Active Delay Line Research Articles

5-GHz Injection-Locked Delay Cell With 10–25 ns Adjustable Group Delay in SiGe BiCMOS

This paper presents an on-chip delay line (DL) unit with an adjustable group delay (GD) between 10 and 25 ns. This active DL is designed based on an injection locked voltage-controlled oscillator (ILVCO) topology, with operation frequency of 5 GHz. Analog GD tuning is achieved through the control voltage of the VCO and the power of the injected signal. The free running phase noise (PN) of the DL at 100 kHz and 10 MHz offsets are -98 and -140 dBc/Hz, respectively, and the DL PN follows the PN of the injected signal in the locked mode. The DL was implemented in a 130-nm SiGe BiCMOS platform, and consumes 1.26 mm2 of silicon area. The power dissipation of the VCO core and buffer stage are 1.68 and 17.7 mW, respectively. To the authors best knowledge, the proposed DL achieves one of the highest GDs among the integrated DL cells.

Tunable plasmon-induced transparency and slow light in terahertz chipscale semiconductor plasmonic waveguides

We numerically propose plasmon-induced transparency (PIT) and the slow light effect based on a terahertz (THz) chipscale plasmonic semiconductor-insulator-semiconductor waveguide system. Via the coupling between two stub resonators, PIT is introduced due to the destructive interference, which can be theoretically described by the transmission-line method. Meanwhile, the strong dispersion within the transparent window will lead to the slow light effect. Via tuning the geometric parameters, the profile of PIT as well as group delay line can be arbitrarily tailored. Moreover, active control of both PIT and slow light can be realized by changing the ambient temperature. Especially, by integrating monolayer graphene into the structure, PIT and slow light can also be electrically modulated via applying voltage. This work provides geometrical, thermal and electrical approaches to manipulate THz transmission and group delay in the subwavelength scale, and can find potential applications as filters, sensors, modulators and active optical delay lines in THz ultracompact circuits.

Tunable Optical OFDM Demultiplexer Utilizing Slab Star Coupler-Based Optical DFT Circuit

We report on a tunable integrated-optic circuit for demultiplexing optical orthogonal frequency division multiplexing (OFDM) signals with various number of sub-carrier channels. The demultiplexer is composed of tunable optical discrete Fourier transform filter (tunable couplers, delay lines, and a slab star coupler) and optical gates. Various sub-carrier number optical OFDM signals can be demultiplexed by selecting the active delay lines with the tunable couplers. After explaining the demultiplexer and its operating principle, we show some experimental results including transmittance and bit error rate measurement of demultiplexed sub-carriers from various sub-carrier number optical OFDM signals. $2 \times 10$ Gbit/s to $10 \times 10$ Gbit/s OFDM signals could be successfully demultiplexed.

An Active Circulator-Based Delay Line

This paper presents a new active circulator-based delay line (DL) scheme to boost the delay time. The prototype achieves up to three times of the delay with a given DL. Linearity, noise, and maximum amplification times are analyzed in detail. This proof-of-concept is implemented in a 32-nm CMOS process and occupies 0.57 $\text {mm} \times 1.3$ mm chip area. It achieves phase noise of −107 dBc/Hz at 1-MHz offset and −12 dBm $P_{\mathrm {in,1\,dB}}$ with 915-MHz input. The power consumption is 64.8 mW.

A 50 Gb/s 190 mW Asymmetric 3-Tap FFE VCSEL Driver

This paper describes the design of an energy-efficient vertical-cavity surface-emitting laser (VCSEL) driver circuit implemented in a 130 nm SiGe BiCMOS technology. The driver features a 3-tap feed-forward equalizer where positive and negative peaks are added to the main signal to compensate for the low-pass characteristic of VCSELs. The circuit is also able to generate asymmetric pre-emphasis to counteract the VCSEL nonlinearity. Bonded to an 18 GHz VCSEL, the driver can reach an error-free (bit error rate < 10−12) optical data rate of 50 Gb/s with an horizontal eye opening better than 0.2 unit interval using a 22 GHz photoreceiver without equalization, retiming, and limiting amplifier at the receiver side. At 48 Gb/s, the horizontal eye opening is 0.5 unit interval. The circuit dissipates only 190 mW from a dual supply of 2.5 and 3.3 V, including the VCSEL power. To the best of the authors’ knowledge, this is the fastest common-cathode VCSEL driver with lowest power consumption for data rates higher than 35 Gb/s. Thanks to the active delay line and the application of vertical inductor, the driver is very compact with an active area of only 0.036 mm2 including the inductor.

