Dictionary learning based reconstruction for distributed compressed video sensing

Distributed compressed video sensing (DCVS) is a framework that integrates both compressed sensing and distributed video coding characteristics to achieve a low-complexity video coding. However, how to design an efficient reconstruction by leveraging more realistic signal models that go beyond simple sparsity is still an open challenge. In this paper, we propose a novel “undersampled” correlation noise model to describe compressively sampled video signals, and present a maximum-likelihood dictionary learning based reconstruction algorithm for DCVS, in which both the correlation and sparsity constraints are included in a new probabilistic model. Moreover, the signal recovery in our algorithm is performed during the process of dictionary learning, instead of being employed as an independent task. Experimental results show that our proposal compares favorably with other existing methods, with 0.1–3.5 dB improvements in the average PSNR, and a 2–9 dB gain for non-key frames when key frames are subsampled at an increased rate.     

Free-viewpoint depth image based rendering

In 3D TV research, one approach is to employ multiple cameras for creating a 3D multi-view signal with the aim to make interactive free-viewpoint selection possible in 3D TV media. This paper explores a new rendering algorithm that enables to compute a free-viewpoint between two reference views from existing cameras. A unique property is that we perform forward warping for both texture and depth simultaneously. Advantages of our rendering are manyfold. First, resampling artifacts are filled in by inverse warping. Second, disocclusions are processed while omitting warping of edges at high discontinuities. Third, our disocclusion inpainting approach explicitly uses depth information. We obtain an average PSNR gain of 3 dB and 4.5 dB for the ‘Breakdancers’ and ‘Ballet’ sequences, respectively, compared recently published results. Moreover, experiments are performed using compressed video from surrounding cameras. The overall system quality is dominated by rendering quality and not by coding.     

A PAPR reduction technique using Hadamard transform combined with clipping and filtering based on DCT/IDCT for IM/DD optical OFDM systems

In Intensity Modulator/Direct Detection (IM/DD) optical OFDM systems, the high peak-to-power average ratio (PAPR) will cause signal impairments through the nonlinearity of modulator and fiber. In this paper, a joint PAPR reduction technique based on Hadamard transformation and clipping and filtering using DCT/IDCT transform has been proposed for mitigating the impairments in IM/DD optical OFDM system. We then experimentally evaluated the effect of PAPR reduction on the bit error rate (BER) performance and the results show the effectiveness of the proposed technique. At a bit error rate (BER) of 1 × 10⁻³, the receiver sensitivity of the proposed 2.5 Gb/s IM/DD optical OFDM system after 100-km standard single-mode fiber transmission has been improved by 0.8 dB, 1.3 dB and 3.1 dB for a launch power of 6.4 dBm, 8 dBm and 10 dBm respectively when compared with the classical system.     

Gain characteristics of quantum dot fiber amplifier based on asymmetric tapered fiber coupler

We theoretically analyzed the gain characteristics of an integrated semiconductor quantum dot (QD) fiber amplifier (SQDFA) by using a 2 × 2 tapered fiber coupler with a PbS QD-coated layer. The asymmetric structure of the fiber coupler is designed to have a maximum working bandwidth around 1550-nm band and provide a desired optical power ratio of the output signals. By using 600 mW of 980-nm pump, 10 dB gain of a 1550-nm signal is estimated with the gain efficiency of 4.5 dB/cm.     

All-optical four-wavelength 2R regeneration based on data-pump four-wave-mixing with offset filtering

A simultaneous all-optical 2R regeneration of 4 × 12.5 Gb/s return-to-zero (RZ) signals is demonstrated based on the data-pump four-wave-mixing in a single highly nonlinear fiber, in which the channel spacing and duty cycle are 200 GHz and 50%. Both the bidirectional configuration and time-interleaved technology are used to reduce the crosstalk from other channels. For further improving the performance of the multichannel regenerator, an offset filtering (OF) method is employed to minimize the influence from the opposite input signal. Our experiments show that the extinction ratio (ER) of regenerated signals is about two times larger than that of the degraded signals and the maximum ER improvement is about 6.5 dB. By using the offset filtering method, the sensitivity improvements of four-wavelength regenerated signals are 2.05 dB, 2.53 dB, 3.57 dB and 2.8 dB, respectively.     

