# Chestnut: Specifications and Interfaces

Chestnut is a high channel count, ultra wide band, high gain, direct conversion quadrature transceiver and signal processing platform. Providing simultaneous support for 4 receive and 4 transmit fully independent radio channels, this flexible platform uses two 40GBASE-R or 100GBASE-R qSFP+ ports to quickly receive and transmit radio data. With a standard instantaneous bandwidth of 500MHz, 16 bit converter resolution, and a tunable RF range between 100kHz to 9GHz, Chestnut aims to provide end users with the best possible value from a high end software defined radio platform offered by a commercial vendor. Chestnut is compatible with various signal processing tool kits, including GNU Radio and includes source code for many of its drivers and peripherals.

Note

Chestnut is capable of digital up/down conversion, so superhet architectures can be implemented using digital up/down conversion on the FPGA.

## Absolute Maximum Ratings

Stresses beyond those listed in the Absolute Ratings Table 1 may cause permanent damage to the device. These ratings are stress specifications only. Functional operation of the product at these conditions is not implied. Exposure to absolute maximum rating conditions for extended periods of time may affect reliability and is, therefore, not recommended.

Warning

EXCEEDING ABSOLUTE RATINGS MAY DAMAGE DEVICE AND MAY CAUSE DANGEROUS FIRE OR ELECTRICAL HAZARDS Exceeding these ratings may substantially damage device, and the resulting hazards may cause serious personal injury or death.

Table 1: Absolute Ratings: Exposure or sustained operation at absolute ratings may permanently damage Chestnut. Ensure fan inlets (located on both sides of the device) are not blocked during operation.

Specifications Min Max Units Notes
Operating Temperature 5 40 C At fan inlet
Operating Humidity 5 100 % Non-Condensing
Storage Temperature 0 40 C
Storage Humidity 20 95 % Non-Condensing
Input RF Power 10 dBm Do not exceed.
IO and TRIG Voltage 1.8 V Do not exceed: Direct to FPGA.
External Reference 3 Vpp Do not exceed.
SMA Torque 0.6 0.7 Nm

## Specifications

Chestnut is a very flexible radio and signal processing platform that supports high bandwidth communications over a wide tuning range. Specific performance figures are provided as an appendix to this manual; for specific measurements, please contact Per Vices.

To provide a general idea of what this product is capable of, Table 2 lists some conservative figures of its out-of-box performance. Configuration of the product towards a specific application may see some of these figures exceed at the expense of others. For more information, please do not hesitate to contact us.

Table 2: Observed Performance. These specifications reference observations taken during internal use and development. Calibration Measurements relative to 20˚C

Specification Min Nom Max Units
Common Radio RF Stage (ADF4355) 0.1 9000 MHz
Baseband Stage 0.1 140 MHz
Dynamic Range 25 70 dB
SFDR 65 dB
Receive Radio RF Input Power -40 dBm
Noise Figure, Rx RF St 3.1 7 dB
Power Gain Low 15 45 dB
Power Gain High -10 65 dB
Group Delay (Radio Chain)$$^{1}$$ Low 13.7 ns
Group Delay (Radio Chain)$$^{1}$$ High 20 ns
ADC (Receive Converter) Independent Channels 4 -
ADC resolution 16 bits
ADC Sample Rate 500 500 MSPS
Rx Sampling Bandwidth 500 MHz
Latency (input to serial)$$^{1}$$ 50 ns
Receive DSP and FPGA Specs (default Firmware) Decimation $$\left(\frac{f_{s}}{n}\right)$$ 1 256 -
Latency (FPGA DSP)$$^{1}$$ 50 500 750 ns
Transmit Radio Transmit Power Low -30 18 dBm
Transmit Power High -10 15 dBm
Group Delay (radio chain)$$^{1}$$ Low 5 ns
Group Delay (radio chain)$$^{1}$$ High 11 ns
DAC (Transmit Converter) Tx Output Bandwidth 500 MHz
DAC resolution 16 bits
DAC Sample Rate 500 MSPS
Latency (serial to output)$$^{1}$$ 50 655 804 ns
Transmit DSP and FPGA Interpolation ($$n\cdot f_{s}$$) 1 256 -
Specifications Latency (FPGA DSP)$$^{1}$$ 96 160 ns
Digital FPGA - Arria 10 -
On Board Processor Core ARM Cortex-A9 MP
LPDDR2 RAM 4 Gb
NAND Flash (x8) 4 Gb
Networking 40/100GBASE-R, Full Duplex$$^{2}$$ (each) 200 Gbps
Default IP, SFP+ Port A 10.10.10.2 -
Default IP, SFP+ Port B 10.10.11.2 -
Int. Reference (10MHz) Frequency Stability -5 5 ppb
Ext. Reference (10MHz) Input Voltage Swing 2.2 2.4 3 Vpp
IO, PPS, and TRIG FPGA IO Voltage Range 0 2.5 2.6 V

$$^{1}$$For additional information on latency, please contact us or refer to the Application Note on Latency.

$$^{2}$$For additional information on bandwidth and sample rate, we have an Application Note that might be of interest.

