Switched-current signal processing for video frequencies and beyond

Switched-current (SI) signal processing circuits with video frequency performance are presented. The delay cells employ negative feedback to produce a `virtual earth' at the input node to improve transmission accuracy. Fully differential structures with common-mode feedback are used to reduce charge injection errors and crosstalk from digital signals. An IC test circuit, in a 1 μm standard digital CMOS process, containing simple delay lines and an FIR filter section is described, and measured performance is given. Typically, a 2T delay line sampling at 13.3 MHz gave a low-frequency gain error of -54 dB, a settling error of -60 dB, a third-harmonic distortion of -40 dB with 75% modulation, and an S/N ratio of 60 dB. Scaling of the memory cell device dimensions and currents should permit SI operation at clock frequencies beyond 100 MHz     

Microwave photonic bandpass filter based on spectrumslicing and phase modulator

A tunable microwave photonic bandpass filter with high mainlobe-to-sidelobe ratio (MSR) based on a phase modulator and a dispersive device is proposed. The multi-tap characteristics of the filter are realized by slicing a broadband source using a Mach-Zehnder interferometer (MZI) which results in a high MSR of 25 dB. The tunability of the filter is realized by an optical variable delay line (OVDL) in one arm of the MZI, which changes the wavelength spacing of the sliced broadband source and results in a tunable free spectrum range (FSR) of the filter. The central frequency of the bandpass filter is tunable from 10.7 GHz to 27 GHz by changing the wavelength spacing from 0.145 nm to 0.054 nm.     

Wavelength blocking filter with flexible data rates and channel spacing

This work presents a high-resolution (13.2 GHz) channel-blocking optical filter, suitable for use as a reconfigurable optical add/drop multiplexer (ROADM), which seamlessly supports data rates from 2.5 to 160 Gb/s. The filter consists of a linear array of 64 MEMS micromirrors and a high-dispersion echelle grating. The demonstrated device had an insertion loss of 9 dB, a loss ripple of 1.2 dB, and a group delay ripple of 15 ps. Data transmission through the device with various mixed data rate scenarios ranging from 2.5 to 160 Gb/s showed negligible penalty, except at 40 Gb/s where a maximum penalty of 1.5 dB was observed due to a phase coherence with the blocker filter ripple.     

Wide-band superconducting microstrip delay line

This paper describes the design, fabrication, and testing of a novel microstrip superconducting delay line. The structure of the delay line is a double-spiral meander line. The device is patterned from a YBa/sub 2/Cu/sub 3/O/sub 7-/spl delta//(YBCO) thin film deposited on both sides of a 2-in-diameter LaAlO/sub 3/ substrate with a thickness of 0.25 mm. It exhibits low insertion loss up to 20 GHz. At 10 GHz, the measured attenuation is 0.031 dB/ns at 30 K, 0.049 dB/ns at 60 K, and 0.118 dB/ns at 77 K. The magnitudes of the ripples are below 2 dB across the entire band. The total delay at low frequency is approximately 29 ns.     

A Novel 3–5 GHz Active Matched Filter for Impulse Radio Ultra-Wideband

In this letter, a novel active matched filter for UWB-IR lower band (3.1–4.85 GHz) is presented. The signal to noise ratio is improved at the output using a tapped delay line with a common source amplifier. An artificial transmission line is used for wideband impedance matching. The matched filter achieves a power gain of 9.8 dB at center frequency. Input matching is better than ${-}19$ dB and output matching is better than ${-}15$ dB. The averaged SNR improvement is 4.6 dB using peak detection. Input referred 1-dB compression point is 0.7 dBm at the center frequency. The matched filter is biased from a 1.5 V supply with a total power consumption of 38 mW.      

Coherence-Free Microwave Photonic Bandpass Filter Using a Frequency-Shifting Recirculating Delay Line

A new microwave photonic filter that realizes a high-resolution bandpass filter response with coherence-free operation and without the limitations of phase-induced intensity noise is presented in this paper. It is based on a frequency-shifting recirculating delay line, which can simultaneously achieve a multitap, high-resolution filter and a very large suppression of noise, while also enabling the use of a conventional narrow-linewidth laser source without suffering from coherent interference effects. Experimental results demonstrate a filter $Q$ value of 200 and an SNR improvement of 40.3 dB compared to conventional recirculating delay line structures.      

