Telecommunications – Transmitter and receiver at same station – With frequency stabilization
Patent
1998-02-20
1999-01-26
Chin, Wellington
Telecommunications
Transmitter and receiver at same station
With frequency stabilization
455264, 455256, H04Q 732
Patent
active
058647490
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The present invention relates to a telecommunications subscriber unit, and in particular to a mobile telephone.
In modern digitally operated mobile telephones and similar subscriber units, the temperature response to which even a voltage-controlled quartz oscillator is subject makes itself evident in disadvantageous fashion if, for example, the utilization location is shifted within a short time from indoors to outdoors during the winter.
The invention differs from the known subscriber units by means of the features of the characterizing portion of claim 1.
Digitally temperature-compensated quartz oscillators for a frequency range of up to 25 MHz are generally known. Here the oscillating crystal and a microprocessor are surrounded, together with a control circuit to generate the correction voltage, by a common housing. Such quartz oscillator is very complex, and its use in telecommunications subscriber units, the demand for which is now very high, is therefore subject to considerable drawback.
SUMMARY OF THE INVENTION
A telecommunications unit according to the present invention includes an oscillator circuit whose frequency standard device has a temperature response. The telecommunications unit also includes a programmed microprocessor for controlling the execution of the unit functions, which is activated by a start instruction given from outside. The telecommunications unit has a temperature sensor arranged in the close vicinity of the frequency standard device. The microprocessor is configured so that correction magnitudes for slaving the frequency of the frequency standard are stored in a memory element of the microprocessor. An instruction sequence for interrogating the instantaneous resistance value of the temperature sensor, which can be called prior to execution of the unit functions dependent on the frequency standard, is inserted in the program of the microprocessor. A correction voltage for the frequency standard device corresponding to the instantaneous resistance value of the temperature sensor can be determined from the correction magnitude values. In addition, the present invention guarantees an extremely low energy consumption in the additional circuit for compensating for the temperature response of the oscillating crystal.
BRIEF DESCRIPTION OF THE DRAWINGS
The FIGURE show a block diagram of a telecommunications subscriber unit according to the present invention.
DETAILED DESCRIPTION OF THE INVENTION
Operation of the telecommunications subscriber unit is controlled by a microprocessor 1. In telecommunications units, microprocessor 1 is usually restarted at each communication request, and in the interim remains in a "standby" mode so as not to put unnecessary load on the battery capacity.
Inserted into the program of microprocessor 1 is an instruction sequence which is started at each activation of the unit prior to executing of the device functions which depend on the frequency standard. As soon as microprocessor 1 is activated, whether by the push of a button prior to an outgoing call or by an incoming call signal, the instruction sequence evaluates the instantaneous resistance value of an NTC resistor 2 which is arranged in the housing of the subscriber unit in the close vicinity of an oscillator crystal 3.0.1 .mu.F capacitor 4 is arranged parallel to NTC resistor 2. The top end of NTC resistor 2 is connected via a 47-kOhm resistor 5 to battery voltage U.sub.B, which for has a voltage example 2.5 V. The resistance value of NTC resistor 2 is received up by an internal A/D converter 6. The correction magnitudes needed to control the frequency of oscillator crystal 3 as a function of the temperature measured by NTC resistor 2 are stored in a memory element 7 in microprocessor 1. The correction value determined by computer 8 in microprocessor 1 is converted, in an internal D/A converter 9 in microprocessor 1, into a voltage value which controls a variable-capacitance diode 10 that is connected at the top end of oscillator crystal 3. Oscillator crystal 3 oscil
REFERENCES:
patent: 5548252 (1996-08-01), Watanabe et al.
patent: 5731742 (1998-03-01), Wojewoda et al.
Chin Wellington
Ferguson Keith
Robert & Bosch GmbH
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