Code Division Multiple Access Applications Research Articles

A Highly Extended High-Efficiency Range Class-F–C Doherty Power Amplifier

This paper presents a new extended high-efficiency-range Doherty power amplifier (DPA) with a main and only a single auxiliary amplifier. In order to extend the output high-efficiency range with a high-efficiency level, asymmetrical cells are employed as the main and auxiliary amplifiers in class-F and class-C complex combining load (CCL) methodology, respectively. To verify the proposed methodology, a DPA with 12-dB output back-off (OBO) is designed and fabricated for wideband code division multiple access (WCDMA) applications. Large-signal continuous-wave measurement results show the power gain of about 11[Formula: see text]dB with a drain efficiency of 59.9% at 12[Formula: see text]dB of OBO. A two-tone test exhibits a third-order intermodulation distortion (IMD) of lower than [Formula: see text][Formula: see text]dBc. Modulated wave measurements show over 55% of average drain efficiency and an adjacent channel leakage power ratio (ACLR) of lower than [Formula: see text][Formula: see text]dBc at an output power level of 31.5[Formula: see text]dBm.

Compact wideband transparent antenna for 5G communication systems

AbstractA compact wideband transparent antenna designed on plexiglass substrate (10 × 12 × 1.48 mm3) is presented. The optically transparent antenna consists of a radiation patch and a ground plane fabricated using AgHT‐8. The antenna design comprises of rectangular shaped branches optimized to attain the wideband characteristics. The proposed antenna design has impedance bandwidth of 58.71% covering the frequency range of 23.92‐43.8 GHz. The radiation pattern of the proposed antenna shows directional radiation pattern with electrical tilt. All calculated and measured results show that proposed compact transparent antenna is an excellent candidate for 5G communication systems and wideband code division multiple access applications.

LARGE-SCALE MIMO MC-CDMA SYSTEM USING COMBINED MULTIPLE BEAMFORMING AND SPATIAL MULTIPLEXING

This paper proposes a novel Large-scale (massive) Multi-input Multi-output Multi-carrier Code division multiple access (LS MIMO MC-CDMA) model and application to Fifth-Generation Mobile Communication Systems (5G). This system uses combined cylindrical array antenna multiple beamforming architecture with spatial multiplexing. The model is optimized by Min-Max criteria in order to minimize side lobes and maximize compression of propagation loss. The Monte Carlo simulation results unify with the analytical solution for system performance.

Mode-Locked Laser Diodes and Their Monolithic Integration

We describe mode locked laser diodes (MLLDs) operating from 40 GHz to >1 THz. Below 40 GHz, operation at the fundamental cavity frequency is appropriate, but at higher frequencies harmonic mode-locking (HML) is used. To increase output power and control nonlinear behavior, the gain needs to be modified, and an AlGaInAs/InP structure with a three-quantum-well active layer and passive far-field reduction layer is presented. In 40-GHz all-active MLLDs, this structure offers improvements in internal loss, slope efficiency, mode locking (ML) range, RF linewidth, timing jitter, far field pattern, and coupling efficiency to a single-mode fiber. By creating a transparent passive waveguide in part of the cavity, a 490-fs pulse width was achieved, the shortest reported from any quantum well MLLD. Several approaches are described for HML: colliding pulse ML operating up to 240 GHz, coupled cavity ML up to 160 GHz, and sampled Bragg grating constructions up to 1.28 THz. This latter approach offers stable HML over a wide range of bias conditions. Finally, we report a synchronized multicolor ML laser array, containing four 40-GHz lasers with designated wavelength registration for optical code division multiple access or optical time division multiple access applications.

Transmitter leakage cancellation technique for CMOS SAW-less radio front-ends

A novel method of transmitter (TX) leakage cancellation is presented to improve the dynamic range of the receiver for wideband code division multiple access applications. The large TX leakage is attenuated within the low noise amplifier (LNA) output using a feed-forward path without any LNA noise figure degradation. A prototype has been designed and laid out in 0.18 μm CMOS technology. It achieves a maximum TX rejection of 18.5 dB with only 5.2 mA current consumption from 1.8 V supply voltage. LNA P-1dBCP (1 dB gain compression point) against TX leakage improves by more than 10 dB. Post layout simulations verify these results. Proposed structure dispels the requirement of off-chip surface acoustic wave filter.

