R. Pullela

Active and nonlinear wave propagation devices in ultrafast electronics and optoelectronics

We describe active and nonlinear wave propagation devices for generation and detection of (sub)millimeter wave and (sub)picosecond signals. Shock-wave nonlinear transmission lines (NLTLs) generate /spl sim/4-V step functions with less than 0.7-ps fall times. NLTL-gated sampling circuits for signal measurement have attained over 700-GHz bandwidth. Soliton propagation on NLTLs is used for picosecond impulse generation and broadband millimeter-wave frequency multiplication. Picosecond pulses can also be generated on traveling-wave structures loaded by resonant tunneling diodes. Applications include integration of photodetectors with sampling circuits for picosecond optical waveform measurements and instrumentation for millimeter-wave waveform and network (circuit) measurements both on-wafer and in free space. General properties of linear and nonlinear distributed devices and circuits are reviewed, including gain-bandwidth limits, dispersive and nondispersive propagation, shock-wave formation, and soliton propagation. >

SCALING OF InGaAs/InAlAsHBTs FOR HIGH SPEED MIXED-SIGNAL AND mm-WAVE ICs

High bandwidths are obtained with heterojunction bipolar transistors by thinning the base and collector layers, increasing emitter current density, decreasing emitter contact resistivity, and reducing the emitter and collector junction widths. In mesa HBTs, minimum dimensions required for the base contact impose a minimum width for the collector junction, frustrating device scaling. Narrow collector junctions can be obtained by using substrate transfer processes, or -if contact resistivity is greatly reduced -by reducing the width of the base Ohmic contacts in a mesa structure. HBTs with submicron collector junctions exhibit extremely high fmax and high gains in mm-wave ICs. Logic gate delays are primarily set by depletion-layer charging times, and neither fτ nor fmax is indicative of logic speed. For high speed logic, epitaxial layers must be thinned, emitter and collector junction widths reduced, current density increased, and emitter parasitic resistance decreased. Transferred-substrate HBTs have obtained 21 dB unilateral power gain at 100 GHz. If extrapolated at -20 dB/decade, the power gain cutoff frequency fmax is 1.1 THz. Transferred-substrate HBTs have obtained 295 GHz fτ. Demonstrated ICs include lumped and distributed amplifiers with bandwidths to 85 GHz, 66 GHz master-slave flip-flops, and 18 GHz clock rate Δ-Σ ADCs.

Single-chip multiband WCDMA/HSDPA/HSUPA/EGPRS transceiver with diversity receiver and 3G DigRF interface without SAW filters in transmitter / 3G receiver paths

There has been an increased demand for 3G cell phones that support multiple bands of operation and are backward compatible with the 2G/2.5G standard to provide coverage where 3G networks have not yet been fully deployed. The transceiver design for such a handset becomes complicated with the need for separate transceivers for 3G and 2G/2.5G [1,2] or for multiple inter-stage receive / transmit SAW filters [3]. A single-chip transceiver that operates as a multimode multiband radio and eliminates the inter-stage receive / transmit SAW filters is presented. Figure 6.3.1 shows the block diagram of the transceiver with 7 primary and 4 diversity bands in WCDMA, and quad band in GSM. The transceiver is designed to operate in any of the UTRA bands 1 to 10, with the exception of band 7. It supports HSDPA (Cat 1–12), HSUPA (Cat 1–6), EGPRS (Classes 1–12, 30–39), and compressed mode of EGPRS / WCDMA operation. The transceiver is compliant with 3G DigRF interface 3.09.

