In this study, we design a differential CMOS power amplifier using a 180-nm SOI RFCMOS process for 802.11n (64-QAM, 20 MHz bandwidth, 9.6 dB peak to average power ratio (PAPR)) applications. To minimize the chip area and mismatch in differential signals, we propose a layout method with an inter-stage matching network using a split inductor. By virtue of the symmetrical layout of the proposed split inductor, the mismatch in the differential signals is minimized, while the interconnection lines between the driver and power stages are shortened to minimize the overall chip area and the loss induced by the resistive parasitic components. The designed power amplifier is measured using a wireless local area network (WLAN) 802.11n signal to verify the feasibility of the proposed layout technique. The power amplifier achieved 20.34 dBm output power, while the measured EVM for the 802.11n applications is satisfied. From the measured results, we successfully prove the feasibility of the proposed power amplifier.

In building highly efficient transmitters of today, one is forced to sacrifice linearity for efficiency. Some of the highest power amplifier efficiency figures are reported by envelope tracking (ET) amplifiers. These amplifiers can generate strong higher-order harmonics, which can lead to interference with receivers operating at the harmonic frequencies. Using non-linear interference cancellation, we can help to remove the interference being caused in those receivers. This paper looks at the problem of modeling the third and second-order harmonic emission from an ET amplifier. It derives the non-linear kernel for estimating such interference. This kernel has been rigorously expanded to show its correlation with the various harmonics and its effectiveness in predicting the harmonic content. We then set up an envelope amplifier test-bench to capture harmonic signal content and cancel it using the derived kernel model. The experiment yields excellent agreement with theory and provides a validation of the system and concept.

A new design of reconfigurable sub-nanosecond pulse generator (PG) with pulse shape selection ability is presented in this paper. Step recovery diode is used as the pulse sharpening device and the pulse shaping circuit consists of a controllable RC differentiator in which a single PIN diode is embedded, which provides two different switchable pulse shaping performances. The realized PG has a compact (10 × 12 mm2) simple structure and is easy to implement while generating Gaussian and monocycle pulses with 510 and 660 ps pulse width, respectively. The proposed pulse shaping method is versatile and can be effectively modified and reconfigured to generate more complicated pulse shapes such as polycycle signals. The measured results reveal that the proposed reconfigurable PG is suitable to be used in systems with pulse shape modulation that require sub-nanosecond pulses at low pulse repetition rates.

In this paper, the structure of a common field-effect transistor (FET)-based negative impedance converter (NIC) that behaves as a negative capacitor is presented. The nonlinear modeling, analysis, and simulation of this non-Foster structure are presented in the time domain and the transient response of the circuit can be used to study the stability of the circuit. For the analysis of the circuit performance, the linear time-dependent modeling approach is used. This method is based on determination of the circuit parameters at each step according to parameters of the previous steps, bias voltages, and the input signal. Results of the proposed method for analysis of non-Foster circuit are compared with those of nonlinear analysis using commercial software, which shows a good agreement together and the proposed method is validated. Based on the analysis, the nonlinear capacitance of non-Foster circuit is extracted and based on the simple second order model of current source of FET, the analytic model of negative capacitor is extracted and improved by curve fitting. The proposed model results have a good agreement with simulation results of NIC's circuit.

The development of compact radio frequency identification (RFID) tag is the key requirement for wireless tracking of precious small size goods/packages in transport. A design of compact meander line tag antenna having inductive coupling feed is presented for RFID system operating at ultra high frequency band of 865–867 MHz. The size of the proposed tag antenna is 43 mm × 10 mm, and is designed using Higgs 4 IC chip (made Alien Technology, USA) having impedance of 20.55 − j191.45 Ω at centre frequency 866 MHz. The antenna characteristics such as impedance, radiation pattern, bandwidth, and effect of ground on gain and tag size are analyzed and found to closely match with the simulated values. The observed value of reading range varies from 87.5 to 35 cms depending on mounting on non-metal and metal packages, respectively.