RF Front-End Passive Circuit Implementation Including Antenna for ZigBee Applications

This paper presents a front-end passive circuit module for ZigBee applications using low-temperature co-fired ceramic technology. The front-end part consists of an antenna, a bandpass filter, a switch, and two baluns. In antenna design, the solenoid shape is employed for reducing the size of the antenna, resulting in an overall size of 9times16.4times1.82 mm³ and a gain of -1.4 dBi. As for the filter, two types of filters are suggested. First, the lumped-type filter employing a high-Q spiral inductor has more than 20-dB attenuation at both stopbands, very near to the passband. Secondly, the semilumped-type filter adopting an edge coupled line and a loading capacitor provides a group delay of below 5 ns and is adequate for the full module structure due to the structure flexibility. A balun is evaluated using lumped components instead of a transmission line and, thus, it provides an insertion loss of only 0.3 dB and a phase difference of 180deg between balanced signals. Based on these components, an RF front-end module including attaching pads for an RF integrated circuit (IC) and baseband IC is implemented. In case of using the lumped-type filter, the insertion loss of the front-end module is 6.5 dB, and the group delay is below 7 ns. In case of adopting the semilumped-type filter, the insertion loss is 6.2 dB, and the group delay is below 4 ns. The overall size of the former and latter is 25.14times28.5times0.68 mm³ and 25.66times25.58times1.17 mm³, respectively     

L波段单片SAW宽带信号形成器

L波段宽带信号形成器是现代超宽带雷达、电子对抗等系统的关键基础器件.采用声表面波(SAW)色散延迟线技术是实现超宽带信号形成器的重要技术途径.该文介绍了一种中心频率为1.55 GHz,带宽≥420 MHz;时延≥0.84 μs的L波段单片SAW宽带信号形成器. 通过对SAW线性调频延迟线换能器拓扑结构优化、阻带抑制和宽带匹配,使得宽带SAWDDL器件的插入损耗低达-38 dB ,阻带抑制高达50 dB(到3 GHz),时域直通隔离度大于90 dB,单端驻波小于2.     

A merged pipe organ binary-analog correlator

The design of a 96-stage, programmable binary-analog correlator is described. An array of charge coupled device (CCD) delay lines of differing lengths perform the delay and sum function. Merging of several CCD channels is employed to reduce the active area. This device architecture allows simplified output detection while maintaining good device performance at high speeds (5-10 MHz). Experimental results indicate a 50 dB broad-band dynamic range and excellent agreement with the theoretical processing gain (19.8 db) when operated at a 6 MHz sampling frequency as a sequence matched filter pseudorandom noise.     

Low-loss athermal silica-based lattice-form interleave filter with silicone-filled grooves

We describe a low-loss athermal silica-based interleave filter with a lattice-form structure. We athermalize the filter by using a silicone-filled groove formed in each delay line and we employ a low-loss design to reduce the accumulated groove excess loss in the multiple delay lines. By using these designs, we obtained a very low groove excess loss of 0.4 dB and achieved satisfactory temperature insensitivity and optical characteristics with this filter.     

A reprogrammable filter bank using charge-coupled device discrete analog-signal processing

A filter bank having up to 32 channels is formed by multiplexing a recursive two-pole delay line filter. Thirty-two sets of filter constants are stored and addressed digitally while multiple delays are provided in analog form by a charge-coupled device (CCD) delay line. The interface between the digitally stored constant and the delayed analog signal occurs in a four quadrant multiplying D/A where the delayed analog signal is weighted by the constant. Sampling and clamping at the CCD interfaces insures accurate bipolar analog operation. The filter hardware is described, the filter constants are derived, and the performance is documented.     

一种新型大带宽高通带平坦度延迟线的设计技术

采用倾斜换能器结构,通过优化设计,研制出中心频率800MHz,带宽200MHz,延迟时间为100ns～3μs且精确可控的声表面波延迟线。该系列产品的插入损耗约为-25dB,直通抑制大于35dB,三次渡越抑制大于50dB,200MHz通带内波纹小于1dB,产品综合性能指标优异。     

A reprogrammable filter bank using charge-coupled device discrete analog-signal processing

A filter bank having up to 32 channels is formed by multiplexing a recursive two-pole delay line filter. Thirty-two sets of filter constants are stored and addressed digitally while multiple delays are provided in analog form by a charge-coupled device (CCD) delay line. The interface between the digitally stored constant and the delayed analog signal occurs in a four quadrant multiplying D/A where the delayed analog signal is weighted by the constant. Sampling and clamping at the CCD interfaces insures accurate dipolar analog operation. The filter hardware is described, the filter constants are derived, and the performance is documented.     

