Gabriel M. Rebeiz

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.

Single- and dual-polarized millimeter-wave slot-ring antennas

Single- and dual-polarized dielectric lens-supported slot-ring antennas have been developed for operation at millimeter-wave frequencies. The antennas are fed with a coplanar waveguide (CPW) to be compatible with uniplanar mixers and low-noise amplifiers, and the feedline is shown to have a minimal effect on the antenna performance. The measured antenna patterns agree well with theoretical results and have symmetric main beams, low sidelobe levels (<-15 dB), low cross polarization (<-20 dB), and 27 dB directivity. A 2/spl times/2 array of single-polarized slot-ring antennas for monopulse applications demonstrates excellent patterns at 94 GHz with -3 dB crossover power levels in both elevation and azimuth scans. The dual-polarized slot ring antenna patterns are nearly identical to those of the single-polarized antenna, and two-port isolation is as low as -25 dB. The dielectric lens-supported slot-ring antenna is an excellent candidate for compact, low-cost millimeter-wave systems with fixed or variable polarization capabilities.

A W-band dielectric-lens-based integrated monopulse radar receiver

An integrated monopulse receiver has been developed for tracking applications at W-band frequencies. The receiver is based on dielectric-lens-supported, coplanar-waveguide-fed slot-ring antennas integrated with uniplanar subharmonic mixers. The design center frequency is 94 GHz and the IF bandwidth is 2-4 GHz. The measured DSB conversion losses of the individual receiver channels range from 14.4 to 14.7 dB at an LO frequency of 45.0 GHz and an IF of 1.4 GHz. This includes the lens reflection and absorption losses, backside radiation, RF feedline loss, mixer conversion loss, and IF distribution loss. Excellent monopulse patterns are achieved with better than 45 dB difference pattern nulls using IF monopulse processing. This translates to sub-milliradian angular accuracy for a 24 mm aperture. Better than 25 dB nulls are possible over a 600 MHz bandwidth.

A 6–18 GHz 5-bit active phase shifter

This paper presents a 6–18 GHz active 5-bit phase shifter in 0.18-µm SiGe BiCMOS technology based on a phase interpolation technique. An L-C resonance-based quadrature all-pass filter generates the I/Q reference signal with high I/Q accuracy over a wide bandwidth, and integrated current-mode DACs control the I/Q amplitudes to achieve 5-bit phase resolution. The phase shifter shows 19.5 dB of power gain with < 1.1 dB of RMS gain variation for all 5-bit phase states at 12 GHz, and the 3-dB gain bandwidth is 7.5–15.2 GHz. The measured RMS phase error is < 3o at 6.4–10.2 GHz and < 5.6° at 6–18 GHz achieving greater than 5-bit accuracy. Within the 3-dB gain bandwidth, the NF ranges from 4 to 5.7 dB and the NF variation is ±0.12 dB for all phase states. The total current consumption is 18.7 mA (phase shifter core: ∼ 3 mA) from a 3.3 V supply voltage and overall chip size is 1.2×0.75 mm2 (phase shifter core: 0.45×0.35 mm2).

A 90-100 GHz double-folded slot antenna

A double-folded slot antenna (DFS) has been designed, fabricated, and tested at 90-100 GHz. The antenna shows a very wideband impedance around 20 /spl Omega/ from 85 to 110 GHz. The low impedance is compatible with superconductor-insulator-superconductor (SIS) junctions, Schottky diodes or high electron mobility transistor (HEMT) amplifiers, which require a low impedance at millimeter wave frequencies. The antenna is placed on a dielectric lens to synthesize a semi-infinite substrate and realize high-directivity patterns. The measured radiation patterns agree very well with theoretical calculations and demonstrate symmetric main beams and sidelobe levels below -15 db over a 10% bandwidth. The double folded slot antenna is an attractive candidate for low-cost wideband millimeter-wave monolithic microwave integrated circuits (MMIC) front ends.

