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Device Overview

The CBX is a full-duplex, wideband transceiver that covers a frequency band from 1.2 GHz to 6 GHz with a instantaneous bandwidth of 40 MHz or 120 MHz. The CBX can serve a wide variety of application areas, including WiFi research, cellular base stations, cognitive radio research, and RADAR. The CBX daughterboard is supported by the USRP Hardware Driver™ (UHD) software API for seamless integration into existing applications.

The CBX does not provided phase coherent operation, and therefore is not recommended for MIMO and Phased Array applications.

Key Features

  • Frequency Range: 1.2GHz - 6GHz
  • Versions: 40MHz / 120MHz
Product cbx 40.jpg
Product cbx 120.jpg

Daughterboard Specifications


  • 2 quadrature frontends (1 transmit, 1 receive)
    • Defaults to direct conversion
    • Can be used in low IF mode through lo_offset with uhd::tune_request_t
  • Independent receive and transmit LO's and synthesizers
    • Allows for full-duplex operation on different transmit and receive frequencies
    • Can be set to use Integer-N tuning for better spur performance with uhd::tune_request_t


Transmit: TX/RX

Receive: TX/RX or RX2

  • Frontend 0: Complex baseband signal for selected antenna
  • Note: The user may set the receive antenna to be TX/RX or RX2. However, when using a CBX board in full-duplex mode, the receive antenna will always be set to RX2, regardless of the settings.


  • Transmit Gains: PGA0, Range: 0-31.5dB
  • Receive Gains: PGA0, Range: 0-31.5dB


  • CBX: 40 MHz, RX & TX
  • CBX-120: 120 MHz, RX & TX


  • lo_locked: boolean for LO lock state


  • All LEDs flash when daughterboard control is initialized
  • TX LD: Transmit Synthesizer Lock Detect
  • TX/RX: Receiver on TX/RX antenna port (No TX)
  • RX LD: Receive Synthesizer Lock Detect
  • RX1/RX2: Receiver on RX2 antenna port

RF Specifications

Freq Range

  • 1.2GHz - 6GHz

Noise Figure

  • 5 - 7.5 dB @ (1.2GHz ~ 5GHz)
  • 7.5dB - 10 dB (5GHz ~ 6GHz)

RX IIP3 (Max)

  • 8 - 10 dBm

RX IQ Imbalance

  • -20 dBc

TX Power (Max)

  • 22 dBm @ (1.2GHz ~ 3GHz)
  • 12 ~ 22 dBm @ (3GHz ~ 6GHz)


  • 30 - 32 dBm @ (1.2GHz ~ 5GHz)
  • 26 ~ 30 dBm @ (5GHz ~ 6GHz)

TX IQ Imbalance

  • -20 dBc

Input/Output Impedance

  • All RF Ports are matched to 50 Ohm with -10dB or better return loss generally. Detailed test is pending.

Input Power Levels

  • The maximum input power for the CBX is -15 dBm.

RF Performance Data

Hardware Specifications

  • Ettus Research recommends to always use the latest stable version of UHD


  • Current Hardware Revision: 1
  • Minimum version of UHD required: 3.8.0

Environmental Specifications

Operating Temperature Range

  • 0-40 °C

Operating Humidity Range

  • 10% to 90% non-condensing

USRP Compatibility


  • N or X Series


  • X Series only

Phase Synchronization

The CBX daughterboard is not capable of phase-synchronous operation. The SBX, UBX, TwinRX daughterboards are recommended for phase-coherent applications.



CBX Schematics

Key Component Datasheets

Part Number Description Schematic ID (Page)
VMMK-3603 Low Noise Amplifier U1, U5 (1)
AS225-313LF SPDT Switch U3, U6 (1)
MGA82563 Amplifier U4 (1)
GVA-84+ Amplifier U9 (1)
PHA-1+ Amplifier U8 (1)
ADL5380ACPZ Quadrature Demodulator U11 (2)
ADA4927-2YCPZ Differential ADC Driver U10 (2)
AD8591ARTZ-REEL Amplifiers U31 (2)
NC7WZ04P6X Dual Inverter U26 (3); U15, U16 (4); U21 (5); U27 (6)
MAX2870ETJ+ Fractional/Integer-N Synthesizer U23 (3); U24 (6)
SKY13267-321 Diversity Switch U12 (3); U25 (6)
LFCN-2000+ Low Pass Filter FL13 (3); FL12 (6)
LP3878MR-ADJ Voltage Regulator U13, U14 (4); U19, U20 (5)
24LC024 EEPROM U17 (4); U22 (5)
ADL5375-05 Quadrature Modulator U18 (5)


RF Connectors

  • The CBX daughterboard features female SMA connectors for both the TX/RX and RX2 connectors.



As of December 1st, 2010 all Ettus Research products are RoHS compliant unless otherwise noted. More information can be found at http://ettus.com/legal/rohs-information

China RoHS

Management Methods for Controlling Pollution Caused by Electronic Information Products Regulation

Chinese Customers

National Instruments is in compliance with the Chinese policy on the Restriction of Hazardous Substances (RoHS) used in Electronic Information Products. For more information about the National Instruments China RoHS compliance, visit ni.com/environment/rohs_china.

Certificate of Volatility



FPGA Resources

UHD Stable Binaries

UHD Source Code on Github