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Current artificial magnetic conductor (AMC) designs use metallic patterns on rigid substrates and focus on shapes and sizes of AMC structures, rather than on material performance, which has hindered operation bandwidth and design flexibility. Here, we introduce printed graphene AMC-based broadband and flexible microwave radar absorbers, which not only redirect but also absorb the incident wave so to broaden the operation bandwidth. Contrasting to other reported works, the phase characteristics of the AMCs are realized through the control of the surface resistance provided by printed graphene laminates. We produced a variety of AMC structures, composed of printed graphene circular ring arrays with exactly the same shape and size, but different sheet resistances. By carefully designing the sheet resistance of printed graphene laminates, the optimized anti-phase reflection cancellation between AMCs can be achieved. With printed graphene AMCs and flexible dielectric substrate, the absorber presented in this work has a broadband effective absorption (above 90% absorptivity) from 7.58 GHz to 18, is polarization insensitive under normal incident, and can work at relatively wide incident angles. Furthermore, this absorber is capable of bending easily with notable performance, which makes it ideal for applications with irregular and uneven shapes. [ABSTRACT FROM AUTHOR]

A wideband CMOS LC tank voltage-controlled oscillator (VCO) with low phase noise variations and a linearized gain has been designed using a new binary-weighted switched-capacitor and digitally-controlled varactor bank. The novel design has the advantages of more linear VCO frequency tuning, lower phase noise and reduced gain to variations in supply voltage. The proposed VCO has been designed using UMC 90-nm, 6-metal CMOS technology and features phase noise variation of less than 4.9 dBc/Hz. The VCO operates from 3.45 to 6.55 GHz, with phase noise of -133.4 dBc/Hz at a 1 MHz offset, a figure of merit (FoM) of -203.3 dBc/Hz, less than 41 dBm spurious harmonics, and a total VCO core current consumption of 1.18 mA from a 3.3 V voltage supply. To the authors' knowledge, this is the lowest phase noise variation ever reported. [ABSTRACT FROM AUTHOR]

A binomial low-pass filter provides the flattest passband response but, slow attenuation transition. This letter presents a design for improving the roll-off performance and reducing the size of the filter based on the negative-ℇ property of complementary split ring resonators (CSRRs), whilst maintaining the filter passband performance. The measured results indicate that the proposed structure achieves a flat pass-band with no ripples. Whilst also having a selectivity of 32 dB/GHz, which significantly exceeds the 17 dB/GHz selectivity of the conventional design. Furthermore, the proposed filter has reduced the filter size by 16%. © 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 2406–2409, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.22799 [ABSTRACT FROM AUTHOR]

In this work, we first screen print thin GO laminates on Kapton film and then chemically reduce to rGO with desired sheet resistance by controlling printing cycles and reduction time. The thin rGO laminates have a wide range of conductivity from 2.8 S m−1 up to 1.3 × 104 S m−1, exhibiting excellent consistency of electric performance even after 50000 times bending. Commonly used rGO reduction level characterization methods have been compared with the proposed sheet resistance method. It is revealed that the later has higher variation with reduction time, providing a new method for reduction monitoring of rGO. Benefiting from the tunability of its sheet resistance, the rGO laminate not only can be used in flexible electronic circuits as conductors or resistors, but also highly efficient to absorb microwave radiations with proper design. Therefore, a printed, three-layer, Jaumann structured microwave absorber has been designed, fabricated and characterised. The maximum microwave absorption rate is up to 99.9997% where the −10 dB fractional bandwidth is over 153%, which covers L, S and C bands. Moreover, the fabricated absorber can absorb efficiently even when the incident angle is as low as 20°. Full design procedure, simulation and measurement results are presented. [ABSTRACT FROM AUTHOR]