A low-voltage low-power CMOS fully differential linear transconductor with mobility reduction compensation

A highly linear fully differential CMOS transconductor architecture based on flipped voltage follower (FVF) is proposed. The linearity of the proposed architecture is improved by mobility reduction compensation technique. The simulated total harmonic distortion (THD) of the proposed transconductor with 0.4V_pp differential input is improved from ?42 dB to ?55 dB while operating from 1.0 V supply. As an example of the applications of the proposed transconductor, a 4th-order 5 MHz Butterworth Gm-C filter is presented. The filter has been designed and simulated in UMC 130 nm CMOS process. It achieves THD of ?53 dB for 0.4V_pp differential input. It consumes 345 μw from 1.0 V single supply. Theoretical and simulated results are in good agreement.     

115 Gbit/s downstream and 10 Gbit/s upstream TWDM-PON together with 11.25 Gbit/s wireless signal utilizing OFDM-QAM modulation

In this work, we propose and investigate a 115 Gbit/s (4 × 28.75 Gbit/s) downstream and 10 Gbit/s upstream time- and wavelength-division-multiplexing passive optical network (TWDM-PON) together with 11.25 Gbit/s wireless broadcasting signal using multi-band orthogonal-frequency-division-multiplexing (OFDM) modulation within 10 GHz bandwidth. Here, to compensate the power fading and chromatic dispersion in the higher frequency, we utilize a −0.7 chirp parameter Mach–Zehnder modulator (MZM) for the OFDM signal. Hence, negative power penalties of −0.3 and −0.4 dB in the downstream and broadcasting wireless signals; and power penalty of 0.3 dB in the upstream signal are measured at the bit error rate (BER) of 3.8 × 10⁻³ after 20 km standard single mode fiber transmission without dispersion compensation.     

Experimental evaluation of prefiltering for 56 Gbaud DP-QPSK signal transmission in 75 GHz WDM grid

We investigate optical prefiltering for 56 Gbaud (224 Gbit/s) electrical time-division multiplexed (ETDM) dual polarization (DP) quaternary phase shift keying (QPSK) transmission. Different transmitter-side optical filter shapes are tested and their bandwidths are varied. Comparison of studied filter shapes shows an advantage of a pre-emphasis filter. Subsequently, we perform a fiber transmission of the 56 Gbaud DP QPSK signal filtered with the 65 GHz pre-emphasis filter to fit the 75 GHz transmission grid. Bit error rate (BER) of the signal remains below forward error correction (FEC) limit after 300 km of fiber propagation.     

On design of a novel class of selective CIC FIR filter functions with improved response

The Cascaded-Integrator-Comb (CIC) filter is a non-recursive (FIR) filter which is multiplier free, consisting only of two building blocks (simple integrator stage and simple comb filter stage) and has a linear phase. This paper summarizes some key points of classical CIC filters and proposes a novel class of CIC FIR filter functions. A novel class of CIC filter functions maintains simplicity of FIR filters by avoiding the multipliers, but shows excellent performances in term of insertion loss in stopband and selectivity with respect to conventional CIC filters. A set of simulations along with illustrative examples is conducted in order to compare the attenuation characteristics of the classical CIC filter functions and the proposed novel class of selective CIC FIR filter functions. For the same level of a constant group delay τ = 45.5 s, a classical CIC filter function has insertion loss of 166.3 dB, and designed novel filter function has a higher level of insertion loss 206.55 dB.     

