Guide to quality control and company standardization

Non-constant envelope modulation schemes have become commonplace in cellular applications due to their higher spectral efficiency. Linear PAs driven by an RF transmitter are usually used to generate these signals faithfully at the expense of power efficiency. Separate processing of amplitude and phase information (e.g., EER or polar modulation) has been proposed [1] as a way of improving the system power efficiency. However, many of these schemes require an efficient high-power low-frequency supply modulator to reconstruct the amplitude information. This can be done, for instance, using a switching DC-to-DC converter with its own limitations in efficiency, bandwidth, and area that also requires an external inductor [2]. Even for an ideal supply modulator, the amplitude dynamic range of the PA itself is limited by the gate-to-drain feedthrough and its associated AM-to-AM and AM-to-PM conversion. (For example, in [3] a 10dB change in the supply results in a 5° phase shift at the output.) Although a digitally-modulated polar PA [4] has been shown as a possible solution at lower power levels, its implementation in a wideband watt-level fully-integrated CMOS PA for non-constant modulation has not yet been demonstrated.

An octave-range watt-level fully integrated CMOS switching power mixer array for linearization and back-off efficiency improvement

This paper presents a development of a wideband delta- sigma modulator for fully digital GHz transmitters. The fully digital RF transmitter is developed as a promising solution for software deflned radio (SDR) terminals and applications. The fully digital transmitter consists of a delta-sigma modulator, a high- speed multiplexer and a switching-mode power amplifler. The speed limitation of delta-sigma modulator is the main limitation to increase the signal bandwidth in fully digital transmitters. In this paper, the bandwidth of the fully digital transmitter is increased 8 times using parallel processing time-interleaved architecture, while maintaining the same signal quality. This architecture was implemented on FPGA and tested for difierent standards (WiMAX and LTE) with a signal bandwidth up to 8MHz. The concept was assessed in terms of SNDR by using a difierential logic analyzer at the output of FPGA, and the SNDR was found to be around 60dB.

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TIME-INTERLEAVED DELTA-SIGMA MODULATOR FOR WIDEBAND DIGITAL GHz TRANSMITTERS DESIGN AND SDR APPLICATIONS

OFDM is an important modulation technique currently in development in the field of communications systems. OFDM signals can combat multipath propagation and fading channels and can support large data rates. However, OFDM systems are multicarrier systems and experience problems due to the required summation of sinusoids when the in-phase subcarriers are combined, which produces high power peaks. The large power envelope fluctuations that occur at the output cause in-band and out-of-band distortions that result in degraded BER performance. The literature contains many qualified approaches to resolving the peak-to-average power ratio problem, including selected mapping, partial transmit sequence, and amplitude clipping techniques. The simplest technique is the amplitude clipping technique, and the selected mapping and partial transmit sequence techniques are excessively complicated for real-time implementation. In this paper, we suggest a modification to the amplitude clipping method to produce a novel clipping technique called the side information supported amplitude clipping SI-SAC method. The SI-SAC technique involves sending certain bits of extra information so that the receiver can recover all of the clipped data. The SI-SAC technique does not add computational complexity to the system, and simulation results show that the proposed method is superior to the conventional method. The peak-to-average power ratio was reduced by i¾?2.5dB, and the magnitude of the mean squared error vector is the same as that of the original signal that is not clipped. In contrast, the conventional amplitude clipping method produces a mean squared error vector with a large magnitude. Copyright © 2012 John Wiley & Sons, Ltd.

Reducing the power envelope fluctuation of OFDM systems using side information supported amplitude clipping approach

Laser direct metal deposition was used to manufacture AlSi10Mg alloy in this study. The microstructure and mechanical properties of the additive manufacturing AlSi10Mg alloy, and the influence of s...

Microstructure and mechanical properties of additive manufacturing AlSi10Mg alloy using direct metal deposition

A silver shell‑copper core coating was applied on additively manufactured (AM) AlSi10Mg alloy to improve the electrical conductivity, corrosion resistance, surface roughness and indentation hardness. Surface microstructure evolution and roughness of the AM alloy, i.e. as-built, during the subsequent processes, such as heat treatment, shot peening and Ag Cu coating, were comprehensively characterized using secondary electron imaging in a scanning electron microscope and a scanning laser microscope, respectively. Also, the surface indentation hardness of the coated alloy was evaluated to study the mechanical response. The corrosion behavior and electrical conductivity of the Ag Cu coated AM alloy were evaluated and compared with the as-built and shot peened AM alloy using the electrochemical and the electrical resistivity measurements, respectively. The results showed that the Ag Cu coating could significantly increase the surface hardness of the AM AlSi10Mg four times along with an average of 60% improvement in roughness. The electrochemical characterization shows a significant increase in the corrosion resistance for the Ag Cu coated AM AlSi10Mg with a low corrosion current density of 4 μmA/cm2 in a chloride solution compared to the uncoated alloy. Finally, it was observed that the Ag Cu coating leads to reduction of the electrical resistance of the studied AM alloy by 40%. Consequently, the electrical conductivity property of the coated AM AlSi10Mg increases.

Enhancement of electrical conductivity and corrosion resistance by silver shell‑copper core coating of additively manufactured AlSi10Mg alloy

This paper presents the design method, properties and driving techniques of a linear 0.5 W 1 GHz LDMOS power amplifier used in a supply modulated envelope tracking transmitter with real-time predistortion. Causes of nonlinearities are identified, and various supply voltage drives are experimented. Measured results show that the power efficiency can be improved while maintaining high linearity. Copyright © 2008 John Wiley & Sons, Ltd.

Envelope tracking power amplifier with static predistortion linearization

Laser welding of AlSi10Mg aluminium-based alloy produced by Selective Laser Melting (SLM)

An efficiency enhanced power amplifier is presented. The amplifier uses envelope tracking (ET) technique and static predistortion to achieve high linearity. The effects of drain voltage modulation to experimental amplifier's gain, phase as well as bandwidth are measured using simple single-tone tests and discussed. Then the amplifier's ET performance is evaluated. The complete envelope tracking system uses 16 QAM modulated 1 MHz bandwidth signals. The amplifier's single-tone power added efficiency (PAE) was measured to be 38% with 20 dBm output power and average PAE for 16 QAM was 39% with average output power of 20 dBm. The amplifier achieved roughly 25 dBc ACPR, which improved to roughly 50 dBc after adding predistortion.

This paper describes advantages and peculiarities of class E power amplifier when used in a polar transmitter system. Basic principles about class E and information about different nonlinearities are given. Also, modifying transistor model to switch use is discussed briefly. A 1 GHz, 0.5 W class E power amplifier was implemented for a polar transmitter. Differences between transmitter systems are mentioned and measurements of a total transmitter system performance are presented.

Timo Rautio

Papers

Enhancement of electrical conductivity and corrosion resistance by silver shell‑copper core coating of additively manufactured AlSi10Mg alloy

Envelope tracking power amplifier with static predistortion linearization

Laser welding of AlSi10Mg aluminium-based alloy produced by Selective Laser Melting (SLM)

Envelope tracking power amplifier with static predistortion linearization

1 GHz Class E RF Power Amplifier For A Polar Transmitter