Low Flicker-Noise Quadrature Mixer Topology

A mixer topology that improves NF at low offset frequencies by reducing 1/f noise contributions is fabricated in 0.13mum CMOS. The NF at 10kHz is 9dB, which is 9dB less than a conventional mixer. The mixer also has 2dB higher gain, improved quadrature matching, higher IP2, straightforward implemention, and is robust over PVT

Capacitive-division traveling-wave amplifier with 340 GHz gain-bandwidth product

We report capacitive-division traveling-wave amplifiers having measured midband gains of 8 dB with a 1-98 GHz 3-dB-bandwidth, and 11 dB gain with a 1-96 GHz bandwidth. The capacitive-division topology raises the input Q of each cell, giving the amplifier increased bandwidth over conventional designs with the same active device technology; using 0.15-/spl mu/m gate length InGaAs/InAlAs HEMTs, bandwidths exceeding 150 GHz are feasible.<<ETX>>We report capacitive-division traveling-wave amplifiers having measured midband gains of 8 dB with a 1-98 GHz 3-dB-bandwidth, and 11 dB gain with a 1-96 GHz bandwidth. The capacitive-division topology raises the input Q of each cell, giving the amplifier increased bandwidth over conventional designs with the same active device technology; using 0.15-/spl mu/m gate length InGaAs-InAlAs HEMTs, bandwidths exceeding 150 GHz are feasible.<<ETX>>

80 GHz distributed amplifiers with transferred-substrate heterojunction bipolar transistors

We report distributed amplifiers with 80 GHz bandwidth, 6.7 dB gain and /spl sim/70 GHz bandwidth, 7.7 dB gain. These amplifiers were fabricated in the transferred-substrate heterojunction bipolar transistor integrated circuit technology. Transferred-substrate HBTs have very high f/sub max/ (>400 GHz) and have yielded distributed amplifiers with record gain-bandwidth product.

An integrated closed-loop polar transmitter with saturation prevention and low-IF receiver for quad-band GPRS/EDGE

This paper describes a 2.5G cellular transceiver with standard DigRF interface, implemented in a low-cost 0.13µm CMOS process. This is the first CMOS single-chip, polar closed-loop transmitter, excluding the power amplifier (PA). This transmitter achieves an efficiency of 26% in EDGE mode by linearizing a saturated PA in a closed-loop feedback system. This is much higher than the typical 15-to-18% efficiency of systems using a linear PA [1]. Typical high-band/ low-band performance of −62/−64dBc in 30kHz for 400kHz offset spectral mask and 1.4/1.7% EVM in EDGE mode are significantly better than those reported earlier [1–3]. Using a low-noise quadrature mixer topology, the receiver, including T/R switch and SAW filters, achieves a sensitivity of −110dBm. The RF solution, consisting of PAs in a multi-chip integrated antenna switch module, SAW filters with integrated matching components and the transceiver, shown in Fig. 6.1.1, is the smallest form factor available in the market today.

Deep submicron transferred-substrate heterojunction bipolar transistors

Using e-beam lithography and combined reactive-ion and wet-chemical etches, we have fabricated transferred-substrate heterojunction bipolar transistors (HBTs) with 0.2 μm emitter and 0.6 μm collector widths and a measured DC current gain of 14. Devices with 0.4 μm emitter and 1.0 μm collector widths obtain record 500 GHz f/sub max/ value.

A transferred-substrate HBT wide-band differential amplifier to 50 GHz

Differential amplifiers are used in automatic gain control amplifiers and limiting amplifiers in fiber-optic receivers. Here we present a differential amplifier fabricated in the transferred-substrate heterojunction bipolar transistor (HBT) integrated circuit technology. The amplifier has a gain of 11 dB and the 3-dB bandwidth is greater than 50 GHz. Two gain stages with DC interstage coupling are used. Biasing is through active current mirrors and a single negative power supply. A bandwidth of 50 GHz is the highest bandwidth ever reported for a broad-band differential amplifier in any technology.

48 GHz digital ICs using transferred-substrate HBTs

Using substrate transfer processes, we have fabricated heterojunction bipolar transistors with submicron emitter-base and collector-base junctions, minimizing RC parasitics and increasing f/sub max/ to 500 GHz. The process also provides a microstrip wiring environment on a low-/spl epsiv//sub r/ dielectric substrate. First design iterations of ECL master-slave flip-flops exhibit 48 GHz maximum clock frequency when connected as static frequency dividers.