Table Of Contents

LO Sharing

Last Modified: May 17, 2017

You can configure the PXIe-3620 RF Upconverter and Downconverter Module module to use an external local oscillator (LO) signal when preparing the signal for upconversion or downconversion.

You can configure the PXIe-3620 to use internal or external LOs, but the module uses internal LOs by default. The LOs have the following uses:

  • LO1—LO source for the mmWave radio head.
  • LO2—Upconverts an in-phase/quadrature (I/Q) baseband signal to an intermediate frequency (IF) signal, and downconverts from an IF signal to an I/Q baseband signal, as shown in the following figure.
    spd-note-note
    Note  

    When simultaneously using the transmit and receive channels, the IF frequencies for receiving and transmitting must be the same.

Figure 1. PXIe-3620 Block Diagram
The mmRH-3602/3642/3652 mmWave Radio Heads use high-side LO injection, where RF Frequency = LO Frequency - IF Frequency. These values are determined using the following formulas:
  • LO Frequency = LO1 Frequency × 4
  • IF Frequency = LO2 Frequency × 3
The mmRH-3647/3657 mmWave Radio Heads use low-side injection, where RF Frequency = LO Frequency + IF Frequency. These values are determined using the following formulas:
  • LO Frequency = LO1 Frequency × 8
  • IF Frequency = LO2 Frequency × 3

The following table shows the resulting frequencies given example user-defined LO frequencies.

Table 1. Example Frequencies
mmWave Radio Heads Mode LO1 Frequency LO2 Frequency IF Frequency RF Frequency
All radio heads IF only 3.667 GHz (user-defined) 11 GHz
mmRH-3602/3642/3652 mmWave 9.765 GHz (user-defined) 3.52 GHz (default) 10.56 GHz 28.5 GHz
mmRH-3647/3657 mmWave 7.625 GHz (user-defined) 4 GHz (default) 12 GHz 73 GHz

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