## External Interfaces

Chestnut has a number of user accessible interfaces through which the device can connect to external sources and sinks. Management functions are carried out over a web page hosted by the Chestnut transceiver and accessible using the Management Ethernet port on the front face of the device. Data is sent over the 100Gbps qSFP+ ports and receive and transmit antennas connect to the SMA connectors on the front of the device. Other peripherals ports provide access or the capability to improve functionality.

• 1Gbps Management Port: connects to the on-board HPS, located on the FPGA silicon, and provide a unified interface by which to control and configure the platform.

• 40GBASE-R or 100GBASE-R qSFP+: there are two qSFP ports on the front panel of the device that use 40GBASE-R or 100GBASE-R encoding to directly communicate with an optical module and interface with a ten gigabit network. These ports directly interface with the FPGA fabric and support high bandwidth, low latency communication between the ADCs and DACs.

• 50$$\Omega$$ SMA: There are eight standard SMA radio headers the front of the unit. These are used to connect to external antennas, sinks, or sources, including:

channels count description
Rx 4 The eight independent receive channels may be connected to external sources or antennas
Tx 4 The eight independent transmit channels may be connected to external antennas or sinks
• USB 2.0 A USB port connects to the Linux system running on the Hard Processor System.

• Micro-SD Slot The FPGA and Hard Processor System may be rebooted or configured using an external Micro-SD card.
• Debug Mini-DSUB The debug port provides JTAG access, and allows for the complete configuration of the unit.
• Trigger Mini-DSUB The trigger port provides access to independent, per-channel, triggers for each radio resource.
• IEC320 C14 Power A standard «computer» cable plugs into this connector to power the unit. The power supply accepts 120V or 240V.

## Operating System

Although Chestnut may be used with any operating system, we strongly recommend using a Linux operating system. This ensures you will be able to take advantage of a very large body of high performance that exists to support high performance computing Chestnut applications, while also providing a more comprehensive development environment. It will also allow users to more easily use our existing example code, and also provides for a higher performance computing environment. It is also possible to SSH into the small Linux distribution running on the on-board processor.

## Network Interface Card (NIC) Requirements

Chestnut uses a 40Gbps or 100Gbps Ethernet connection to quickly send and receive data. The following network cards have been tested for compatibility with Chestnut. The recommended NICs for Chestnut are:

Manufacturer MPN Line Rate
Mellanox MCX516A-CDAT Regular
Napatech NT200A02-2×100/40 High-throughput

If you have any questions or concerns about NIC card requirements, please do not hesitate to contact us.

## Optical Fiber Requirements

Chestnut requires active optical cabling: Chestnut can ship with high quality, qSFP cabling (AOC) that uses OM-1 type optical fiber (kit option). We suggest using Optical Multimode (OM) grade fiber (ie. OM1, OM2, OM3, or OM4). In a production environment, or when integrating the product into existing infrastructure, you may use legacy FDDI grade fiber for short runs, though we advise testing worst-case performance across the longest run prior to wide scale deployment.

Figure 1: We sugget using optical multimode (OM) grade fiber

Figure 2: This is the transceiver module that gets hooked up to the end of the Optical Fiber cable

The recommended qSFP+ optical fibre cables for Chestnut are:

Manufacturer Product
Senko MPO Female 12 Fibers Type B LSZH OM4 (OM3) 50/125 Multimode

If you have any questions or concerns about optical fiber requirements, please do not hesitate to contact us.

## Mechanical

Chestnut conforms to a 2U form factor and 19-inch rack.

## RF Chain

Simulated RF chain performance (based on component specifications) yield the simulated performance indicated in Table 1 As both the receive and transmission chains use variable stages, the figures were calculated using midpoint references for attenuation and gain stages. With proper tuning and calibration, you should expect better values. More information on the specific RF chain used may be found in the System Architecture section.