Radio frequency bus leveling system

• US 5,546,050 A
• Filed: 03/14/1995
• Issued: 08/13/1996
• Est. Priority Date: 03/14/1995
• Status: Expired due to Fees

• Current Assignee: The Boeing Co.
• Original Assignee: The Boeing Co.
• Inventors: Florian, Michael H., Hogue, David R., Redd, Harold J., Bonebright, Rodney K.
• Primary Examiner(s): Mullins, James B.
• Application Number:
  US08/403,408
• Time in Patent Office: 518 Days
• Field of Search: 330/52, 330/86, 330/132, 330/282
• US Class Current: 330/282
• CPC Class Codes: H03G 1/0058 PIN-diodes
• CPC Class Codes: H03G 3/3036 in high-frequency amplifiers or in frequency-changers H03G3/3052, H03G3/32, H03G3/34 take precedence

Abstract

A bus leveling system for automatically monitoring and maintaining the amplitude of a radio frequency (RF) signal carded on a bus. A two-stage variable gain amplifier (64) is connected in series with the bus. Each stage of the variable gain amplifier is constructed with a PIN diode (84, 86) in a feedback path of the stage. The amplification of the variable gain amplifier is varied by the injection of current into the feedback path to adjust the resistance of the PIN diodes. A control circuit having an RE detector (78) is provided to monitor and adjust the gain generated by the variable gain amplifier. Preferably, the control circuit and the variable gain amplifier are incorporated into an Application Specific Integrated Circuit (ASIC) (62). The RF detector is constructed of two Gilbert multipliers (202, 204) to minimize errors caused by operating condition changes, including variations in power supply voltage, temperature, or process.

Claims

1. A system for maintaining the amplitude of a signal carded on a bus, the signal including at least one carder modulated with data and a component indicative of the amplitude of the signal, the system comprising:

(a) a variable gain amplifier having an input and an output that are connected in series with the bus, the variable gain amplifier comprising an amplifier, a PIN diode connected in a feedback path from the output of the amplifier to the input of the amplifier, and a control input coupled to the feedback path, wherein a control signal provided to the control input varies the resistance of the PIN diode to adjust the gain produced by the variable gain amplifier;

(b) a filter coupled to the output of the variable gain amplifier for filtering the signal carried on the bus to isolate the component of the signal that is indicative of the amplitude of the signal;

(c) a voltage reference for producing a reference voltage level; and

(d) a detector coupled to the filter and to the control input of the variable gain amplifier for comparing the amplitude of the component of the signal with the reference voltage level and providing a control signal to the control input of the variable gain amplifier to bring the amplitude of the component equal to the reference voltage level, the detector comprising;

(i) a first multiplier coupled to the filter for receiving the component of the signal indicative of the amplitude of the signal and generating a load current proportional to the amplitude of the component;

(ii) a second multiplier coupled to the voltage reference for generating a reference current proportional to the reference voltage level; and

(iii) a current comparator coupled to the first and second multipliers for comparing the load current with the reference current and producing a control signal proportional to the difference between the load current and the reference current.

2. The system of claim 1, wherein the amplifier, the voltage reference, and the detector are incorporated into an Application Specific Integrated Circuit (ASIC).

3. The system of claim 2, wherein the voltage reference is a bandgap reference.

4. The system of claim 3, further comprising a PIN driver coupled between the detector and the variable gain amplifier for receiving the control signal generated by the detector and amplifying the control signal to provide sufficient current to vary the resistance of the PIN diode and adjust the gain produced by the variable gain amplifier.

5. The system of claim 4, wherein the variable gain amplifier further composes a second amplifier having a PIN diode connected in a feedback path from the output of the second amplifier to the input of the second amplifier, and a control input coupled to the feedback path such that a control signal applied to the control input varies the resistance of the PIN diode to adjust the gain of the variable gain amplifier.

6. The system of claim 5, wherein the PIN driver provides a second control signal to the second amplifier to vary the resistance of the PIN diode in the feedback path of the second amplifier in order to adjust the gain produced by the variable gain amplifier.

7. The system of claim 6, further comprising a buffer coupled between the output of the variable gain amplifier and the filter.

8. The system of claim 7, further comprising a resistor network coupled between the buffer and the filter for attenuating the signal to a desired level.

9. The system of claim 1, wherein the signal is a radio frequency signal.

10. The system of claim 9, wherein the component indicative of the amplitude of the signal is a pilot tone.

11. The system of claim 1, wherein the first and second multipliers are Gilbert multipliers.

12. The system of claim 1, further comprising a buffer coupled to the output of the variable gain amplifier, the buffer providing an active tap of the signal carded on the bus.

13. A system for maintaining the amplitude of a signal carded on a bus, the signal including at least one carder modulated with data and a pilot tone indicative of the amplitude of the signal, the system comprising:

(a) a variable gain amplifier having an input and an output that are connected in series with the bus, and a control input, a gain produced by the variable gain amplifier adjusted in response to a control signal provided to the control input;

(b) a filter coupled to the output of the variable gain amplifier for filtering the signal carded on the bus to isolate a pilot tone from the signal;

(c) a voltage reference for producing a reference voltage; and

(d) a detector coupled to the filter, the voltage reference and the control input of the variable gain amplifier, the detector comprising;

(i) a first Gilbert multiplier coupled to the filter for receiving the pilot tone and generating a load current proportional to the amplitude of the pilot tone;

(ii) a second Gilbert multiplier coupled to the voltage reference for generating a reference current proportional to the reference voltage level; and

(iii) a current comparator coupled to the first and second Gilbert multipliers for comparing the load current with the reference current, producing a control signal proportional to the difference between the load current and the reference current, and providing the control signal to the control input of the variable gain amplifier in order to adjust the gain of the variable gain amplifier so that the pilot tone is maintained at a desired amplitude.

