Michele Squartecchia

Large-signal modeling of multi-finger InP DHBT devices at millimeter-wave frequencies

A large-signal modeling approach has been developed for multi-finger devices fabricated in an Indium Phosphide (InP) Double Heterojunction Bipolar Transistor (DHBT) process. The approach utilizes unit-finger device models embedded in a multi-port parasitic network. The unit-finger model is based on an improved UCSD HBT model formulation avoiding an erroneous RciCbci transit-time contribution from the intrinsic collector region as found in other III-V based HBT models. The mutual heating between fingers is modeled by a thermal coupling network with parameters extracted from electro-thermal simulations. The multi-finger modeling approach is verified against measurements on an 84 GHz power amplifier utilizing four finger InP DHBTs in a stacked configuration.

Low conversion loss 94 GHz and 188 GHz doublers in InP DHBT technology

An Indium Phosphide (InP) Double Heterojunction Bipolar Transistor (DHBT) process has been utilized to design two doublers to cover the 94 GHz and 188 GHz bands. The 94 GHz doubler employs 4-finger DHBTs and provides conversion loss of 2 dB. A maximum output power of nearly 3 dBm is measured while the doubler is not entirely saturated. The DC power consumption is 132 mW. The 188 GHz doubler utilizes a 1-finger DHBT. Conversion loss of 2 dB and a maximum output power of −1 dBm are achieved at 188 GHz with on-wafer measurements. The DC power consumption is 24 mW under saturated conditions. Both doublers operate over a broad bandwidth. The total circuit area of each chip is 1.41 mm2.

3D thermal simulations and modeling of multi-finger InP DHBTs for millimeter-wave power amplifiers

This paper presents the comparison between the simulated and measured thermal resistance of InP Double Heterojunction Bipolar Transistors (DHBT). 3D thermal simulations were carried out in order to compute the temperature distribution across the full structure due to a constant power excitation of devices with up to 8 emitter fingers. The surface temperature profile was then used to compute the average thermal resistance of the multi-finger devices. The comparison with the corresponding results obtained by electrical measurements show a good agreement. The temperature profiles from several simulations are used to extract the thermal resistance matrix used in the electro-thermal coupling network of a compact large-signal model.

75 GHz InP DHBT power amplifier based on two-stacked transistors

In this paper we present the design and measurements of a two-stage 75-GHz InP Double Heterojunction Bipolar Transistor (DHBT) power amplifier (PA). An optimized two-stacked transistor power cell has been designed, which represents the building block in the power stage as well as in the driver stage of the power amplifier. Besides the series voltage addition of the stacked structure, parallel power combining techniques were adopted to increase the output power of the MMIC amplifier, with four-way and eight-way corporate power combiners at the driver and power stages, respectively. At 75 GHz, the power amplifier exhibits a small signal gain of G = 12.6 dB, output power at 1-dB compression of Pout, 1dB = 18.6 dBm and a saturated output power of Psat > 21.4 dBm.

InP DHBT technology for power amplifiers at mm-wave frequencies

An InP Double Heterojunction Bipolar Transistor (DHBT) technology is presented for millimeter-wave power amplifiers at E-band and higher frequencies. Single- and multi-finger transistors with 0.7m emitter width and emitter lengths of 5, 7, 10m are designed for high frequency and high power applications. The static and AC performances of the fabricated devices are discussed. Reported cutoff frequency and maximum oscillation frequency are ft=267GHz and fmax=450GHz for a 0.75mP2 single-finger device, respectively. Results from large-signal measurements at 30GHz are reported for single and 4-finger devices. Ballasted devices are introduced to improve thermal behaviour and to increase the limits of the safe operating area (SOA). The SOA is improved approximately by 75% for 4-finger devices with 0.710m2 emitter. A fabricated monolithic microwave integrated circuit (MMIC) at E-band based on stacked InP DHBTs is presented and its performances reported to demonstrate the power capabilities of the technology.

A physical based equivalent circuit modeling approach for ballasted InP DHBT multi-finger devices at millimeter-wave frequencies

Multifinger InP DHBTs can be designed with a ballasting resistor to improve power capability. However accurate modeling is needed to predict high frequency behavior of the device. This paper presents two distinct modeling approaches: one based on EM simulations and one based on a physical equivalent circuit description. In the first approach, the EM simulations of contact pads and ballasting network are combined with the small-signal model of the intrinsic device. In the second approach, the ballasting network is modeled with lumped components derived from physical analysis of the layout and then combined with EM simulated contact pads and with the device model. The models are validated against S-parameters measurements of real devices up to 65 GHz showing good agreement in terms of maximum available gain. In addition, a MAG of 2-4 dB at 170 GHz shows that ballasted devices can be employed for power amplifiers in D band.

Flicker noise comparison of direct conversion mixers using Schottky and HBT dioderings in SiGe:C BiCMOS technology

In this paper, we present flicker noise measurements of two X-band direct conversion mixers implemented in a SiGe:C BiCMOS technology. Both mixers use a ring structure with either Schottky diodes or diode-connected HBTs for double balanced operation. The mixers are packaged in a metal casing on an Arlon 25N substrate to shield the sensitive noise measurement. Conversion loss measurements of both mixers is performed both for on-wafer and packaged versions. The experimental results shows that the Schottky diode mixer exhibits a 1/f noise corner frequency of 250 kHz, while the diode connected HBT circuit demonstrates a 1/f noise corner frequency around 10 kHz.

Design of a SiGe BiCMOS canceller for low frequency noise reduction in direct conversion receivers

Direct-conversion receivers are increasingly employed in many applications, such as wireless communications and radars. Indeed, they represent an effective alternative to heterodyne receivers, as they allow a higher level of integration. However, performance limitations are imposed by the leakage of the local oscillator (LO) toward the RF port of the mixer (Figure 1(a)). This causes the LO self-mixing phenomenon, which is responsible of a significant DC offset at the output of the receiver (Figure 1(b)). In turn, this DC offset gives rise to a high level of low frequency noise affecting the signal recovery at baseband (R. S. Michaelsen et al., IEEE Microwave and Wireless Components Letters, Vol. 23 No. 2, 2013, pp. 66–68).