A 75 GHz to 115 GHz quasi-optical amplifier

A wideband quasi-optical amplifier employing two pyramidal back-to-back horns has been developed. Using a four-stage W-band low noise amplifier (LNA) designed and fabricated by Martin Marietta Laboratories, the quasi-optical amplifier gives a system gain greater than 11 dB from 86 GHz to 113 GHz without any low frequency oscillations. A peak system gain of 15.5 dB is measured at 102 GHz, and the measured noise figure of the system is 7.4 dB at 94 GHz. The quasi-optical amplifier design maintains the same polarization of the received and transmitted signal, provides better than -40 dB isolation, and can be fabricated monolithically at millimeter-wave frequencies     

Higher Order Cochlea-Like Channelizing Filters

A design method is presented for contiguous-channel multiplexing filters with many channels covering a wide bandwidth. The circuit topology extends previous work on cochlea-like channelizers by introducing multiple resonator-channel filter sections. The new design provides increased stopband rejection, lower insertion loss, and improved passband shape compared with the earlier version while retaining a simple design method and a compact layout, and requires no post-fabrication tuning. Results of a three-pole ten-channel channelizer covering from 182 MHz to 1.13 GHz with 17.5% bandwidth channels and 1.1-dB insertion loss are presented, and agree well with theory. A discussion of the power handling of planar channelizers is also presented.      

A 40–50-GHz SiGe 1 : 8 Differential Power Divider Using Shielded Broadside-Coupled Striplines

This paper presents a 1 : 8 differential power divider implemented in a commercial SiGe BiCMOS process using fully shielded broadside-coupled striplines integrated vertically in the silicon interconnect stackup. The 1 : 8 power divider is only 1.12 $,times,$1.5 mm$^{2}$ including pads, and shows 0.4-dB rms gain imbalance and $≪ {hbox{3}}^{circ}$ rms phase imbalance from 40 to 50 GHz over all eight channels, a measured power gain of ${hbox{14.9}} pm {hbox{0.6}}$ dB versus a passive divider at 45 GHz, and a 3-dB bandwidth from 37 to 52 GHz. A detailed characterization of the shielded broadside-coupled striplines is presented and agrees well with simulations. These compact lines can be used for a variety of applications in SiGe/CMOS millimeter-wave circuits, including differential signal distribution, miniature power dividers, matching networks, filters, couplers, and baluns.      

Millimeter-wave tapered-slot antennas on synthesized lowpermittivity substrates

This paper presents 30-GHz linear-tapered slot antennas (LTSA) and 94-GHz constant-width slot antennas (CSWA) on synthesized low dielectric constant substrates (ϵ_r=2.2). The performance of tapered-slot antennas (TSA) is sensitive to the effective thickness of the substrate. We have reduced the effective thickness by selectively machining holes in the dielectric substrate. The machined substrate antenna radiation patterns were significantly improved independent of the machined hole size or lattice as long as the quasi-static effective thickness remained the same, even if the hole/lattice geometry is comparable to a wavelength. The method was applied at 94 GHz on a CSWA with excellent radiation pattern improvement, making it suitable for f/1.6 imaging array applications     

High-isolation CPW MEMS shunt switches. 2. Design

For pt.1 see ibid., vol.48, no.6, p.1045-1052 (2000). In this paper, the second of two parts, the equivalent RLC model of the shunt switch is used in the design of tuned two- and four-bridge “cross” switches from 10 to 40 GHz. The cross switch attained an insertion loss of less than 0.3-0.6 dB, a return loss below -20 dB from 22 to 38 GHz in the up state, and a down-state isolation of 45-50 dB with only 1.5 pF of down-state capacitance (C_d). Also, an X-band microelectromechanical system (MEMS) switch with an insertion loss of less than 0.2 dB and an isolation of 35 dB is presented. This is done by inductively tuning the LC series resonance of the shunt switch. The MEMS bridge height is 1.5-2.5 μm, resulting in a pull-down voltage of 15-25 V. Application areas are in low-loss high-isolation communication and radar     

Millimeter-wave double-dipole antennas for high-gain integratedreflector illumination

A double-dipole antenna backed by a ground plane has been fabricated for submillimeter wavelengths. The double-dipole antenna is integrated on a thin dielectric membrane with a planar detector at its center. Measured feed patterns at 246 GHz agree well with theory and demonstrate a rotationally symmetric pattern with high coupling efficiency to Gaussian beams. The input impedance is around 50 Ω and will match well to a Schottky diode or SIS detector. The double-dipole antenna served as the feed for a small machined parabolic reflector. The integrated reflector had a measured gain of 37 dB at 119 μm. This makes the double-dipole antenna ideally suited as a feed for high-resolution tracking or for long-focal-length Cassegrain antenna systems     

