A V-band front-end with 3-D integrated cavity filters/duplexers and antenna in LTCC technologies

This paper presents a compact system-on-package-based front-end solution for 60-GHz-band wireless communication/sensor applications that consists of fully integrated three-dimensional (3-D) cavity filters/duplexers and antenna. The presented concept is applied to the design, fabrication, and testing of V-band (receiver (Rx): 59-61.5 GHz, transmitter (Tx): 61.5-64 GHz) transceiver front-end module using multilayer low-temperature co-fired ceramic technology. Vertically stacked 3-D low-loss cavity bandpass filters are developed for Rx and Tx channels to realize a fully integrated compact duplexer. Each filter exhibits excellent performance (Rx: IL<2.37 dB, 3-dB bandwidth (BW) /spl sim/3.5%, Tx: IL<2.39 dB, 3-dB BW /spl sim/3.33%). The fabrication tolerances contributing to the resonant frequency experimental downshift were investigated and taken into account in the simulations of the rest devices. The developed cavity filters are utilized to realize the compact duplexers by using microstrip T-junctions. This integrated duplexer shows Rx/Tx BW of 4.20% and 2.66% and insertion loss of 2.22 and 2.48 dB, respectively. The different experimental results of the duplexer compared to the individual filters above are attributed to the fabrication tolerance, especially on microstrip T-junctions. The measured channel-to-channel isolation is better than 35.2 dB across the Rx band (56-58.4 GHz) and better than 38.4 dB across the Tx band (59.3-60.9 GHz). The reported fully integrated Rx and Tx filters and the dual-polarized cross-shaped patch antenna functions demonstrate a novel 3-D deployment of embedded components equipped with an air cavity on the top. The excellent overall performance of the full integrated module is verified through the 10-dB BW of 2.4 GHz (/spl sim/4.18%) at 57.45 and 2.3 GHz (/spl sim/3.84%) at 59.85 GHz and the measured isolation better than 49 dB across the Rx band and better than 51.9 dB across the Tx band.     

60-GHz-band coplanar MMIC active filters

This paper presents the design and performance of 60-GHz-band coplanar monolithic microwave integrated circuit (MMIC) active filters. To compensate for the loss of the passive filter, a resonator composed of a quarter-wavelength line is terminated by a circuit with a constant negative resistance over a wide frequency band. Cross-coupling is introduced to make the attenuation poles on both sides of the passband. We develop two types of two-stage filter: one with medium bandwidth and the other with narrow bandwidth. The former shows an insertion loss of 3.0 dB with a 3-dB bandwidth of 2.6 GHz and a rejection of larger than 20 dB at a 3-GHz separation from a center frequency of 65.0 GHz. This filter also shows a noise figure of 10.5 dB. The latter filter shows an insertion loss of 2.8 dB with a 10-dB bandwidth of 2.1 GHz at a center frequency of 65.0 GHz. It also shows an output power of 5.0 dBm at a 1-dB compression point. The loss variation due to temperature variation is successfully compensated using a gate bias control circuit. The size of the MMIC filters is 2.5 mm/spl times/1.1 mm.     

An interdigital bandpass filter embedded in LTCC for 5-GHz wireless LAN applications

This letter presents a compact interdigital stripline bandpass filter embedded in low temperature cofired ceramic for 5-GHz wireless LAN applications, including design, simulation, fabrication, and measurements. The filter measures 8 mm/spl times/7 mm/spl times/1.1 mm and exhibits an insertion loss of 3.6 dB, a return loss of 20 dB, and a 212-MHz passband with the midband frequency at 5.28 GHz. The filter is highly reproducible with good tolerance. A low noise amplifier (LNA) built on the top of the LTCC substrate with an embedded filter has the same bandwidth and midband frequency as those of the filter. Using this filter and an integrated chip, a small RF front-end receiver has been achieved.     

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.     

Miniature and tunable filters using MEMS capacitors

Microelectromechanical system (MEMS) bridge capacitors have been used to design miniature and tunable bandpass filters at 18-22 GHz. Using coplanar waveguide transmission lines on a quartz substrate (/spl epsiv//sub r/ = 3.8, tan/spl delta/ = 0.0002), a miniature three-pole filter was developed with 8.6% bandwidth based on high-Q MEMS bridge capacitors. The miniature filter is approximately 3.5 times smaller than the standard filter with a midband insertion loss of 2.9 dB at 21.1 GHz. The MEMS bridges in this design can also be used as varactors to tune the passband. Such a tunable filter was made on a glass substrate (/spl epsiv//sub r/ = 4.6, tan/spl delta/ = 0.006). Over a tuning range of 14% from 18.6 to 21.4 GHz, the miniature tunable filter has a fractional bandwidth of 7.5 /spl plusmn/ 0.2% and a midband insertion loss of 3.85-4.15 dB. The IIP/sub 3/ of the miniature-tunable filter is measured at 32 dBm for the difference frequency of 50 kHz. The IIP/sub 3/ increases to >50 dBm for difference frequencies greater than 150 kHz. Simple mechanical simulation with a maximum dc and ac (ramp) tuning voltages of 50 V indicates that the filter can tune at a conservative rate of 150-300 MHz//spl mu/s.     

