Bandwidth Limitation for the Constant Envelope Components of an OFDM Signal in a LINC Architecture

Mustafa, Abdul K.; Ahmed, Shabbir; Faulkner, M.

doi:10.1109/tcsi.2013.2246255

Cited by 10 publications

(8 citation statements)

References 17 publications

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“…1, the phase signals Φ 1,2 (t) are derived from baseband complex components I and Q by the signal component separator (SCS). Because of nonlinear signal processing in the signal component separator, the bandwidth of the modulating signal Φ(t) far exceeds the bandwidth of the original baseband IQ signal [41]. The bandwidth expansion sets further requirements for the sampling rate of a digital system.…”

Section: Outphasing Transmitter Operation a Outphasing Principlementioning

confidence: 99%

Digital Interpolating Phase Modulator for Wideband Outphasing Transmitters

Lemberg

Kosunen

Roverato

et al. 2016

IEEE Trans. Circuits Syst. I

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Radio transmitters are evolving towards digitalintensive solutions to exploit reconfigurability and benefit from CMOS process scaling. Outphasing has been identified as a suitable candidate for digital wideband transmitters. However, with recent digital-intensive outphasing transmitters the achieved performance in terms of adjacent channel leakage ratio (ACLR) has been limited. This paper identifies the sampling images of the modulating phase signal as the main factor limiting the ACLR of digital outphasing transmitters. We present a new digital interpolating phase modulator architecture, capable of providing significantly better sampling image attenuation. When evaluated in outphasing configuration with a 100 MHz OFDM signal at the carrier frequency of 2.46 GHz, and 10-bit phase resolution, the proposed solution achieves an ACLR of-59 dBc, compared to-43 dBc achievable with the phase modulator architecture utilized in state-of-the-art digital outphasing transmitters. The proposed digital interpolating phase modulator is also capable of custom carrier generation, a straightforward method for generating an arbitrary carrier frequency up to 1.25 times the phase modulator sampling rate.

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Section: Outphasing Transmitter Operation a Outphasing Principlementioning

confidence: 99%

Digital Interpolating Phase Modulator for Wideband Outphasing Transmitters

Lemberg

Kosunen

Roverato

et al. 2016

IEEE Trans. Circuits Syst. I

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“…A further consideration relating to combiner operating bandwidth is the effect on the load impedances seen by the four branch amplifiers at different operating frequencies [46]. Fig.…”

Section: Combiner Bandwidthsmentioning

confidence: 99%

Four-Way Microstrip-Based Power Combining for Microwave Outphasing Power Amplifiers

Barton

Perreault

2014

IEEE Trans. Circuits Syst. I

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Abstract-A lossless multi-way outphasing and power combining system for microwave power amplification is presented. The architecture addresses one of the primary drawbacks of Chireix outphasing; namely, the sub-optimal loading conditions for the branch power amplifiers. In the proposed system, four saturated power amplifiers interact through a lossless power combining network to produce nearly resistive load modulation over a 10:1 range of output powers. This work focuses on two microstrip-based power combiner implementations: a hybrid microstrip/discrete implementation using a combination of microstrip transmission line sections with discrete shunt elements, and an all-microstrip implementation incorporating open-circuited radial stubs. We demonstrate and compare these techniques in a 2.14 GHz power amplifier system. With the allmicrostrip implementation, the system demonstrates a peak CW drain efficiency of 70% and drain efficiency of over 60% over a 6.5-dB outphasing output power range with a peak power of over 100 W. We demonstrate W-CDMA modulation with 55.6% average modulated efficiency at 14.1 W average output power for a 9.15-dB peak to average power ratio (PAPR) signal. The performance of this all-microstrip system is compared to that of the proposed hybrid microstrip/discrete version and a previously reported implementation in discrete lumped-element form.Index Terms-base stations, outphasing, power amplifier (PA), wideband code division multiple access (W-CDMA), Chireix, LINC, load modulation.

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“…It is known that the bandwidth of the LINC component signals is much wider than its original signal. There are a number of methods to reduce the bandwidth, e.g., [38,39]. However, these methods may distort the combined signal.…”

Section: Discussionmentioning

confidence: 99%

Maximum likelihood detection for coded combinerless LINC-OFDM systems

Cheng

Hsu

2016

J Wireless Com Network

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Owning to the high peak-to-average power ratio problem, the power efficiency of orthogonal-frequency-divisionmultiplexing (OFDM) systems is usually low. It deteriorates in millimeter wave systems in which the design of an efficient linear power amplifier is much more challenging. The linear-amplification-with-nonlinear-component (LINC) technique can serve as a remedy, decomposing the input signal into two constant-envelop component signals followed by high-efficient nonlinear amplifiers. However, the power combiner, a key component used to combine the amplified signals, is difficult to implement. Combinerless LINC systems employ two transmit antennas such that two component signals can be naturally combined at the receiver. Unfortunately, the performance of combinerless LINC-OFDM systems is seriously degraded if difference, even small, exists between the two channels. The maximum likelihood (ML) receiver can effectively solve the problem; however, its computational complexity is prohibitedly high. We propose a coded combinerless LINC-OFDM system, including a convolutional encoder and a list Viterbi algorithm (LVA) decoder, to solve the problem. The LVA can provide a small number of candidates for the ML detector, dramatically reducing the required computational complexity. We also utilize an enhanced zero-forcing equalizer such that the soft-demapping operation can be effectively conducted. Finally, we propose a simple iterative interference cancellation scheme to further enhance the performance. Simulations show that the proposed combinerless LINC-OFDM system can outperform the conventional OFDM while the consumed power is much lower.

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Bandwidth Limitation for the Constant Envelope Components of an OFDM Signal in a LINC Architecture

Cited by 10 publications

References 17 publications

Digital Interpolating Phase Modulator for Wideband Outphasing Transmitters

Digital Interpolating Phase Modulator for Wideband Outphasing Transmitters

Four-Way Microstrip-Based Power Combining for Microwave Outphasing Power Amplifiers

Maximum likelihood detection for coded combinerless LINC-OFDM systems

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