This paper presents a simple reconfigurable bandpass filter switching from 2.4 to 5 GHz based on PIN diodes. The proposed filter is intended to add frequency-tunability to antenna systems used in cognitive radio applications. It consists of a bent connecting stub with two open-circuited quarter-wave stubs grounded via PIN diodes. By controlling the didoes states, the electrical length of the stubs can be switched from quarter-wave to half-wave and vice versa, so as to tune the filter center frequency. The proposed design approach consists of ensuring communication at 2.4 GHz while blocking the 5 GHz band in the ON state, whereas in the OFF state, the filter is intended to reject the 2.4 GHz band and passing the 5 GHz band. A prototype of the proposed filter is fabricated and measured to validate the proposed concept. Both simulated and measured results show a two-state filter with a wide tuning range from 2.4 to 5 GHz and a good stopband rejection level better than 40 dB. Moreover, a flat group delay of about 0.55–0.7 ns is achieved within the operating bandwidth in both states. The proposed filter is able to achieve simultaneous bandwidth and frequency control, showing an important tool to meet modern system requirements.

This paper presents a wideband band-stop filter (BSF) structure designed by using planar technology. The proposed filter consists of a modified conventional band-stop structure with open stubs, inner T-inverted shape, and two input/output feed lines. Based on series of optimization and a specific design method, two compact filters with good electrical performance are obtained. In order to characterize the frequency response of the proposed filters, the performance is carried out numerically using two different solvers (Advanced Design System -Momentum and CST-MWS). Furthermore, in order to validate the conception approach, two circuits are designed, fabricated, and tested. Additionally, an equivalent circuit of the wideband BSF is built to estimate the electromagnetic simulation results for practical realization. The features of the design have a reduced size, wideband rejection, and higher insertion losses, which can be performed by adjusting the L-shaped stubs (23.25 × 2.2 mm2) toward the 50 Ω input and output ports. Two filters are designed, fabricated, and tested; one can be operated between an fractional bandwidth (FBW) of about 50% at a center frequency of 1.8 GHz, and the other can be switched from an FBW of 43.38% at a center frequency of 1.82 GHz. In addition, good agreement between the simulation and the measured results is achieved. The overall size of each filter is 43.4 × 34.5 mm2.

We review the main results of the development of whispering gallery mode (WGM) resonators and their unique applications due to their quasi-optical functionality. Several types of advanced WGM resonators are proposed by the authors. The theoretical results are described for the resonators with an analytical solution of the electromagnetic problems. Special emphasis is given to the interaction of moving charged particles and waves of cylindrical resonators. Important aspects are described concerning the developed sapphire resonators, for which an exact solution can only be found by using specially designed computer program products. A separate section of the paper is devoted to application aspects of the WGM resonators. In particular, it describes advanced solutions for overcoming the problems of measuring the small microwave (MW) surface impedance of unconventional superconductors in the form of large-area thin films and small samples under study. In addition, a demonstration of accurate complex permittivity measurements of small volumes of lossy liquids is provided. Special emphasis is given to highly stable MW signal sources, namely Ka-band transistor-based feedback oscillator and solid-state maser WGM oscillators. Recently obtained results are presented of experimental studies of the auto-oscillatory system developed on the basis of the WGM resonator with relativistic electron beam.

This paper presents the design of a size miniaturized and harmonic suppressed wideband double-section rat-race coupler (RRC). Series and shunt stepped-impedance transmission line units are proposed to replace the quarter wavelength transmission lines in the conventional design of wideband (50% fractional bandwidth) two-stage rat-race coupler. Design equations are derived using the lossless transmission line model. The proposed double-section RRC occupies only 14% area of the conventional coupler, with good return loss and isolation performances. In addition, the full-wave simulation and measured responses exhibit harmonic suppression up to at least fifth harmonic. The proposed design can be easily implemented using the standard printed circuit board etching process without any via-holes, bonding wires, and lumped elements, which make it very useful for wireless communication systems

This paper presents an extension of the formulation of wave propagation in transverse electric (TE) and transverse magnetic (TM) modes in the case of metallic circular waveguides filled with anisotropic metamaterials. The determined higher-order modes have been analyzed and exploited to the design of filters. Among the particularities of anisotropic material, the backward waves can propagate below the cut-off frequency. The numerical results for TE and TM modes have been compared with theoretical predictions. Good agreements were obtained. We analyzed a periodic structure containing waveguides filled with anisotropic metamaterial using the mode-matching technique. By using modal analysis, our approach reduced considerably the computation time compared to HFSS.

