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Dissertation
Active antennas with an efficient multifunction self-oscillating mixer for wireless communications
Doctor of Philosophy (Ph.D.), Drexel University
Jun 1999
DOI:
https://doi.org/10.17918/00000774
Abstract
Personal communications services (PCS) systems employing low earth orbit (LEO) and medium earth orbit (MEO) satellites demand special antennas and transceiver circuits. Design and fabrication of active antennas with high performance transceiver front end electronics suitable for satellite and mobile communications are presented in this thesis. Design and fabrication of an efficient self-oscillating mixer (SOM) using matched pair Si BJTs is presented first. Methods to ensure high spectral purity (i.e., low FM noise) of the local oscillator (LO) are proposed and implemented. The transistors are characterized and their nonlinear parameters are extracted and optimized using a CAD tool. Both time-domain and frequency-domain simulations are performed to predict the performance of the circuit. As a prototype, a hybrid SOM is designed and fabricated. Measurements on the circuit demonstrate a stable LO signal at 560MHz with an output power level of 5dBm and a phase noise of -101dBc/Hz at 100kHz offset frequency. A 20dB up-conversion gain and a -2dB down-conversion gain is measured. Compression dynamic range (CDR) of 83dB. MHz and 100dB. MHz are also measured for the up- and down-converted mixer, respectively. Two-tone intermodulation distortion measurements indicate a third order intercept point (IP-3) of -2dBm for the case of up-conversion. The up-converted mixer gives a single side band (SSB) noise figure of 1.9dB. A quadrifilar helix antenna (QHA) is designed and fabricated for operation at UHF. A mathematical model for design implementation of the antenna in a commercial CAD tool has been developed. Using method of moments (MoM), radiation characteristics of the antenna in free space and above various ground planes are investigated. Methods to reduce multipath effect due to ground reflection on the antenna pattern are studied. Measurements on the QHA indicate a gain of 4.2dBi and an axial ratio less than 1dB over a wide beamwidth. The performance of the active antenna consisting of the SOM and the QHA was evaluated. When operated at higher frequencies, unique characteristics of the active antenna such as low power consuming, light weight, and efficiency make the structure attractive for many communication circuits both in handheld units and in T/R modules in phased array antennas.
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Details
- Title
- Active antennas with an efficient multifunction self-oscillating mixer for wireless communications
- Creators
- Manouchehr Ghanevati
- Contributors
- Afshin S. Daryoush (Advisor) - Drexel University, Electrical and Computer Engineering
- Awarding Institution
- Drexel University
- Degree Awarded
- Doctor of Philosophy (Ph.D.)
- Publisher
- Drexel University; Philadelphia, Pennsylvania
- Number of pages
- xxii, 171 pages
- Resource Type
- Dissertation
- Language
- English
- Academic Unit
- College of Engineering (1970-2026); Electrical (and Computer) Engineering [Historical]; Drexel University
- Other Identifier
- 991014970199804721