Analog photonic links require linear drive of electrooptic modulators at high frequency to support emerging millimeter wave (mm-wave) communication standards. However, this is challenging due to the ...nonlinear distortion of commonly used Mach-Zehnder modulators (MZMs). This article presents the first CMOS MZM driver capable of operating over a wide 20-35-GHz frequency range with a programmable linearizer. A broadband design is achieved with a magnetically coupled resonator (MCR) technique that provides wideband impedance matching for the interstage and output-stage matching networks. Linearization is achieved with a topology consisting of inverter-based amplifier segments that provide programmable predistortion gains over the input signal regions. Fabricated in 28-nm CMOS, the driver delivers 2.5-Vpp swing to an external MZM. Operating the majority of the circuitry at 0.9 V, except for the 1.6-V output stage, allows for a power consumption of only 180 mW. The proposed programmable linearizer is able to compensate the amplitude-to-amplitude modulation (AM-AM) compression of the amplifier stages and the external MZM, extending output power 1-dB compression point (<inline-formula> <tex-math notation="LaTeX">\text {OP}_{1~\text {dB}} </tex-math></inline-formula>) of the whole radio-over-fiber (RoF) link by 3 dB and achieving 4.8-dBm third-order input intercept point (IIP3) at 25 GHz.
This paper presents a new predistortion linearization technique for high linearity and high modulation efficiency in millimeter-wave (mm-wave) CMOS power amplifiers (PA) for fifth-generation (5G) ...mobile communications. Our proposed linearizer adopts a transformer-based (i.e., inductive) self-compensated predistortion network at the input of the PA whose amplitude-modulation to phase-modulation (AM-PM) response is opposite compared with the AM-PM response of a CMOS PA, resulting in an AM-PM cancellation effect. This proposed inductive linearization method mitigates the large gain reduction problem in traditional capacitor-based linearization approaches while consuming no extra dc power or without introducing additional control circuitry. As a result, a significant improvement in power-efficiency and linearity is achieved with high-order complex modulation signals. To validate the proposed linearization method, a PA prototype in 65-nm CMOS technology was fabricated and tested, and it exhibited <1° of <inline-formula> <tex-math notation="LaTeX">\vert </tex-math></inline-formula>AM-PM<inline-formula> <tex-math notation="LaTeX">\vert </tex-math></inline-formula> distortion at <inline-formula> <tex-math notation="LaTeX">P_{\mathrm {o,1\, dB}} </tex-math></inline-formula> over 4 GHz of bandwidth (27-31 GHz). At 28 GHz, the measured saturated <inline-formula> <tex-math notation="LaTeX">P_{\mathrm {o}} </tex-math></inline-formula> and peak power-added-efficiency (PAE) was 15.6 dBm and 41%, respectively, while achieving a 6-dB <inline-formula> <tex-math notation="LaTeX">P_{\mathrm {o}} </tex-math></inline-formula> back-off PAE of 25%. To assess PA's large-signal performance for 5G communications, the prototype was measured with the 64-quadratic-amplitude modulation (QAM) signal at 2-Gb/s data rates at 28 and 30 GHz, and the PA achieves modulated-PAE of 18.2%/17.6% and average-<inline-formula> <tex-math notation="LaTeX">P_{\mathrm {o}} </tex-math></inline-formula> of 9.8 dBm/10 dBm, respectively, while maintaining <−30 dBc of adjacent-channel-power-ratio and <−25.5 dB of error-vector-magnitude. The achieved modulated-PAE at 28 and 30 GHz shows more than <inline-formula> <tex-math notation="LaTeX">2\times </tex-math></inline-formula> improvement in comparison with the recently reported 28-GHz linear CMOS PAs. Also, the PA occupies a compact active-area of 0.24 mm 2 .
