Munir A. Tarar

A direct down-conversion receiver for coherent extraction of digital baseband signals using the injection locked oscillators

In todays digital wireless communications direct down-conversion receiver is becoming a favorite choice due to its overall simplicity and low cost. However, carrier recovery of the received digitally modulated RF signal for clear IQ signal extraction at high symbol rates is not so simple. Until now, phase-locked loop (PLL) and/or direct-digital synthesizers (DDS) or combination of both have been used for better performance but at the expense of high complexity or cost. In this paper for the first time we propose a direct down- conversion receiver that uses an injection-locked oscillator (ILO) for carrier recovery and frequency synthesizing. The results are shown for carrier recovery of a 2.1 GHz 20 Msps 8 PSK signal and coherent demodulation of a 2.78 GHz 160 Msps QPSK signal. The receiver presented is of low-cost and low-complexity and applicable to any kind of digitally modulated signals reception. It can be used in many wireless applications as WiMax, RFID and sensor networks.

Design of Dual Band Wearable Antenna Using Metamaterials

Abstract This paper presents two types of dual band (2.4 and 5.8 GHz) wearable planar dipole antennas, one printed on a conventional substrate and the other on a two-dimensional metamaterial surface (Electromagnetic Bandgap (EBG) structure). The operation of both antennas is investigated and compared under different bending conditions (in E and H-planes) around human arm and leg of different radii. A dual band, Electromagnetic Band Gap (EBG) structure on a wearable substrate is used as a high impedance surface to control the Specific Absorption Rate (SAR) as well as to improve the antenna gain up to 4.45 dBi. The EBG inspired antenna has reduced the SAR effects on human body to a safe level (<2W/Kg). I.e. the SAR is reduced by 83.3% for lower band and 92.8% for higher band as compared to the conventional antenna. The proposed antenna can be used for wearable applications with least health hazard to human body in Industrial, Scientific and Medical (ISM) band (2.4 GHz, 5.2 GHz) applications. The antennas on human body are simulated and analyzed in CST Microwave Studio (CST MWS).

Textile antenna for body centric WiMAX and WLAN applications

Body centric wireless communication refers to inter human and intra human connectivity for various medical and rescue application. A compact and flexible printed textile antenna operable at 5.2GHz for WiMAX and WLAN application has been presented. Wearable 1mm thick blue jeans having relative permittivity 1.67 and loss tangent of 0.01 has been used as substrate material. Return loss, VSWR and radiation pattern have been presented to show the good agreement between the simulated and measured results. Free space and near body scenarios were considered separately while designing and in measurement of results. The proposed antenna exhibits omnidirectional radiation pattern for near body case with suitable gain of 5dB for body centric applications. Simulations were carried out using HFSS (High Frequency Structural Simulator) and measurements were performed using vector network analyzer and anechoic chamber.

Injection-Locked Phase-Locked Loop for BPSK Coherent Demodulation: Theory and Design

In this paper for the first time the use of injection-locked phase-locked loop (ILPLL) for the BPSK to ASK coherent conversion is explored. Two circuit architectures are proposed, one using two second-harmonic ILPLL (SH-ILPLL) and the other using a single SH-ILPLL. In the case of two SH-ILPLL, feedback loop amplifiers are used and an increase of 20 times in the locking range of the converter is achieved. In the case of the single SH-ILPLL, direct BPSK to ASK conversion is also achieved but found with smaller locking and dynamic ranges. However, it is very simple and easy to develop. With the addition of an envelop detector, both circuit architectures can be used as a complete and compact RF front-end receiver that can direct demodulate digital RF/microwave signals without many intermediate components and devices. Such a low-cost and low-complexity receiver can be employed in many wireless applications such as RFID and sensor networks.

Recent Progress of ILO-Based Novel Synchronization Techniques for Transceivers Used in Broadband Wireless Communication Systems

To deliver data at hundreds of megabits per sec over wireless media with high accuracy requires high signal acquisition and synchronization speeds. Many techniques have been developed in the past and choice of a right synchronization technique has become user and application specific. In this paper, we present our recent progress on the development of synchronization techniques, first, by reviewing the present techniques and then by presenting our work on using injection-locked techniques. Our work include the second-harmonic injection-locked phase-locked loop (SH-ILPLL) for BPSK signal demodulation with wide locking range, a single-frequency ILO for high speed 160 Msps QPSK detection and a selectable frequency dielectric resonator oscillator (SF-DR-ILO) based synchronization for coherent demodulation of multi-frequency QPSK signals of up to 63Msps. Our novel synchronization techniques can be used for modern communication systems such as WiMax or UWB applications. They can also be used for a fixed frequency or multiple-frequency high data rate video transmission over the indoor reciprocal channel.