Design of Highly Birefringent Bending Insensitive Single Mode Photonic Crystal Fiber

Objectives: Bending insensitive Photonic Crystal Fiber will possess low loss and the research aims for high birefringence and large nonlinearity. Bending insensitive Photonic Crystal Fiber (PCF) along with high birefringence and high nonlinearity is being presented in this paper. Methodology: The fiber is bent by applying some bending radius along with the angle in the direction of the bending and the effects due to these angles are being extensively studied by using Finite Element Method (FEM). Findings: The birefringence in the range of 10−2 can be achieved and nonlinear coefficient in the range of 70-110 W−1Km−1 can be obtained. The PCF possesses very low effective mode field area (MFA) which would be leading to positive effect on the bending losses. The number of air hole rings used in the designed structure is very less so the designed fiber is easy to fabricate. Applications: This fiber can be used in the medical applications for detecting the tumors, for Optical Code Division Multiple Access (OCDMA) applications, high power laser applications.

Dual-Band Base Station Array Using Filtering Antenna Elements for Mutual Coupling Suppression

This paper presents a novel dual-band base station antenna array using filtering antenna elements for size miniaturization. It consists of two $1 \times 6$ subarrays arranged side by side, which are designed for Digital Cellular System (DCS: 1710–1880 MHz) and Wideband Code Division Multiple Access (WCDMA: 1920–2170 MHz) applications. The two subarrays are composed of filtering antenna elements with high in-band radiation efficiency and out-of-band radiation rejection levels. The radiation of the DCS subarray is suppressed in the WCDMA band and vice versa. Mutual coupling between the two subarrays, therefore, can be suppressed and high isolation can be obtained with reduced subarray spacing. For demonstration, a dual-band filtering antenna array is designed and fabricated. The overall width of the array is only 206 mm, which is much narrower than that of typical industrial products ( $\sim 290$ mm). An isolation of 35 dB is obtained between the two subarrays without any decoupling network. The measured antenna gains are about 14.2 and 14.5 dBi for DCS and WCDMA bands, respectively, and the 3-dB beamwidths of the horizontal radiation patterns are 65° ± 5°. In addition, null filling below the main beam in the vertical radiation patterns is realized by elaborately designing a feed network to manipulate the output magnitude and phase of each array element. The proposed array is suitable for potential base station applications.

Analysis, Design, and Test of CDMA LFSR with Offset Mask Using Standard ICs

Hardware implementation of Linear Feedback Shift Register (LFSR) plays a great and very important role in communication systems, and in many security devices. In this paper, a design of LFSR with offset mask has been presented, for Direct Sequence Code Division Multiple Access (DS-CDMA) applications. Integrated electronic components have been used. An accessible model facilitating the synthesis on Printed Circuit Boards (PCB) and implementation on Field Programmable Gate Array (FPGA) is offered. In addition, a temporal and spectral analysis of the circuit is performed in order to validate the design. This latter facilitates the generation of pseudo-random codes based on LFSR and their integration into electronic systems.

Fully Monolithic BiCMOS Reconfigurable Power Amplifier for Multi-Mode and Multi-Band Applications

A power amplifier (PA) supporting wideband code division multiple access, long-term evolution (LTE), and wireless local area network applications has been implemented in 0.18- $\mu{\hbox{m}}$ SiGe BiCMOS technology. The PA integrates a tunable input matching network, a broadband output matching network, and adaptive bias circuits in a single chip to achieve high linearity and high power in different modulation schemes and operating bands. The three-stage PA adopts a differential-type configuration without using through-silicon-via technology to deliver 4 1.3–42 dB of gain and 28.2–28.6 dBm of 1-dB compression output power with a 20.8–27.6% power-added efficiency (PAE) at 1.85–2.5 GHz. To further validate the usefulness of the proposed PA, the envelope-tracking PA is designed to improve the PAE by 6.5% within the linearity specification of a 24.7-dBm average output power and a $-$ 33-dBc adjacent channel leakage ratio for 2.35-GHz 16 quadrature-amplitude-modulation time-division LTE signal with 20-MHz bandwidth.

