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Proceedings ArticleDOI

Design of Quadrature Directional Couplers with Continuously Variable Coupling Ratios

01 Oct 2008-pp 199-202
TL;DR: In this paper, the authors present a systematic approach for the design of directional couplers with tunable coupling strength, which maintain the properties of perfect impedance match and isolation over the whole tuning range.
Abstract: This paper presents a systematic approach for the design of directional couplers with tunable coupling strength, which maintain the properties of perfect impedance match and isolation over the whole tuning range. The devised method is based on eigenreflections and requires the synthesis of one-ports. This can be carried out with the help of graphical presentations in the Smith chart, thus fostering intuition in finding new circuit structures. The method is theoretically demonstrated by the development of a novel tunable LC-coupler or Maxwell bridge and a tunable proximity coupler. An experimental realization of the Maxwell bridge yields a tunable coupling ratio between 2 dB and 20 dB while maintaining excellent return loss and isolation.
Citations
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Journal ArticleDOI
TL;DR: In this paper, a highly reconfigurable, low power, and compact directional coupler is presented, which uses varactors and novel active inductors to achieve wide tuning ranges of operating frequencies and coupling coefficients.
Abstract: This paper presents a highly reconfigurable, low-power, and compact directional coupler. The coupler uses varactors and novel active inductors to achieve wide tuning ranges of operating frequencies and coupling coefficients. The use of a low-pass circuit architecture with only two inductors minimizes chip area, power consumption, and noise. The coupler is implemented in a 0.13-μm CMOS process. It occupies an area of 350 μm× 340 μm and consumes 40 mW or less power. The obtained 1-dB compression point is -3.2 dBm, and the measured noise figure is ~ 23 dB. These parameters compare favorably with previously published reconfigurable couplers. The measured coupling coefficient can be tuned from 1.3 to 9.0 dB at 4 GHz with 32 dB or better isolation and 15 dB or better return loss. The operating center frequency can be tuned from 2.0 to 6.0 GHz for a nominal 3-dB operation. These results agree with theoretical predictions and simulations reasonably well.

51 citations

Journal ArticleDOI
TL;DR: In this paper, a varactor-based coupler structure was proposed for reconfigurable operating frequency, power-dividing ratio, and coupler to/from crossover responses.
Abstract: This paper proposes a varactor-based coupler structure that allows for reconfigurable operating frequency, power-dividing ratio, and coupler to/from crossover responses. Particularly, this coupler can theoretically realize perfect impedance matching and port isolation at all tuning states. The coupler analysis, design equations, and design graphs were conducted, given, and discussed in detail. For demonstration purposes, two prototypes were experimentally developed and characterized. The first quadrature coupler demonstrates a frequency-tuning range from 0.632 to 1.5 GHz with a constant power-dividing ratio of −3 dB, 20-dB isolation, and >14-dB return loss. In the second prototype, for the phase error 19 dB, the power-dividing ratio was tuned from −6.4 to 20.5 dB at 1 GHz, yielding a 26.9-dB tuning range and crossover characteristics at low bias voltages. Measured and simulated results are in good agreement.

36 citations

Journal Article
TL;DR: The scope of this article is to provide a comprehensive understanding of design principles for frequency agile and reconfigurable microwave circuits such as power dividers and couplers and how they can be used in radio-frequency (RF)-transceiver subsystems to pave the way toward reconfiguring radio front-end architectures.
Abstract: Over the last decade, mobile communication and its associated mass volume market has become one of the driving forces in the technology evolution of semiconductor and microwave circuits. For handheld communication devices, it is now mainstream to support increasing numbers of communication standards and localization services that occupy ever-expanding wide frequency ranges and bandwidths. At the same time, the physical dimensions of handheld user devices are shrinking, leading to even tighter specifications for the highly integrated front-end architectures of mobile radios. Todays radio front-end architectures use dedicated receive and transmit paths for each covered communication standard, thus the overall complexity and occupied area is increasing as well. The wide frequency allocation of the regulated communication bands along with the variety of standards, which have to be covered by these radios, calls for reconfigurable and frequency agile microwave subsystems. The scope of this article is to provide a comprehensive understanding of design principles for frequency agile and reconfigurable microwave circuits such as power dividers and couplers and how they can be used in radio-frequency (RF)-transceiver subsystems to pave the way toward reconfigurable radio front-end architectures. Introducing reconfigurability in microwave circuits is achieved by tunable passive components. Tunable passives can be implemented in a variety of technologies such as ferroelectric varactors, semiconductor diodes, and microelectromechanical systems (MEMS) components. Attractive applications for tunable circuits in the RF front end are tunable matching networks, filters, reconfigurable power amplifiers, tunable voltage controlled oscillator (VCO) circuits, and finally, couplers and dividers.

