A Complete Solution for Custom HAM, Cellular, and Wideband Networks

The Lime RF Front End (LimeRFE) is an open hardware power amplifier (PA) module with appropriate filtering and support circuitry to augment the LimeSDR, LimeSDR Mini, and LimeNET Micro platforms, providing a complete solution that addresses real life applications ranging from HAM radio to standards-compliant cellular network implementations.

LimeRFE will enhance any LimeSDR based wireless project by providing:

• A stronger, clearer signal when transmitting
• Less noise when receiving
• Improved range for both

Software-Defined Front End

A single LimeRFE covers three very different sets of bands: HAM, cellular, and wideband. The exact band used at any given time is software-selectable. By making the RF front end definable in software, LimeRFE is the next step in the evolution of software-defined radio.

LimeRFE render front (left) and back (right)

Features & Specifications

HAM Bands

* Preliminary estimates of 1-dB compression point

** See note below about HF bands

A Note About HF Bands

Depending upon the application and overall system configuration, additional filtering may be required for use with HF bands. In particular, HF is not one, but ten bands starting at 1.6 - 1.8 MHz and moving upward incrementally to 28.0 - 29.7 MHz. On-board filtering will attenuate signals greater than 30 MHz, but not Tx harmonics, or out-of-band Rx signals below this. You may need additional filtering, depending on the environment (if there are nearby HAMs operating on other HF bands, for example) and on whether or not you are using external power amplifiers with integrated filters, antenna tuning units, etc.

Cellular Bands

Wideband Channels

* Preliminary estimates of 1-dB compression point

Additional Features

• Filtering
  • Each band has appropriate filtering both for Rx & Tx
  • Selectable AM/FM notch filter
• Fully Open Source Software
  • Firmware
  • API support
  • GUI
  • LimeSuite integration
• Control & Configuration
  • Programmable via Arduino IDE
  • Arduino Nano-compatible microcontroller (ATmega328)
  • FT232RL USB-to-serial converter
  • Host serial connection via USB mini Type B connector
• Power & SWR Meter
  • 1 – 4000 MHz power & SWR meter (external directional coupler required)
  • Cellular bands Tx power meter (internal coupler)
• 10-pin Interface to SDR
  • Power and ground
  • I2C (SDA and SCL)
  • 2x GPIO connected to on-board microcontroller
  • 4x bi-directional level shifted I/O
    • 1.2 – 5.5 V
    • Each I/O has a high voltage and power Darlington drive stage for inductive loads (e.g., coaxial relays)
    • Individually switchable direction (input/output)
• Power Supply
  • Single 12 V supply
  • Optionally supply microcontroller and Rx channels via USB

Block Diagram

* Output 1 dB compression values are preliminary assessments only. Final values may differ. Values are given for the driver outputs - final output values will be lower.

Fulfillment & Logistics

All LimeRFE boards will be delivered to Crowd Supply’s warehouse for final distribution to backers worldwide. For more information, please see this page about ordering, paying, and shipping.

Risks & Challenges

We’ve produced a number of prototype revisions to verify the performance over the RF bands detailed above. As with previous Lime Microsystems campaigns, supply chain is our biggest risk – parts shortages could delay production. LimeRFE will, however, benefit from the considerable work we’ve already put into creating various LimeSDR supply chains.