Fiber-optic multigigabit GaAs MIC front-end circuit with inductorpeaking

The design and performance of a multigigabit optical front-end circuit are discussed. Inductor peaking is applied to the GaAs MIC preamplifiers and a 3-dB down bandwidth of 6.5 GHz, 15.5-pA/√Hz averaged input equivalent noise current density from 10 MHz to 6.5 GHz, and transimpedance gain of 57 dB are achieved. A 3-dB down bandwidth of 6.1 GHz is achieved in an optical front-end circuit with a InGaAs p-i-n photodiode. This performance indicates that the optical front-end circuit with inductor peaking is promising for multigigabit optical receivers     

Highly efficient 40-GHz bandwidth Ti:LiNbO3 opticalmodulator employing ridge structure

The design and fabrication of a Ti:LiNbO₃ optical modulator employing a ridge structure with a shielding plane are described. The ridge structure offers a relatively low microwave propagation loss and large interaction between the microwave and optical wave under the condition of a 50 Ω characteristic impedance system, resulting in a large modulation bandwidth and low driving voltage. As a result, a 3-dB optical bandwidth of 40 GHz with a driving voltage of 3.6 V is achieved at 1.5 μm     

A broadband Ti:LiNbO3 optical modulator with a ridgestructure

We describe the design, fabrication, and characteristics of a Ti:LiNbO₃ optical modulator with a ridge structure. The structure keeps microwave propagation loss low and enables a large interaction between microwaves and optical waves under the conditions of velocity-matching and impedance matching, resulting in a large modulation bandwidth and low driving voltage. Using this structure, we have developed an optical intensity modulator with an optical 3-dB bandwidth of 75 GHz and a driving voltage of 5.0 V at a wavelength of 1.5 μm     

GaAs traveling-wave optical modulator using a modulated coplanar strip electrode with periodic cross-tie overlay

This paper proposes and analyzes a GaAs traveling-wave optical modulator which uses a modulated coplanar strip electrode with periodic cross-tie overlay. This slow-wave structure can be designed to satisfy phase velocity and impedance matching conditions simultaneously. The dominant conductor loss in the slow-wave structure is reduced using the modulated coplanar strip electrode. The calculated 3-dB modulation bandwidth (100 GHz) is much wider than the bandwidth limit (30 GHz) of conventional electrode structures that are limited by phase velocity mismatch.     

Bipolar monolithic amplifiers for a gigabit optical repeater

Main amplifier, AGC amplifier, and preamplifier ICs have been designed and fabricated using an advanced silicon bipolar process to provide the required characteristics of repeater circuits for a gigabit optical fiber transmission system. The bipolar technology used involved a separation width of 0.3 /spl mu/m between the emitter and the base electrode. New circuit techniques were also used. The differential type main amplifier has a peaking function which can be varied widely by means of DC voltage supplied at the outside IC terminal. A bandwidth which can be varied to about three times the value for a nonpeaking amplifier is easily obtained. The gain and maximum 3-dB down bandwidth were 4 dB and 4 GHz, respectively. The main feature of the AGC amplifier is that the diodes are connected to the emitters of the differential transistor pair to improve the linearity. The maximum gain and 3-dB down bandwidth were 15 dB and 1.4 GHz, respectively, and a dynamic range of 25 dB was obtained. The preamplifier has a shunt-series feedback configuration. Furthermore, a gain and 3-dB down bandwidth of 22 dB and 2 GHz, respectively, were achieved with an optimum circuit design. The noise figure obtained was 3.5 dB.     

Broad-band GaAs monolithic equalizing amplifiers formultigigabit-per-second optical receivers

The authors discuss the development of ICs (integrated circuits) for a preamplifier, a gain-controllable amplifier, and main amplifiers with and without a three-way divider for multigigabit-per-second optical receivers using a single-ended parallel feedback circuit, two (inductor and capacitor) peaking techniques, and advanced GaAs process technology. An optical front-end circuit consisting of a GaAs preamplifier and an InGaAs p-i-n photodiode achieves a 3-dB bandwidth of 7 GHz and -12-dBm sensitivity at 10 Gb/s. Moreover, a gain-controllable amplifier obtains a maximum gain of 15 dB, a gain dynamic range of 25 dB, and a 3-dB bandwidth of 6.1 GHz by controlling the source bias of the common-source circuit. Gain, 3-dB bandwidth, and output power of the main amplifier with the three-way divider are 17.4 dB, 5.2 GHz, and 5 dBm, respectively. These ICs can be applied to optical receivers transmitting NRZ signals in excess of 7 Gb/s     