Envelope tracking CMOS power amplifier with high-speed CMOS envelope amplifier for mobile handsets

A high-efficiency CMOS power amplifier (PA) based on envelope tracking (ET) has been reported for a wideband code division multiple access (W-CDMA) and long term evolution (LTE) application. By adopting a high-speed CMOS envelope amplifier with current direction sensing, a 5% improvement in total power-added efficiency (PAE) and a 11 dB decrease in adjacent channel leakage ratio (ACLR) are achieved with a W-CDMA signal. Moreover, the proposed PA achieves a PAE of 25.4% for a 10 MHz LTE signal at an output power (Pout) of 25.6 dBm and a gain of 24 dB.

A Quadratic-Interpolated LUT-Based Digital Predistortion Technique for Cellular Power Amplifiers

Baseband digital predistortion (DPD) is an efficient and low-cost method for linearizing a power amplifier (PA) in a wireless system using a modulation scheme with nonconstant envelope. The polynomial and the lookup table (LUT) predistortion schemes are two commonly used approaches. Both approaches require time to find the inverse characteristics of the PA to be predistorted. However, for DPD to be actually implemented in real-world scenarios, fast convergence is highly desirable. A low-complexity joint-polynomial/LUT predistortion PA linearizer is proposed to obtain fast linearization. The algorithm utilizes quadratic interpolation of the LUT, which reduces the required LUT size and hence reduces convergence time without degradation of linearity. Simulation result shows that the proposed method can achieve up to 500% improvement in convergence speed compared with the conventional linear interpolation approach for the wideband code-division multiple access application.

DESIGN OF A DUAL-BAND DOHERTY POWER AMPLIFIER UTILIZING SIMPLIFIED PHASE OFFSET-LINES

This paper proposes a novel design methodology for dual-band Doherty power amplifler (DPA) with simplifled ofiset-lines. The methodology is validated with the design and fabrication of a 10W GaN based DPA for Global System for Mobile Communications (GSM) and Wideband Code Division Multiple Access (WCDMA) applications at 0.90GHz and 2.14GHz, respectively. In the measurement results, the DPA achieves a drain e-ciency (DE) of 51.2% with an output power of 37.2dBm at the 6.5dB output power back-ofi (OBO) from the saturated output power at 0.90GHz, and a DE of 39.9% with an output power of 37.4dBm at the 6.5dB OBO at 2.14GHz. Linearity results using 20MHz 16QAM signal show an adjacent channel leakage ratio (ACLR) of i48dBc and i43dBc with the average output power of 37.2dBm and 37dBm at 0.90GHz and 2.14GHz, respectively.

A CMOS Transmitter Leakage Canceller for WCDMA Applications

A transmitter (TX) leakage canceller is proposed for improving the dynamic range of the receiver (RX) for wideband code division multiple access applications. A TX leakage canceller circuit in this paper is simple in implementation and has low noise figure (NF) contribution. It is a feed-forward canceller that samples a reference signal from the TX output and injects the amplitude-adjusted and phase-rotated signal to the RX chain. The canceller circuit is integrated with a low-noise amplifier and implemented in a 0.18-μm CMOS technology. A cancellation of 23 dB is achieved with only 10-mA current consumption increase and low NF increase.