A Fully Embedded LTCC Multilayer BPF for 3-D Integration of 40-GHz Radio

This paper demonstrates a low loss fully embedded multilayer bandpass filter (BPF) using low-temperature cofired ceramic (LTCC) technology for 3-D integration of 40-GHz multimedia wireless system (MWS) radio. The LTCC filter implemented in a stripline configuration occupies an area of only 5.5 times 2.3 times 0.6 mm including shielding structure and coplanar waveguide (CPW) transitions. The measured insertion loss was as small as 1.9 dB at a center frequency of 41.8 GHz, and the return loss was 12.2 dB including the loss associated with two CPW-to-stripline transitions. This six-layer BPF showed 3-dB bandwidth of 10.5% from 39.6 to 44.0 GHz at a center frequency of 41.8 GHz and suppressed the local oscillator (LO) signal to 20.2 dB at a local oscillator frequency of 38.8 GHz, making it suitable for the 40 GHz MWS applications.     

Multistage second-order microring-resonator filters with box-like spectral responses and relaxed fabrication tolerances

We demonstrate an optical filter based on multistage second-order microring resonators (MRs) with box-like spectral responses. Compared with single-stage high-order optical filters with the same number of MRs, the demonstrated structure has comparable performances in the aspects of passband flatness, rolling-off slope and insertion loss. Moreover, the architecture relaxes the fabrication tolerance, electrical wiring and tuning difficulty since there are only two MRs in each stage. We experimentally demonstrate this kind of optical filter with five stages, which shows a 3-dB bandwidth of ~17 GHz, a rolling-off slope of ~5 dB/GHz and an on-chip insertion loss of ~6 dB.     

Analysis and Application of 3-D LTCC Directional Filter Design for Multiband Millimeter-Wave Integrated Module

In this paper, we describe a systematic design and analysis procedure towards the successful implementation of 3-D low-temperature cofired ceramic (LTCC) multilayer loop directional filters at millimeter-wave frequencies. Directional filters represent a fundamental building block combining multiple filtering for mixing and multiplexing operations, hence reducing complexity while maintaining compactness. In this paper, different vertical coupling schemes are realized in order to implement the directional filters with the different performance optimums. The further use of the rectangular loop has been demonstrated as the optimum topology leading to the best performances. The filters have been measured to have less than 2.5-dB insertion loss in the bandpass path and higher than 25-dB rejection at 40 GHz, while occupying an area of 1.7times1.7 mm². They demonstrate 4.7%-6.3% fractional bandwidth with better than 20-dB isolation. 40-GHz multiplexers for multiband applications with 4-GHz/8-GHz frequency separations have been designed and measured to have approximately 3-dB insertion loss in each band with better than 20-dB isolation between the outputs in passbands. This is the first complete report on LTCC directional filter-based designs towards the system-on-package (SOP) solution for the multiband millimeter-wave wireless modules     

A Fully Embedded 60-GHz Novel BPF for LTCC System-in-Package Applications

In this paper, a novel LTCC stripline (SL) 60-GHz band-pass filter (BPF) composed of transitions to coplanar waveguide (CPW) pads for monolithic microwave integrated circuit integration is presented. For low-loss interconnection with active devices, a CPW-to-SL vertical via transition integrating air cavities and a CPW-to-CPW planar transition using internal ground planes are proposed and implemented. The fabricated transition shows an insertion loss of 1.6 dB and a reflection loss below -20 dB at the passband of the filter. The implemented SL BPF using dual-mode patch resonators shows a center frequency of 60.4 GHz, 3.5 % bandwidth, and reflection losses below -15 dB at the passband. Excluding the insertion loss of the transitions, the filter insertion loss reveals 4.0 dB     

High-performance microwave coplanar bandpass and bandstop filters on Si substrates

