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In this paper, we analyze performance of reflected signal mitigation method for ultrasonic communication system through a steel wall channel. Pre-distortion scheme using echo cancellation pulse can be one of the solutions against the echo problem without a burden of receiver complexity. However, there are some possible exceptions which make performance of echo reduction effect worse. In this paper, therefore, we're concerned about ununiformed path lengths of each reflection and amplitude measurement error of 1st echo. Narrow pulse test is performed for characterization of the channel and evaluation of echo cancellation method in MATLAB simulation. Simulation results show that the effect of echo cancellation can be degraded if channel model approximation is not correct. But, although this problem can be happened, the system performance of mitigation of echoes is outstandingly successful since reflections after echo cancellation are tiny compared with LOS received signal. [ABSTRACT FROM PUBLISHER]

Wideband signals without pre-distortion are distorted by memory and nonlinear effect of high power amplifier. To compensate these distortions, we propose an adaptive pre-distorter based on orthogonal polynomials. Based on orthogonal criterion, we derive a series of orthogonal polynomials under circular symmetric complex Gaussian distribution. Indirect learning architecture is used for pre-distorter identification and recursive least square algorithm is introduced for parameters estimation. At last using two power amplifier models, we simulate the performance of the proposed pre-distorter in an OFDM system. Simulation results show that the proposed pre-distorter can effectively compensate the distortions produced by high power amplifier. [ABSTRACT FROM PUBLISHER]

In this paper, we propose closed loop satellite communication system to compensate for nonlinear problem of HPA in satellite. Conventional pre-distorter schemes can only compensate for one HPA nonlinear problem. But, the proposed schemes can compensate for nonlinear problem including two HPA model. The purpose of this paper is to increase efficiency of HPA and to secure high communication quality by closed loop pre-distortion technique with feedback information at the receiver. Simulation result shows that the proposed scheme can compensate for nonlinear problem including two different HPA models. [ABSTRACT FROM PUBLISHER]

Signal generator is an important part for a Radar system. In this paper, the Pre-distortion for baseband signals and intermediate frequency (IF) signal is introduced. The signal generator with the effective pre-distorition methods in time and frequency domain based on DDWS is realized. Experimental results of the signal generator are presented, which prove the pre-distortion are reasonable and effective. Temperature and vibration tests are also involved to validate the stability and reliability. [ABSTRACT FROM PUBLISHER]

A 1710–1755MHz hybrid power amplifier module (PAM) consisting of a CMOS driver and a GaAs HBT output stage is described. By using multiple parallel CMOS driver stages the gain and bias current expansion needed to maintain the linearity into class C operation of the bipolar output stage is generated. This extends the linear output power range by 0.5 dBm and increases the power added efficiency (PAE) at ACLR1 of −40dBc from 39.0% at 28 dBm output power to 41.3% at 28.5 dBm output power for a WCDMA modulated signal. The PA achieves 43.5% PAE at 29 dBm Pout for an ACLR1 of −37 dBc with a gain of 26 dB and supply voltage of 3.4V. [ABSTRACT FROM PUBLISHER]

Millimeter-wave power amplifiers realized in CMOS processes have demonstrated output power and power added efficiency exceeding 20 dBm and 30%, respectively. We describe efforts to achieve high power and high efficiency for mm-wave transmitters and linearize mm-wave PAs in fineline CMOS processes. We will present novel circuit approaches based on Doherty amplifiers and digital pre-distortion of high-power mm-wave CMOS PA to demonstrate low error-vector magnitude (EVM). [ABSTRACT FROM PUBLISHER]

A modified piece-wise polynomial pre-distortion is proposed, investigated and compared against classic memoryless polynomial pre-distortion. The proposed enhanced piece-wise polynomial pre-distortion uses the overlap between segments to ensure continuity in the total pre-distortion function. The implementation of overlap allows the use of a simple error estimation algorithm to minimise hand over error. The classic and proposed piece-wise pre-distortion performances are assessed and compared for several sets of polynomial coefficients. The proposed method is shown to consistently outperform classical polynomial pre-distortion in terms of required coefficients and linearity improvement. The method is applied for the linearisation of an envelope tracking Class-J PA at 1.7GHz, under a 1.4MHz LTE signal with a 14.4dB PAPR. [ABSTRACT FROM PUBLISHER]