Miscellaneous active electrical nonlinear devices – circuits – and – External effect – Temperature
Reexamination Certificate
1999-07-13
2001-10-09
Kim, Jung Ho (Department: 2816)
Miscellaneous active electrical nonlinear devices, circuits, and
External effect
Temperature
C327S306000
Reexamination Certificate
active
06300817
ABSTRACT:
BACKGROUND OF THE INVENTION
The invention relates to a circuit to reduce the temperature-dependence of a predistorter diode in a predistorter for an external optical modulator. Either current or voltage impression can be used to adjust the operating point of a diode in a signal-influencing network.
U.S. Pat. No. 5,210,633, FIG. 2 shows an arrangement with current impression. In this type of arrangement the dc voltage at the diode changes as a function of the level fluctuations of the signal let through by the diode, which can be a high-frequency signal. With this familiar arrangement, the operating point for a signal amplitude value of the high-frequency signal can be optimally adjusted if the diode network is a predistorter to linearize the output signal of an optical modulator. Thus, the current source has to be tracked according to the amplitude of the input signal for an optimal linearization of the curve in this familiar arrangement.
U.S. Pat. No. 5,161,044, FIG. 15 shows a diode network to linearize the output signal of an external optical modulator, which is linearized by a light from a light source. The diodes here are connected to voltage sources. Since these are semiconductor diodes, the current-voltage curve is temperature-dependent. The operating point of the diode thus changes with no particular measure when the temperature changes. It is already known that the voltage of predistorter diodes can be tracked using a computer according to a temperature table, whereby a temperature sensor and an A/D converter as well as D/A converter are required. However, this entails a lot of work and equipment.
It is also state-of-the-art to solve the problem by keeping the predistorter diodes at a constant temperature, for example using Peltier cooling.
SUMMARY OF THE INVENTION
The invention is based on reducing the influence of the temperature-dependence of the operating point of a predistorter diode.
This problem is solved in accordance with the invention by connecting the predistorter diode in series with an ohmic resistance and feeding the series circuit from a power supply during operation, whereby the voltage of the power supply and the ohmic resistance are selected such that when the temperature of the predistorter changes the curvature of the temperature-dependent current-voltage curve for the predistorter diode hardly varies, if at all, at the respective operating point.
One advantage of the invention is the very simple type of compensation which the invention enables. The simplest solution is to connect a resistance before the predistorter diode, whereby the series circuit of the resistance and predistorter diode has a constant voltage. The resistance should be dimensioned (e.g. through tests) to achieve the desired temperature compensation. It is important that the curvature of the curve in the respective operating point is essentially the same. This curvature is important for the generation of harmonics and thus for the distorting properties of the predistorter diode. It may be advantageous to keep the slope of the curve as constant as possible in every operating point.
A further advantage is that even if the operating point of the predistorter diode has been stabilised against temperature-dependence by another method, the measure in accordance with the invention still reduces or fully compensates the remaining changes in the curvature of the curve of the predistorter diode in the respective operating point during temperature fluctuations.
In one embodiment of the invention the voltage at a reference diode which is thermally coupled to the predistorter diode is impressed on the predistorter diode as a power supply. This means that one reference diode is adequate for two branches of a signal path.
Since the predistorter diodes under consideration are semiconductor diodes and the diode current rises with a rising temperature at a constant voltage, the invention can be used with no problems.
REFERENCES:
patent: 5161044 (1992-11-01), Nazarathy et al.
patent: 5210633 (1993-05-01), Trisno
patent: 5302922 (1994-04-01), Heidemann et al.
patent: 5327279 (1994-07-01), Farina et al.
patent: 5378937 (1995-01-01), Heidemann et al.
patent: WO 94/02998 (1994-02-01), None
patent: WO 97/35390 (1997-09-01), None
Berger Werner
Braun Klaus
Alcatel
Kim Jung Ho
Sughrue Mion Zinn Macpeak & Seas, PLLC
LandOfFree
Temperature stabilization of a predistorter does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Temperature stabilization of a predistorter, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Temperature stabilization of a predistorter will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2562229