This paper reports on digital transmitter architecture for the 450 MHz band using an envelope delta-sigma modulator realized in CMOS and a voltage-mode class-S (VMCS) power amplifier (PA) based on GaN monolithic microwave integrated circuits (MMICs). The class-S PA is characterized for narrowband single-tone signals and a single- as well as a four-carrier downlink wideband code division multiple access (WCDMA) signal with a peak-to-average power ratio of 7.5 dB. Using single-tone excitation the PA shows a maximum drain efficiency of 86% and a peak output power of 4.4 W. At 6 and 10 dB back-off, 59 and 36% efficiency are achieved, respectively. With the single- and four-carrier WCDMA input signals maximum drain efficiencies of 64 and 53% are reached, respectively, and peak output power is 0.7 W. The adjacent channel leakage ratio shows values of about −34 dBc (5 MHz) and −38 dBc (10 MHz) for single-carrier WCDMA excitation. This is the first complete VMCS PA chain characterized with standard communication signals.

Electrodynamics models and radiophysical properties of carbon nanotube-dipoles (isolated on the substrate lattices), metallic optical antennas and optical antennas, formed from ZnO nanorods coated with metal films were developed and investigated. The models are based on numerically analytical solution of integrodifferential equations describing the diffraction of electromagnetic waves on impedance and dielectric bodies. The use of integral representations of the kernels of integrodifferential equations allowed us to overcome the difficulties of solution, associated with the singularity of kernels and to reduce the computation time by an order of magnitude.

In this work, the design of the wideband millimeter-wave power amplifier for multiband communication is presented. In order to achieve compact, simple and robust design, a differential cascade transformer-coupled topology is used. The amplifier is implemented in 90 nm low-leakage CMOS technology and achieves 3 dB bandwidth of 8 GHz (from 60 to 68 GHz) and a peak gain of 18 dB. The PO1dB is better than 5 dBm from 58 to 80 GHz, and peak output power is 11.9 dBm with 1 dB flatness from 62 to 77 GHz. The chip consumes an area of 0.25 mm2 including bond pads and DC current of 125 mA from a 2.2 V supply.

In this paper, a new compact hybrid fractal antenna with ultrawideband (UWB) behavior is proposed. Two merged fractals shapes, i.e. Sierpinski carpet and Sierpinski Gasket fed with coplanar waveguide (CPW) feed make patch as multiband and broadband antenna. The antenna is optimized using particle swarm optimization for side length of Sierpenski Gasket fractal and bandwidth. The overall width of the patch is taken as a parameter for optimizing bandwidth. The total size of presented antenna is 59 × 29 mm2. The antenna resonates at 2–5.2 GHz, so that wideband operation is observed. Antenna with this type of characteristics can be used when UWB response at lower frequencies is required. Sierpenski Gasket performs two functions in the proposed design, i.e. to radiate as well as impedance transformer to Sierpenski carpet. The proposed design presents novelty in design to achieve proper impedance matching to edge of Sierpenski carpet design with CPW feed by making Sierpenski Gasket as impedance transformer.

This paper presents and discusses two possible real-time digital predistortion (DPD) architectures suitable for envelope tracking (ET) power amplifiers (PAs) oriented at a final computationally efficient implementation in a field programmable gate array (FPGA) device. In ET systems, by using a shaping function is possible to modulate the supply voltage according to different criteria. One possibility is to use slower versions of the original RF signal's envelope in order to relax the slew-rate (SR) and bandwidth (BW) requirements of the envelope amplifier (EA) or drain modulator. The nonlinear distortion that arises when performing ET with a supply voltage signal that follows both the original and the slow envelope will be presented, as well as the DPD function capable of compensating for these unwanted effects. Finally, two different approaches for efficiently implementing the DPD functions, a polynomial-based and a look-up table-based, will be discussed.

Broadcasting is an inevitable operation in networks. This paper addresses the issues related to broadcasting such as node interference and latency delay in ad-hoc networks .These problems could be overcome by our proposed algorithm approximate directional routing protocol (ADRP) which is mainly inspired by the existing on-demand directional routing protocol (DRP). DRP is also similar to Dynamic Source Routing (DSR). The use of directional antennas for broadcasting is gaining acceptance in ad-hoc networks. The key benefits of smart antennas are minimum energy consumption and bandwidth conservation. Although excess of literature is directed toward the use of smart antennas, a powerful protocol for reducing redundancy, end-to-end delay, and interference is being researched. One such protocol is ADRP. ADRP is a reactive protocol that combines the effect of DRP and approximation algorithm that finds optimal solution for broadcast problems. Omni-directional antennas are capable of wide angle signal transmission. Compared with omni-directional antennas, its successor directional antennas have come up with significant advantages of reducing packet redundancy and interference by gaining higher signal-to-noise ratio. The duo pack will considerably decrease end-to-end delay and node interference giving out significant performance benefits thereby substantially increasing throughput.

This paper reports design and successful development of new and high performance transmit and receive feed systems for reflector antennas at “lower-extended C-band”. The horns are analyzed and optimized using the mode-matching technique-based software CHAMP. Other feed components are designed with the aid of the mode-matching technique and finite element method based softwares viz. MICIAN and HFSS. The predicted radio frequency (rf) performances comply with the measured results with small deviation. Some issues related to feed system such as impact of horn outer structure; such as base for tooling ball, feed bracket for struts etc. on its rf performance are discussed. It is shown that the outer feed structure plays a significant role apart from the internal cavity of the horn for prediction of electrical performance of the feed system. Besides high rf performance; good mechanical properties such as compactness and ease to fabrication are achieved through innovative feed design.