A triple-band antenna array for next-generation wireless and satellite-based applications

In this paper, a triple-band 1 × 2 and 1 × 4 microstrip patch antenna array for next-generation wireless and satellite-based applications are presented. The targeted frequency bands are 3.6, 5.2 and 6.7 GHz, respectively. Simple design procedures and optimization techniques are discussed to achieve better antenna performance. The antenna is designed and simulated using Agilent ADS Momentum using FR4 substrate (e r = 4.2 and h = 1.66 mm). The main patch of the antenna is designed for 3.6 GHz operation. A hybrid feed technique is used for antenna arrays with quarter-wave transformer-based network to match the impedance from the feed-point to the antenna to 50 Ω. The antenna is optimized to resonate at triple-bands by using two symmetrical slits. The single-element triple-band antenna is fabricated and characterized, and a comparison between the simulated and measured antenna is presented. The achieved simulated impedance bandwidths/gains for the 1 × 2 array are 1.67%/7.75, 1.06%/7.7, and 1.65%/9.4 dBi and for 1 × 4 array are 1.67%/10.2, 1.45%/8.2, and 1.05%/10 dBi for 3.6, 5.2, and 6.7 GHz bands, respectively, which are very practical. These antenna arrays can also be used for advanced antenna beam-steering systems.

Signal analysis, design methodolgy, and modular development of a TR module for phased array radars

Phased array radars have received considerable importance both in commercial and defense communications. Lot of research has been carried out regarding development of its necessary components such as the antenna array, transmit/receive module (TRM) and processor unit. The cost, efficiency, wide bandwidth, and fabrication technology for the TRM have been pursued as key research areas. Cost reduction techniques till date have focused on the use of high tech MMIC fabrication techniques. Literature lacks in guiding a novice design engineer working on TRM in a cost effective manner. This paper presents mathematical analysis of signals processed in a TRM to enable a design engineer understand the constraints involved in the system design. The behavioral simulation, at 2.0 GHz, of TR module has been performed and, simulated results of phase shifter and TR switch sub-modules are also presented. Detailed system simulation is performed using lumped components for cost effective implementation in a lab environment. The results depict a close realization of the mathematical formulation.

Analysis, design, and simulation of phased array radar front-end

Phased array technology has brought revolution not only in the defense but also in the commercial industry. Considering the development taking place in this area, it can be safely said that the future belongs to the phased array technology. This paper presents system level modeling and integration of the front end of phased array radar. This includes the modeling and simulation of an antenna array, transceiver (TR) module and the target detection. Concept of beam formation and steering is also explained with the help of simulation. The system level modeling is carried out in Advance Design System (ADS) and Momentum — an Electromagnetic (EM) tool of ADS. An effort in the simulations is made towards the realization, understanding and highlighting the challenges involved in the practical implementation of the system.

The Implementation of a New All-Digital Phase-Locked Loop on an FPGA and Its Testing in a Complete Wireless Transceiver Architecture

In this paper a novel user-friendly implementation of an all-digital phase-locked loop (ADPLL) is presented.Its novelty lies in the fact that the very basic functions of the ADPLL are kept in the top module Verilog file.Against the normal design practice, all of the main math functions were implemented using the sub-modules placed outside but called from within the top module.This way ADPLL can be easily implemented in a low-cost FPGA. Further, the implementation details of an ADPLL, which are not reported previously in a singles hot, are described altogether for the first time. The reconfigurable ADPLL is then implemented in a transceiver architecture and tested with real signals received wirelessly. The recovered IQ constellation EVM of 9.0336% was obtained, which is quite practical.This proves the feasibility of the ADPLL not only in simulations but in a real communication system. The ADPLL designed this way can be used in any communication system, although preferably for high data rate transceiver applications.

A multi-channel wideband direct-conversion receiver using synchronization signal from a tunable injection locked oscillator

Synchronization is a challenging issue facing industrial designers that has not been researched often by academic researchers. The conventional techniques are phase-locked loop (PLL), digital PLL, or direct-digital synthesis (DDS). With any one or a combination of these techniques, high performance can be achieved at the expense of complexity or cost. In this paper, another technique, the injection locking technique, is explored to provide synchronization for a direct-conversion receiver. More specifically, signal synchronization is achieved with a selectable dielectric-resonator injection locked oscillator (DRILO) designed at a free running frequency of 3.634 GHz. The receiver developed was able to recover the carrier and IQ signals from 3.58 GHz, 3.63 GHz and 3.69 GHz with 50 Msps to 63 Msps QPSK modulated signals. The receiver designed as such is novel and simple, and can find applications in many modern communications such as WiMax. It can also overcome frequency synchronization problems faced in OFDM systems.