) has its applications in satellite communications. This paper presents the performance optimisation of input and radiation characteristics of QHA in the presence of infinite and finite metallic ground planes. For the infinite ground plane, it has been observed that input parameters such as impedance and voltage standing wave ratio (VSWR) are stable, and the antenna has broader half power beamwidth (HPBW). Smaller metallic platforms that act as finite ground planes produce better 3-dB axial ratio beamwidth and boresight axial ratio. Deployment of QHA on smaller metallic platforms such as nanosatellites and CubeSats enhances the circularly polarised beamwidth of the antenna with improved boresight axial ratio. However, on large low earth orbit (LEO) satellites, stable input characteristics and broader HPBW have been achieved at the cost of narrow circularly polarised beamwidth and degraded boresight axial ratio.KEYWORDS helix antenna, satellite antennas, satellite communication, RF measurements, wire antennas, wideband antennas 1 | INTRODUCTION Quadrifilar helix antenna (QHA) has a wide range of applications and is deployed on various space and terrestrial communication platforms. 1-5 It is used for global positioning system (GPS), 5 radio frequency identification (RFID), 6 and low earth orbit (LEO) satellites. 7 In authors' opinion, further study is required on the QHA deployment over terrestrial and satellite platforms.In literature, the effect of ground plane on the QHA radiation characteristics is explained based on two theories: image theory and uniform theory of diffractions. Image theory explains the performance of QHA above large infinite ground planes that is helpful in examining QHA for large platforms. 8 If the ground plane is a perfect electric conductor, it will reflect radiations caused by any antenna installed over it. The image theory assumes that this reflected signal is originated by another antenna placed at the mirror image of the real antenna. This assumption helps to analyse ground reflections as the superposition of two radiation sources. Uniform theory of diffraction (UTD) is applicable to the finite ground plane models to describe the diverging behaviour of QHA from an expected response. 9,10 UTD is derived from the geometrical theory of diffraction (GTD) that has a significant impact on the high frequency computational This work was supported by COMSATS University Islamabad, Lahore Campus, Lahore Pakistan.

show abstract

Balanced Transmission-Line Measurements Using Coaxial Equipment (Correspondence)

Cited by 9 publications

References 4 publications

Concept of a Radiofrequency Device for Osteopenia/Osteoporosis Screening

Concept of a Radiofrequency Device for Osteopenia/Osteoporosis Screening

Measuring the Impedance and Efficiency of Differentially Driven Microstrip Antenna by Two Balun Methods

Ground plane impact on quadrifilar helix antenna performance with respect to deployment heights

Contact Info

Product

Resources

About