Broadband transitions are presented in this paper for capacitively grounded coplanar waveguide to coupled microstrip (CMS) lines. These transitions are realized on both thick Rogers RO3003 substrate (thickness of 10 mils) and a thin benzocyclobutene (BCB) polymer film (thickness of 20 µm). A flat bandwidth of 4–20 GHz and 3.2 to over 40 GHz are measured for the RO3003 and BCB polymer substrates, respectively. These performances are obtained without making via-hole in the substrate or patterning the bottom ground plane, which makes this broadband transition easier to fabricate compared with the via-hole-based grounded CPW–CMS transitions.

In this paper, we demonstrate the successful implementation of an onwafer noise parameters test set that employs an extended six-port network and a conventional noise figure analyzer. The necessary formulation that enables the calibration of the noise parameter test set as well as extraction of the noise wave correlation matrix of a two-port device under test (DUT) was tested for coaxial connector-type DUT measurement in an earlier work but not for onwafer-type DUT. Furthermore, we demonstrate the performance of this technique against data obtained from the well-known tuner method. Measurement carried out for very low-noise figure (2 dB) onwafer-type amplifier demonstrates the capability of our technique. The measured noise parameters show fluctuations in minimum noise figure, NFmin of ±0.1 dB, and in noise resistance Rn of about 2%. This test set is simple and fast leading to tremendous time- and cost-savings as well as a simplified procedure in onwafer noise parameters measurements.

A new Ku-band reflectarray with an artificial anisotropic slab that consists of periodic holes, backed by a planar artificial magnetic conductor (AMC) is proposed. The unit-cell of the reflectarray is a two-layered structure that consists of a dielectric with a hole on a grounded patch. The phase diagram of the proposed unit-cell is calculated by a full-wave computational technique, which uses the dyadic Green's function evaluated by an equivalent transmission line modeling in the spectral domain. The obtained dyadic Green's function is used in an integral equation formulated for the surface current densities on the metallic grating. The resultant integral equation is then solved using the method of moments. The required phase shift at Ku-band is obtained by changing the radius of holes in the artificial slab. The introduced unit cell has linear phase range between 13.95 and 14.95 GHz. It is shown that this frequency band is the usable bandwidth of AMC structure. Finally, the designed reflectarray is analyzed using a full-wave electromagnetic solver. The numerical results show a maximum gain of 27.4 dBi, and 48.09% efficiency, at 14.45 GHz with 4.15% 1-dB gain bandwidth for the designed 21 × 21 cm2 reflectarray.

The design and measurement of reconfigurable circularly polarized capacitive fed microstrip antenna are presented. Small isosceles right angle triangular sections are removed from diagonally opposite corners for the generation of circular polarization (CP) of axial ratio bandwidth of 11.1%. Horizontal slits of different lengths are inserted at the edges of the truncated patch to provide the dual-band CP and by switching PIN diodes across the slits ON and OFF, reconfigurable circularly polarized antenna is realized. The antenna shows dual-band behavior with reconfigurable CP. In order to enhance the operation bandwidth of the antenna, an inclined slot was embedded on the patch along with PIN diodes across the horizontal slits. This proposed antenna gave an impedance bandwidth of 66.61% (ON state) ranging from 4.42 to 8.80 GHz and 68.42% (OFF state) ranging from 4.12 to 8.91 GHz and exhibits dual-frequency CP with PIN diode in OFF state and single-frequency CP with PIN diode in ON state with good axial ratio bandwidth. The axial ratio bandwidth of 4.42, 2.35, and 2.72% is obtained from the antenna. The antenna has a similar radiation pattern in all the three different CP bands and almost constant gain within the bands of CP operation.

This paper presents the behavior of three iterations of a coplanar waveguide fed CANTOR Set fractal antenna. This kind of antennas allows having a broadband behavior and important gains. Also, the setup of slots allows having more lower resonant frequencies and therefore designing miniaturized antennas with good performances. The proposed antennas are suitable for 2.5/3.3/5/5.5 GHz worldwide interoperability for microwave access and for 2.4–2.5/4.9–5.9 GHz wireless local area networks applications. The simulations were performed in FEKO 6.3. The measurements were performed with Vector Network Analyzer HP 8719C.

