Integrated Transversal Equalizers in High-Speed Fiber-Optic Systems

Intersymbol interference (ISI) caused by intermodal dispersion in multimode fibers is the major limiting factor in the achievable data rate or transmission distance in high-speed multimode fiber-optic links for local area networks applications. Compared with optical-domain and other electrical-domain dispersion compensation methods, equalization with transversal filters based on distributed circuit techniques presents a cost-effective and low-power solution. The design of integrated distributed transversal equalizers is described in detail with focus on delay lines and gain stages. This seven-tap distributed transversal equalizer prototype has been implemented in a commercial 0.18-µm SiGe BiCMOS process for 10-Gb/s multimode fiber-optic links. A seven-tap distributed transversal equalizer reduces the ISI of a 10-Gb/s signal after 800 m of 50-µm multimode fiber from 5 to 1.38 dB, and improves the bit-error rate from about 10^-5 to less than 10^-12

Equalization of Third-Order Intermodulation Products in Wideband Direct Conversion Receivers

This paper reports a SAW-less direct-conversion receiver which utilizes a mixed-signal feedforward path to regenerate and adaptively cancel IM3 products, thus accomplishing system-level linearization. The receiver system performance is dominated by a custom integrated RF front end implemented in 130-nm CMOS and achieves an uncorrected out-of-band IIP3 of -7.1 dBm under the worst-case UMTS FDD Region 1 blocking specifications. Under IM3 equalization, the receiver achieves an effective IIP3 of +5.3 dBm and meets the UMTS BER sensitivity requirement with 3.7 dB of margin

A 24-GHz SiGe Phased-Array Receiver—LO Phase-Shifting Approach

A local-oscillator phase-shifting approach is introduced to implement a fully integrated 24-GHz phased-array receiver using an SiGe technology. Sixteen phases of the local oscillator are generated in one oscillator core, resulting in a raw beam-forming accuracy of 4 bits. These phases are distributed to all eight receiving paths of the array by a symmetric network. The appropriate phase for each path is selected using high-frequency analog multiplexers. The raw beam-steering resolution of the array is better than 10 [degrees] for a forward-looking angle, while the array spatial selectivity, without any amplitude correction, is better than 20 dB. The overall gain of the array is 61 dB, while the array improves the input signal-to-noise ratio by 9 dB

A Software Defined Radio Platform with Direct Conversion: SOPRANO

A new software defined radio platform with multiport-based direct conversion is proposed, named SOPRANO (Software Programmable and Hardware Reconfigurable Architecture for Network). The main features of SOPRANO are a high-level design methodology for digital circuits, a new mixer-less direct conversion method, and software algorithms for multi-band and multi-mode operation. We built the first prototype SOPRANO 1.0, which was able to receive PSK and QAM signals with two different carrier frequencies at 2.45 GHz and 5.25 GHz by changing signal processing software

A Fully-Integrated Reconfigurable Dual-Band Transceiver for Short Range Wireless Communications in 180 nm CMOS

© 2015 IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other users, including reprinting/ republishing this material for advertising or promotional purposes, creating new collective works for resale or redistribution to servers or lists, or reuse of any copyrighted components of this work in other works.A fully-integrated reconfigurable dual-band (760-960 MHz and 2.4-2.5 GHz) transceiver (TRX) for short range wireless communications is presented. The TRX consists of two individually-optimized RF front-ends for each band and one shared power-scalable analog baseband. The sub-GHz receiver has achieved the maximum 75 dBc 3rd-order harmonic rejection ratio (HRR3) by inserting a Q-enhanced notch filtering RF amplifier (RFA). In 2.4 GHz band, a single-ended-to-differential RFA with gain/phase imbalance compensation is proposed in the receiver. A ΣΔ fractional-N PLL frequency synthesizer with two switchable Class-C VCOs is employed to provide the LOs. Moreover, the integrated multi-mode PAs achieve the output P1dB (OP1dB) of 16.3 dBm and 14.1 dBm with both 25% PAE for sub-GHz and 2.4 GHz bands, respectively. A power-control loop is proposed to detect the input signal PAPR in real-time and flexibly reconfigure the PA's operation modes to enhance the back-off efficiency. With this proposed technique, the PAE of the sub-GHz PA is improved by x3.24 and x1.41 at 9 dB and 3 dB back-off powers, respectively, and the PAE of the 2.4 GHz PA is improved by x2.17 at 6 dB back-off power. The presented transceiver has achieved comparable or even better performance in terms of noise figure, HRR, OP1dB and power efficiency compared with the state-of-the-art.Peer reviewe

A 10-Gb/s two-dimensional eye-opening monitor in 0.13-μm standard CMOS

An eye-opening monitor (EOM) architecture that can capture a two-dimensional (2-D) map of the eye diagram of a high-speed data signal has been developed. Two single-quadrant phase rotators and one digital-to-analog converter (DAC) are used to generate rectangular masks with variable sizes and aspect ratios. Each mask is overlapped with the received eye diagram and the number of signal transitions inside the mask is recorded as error. The combination of rectangular masks with the same error creates error contours that overall provide a 2-D map of the eye. The authors have implemented a prototype circuit in 0.13-μm standard CMOS technology that operates up to 12.5 Gb/s at 1.2-V supply. The EOM maps the input eye to a 2-D error diagram with up to 68-dB mask error dynamic range. The left and right halves of the eyes are monitored separately to capture horizontally asymmetric eyes. The chip consumes 330 mW and operates reliably with supply voltages as low as 1 V at 10 Gb/s. The authors also present a detailed analysis that verifies if the measurements are in good agreement with the expected results

Nonlinear interference suppressor for varying-envelope local interference in multimode transceivers

In multimode transceivers, a local transmitter may induce a large interference in a local receiver, often several orders of magnitude stronger than the desired received signal. To suppress this interference by linear filtering, the receiver would need a very large dynamic range, resulting in excessive power consumption. A potentially much more power-efficient approach uses an adaptive memoryless nonlinearity that can strongly suppress the interference when adapted proportional to the envelope of the received interference. This approach has so far been limited to constant-envelope interferences owing to the difficulty of extracting accurate interference envelope information from the received signal. In this paper, we observe that in multimode transceivers the locally available baseband interference enables accurate adaptation for varying-envelope interferences. We identify and analyze nonlinear distortion products which are negligible for constant-envelope interferences. We show that adequate interference suppression can be achieved along with a negligible distortion to the desired signal