Fabrication and Characteristics of 40-Gb/s Traveling-Wave Electroabsorption Modulator-Integrated DFB Laser Modules

We have developed 40-Gb/s traveling-wave electroabsorption-modulator-integrated distributed feedback laser (TW-EML) modules using several advanced technologies. First, we have adopted a selective area growth (SAG) method in the fabrication of the 40-Gb/s EML device to provide active layers for the laser and the electroabsorption modulators (EAMs) simultaneously. The fabricated device shows that the measured 3-dB bandwidth of electrical-to-optical (E/O) response reaches about 45 GHz and the return loss (S₁₁) is kept below -10 dB up to 50 GHz. For the module design of the device, we mainly considered electrical and optical factors. The measured S₁₁ of the fabricated 40 Gb/s TW-EML module is below -10 dB up to about 30 GHz and the 3-dB bandwidth of the E/O response reaches over 35 GHz. We also have developed two types of coplanar waveguide (CPW) for the application of the driver amplifier integrated 40 Gb/s TW-EML module, which is a system-on-package (SoP) composed of an EML device and a driver amplifier device in a module. The measured S₁₁ of the two-step-bent CPW is below -10 dB up to 35 GHz and the measured S₁₁ of the parallel type CPW is below -10 dB up to 39 GHz.     

Field Theory Design of Rectangular Waveguide Multiple-Slot Narrow-Wall Couplers

A compact narrow-wall multiple-slot coupler suitable for inexpensive and very accurate metal-etching manufacturing techniques is proposed and optimized. A computer-aided design theory based on the method of field expansion of eigenmodes considers the effects of finite insert thickness and higher order mode interaction, step discontinuities, and changes in width. Computer-optimized design data for --20-, --8.34-, and --3-dB couplers in the R140-waveguide band (12.4--18 GHz) are given. These data are transferable into other common waveguide bands, e.g., R620 band (50-75 GHz), by suitable frequency scaling calculations. A metal-etched 12-slot coupler prototype for a midband frequency of about 15 GHz achieves a +-1-dB bandwidth of the --3-dB coupling of about 3.2 GHz together with a measured isolation of typically 35-40 dB (minimum 25 dB at the band limits). The measurements show good agreement with theory.     

A Ka-band power amplifier based on the traveling-wave power-dividing/combining slotted-waveguide circuit

An eight-device Ka-band solid-state power amplifier has been designed and fabricated using a traveling-wave power-dividing/combining technique. The low-profile slotted-waveguide structure employed in this design provides not only a high power-combining efficiency over a wide bandwidth, but also efficient heat sinking for the active devices. The measured maximum small-signal gain of the eight-device power amplifier is 19.4 dB at 34 GHz with a 3-dB bandwidth of 3.2 GHz (f/sub L/=31.8 GHz, f/sub H/=35 GHz). The measured maximum output power at 1-dB compression (P/sub out/ at 1 dB) from the power amplifier is 33 dBm (/spl sim/2 W) at 32.2 GHz, with a power-combining efficiency of 80%. Furthermore, performance degradation of this power amplifier due to device failures has also been simulated and measured.     

High-speed characteristics of low-optical loss oxide-apertured vertical-cavity lasers

We characterize the high-speed modulation properties of thin-oxide-apertured vertical-cavity lasers. The modulation response scales with device diameter due to the negligible optical scattering loss present in these devices. A small diameter laser of 3.1 /spl mu/m has a maximum 3-dB bandwidth of 15.2 GHz at a bias of only 2.1 mA. Modeling indicates a no-parasitic bandwidth of 18.2 GHz at this current level, with an intrinsic 3-dB bandwidth limit of 45 GHz due to gain compression. The present devices are limited by parasitic capacitance across the thin oxide layer.     

