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Liming Zhou
Advisor: Afshin S. Daryoush, Ph.D.
Abstract:
Future generations of wide-band wireless communication systems utilize the spatial diversity and polarization diversity with broadband digital receivers to improve information capacity for the provided spectrum. This thesis addresses the generation of multiple beam patterns and polarization forms by taking advantages of both front-end beam polarization control and back-end multi-beam generation. The polarization diversity is implemented using broadband RF hardware at the front-end, where two orthogonally polarized waves are demonstrated.
More specifically, the design, realization, and test results of two 2.45GHz digital direct conversion receivers are reported in this thesis. The first unit is a hybrid realization using commercial discrete off-the-shelf components for a half-duplex communication over a 100m range. The transceiver board was designed to have a gain of 23dB, an output 1dB compression point (OP1dB) of 18dBm, and an output third order inception point (OIP3) of 28dBm in the transmit state, while the measure performance of an assembled board shows a gain of 19dB, an OP1dB of 10dB, and an OIP3 of 23dBm. Its receive state has was designed for a gain of 54dB, a noise figure (NF) of 4.4dB, an input 1dB compression point (IP1dB) of -32dBm and input third order interception point (IIP3) of -13dBm. The measured receive state of this board has a gain of 49dB, a NF of 6.3dB, an IP1dB of -29dBm and an IIP3 of -13dBm. The measured SFDR and CDR for the receiver are 54dB and 66dB respectively compared to the designed level. This robustness of this unit is demonstrated in a prototype 4x4 MIMO configuration with10MHz of bandwidth at 2.45GHz carrier frequency.
The hybrid transceiver design experience was extended to a broadband integrated circuit (IC) digital receiver using a commercial (Knowledge*On) InGaP/GaAs HBT technology with fT = 65GHz. A 2.45GHz LNA and double balanced Gilbert Cell mixer are designed and realized, as an effort to create a full duplex transceiver. The LNA has a 2-stage internally match 2-stage common emitter design with 100 MHz bandwidth. It has a gain of 23dB with flatness of ±0.5dB over 180 MHz, a NF of 2.4dB with flatness of ±0.1dB over 200MHz, an output P1dB of -0.7dBm and an OIP3 of 9.8dBm. The down-conversion mixer is a double balanced Gilbert-cell core with differential input and output signal format. A conversion gain of 11.5dB, a NF of 13.1dB, IP1dB of -6.0dBm and an IIP3 of 6.6dBm are measured for a frequency band over 800MHz. Both the LNA and mixer perform closely matches up with the simulation performed on the designed circuits using nonlinear VBIC parameters of the HBT except for minor differences from the designed VSWR.
The developed IC based digital receiver is applied to a novel reconfigurable direct conversion receiver structure. The digital receiver is fully reconfigurable for the reception of spatial and polarization diversified signals. When operated with a dual polarized antenna, the dual circular polarized (CP) waves and two other dual linear polarized (LP) combinations may be formed by taking advantage of passive switches and digitally- or analog-controlled phase shifters in the local oscillator path. A polarization rejection of 14dB for an observing bandwidth of 500MHz at 2.45GHz is observed on a discrete FR-4 based test setup without optimization. The proposed receiver structure is also capable of creating a steering antenna beam in conjunction with the polarization tuning circuit with a multiple receiver antenna array with analog phase shifters. This additional function does not burden the already power hungry digital signal processors. In fact a combination of the front-end polarization diversity rejection of 14dB along with the back-end multi-beamforming network provides an efficient tool against jamming signals in the field regardless of its location, while reducing the computational power of the back-end digital signal processors.
Monday, March 19th, 2007 at 1:30 p.m.
Bossone 303
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