Designing training sequences for carrier frequency estimation in frequency-selective channels

A procedure for selecting a training sequence (TS) is developed for frequency estimation in frequency-selective channels. An expression for the unconditional Crame/spl acute/r-Rao bound (UCRB) is obtained by averaging the CRB for frequency estimation over the probability density function of Gaussian random channels. In addition, a necessary and sufficient condition for minimizing the UCRB is derived. Based on these results, a procedure for selecting a TS is developed. Through a computer search, binary TSs up to length 24 are found and tabulated. It is observed that periodic TSs tend to be selected when the TS length is twice the channel duration. Simulation results demonstrate that the proposed TSs can enhance the performance of the maximum likelihood (ML) frequency estimate.     

Low-power high-slew-rate CMOS buffer amplifier for flat panel display drivers

A new high-slew-rate CMOS buffer amplifier consuming a very small quiescent current is proposed. This buffer amplifier recursively copies the output driving current and increases the tail current of the input differential pair during slewing. Since the proposed buffer has a possible slew rate higher than 10 V//spl mu/s for a load capacitance of 1 nF almost independently of static currents as low as 1 /spl mu/A, this buffer amplifier is promising for column driver ICs of flat panel displays that require low static power consumption, high current driving capabilities, and small silicon areas.     

A 13-dB IIP3 improved low-power CMOS RF programmable gain amplifier using differential circuit transconductance linearization for various terrestrial mobile D-TV applications

A CMOS RF digitally programmable gain amplifier (RF PGA), covering various terrestrial mobile digital TV standards (DMB, ISDB-T, and DVB-H) is implemented as a part of a low-IF tuner IC using 0.18-/spl mu/m CMOS technology. An improvement of 13-dB IIP3 is attained without significant degradation of other performance criteria like gain, noise figure, common-mode rejection ratio, etc., at similar power consumption. This is achieved by applying a newly proposed differential circuit gm" (the second derivatives of transconductance) cancellation technique, called the differential multiple gated transistor (DMGTR). In the DMGTR amplifier, the negative value of gm" in the fully differential amplifier can be compensated by the positive value of gm" in the pseudo differential amplifier which is properly sized and biased. By adopting the DMGTR, a low-power highly linear RF PGA is implemented. Also, in order to have wide gain range with fine step resolution, a new RF PGA architecture is proposed. The measurement results of the proposed RF PGA exhibit 50-dB gain range with 0.25-dB resolution, 4.5-dB noise figure, a -4-dBm IIP3 (maximum 30 dBm) and 25-dB gain at 16-mW power consumption.     

A novel way to improve the dispersion-limited transmission distance of electroabsorption modulated lasers

We propose and demonstrate a way to improve the dispersion-limited reach of electroabsorption modulated lasers (EMLs). We generate continuous-phase frequency-shift keying/amplitude-shift keying (ASK) signals with the EML by applying a small current modulation to the laser diode (LD) on top of electroabsorption-modulated ASK signals. The amount of frequency deviation induced by the current modulation is adjusted to have the EML output signals experience /spl pi/ phase shift at every space. The experimental demonstration shows that with the proposed scheme we can increase the dispersion-limited transmission distance of the EML-based transmitter by 25%-75%, and it can be further improved by employing an LD with flat frequency-modulation response.     

Metal-defined polymeric variable optical attenuator

A variable optical attenuator (VOA) based on a metal-defined polymeric optical waveguide has been demonstrated for the first time. The metal film stressor deposited on top of the upper cladding layer not only produces the refractive index change within the core layer, but also acts as a thin-film heater allowing thermal tuning of the optical power within a metal-defined optical waveguide. Fabricated devices exhibit greater than 25 dB of optical attenuation with an applied electrical current of /spl sim/40 mA at 1550-nm wavelength. The switching speed of the VOA exhibits 800 /spl mu/s of rising and 720 /spl mu/s of falling time.     