A sub-sampling 4.25 GS/s 3-bit flash ADC with asymmetric spatial filter response

A sub-sampling 3-bit 4.25 GS/s flash ADC with a novel averaging termination technique—asymmetric spatial filter response—in 0.13 um CMOS for impulse radio ultra-wideband (IR-UWB) receiver is presented. In this design, a track and hold (T/H) circuit with self-biased buffer is used to compensate the degradation in amplitude when frequency increases to giga Hz. Averaging termination technique using asymmetric spatial filter response is proposed to relieve the termination offset of the flash ADC. A revised encoder scheme is adopted to solve the problem of different propagation delay. The measurement results reveal that the SFDR and SNDR of the ADC are 26.3 dB and 18.4 dB, respectively, even the input signal frequency is 4.2 GHz. INL and DNL are measured improved to 0.11LSB and 0.18LSB, respectively, when asymmetric spatial filter is used. The power of ADC is 63 mW and the active area is 0.49×0.72 mm². The ADC achieves a figure of merit (FoM) of 2.2 pJ/conversion-step.     

Joint adaptive code rate technique and bit interleaver for direct-detection optical OFDM system

In this paper, we have theoretically analyzed that the existence of inter-subcarrier mixing interferences (ISMI) and frequency selective fading (FF) in the directed-detection optical orthogonal-frequency-division-multiplexing (DDO-OFDM) system will cause an unbalanced error distribution and degrade the system performance. Then we propose to employ the adaptive code rate technique (ACT) and bit interleaver in the DDO-OFDM system to combat ISMI and FF. The experimental results show that the receiver sensitivity of 5.9-Gb/s 64-ary quadrature-amplitude-modulation (64QAM) OFDM signal employing ACT(9.43 Gb/s after encoding) is improved more than 2 dB compared with the 5.9-Gb/s OFDM signal with 0.66 turbo coding rate (8.85 Gb/s after encoding) at the bit-error ratio (BER) of 1e-4. When the coding rate is all 0.625, the OFDM signal employing ACT has more than 1-dB gain improvement compared with the OFDM signal encoded with fixed-rate turbo coding. And additional ∼1-dB receiver sensitivity improvement is enabled when the OFDM signal employ ACT and bit-interleaver simultaneously.     

An automatic region-based video sequence codec based on fractal compression

In order to improve the performance of fractal video coding, we explore a novel fractal video sequences codec with automatic region-based functionality. To increase the quality of decoding image, intra frame coding, deblocking loop filter and sub-pixel block matching are applied to the codec. An efficient searching algorithm is used to increase the compression ratio and encoding speed. Automatic region-based fractal video sequences coding reduces coding stream greatly. Experimental results indicate that the proposed algorithm is more robust, and provides much less encoding time and bitrate while maintaining the quality of decompression image than the conventional CPM/NCIM method and other related references. We compare the proposed algorithm with three algorithms in Refs. [24], [25], [26], and the results of all these four algorithms are compared with H.264. The bitrate of the proposed algorithm is decreased by 0.11% and the other algorithms are increased by 4.29%, 6.85% and 11.62%, respectively. The average PSNR degradations of the four algorithms are 0.71 dB, 0.48 dB, 0.48 dB and 0.75 dB. So the bitrate of the proposed algorithm is decreased and the other algorithms are increased. At the meantime the compression time is reduced greatly, about 79.19% on average. The results indicate that, on average, the proposed automatic region-based fractal video sequences coding system can save compression time 48.97% and bitrate 52.02% with some image quality degradation in comparison with H.264, since they are all above 32 dB and the human eyes are insensitive to the differences.     

Design of microstrip wide stopband quad-band bandpass filters for multi-service communication systems

This paper presents two planar high performance quad-channel bandpass filters, which are designed based on a novel circular multi-mode resonator. In this paper and for the first time, the proposed resonator is utilized to achieve quad passbands. It consists of diverged feeding lines that are coupled to etched circular cells. The first filter has quite close channels at 2.62, 2.88, 4.34 and 4.67 GHz, which make it appropriate for frequency division duplex (FDD) scheme. Meanwhile, the second filter is designed for WCDMA and WiMAX applications. Both filters are able to attenuate the harmonics up to 19 GHz with a maximum harmonic level of −20 dB. The insertion losses and return losses of both filters at all channels are better than 1.2 dB and 17.5 dB, respectively. The harmonic attenuation method is presented employing a LC equivalent circuit of the proposed resonator. In order to verify the designing methodology, the proposed filters are fabricated and measured where there are good agreements between the simulation and measurement results.     