Compact and Broadband Variable True-Time Delay Line with DLL-Based Delay-Time Control

This study presents the design and implementation of a compact and wideband active variable true-time delay line for timed array applications. Using a combination of coarse delay cells and fine delay cells, the proposed delay line achieves a large delay range and a high delay tuning resolution. Instead of LC delay lines or transmission lines, the delay can be approximated by compact active filters using transconductors and capacitors. The coarse delay cell adopts inductive peaking to broaden the bandwidth, and the fine delay cell employs a novel differential active inductor to improve the delay resolution and integration level. The group delays of the coarse delay cells and fine delay cells are analyzed and optimized. The signal transmission path is controlled by path-selection amplifiers and V---I conversion switches to achieve delay variability. The delay time is calibrated by the delay-locked loop (DLL) to mitigate the process, voltage and temperature variations. The complementary metal-oxide-semiconductor (CMOS) variable true-time delay line is fabricated in a 0.18-$$\upmu \hbox {m}$$μm CMOS process. Experiments indicate that the maximal relative delay is 95?ps and that the delay resolution is 5?ps within a 10% delay variation over a frequency range of 0.6---4.2?GHz. The chip dissipates 88?mW under a 1.8-V supply, and the core area including the DLL circuit is only 0.05?$$\hbox { mm}^{2}$$mm2.

Passive compression technique applied to UWB beamforming and imaging architectures

Recent works have demonstrated the feasibility of microwave imaging using compressive techniques, exempting the use of active delay lines, phase shifters, or moving parts to achieve beamforming. With this method, waves are coded in a passive way by a compressive device to reduce the complexity of the transmitter and/or receiver chains of the telecommunication and radar systems requiring beamsteering. Such a technique is based on the exploitation of the frequency diversity, implying that a reduction of the compressive device's volume imposes a diminution of the number of driven antennas. In this paper, the improvement brought by simultaneous excitations of the compressive device is presented. Adapting a new mathematical formulation, it is shown that M inputs can send independent waveforms allowing the beamsteering of an N-elements antenna array, while maintaining N &gt; M.

Analysis and Design of a Power-Scalable Continuous-Time FIR Equalizer for 10 Gb/s to 25 Gb/s Multi-Mode Fiber EDC in 28 nm LP CMOS

A continuous-time 7-tap FIR equalizer tailored to dispersion compensation in multi-mode fiber links is presented. By using a novel active delay line, the ultra-compact equalizer is very flexible, maintaining optimal performances and power scalability over a wide range of input data-rates. Particular care is taken to address critical issues of continuous-time realizations, such as noise, linearity and dynamic range. All-pass stages, realized with a simple circuit topology featuring high linearity and wide bandwidth, are investigated to implement the active delay line elements. Filter tap coefficients are realized with programmable transconductors and output currents are summed through a transimpedance amplifier, providing simultaneously high gain and wide bandwidth. Extensive experimental results, carried out on test chips realized in 28 nm LP CMOS technology, are presented. The equalizer demonstrates successful operation with variable data-rates ranging from 10 Gb/s to 25 Gb/s and power dissipation scalable from 55 mW to 90 mW. Compared to previously reported high-speed FIR equalizers, the proposed solution accepts the largest variation of the input data-rate with state-of-the-art power efficiency and core silicon area of only 0.085 mm 2 , meeting the demand of emerging 400 Gb/s standards.

Compact passive and active tunable delay lines using complementary split‐ring resonators

A novel compact left-handed delay line using four-cell of complementary split-ring resonators (CSRRs) has been designed, fabricated and characterised. It is found that the cell separation of CSRRs has significant effects on time delay. To obtain maximum time delay, each cell separation must be individually tuned and optimised. The results show that cell separation optimisation can prolong the delay time from 0.6 to 6.08 ns, increased by more than 90%. Furthermore, varactor diodes were embedded in the delay line to provide tunability. It is verified experimentally that the delay time can be tuned from 0.08 to 5.6 ns by varying DC bias from 0 to −20 V. In addition, a new equivalent circuit model has been developed and verified both numerically and experimentally, to take into account of the magnetic coupling between the rings in the adjacent cells, which has been neglected so far in published works. The proposed analysis reveals that such magnetic coupling can be sometimes very strong and has significant effects on circuit performance.