30 citations


Cites background from "Design of Quadrature Directional Co..."

  • ...Using this rule, a systematic design of couplers having continuously tunable coupling ratios is possible [16], [18]....

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  • ...The scattering-parameters are then linear combinations of the four eigenreflections [18]:...

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Journal ArticleDOI
TL;DR: In this paper, two novel concepts of area-efficient ultra-wideband microelectromechanical systems (MEMS) reconfigurable coupled line directional couplers, whose coupling is tuned by mechanically changing the geometry of 3-D micromachined coupled transmission lines, utilizing integrated MEMS electrostatic actuators, are presented.
Abstract: This paper reports on two novel concepts of area-efficient ultra-wideband microelectromechanical systems (MEMS) reconfigurable coupled line directional couplers, whose coupling is tuned by mechanically changing the geometry of 3-D micromachined coupled transmission lines, utilizing integrated MEMS electrostatic actuators. Concept 1 is based on symmetrically changing the geometry of the ground coupling of each signal line, while Concept 2 is simultaneously varying both the ground coupling and the coupling between the two signal lines. This enables uniform and well predictable performance over a very large frequency range, in particular a constant coupling ratio while maintaining an excellent impedance match, along with high isolation and a very high directivity. For an implemented micromachined prototype 3-6-dB coupler based on Concept 1, the measured isolation is better than 16 dB, and the return loss and directivity are better than 10 dB over the entire bandwidth from 10 to 18 GHz. Concept 2 presents an even more significant improvement. For an implemented 10-20-dB prototype based on Concept 2, the measured isolation is better than 40 dB and the return loss is better than 15 dB over the entire bandwidth from 10 to 18 GHz for both states. The directivities for both states are better than 22 and 40 dB, respectively, over the whole frequency range. The measured data fits the simulation very well, except for higher through-port losses of the prototype devices. All devices have been implemented in a silicon-on-insulator RF MEMS fabrication process. Measured actuation voltages of the different actuators are lower than 35 V. Reliability tests were conducted up to 500 million cycles without device degradation.

27 citations


Cites background from "Design of Quadrature Directional Co..."

  • ...Thus, novel concepts are required where the input matching and directivity is maintained while the coupling ratio is tuned over a large, for instance 10 dB, range....

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Proceedings ArticleDOI
07 Jun 2009
TL;DR: In this paper, the design aspects of sequential power amplifiers (SPAs) were discussed and an optimum practical realisation was suggested, using an FPGA-circuit at the input and an adaptable directional coupler as the signal combiner at the output.
Abstract: This paper discusses design aspects of sequential power amplifiers (SPAs). After derivation of theoretical performance limits, an optimum practical realisation is suggested, using an FPGA-circuit at the input and an adaptable directional coupler as the signal combiner at the output. Design trade-offs between the optimum coupling and the output power capability of the involved amplifiers are outlined. Using SPAs efficiencies of more than 50% can be achieved under up 10dB back-off from maximum power. The combining characteristics of the adaptable combiner are investigated. Off-the-shelf power amplifiers may be employed, which can be linearized in a conventional manner. The paper closes with measurement results.

16 citations


Additional excerpts

  • ...In [7] the design of such a combiner is described....

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References
More filters
Book
01 Jan 1965
TL;DR: This book discusses waveguide junctions with several arms, dielectrics in waveguides, mode transformations, and the symmetry of wave guide junctions.
Abstract: * Chapter 1: Introduction * Chapter 2: Electromagnetic waves * Chapter 3: Waveguides as transmission lines * Chapter 4: Elements of network theory * Chapter 5: General microwave circuit theorems * Chapter 6: Waveguide circuit elements * Chapter 7: Resonant cavities as microwave circuit elements * Chapter 8: Radial transmission lines * Chapter 9: Waveguide junctions with several arms * Chapter 10: Mode transformations * Chapter 11: Dielectrics in waveguides * Chapter 12: The symmetry of waveguide junctions

648 citations


"Design of Quadrature Directional Co..." refers background in this paper

  • ...The four-port is then decomposed into four identical one-ports terminated with ideal electric or magnetic walls for even-even (ee), even-odd (ed), odd-even (de) and odd-odd (dd) excitations in the symmetry planes [6]....

