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To investigate theoretically and experimentally(I) The injection locking properties of HBT Active Antenna Transmitters(ii) To exploit injection locking for direct phase modulationProgress:A suitable large-signal model [1] of an H.B.T. device, based on the Gummel-Poon model has been implemented which incorporates thermally induced gain compression effects which are seen in H.B.T. devices. Work is now being carried out to fit this model to a AlGaS H.B.T. device (supplied under collaboration agreement with GECMarconi Materials Technology Ltd). This involves d.c., small signal and large signal device measurement and a special purpose large signal test jig has been designed for this purpose. An oscillator synthesis procedure has been implemented using HP Microwave Development Software. Also implemented in M.D.S. are harmonic balance and time domain based procedures to verify that the oscillator design will startup and operate in a stable limit cycle. These procedures allow the investigation of the oscillator circuit in both free-running and injection locked (using fundamental and sub-harmonic frequencies) for the injection locking and voltage controlled oscillator (V.C.O.) properties of the circuit has also been investigated using known large signal NE71000FET large signal models in order to justify the design philosophy.Theoretical studies of injecting the oscillator with two injection locking signals, one at the fundamental frequency of the oscillator, the other close to the first sub-harmonic have been carried out via simulation (a large signal model of a B.J.T. device was used as the active device). The aim of this experiment is to replicate the procedure described in [2] which allows the up-conversion efficiency for sub-harmonic locking to be established.A simple mixing theory has been developed in order to explain the theoretical results obtained during the above procedure. References[1] Correra, F.S., Tadayon, S., A modified Gummel-Poon model applied to HBTs , 23rd European Microwave Conference, 1993, pp 96-98.[2] Zhang, X., Zhou, X., Aliender, B., Daryoush, A.S., A Study of Subharmonic Injection Locking for Local Oscillators , IEEE Microwave and Guided Letters, Vol.2, No.3, March 1992.Related Publications1. Fusco, V.F., Drew, S., Active Antenna Phase Modulator Performance, 23rd European Microwave Conference, ISBN 0-946821-23-2, pp 248-251, September 1993.2. Fusco, V.F., Drew, S., McDowall, S.D., Synthesis and Performance of an Active Microstrip Antenna, Special Issue CAD of Printed Antennas and Arrays, International Journal of Microwave and Millimetric Wave Computer Aided Engineering, Vol.4, No.1, pp 100-110, January 1994.3. Fusco, V.F., Sancheti, S., Drew, S., Humphrey, D., Active Antenna Element Design Issues, IEE Colloquium on Smart Antennas, Digest No.1944/182, pp 9/1-9/7, December 1994.
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