An ultra-low-power, low-voltage electronic audio delay line for usein hearing aids

In this paper, the design of an electronic audio delay line, realized with a second-order all-pass filter, is presented. The designed filter is primarily intended for use in hearing aids, to provide directivity by a specially designed microphone array. The filter operates at a supply voltage of as low as 1.8 V. The simulated and measured total quiescent current is 0.9 μA. Owing to current companding and class-AB operation, the dynamic range is 62 dB at a total harmonic distortion (THD) below 7%, i.e., at maximum output. The delay time is adjustable by control currents. The filter has been integrated in a standard bipolar process. The total measured delay time of the all-pass filter is approximately 110 μs over a bandwidth of 4 kHz     

Compact Wide-Band Bandpass Filter Using Microstrip to Slotline Broadside-Coupling

In this letter, two quarter wavelength microstrip stubs with a shorted slot line resonator etched in the ground plane is used to design a compact wideband bandpass filter (BPF). Wideband characteristics are obtained using broadside-coupling between the stubs and the slot line. 3-dB fractional bandwidth (FBW) is varied by changing coupled line widths. The filter has the advantages of compactness, wide bandwidth, low passband insertion loss (IL), low group delay variation and ease of fabrication. One prototype fabricated filter has a FBW of 60.0% with a maximum passband IL of 0.9 dB and group delay variation of 0.40 nS. BPF occupying area is less than 0.19lambdagtimes0.20lambdag, where lambdag is the guided wavelength at midband frequency 2.5 GHz. Good agreement between measurements and simulations are obtained.     

Tunable Matched Filters for Pulse-Code Modulation Using Charge-Transfer Devices

A tunable matched filter for the major PCM codes has been synthesized utilizing a developmental bucket-brigade delay (BBD) line. The variable delay feature of the BBD allows continuous tuning of the matched filter over a wide range of bit rates. By combining and weighting the outputs of two BBD lines, matched filters for nonreturn-to-zero (NRZ), return-to-zero (RZ), and biphase codes are realized with a signal-to-noise performance within 0.8 dB of theoretical.     

All-fibre multichannel flattop filter based on coherent fibre delayline structure

A technique for implementing an all-fibre multichannel flattop filter based on an optically coherent fibre delay line structure is demonstrated. Using a cascaded high birefringence fibre structure, negative tap weighting is realised in the transversal filter with suppression of optical interference noise. Flattened passbands ~0.35 nm and 0.87 nm with ripples <0.15 dB are obtained     

Tunable microwave photonic filter for noise and interference suppression in UMTS base stations

A design of a tunable microwave photonic filter for noise suppression and channel interference mitigation in the front-end stage after the receiving antenna of an UMTS base station is presented. The filter provides a tunable and very high selective performance (5 MHz along the 1935-1977 MHz band) with 14 dB suppression in the stopband using 30 fibre Bragg gratings and a reconfigurable dispersive delay line.     

SAW dispersive delay line utilising apodised IDT with periodic electrodes

In designing SAW dispersive delay lines (DDLs), one usually applies dispersive interdigital transducers with electrode spacing varying according to the frequency-delay time relation of the delay line impulse response. A new method is proposed in the letter, in which a DDL is treated as a bandpass filter with a nonlinear phase response. Such a filter can be synthesised with an IDT having periodic electrodes with apodisation. The experimental result is ?40 dB of sidelobe level obtained in a system of two DDLs, one of which is Hamming-weighted.     

采用SAW和PLL技术的扩频通信信道模块

通过采用锁相环(PLL)技术实现了射频载波的跳频扩频(FHSS)，跳变载波相噪小于-98dBc／Hz@1kHz，杂散抑制大于70dB，收发端隔离度大于105dB；声表面波(sAw)匹配滤波器保证了20Mbps的直接序列扩频(DSSS)信号的实时解扩，SAW固定延迟线实现了延迟差分解调与解码。导出采用2阶有源比例积分器作为PLL频率合成器的低通滤波器的中相位边界与环路衰减系数之间的数学关系式。