MSS L-band Radio Frequency Unit (RFU)

Square Peg Communications Inc.’s Radio Frequency Unit (RFU) is a frequency converter that translates frequencies in the 70 MHz IF band to/from the MSS L band utilized by Inmarsat, LightSquared, Thuraya and other mobile satellite operators. Some RFU variants also cover the extended L band (XL) supported by Inmarsat’s new Alphasat satellite.

The RFU is normally used for mobile terminal (MT) testing in conjunction with an SPCI Physical Layer Tester (PLT). In this configuration, the RFU allows the PLT to emulate the air interface as seen by the mobile terminal. Other variants of the RFU are also available which permit the IF equipment to emulate a mobile terminal or to perform off-air monitoring.

For mobile terminal testing, the RFU interfaces to the terminal at its L-band antenna port. A high-power attenuator mounted outside the RFU chassis brings the signal level to a convenient range, and a diplexer separates the received and transmitted signals. The separate transmit and receive RF signals pass through external loops, allowing the diplexer to be bypassed if desired.

The received L-band signal is converted to IF by a fixed-tuned downconverter. The IF signal is split into five outputs to drive a maximum of five demodulators. The level of the received signal can be adjusted with a manual step attenuator to match the input range of the demodulators.

The IF transmit signals from up to five modulators are combined and converted to L-band by a fixed-tuned upconverter. The level of the L-band signal is set with a manual step attenuator.

Noise or other interference can be added to the transmitted L-band signal via an auxiliary L-band input.

  • Physical

    RF Unit (RFU)

    19” / 3U rack mount enclosure

    RF Interface

    Connector

    N female

    Impedance

    50 ohm nominal

    Receive frequency

    -01, -03:  1626.5 to 1660.5 MHz

    -02, -04:  1525.0 to 1559.0 MHz

    -05:         1626.5 to 1675.0 MHz

    Receive level (into high-power attenuator)

    0 to +48 dBm (+45 dBm max per channel)

    Receive level (into RFU)

    -30 to +18 dBm

    Receive gain (Rx attenuator set to 0 dB)

    18.5 ± 3.5 dB

    Receive attenuator

    0 to 60 dB in 10 dB steps

    Receive flatness

    ± 3.0 dB

    Receive spurious signals

    ≤ -90 dBm

    Receiver 3rd order intermodulation

    ≤ -55 dBc (two carriers at -23 dBm each, receive path attenuation adjusted optimally)

    Transmit frequency

    -01, -03:  1525.0 to 1559.0 MHz

    -02, -04:  1626.5 to 1660.5 MHz

    -05:         1518.0 to 1559.0 MHz

    Transmit level (from high-power attenuator)

    -60 dBm max per-carrier (IF input signals) -15 dBm max (externally applied noise)

    Transmit level (from RFU)

    -30 dBm max per-carrier (IF input signals) +15 dBm max (externally applied noise)

    Transmit gain (Tx attenuator set to 0 dB)

    -10 dB

    Transmit attenuator

    0 to 60 dB in 10 dB steps

    Transmit level flatness

    ± 3.0 dB

    Transmit spurious

    < -95 dBm

    Transmit 3rd order intermodulation

    ≤ -55 dBc with two carriers input at IF of –20 dBm each

    Phase noise density (Tx or Rx)

    -01, -02, -05 :

    @ 10 Hz:     ≤ - 67 dBc/Hz

    @ 100 Hz:   ≤ - 80 dBc/Hz

    @ 1 kHz:     ≤ - 86 dBc/Hz

    @ 10 kHz:   ≤ - 94 dBc/Hz

    @ 100 kHz: ≤ - 110 dBc/Hz

    -03, -04 :           

    @ 10 Hz:     ≤ - 67 dBc/Hz

    @ 100 Hz:   ≤ - 79 dBc/Hz

    @ 1 kHz:     ≤ - 79 dBc/Hz

    @ 2 kHz:     ≤ - 70 dBc/Hz

    @ 10 kHz:   ≤ - 92 dBc/Hz

    @ 100 kHz: ≤ - 110 dBc/Hz

    Frequency accuracy

    Per input reference

    TX IF Interface

    Number of ports

    5

    Connector

    BNC female

    Impedance

    50 ohm nominal

    Frequency

    -01, -02 : 50.0 – 84.0 MHz

    -03, -04 : 53.0 – 87.0 MHz

    -05 :        43.0 – 84.0 MHz

    Input level

    -20 dBm to -40 dBm per channel


    RX IF Interface

    Number of ports

    5

    Connector

    BNC female

    Impedance

    50 ohm nominal

    Frequency

    -01, -02 variants:   51.5 – 85.5 MHz

    -03, -04 variants:   53.0 – 87.0 MHz

    -05 variant:            41.5 – 90.0 MHz

    Output level

    -20 dBm to -40 dBm per channel

    Reference Interface

    Connector

    BNC female

    Impedance

    50 ohm nominal

    Frequency

    10 MHz

    Input level

    -01, -02, -05 variants: 0 dBm ± 3 dB

    -03, -04 variants:    + 3 dBm ± 2 dB

    Power

    Connector

    IEC 320 male

    Voltage

    105-130 VAC or 205-250 VAC, 47?63 Hz

    Current

    ≈0.12 A rms at 115 VAC

  • Model Number

    Function

    EM-907516C-01

    LES emulator with PLT IF

    EM-907516C-02

    MT emulator with PLT IF

    EM-907516C-03

    LES emulator with 70 MHz IF

    EM-907516C-04

    MT emulator with 70 MHz IF

    EM-907516C-05

    LES emulator (XL) with PLT IF

  • RFU Data Sheet

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