Software Defined Radio


The ultimate low-cost massive MIMO SDR, with up to 32x32 transmit/receive channels

$106,450 raised

of $16,000 goal

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XYNC is part of the Qorvo RF Accelerator and the Molex Stay Connected Design Challenge!

Eight XTRX Boards, Synchronized & Multiplexed

If you’re working on a massive MIMO system or have a large swath of spectrum you need to monitor, XYNC (pronounced iks-sync) is right for you. XYNC builds on the success of the Octopack SDR we offered during the XTRX campaign and takes into account feedback from the original Octopack users.

XYNC (back)

Synchronized and Multiplexed XTRXs

A single XYNC comes equipped with four or eight removable XTRX boards, metal installation brackets, cables for all of the TX/RX ports and the GPS port, and a special board for synchronizing the XTRX units. Each onboard XTRX provides two transmit channels and two receive channels. Thus, XYNC Octo (with eight XTRX units) has 16 transmit and 16 receive channels. Two XYNC Octos can be synchronized and will give you 32 transmit and 32 receive channels.

On the digital side, each XTRX unit is connected to a PCIe switch that multiplexes the XTRX PCIe lanes into a single PCIe 2.0 x4 connector. This makes it very compact and easy to install into a standard PC. Just don’t forget to provide enough air flow for cooling, as setups like this can get quite hot.

A single XTRX is shown above. XYNC includes up to eight XTRX boards.

Features & Specifications

RF Bandwidth

XYNC is based on multiple synchronized XTRX SDRs, so the maximum achievable RF bandwidth is a function of the individual XTRX RF bandwidths.

If you want to tune XYNC channels to receive or transmit at different parts of the spectrum, please keep two things in mind:

  1. XTRX RF filters are not ideal and have natural roll-off towards the edge, so you might need to overlap the XTRXs' receive/transmit windows to achieve a contiguous spectrum within which to receive or transmit.
  2. Each XTRX has only one receive and one transmit PLL, so both RX channels are "locked" to one other, as are both TX channels. This means that a single XYNC board only provides up to eight independent RX channels and eight independent TX channels.

XYNC Simplified Block Diagram

XYNC simplifed block diagram (without phase sync loopback)

XYNC Full Block Diagram

XYNC full block diagram (with phase sync loopback)

Sampling Rate & Throughput Limits

XYNC uses a PCIe switch to connect all of its XTRXs to a single PCIe bus. The XTRXs are connected to the PCIe switch with PCIe 2.0 x1 buses, and the switch is connected to the host with a PCIe 2.0 x4 bus, which introduces additional limits to the XYNC sampling rate and throughput compared to a single XTRX.

Expanding on the (theoretical) maximum XTRX throughput limits, we get the following throughput per channel for XYNC Octo in various configurations. Green cells indicate combinations of sample rate and PCIe bus configuration where the sampling rate is not limited by the PCIe bus but by the XTRX itself.

Maximum PCIe Bus Throughput by Configuration

ModeIQ x Ch x bitsBits totalPCIe 1.0 x1 (max 1,750 Mbps) PCIe 2.0 x1 or PCIe 1.0 x2 (max 3,500 Mbps) PCIe 2.0 x2 (max 7,000 Mbps) PCIe 2.0 x4 XYNC Total throughput (max 14,000 Mbps) PCIe 2.0 x4 per XYNC Octo channel (max 14,000 Mbps)
8-bit SISO2 x 1 x 816 bits109 Msps219 Msps 438 Msps 875 Msps 109 Msps
12-bit SISO2 x 1 x 1224 bits73 Msps146 Msps 292 Msps 583 Msps 73 Msps
16-bit SISO2 x 1 x 1632 bits55 Msps109 Msps219 Msps 438 Msps 55 Msps
8-bit MIMO2 x 2 x 832 bits55 Msps109 Msps 219 Msps 438 Msps 55 Msps
12-bit MIMO2 x 2 x 1248 bits36 Msps73 Msps146 Msps 292 Msps 36 Msps
16-bit MIMO2 x 2 x 1664 bits27 Msps55 Msps109 Msps 219 Msps 27 Msps

SISO & MIMO configurations

In the table above, SISO configurations mean that only one receive and one transmit channel is used on each XTRX, i.e., XYNC Octo would have 8x8 RX/TX channels. MIMO configurations mean that both receive and both transmit channels are used on each XTRX, i.e., XYNC Octo would have 16x16 RX/TX channels. This is why SISO configurations enjoy twice the bandwidth per channel of MIMO configurations – they have half as many channels between which to share that bandwidth.