Orthogonal frequency division multiplexing with index modulation (OFDM-IM) performs transmission by considering two modes over OFDM subcarriers, which are the null and the conventional M-ary signal ...constellation. The spectral efficiency (SE) of the system, however, is limited, since the null mode itself does not carry any information and the number of subcarrier activation patterns increases combinatorially. In this paper, a novel IM scheme, called multiple-mode OFDM-IM (MM-OFDM-IM), is proposed for OFDM systems to improve the SE by conveying information through multiple distinguishable modes and their full permutations. A practical and efficient mode selection strategy, which is constrained on the phase shift keying/quadrature amplitude modulation constellations, is designed. Two efficient detectors that provide different tradeoffs between the error performance and detection complexity are also proposed. The principle of MM-OFDM-IM is further extended to the in-phase and quadrature components of OFDM signals, and the method of generating multiple modes from the M-ary pulse amplitude modulation constellation for this modified scheme is also introduced. Bit error rate (BER) analyses are provided for the proposed schemes. Monte Carlo simulations on BER corroborate the analyses and show that the proposed schemes appear as promising multi-carrier transmission alternatives by outperforming the existing OFDM-IM counterparts.
Recent studies of brain activities show that cross-frequency coupling (CFC) plays an important role in memory and learning. Many measures have been proposed to investigate the CFC phenomenon, ...including the correlation between the amplitude envelopes of two brain waves at different frequencies — cross-frequency amplitude–amplitude coupling (AAC). In this short communication, we describe how nonstationary, nonlinear oscillatory signals may produce spurious cross-frequency AAC. Utilizing the empirical mode decomposition, we also propose a new method for assessment of AAC that can potentially reduce the effects of nonlinearity and nonstationarity and, thus, help to avoid the detection of artificial AACs. We compare the performances of this new method and the traditional Fourier-based AAC method. We also discuss the strategies to identify potential spurious AACs.
•Nonstationary oscillations can induce spurious amplitude–amplitude coupling (AAC).•Nonlinear waveform can induce spurious AAC.•The EMD-based AAC method performs better than the Fourier-based AAC method.
A new coded modulation scheme is proposed. At the transmitter, the concatenation of a distribution matcher and a systematic binary encoder performs probabilistic signal shaping and channel coding. At ...the receiver, the output of a bitwise demapper is fed to a binary decoder. No iterative demapping is performed. Rate adaption is achieved by adjusting the input distribution and the transmission power. The scheme is applied to bipolar amplitudeshift keying (ASK) constellations with equidistant signal points and it is directly applicable to two-dimensional quadrature amplitude modulation (QAM). The scheme is implemented by using the DVB-S2 low-density parity-check (LDPC) codes. At a frame error rate of 10 -3 , the new scheme operates within less than 1.1 dB of the AWGN capacity 1/2 log 2 (1 + SNR) at any spectral efficiency between 1 and 5 bits/s/Hz by using only 5 modes, i.e., 4-ASK with code rate 2/3, 8-ASK with 3/4, 16-ASK and 32-ASK with 5/6, and 64-ASK with 9/10.
In order to realize probabilistically shaped signaling within the probabilistic amplitude shaping (PAS) framework, a shaping device outputs sequences that follow a certain nonuniform distribution. In ...case of constant-composition (CC) distribution matching (CCDM), the sequences differ only in the ordering of their constituent symbols, whereas the number of occurrences of each symbol is constant in every output block. Recent results by Amari et al. have shown that the CCDM block length can have a considerable impact on the effective signal-to-noise ratio (SNR) after fiber transmission. So far, no explanation for this behavior has been presented. Furthermore, the block-length dependence of the SNR seems not to be fully aligned with previous results in the literature. This paper is devoted to a detailed analysis of the nonlinear fiber interactions for CC sequences. We confirm in fiber simulations the inverse proportionality of SNR with CCDM block length and present two explanations. The first one, which only holds in the short-length regime, is based on how two-dimensional symbols are generated from shaped amplitudes in the PAS framework. The second, more general explanation relates to an induced shuffling within a sequence, or equivalently a limited concentration of identical symbols, that is an inherent property for short CC blocks, yet not necessarily present in case of long blocks. This temporal property results in weaker nonlinear interactions, and thus higher SNR, for short CC sequences. For a typical multi-span fiber setup, the SNR difference is numerically demonstrated to be up to 0.7 dB. Finally, we evaluate a heuristic figure of merit that captures the number of runs of identical symbols in a concatenation of several CC sequences. For moderate block lengths up to approximately 100 symbols, this metric suggests that limiting the number identical-symbol runs can be beneficial for reducing fiber nonlinearities and thus, for increasing SNR.