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Journal ArticleDOI
J. Reed1, G.J. Wheeler1
TL;DR: In this article, an analysis of four-arm symmetrical networks such as a branched directional double stub coupler or the hybrid ring (rat race) is presented, where the input wave is broken into an even and an odd mode and the vector amplitude out the various arms is computed from the sums or differences of the reflection or transmission coefficients for the two modes.
Abstract: An analysis of four-arm symmetrical networks such as a branched directional double stub coupler or the hybrid ring (rat race) is presented. The input wave is broken into an even and an odd mode and the vector amplitude out the various arms is computed from the sums or differences of the reflection or transmission coefficients for the two modes. A zero decibel directional coupler is described and its possible use as a duplexer is proposed. The design of multiple stub directional couplers for any degree of coupling is discussed. A method of computing the bandwidth of all these couplers is outlined, and the bandwidth curves, the power out the various arms with respect to frequency of the zero decibel coupler, are computed. A tabulation is made for six different 3 db couplers (even-power split) and their standing wave ratio, evenness of power split and isolation of the fourth arm as a function of frequency assuming perfect performance at the band center.

471 citations


"Design of Quadrature Directional Co..." refers methods in this paper

  • ...Instead of analysing the structure with the method of [5], it is advantageous to apply even and odd excitations in both symmetry planes (A-A’, B-B’)....

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Proceedings ArticleDOI
15 Jun 1982
TL;DR: In this article, a microstrip variable coupling directional couplers for 4 GHz band have been proposed and tested by changing the junction capacitances of the varactor diodes.
Abstract: A microstrip variable coupling directional couplers for 4 GHz band have been proposed and tested. By changing the junction capacitances of the varactor diodes, the coupling varies from 4 dB to 20 dB, and the directivity varies from 16 dB to 29 dB. Available frequency range is from 2.7 GHz to 5.3 GHz.

34 citations


"Design of Quadrature Directional Co..." refers methods in this paper

  • ...In [2] varactor diodes are inserted into the branches of a quadrature hybrid to modify the coupling ratio between 4 and 20dB via the branch impedances....

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Proceedings ArticleDOI
03 Jun 2007
TL;DR: In this paper, a microstrip parallel coupler with tunable coupling coefficient is proposed, where two varactors are placed on parallel-coupled lines to tune the coupling coefficient.
Abstract: A novel microstrip parallel coupler with tunable coupling coefficient is proposed. Two varactors are placed on microstrip parallel-coupled lines to tune the coupling coefficient. With proper combinations of the capacitances of two varactors, the coupling coefficient can be tuned from 10 dB to 6 dB with good return loss and directivity. By using the Labview program and data acquisition component, a software configurable coupler is implemented. This software configurable coupler will be useful in microwave instrumentation.

22 citations


"Design of Quadrature Directional Co..." refers background in this paper

  • ...In [3] a variable capacitor is placed in a microstrip coupler in the middle between parallel coupled lines and a second varactor is connecting one of the lines to ground....

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Proceedings ArticleDOI
13 Jun 1999
TL;DR: In this article, a varactor tuned directional coupler with a parallel LC resonator is proposed to control the operating frequency range with 40% tunability with even-odd mode analysis.
Abstract: The directional coupler with a parallel LC resonator is proposed to control the operating frequency range. The proposed directional coupler is designed based on even-odd mode analysis technique. It has physically quarter wavelength coupled section at center frequency. A varactor tuned directional coupler is designed and fabricated with a parallel LC resonator. It shows the flexible operating frequency range with 40% tunable. The measured results show good agreement with the simulated characteristics.

18 citations


"Design of Quadrature Directional Co..." refers methods in this paper

  • ...In [1] a resonator is integrated into a coupler which can be tuned with a varactor diode to vary the centre frequency over a narrow bandwidth....

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