LimeSDR Micro is a next-generation, high-performance, software-defined radio (SDR) with integrated vector signal processing acceleration, packaged in a compact M.2 2280 form factor. Featuring an NXP LA9310 baseband processor and Lime Microsystems LMS7002M transceiver, LimeSDR Micro is an all-software-programmable platform with market leading size, weight, power, and cost.

LimeSDR Micro may be used as a classic SDR with all processing carried out on the host computer, or the LA9310 Vector Signal Processor Accelerator (VSPA) may be used to offload physical layer processing and thereby significantly reduce load on the host CPU, while simultaneously reducing power consumption and enabling the creation of highly energy-efficient solutions.

From Enthusiast to Advanced Applications

LimeSDR Micro is suited to a wide variety of applications, ranging from simple receive-only and narrowband uses, to signal analysis, cellular base stations, custom user equipment/modems, drone communications, and more.

Thanks to its compact nature and the NXP LA9310 ultra-low power consumption baseband processor, LimeSDR Micro is suited to many applications where a classic SDR simply would not meet the size, weight, and power requirements. Integrating a commercial baseband processor provides a clear path to highly optimized solutions deployed at scale.

Features & Specifications

• Channels¹: 1T2R expandable to 1T4R
• Frequency Range: 30 MHz – 3.8 GHz
• Bandwidth: 100 MHz TDD or half-duplex operation and 50 MHz FDD
• Analogue Filtering: 0.75 – 100 MHz
• Sample Rate: up to 160 Msps half-duplex (Tx or Rx) and TDD, and up to 61.44 Msps FDD
• Vector Signal Processing Accelerator: up to 80 GFLOPs
• Control Processor: ARM Cortex-M4 at up to 307 MHz
• Host Interface: 1x lane PCIe Gen 3
• Clock Subsystem:
  • Rakon E6245LF 30.72 MHz VCTCXO
  • VCTCXO may be tuned by an onboard 16-bit DAC
  • Reference clock input and output connector
• EEPROM Memory: 512Kb (used for NXP LA9310 initial configuration)
• Temperature sensor: TMP1075NDRLR
• Optional GNSS Receiver²: Antenova M10578-A3 3 (not fitted on basic variant)
• General purpose inputs/outputs:
  • 2x Green LEDs
  • 4x GPIOs 3.3V on GPIO connector
  • IC2 on GPIO connector (shared with on-board devices)
• Connectors:
  • M.2 2280 Key B+M
  • 3x MHF4 RF (TX, RX1 & RX2)
  • 4x MHF4 clock and PPS I/O
  • 15-pin FPC external analogue I/Q baseband input (RX3 & RX4)
  • 8-pin FPC GPIO
  • Board size³: 22 mm x 80 mm

Notes:

¹ As supplied, LimeSDR Micro has 1x transmit and 2x receive channels, but may be expanded up to 4x receive channels via two analogue baseband inputs on an FPC connector.

² At present, the optional GNSS receiver may be used for location, time of day, and generating a VCTCXO DAC value. A future firmware update may add GSPDO support, but this is not guaranteed.

³ LimeSDR Micro may not be suited to installation in certain space-constrained systems, e.g. laptops, due to the increased (non-standard) module height of up to ~4mm from the PCBA top side.

Block Diagram

Note that the GNSS receiver is optional and not fitted with the basic version.

Board Overview

LimeSDR Micro M.2 2280 Overview (top)

LimeSDR Micro M.2 2280 Overview (bottom)

100% Software-Programmable

LimeSDR Micro is an all-software-programmable platform and does not require FPGA development experience in order to take advantage of hardware-accelerated signal processing. The NXP LA9310 Reference Manual and VSPA2 Instruction Set Manual are both available without NDA, along with of course comprehensive documentation for Lime Microsystems LMS7002M.

NXP also provide a collection of open source VSPA kernels for functions such as FFT, inverse FFT, CRC generation, FIR filters, mixer, and modulation/demodulation of up to 1024-QAM. With selected kernels accompanied by MATLAB scripts for generating test vectors. The DSP kernels may be used both to extend the default firmware and to create of entirely new firmware, for example, to implement physical layer processing for a particular wireless standard.

LA9310 block diagram, copyright NXP Semiconductors

LimeSDR Micro uniquely combines the power and flexibility of SDR running on a general-purpose processor (GPP) such as a development workstation, with the option to progressively transfer compute-intensive functions to a commercial baseband processor, thereby providing a clear path from developing applications in the lab to deploying them in demanding and resource-constrained environments.

Open Source

LimeSDR Micro is a fully fledged member of the LimeSDR family, which was established a decade ago and set the standard for radically open software-defined radio.

