by embedINN

A versatile dev board with everything you need to design custom IoT protocols & gateways

View all updates Sep 18, 2020

Browsing the Sky For GNSS Satellites

by Abdul Malik Khan

The iotSDR has a Max2769 GNSS front-end chip capable of receiving on the GNSS L1 band. GNSS systems are similar, in some respects, to satellite communication systems. They provide a unique set of features that we believe justifies the inclusion of such a specialized receiver chip. Some of the features that we would like to discuss here include:

  1. Simplex communication (no two-way communication)
  2. Low transmit and receive power (a 25 W transmitter covers the globe)
  3. The receiver searches carrier-phase and Doppler measurements with very high sensitivity

To achieve their performance requirements, GNSS receivers typically rely on a specific front-end rather than a generic SDR front-end.

The GNSS chip on iotSDR has a transmit-only SPI interface for configuration and I/Q (or simple I) streaming. It can be configured in a variety of ways. For general usage, we have configured the chip to have a 16.384 MSPS sampling rate, with 4.092 MHz Intermediate Frequency (IF) streaming from 2-bit I and 2-bit Q interfaces. The block design in the FPGA Programmable Logic (PL) element of the ZYNQ SoC compacts 8 samples of 4-bit data into a 32-bit word, stores it in ping-pong memory, and makes it available to the ARM Processing System (PS) element of the SoC. The LwIP-based application in the PS transmits the logged data via UDP or TCP stream. That stream can be received on a host using a python script, a C++ application, or GNU Radio’s iotSDR module. Finally, the received data can be post-processed using available GNSS software-defined receivers.

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Product Choices


iotSDR 7020

One iotSDR dev board with a Zynq XC7Z020 FPGA


Ethernet cable (1M)

From the Crowd Supply Basics project.

Bel Ethernet Cable: RJ45 CAT5E Shield (1M). Connector ends: RJ45, wire gauge: 24 AWG, male / male.


Active GPS Antenna

From the Crowd Supply Basics project.

A low-noise active GPS antenna suited for the GPS L1 band. Accepts 3-5V DC and outputs RF via an SMA(m) connector. Optional adhesive mounting.


916 MHz Helical Monopole Antenna

From the Crowd Supply Basics project.

Order two for use with iotSDR.

916 MHz ISM Right Angle SMA Connector (LoRaWAN, HaLow, IoT Low-Profile Whip) by Linx Technologies


LCW Dipole Antenna

From the Crowd Supply Basics project.

Order two for use with iotSDR.

2.4 GHz Dipole Tilt Swivel Antenna with SMA connector by Linx Technologies. Length: 83.1 mm


430-435 MHz SMA Male Antenna

From the Crowd Supply Basics project.

Order two for use with iotSDR.

One single 433MHz Swivel Stick Dipole – SMA-M Stick Antenna by Pulse. (Image includes two antenna to show swivel capability.)


microSD Card

From the Crowd Supply Basics project.

An industrial-grade memory card with extended endurance.



Embedding things in reality.

Abdul Malik Khan

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