Optical down-sampling of wide-band microwave signals

Phase-encoded optical sampling allows radio-frequency and microwave signals to be directly down-converted and digitized with high linearity and greater than 60-dB (10-effective-bit) signal-to-noise ratio. Wide-band electrical signals can be processed using relatively low optical sampling rates provided that the instantaneous signal bandwidth is less than the Nyquist sampling bandwidth. We demonstrate the capabilities of this technique by using a 60-MS/s system to down-sample two different FM chirp signals: 1) a baseband (0-250 MHz) linear-chirp waveform and 2) a nonlinear-chirp waveform having a 10-GHz center frequency and a frequency excursion of 1 GHz. We characterize the frequency response of the technique and quantify the analog bandwidth limitation due to the optical pulse width. The 3-dB bandwidth imposed by a 30-ps sampling pulse is shown to be 10.4 GHz. We also investigate the impact of the pulse width on the linearity of the phase-encoded optical sampling technique when it is used to sample high-frequency signals.     

A 60-GHz Millimeter-Wave Bandpass Filter Using 0.18-μm CMOS Technology

This letter presents the design and implementation of a 60-GHz millimeter-wave RF-integrated-circuit-on-chip bandpass filter using a 0.18-mum standard CMOS process. A planar ring resonator structure with dual-transmission zeros was adopted in the design of this CMOS filter. The die size of the chip is 1.148times1.49 mm². The investigations of sensitivity to the insertion loss and the passband bandwidth for different perturbation stub sizes are also studied. The filter has a 3-dB bandwidth of about 12 GHz at the center frequency of 64 GHz. The measured insertion loss of the passband is about 4.9 dB, and the return loss is better than 10 dB within the passband.     

110-GHz, 50%-efficiency mushroom-mesa waveguide p-i-n photodiodefor a 1.55-μm wavelength

A mushroom-mesa structure is proposed to reduce the CR-time constant which originates from the waveguide photodiode structure. Experimental results at a 1.55-μm wavelength show that the multimode waveguide p-i-n photodiode with mushroom-mesa structure has an electrical 3-dB bandwidth of more than 75 GHz in the frequency domain and an electrical 3-dB bandwidth of 110 GHz in the time domain. The external quantum efficiency is 50% or 0.63 A/W, which leads to a record bandwidth-efficiency product of 55 GHz for long wavelength p-i-n photodetectors     

Ultra-Broad-Band GaAs Monolithic Amplifier

GaAs monolithic IC design and fabrication techniques suitable for baseband pulse amplification have been developed. The developed GaAs monolithic amplifier has a two-stage construction using two source-grounded FET's. To reduce input VSWR without serious noise-figure degradation, an inter-gate-drain negative feedback circuit was adopted. An interstage circuit is a dc-coupled circuit consisting of an appropriate impedance transmission line. Gate voltage for the second-stage FET is self-biased. The amplifier has 13.5-dB gain over the 3-dB bandwidth from below 500 MHz to 2.8 GHz. Less than 6-dB (7-dB) noise figure was obtained from 700 MHz to 2.2 GHz (150 MHz to 3 GHz). Input VSWR is less than 1.5     

Ultra-broad-band GaAs monolithic amplifier

GaAs monolithic IC design and fabrication techniques suitable for baseband pulse amplification have been developed. The developed GaAs monolithic amplifier has a two-stage construction using two source-grounded FET's. To reduce input VSWR without serious noise-figure degradation, an inter-gate-drain negative feedback circuit was adopted. An interstage circuit is a dc-coupled circuit consisting of an appropriate impedance transmission line. Gate voltage for the second-stage FET is self-biased. The amplifier has 13.5-dB gain over the 3-dB bandwidth from below 500 kHz to 2.8 GHz. Less than 6-dB (7-dB) noise figure was obtained from 700 MHz to 2.2 GHz (150 MHz to 3 GHz). Input VSWR is less than 1.5     

InP-based 10-GHz bandwidth polarization diversity heterodynephotoreceiver with electrooptical adjustability

A polarization diversity optical receiver, integrated with two pairs of balanced photodiodes in the InP/InGaAsP material system, is described. This circuit includes two polarization splitters based on modal birefringence and, for the first time, adjustable 3-dB TE and TM directional couplers (relaxing fabrication tolerances). On-chip losses are below 2.5 dB (TE) and 5.5 dB (TM). Waveguide to PIN coupling efficiency is >95%. Polarization crosstalk is in the 9-10-dB range, 3-dB couplers balance can be recovered, and common mode rejection ratio (CMRR) lower than -30 dB is obtained and remains below -20 dB over 6 GHz. Balanced receiver circuit 3-dB bandwidth is in excess of 10 GHz     

