Miscellaneous active electrical nonlinear devices – circuits – and – Specific identifiable device – circuit – or system – Unwanted signal suppression
Reexamination Certificate
1999-07-06
2001-11-27
Kim, Jung Ho (Department: 2816)
Miscellaneous active electrical nonlinear devices, circuits, and
Specific identifiable device, circuit, or system
Unwanted signal suppression
C359S199200
Reexamination Certificate
active
06323726
ABSTRACT:
BACKGROUND OF THE INVENTION
The invention concerns a diode network having at least one diode, which in operation is located in the path of a high-frequency signal, a predetermined diode voltage being applied to the diode to adjust its operating point.
To adjust the operating point of a diode in a signal-influencing network, current injection on the one hand and voltage injection on the other hand is known. An arrangement with current injection is shown in FIG. 2 of U.S. Pat. No. 5,210,633. In such an arrangement, the DC voltage applied to the diode varies in accordance with fluctuations in the level of the signal passed by the diode, which can be a high-frequency signal. In this known arrangement, if the diode network involves a predistorter circuit for linearising the output signal of an optical modulator, then the operating point can only be optimised for a single value of the amplitude of the high-frequency signal. Therefore, in the known arrangement, for optimum linearisation of the characteristic it is necessary to correct the current sources according to the amplitudes of the input signal.
Furthermore, U.S. Pat. No. 5,161,044, FIG. 15, discloses a diode network of the type initially described for linearising the output signal of an external optical modulator, by which the light leaving a light source is modulated. Here the terminals of two diodes in an inverse-parallel connection in the signal path of the signal to be influenced, are connected to voltage sources via inductors having a low ohmic resistance. The inductors are used to decouple the signal path from the voltage sources. A disadvantage of such an arrangement is that the inductors have stray capacitances, so that complete decoupling of the signal path from the voltage sources is not possible.
SUMMARY OF THE INVENTION
The object of the invention is to create a voltage injection for an arrangement of the type initially described, in which the use of inductors is unnecessary for the decoupling of the voltage source from the diode.
This object is achieved in that a control device is provided to maintain the diode voltage constant.
With the invention it is advantageous that, due to the measurement of the DC voltage acting on the diode itself and influencing the operating point, it is not necessary to provide a low-resistance coupling between a voltage source and the diode, with respect to direct current. Rather, the source of electrical energy being used for adjusting the operating point of the diode can be coupled to the diode via a low-inductance resistor, dimensioned so that it provides adequate decoupling for high frequency. The control device ensures that, despite this resistor, constant voltage ultimately appears at the diode, even with fluctuations of the signal conducted through the diode.
An exemplary embodiment of the invention provides for the control device to be realised by means of operational amplifiers.
REFERENCES:
patent: 5161044 (1992-11-01), Nazarathy et al.
patent: 5210633 (1993-05-01), Trisno
patent: 5327279 (1994-07-01), Farina et al.
patent: 5378937 (1995-01-01), Heidemann et al.
patent: 5963352 (1999-10-01), Atlas et al.
patent: 30 29 105 A1 (1981-02-01), None
patent: 42 40 714 A1 (1993-07-01), None
patent: WO97/35390 (1997-09-01), None
Berger Werner
Braun Klaus
Alcatel
Kim Jung Ho
Sughrue Mion Zinn Macpeak & Seas, PLLC
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