A millimeter-wave monolithic integrated circuit consisting of a W-band (75–100 GHz) single-pole-five-throw (SP5T) switch and multiple internal active and passive loads for radiometer calibration was designed and manufactured in a low noise 50 nm GaAs metamorphic high electron mobility transistor technology. This highly compact and integrated front-end device for radiometer systems is capable of ultra fast switching between two identical input ports (e.g. for polarimetric applications) and three internal calibration references. It allows an accurate multi-load calibration with noise temperatures between 220 and 1750 K at the output of the device. Compared to conventional calibration methods this marks a substantial advantage in terms of size, mass, power consumption, complexity, and repetition rate.

Fourth generation mobiles require multi-standard operating handsets with small physical size as well as increasing demand for higher data rates. Compact multi-band printed inverted-F antennas (IFA) for available wireless communications are proposed in this paper. New design of printed IFA based on uniplanar compact electromagnetic band-gap (EBG) structure concept is proposed. A printed-IFA with L-load shaped over an artificial ground plane is designed as the main antenna to cover most wireless applications such as GSM, LTE, UMTS, Bluetooth, Wimax, and WLAN. The multi-band is created by means of an EBG structure that is used as a ground plane. Different shapes of uniplanar EBG such as ring, split ring resonator, and spiral rather than mushroom-like structure are investigated. The proposed antenna is built on the uniplanar EBG ground plane with size of 35 × 45 mm2, which is suitable for most of the mobile devices.

In this paper, optimization of a microstrip patch antenna is presented. The optimization uses a genetic algorithm in the IE3DTM Simulator. The optimization is done in several steps, first by changing the position of parasitic patches on the top layer, second by placing a feeding patch at the middle layer of geometry, and third by indirect coupling between the top and middle layer patches. Overall, we have performed many possible iterations and found appropriate geometry. From this appropriate geometry we have achieved maximum directional gain (6.2–8.8 dBi) over a 6 GHz bandwidth slot, 38% impedance bandwidth of the X-band and 14.8% impedance bandwidth of the Ku-band. The broadband frequency of operation is demonstrated by single geometry. The geometry of a single probe fed rectangular microstrip antenna incorporating a slot, gap coupled with a parasitic and an active patch on geometry, has been studied. We have investigated the height between active and parasitic patches as 0.0525λ and the height between parasitic patches itself as 0.0525λ. We have investigated the enhancement in maximum directional gain by stacking geometry with one active patch and two parasitic patches of different dimensions. This optimized antenna is used for X-band and Ku-band applications. The hardware validation and simulation results are matched to the proposed design.

In this paper, we present a non-resonant high impedance reflectometer with a reference impedance close to one of the tip probe of a near-field microwave microscope. We show that for an apex of the tip probe of 100 µm there is an optimum reference impedance close to 1 kΩ. To validate this approach a microwave circuit that makes use of lumped elements has been fabricated. A proof of concept is also explored for capacitance measurements between the tip probe and a metal plate.

A general purpose two-channel Frequency modulated continuous wave (FMCW)-sensor in E-band is extended to a digital-beam-forming (DBF) system. The hardware extension contains a transmit multiplexer, which allows switching of the (DBF) transmit signal of the sensor to any of 32 linearly arranged waveguide antennae. To maintain the spatial sampling condition by λ/2 element distance, the antenna ports are arranged in the E-plane. The ports can directly radiate or serve as primary radiators of a cylindrical dielectric lens focusing in the H-plane. By realizing the hardware extension based on a metal-backed substrate, some novel radio frequency (RF) structures became necessary. One of these structures is a special twisting microstrip-to-waveguide-transition to connect the switching matrix to waveguide ports arranged in the E-plane. Key elements of the multiplexer are commercially available pin-diode-based MMIC-switches in microstrip technology. To lower the inductance of the interconnects, they are embedded in cavities in the metal-backed RF-substrate. RF interconnects between the sensor and the extension are all done with waveguide ports. Further interconnects between the module and the extension are low-frequency or digital and are led via cables and removable plugs. Both module and extension can be powered separately. This gives an easily mountable extension for making a two-dimensional (2D) DBF sensor out of a 1D FMCW-sensor.

A large-signal model and a simulation technique based on non-sinusoidal voltage excitation are used to obtain the electric field snapshots from which the series resistance and related high-frequency properties of a 35 GHz Silicon Single-Drift Region (SDR) Impact Avalanche Transit Time (IMPATT) device have been estimated for different bias current densities. A novel method is proposed in this paper to determine the parasitic series resistance of a millimeter-wave IMPATT device from large-signal electric field snapshots at different phase angles of a full cycle of steady-state oscillation. The method is based on the depletion width modulation of the device under a large-signal condition. The series resistance of the device is also obtained from the large-signal admittance characteristics at threshold frequency. The values of series resistance of a 35 GHz SDR IMPATT diode obtained from the proposed method and the large-signal admittance method are compared with experimentally reported values. The results show that the proposed method provides better and closer agreement with the experimental value.