A novel technique to improve gain in transparent UWB antennas

A novel technique to improve the performance of AgHT-8 transparent polymer antennas is proposed in this paper. A spit-ring resonator is introduced on the radiating patch to enhance gain. The resonator basically concentrates the radiating energy to the central area of the patch thus improving gain. The designed antenna demonstrates good gain while maintaining the original transparency of the material. Such an antenna inscribed on the commercially available AgHT-8 sun shielding film material makes it a viable option for wireless applications like in-house base stations and applications requiring fast data rate transfers which can be mounted on windows and glass panels. © 2011 IEEE.Solutia Inc., St. Louis, Missouri, US

Design of 5 th-order analog predistorter

This paper presents the design of a 5th-order analog predistorter to suppress the 3rd-and 5th-order intermodulation distortion products (EVTDP3 and EVTDP5) at the output of a base-station power amplifiers (PAs). The predistorter consists of two mixers: one mixer generating the 3rd-order intermodulation (IM3) products and another mixer of same configuration generating the 5th-order intermodulation (IM5) products using the IM3 products generated by the other mixer, thus simplifying the design and hardware implementation. The predistorter is implemented and tested using two-tone and the CDMA (IS-95) signals at 2.2GHz in a practical 10W-PA. The two-tone test results show that the proposed predistorter can suppress the IMDP3 and IMDP5 by 17dB and lldB, respectively. For the CDMA (IS-95) test, results show that the predistorter can improve the adjacent channel power ratio (ACPR) by 10 dB at ± 887 kHz from the center frequency. © 2010 IEEE.published_or_final_versionThe 2010 IEEE Region 10 International Conference (TENCON 2010), Fukuoka, Japan, 21-24 November 2010. In TENCON (IEEE Region 10 Conference) Proceedings, 2010, p. 876-87

Effects of ground-plane size on planar UWB monopole antenna

Planar monopole antennas have found widespread applications in wireless communication systems. Their advantages of compact size, omnidirectional radiation pattern and wide impedance bandwidth make them good candidates for the designs of ultra-wideband (UWB) antennas. This paper investigates the effects of the dimensions of the rectangular ground-plane on the return loss and efficiency of an elliptical planar monopole antenna for UWB applications. Computer simulation and measurement are carried out on a group of nine antennas with different rectangular ground plane sizes. The simulated and measured results on return loss agree well. However, the simulated and measured efficiencies do not agree well in the lower UWB band. The measured efficiency shows that the efficiency is affected more by the width rather than by the length of the ground plane while the length of the ground plane affects the lower cutoff frequency. © 2010 IEEE.published_or_final_versionThe 2010 IEEE Region 10 International Conference (TENCON 2010), Fukuoka, Japan, 21-24 November 2010. In TENCON (IEEE Region 10 Conference) Proceedings, 2010, p. 422-42

A compact 6-bit phase shifter with high-power capacity based on composite right/left-handed transmission line

The EuMC 2010 Conference was one of the 4 conferences held during the 13th European Microwave Week (EuMW2010): "Connecting the World", Paris, France, 26 September-1 October 2010A compact 6-bit phase shifter with high power-handling capacity is designed based on the use of metamaterial, composite right/left-handed transmission line (CRLH-TL). Eight PIN diodes mounted on the fingers of the CRLH-TL are used as switches to control the phase incursion of the input signal. Different phase shifts are achieved by using different states of the switches (PIN diodes) determined by 6 controlling bits. Since the surface current flowing through each of the switches is only a fraction of the total current through the device, the power handled by each of the PIN diodes is much smaller than the total power through the device; thus the power-handling capacity of the phase shifter can be greatly improved. The phase shifter is designed to provide a phase-shift range from 0° to 360° at a step of 5.625° and operate in the frequency band from 9.2 to 9.8 GHz. Simulation results and measurement results of the prototype agree closely and show that the phase shifter has a much higher power-handling capacity than that of the PIN diode and low insertion losses across the operating frequency band. © 2010 EuMA.published_or_final_versionThe 40th European Microwave Conference (EuMC 2010), Pairs, France, 28-30 September 2010. In Proceedings of EuMC 2010, 2010, p. 437-44

An RF predistorter for base station HPAs of NADC system

This paper presents the design of an effective and low cost RF predistorter for use in the base-station high power amplifiers (HPAs) of the North American Digital Cellular (NADC) system. A complex polynomial is used to model the characteristic of the HPA and the predistorter generates the inband intermodulation (IM) products required for predistortion of the HPA. The design of the predistorter has a simple structure, using Schottky diodes as the nonlinear device to generate the inband IM products. Experimental results using a practical HPA show that the predistorter can reduce the adjacent-channel-power ratio (ACPR) of the pi/4-DQPSK signal used in the NADC system by 20 dB at an HPA output power level of 30 W. Moreover, the constellation and eye diagrams of the pi/4-DQPSK signal show that the predistorter can also reduce the signal distortion caused by the HPA. ©2009 IEEE.published_or_final_versio

