Title page for ETD etd-05082001-131602


Type of Document Master's Thesis
Author Johnson, Daniel Austin
Author's Email Address johnsond@vt.edu
URN etd-05082001-131602
Title 5-6 GHz RFIC Front-End Components in Silicon Germanium HBT Technology
Degree Master of Science
Department Electrical and Computer Engineering
Advisory Committee
Advisor Name Title
Raman, Sanjay Committee Chair
Bostian, Charles W. Committee Member
Pratt, Timothy J. Committee Member
Keywords
  • Front-end
  • Mixer
  • 5 GHz
  • Integrated circuit
  • LNA
  • ISM
  • SiGe
  • RFIC
  • U-NII
  • Sub-harmonic
Date of Defense 2001-04-12
Availability unrestricted
Abstract
In 1997 the Federal Communications Commission (FCC) released 300 MHz of

spectrum between 5-6 GHz designated the unlicensed national information

infrastructure (U-NII) band. The intention of the FCC was to provide an

unlicensed band of frequencies that would enable high-speed wireless

local area networks (WLANs) and facilitate wireless access to the

national information infrastructure with a minimum interference to other

devices. Currently, there is a lack of cost-effective technologies for

developing U-NII band components. With the commercial market placing

emphasis on low cost, low power, and highly integrated implementations

of RF circuitry, alternatives to the large and expensive distributed

element components historically used at these frequencies are needed.

Silicon Germanium (SiGe) BiCMOS technology represents one possible

solution to this problem. The SiGe BiCMOS process has the potential for

low cost since it leverages mature Si process technologies and can use

existing Si fabrication infrastructure. In addition, SiGe BiCMOS

processes offer excellent high frequency performance through the use of

SiGe heterojunction bipolar transistors (HBTs), while coexisting Si CMOS

offers compatibility with digital circuitry for high level

'system-on-a-chip' integration.

The work presented in this thesis focuses on the development of a SiGe

RFIC front-end for operation in the U-NII bands. Specifically, three

variants of a packaged low noise amplifier (LNA) and a packaged active

x2 sub-harmonic mixer (SHM) have been designed, simulated and measured.

The fabrication of the Rifts was through the IBM SiGe foundry; the

packaging was performed by RF Micro devices. The mixer and LNA designs

were fabricated on separate die, packaged individually, and on-chip

matched to a 50 ohm system so they could be fully characterized.

Measurements were facilitated in a coaxial system using standard FR4

printed circuit boards.

The LNA designs use a single stage, cascoded topology. The input ports

are impedance matched using inductive emitter degeneration through

bondwires to ground. One version of the LNA uses an shunt

inductor/series capacitor output match while the other two variation use

a series inductor output match. Gain, isolation, match, linearity and

noise figure (NF) were used to characterize the performance of the LNAs

in the 5 - 6 GHz frequency band. The best LNA design has a maximum gain

of 9 dB, an input VSWR between 1.6:1 and 2:1, an output match between

1.7:1 and 3.6:1, a NF better than 3.9 dB and an input intercept point

(IIP3) greater than 5.4 dBm. The LNA operates from a 3.3 V supply

voltage and consumes 4 mA of current.

The SHM is an active, double-balance mixer that achieves x2 sub-harmonic

mixing through two quadrature (I/Q) driven, stacked Gilbert-cell

switching stages. Single-ended-to-differential conversion, buffering

and I/Q phase separation of the LO signal are integrated on-chip.

Measurements were performed to find the optimal operating range for the

mixer, and the mixer was characterized under these sets of conditions.

It was found that the optimal performance of the mixer occurs at an IF

of 250-450 MHz and an LO power of -5 dBm. Under these conditions, the

mixer has a measured conversion gain of 9.3 dB, a P_1-dB of -15.7 dBm

and an 2LO/RF isolation greater than 35 dB at 5.25 GHz. At 5.775 GHz,

the conversion gain is 7.7 dB, the P_1-dB is -15.0 dBm, and the

isolation is greater than 35 dB. The mixer core consumes 9.5 mA from a

5.0 V supply voltage.

This work is sponsored by RF Microdevices (RFMD)through the CWT a liate

program.The author was supported under a Bradley Foundation fellowship.

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