A 60-GHz point-to-multipoint millimeter-wave fiber-radio communication system

A 60-GHz point-to-multipoint wireless access link with data rate of 156 Mb/s incorporating 60-GHz transceiver modules and full-duplex fiber-optic millimeter-wave transmission is developed for short-range applications such as indoor wireless local area networks and intelligent transport systems. For compact system configuration, a small-size millimeter-wave transceiver module with planar antennas is developed. The transceiver module is based on broadband planar integration and packaging of millimeter-wave circuits. The RF output power is +10 dBm and the measured 3-dB antenna beamwidth is 30/spl deg/. The total size of the developed 60-GHz transceiver module, except input and output connectors, is 50 mm /spl times/ 75 mm /spl times/ 35 mm. A point-to-point full duplex fiber-optic configuration is extended to the scheme with multiple access points (APs) by using a tree coupler and a dense wavelength division multiplexing multiplexer. The AP has a simple configuration without frequency conversion. The bit error rate and packet error rate performances of the 60-GHz fiber-radio access link are evaluated. Furthermore, the effect of the extension to the scheme with multiple APs is investigated.     

Enhanced-xVSB system development for improving ATSC terrestrial DTV transmission standard

This paper describes advanced dual stream system for improving mobile/pedestrian reception performance to the ATSC DTV 8-VSB transmission standard. E-xVSB system can transmit a mixture of normal (8-VSB) stream and enhanced (robust) stream. The robust stream has a higher threshold of visibility (TOV) compared to the standard stream, and legacy receivers ignore the robust packets. Thus, Enhanced-xVSB system is fully backward compatible with a current ATSC standard. For more robust transmission support, E-xVSB system adopts a reduced constellation method as well as enhanced trellis-coded modulation scheme. E-xVSB system supports a variety of enhanced modulation schemes: Pseudo-2VSB, Enhanced-4VSB, modified Enhanced-8VSB and Hybrid-VSB. Proposed system has been tested in the Lab, and the testing results are shown in this paper.     

A 10-bit 400-MS/s 160-mW 0.13-/spl mu/m CMOS dual-channel pipeline ADC without channel mismatch calibration

This paper describes a 10-bit 400-MS/s dual-channel analog-to-digital converter (ADC) insensitive to offset, gain, and sampling-time mismatches between channels. An adaptive closed-loop sampling technique based on a multi-stage amplifier eliminates the channel offset effectively. Multi-stage amplifiers with high DC gain reduce the gain mismatch between channels and guarantee a large signal swing at low supply voltages. A single clock-edge sampling scheme for clock-skew reduction minimizes the sampling-time mismatch. The proposed prototype ADC in a 0.13-/spl mu/m CMOS process occupies an active area of 4.2mm/sup 2/, dissipates 160mW from 1.2 V and 400 MS/s, and shows a signal-to-noise-and-distortion ratio of 54.8 dB with a 29-MHz sinusoidal input at 400 MS/s without any channel-mismatch calibration technique. The measured maximum offset and gain mismatches are less than 0.1% and 0.2%, respectively.     

Impedance matching by series condensers for power receivers of in vivo robotic capsules

An impedance matching technique using series condensers for the power receivers of in vivo robotic capsules is proposed. The power delivery function of the condenser ratio and its optimal ratio are derived. Experimental results validate the derived function.     

Modeling and measurement of simultaneous switching noise coupling through signal via transition

The signal via is a heavily utilized interconnection structure in high-density System-on-Package (SoP) substrates and printed circuit boards (PCBs). Vias facilitate complicated routings in these multilayer structures. Significant simultaneous switching noise (SSN) coupling occurs through the signal via transition when the signal via suffers return current interruption caused by reference plane exchange. The coupled SSN decreases noise and timing margins of digital and analog circuits, resulting in reduction of achievable jitter performance, bit error ratio (BER), and system reliability. We introduce a modeling method to estimate SSN coupling based on a balanced transmission line matrix (TLM) method. The proposed modeling method is successfully verified by a series of time-domain and frequency-domain measurements of several via transition structures. First, it is clearly verified that SSN coupling causes considerable clock waveform distortion, increases jitter and noise, and reduces margins in pseudorandom bit sequence (PRBS) eye patterns. We also note that the major frequency spectrum component of the coupled noise is one of the plane pair resonance frequencies in the PCB power/ground pair. Furthermore, we demonstrate that the amount of SSN noise coupling is strongly dependent not only on the position of the signal via, but also on the layer configuration of the multilayer PCB. Finally, we have successfully proposed and confirmed a design methodology to minimize the SSN coupling based on an optimal via positioning approach.