Off-axis properties of silicon and quartz dielectric lens antennas

The theoretical far-field patterns and Gaussian-beam coupling efficiencies are investigated for a double-slot antenna placed off aids on extended hemispherical silicon and quartz lenses. Measured off-axis radiation patterns at 250 GHz agree well with the theory. Results are presented that show important parameters versus off-axis displacement: scan angle, directivity, Gaussicity, and reflection loss. Directivity contour plots are also presented and show that near-diffraction limited performance can be achieved at off-axis positions at nonelliptical extension lengths. Some design rules are discussed for imaging arrays on dielectric lens antennas     

Some important properties of waveguide junction generalizedscattering matrices in the context of the mode matching technique

Some important properties for the generalized scattering matrix [S] of waveguide step discontinuities, in the context of the mode matching technique, are derived by considering the conservation of the complex power and self reaction across the discontinuities. Apart from their theoretical significance, these properties are useful for the numerical verification of the mode matching technique when designing waveguide circuits. The properties are shown to apply in the general case of junctions between lossless inhomogeneously filled waveguides, and they are proven to remain valid irrespective of the number of modes retained in the field expansions. During the process of deriving these properties, the mode matching technique for a waveguide step discontinuity is revisited and some subtle theoretical issues are resolved. In this framework, the selection of the appropriate testing modes for enforcing the field continuity conditions across the discontinuity is rigorously justified. In addition, two distinct mode matching formulations corresponding to the two possible orthogonality relations among the eigenmodes of lossless waveguides are proven to be equivalent. Finally, it is shown that the correct application of the held boundary conditions across the step discontinuity implies requirements on the number of modes used to represent the fields, in each waveguide, which are compatible with the relative convergence criterion     

A Millimeter-Wave (40–45 GHz) 16-Element Phased-Array Transmitter in 0.18-$mu$ m SiGe BiCMOS Technology

This paper demonstrates a 16-element phased-array transmitter in a standard 0.18-mum SiGe BiCMOS technology for Q-band satellite applications. The transmitter array is based on the all-RF architecture with 4-bit RF phase shifters and a corporate-feed network. A 1:2 active divider and two 1:8 passive tee-junction dividers constitute the corporate-feed network, and three-dimensional shielded transmission-lines are used for the passive divider to minimize area. All signals are processed differentially inside the chip except for the input and output interfaces. The phased-array transmitter results in a 12.5 dB of average power gain per channel at 42.5 GHz with a 3-dB gain bandwidth of 39.9-45.6 GHz. The RMS gain variation is < 1.3 dB and the RMS phase variation is < for all 4-bit phase states at 35-50 GHz. The measured input and output return losses are < -10 dB at 36.6-50 GHz, and <-10 dB at 37.6-50 GHz, respectively. The measured peak-to-peak group delay variation is plusmn 20 ps at 40-45 GHz. The output P_-1dB is -5plusmn1.5 dBm and the maximum saturated output power is - 2.5plusmn1.5 dBm per channel at 42.5 GHz. The transmitter shows <1.8 dB of RMS gain mismatch and < 7deg of RMS phase mismatch between the 16 different channels over all phase states. A - 30 dB worst-case port-to-port coupling is measured between adjacent channels at 30-50 GHz, and the measured RMS gain and phase disturbances due to the inter-channel coupling are < 0.15 dB and < 1deg, respectively, at 35-50 GHz. All measurements are obtained without any on-chip calibration. The chip consumes 720 mA from a 5 V supply voltage and the chip size is 2.6times3.2 mm².     

RF MEMS,BST, and GaAs varactor system‐level response in complex modulation systems

This article presents the response of RF microelectromechanical systems (RF MEMS), barium strontium titanate (BST), and gallium arsenide (GaAs)‐based tunable filters and reconfigurable matching networks to a wideband code‐division‐multiple‐access signal centered at 1.95 GHz. The RF MEMS tunable filter and impedance tuner result in very low intermodulation distortion and spectral regrowth compared to their BST and GaAs counterparts. The linearity of the BST and GaAs tunable networks improves considerably by using a series combination of BST and GaAs varactors, but the RF MEMS‐based networks still show the best linearity of all three technologies. Also, it is shown that the reconfigurable networks, tuned with capacitive RF MEMS can handle up to 1 W of RF power with no self‐actuation. © 2007 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2008.