Synchronization & Phase Coherency

What exactly does XYNC synchronize? The answer is a bit complex. Below are some important facts you should keep in mind:

Note that the XYNC software package does not currently include the phase calibration algorithm. Please contact us directly if you need support with phase calibration.

Power Consumption

XYNC consists of three main units:

  1. The PCIe switch unit
  2. The synchronization & frontend unit
  3. Several XTRX SDR units (8x for Octo)

The power consumption of the PCIe switch and frontend units is relatively constant at about 10 W.

XTRX power consumption varies significantly depending on whether you’re doing RX, TX, or both; on whether you’re doing continuous or burst TX/RX; and on output power, internal gains, bandwidth, digital pre-processing, and a few other parameters. Maximum XTRX power consumption at maximum sample rate and gains is approximately 3 W, for a total of 34 W maximum power consumption for the entire XYNC Octo system.

Power Supply

XYNC is powered from two different sources, a PCIe edge connector and a 6-pin 12 V GPU ATX Molex connector:

PCIe Switch Unit:PCIe edge connector
Synchronization & Frontend Unit:6-pin 12 V GPU ATX Molex connector
XTRX Units:PCIe edge connector

6-pin 12 V GPU ATX Molex connectors, which are typically used to provide power to video cards, look like the following:

In terms of voltages, XYNC uses 3.3 V and 12 V from the PCIe connector and 12 V from the 6-pin ATX connector for the synchronization logic on the synchronization & frontend unit.


With tens of watts of power consumption, cooling is important. Output power and other parameters of the LMS7002M chips we’re using begin to degrade at about 80°C. It’s important to keep the ambient temperature significantly below that to provide enough of a temperature gradient for the chips to cool. If you’re interested in phase stability, it’s also important to keep the temperature as stable as possible – temperature changes can noticeably affect phase stability, causing phase differences between the XYNC channels to drift.

For general applications, we recommend at least providing a stable flow of air through the PCIe compartment. For industrial applications, an external box with a passive heatsink might be a good choice. You can connect such a box to the PCIe bus with a PCIe bus extender.

Fairwaves is happy to work with backers on heat dissipation designs that will keep your XYNC operating safely under its target conditions.

XYNC Variants

During the original XYNC campaign, we offered a few XYNC variants in addition to the currently available XYNC Octo:

For more information on these variants, see the archived campaign page.

Fulfillment & Logistics

Crowd Supply is handling all shipping. Take a look at their Frequently Asked Questions (FAQ) page for answers to the most common fulfillment questions.

XYNC is participating in the Qorvo RF Accelerator!

In the Press

Geeky Gadgets

"Developers, makers and enthusiasts working on a MIMO system may be interested in a new piece of hardware, launched by the Crowd Supply website last month, called the XYNC."


"Con diversos modelos que van de menos a más potencia, esta radio definida por software con capacidad MIMO puede ser utilizada en conexión con otra placa idéntica para otorgar todavía mayor funcionalidad."

"[XYNX]is designed for situations or use cases that involve large band of spectrum monitoring or massive MIMO system... "

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Produced by Fairwaves in Boston, USA and London, UK.

Sold and shipped by Crowd Supply.


Eight XTRXs provide 16 TX channels at 30 MHz - 3.7 GHz and 16 RX channels at 30 MHz - 3.7 GHz.

$6,990 Free US Shipping / $18 Worldwide

About the Team


Boston, USA and London, UK  ·

We are a vertically integrated vendor of cellular equipment focused on the needs of emerging markets. We are developing, manufacturing, deploying, and operating turn-key cellular network solutions including radio equipment, towers, power and backhaul all the way to a core network and SS7 interconnect. Our team has been building software-defined radios and systems based on them since 2009 and is well known for its ClockTamer, UmTRX, and UmSITE products.

Alexander Chemeris


Sergey Kostanbaev

Software & Firmware Development

Andrey Sviyazov

Hardware Design

Albert Gardiner


Andrey Bakhmat


Andy Avtushenko


See Also

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