A DISTRIBUTED VARIABLE DELAY LINE FOR WIDEBAND BEAM-FORMERS

A fully integrated CMOS wideband distributed variable delay line for time array beam-formers is presented. The delay line works over a full difierential mode, and the delay cell function is based on difierential ampliflers with active inductive peaking loads. A delay resolution of 15ps is obtained with a maximum delay capability of 150ps. The designed active delay line provides 3 scanning angles with 8:6 - of spatial resolution. This delay line is applicable for a 4 channel beam-former with an operational bandwidth of 500MHz centered at 5GHz. Our active delay line consumes up to 352mW of power from a 2.5V supply. The circuit is simulated in standard 0.25m BiCMOS process and occupies 252m £ 123m of silicon area.

Application of combinations of axisymmetric modes in electrodynamic systems of high-power microwave devices

We consider some applications of combinations of axisymmetric magnetic waves of circular waveguides in microwave transmission lines, passive and active pulse compressors, delay lines, electron gyrodevices and other microwave components on the basis of analysis of the properties of such waves.

A Novel On-Chip Active Dispersive Delay Line (DDL) for Analog Signal Processing

In this letter, we report the first on-chip design of an active dispersive delay line (DDL) based upon the distributed amplification structure. This distributed amplifier DDL exhibits nanosecond delay variation in the frequency band from 11 to 15 GHz. An on-chip temporal imager is implemented with this active DDL and a linear chirp generator, realized by ramping the control voltage of a voltage controlled oscillator. The experimental data exhibits pulse stretching as well as pulse compression with this system.

Coherent control of stimulated emission inside one dimensional photonic crystals: strong coupling regime

The present paper discusses the stimulated emission, in strong coupling regime, of an atom embedded inside a one dimensional (1D) Photonic Band Gap (PBG) cavity which is pumped by two counter-propagating laser beams. Quantum electrodynamics is applied to model the atom-field interaction, by considering the atom as a two level system, the e.m. field as a superposition of normal modes, the coupling in dipole approximation, and the equations of motion in Wigner-Weisskopf and rotating wave approximations. In addition, the Quasi Normal Mode (QNM) approach for an open cavity is adopted, interpreting the local density of states (LDOS) as the local density of probability to excite one QNM of the cavity; and therefore rendering this LDOS dependent on the phase difference of the two laser beams. In this paper we demonstrate that the strong coupling regime occurs at high values of the LDOS. In accordance with the results of the literature, the emission probability of the atom decays with an oscillatory behaviour, so that the atomic emission spectrum exhibits two peaks (Rabi splitting). The novelty of this work is that the phase difference of the two laser beams can produce a coherent control of both the oscillations for the atomic emission probability and, as a consequence, of the Rabi splitting in the emission spectrum. Possible criteria to design active delay lines are finally discussed.

Erbium-Doped Fiber Amplifier Gain Characteristics Inside Active Delay Line Structures

A systematic study of how the erbium-doped fiber amplifier (EDFA) gain behaves inside an active recirculating delay line structure is presented. It is verified using a representation of an active-fiber Bragg-grating-pair filter. It shows that due to the presence of the recirculating signal, the EDFA gain inside the cavity exhibits hard saturation, and with a proper design, fluctuations in pump power have only slight effects on EDFA gain and this enables the active delay line filter to realize a stable high-Q frequency response. Results demonstrate a high-Q photonic signal processing filter that exhibits low sensitivity to pump power perturbations and which shows robust active filter operation.

An Active Semiconductor Tunable-Shape Optical Filter and Delay Line

We present a novel active semiconductor optical filter consisting of a curved-waveguide distributed-feedback (DFB) section and a phase-shifter section with a highly reflective coating. Separate electrical contacts to the DFB and phase-shifter sections allow independent tuning of the gain and the phase accumulated through the structure. The waveguide curvature forms an additional cavity, leading to interesting and controllable coupled-cavity effects. We show experimental and theoretical transmission properties of this filter operating with fixed gain in the DFB and current-controlled absorption in the phase-shifter and suggest potential applications to active filter control and tunable optical delay lines.