High-performance bandpass and bandstop microwave coplanar filters, which operate from 22 to 91 GHz, have been fabricated on Si substrates. This was achieved using an optimized proton implantation process that converts the standard low-resistivity (/spl sim/10 /spl Omega//spl middot/cm) Si to a semi-insulating state. The bandpass filters consist of coupled lines to form a series resonator, while the bandstop filter was designed in a double-folded short-end stub structure. For the bandpass filters at 40 and 91 GHz, low insertion loss was measured, close to electromagnetic simulation values. We also fabricated excellent bandstop filters with very low transmission loss of /spl sim/1 dB and deep band rejection at both 22 and 50 GHz. The good filter performance was confirmed by the higher substrate impedance to ground, which was extracted from the well-matched S-parameter equivalent-circuit data.     

Compact Wideband Bandpass Filters With Wide Upper Stopband

In this letter, a T-shaped microstrip feeding arrangement is proposed to design wideband bandpass filter (BPF) using shorted slot-line resonators. This feed line produces frequency selective external coupling which is utilized to suppress unwanted harmonics. Up to sixth order harmonics are suppressed. Other advantages are low passband group delay variation, ease of fabrication, low insertion loss (IL), and compact size. A fabricated BPF of fractional bandwidth 56.3% at midband frequency 2.3 GHz has a maximum IL of 1.2 dB in its passband and 30-dB upper stopband extends over 11.53 GHz     

Comparative Study of Feeding Techniques for Three-Dimensional Cavity Resonators at 60 GHz

In this paper, various topologies of feeding structures are comparatively evaluated for 60-GHz three-dimensional integrated cavity resonators used in three-dimensional integrated RF modules. Three excitation techniques (slot excitation with a shorting via, slot excitation with a lambdag/4 open stub, probe excitation) have been evaluated using simulated and measured data. The probe excitation is demonstrated as an attractive option for wideband applications due to its relatively wide bandwidth performance (~1.8%) and the strongest external coupling. The slot excitation with an open stub outperforms the other techniques, exhibiting the lowest insertion loss (~0.84 dB) for a 3-dB bandwidth of about 1.5% centered at 59.2 GHz and has the simplest fabrication     

A simple monolithically integrated optical receiver consisting of an optical preamplifier and a p-i-n photodiode

We demonstrate a monolithic optical receiver consisting of the integration of a semiconductor optical amplifier and a p-i-n photodetector based on asymmetric twin-waveguide technology. Multiple quantum wells with 1% compressive strain are used for both optical amplification and detection. The device has a peak external responsivity of 8.2/spl plusmn/0.4 A/W (/spl sim/9-dB fiber-to-detector gain), and a 3-dB optical bandwidth of 11/spl plusmn/1GHz, equivalent to a 265-GHz gain-bandwidth product. The efficient coupling of light between individual optical components is achieved by a lateral adiabatic taper that reduces the fabrication complexity. This work represents a considerable simplification over previously demonstrated high-performance integrated optical receivers.     

Applications of layer-by-layer polymer stereolithography for three-dimensional high-frequency components

A laser-based layer-by-layer additive process, stereolithography, is used to create truly three-dimensional (3-D) structures for high-frequency applications. High aspect-ratio complicated 3-D structures embedded inside of a layer-by-layer package are created by this process. Previously, Q's greater than 3000 and tolerances of /spl sim/0.19% have been achieved for embedded resonators. In this paper, more applications are demonstrated. Particular examples include the integration of a nonplanar monopole antenna coupled to a high-Q embedded cavity with only 0.26% shift in resonant frequency (19.37 GHz) and a slight 0.06% reduction in bandwidth compared to simulation. Stacked cavities and coupling sections within a substrate are also demonstrated to create vertically integrated filters. For 2% bandwidth two-pole filters, insertion losses as small as 0.27 dB are measured. Furthermore, a vertically integrated 1.2% four-pole filter is demonstrated with acceptable performance without tuning after fabrication. These applications illustrate that the laser-based stereolithography process is suitable for the integration of high-frequency and high-Q 3-D structures within a package.     