Active damping of a piezoelectric tube scanner using self-sensing piezo actuation

In most Atomic Force Microscopes (AFM), a piezoelectric tube scanner is used to position the sample underneath the measurement probe. Oscillations stemming from the weakly damped resonances of the tube scanner are a major source of image distortion, putting a limitation on the achievable imaging speed. This paper demonstrates active damping of these oscillations in multiple scanning axes without the need for additional position sensors. By connecting the tube scanner in a capacitive bridge circuit the scanner oscillations can be measured in both scanning axes, using the same piezo material as an actuator and sensor simultaneously. In order to compensate for circuit imbalance caused by hysteresis in the piezo element, an adaptive balancing circuit is used. The obtained measurement signal is used for feedback control, reducing the resonance peaks in both scanning axes by 18 dB and the cross-coupling at those frequencies by 30 dB.Experimental results demonstrate a significant reduction in scanner oscillations when applying the typical triangular scanning signals, as well as a strong reduction in coupling induced oscillations. Recorded AFM images show a considerable reduction in image distortion due to the proposed control method, enabling artifact free AFM-imaging at a speed of 122 lines per second with a standard piezoelectric tube scanner.     

Compact circular-patch-based bandpass filter for ultra-wideband wireless communication systems

Ultra-wideband (UWB) is a radio technology that enables low-power-level, short-range, and wide-bandwidth communication, and it has been widely applied in personal area networks, precision geolocation, medical, surveillance, and vehicular radar systems. Since Federal Communications Commission released the unlicensed use of the UWB range (3.1–10.6 GHz), a significant attention has been paid to the development of UWB devices, particularly UWB bandpass filters. In this paper, we propose a novel UWB bandpass filter based on circular patch resonator that is grounded by via and perturbed by slits and defected ground structures. The resonator’s behaviour is analysed in detail and it is shown that its specific configuration allows a flexible control of the three lowest resonant modes, which are used to form UWB passband. To demonstrate the potential of the resonator, a UWB filter has been designed, fabricated, and measured. The filter is characterized by the insertion loss lower than 1 dB and return loss higher than 17 dB within the passband, as well as by very small group delay variation of only 0.07 ns. Also, the filter exhibits suppression higher than 19 dB up to 30 GHz, and very small overall dimensions of only 0.31λ_g × 0.31λ_g, and thus it outperforms other published UWB filters.     

No-reference analysis of decoded MPEG images for PSNR estimation and post-processing

We propose no-reference analysis and processing of DCT (Discrete Cosine Transform) coded images based on estimation of selected MPEG parameters from the decoded video. The goal is to assess MPEG video quality and perform post-processing without access to neither the original stream nor the code stream. Solutions are presented for MPEG-2 video. A method to estimate the quantization parameters of DCT coded images and MPEG I-frames at the macro-block level is presented. The results of this analysis is used for deblocking and deringing artifact reduction and no-reference PSNR estimation without code stream access. An adaptive deringing method using texture classification is presented. On the test set, the quantization parameters in MPEG-2 I-frames are estimated with an overall accuracy of 99.9% and the PSNR is estimated with an overall average error of 0.3 dB. The deringing and deblocking algorithms yield improvements of 0.3 dB on the MPEG-2 decoded test sequences.     