Gigahertz waveform sampling and digitization circuit design and implementation

A series of multichannel transient waveform digitization integrated circuits with up to 5 GHz sample rates and parallel 10-bit digitization have been designed, tested, and fabricated in large quantities. The current CMOS circuit uses four arrays of 128 fast switched capacitors per channel to record four parallel analog transient inputs. High-speed sample clock generation is provided by an analogically adjustable asynchronous active delay line that uses look-ahead to generate 128 multi-GHz four-way interleaved clocks without the need for external high-speed clocking. After transient capture, each channel is fed into 128 parallel 10-bit analog to digital converters for fast, channel-parallel digitization, followed by digital readout. The fast triggering and waveform capture, channel-parallel digitization and convenient word-parallel digital readout results in a responsive and low dead-time system. Acquisition sample rates range from /spl sim/50 kHz to /spl sim/3 GHz. Analog input bandwidth was measured to be /spl sim/350 MHz. Temporal noise is typically equivalent to /spl sim/1 mV root mean square (rms) for a signal-to-noise ratio of /spl sim/2500:1 rms. Fixed-pattern spatial noise, after on-chip digitization, is equivalent to /spl sim/5 mV rms. Current design directions are intended improve on this technology with sample rates in excess of 10 GHz and an analog bandwidth exceeding 1 GHz.

Active magnetostatic wave delay line for microwave signals

Summary form only given. Three variants of a new active magnetostatic wave (MSW) delay line for pulsed microwave signals providing controlled delay times of up to 1 /spl mu/s has been developed and experimentally tested. The proposed active delay line consists of an input and output transducers, yttrium-iron garnet (YIG) film waveguide (where the microwave MSW pulse is propagating), and an open dielectric resonator which is situated between the transducers and is used to supply electromagnetic pumping pulses having frequency (9.4 GHz) twice as large as the carrier frequency of the input microwave radio-pulse (4.7 GHz). In contrast with the usual passive MSW delay line, where characteristics are controlled by the external bias magnetic field, the characteristics of the developed active delay line are controlled by the amplitude, duration, and the moment of application of the pumping pulse. While traditional passive MSW delay lines have substantial insertion losses proportional to the delay time (/spl sim/ 80 dB//spl mu/s), in the developed active delay line the amplitude of the output delayed pulse can be kept constant in the whole interval of possible time delays.

Reversal of momentum relaxation.

A new phenomenon of momentum relaxation reversal has been discovered experimentally and explained theoretically for dipolar spin waves in magnetic garnet films. It is shown that the process of momentum relaxation, caused by the scattering of a signal wave on defects, can be reversed, and the signal can be restituted after it left the scattering region. The reversal of momentum relaxation is achieved by frequency-selective parametric amplification of a narrow band of scattered waves having low group velocities and frequencies close to the frequency of the original signal wave. The phenomenon can be used for the development of a new type of active microwave delay lines.

The Palomar Testbed Interferometer

The Palomar Testbed Interferometer (PTI) is a long-baseline infrared interferometer located at Palomar Observatory, California. It was built as a testbed for interferometric techniques applicable to the Keck Interferometer. First fringes were obtained in 1995 July. PTI implements a dual-star architecture, tracking two stars simultaneously for phase referencing and narrow-angle astrometry. The three fixed 40 cm apertures can be combined pairwise to provide baselines to 110 m. The interferometer actively tracks the white-light fringe using an array detector at 2.2 microns and active delay lines with a range of +/-38 m. Laser metrology of the delay lines allows for servo control, and laser metrology of the complete optical path enables narrow-angle astrometric measurements. The instrument is highly automated, using a multiprocessing computer system for instrument control and sequencing.

Active magnetostatic wave delay line

Two configurations for an active microwave delay line with feedback to improve the loss per unit delay time have been made and characterized. The lines utilized thin yttrium iron garnet (YIG) film, magnetostatic wave (MSW) passive elements, a microwave amplifier, and a variable attenuator connected in a feedback loop. The two delay line setups used a surface wave (MSSW) configuration with a single MG element and a nondispersive configuration with MSSW and backward volume wave (MSBVW) delay lines in series. For each setup, a sequence of delayed pulses at the output is observed when a single microwave pulse is fed to the input. The one-pass delay time T of the pulse through the MSW delay line and the number n of circulations in the feedback loop defines the total delay time nT for the nth pulse. The feedback resulted in a reduction in the output pulse decay rate and longer useful delay times. For a passive delay line with no feedback, typical values of the loss p.u. delay time L and useful delay time (nT)/sub U/ were -110 dB//spl mu/s and 0.1-0.2 /spl mu/s, respectively. With feedback for the MSSW delay line, a 4.5-GHz operating frequency, and 40 ns input pulses, L and (nT)/sub U/ were -19 dB//spl mu/s and 0.6 /spl mu/s, respectively. Feedback with the nondispersive delay line gave L and (nT)/sub U/ values of -12 dB//spl mu/s and 3 /spl mu/S, respectively, for 4.5-GHz, 40-ns input pulses.