Introduction

LimeSDR XTRX Board Key Features

LimeSDR XTRX is Small form factor mini PCIe expansion card Software Defined Radio (SDR) board. It provides a hardware platform for developing and prototyping high-performance and logic-intensive digital and RF designs based on Xilinx’s XC7A50T-2CPG236I FPGA and Lime Microsystems transceiver chipsets.

LimeSDR XTRX is a building block for any Massive MIMO configuration from 2Tx2R to 32Tx32R for very high data rate applications. Hence, it could be used in conjunction with any digital processors (ASICs, GPPs and GPUs) of varying level of performance in terms of speed, power dissipation and cost to fit any air interface from narrowband to broadband signals. The board is designed for maximum scalability in terms of the following parameters:

  • Frequency and Bandwidth: The heard of the board is the Lime Transceiver RFIC (LMS7002) providing frequency flexibility up to 3.8GHz and bandwidths of over 100MHz.

  • Baseband Interface: A significant level of digital circuitry resides within the LMS7002 and accompanying Xilinx for the implementation of the key physical layer radio functions including filtering, decimation, interpolation and flexible interface such as PCIe and SerDes to name a few.

_images/LimeSDR-XTRX_v1.2_3D_top.png

Figure 1: LimeSDR XTRX v1.2 board top view

_images/LimeSDR-XTRX_v1.2_3D_bot.png

Figure 2: LimeSDR XTRX v1.2 board bottom view

LimeSDR XTRX board features:

  • RF and BB parameters:

    • Configuration: MIMO (2xTX, 2xRX)

    • Frequency range: 30 MHz – 3.8 GHz

    • Bandwidth: 30.72 MHz

    • Sample depth: 12 bit

    • Sample rate: 30.72 MSPS

    • Transmit power: max 10 dBm (depending on frequency)

  • USB 2.0 controller: Microchip USB3333E-GL

  • FPGA: board is designed based on Xilinx Artix-7 XC7A50T-2CPG236I FPGAs in 236-ball CSBGA package. Xilinx XC7A50T-2CPG236I features are:

    • 236-pin CSBGA package (10mm x 10mm, 0.5mm)

    • 52160 LUTs logic capacity

    • 2700 Kb Embedded Memory

    • 600 Kb distributed RAM

    • 120x 18x18-bit multipliers

    • 5x PLLs and 4x DLLs

    • 106 IOs

    • FPGA configuration via JTAG

  • RF transceiver: Lime Microsystems LMS7002M

  • EEPROM Memory: 128Kb EEPROM for LMS MCU firmware (optional); 128Kb EEPROM for FPGA data (optional)

  • FLASH Memory: 256Mb Flash memory for FPGA configuration

  • Temperature sensor: TMP1075NDRLR

  • General user inputs/outputs:

    • 2x Green LEDs

    • 4x GPIOs 3.3V in GPIO connector

    • 1x GPIO in Baseband connectors

  • Connections:

    • USB 2.0 (Micro-B) socket

    • Coaxial RF (U.FL female) connectors

    • FPGA GPIO 8-pin FPC connector

    • FPGA JTAG connector (unpopulated)

    • Mini PCIe edge connector

    • RF Baseband 15-pin FPC connectors

  • Clock system:

    • 26.00MHz on board VCTCXO

    • VCTCXO may be tuned by on board DAC

    • Reference clock input and output connectors (U.FL and mPCIe)

  • Board size: 50.8mm x 20.97mm (PCIe Mini card form factor)

  • Board power sources: USB connector (5V) or mini PCIe (3.3V)

For more information on the following topics, refer to the respective documents:

Board Overview

One of the key elements of LimeSDR XTRX board is the Xilinx Artix-7 (XC7A50T-2CPG236I) FPGA. It’s main function is to transfer digital data between LMS7002M RF transceiver and PC through a mini PCIe edge connector or Serial connection to another FPGA board. The block diagram for LimeSDR XTRX board is presented in the Figure 3.

_images/LimeSDR-XTRX_v1.2_diagrams_BD.png

Figure 3: LimeSDR XTRX v1.2 board block diagram

This section contains component location description on the board. LimeSDR XTRX board picture with highlighted connectors and main components are presented in Figure 4 and Figure 5, respectively.

_images/LimeSDR-XTRX_v1.2_components_top.png

Figure 4: LimeSDR XTRX v1.2 board top connectors and main components

_images/LimeSDR-XTRX_v1.2_components_bot.png

Figure 5: LimeSDR XTRX v1.2 board bottom connectors and main components

Description of board components is given in the Table 1.

Table 1. Board components

Featured Devices

Board Reference

Type

Description

IC1

RF transceiver

Lime Microsystems LMS7002M

IC7

FPGA

Xilinx Artix-7(XC7A50T-2CPG236I)

IC19

USB 3.0

microcontroller

Microchip USB 2.0 to transceiver chip USB3333E-GL

Miscellaneous devices

IC9

IC

Temperature sensor TMP1075NDRLR

IC16

IC

SIM Card Interface NVT4555UKZ

Configuration, Status and Setup Elements

X9

JTAG chain

connector

FPGA programming connector on the PCB bottom side

(compatible with Molex 788641001 connector)

LED1, LED2

Status LEDs

User defined FPGA indication LEDs

General User Input/Output

X12

Pin header

8-pin FPC connector

Memory Devices

IC2

IC

I²C EEPROM Memory 128Kb (16 x 8), connected to LMS7002M RF transceiver I2C bus

IC13

IC

I²C EEPROM Memory 128Kb (16K x 8), connected to FPGA I2C bus

IC18

IC

SPI Flash Memory 256 Mb (32M x 8) connected to FPGA SPI

Communication Ports

X11

USB 2.0

USB 2.0 Micro-B socket

X10

mini PCIe

mini PCI Express Card Edge connector

Clock Circuitry

XO1

VCTCXO

26.00 MHz Voltage Controlled Temperature Compensated Crystal Oscillator

IC17

IC

16 bit DAC for VCTCXO (XO1) frequency tuning (default)

IC11

IC

GNSS Receiver module

IC8, IC10, IC12, IC14

IC

Logic level converters

IC15

IC

Analogue switch

IC20

IC

Analogue switch

X7

U.FL connector

Reference clock input/output (CLK)

X6

U.FL connector

1PPS input

X5

U.FL connector

GNSS (active) antenna connector

Power Supply

IC22

IC

Four-output switching regulator LP8758A1E0YFFR

IC31

IC

Four-output switching regulator LP8758A1E0YFFR

IC21

IC

Linear regulator LD39100PUR

IC26

IC

Linear regulator LD39100PUR

IC29

IC

Linear regulator LD39100PUR

IC32

IC

Linear regulator LD39100PUR