A low power and small area digital self-calibration technique for pipeline ADC

A digital self-calibration implementation with discontinuity-error and gain-error corrections for a pipeline analog-to-digital converter (ADC) is presented. In the proposed calibration method, the error owing to each reference unit capacitor of the multiplying D/A converter is measured separately using a calibration capacitor and an enhanced resolution back-end pipeline ADC acting as an error quantizer. The offset and finite open loop DC-gain of the operational amplifier and capacitor mismatches, the reference voltage mismatch can all be calibrated. The calibration can be achieved by that only used addition and subtraction. Hence, it needs low power and area consuming. A prototype ADC with the proposed calibration was fabricated on a 0.5 μm double-poly triple-metal CMOS process. The power consumption and area of the calibration circuit are only 10.1 mW and 1.05 mm², respectively. At a sampling rate of 30 MS/s, the calibration improves the DNL and INL from 2.59 LSB and 14.98 LSB to 0.72 LSB and 1.82 LSB, respectively. For a 1.25 MHz sinusoidal signal, the calibration improves the signal-to-noise-distortion ratio and spurious-free dynamic range from 43.1 dB and 52.1 dB to 75.51 dB and 83.61 dB, respectively. The 12.25 effective number of bits at 30 MS/s ADC consumes a total power of 136 mW.     

Low power dissipation SiGe HBT dual-band variable gain amplifier

A dual-band variable gain amplifier operating at 0.9 GHz and 2.4 GHz was designed based on high performance RF SiGe HBT for large amount of signals transmission and analysis. Current steering was adopted in gain-control circuit to get variable trans-conductance and then variable gain. Emitter degeneration and current reuse were considered in amplifying stage for low noise figure and low power dissipation respectively. A single-path circuit resonating at two frequency points simultaneously was designed for input impedance matching. PCB layout parasitic effects, especially the via parasitic inductor, were analyzed theoretically and experimentally and accounted for using electro-magnetic (EM) simulation. The measurement results show that a dynamic gain control of 26 dB/16 dB in a control voltage range of 0.0–1.4 V has been achieved at 0.9/2.4 GHz respectively. Both S₁₁ and S₂₂ are below than –10 dB in all the control voltage range. Noise figures at both 0.9 GHz and 2.4 GHz are lower than 5 dB. Total power dissipation of the dual-band VGA is about 16.5 mW at 3 V supply.     

Compact differential bandpass filter with a narrow notched band using APCL structure suitable for UWB application

A compact differential band pass filter with asymmetric parallel-coupled lines (APCL) and center frequency of 5.6 GHz is proposed in this paper. The APCL suppresses unwanted RFID signals by introducing a fully tunable notched band at 6.8 GHz. By combining the concept of transmission matrix with modal analysis and extracting a novel model for symmetric three parallel coupled lines (SPCL), role of each resonant frequency is clearly explained. Measurement results in the differential mode show a pass band from 3.1 to 8.1 GHz and a wide stop band from 9.1 to 16 GHz with attenuation of more than 20 dB. In addition, S₂₁ in common mode is lower than −10.5 dB over the pass band.     

All-optical clock extraction from 40-Gbit/s NRZ data using cascaded long-period fiber grating

All-optical clock extraction from a 40-Gbit/s NRZ input signal is demonstrated using a cascaded long-period fiber grating (CLPG) and a mode-locked fiber ring laser. The CLPG has a Mach–Zehnder configuration with two arms along the core and cladding regions. Using the difference in propagation delay between two arms, the non-return-to-zero (NRZ) signal is converted to the pseudo-return-to-zero (PRZ) signal. To obtain repetitive pulses as a clock signal from the PRZ signal, a ring laser with a semiconductor optical amplifier (SOA) is used. Subsequently, the measured carrier-to-noise ratio (CNR) of the PRZ and clock signals are enhanced up to 30 dB and 31 dB, respectively, compared to that of the original NRZ signal. Also, the clock signal centered at 40 GHz has a low timing jitter of <1.3 ps. It is expected that this method can be applied to high speed fiber-optic systems of >40 Gbit/s due to its small time delay between the core and cladding regions.