A dc-dc power converter based on a two-phase synchronous buck converter that reproduces single-carrier digital modulation schemes by controlling the first switching harmonic of the output voltage ...ripple is presented in this paper. The dc-dc power converter carries out both the lighting and the transmission functionalities of visible light communication transmitters. Control of both the amplitude and the phase of sinusoidal currents injected toward high-brightness LEDs enable the use of efficient modulation schemes, such as quadrature amplitude modulation, carrierless amplitude and phase modulation, amplitude-shift keying, and phase-shift keying. These modulation schemes achieve higher spectral efficiency (i.e., more data can be transmitted using the same bandwidth) than previously proposed modulation schemes performed by visible light communication transmitters based on the use of dc-dc power converters. To the authors' knowledge, the ratio between the bit rate achieved and the switching frequency of the dc-dc power converter presented in this paper is the highest that can be found in the literature.
This paper presents a 64-element 28-GHz phased-array transceiver for 5G communications based on <inline-formula> <tex-math notation="LaTeX">2\times 2 </tex-math></inline-formula> transmit/ receive ...(TRX) beamformer chips. Sixteen of the <inline-formula> <tex-math notation="LaTeX">2\times 2 </tex-math></inline-formula> TRX chips are assembled on a 12-layer printed circuit board (PCB) together with a Wilkinson combiner/divider network and 28-32-GHz stacked-patch antennas. The 64-element array results in 1.1 dB and 8.9° rms amplitude and phase error, respectively, with no calibration due to the symmetric design of the <inline-formula> <tex-math notation="LaTeX">2\times 2 </tex-math></inline-formula> beamformer chips and the PCB Wilkinson network. The effect of phase and amplitude mismatch between the 64 elements is analyzed and shown to have little impact on the 64-element array performance due to the averaging effects of phased arrays. Detailed pattern, effective isotropic radiated power (EIRP), and link measurements performed without any array calibration are presented and show the robustness of the symmetrical design technique. The phased array can scan to ±50° in azimuth (<inline-formula> <tex-math notation="LaTeX">H </tex-math></inline-formula>-plane) and ±25° in elevation (<inline-formula> <tex-math notation="LaTeX">E </tex-math></inline-formula>-plane) with low sidelobes and achieves a saturated EIRP of 52 dBm with 4-GHz 3-dB bandwidth. A 300-m wireless link is demonstrated with a record-setting data rate of 8-12 Gb/s over all scan angles using two 64-element TRX arrays and 16-/64-QAM waveforms.
The synchronised phasor measurement units (PMUs), serving as ‘GridEye’, provide data that improve the observability and controllability of the power grid due to its high accuracy and high-upload ...rate. However, missing or abnormal data may seriously affect its applications. This study proposes a method to recover the missing or abnormal amplitude data in PMU measurements (i.e. the active power, reactive power, positive sequence current, and voltage amplitude), based on the historical PMU data obtained from both ends of the line, which is independent of the transmission line parameters and the phase angle that may be influenced by synchronisation. First, the issues in the quality of measured PMU data are analysed, and the motivation of the proposed method is stated. Then, a method to screen out the bad data from the historical data is proposed based on the density-based spatial clustering of applications with noise. Furthermore, the model of data recovery is established, and the recovery method, which recovers the voltage amplitude, active power, reactive power, and current amplitude in sequence, using historical amplitude data to calculate related recovery coefficients is proposed. Finally, the effectiveness and practicability of the proposed method are verified by examples of simulation and measured data.
In the quantum noise stream cipher (QNSC) system, the low-order plaintext is encrypted by pre-shared keys into high-order ciphertext. However, high-speed optical communication systems have a huge ...demand for pre-shared keys. On the other hand, the separation of the secure communications sub-system from the secure key distribution (SKD) sub-system increases potential security risks and introduces additional resources overhead. In this letter, we propose an artificial amplitude noise-based SKD scheme (AAN-SKD) in QAM/QNSC to generate secret key for legal parties accordingly. The two orthogonal PAM symbols are superimposed to generate QAM symbols. Thus, the AAN-SKD can also be implemented in PAM modulation. In addition, the data transmission and AAN-SKD are completed in the same channel. Experimental results indicate that the key generation rate and key consistency ratio of the proposed scheme can reach 188.22 Mbit/s and 91%, respectively. Compared with quantum key distribution, the AAN-SKD has the advantage of lower cost, better compatibility, and a higher key rate.
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