Circular-polarization reconfigurable monopole antenna with enhanced boresight gain for GNSS applications

A circular-polarization (CP) reconfigurable monopole antenna with enhanced boresight-gain for GNSS applications is proposed. The antenna consists of two meandered monopoles placed perpendicular to each other, a feeding network using the Wilkinson power divider, two switchable 90°-phase-shifters, a defected ground structure (DGS) and a metallic reflector. The metallic reflector is placed at the back of the antenna to improve efficiency and boresight gain. Simulation results show that the metallic reflector can substantially increase the efficiency and boresight-gain of the antenna by about 20% and 5 dB, respectively, in the operating band, yet retaining the impedance bandwidth and axial-ratio bandwidth.postprin

Simplified ordering for fixed-complexity sphere decoder

This paper proposes a simplified ordering algorithm for the fixed-complexity sphere decoder (FSD). The new algorithm is developed from the analysis of the ordering for FSD from a geometrical point of view. Computer simulation is used to assess the improvements in bit-error rate (BER) performances of MIMO systems using the FSD with the original and the simplified ordering. Simulation results show that the new ordering method can achieve nearly the same BER as the original ordering method but with much less complexity. Copyright © 2010 ACM.postprintThe 6th International Wireless Communications and Mobile Computing Conference (IWCMC 2010), Caen, France, 28 June-2 July 2010. In Proceedings of the 6th International Wireless Communications and Mobile Computing Conference, 2010, p. 804-80

A new family of linear dispersion code for fast sphere decoding

In this paper, a new family of Linear Dispersion Codes (LDCs) that can be decoded using a fast Sphere Decoding (SD) algorithm in MIMO systems is proposed. The basic principle of this structure is to make the LDC to have as many as possible the rows orthogonal in the dispersion matrices. Monte Carlo simulation results show that the optimum LDCs with this orthogonal structure have nearly identical bit-error-rate (BER) performances as other optimal LDCs. We develop a simplified Sphere Decoding (SD) algorithm that can significantly reduce the decoding complexity in decoding the new LDCs with proposed orthogonal structure. Simulation results show that the complexity reduction is more significant for MIMO system transmitting higher level modulation. For 2×4 MIMO systems transmitting 4 64QAM and 256QAM symbols in a block length of 4, the reductions are about 71-83% and 76-88%, respectively. ©2009 IEEE.published_or_final_versionThe 22nd IEEE Canadian Conference on Electrical and Computer Engineering (CCECE 2009), St. John's, NL., 3-6 May 2009. In Proceedings of the 22nd CCECE, 2009, p. 314-31

A 5 th-order analog predistorter for NADC system

This paper presents the design of a 5th-order analog predistorter using the inband intermodulation (IM) signals for predistortion of base-station high power amplifiers (HPAs) for the North American Digital Cellular (NADC) system. The predistorter employs two mixers with same configuration to generate 3rd-order intermodulation (IM3) products and 5th-order intermodulation (IM5) products, to suppress the 3 rd-and 5th-order intermodulation distortion products (IMDP3 and IMDP5) at the HPA output. The predistorter is implemented and tested using the pi/4-DQPSK signal of the NADC system at 2.2GHz in a practical 100W-HPA. The results show that, at the HPA output powers of 65.6, 56.2, 50 and 41.3 W, the predistorter can suppress the adjacent channel power ratio (ACPR) of the pi/4-DQPSK signal at ± 20 kHz from the center frequency by 15.16, 15.83, 16.17 and 15.17 dB, respectively. © 2010 IEEE.published_or_final_versionThe 12th IEEE International Conference on Communication Systems (ICCS 2010), Singapore, 17-19 November 2010. In Proceedings of 12th ICCS, 2010, p. 19-2

An intermodulation products generator for predistortion of base station HPAs

This paper presents the design of an intermodulation (IM) products generator for predistortion of high-power amplifiers (HPAs) used in the base stations of cellular mobile systems. The IM products generator composes of two simple mixers constructed with Schottky diodes, has a simple structure and requires no external dc bias voltage. Simulation and measurement results show that the generator has a low conversion loss and low spurious frequency components. Studies of the IM3 generator for predistortion of a practical base station HPA are also carried out by simulation and measurements. Measurement result of a two-tone test shows that the predistorter can suppress the 3rd intermodulation distortion (IMD) products by 15 dB. ©2009 IEEE.published_or_final_versionThe IEEE Radio and Wireless Symposium (RWS 2009), San Diego, CA., 18-22 January 2009. In Proceedings of RWS, 2009, p. 602-60