CMOS Transmitter using Pulse-Width Modulation Pre-Emphasis achieving 33dB Loss Compensation at 5-Gb/s

A digital transmitter pre-emphasis technique is presented that is based on pulse-width modulation, instead of finite impulse response (FIR) filtering. The technique fits well to future high-speed low-voltage CMOS processes. A 0.13 /spl mu/m CMOS transmitter achieves more than 5 Gb/s (2-PAM) over 25 m of standard RG-58U low-end coaxial copper cable. The test chip compensates for up to 33 dB of channel loss at the fundamental signaling frequency (2.5 GHz), which is the highest figure compared to literature

Jitter Limitations on Multi-Carrier Modulation

A feasibility study is made of an OFDM system based on analog multipliers and integrate-and-dump blocks, targeted at Gb/s copper interconnects. The effective amplitude variation of the integrator output caused by jitter is explained in an intuitive way by introducing correlation plots. For a given rms jitter and error rate, high frequency carriers allow for less modulation depth than low frequency carriers. A jitter limit on the total system bit rate is calculated, which is a function of rms jitter, bandwidth, and specified system symbol error rate. It is concluded that, because of the high sensitivity to timing errors inherent in OFDM, traditional PAM systems with equal bandwidth and error rate are more feasible

Pulse-Width Modulation Pre Emphasis applied in a Wireline Transmitter, achieving 33dB Loss Compensation at 5-Gb/s in 0.13-μm CMOS

Abstract—A transmitter pre-emphasis technique for copper cable equalization is presented that is based on pulse-width modulation (PWM). This technique is an alternative to the usual 2-tap symbol-spaced FIR (SSF) pre-emphasis. The technique uses timing resolution instead of amplitude resolution to adjust the filter transfer function, and therefore fits well with future high-speed low-voltage CMOS processes. Spectral analysis and time domain simulations illustrate that PWM pre-emphasis offers more relative high frequency boost than 2-tap SSF. Only one coefficient needs to be set to fit the equalizer transfer function to the channel, which makes convergence of an algorithm for automatic adaptation straightforward. A proof-of-concept 0.13- m CMOS transmitter achieves in excess of 5 Gb/s (2-PAM) over 25 m of standard RG-58U low-end coaxial copper cable with 33 dB of channel loss at the Nyquist frequency (2.5 GHz). Measured BER at this speed and channel loss is 10 12

Wireline equalization using pulse-width modulation

Abstract-High-speed data links over copper cables can be effectively equalized using pulse-width modulation (PWM) pre-emphasis. This provides an alternative to the usual 2-tap FIR filters. The use of PWM pre-emphasis allows a channel loss at the Nyquist frequency of ~30dB, compared to ~20dB for a 2-tap symbol-spaced FIR filter. The use of PWM fits well with future high-speed low-voltage CMOS processes. The filter has only one ‘knob’, which is the duty-cycle. This makes convergence of an algorithm for automatic adaptation straightforward. Spectral analysis illustrates that, compared to a 2-tap FIR filter, the steeper PWM filter transfer function fits better to the copper channel. This applies to both half-symbol-spaced and symbol-spaced 2-tap FIR filters. Circuits for implementation are as straightforward as for FIR pre-emphasis. In this paper new measurements are presented for a previous transmitter chip, and a new high-swing transmitter chip is presented. Both coaxial and differential cables are used for the tests. A bit rate of 5 Gb/s (2-PAM) was achieved with all cable assemblies, over a cable length of up to 130 m. Measured BER at this speed is <10-12

Wireline Equalization using Pulse-Width Modulation

Copper channels suffer from attenuation and dispersion, caused by the skin effect and dielectric loss. Furthermore, they suffer from reflections, caused by impedance discontinuities. As a consequence, the achievable bit rate is limited by intersymbol interference: neighboring symbols interfere with each other. The aim of this research was to find new equalization and modulation techniques that can be used to increase the data rate over copper interconnects while maintaining an acceptable bit error rate. These techniques must be compatible with future CMOS generations

Data Communication in Read-Out Systems: How Fast Can We Go Over Copper Wires?

In a digital X-ray imaging system, data has to be transmitted from the detector to the storage system. In future digital X-ray imaging systems, higher data rates will be needed. For some applications, e.g. protein crystallography at synchrotron beams, data rates in the order of gigabits per second are expected. Present trend for such systems is to move from a parallel data bus towards a high-speed serial readout. For high speed signaling over short distances (up to 10 m) the attenuation of copper cables is low enough to permit multi-gigabit per second speeds. In this article, an overview will be given of problems encountered in high speed data transmission over copper cable and techniques will be shown to overcome these problems. The bandwidth bottleneck in short distance communication is in the IC-technology and not in the channel. The cable transfer function results in inter-symbol interference (ISI). The skin-effect is the most significant cause of ISI for short length (10 m) coaxial copper cables. Fortunately, equalization can compensate for these effects. An equalizer has a transfer function that is the inverse of the channel transfer function. With the correct equalizer, a very low Bit Error Ratio (BER) can be achieved. The measured RG-58U cable (τ1=0.12 ns) could transmit at a bit rate of 8.3 Gbps, with a BER of 10−12. Multi-gigabit speeds are possible over short length coaxial copper cables

Equalization of Skin Effect Loss Dominated Channels using Pulse-Width Modulation (PWM) Pre-Emphasis

A digital transmitter pre-emphasis technique is presented that is based on pulse-width modulation, instead of finite impulse response (FIR) filtering. The technique fits well to future high-speed low-voltage CMOS processes. A 0.13μm CMOS transmitter achieves more than 5Gb/s (2-PAM) over 25m of standard RG-58U low-end coaxial copper cable. The test chip compensates for up to 33dB of channel loss at the fundamental signaling frequency (2.5GHz), which is the highest figure compared to literature