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LO Leakage in Six-Port Modulators and Demodulators and its Suppression Techniques
Linköping University, Department of Science and Technology, Physics and Electronics. Linköping University, The Institute of Technology.
Linköping University, Department of Science and Technology, Physics and Electronics. Linköping University, The Institute of Technology.ORCID iD: 0000-0003-2117-1178
Linköping University, Department of Science and Technology, Physics and Electronics. Linköping University, The Institute of Technology.
Linköping University, Department of Science and Technology, Physics and Electronics. Linköping University, The Institute of Technology.
2012 (English)Conference paper, Oral presentation only (Refereed)
Abstract [en]

In a six-port demodulator utilizing diodes for power detection, impedance mismatch at the interface between the six-port correlator and diodes generates unwanted local oscillator (LO) leakage to the radio frequency (RF) port. A six-port modulator that uses variable reflection coefficients at specific ports to generate a modulated RF may also suffer from LO leakage if there is a static part in the reflection coefficient. It is known that LO leakage to the RF port not only generates unwanted emission of the LO signal, but also degrades the receiver system performance due to a dynamic dc offset and second-order non-linearity at the detected baseband signal. How this LO leakage appears to the RF port in six-port demodulators and modulators are analyzed. Two different approaches to suppress the LO leakage is then discussed: a) diode impedance matching and b) introduction of a λ/4 line on specific ports. The performance when λ/4 lines are used on specific ports is verified by measurement for both a demodulator and a modulator. The measurement shows high suppression of the LO leakage.

Place, publisher, year, edition, pages
IEEE , 2012. 1-3 p.
Keyword [en]
Six-Port Correlator, Six-Port Receiver, LO Leakage, LO Suppression
National Category
Engineering and Technology
Identifiers
URN: urn:nbn:se:liu:diva-77207DOI: 10.1109/MWSYM.2012.6258402ISBN: 978-1-4673-1086-4 (print)ISBN: 978-1-4673-1085-7 (print)OAI: oai:DiVA.org:liu-77207DiVA: diva2:525542
Conference
International Microwave Symposium, June 17-22, Montréal, Canada
Available from: 2012-05-08 Created: 2012-05-08 Last updated: 2015-03-18Bibliographically approved
In thesis
1. Study of Six-Port Modulators and Demodulators for High-Speed Data Communications
Open this publication in new window or tab >>Study of Six-Port Modulators and Demodulators for High-Speed Data Communications
2012 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

There is an increasing demand for high-speed wireless data communications to support consumers’ need for, among other things, real time streaming of high definition video and fast file transfers. One radio architecture that has a potential to meet the increasing demand for high-speed data communications is a radio technique based on the six-port architecture. In addition to high-speed, the six-port radio also allows low power consumption and low cost. In this thesis, a comprehensive study of the six-port radio technique for high data rate (> 1 Gbit/s) and low complexity are presented.

Firstly, a technique to suppress the carrier leakage was proposed, analyzed and verified by measurements. The proposed technique uses only a phase shifting network between the six-port correlator and its variable impedance loads, hence it is easy to implement. When the proposed carrier leakage suppression technique is used together with differential control signals, it also has the benefit of both improving the linearity and increasing the output power of the modulator. The same carrier leakage suppression technique can also be used in a six-port demodulator (receiver) to improve its performance.

Secondly, Schottky diodes were proposed to be used as high-speed variable impedance loads. A six-port modulator operating at 7.5 GHz, using the carrier leakage suppression technique together with Schottky diodes as variable impedance loads, was manufactured. Measurements on a 16 quadrature amplitude modulated (QAM) signal with a symbol rate of 300 Msymbol/s, i.e., a data rate of 1.2 Gbit/s, have proved high-speed operation, good modulation properties as well as carrier leakage suppression.

Thirdly, a six-port demodulator was built for high data rate applications and measurements were conducted to characterize its performance. Demodulation of a 16-QAM signal at a data rate of 1.67 Gbit/s results in an acceptable bit error rate and error vector magnitude (EVM) performance.

Last but not least, new diode configurations were proposed, analyzed and verified for use in six-port demodulators. Using the proposed diode configurations, the use of differential amplifiers, as commonly used in a six-port demodulator, can be avoided. Avoiding the use of differential amplifiers allows high-speed processing and at the same time reduces the power consumption and implementation complexity. In the context of the new diode configurations, it was shown that a six-port receiver has better EVM vs frequency performance and lower implementation complexity, compared to a five-port or four-port receiver.

Place, publisher, year, edition, pages
Linköping: Linköping University Electronic Press, 2012. 79 p.
Series
Linköping Studies in Science and Technology. Dissertations, ISSN 0345-7524 ; 1445
National Category
Communication Systems
Identifiers
urn:nbn:se:liu:diva-76087 (URN)978-91-7519-899-6 (ISBN)
Public defence
2012-05-31, K1, Kåkenhus, Campus Norrköping, Linköpings universitet, Norrköping, 10:00 (English)
Opponent
Supervisors
Available from: 2012-05-08 Created: 2012-03-26 Last updated: 2012-05-08Bibliographically approved

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