Sharif Digital Repository

A highly linear X-band low-noise amplifier (LNA) is proposed and implemented in a standard 0.18-μm CMOS technology. The LNA features both high and low-gain operation modes. In its normal high-gain mode, the LNA shows a small-signal gain of 13.6 dB with an IIP3 of +9.5 dBm and a noise figure of 4.7 dB. The two-stage amplifier draws 90 mA from the 3.3V power supply to achieve +14.8 dBm output P1dB (+2.2 dBm input P1dB). In the low-gain mode, the gain is reduced by about 10 dB to further enhance the linearity and to accommodate very large blockers. Accordingly, the input P1dB is enhanced to +13.7 dBm while the noise figure is increased by 8.1 dB. A technique is also introduced to maintain the... 

In this study, ternary MWCNTs/CoFe2O4/FeCo nanocomposite coated with conductive PEDOT-polyaniline (PA@MW/F/C) co-polymers were synthesized by microwave-assisted sol-gel followed in-situ polymerization methods. The phases, crystal structures, morphologies, magnetic and electromagnetic features of the as-prepared samples were identified via XRD, SEM, XPS, VSM, and VNA respectively. Absorption characteristics were investigated in the frequency (12–18 GHz) Ku band. XRD, VSM and SEM analysis confirmed the partial reduction process of CoFe2O4 and successfully decorated magneto-dielectric particles with co-polymers. By measuring electromagnetic features of the samples, it was found that coating... 

An inductorless low noise amplifier (LNA) with active balun for digital TV (DTV) applications is presented. The LNA exploits a noise cancellation technique which allows for simultaneous wide-band impedance matching and low noise design. The matching and amplifier stages in the LNA topology perform single-ended to differential signal conversion with balanced output. The second and third-order nonlinearity of the individual amplifiers as well as the distortion caused by the interaction between the stages are suppressed to achieve high IIP2 and IIP3. A method for intrinsic cancellation of the second-order interaction is employed to reduce the dependence of the IIP3 on the frequency spacing... 

The transformer-feedback (TRFB) interstage bandwidth enhancement technique for broadband multistage amplifiers is presented. Theory of the TRFB bandwidth enhancement and the design conditions for maximum bandwidth, maximally flat gain, and maximally flat group delay are provided. It is shown that the TRFB bandwidth enhancement can provide higher bandwidth compared to the conventional techniques based on reactive impedance matching networks. A three-stage low-noise amplifier (LNA) monolithic microwave integrated circuit with the TRFB between its consecutive stages is designed and implemented in a 0.1-μ m GaAs pHEMT process. The TRFB is realized by coupling between the drain bias lines of... 

A 6-bit passive phase shifter for 2.5- to 3.2-GHz frequency band has been designed and implemented in a standard 0.18- μm CMOS technology. A new switched-network topology has been proposed for implementing the 5.625 ° phase shift step. The insertion loss of the circuit is compensated with an on-chip bidirectional amplifier. The measured return losses of the circuit are better than 8 dB with output 1-dB compression point of +9.5 dBm in the transmit mode and noise figure of 7.1 dB in the receive mode. The fabricated phase shifter demonstrates an average rms phase error of less than 2° over the entire operation bandwidth, which makes it suitable for high-precision applications  

An analytical approach for design optimization of multi-stage LNAs with common source topology is developed. This paper reviews and analyses simultaneous noise and input impedance matching in three different topologies including common source amplifier with inductive degeneration, resistive feedback and dual feedback in order to achieve maximum available gain and minimum possible noise figure (NF). A study on multi-stage LNAs is performed to calculate optimum input impedance of each stage for minimum overall NF while considering the gain and NF of that stage in addition to the effect of noise of the following stages. MATLAB was used to calculate the starting point of design optimization in a... 

Carbon fiber (CF) as a multifunctional material with superb performance in aviation industry has serious drawback such as impedance mismatch which restricted the capability of using it as microwave absorber materials. In this research, a novel hierarchical carbon fiber@La0.7Sr0.3MnO@NiO (CF/LS/N) composite was facilely and successfully synthesized via sol-gel and subsequent hydrothermal reactions. The structural, morphological, magnetic and electromagnetic behavior of the composite were precisely evaluated via XRD, FESEM, XPS, VSM and VNA analysis. According to the systematic evaluation results, the synergistic positive effect of adding NiO nanoparticles is revealed in improving the... 

This paper offers a new EF-class converter for dynamic wireless power transfer application. The proposed high-frequency converter employs a floating-frequency switching algorithm to control the converter in a continuous frequency range, eliminate the requirement to any additional operational data from the secondary (receiver) side, accelerate the load impedance match while moving, maximize the transferred power rate, reduce charging interval and compensate power transfer tolerances. Moreover, an optimized super elliptical shape coil is designed to cope with lateral misalignment, enhance coil coupling, and increase efficiency. In the proposed converter, (i) soft switching is implemented to...