Telecommunications – Transmitter and receiver at same station – With frequency stabilization
Reexamination Certificate
1999-11-04
2003-09-16
Vo, Nguyen T. (Department: 2685)
Telecommunications
Transmitter and receiver at same station
With frequency stabilization
C455S118000
Reexamination Certificate
active
06622009
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to radiotelephone transmitter/receivers and in particular, but not exclusively it relates to transmitter tracking loops for radiotelephones.
2. Description of the Related Art
Reference is made to the following papers for technological background material relating to the invention:
“Recent Advances in RF Integrated Circuits” by Behzad Razavi published in IEEE Communications Magazine December 1997.
“Oversampling and sigma-delta strategies for data conversion” by R. W. Stewart and E. Pfann published in Electronics & Communication Engineering Journal February 1998.
“An Agile ISM (Industrial, Scientific and Medical use) Band Frequency Synthesizer with Built-In GMSK Modulation” by Norman M. Filiol, Thomas A. D. Riley, Calvin Plett and Miles A. Copeland published in IEEE Journal of Solid-State circuits, Vol 33, no. 7 July 1998.
UK patent application GB 2 320 629 A.
It is now a common practice to make use of a tracking loop architecture for mobile phones for operation with GSM (Global System for Mobile communications, formerly Groupe Special Mobile). This tracking loop architecture uses a Voltage controlled oscillator (VCO) operating at the required transmission frequency to provide the output carrier frequency i.e. an “on-channel” transmitter. The transmitter VCO is phase locked and within the loop bandwidth of this VCO the modulated data passes. Through the process of down conversion and phase detection, the modulation on the output of the VCO is-compared with the original (desired) modulation. The negative feedback thereby implemented provides for accurate reproduction of the modulation at radio frequency.
Fabrication of this type of system requires a significant area of RF silicon for the down converter, high frequency phase detector and quadrature modulator. Owing to the low yield and the quantity of wafers used for implementation of circuits in RF Silicon, costs for RF Silicon are relatively high when compared with standard CMOS circuitry. For this reason it is desirable to implement such a modulation loop but using only CMOS technology and so allowing for integration with the base band circuitry.
SUMMARY OF THE INVENTION
It is therefore an object of the present invention to provide a radiotelephone transmitter/receiver reducing its cost and size.
According to the invention a part of the output signal from the voltage control oscillator is down-converted by the down-converting means. The down-converted signal is compared with a modulation signal by the phase detector. The signal has amplitude and polarity based on the comparison effected between the down-converted signal and the modulation signal is provided to the voltage control oscillator. The voltage control oscillator outputs a signal has frequency based on the applied signal.
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Behzad Razavi, “Recent Advances in RF Integrated Circuits”,IEEE Communications Magazine, Dec. 1997, pp. 36-43.
R. W. Stewart et al., “Oversampling and sigma-delta strategies for data conversion”,Electronics & Communication Engineering Journal, Feb. 1998, pp. 37-47.
Norman M. Filiol et al., “An Agile ISM Band Frequency Synthesizer with Built-In GMSK Data Modulation”,IEEE Journal of Solid-State Circuits, vol. 33, No. 7, Jul. 1998, pp. 998-1008.
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