A compact LTCC-based Ku-band transmitter module

Presents design, implementation, and measurement of a three-dimensional (3-D)-deployed RF front-end system-on-package (SOP) in a standard multi-layer low temperature co-fired ceramic (LTCC) technology. A compact 14 GHz GaAs MESFET-based transmitter module integrated with an embedded bandpass filter was built on LTCC 951AT tapes. The up-converter MMIC integrated with a voltage controlled oscillator (VCO) exhibits a measured up-conversion gain of 15 dB and an IIP3 of 15 dBm, while the power amplifier (PA) MMIC shows a measured gain of 31 dB and a 1-dB compression output power of 26 dBm at 14 GHz. Both MMICs were integrated on a compact LTCC module where an embedded front-end band pass filter (BPF) with a measured insertion loss of 3 dB at 14.25 GHz was integrated. The transmitter module is compact in size (400 /spl times/ 310 /spl times/ 35.2 mil/sup 3/), however it demonstrated an overall up-conversion gain of 41 dB, and available data rate of 32 Mbps with adjacent channel power ratio (ACPR) of 42 dB. These results suggest the feasibility of building highly SOP integrated RF front ends for microwave and millimeter wave applications.     

Compact and wideband microstrip bandstop filter

A novel one-section bandstop filter (BSF), which possesses the characteristics of compact size, wide bandwidth, and low insertion loss is proposed and fabricated. This bandstop filter was constructed by using single quarter-wavelength resonator with one section of anti-coupled lines with short circuits at one end. The attenuation-pole characteristics of this type of bandstop filters are investigated through TEM transmission-line model. Design procedures are clearly presented. The 3-dB bandwidth of the first stopband and insertion loss of the first passband of this BSF is from 2.3 GHz to 9.5 GHz and below 0.3 dB, respectively. There is good agreement between the simulated and experimental results.     

Compact and low-loss interleave filter employing lattice-form structure and silica-based waveguide

This paper describes a compact and practical interleave filter with uniform multi/demultiplexing properties and a wide operational wavelength range realized by using a lattice-form structure and a silica-based waveguide. In the design, we optimized the bandwidth by controlling the lattice stage number and the loss ripple in the spectrum. Moreover, we propose a novel coupler with a large fabrication tolerance, a new tandem configuration that provides uniform characteristics and low dispersion, a polarization dependence compensation method, and a folded configuration, which are effective in realizing a high-performance interleave filter. Based on the above techniques, we fabricated a 50-GHz channel spacing interleave filter by using planar-lightwave-circuit technologies and demonstrated that it performed well throughout the C-band, exhibiting a low insertion loss of about 2 dB, a low chromatic dispersion of within +/-20 ps/nm, a 1-dB passband width of over 34 GHz, and a 30-dB stopband width of over 25 GHz, which are sufficient for a 10-Gbps transmission system.     

A miniature 2.1-GHz low loss microstrip filter with independent electric and magnetic coupling

A miniature planar two-pole microstrip filter with independent electric and magnetic coupling has been developed at 2.1 GHz. The independent coupling allows separate control of two transmission zeroes and result in a sharp filter skirt. The two-pole filter occupies an area of 6.6/spl times/4.6 mm/sup 2/ (30 mm/sup 2/) on an /spl epsi//sub r/=10.2 substrate, and shows a 5% bandwidth (100 MHz) and an insertion loss of 1.4 dB. The filter unloaded Q is 150 at 2.1 GHz which is much better than compatible filters done in LTCC technology.     

Passband-width broadening design for WDM filter with lattice-forminterleave filter and arrayed-waveguide gratings

We successfully fabricated a high channel count and flat-top wavelength-division-multiplexing filter by integrating a waveguide-type interleave filter and two arrayed-waveguide grating on one chip. Optimizing the loss ripple of the interleave filter, we realized a 50-GHz spacing, 102-channel ports, a 1-dB passband of 30 GHz, and an insertion loss of 4 dB     

Precision fabrication techniques and analysis on high-Q evanescent-mode resonators and filters of different geometries

High-Q evanescent-mode resonators and filters are realized by both silicon micromachining and layer-by-layer polymer processing. Capacitively loaded cavities can be reduced to a size much smaller than a wavelength, but still have a much higher unloaded Q than lumped elements. The loaded resonators are utilized for reduced-size filters with a low insertion loss enabled by the relatively high-Q factor. The small fabrication tolerances of silicon micromachining and polymer stereolithography processing enable the realization of highly loaded evanescent-mode resonators and filters. A 14-GHz resonator micromachined in silicon has a volume of 5 mm /spl times/ 5 mm /spl times/ 0.45 mm, representing a resonant frequency reduction of 66.8% compared to an empty cavity of the same dimensions. The polymer-based fabrication is used to create resonators of different three-dimensional geometries with Q's up to 1940 and frequency reductions up to 49.9%. An insertion loss of 0.83 dB is measured in a 1.69% bandwidth filter created by polymer processing with a frequency reduction of 47% compared to an unloaded cavity. The frequency sensitivity to fabrication tolerances of these structures is also analyzed.