Trim effect compensation circuit
Inactive Publication Date: 2003-05-22
CTS CORP ELKHART
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Benefits of technology
[0012] A further feature of the invention is to provide an oscillator assembly that includes a voltage controlled crystal oscillator that produces a stable reference frequency. The voltage controlled crystal oscillator has a terminal connected to an electronic frequency adjust voltage. A temperature compensation circuit is in communication with the voltage controlled crystal oscillator. The temperature compensation circuit is adapted to provide a temperature compensation voltage to the voltage controlled crystal oscillator. The temperature compensation voltage allows the voltage controlled crystal oscillator to maintain the stable reference frequency as the temperature around the oscillator assembly varies. A trim effect compensation circuit is connected between the temperature compensation circuit and the terminal. The trim effect compensation circuit is adapted to adjust the temperature compensation voltage in response to a change in the electronic frequency adjust voltage.
Problems solved by technology
When the EFA voltage is changed, however, the pulling sensitivity of the circuit is also affected.
This means that the exact same temperature compensating voltage from the network will have a slightly different effect on the frequency over temperature, resulting in a rotation of the temperature versus frequency curve which degrades the temperature error.
The further the frequency has been adjusted or pulled, the greater the magnitude of the error.
This error that results after trimming the frequency back to nominal to compensate for aging has become known as the "Trim Effect Error."
Trim effect error has always been a problem with TCXO's.
Although there are some circuit configurations and techniques which can minimize the effect, there is no way to avoid the problem.
With some telecom systems requiring compensation to a level of better than +0.3 ppm to achieve Stratum 3 holdover requirements, the trim effect is a limitation in these types of TCXO applications.
Method used
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[0011] It is a feature of the invention to provide an oscillator that has a trim effect compensation circuit.
[0012] A further feature of the invention is to provide an oscillator assembly that includes a voltage controlled crystal oscillator that produces a stable reference frequency. The voltage controlled crystal oscillator has a terminal connected to an electronic frequency adjust voltage. A temperature compensation circuit is in communication with the voltage controlled crystal oscillator. The temperature compensation circuit is adapted to provide a temperature compensation voltage to the voltage controlled crystal oscillator. The temperature compensation voltage allows the voltage controlled crystal oscillator to maintain the stable reference frequency as the temperature around the oscillator assembly varies. A trim effect compensation circuit is connected between the temperature compensation circuit and the terminal. The trim effect compensation circuit is adapted to adjust t...
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An oscillator assembly has a voltage controlled crystal oscillator that produces a stable reference frequency. The voltage controlled crystal oscillator is connected to an electronic frequency adjust voltage. A temperature compensation circuit is connected to the voltage controlled crystal oscillator. The temperature compensation circuit provides a temperature compensation voltage to the voltage controlled crystal oscillator. A trim effect compensation circuit is connected between the temperature compensation circuit and the electronic frequency adjust voltage. The trim effect compensation circuit adjusts the temperature compensation voltage in response to a change in the electronic frequency adjust voltage.
Description
[0001] This application is related to U.S. patent application Ser. No. 09 / 335,245, filed Jun. 17, 1999, and titled, "Temperature Compensating Circuit for a Crystal Oscillator". The contents of which are herein incorporated by reference in entirety.[0002] 1. Field of the Invention[0003] This invention relates to an oscillator that provides a stable reference frequency signal in electronic equipment. Specifically, there is an oscillator that has a trim effect compensation circuit to compensate for error in the frequency versus temperature curve which results when a temperature compensated crystal oscillator is adjusted or trimmed to correct for frequency drift due to aging.[0004] 2. Description of Related Art[0005] Temperature Compensated Crystal Oscillators (TCXO's) which employ thermistor / resistor networks have been in existence for some 45 years. These networks operate on the principle of producing a precisely calibrated, temperature varying correction voltage. When this voltage is...
Claims
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Login to View More IPC IPC(8): H03B5/36
CPCH03B5/368H03B5/366
InventorFRY, STEVEN J.CARLISLE, RAYMOND M.
OwnerCTS CORP ELKHART