Low power saw‐less WCDMA transmitter with quadrature driver amplifier and injection‐locked frequency divider

AbstractA direct conversion transmitter with low noise and low power is presented in this article.A quadrature driver amplifier is used to remove the Inphase‐Quadrature crosstalk in a passive mixer operating with 50% duty cycle local oscillator (LO). In the quadrature LO generation, an inductor‐less injection‐locked frequency divider is utilized to reduce the phase noise contribution with cost of a small current and area. Fabricated in 65 nm CMOS process, a transmitter prototype is designed for wideband code division multiple access (WCDMA) application. Measurement results show that the proposed transmitter achieves 1 dBm maximum output power at 2.53 GHz, 1.7% error vector magnitude (EVM), and −158.5 dBc/Hz output noise at the receiver (RX) band, eliminating the need for the surface acoustic wave (SAW) filter in a traditional transmitter design, with an area of 0.18 mm2 and a total power consumption of 37.8 mW. © 2013 Wiley Periodicals, Inc. Microwave Opt Technol Lett 55:1217–1221, 2013; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.27571

Rectangular Global Envelope Super Structured FBGs for Multiband Coherent OCDMA

We present rectangular global envelope coherent direct sequence en/decoders for wavelength division multiplexing (WDM)-optical code division multiple access applications. The device presents balanced insertion loss and sharp edges for optimum DWDM channeling. Experimental results using 5 and 1 100-GHz sub-bands en/decoders demonstrate the applicability of these devices both for broadcasting and point-to-point applications.

On the Construction of Binary Sequence Families With Low Correlation and Large Sizes

In this paper, we revisit a method to produce binary sequences using the most significant bit map from Z4 to the binary field. This method is useful for the construction of binary sequences with low correlation and large family size. There may be more cases where starting with Z4 could help researchers design new low correlation sequences for code-division multiple access application.

Dielectric-Loaded Compact WLAN/WCDMA Antenna With Shorted Loop and Monopole Elements

A compact, planar, dielectric-loaded, and multiple-band antenna for 2.45/5-GHz WLAN and 2.1-GHz wideband code-division multiple access (WCDMA) applications is presented in this letter. The antenna has a planar loop element with a shorting pin and a planar monopole element that are printed on the same substrate and driven by a microstrip line. The loop and monopole elements are covered by a thin FR4 layer on top to achieve good impedance matching at both bands. Analysis of the antenna has been realized using extensive 3-D full-wave electromagnetic simulations. Antenna measurements have also been presented, and it is shown that measurements and simulations are in good agreement.

70-MHz IF 10-MHz bandwidth bandpass $$\Upsigma\Updelta$$ modulator for WCDMA applications

A MASH bandpass $$\Upsigma\Updelta$$ modulator for wide-band code division multiple access (WCDMA) applications is presented. The signal bandwidth of the proposed modulator is 10 MHz centered aroun...

Generation of pseudorandom binary sequences by means of linear feedback shift registers (LFSRs) with dynamic feedback

In 2002, Mita et al. [1] proposed a pseudorandom bit generator based on a dynamic linear feedback shift register (DLFSR) for cryptographic application. The particular topology there proposed is now analyzed, allowing us to extend the results to more general cases. Maximum period and linear span values are obtained for the generated sequences, while several estimations for autocorrelation and cross-correlation of such sequences are also presented. Furthermore, the sequences produced by DLFSRs can be considered as interleaved sequences. This fact allows us to apply the general interleaved sequence model proposed by Gong and consequently simplify their study. Finally, several remarks are stated regarding DLFSR utilization for cryptographic or code division multiple access (CDMA) applications.

An analytic approach for CDMA output of feedforward power amplifier

In this paper, a novel method is introduced to predict the Code-Division Multiple-Access (CDMA) output spectrum of an RF power amplifier linearized with feedforward technique based on transfer function. In this method, an RF power amplifier is modeled mathematically by nonlinear complex envelope transfer function based on AM-AM and AM-PM distortion diagrams. Using this model, analytic expressions of CDMA output spectrum of power amplifier is calculated. Having mathematical model of RF power amplifier leads to derive analytic expressions for InterModulation (IM) products in feedforward amplifier. Based on these expressions, IM products are related to nonlinear complex envelope transfer function of feedforward amplifier. Then, CDMA output spectrum of feedforward linearization technique is predicted. The loops imbalances in feedforward technique are considered in analysis. Finally, the results of derived expressions in MATLAB software are compared with ADS simulations results and good agreements were achieved. Employing this method gives insight for feedforward analysis and loops imbalances effects in feedforward amplifier for CDMA applications.