Automatic RF leveling in passenger aircraft video distribution system

• US 5,220,419 A
• Filed: 04/08/1991
• Issued: 06/15/1993
• Est. Priority Date: 04/08/1991
• Status: Expired due to Fees

• Current Assignee: Rockwell International Corporation
• Original Assignee: Hughes Aircraft Company (Rtx Corporation)
• Inventors: Rabowsky, Irving, Sklar, Richard E.
• Primary Examiner(s): Eisenzopf, Reinhard J.
• Assistant Examiner(s): FAILE, ANDREW I
• Application Number:
  US07/681,850
• Time in Patent Office: 799 Days
• Field of Search: 455/3.1, 455/6.1, 455/6.2, 455/6.3, 455/14, 455/66, 455/67.1, 455/67.3, 455/234.1, 455/234.2, 455/240.1, 455/249.1, 455/253.2, 358/86, 375/98
• US Class Current: 725/76
• CPC Class Codes: H04H 20/62 for transportation systems, e.g. in vehicles

Abstract

A passenger aircraft video distribution system distributes modulated RF signals provided from a central signal source to be used at each passenger seat. The RF signals are distributed by means of various RF components, including amplifiers (90, 14a, 164, 24a, 24b, 34a), taps (180, 210) and splitters (108, 182, 214). In order to ensure proper RF levels for best tuner operation, each of a number of stations in the distribution system is provided with a variable gain amplifier (90, 14a, 164, 24a, 24b, 34a) controllable by a microprocessor (92, 50a, 220, 52a, 56a, 216). A separate service line (222, 224, 226, 228, 230, 232, 234) enables a central microprocessor to monitor RF levels at different stations to automatically provide, via the same service line, appropriate gain control signals to obtain proper RF levels. The monitored RF levels are also employed for diagnostic purposes.

Claims

1. An adjustable level signal transmission system comprising:

a chain of stations through which a signal is transmitted in sequence from one station to the next,

at least a group of said stations each including a variable gain amplifier connected to receive said signal transmitted from an upstream station and to transmit the received signal to the next downstream station in the chain,

at least some of said stations including means for tapping the signal for use at an individual station,

means for monitoring output signal levels of the amplifiers at at least some of the stations of said group, and

means responsive to the monitored signal levels for commanding variation of the gain of a first relatively upstream one of said amplifiers that is upstream from a second relatively downstream one of said amplifiers in response to occurrence of a monitored signal level at said downstream amplifier that is outside of a predetermined range of signal levels, at least a third relatively downstream amplifier having its gain varied by said means for commanding, and including means for compensating said third downstream amplifier for a commanded gain variation of said first upstream amplifier.

2. A passenger aircraft video distribution system comprising:

a passenger entertainment service controller station (PESC) having audio and video inputs and including means for processing said inputs to provide a transmitted output comprising a plurality of RF carriers having audio and video signals modulated thereon, said PESC station including a PESC variable gain amplifier connected to receive said inputs,

an area distribution box station (ADB) having a first ADB variable gain amplifier connected to receive the output of said PESC station, said area distribution box station comprising;

an ADB coupler responsive to said first ADB variable gain amplifier and providing a first output,

a second ADB variable gain amplifier connected to receive a signal from said coupler and to provide a transmitted ADB output signal comprising said carriers having said audio and video signals modulated thereon on, and

a line of interconnected video seat electronic box stations (VSEB), each having at least one tuner for manual operation by a passenger at the respective VSEB station, each of a group of said VSEB stations including a VSEB coupler responsive to said ADB output signal and providing a modulated RF carrier output transmitted to the next VSEB station in said line of VSEB stations, each said VSEB station of said group including a VSEB variable gain amplifier connected between said VSEB coupler and the tuner of the respective VSEB station,

each of said variable gain amplifiers including a monitoring terminal for providing a monitor signal indicative of the RF level of signal at the output of the respective variable gain amplifier, and

means responsive to the monitoring terminal of one of said ADB and VSEB variable gain amplifiers for controlling the gain of the variable gain amplifier of at least one station upstream from said one of said ADB and VSEB amplifiers to thereby adjust the RF signal level at the output of said one VSEB or ADB amplifier.

3. The system of claim 2 wherein each of said PESC, ADB and VSEB stations includes microprocessor means for controlling the gain of the amplifier at the respective station.

4. The system of claim 2 wherein said means responsive to the monitoring terminal includes a service line separate from the independent of transmission of the RF carriers between said PESC station and said ADB station and said VSEB stations.

5. The system of claim 4 including a PESC microprocessor at said PESC station, an ADB microprocessor at said ADB station, and a VSEB microprocessor at each of said VSEB stations, each said microprocessor including microprocessor means for controlling the gain of the amplifier at the associated station, at least one of said microprocessors including means for controlling the gain of amplifiers at other stations.

6. The system of claim 5 wherein said means responsive to the monitoring terminal for controlling the gain comprises said PESC microprocessor, said PESC microprocessor including means responsive to a signal at said monitoring terminal of one of the amplifiers at one of said ADB and VSEB stations for adjusting the gain of the amplifier at said PESC station to cause the level of the RF output of the amplifier at said one VSEB to fall within a predetermined range of levels.

7. The system of claim 5 wherein said means responsive to the monitoring terminal for controlling the gain comprises said ADB microprocessor, said ADB microprocessor including means responsive to a signal at said monitoring terminal of the amplifier of one of said ADB and VSEB stations for adjusting the gain of the amplifier at at least one of said ADB and PESC stations to cause the level of the RF output of the amplifier at said one VSEB station to fall within a predetermined range of levels.

8. The system of claim 6 wherein said PESC microprocessor includes means for adjusting the gain of the amplifier at at least one of the VSEB stations other than said one VSEB station to compensate for adjustment of the gain of the amplifier at said PESC that is effected in response to the monitoring signal at the output of the amplifier at said one VSEB station.

9. In a signal transmission system having first, second and third stations connected successively in a chain of stations by a signal transmission line, each station having a variable gain amplifier for controlling level of signals received thereby and for transmitting and receiving signals, a method of controlling level of signals received at said stations comprising the steps of:

monitoring the received signal level at the output of said amplifiers,

employing the signal level monitored at the output of the amplifier of said second station to vary the gain of the amplifier at said first station, wherein said first station is located upstream relative to said second station, thereby nominally varying the level of signal transmitted to said third station, and

adjusting the gain of the amplifier at said third station to compensate for the variation in gain of the amplifier at said first station, wherein said third station is located downstream relative to said second station.