A microstrip transmission line fed fork-shaped planar antenna is proposed for Bluetooth, WLAN, and WiMAX applications. The antenna made of a microstrip feed line, fork-shape patch on one side and defected ground plane on the other side of dielectric substrate. A fork-shape is formed by two side circular arms and a rectangular central arm. The inverted T-shaped ground plane with a rectangular slot in the center arm is used to increase the bandwidth with better impedance matching of the lower band. The antenna is practically fabricated to validate the design. The antenna resonate dual band to cover an entire the WLAN and WiMAX bands. The antenna shows the measured bandwidth of 410 MHz (2.26–2.67) and 3.78 GHz (3.0–6.78 GHz) at lower and upper bands, respectively.

Compact modified T-slot circular patch antenna for multiple input multiple output (MIMO) applications, which has good response for four operating frequency bands is developed. Here the design consists of a circular patch with a new slot loaded T- shape on one side of the substrate and a feeder line on the other side of the substrate. A shorting pin is located between the patch and the feeder line. This proposed antenna resonates at the frequencies of 2, 4.8, 5.4, and 6.2 GHz covering the S-band, C-band, and LTE applications. The independent tuning of frequency bands is achieved by varying the length of the slots. By independent tuning of frequency bands, the selection of interested frequency band is achieved. The single element with miniaturized size of 1.945λ × 1.945 λ (30 × 30 mm2) is achieved including the feed line. The antenna has been tested for MIMO applications. The measured envelope correlation coefficient between the two elements, which are spaced 0.139 λ is <0.1(low correlation) and mutual coupling is found to be in the range of −20 dB to −80 dB. The simulation and measurement results of reflection coefficient, mutual coupling, and radiation pattern are presented.

This paper presents the design of a split-ring resonators (SRR) loaded coplanar waveguide-fed ultra-wide band (UWB) antenna. As using the electromagnetic coupling SRR connected by open-ended microstrip lines, this UWB antenna achieves wide band-notched characteristics. The frequency of the proposed antenna operates from 2.37 to 10.93 GHz with a broad notch band covers from 4.96 to 6.15 GHz (IEEE 802.11.ac), the relative stopped bandwidth of the notch band achieves 20.42%. Besides, theoretical analysis and experimental results are proposed to illustrate and validate this proposed antenna.

A probe feed wideband multi-element dual segments quarter cylindrical dielectric resonator antenna (q-CDRA) in composite forms have been proposed. The q-CDRA has been introduced by splitting CDRA into four uniform quarters and multi-segmentation approach has been castoff for further improvement in bandwidth of q-CDRA. The dual segments q-CDRA has been designed and analyzed using theoretical analysis and Ansoft HFSS simulation software. Further the dual segment multi-element q-CDRAs in composite form have been designed. A coaxial probe has been placed at the center of the ground plane for the excitation of proposed multi-element and multi-segmented composite form of q-CDRA, which excite TM01δ mode in the proposed antenna. The input characteristics and radiation patterns of the proposed composite antennas have been studied and their results are compared with corresponding experimental results. Prototype of single, two, and four elements dual-segment composite q-CDRAs have been fabricated and input characteristics of the proposed composite antennas have been compared with each other. Four elements dual-segment composite q-CDRA has shown wide impedance bandwidth (|S11| ≤ −10 dB) of 85.13% with monopole-like radiation pattern. The peak gain of 4.85 dBi with 98.5% radiation efficiency has been achieved for dual-segment four elements composite q-CDRA. The proposed multi-element dual-segment composite q-CDRAs may find suitable applications in C and X-band with complete covering of the 5.0 GHZ wireless local area network (WLAN) and worldwide interoperability for microwave access (WiMAX) band.

In this paper, combination of electromagnetic band gap (EBG) and split-ring resonator (SRR) loads with fractal formation for miniaturization of microstrip antenna is noticed. Here two different shapes of antenna have been studied with two well-known metamaterial structures as parasitic elements. A conventional microstrip antenna, which is surrounded by four EBG unit cells, is chosen as the first antenna. It has an effective resonance at 2.5. The Minkowski fractal method is applied to EBG unit cells in this stage. The Minkowski fractal structure is implemented for accession of effective capacitance in EBG unit cells. The second antenna frequencies are 2.5 and 5.9 GHz. It contains a slot structure with four SRRs, used for making parasitic elements and for achieving multi-band characteristic. The fractal method is used to improve the inductance of SRR structure by increasing the effective length of microstrip line. At this stage, the applied fractal structure has been modified, so that the frequency of wireless application could be achieved. In the last step, by some changes in feed line of the slot antenna, circular polarization (CP) is obtained for the second antenna, which shows that SRR load can be helpful for making the CP.