VARIABLE GAIN AMPLIFIER SYSTEM, PARTICULARLY FOR OPTICAL RECEIVER SYSTEMS

Abstract

The invention relates to a variable gain system, particularly for optical receiver systems, having: an input for an electronic signal, at least two variable gain amplifiers, and an output for an amplified electrical signal, wherein the at least two variable gain amplifiers are connected in parallel to the input and the output aggregates the signals of the at least two variable gain amplifiers.

Claims

1. Variable gain system, particularly for optical receiver systems, comprising: an input for an electronic signal, at least two variable gain amplifiers; and an output for an amplified electrical signal, wherein the at least two variable gain amplifiers are connected in parallel to the input and the output aggregates the signals of the at least two variable gain amplifiers.

2. Variable gain system according to claim 1, wherein the at least two variable gain amplifiers cover different portions of the gain range of the variable gain amplifier system.

3. Variable gain system according to claim 2, wherein the variable gain amplifier covering the lowest gain range of the variable gain amplifier system is directly connected to the output and wherein the other variable gain amplifiers covering higher gain ranges of the variable gain amplifier system are connected to the output by separate switches or wherein all variable gain amplifiers are connected to the output by separate switches.

4. Variable gain system according to claim 3, wherein the separate switches are operated by a control unit of the variable gain amplifier system based on the power of the electrical signal at the input or output of the variable gain amplifier system.

5. Variable gain system according to claim 1, wherein the at least two variable gain amplifiers are continuous variable gain amplifiers.

6. Variable gain system according to claim 1, wherein the electrical signal at the input is an analog electrical signal.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0019] FIG. 1 a first embodiment of a variable gain amplifier system according to the invention with two variable gain amplifiers, and

[0020] FIG. 2 a second embodiment of a variable gain amplifier system according to the invention with three variable gain amplifiers and a control unit.

DETAILED DESCRIPTION

[0021] FIG. 1 shows a first embodiment of a variable gain system 1, particularly for optical receiver systems. The variable gain system 1 of FIG. 1 comprises an input 2 for an electronic signal, two variable gain amplifiers 3, 4 and an output 5 for an amplified electrical signal. The two variable gain amplifiers 3, 4 are connected in parallel to the input 2. The output 5 aggregates the signals of the two variable gain amplifiers 3, 4.

[0022] The two variable gain amplifiers 3, 4 cover different portions of the gain range of the variable gain amplifier system 1. Thus, the two variable gain amplifiers amplify different parts of the signal at the input 2 of the variable gain system 1. The variable gain amplifier 4 covering the lowest gain range of the variable gain amplifier system 1 is directly connected to the output 5 and the other variable gain amplifier 3 covering higher gain ranges of the variable gain amplifier system 1 is connected to the output 5 by separate switches 6. If the signal at the input 2 of the variable gain system 1 has a high power level only variable gain amplifier 4 is connected to the output 5 and variable gain amplifier 3 is disconnected from the output 5 by switch 6. Since the variable gain amplifier 4 covers the lower gain range of the variable gain system 1 the amplification of signal at the input 2 is limited and a saturated output signal is avoided. If the power level of the signal at the input 2 of the variable gain system 1 is low the signal is amplified by variable gain amplifier 3 and variable gain amplifier 4 and thereby amplifying the input signal stronger.

[0023] The two variable gain amplifiers 3, 4 are continuous variable gain amplifiers and the electrical signal at the input 2 is an analog electrical signal.

[0024] Since the variable gain amplifiers 3, 4 are connected in parallel to the input 2 of the variable gain system 1 the noise and total harmonic distortion corresponds to a variable gain system with one variable gain amplifier.

[0025] FIG. 2 shows a second embodiment of a variable gain system 1, particularly for optical receiver systems. The variable gain system 1 of FIG. 2 comprises an input 2 for an electronic signal, three variable gain amplifiers 3, 4 and an output 5 for an amplified electrical signal. The three variable gain amplifiers 3, 4 are connected in parallel to the input 2. The output 5 aggregates the signals of the three variable gain amplifiers 3, 4.

[0026] The three variable gain amplifiers 3, 4 cover different portions of the gain range of the variable gain amplifier system 1. The variable gain amplifier 4 covering the lowest gain range of the variable gain amplifier system 1 is directly connected to the output 5. The other two variable gain amplifiers 3 covering higher gain ranges of the variable gain amplifier system 1 are connected to the output 5 by separate switches 6.

[0027] The separate switches 6 are operated by a control unit 7 of the variable gain amplifier system 1 based on the power of the electrical signal at the output 5 of the variable gain amplifier system 1. The control unit 7 monitors the power level of the electrical signal at the output 5 of the variable gain system 1 of FIG. 2, which is indicated in FIG. 2 by dashed line between the control unit 7 and the output 5. Depending on the power level of the electrical signal at the output 5 of the variable gain system 1 the control unit 7 connects the second and/or third variable gain amplifier 3 to the output 5 using switches 6. The switches 6 are operated by control unit 7, indicated in FIG. 2 by a dashed line between control unit 7 and switches 6.

[0028] If the signal at the output 5 of the variable gain system 1 has a high power level only variable gain amplifier 4 is connected to the output 5 and the other two variable gain amplifiers 3 are disconnected from the output 5 by switches 6. Since the variable gain amplifier 4 covers the lower gain range of the variable gain system 1 the amplification of signal at the input 2 is limited and a saturated output signal is avoided. If the power level of the signal at the output 5 of the variable gain system 1 decreases the control unit 7 can close one or both switches 6 to connect one of or both variable gain amplifiers 3 to the output 5. In this case the electrical signal at the input 2 is amplified by one or both additional variable gain amplifiers 3 and variable gain amplifier 4 and thereby amplifying the input signal stronger. By increasing the number of the additional variable gain amplifiers 3 the gain range of the variable gain system 1 is increased, but the noise and total harmonic distortion still corresponds to a variable gain system 1 with one variable gain amplifier.