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Sinclair Technologies IWCE Presentation

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Sinclair Technologies IWCE Presentation Powered By Docstoc
					System Design Concepts

    By Gus Roumeliotis




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      System Design Concepts
Antenna Combining Systems
• Allow multiple transmitters and receivers to share an antenna system
• Provide adequate isolation to permit simultaneous operation of all
   frequencies
• May consist of several antenna systems (multiple Tx & Rx antennas)

Terminology

•   Multicoupling
     – Refers to the combining of multiple transmitters and receivers onto
        a single antenna.
•   Combiner
     – Transmit multicoupler with ferrite isolators




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      System Design Concepts
Advantages

•   Maximize tower utilization
     – Reduces tower loading by minimizing the number of antennas &
        feedlines
     – Expandable systems avoid need for tower climb
     – Premium antenna location can be utilized by many users
•   Minimize interference risk
     – Proper multicoupler system is designed to avoid all transmitter
        noise, receiver desense, and intermod problems
     – Bandpass filters commonly used in multicoupler systems to
        provide carrier suppression against other transmitters and noise
        suppression to avoid causing problems for receivers.
     – Bandpass filters also inherently notch the second harmonic of the
        pass frequency




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      System Design Concepts
•   VHF systems
     – Virtually no band plan
     – Potential for extremely close Tx-Rx spacings
          • Most Tx combiner and Rx Multicoupler systems are custom designs
     – Lower frequency means separation must be greater between antennas
          • 30-40 feet tip-to-bottom to gives approx. 55 dB
     – Greater cavity efficiency in this frequency band.
          • 7” bandpass cavity set at 1.0 dB insertion loss will provide 20 dB
             isolation 1.0 MHz from f0
•   UHF Systems
     – Paired services mean standard spacings
     – Watch for close minimum spacings
          • E.g. 461 Tx and 459 Rx
     – Higher frequency means separation can be less between antennas
          • 20 feet tip-to-bottom to get 55 dB
     – Lower cavity efficiency at this higher frequency band.
          • 7” bandpass cavity set at 1.0 dB insertion loss will provide 12 dB
             isolation 1.0 MHz from f0


                                                                                 4
      System Design Concepts
•   800 & 900 MHz systems
     – Paired services mean standard spacings
     – Watch for cell sites and paging transmitters
          • 894 MHz is 2MHz from 900 MHz SMR Rx band
     – Higher frequency means separation can be less between
        antennas
          • 10 feet tip-to-bottom to get 55 dB
     – Use of ¾ wavelength cavities required
          • 7” ¾ wave bandpass cavity set at 1.0 dB insertion loss will
            provide 11 dB isolation 1.0 MHz from f0




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       System Design Concepts
The Antenna Combining System Design Objectives

•   Provide sufficient isolation between transmitters (Tx’s) and Receivers
    (Rx’s) to prevent RF interference in each receiver
     – Tx/Rx (Transmitter noise)
     – Rx/Tx (Receiver desensitization or Tx carrier)
     – Tx/Tx (Transmitter to transmitter isolation)
     – Rx/Rx (Receiver to receiver isolation)
•   Maintain proper impedance match with radios (Z0=50 OHMS)
•   Minimize insertion losses




                                                                             6
      System Design Concepts
The Antenna Combining System Design Constraints

•   Number of Transmitters (Tx’s) and Receivers (Rx’s)
•   Frequency of Tx’s and Rx’s (MHz)
•   Tx power levels (Watts)
•   Radio manufacturers (Motorola, GE, Kenwood)
•   Number of antennas (Gain of antennas in dBd)
•   Horizontal or Vertical antenna separation (Feet)
•   Future expansion needs
•   Packaging
•   Other operating frequencies on site
•   Combine or mate with existing equipment
•   Desired Price and availability




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    System Design Concepts
The Antenna Combining System Design Process

•   Obtain design constraint information
     – Tx’s & Rx’s frequencies, power levels, antennas, etc.
•   Perform intermodulation study
•   Examine frequency separations
     – Tx/Rx, Rx/Tx, Tx/Tx, Rx/Rx
•   Determine isolation requirements
     – Duplex operation curves (TNRD Curves)
•   Select type(s) of components and/or combiners to be utilized
•   Sketch design configuration using Visio
     – (Electrical and Mechanical)
•   Verify all design constraints incorporated and objectives met
•   Price system up, and check system availability
•   Finalize system diagram/quotation




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      System Design Concepts
Sinclair Capabilities

•   Custom combining and multicoupling systems available
•   Complete line of components for embedding into OEM systems
     – Cavity filters
     – Duplexers
     – Preselectors
     – Isolators
     – Preamplifiers
     – Splitters




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      System Design Concepts
Custom & Special Requirements

1.    Simplex, half-duplex, full duplex radio combining
2.    High power transmitters
3.    High isolation/low loss
4.    Small packaging
5.    Cabinet systems
6.    Various power supply configurations
7.    Large channel capacity combiners
8.    Intermod analysis & prevention
9.    Isolation analysis & design
10.   Retuning & expansion capabilities
11.   Expansion/modification of existing antenna system
12.   Environmental protection
13.   Customized products (NPR’s, R&D, etc.)


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posted:4/25/2011
language:English
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