LimeSDR Micro is supported by:

• Open source hardware design: LimeSDR Micro Altium projecy
• Open source control firmware: LimeSDR Micro LA9310 ARM Cortex-M4 project
• Open source DSP firmware: LimeSDR Micro LA9310 VSPA project
• Open source driver stack: Lime Suite NG
• Detailed documentation: MyriadRF website

The VSPA firmware can be built by a free-to-use, Linux-based compiler, with a single command (cmake target) which sets up the toolchain and builds the firmware project.

Lime Suite NG includes plug-ins for SoapySDR, GNU Radio, Amarisoft 4G/5G, and others. There is also support for OpenAirInterface and srsRAN Project.

Expandable

LA9310 has a 1T4R architecture. The first two receive channels are connected to LMS7002M, providing coverage over a 30 MHz – 3.8 GHz frequency range. A 15-pin FPC connector provides access to the second two LA9310 analogue baseband inputs, which may be used with accessories that increase the channel count and extend the frequency range. In addition, an 8-pin FPC provides access to GPIO for accessory control.

LimeFEA HF Micro

LimeFEA HF Micro adds a third receive path with a frequency range of 0 - 30 MHz to LimeSDR Micro. This third receive channel uses a direct sampling architecture and essentially captures the entire HF frequency range, with tuning then performed in the digital domain, along with digital filtering, demodulation, etc.

LimeFEA HF Micro integrates configurable analogue filtering so as to help mitigate the effect of blockers and improve sensitivity:

• Medium Wave (MW) broadcast notch filter
• Band filters:
  • 0 - 2 MHz LPF
  • 2 - 12 MHz BPF
  • 12 - 30 MHz BPF

In addition, LimeFEA HF Micro provides:

• 90 dB gain
• 72 dB programmable step attenuation
• 5x MHF4 to SMA transition
• TDD switching out

The five MHF4-to-SMA transitions are provided for convenient access to LimeSDR Micro RF and clock I/O. Likewise with the TDD signal, which is present on the same FPC connector as the I²C signals which are used to configure the LimeFEA HF Micro board.

LimeFEA HF Micro Full RF Path

Straight-through MHF4-to-SMA transitions are not shown

Please note that LimeFEA HF Micro integrates relatively basic band filtering and certain uses may benefit from additional, narrower band filtering such as that provided by a pre-selector.

LimeSDR Micro Pro

LimeSDR Micro Pro builds on LimeSDR Micro to provide a highly convenient USB 4.0 (40 Gbps mode only) peripheral that also integrates LimeFEA HF Micro. The solution is packaged in a high-quality enclosure which is machined from solid aluminium, and is powered via USB Type-C PD.

Please note that LimeSDR Micro Pro can only be used with computers which support USB 4.0 40 Gbps mode (a.k.a. Thunderbolt 3). It will not work at all with slower ports or USB 3.x!

LimeFEA M.2 2280

LimeFEA M.2 2280 is a combination of an adapter that allows LimeSDR Micro M.2 2280 to be used in a full-size PCIe x4 or larger slot, and a 2x2 MIMO RF front-end (RFE) which integrates low-noise amplifiers (LNAs) in the receive paths (100 MHz to 4 GHz receive frequency range) and power amplifier (PA) drivers in the transmit paths (100 MHz to 6 GHz transmit frequency range).

LimeFEA M.2 2280 Full RF Path

Prelimenary Figures

LimeFEA M.2 2280 is based on the existing LimeFEA mPCIe Full design and the figures shown here are those measured for the latter.

TDD switching is controlled via a LimeSDR Micro GPIO pin and enables a single RF connection to be used for transmit and receive, e.g., with LTE-TDD and 5G NR TDD operation.

Note that only one transmit path will be active when used with LimeSDR Micro, since it is a 1T2R design. However, LimeFEA M.2 2280 may also be used with future M.2 2T2R SDRs.

Any RF cables, such as SMA-to-U.FL pigtails for the PCIe bracket, should be ordered separately.

Manufacturing Plan

Selected partners and customers have had access to pre-production hardware for some months and the design has been updated based on feedback received and the results from our own testing. We are now ready to go into production using the same trusted manufacturing partners we’ve used to deliver other products in the LimeSDR family.

Fulfilment & Logistics

After completing production, we’ll send everything to Crowd Supply’s fulfilment partner, Mouser Electronics, who will distribute products to backers worldwide. You can learn more about Crowd Supply’s fulfilment service under Ordering, Paying, and Shipping in their guide.

Risks & Challenges

The biggest risk we face is supply chain uncertainty. From finding reliable sources of components, to being on site for production, we’ve made every effort to ensure smooth delivery to backers. Should something nonetheless go wrong, we’re committed to communicate openly and honestly about what’s going on and what we’re doing to fix it. We appreciate the trust you put in us!