An Improved Wideband All-Pass I/Q Network for Millimeter-Wave Phase Shifters

This paper presents the design and analysis of an improved wideband in-phase/quadrature (I/Q) network and its implementation in a wideband phased-array front-end. It is found that the addition of two resistors (Rs) in the all-pass I/Q network results in improved amplitude and phase performance versus capacitance loading and frequency, which is essential for wideband millimeter-wave applications. A prototype 60-80-GHz phased-array front-end based on 0.13-μm SiGe BiCMOS is demonstrated using the improved quadrature all-pass filter and with 4-bit phase-shifting performance at 55-80 GHz. Application areas are in wideband millimeter-wave systems.

An X- and Ku-Band 8-Element Linear Phased Array Receiver

This paper presents an 8-element linear phased array receiver in 0.18-mum SiGe BiCMOS technology for X-and Ku-band applications. The array receiver adopts RF phase shifting architecture and the active 4-bit phase shifter synthesizes a phase by adding two properly weighted I-and Q-input. With all the digital control circuitry, bandgap reference and ESD protection for all I/O pads, the receiver consumes 170 mA from a 3.3 V supply voltage. The receiver shows about 20 dB of power gain per channel at 12 GHz with a 3-dB gain bandwidth from 8.5 to 14.5 GHz. The rms gain error is less than 0.9 dB and the rms phase error is less than 6deg at 6-18 GHz for all the 4-bit phase states. The minimum NF is 3.85 dB at 10-11 GHz and typical input PldB at 12 GHz is -31 dBm. The overall chip size is 2.2times2.45 mm2. To our knowledge, this is the first demonstration of an RF-based phased array in a silicon chip with the record rms phase and gain errors at 6-18 GHz.

X/Ku-band 8-element phased arrays based on single silicon chips

This paper presents a complete 8-element X/Ku-band phased array based on a single silicon chip. The phased array is integrated together with the antennas and digital control circuitry on a single Teflon board. The chip-on-board package, together with 8 X/Ku-band RF inputs and one RF output in a 2.2×2.5mm2 area, and the appropriate grounding and Vcc connections, are modeled using a 3-D EM solver. The design results in a low coupling between the different RF ports, and ensures stability even with a channel gain of 20 dB at 12 GHz. The measured patterns show a near-ideal performance up to a scan angle of 60° with an instantaneous scanning bandwidth of 11.4–12.6 GHz (limited by non true-time delay connections between the antennas and the chip). Temperature tests indicate that the silicon chip maintains excellent phase stability and rms phase error up to 100°C. To our knowledge, this represents the first system-level measurements on silicon-chip phased arrays.

Highly dense microwave and millimeter-wave phased array T/R modules using CMOS and SiGe RFICs

We have used silicon technologies to build highly dense phased array for X to W-band applications. Typical designs include an 8-element 8–16 GHz SiGe phased array receiver, a 16-element 30–50 GHz SiGe transmit phased array, a miniature (&#60; 3mm2) and low power (&#60;100 mW) CMOS phased array receiver at 24 GHz, and a 4-element SiGe/CMOS Tx/Rx phased array at 34–38 GHz with 5-bit amplitude and phase control, a 2-antenna 4-simultaneous beam phased array chip at 15 GHz. Also, a miniature 8×8 Butler Matrix with &#60; 3 dB loss in 0.13 um CMOS has been developed for multibeam applications. It is shown that silicon chips can be used to lower the cost of phased arrays with a significant impact at Ku, K and W-band applications where there is so little available space behind each antenna element due to the very small element area.

Highly dense microwave and millimeter-wave phased array T/R modules and Butler matrices using CMOS and SiGe RFICs

We have used silicon technologies to build highly dense phased array for X to W-band applications. Typical designs include an 8-element 8–16 GHz SiGe phased array receiver, a 16-element 30–50 GHz SiGe transmit phased array, a miniature (< 3mm2) and low power (<100 mW) CMOS phased array receiver at 24 GHz, and a 4-element SiGe/CMOS Tx/Rx phased array at 34–38 GHz with 5-bit amplitude and phase control, a 2-antenna 4-simultaneous beam phased array chip at 15 GHz. Also, a miniature 8×8 Butler Matrix with < 3 dB loss in 0.13 um CMOS has been developed for multibeam applications. It is shown that silicon chips can be used to lower the cost of phased arrays with a significant impact at Ku, K and W-band applications where there is so little available space behind each antenna element due to the very small element area.