Operational Description

FCC ID: NQ8DC60XU

Operational Description

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FCCID_1533292

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                        Network Interface Group

Author:       Antonio Callegaris
Date:         03/08/2011
Copyright 2011 Pace Micro Technology plc. All Rights Reserved.




Purpose
          The purpose of this document is to give a brief description of the RF4CE transceiver RF section
          and the list of frequency channels used.


Revision History
            Issue         Date                  Modification list and author
            A             03.08.2011            Original Issue – Antonio Callegaris


Definitions/Abbreviations
            Abbreviation                Description
            ADC                         Analog to Digital Converter
            BPF                         Band Pass Filter
            I/Q                         In phase / Quadrature
            LNA                         Low Noise Amplifier
            PA                          Power Amplifier
            LPF                         Low Pass Filter
            RF                          Radio Frequency
            PCB                         Printed Circuit Board
            PHY                         Physical Layer
            RX                          Receive
            RSSI                        Receive Signal Strength Indicator
            TX                          Transmit
            VCM                         Voltage Control Module


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RF Section
     Below is the top level block diagram of the RF4CE Transceiver




    TX Chain
     The I/Q Data are up-converted to RF with a local oscillator directly modulated.
     The local oscillator works at 2*Fo where Fo is frequency of RF channel
     The RF TX signal is split in two separate paths.
     The signal in each path is amplified and sent to the RF output pins (RF1 and RF2).
     When one PA is switched on, the other is switched off.

     RX Chain
     One of the two RF signals present respectively at RF1 and RF2 is selected by the diversity switch and
     amplified by the LNA.
     The signal at the LNA output is down-converted to baseband.
     The local oscillator works at (Fo – 2MHz) * 2 where Fo is frequency of RF channel.
     After being down-converted the signal goes through a BPF filter and successively to an ADC.

     Antenna Diversity
     The RF4CE Transceiver supports antenna diversity over two antennas. For every received packet
     the digital signal processor in the transceiver will select the antenna with the best signal. The
     decision is made at the very beginning of the packet. Normally the transmitter will use the antenna
     that was used to receive the last packet. The result of the antenna diversity mechanism is that either
     RF port 1 or RF port 2 can be used for transmit; there is only one antenna transmitting at the time.


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    External components and antennas

    Below is the top level block diagram of the RF4CE Transceiver external components and
    antennas.




    Each path is used as TX or RX path. Only one path per time is used.
    The signal is differential at the chipset input/output.
    A lumped element balun is used to pass from differential to single ended.
    The purpose of the lumped element LPF is to remove the harmonics of the fundamental.
    The antennas are printed F-inverted.


    Applicable Frequency Range

    The RF4CE application supports 3 RF channels; these channels are the following IEEE802.15.4
    channels:
       • CH15 2425MHz
       • CH20 2450MHz
       • CH25 2475MHz



Document Created: 2011-08-03 11:44:51
Document Modified: 2011-08-03 11:44:51

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