Wideband Marchand Balun Research Articles

A Novel Compact Isolation Circuit Suitable for Ultracompact and Wideband Marchand Baluns

A novel compact isolation circuit (IC) is proposed for the ultracompact and wideband UHF Marchand balun topology, and exact design formulas are presented for arbitrary coupling coefficients and impedance-transforming termination impedances. The wideband Marchand balun mainly consists of two identical coupled transmission-line sections which are far shorter than 90° long, connecting segment, two or three lumped elements and the proposed IC. The novel IC features −180° phase delay between two balanced ports, and makes the ultracompact implementation possible, which is quite different from the conventional ones with 180° phase delays between two balanced ports. In addition, due to the −180° phase delays, excellent isolation performance and excellent phase responses can be performed. For the proof-of-concept demonstrations, one prototype with each coupled-line section being only 20° long and the half IC being only 20° long is tested at 700 MHz. The measured frequency responses are in good agreement with the predicted ones with the performance of the 10-dB return loss bandwidth of 40% and −15 dB isolation bandwidth of 121.4%. In terms of sizes versus bandwidths, the fabricated Marchand balun can be regarded as the best and the smallest ever recorded, based on the low-cost microstrip technology.

Modified Wideband Marchand Balun With Tunable Power Division Ratio and Constant Phase

A balun with a wide tunable power division ratio and constant phase across a wide frequency band is presented. The proposed design is a modification of the traditional Marchand balun with a varactor and series resistor loaded at the central point of the two connected pairs of coupled lines. The varactor is used to control the power division ratio at two output ports, whereas the resistor is used to stabilize the power division across a wide operational bandwidth. The achievable power division ratio and differential phase are investigated for different band ranges. A prototype is designed, fabricated, and tested. The results indicate a tuning power ratio range from 1:1 to 3.5:1 across 80% fractional bandwidth (1.2–2.8 GHz) with more than 10 dB return loss and less than 9 $^{\circ}$ differential phase.

A New Design Approach for Asymmetric Coupled-Section Marchand Balun

A systematic design for asymmetric coupled-section Marchand baluns is presented. Asymmetrically coupled transmission lines in multilayer configuration are exploited for constructing Marchand baluns. Design equations for characteristic impedance and electrical length of asymmetrical coupled transmission lines are derived for establishing a systematic design procedure. Novel Marchand balun based on these design equations is composed of two identical asymmetrical coupled transmission lines. However, contrary to the general conventional design approach where ranges for characteristic impedances of coupled lines are ambiguously capitalized, values for characteristic impedance and length are explicitly expressed. Our approach is fundamentally different from the design method using coupling coefficients where solution for coupling coefficient is inherently restricted. To verify the proposed method, one design example is performed for wideband Marchand balun in multilayer configuration, and is fabricated for verifying the design procedure proposed. Maintaining the return loss more than 10 dB, the bandwidth is measured from 0.43 to 1.0 GHz, where S21 and S31 show better than 4 dB. The measured phase and amplitude imbalances illustrate 0.5 dB and ±5o, respectively.

A novel model for a planar wideband Marchand balun

A new lumped element model for conventional Marchand baluns is presented. Analyzed by the even- and odd-mode method, the equivalent equations are derived for λ/4 coupled lines. Based on the proposed 5th-order lumped equivalent circuit for λ/4 coupled lines, the self-inductance, mutual inductive coupling and the capacitance can be calculated according to the even- and odd-mode characteristic impedance, therefore, the model parameters of the balun can be easily gained from the derived equations. To verify the model, a GaAs monolithic wideband Marchand balun was implemented and tested. The EM simulation and experimental results show a good agreement with the model simulation. This model is available in a wide frequency range and makes the design procedure of the Marchand balun faster and easier.

Broadband double‐balanced diode mixer using a Marchand balun with vertical coupling structure

AbstractIn this article, a broadband double‐balanced mixer is presented using a wideband Marchand balun implementation by vertical coupler. Frequency is selected as 1.0–3.7 GHz for radio frequency (RF), 1.14–3.84 GHz for LO, and 140 MHz for IF signals. When LO signal with 7 dBm at 2.64 GHz is injected, a conversion loss of 7.5 dB, and RF to LO isolation of −45 dB are obtained. Also, an average conversion loss of 9 dB, and RF to LO isolation of −25 dB are obtained for frequency band of 1.0–3.7 GHz. © 2009 Wiley Periodicals, Inc. Microwave Opt Technol Lett 51: 1811–1814, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.24488

A 60‐GHz millimeter‐wave CMOS Marchand balun using 0.18‐μm CMOS technology

AbstractA novel 60‐GHz wideband Marchand balun fabricated with a standard 0.18 μm six‐metal‐layer CMOS process for millimeter‐wave applications is presented. A technique for achieving good balance with the fourth metal layer microstrip conductor is used in the designed Marchand balun. The fabricated CMOS balun uses multilayer coupling with the top two layers. An output matching network is added to improve the output return loss. The measured amplitude imbalance was about ±1.5 dB from 25 to 65 GHz, over the 89% operating frequency band. © 2009 Wiley Periodicals, Inc. Microwave Opt Technol Lett 51: 766–770, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.24176