SLAA871 January   2019 AFE7422 , AFE7444

 

  1.   AFE74xx as a single-chip wideband repeater using loopback mode
    1.     Trademarks
    2. 1 Introduction
    3. 2 Repeater Mode (RX-TX Loopback With SerDes Bypassed)
      1. 2.1 Overview of the AFE74xx Repeater Mode
      2. 2.2 Configuration of the AFE74xx as a Repeater
      3. 2.3 Programming the Repeater Mode
        1. 2.3.1 Hardware Setup
        2. 2.3.2 Software Setup and GUI Configuration
    4. 3 130-MHz Digital Repeater System Overview
      1. 3.1 Key System Specifications
    5. 4 System Overview
      1. 4.1 Block Diagram
      2. 4.2 Design Considerations
      3. 4.3 Highlighted Products
        1. 4.3.1 LMK04828
      4. 4.4 System Design Theory
    6. 5 Hardware and Testing
      1. 5.1 Measured Latency and Gain
        1. 5.1.1 Hardware
        2. 5.1.2 Test Setup and Results
      2. 5.2 Measured Linearity Performance
        1. 5.2.1 Hardware and Test Setup
        2. 5.2.2 Test Results
      3. 5.3 Measured Selectivity (Out-of-Band Jammer)
        1. 5.3.1 Hardware and Test Setup
        2. 5.3.2 Test Results
    7. 6 Terminology

4.4 System Design Theory

A digital RF repeater accomplishes the following goals:

  • Shows good selectivity by eliminating unwanted signals from being transmitted within the desired signals passband, which reduces interference in other bands
  • Shows good antenna isolation between the donor and the service antenna
  • Has low RX to TX latency
  • Shows low ac-performance degradation.

Figure 11 shows the basic, traditional, RF-repeater design architecture.

tida-060007-traditional-digital-RF-repeater.gifFigure 11. Traditional Digital RF Repeater

The traditional repeater architecture first conditions the input signal using filters and LNAs. The local oscillator (LO) mixer downconverts the band to an intermediate frequency. The signal is filtered, sampled, and then sent to an FPGA for digital processing. The downmixing process is then reversed, and the final signal is output through the donor antenna to the desired base station.

All of the frequency translation functions of the traditional RF repeater are performed in the digital domain of the integrated AFE74xx system. This system replaces the need for discrete mixers, IF filters, and LOs (PLLs) from the analog-signal chain in order to achieve direct synthesis.