14. The system of claim 13, wherein the variable gain amplifier comprises:

(a) an amplifier having an input and an output; and

(b) a PIN diode connected in a feedback path from the output of the amplifier to the input of the amplifier, wherein the control input of the variable gain amplifier is coupled to the feedback path so that a control signal received on the control input varies the resistance of the PIN diode.

15. The system of claim 14, wherein the amplifier and the detector are incorporated into an Application Specific Integrated Circuit (ASIC).

16. The system of claim 15, wherein the voltage reference is a bandgap reference.

17. The system of claim 14, further comprising a PIN driver coupled between the detector and the variable gain amplifier, said PIN driver receiving the control signal generated by the detector and amplifying the control signal to provide sufficient current to vary the resistance of the PIN diode and adjust a gain produced by the variable gain amplifier.

18. The system of claim 17, wherein the variable gain amplifier further comprises a second amplifier having a PIN diode connected in a feedback path from an output of the second amplifier to an input of the second amplifier, and a control input coupled to the feedback path such that a control signal applied to the control input varies the resistance of the PIN diode to adjust the gain of the variable gain amplifier.

19. The system of claim 18, wherein the PIN driver provides a second control signal to the second amplifier to vary the resistance of the PIN diode in the feedback path of the second amplifier in order to adjust the gain produced by the variable gain amplifier.

20. The system of claim 19, further comprising a buffer coupled between the output of the variable gain amplifier and the filter.

21. The system of claim 20, further comprising a resistor network coupled between the buffer and the filter for attenuating the signal to a desired level.

22. The system of claim 17, wherein the amplifier, the voltage reference, the detector, and the PIN driver are incorporated into an Application Specific Integrated Circuit (ASIC).

23. The system of claim 13, wherein the signal is a radio frequency signal.

24. The system of claim 13, further comprising a buffer coupled to the output of the variable gain amplifier, the buffer providing an active tap of the signal carried on the bus.

25. A system for maintaining the amplitude of a signal carded on a bus, the signal including at least one carrier modulated with data and a component indicative of the amplitude of the signal, the system comprising:

(a) a PIN diode; and

(b) a leveler incorporated in an Application Specific Integrated Circuit (ASIC) comprising;

(i) a variable gain amplifier having an input and an output that are connected in series with the bus, the variable gain amplifier comprising an amplifier with the PIN diode connected in a feedback path from the output of the amplifier to the input of the amplifier, and a control input coupled to the feedback path, wherein a control signal provided to the control input varies the resistance of the PIN diode to adjust the gain produced by the variable gain amplifier;

(ii) a voltage reference for producing a reference voltage level; and

(iii) a control circuit coupled to the output of the variable gain amplifier, the voltage reference, and the control input of the feedback path, the control circuit comparing the amplitude of a component of the signal carried on the bus with the reference voltage level and adjusting the gain of the variable gain amplifier to maintain the component of the signal at a desired amplitude.

26. The system of claim 25, further comprising a filter coupled to the output of the variable gain amplifier for filtering the signal carried on the bus to isolate the component of the signal that is indicative of the amplitude of the signal.

27. The system of claim 26, wherein the control circuit comprises a detector coupled to the filter and to the control input of the variable gain amplifier for comparing the amplitude of the component:

of the signal with the reference voltage level and providing a control signal to the control input of the variable gain amplifier to bring the amplitude of the component equal to the reference voltage level.

28. The system of claim 27, wherein the voltage reference is a bandgap reference.

29. The system of claim 28, wherein the detector comprises:

(a) a first multiplier coupled to the filter for receiving the component of the signal indicative of the amplitude of the signal and generating a load current proportional to the amplitude of the component;

(b) a second multiplier coupled to the voltage reference for generating a reference current proportional to the reference voltage level; and

(c) a current comparator coupled to the first and second multipliers for comparing the load current with the reference current and producing a control signal proportional to the difference between the load current and the reference current.

30. The system of claim 29, wherein the first and second multipliers are Gilbert multipliers.

31. The system of claim 30, wherein the leveler further comprises a PIN driver coupled between the detector and the variable gain amplifier for receiving the control signal generated by the detector and amplifying the control signal to provide sufficient current to vary the resistance of the PIN diode and adjust the gain produced by the variable gain amplifier.

32. The system of claim 31, wherein the variable gain amplifier further comprises a second amplifier having a PIN diode connected in a feedback path from the output of the second amplifier to the input of the second amplifier, and a control input coupled to the feedback path such that a control signal applied to the control input varies the resistance of the PIN diode to adjust the gain of the variable gain amplifier.

33. The system of claim 32, wherein the PIN driver provides a second control signal to the second amplifier to vary the resistance of the PIN diode in the feedback path of the second amplifier in order to adjust the gain produced by the variable gain amplifier.