Low-loss LTCC cavity filters using system-on-package technology at 60 GHz

In this paper, three-dimensional (3-D) integrated cavity resonators and filters consisting of via walls are demonstrated as a system-on-package compact solution for RF front-end modules at 60 GHz using low-temperature cofired ceramic (LTCC) technology. Slot excitation with a /spl lambda/g/4 open stub has been applied and evaluated in terms of experimental performance and fabrication accuracy and simplicity. The strongly coupled cavity resonator provides an insertion loss <0.84 dB, a return loss >20.6 dB over the passband (/spl sim/0.89 GHz), and a 3-dB bandwidth of approximately 1.5% (/spl sim/0.89 GHz), as well as a simple fabrication of the feeding structure (since it does not require to drill vias to implement the feeding structure). The design has been utilized to develop a 3-D low-loss three-pole bandpass filter for 60-GHz wireless local area network narrow-band (/spl sim/1 GHz) applications. This is the first demonstration entirely authenticated by measurement data for 60-GHz 3-D LTCC cavity filters. This filter exhibits an insertion loss of 2.14 dB at the center frequency of 58.7 GHz, a rejection >16.4 dB over the passband, and a 3-dB bandwidth approximately 1.38% (/spl sim/0.9 GHz).     

Design of Low-Profile Millimeter-Wave Substrate Integrated Waveguide Power Divider/Combiner

A low-profile millimeter-wave substrate integrated waveguide (SIW) power divider/combiner is presented in this paper. The simplified model of this compact SIW power dividing/combining structure has been developed. Analysis based on equivalent circuits gives the design formula for perfect power dividing/combining. In order to verify the validity of the design method, a four-way SIW power divider/combiner circuit operating at Ka band is designed, fabricated and measured. Good agreement between simulated and measured results is found for the proposed passive power divider/combiner. Experiments on the four-way passive divider/combiner back-to-back design demonstrate a minimum overall insertion loss of 1.5 dB at 31.1 GHz, corresponding to a power-combining efficiency of 84%. The measured 10-dB return loss bandwidth is demonstrated to be 2.2 GHz, and its 0.5-dB bandwidth was 2 GHz.     

Coherent receiver front-end module including a polarizationdiversity waveguide OIC and a high-speed InGaAs twin-dual p-i-nphotodiode OEIC both based on InP

The economic implementation of coherent optical systems requires practical integrated optical front-end receiver devices with reasonable degree of integration. As a precursor to such an OEIC, an InGaAsP/InP polarization diversity waveguide OIC, including two TE/TM-mode splitters, two TE-filters, two 3-dB couplers, and a planar front-illuminated InGaAs twin-dual-p-i-n photodiode-OEIC (including two balanced p-i-n photodiodes) was fabricated. The OIC depicts a TE/TM-mode separation of more than 13 dB, a 3-dB coupler imbalance of less than 10% and an intrinsic loss of less than 2 dB. A single detector device shows a responsivity of 1.05 A/W at a wavelength of 1.55 μm, a total series resistance below 10 Ω, and a 3-dB bandwidth of more than 10 GHz. The O(E)ICs have been (packaged) in a versatile housing for system tests. The operation of the modules has been demonstrated in a heterodyne experiment yielding a bandwidth of more than 2.2 GHz for the whole module     

An over-110-GHz InP HEMT flip-chip distributed baseband amplifier with inverted microstrip line structure for optical transmission system

We successfully developed state-of-the-art InP high electron mobility transistor (HEMT) distributed amplifiers by using inverted microstrip line (IMSL) technology. The IMSL has minor frequency dispersion characteristics and a simple equivalent circuit model can embody its discontinuity, such as a T-junction, because it has a large ground plane at the surface of the chip. For one distributed amplifier, we achieved a gain of 14.5 dB and a 94-GHz 3-dB bandwidth resulting in a gain-bandwidth product of 500 GHz, and for the other we achieved a gain of 7.5 dB and a 3-dB bandwidth of over 110 GHz. Furthermore, this technology also offers the capability of fabricating ultra-broad-band packaged ICs with flip-chip assembly for operation up to the W-band. In this paper, we focus on the advantage of IMSL technology for circuit design. We used an IMSL structure to design and fabricate a distributed amplifier to verify the advantages of IMSL. Our results show that this is an accurate technique for designing broad-band circuits up to 110 GHz.