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Device Overview

The UBX daughterboard is a full-duplex wideband transceiver that covers frequencies from 10 MHz to 6 GHz. Coherent and phase-aligned operation across multiple UBX daughterboards on USRP X Series motherboards enables users to explore MIMO and direction finding applications. The UBX daughterboard is supported by the USRP Hardware Driver™ (UHD) software API for seamless integration into existing applications.

The UBX is capable of phase coherent operation, and therefore is suitable for MIMO and Phased Array applications, on the X Series. Additionally this capability is only available on the X Series devices.

Key Features

  • Frequency Range: 10 MHz - 6 GHz
  • Versions: 40MHz / 160MHz
  • RF shielding
  • Full duplex operation with independent TX and RX frequencies
  • Synthesizer synchronization for applications requiring coherent or
    phase-aligned operation, supported on USRP X Series motherboards only
Product ubx 40.png
Product ubx 160.png

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 UBX 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


  • UBX: 40 MHz, RX & TX
  • UBX-160: 160 MHz, RX & TX


  • lo_locked: boolean for LO lock state


  • LOCK: Synthesizer Lock Detect
  • TX/RX TXD: Transmitting on TX/RX antenna port
  • TX/RX RXD: Receiving on TX/RX antenna port
  • RX2 RXD: Receiving on RX2 antenna port

RF Specifications

Freq Range

  • 10MHz - 6GHz

Noise Figure

  • 10 MHz - 500 MHz: 3 - 4 dB
  • 500 MHz - 1.5 GHz: 2 - 3 dB
  • 1.5GHz - 6GHz: 4 - 10 dB

RX IIP3 (Max)

  • 10 MHz - 6 GHz: 8 - 9 dBm

RX IQ Imbalance

  • 10 MHz - 6 GHz: < -30dBc

TX Power (Max)

  • 10 MHz - 3 GHz: 20 dBm
  • 3 - 6 GHz: 8 - 20 dBm


  • 10 - 500 MHz: 41 dBm
  • 0.5 - 3 GHz: 36 dBm
  • 3 - 6 GHz: 26 dBm - 36 dBm

TX IQ Imbalance

  • 10 MHz - 6 GHz: < -30 dBc

Note: The UBX 160 transmitter path has 160 MHz of bandwidth throughout the full frequency range of the device; the receiver path has 84 MHz of bandwidth for center frequencies from 10 MHz to 500 MHz.

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 UBX is -15 dBm.

RF Performance Data

Hardware Specifications

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


  • Current Hardware Revision: 2
  • Minimum version of UHD required for UBX rev-1: 3.8.2
  • Minimum version of UHD required for UBX rev-2: 3.9.5


  • Current Hardware Revision: 2
  • Minimum version of UHD required for UBX rev-1: 3.8.2
  • Minimum version of UHD required for UBX rev-2: 3.9.5

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 UBX daughterboard is capable of phase-synchronous operation, and is recommended for phase-coherent applications. The SBX and TwinRX daughterboards are also recommended for phase-coherent applications.

If you are operating the UBX at frequencies below 1 GHz and need phase synchronization, then it is necessary to select a 20 MHz daughterboard clock rate, instead of using the default 50 MHz rate. Note that this is only required for phase synchronization below 1 GHz. The UBX can still operate below 1 GHz without setting this lower daughterboard clock rate, but it will operate without any phase synchronization capability.

If you're using a UHD program, then you can specify the lower daughterboard clock rate on the command line of the program, with --args="dboard_clock_rate=20e6".

If you're using the UHD API from a C++ program, then you can include "dboard_clock_rate=20e6" in the device arguments parameter when first invoking multi_usrp::make().

If you're using GNU Radio, then you can add "dboard_clock_rate=20e6" to the "Device Arguments" field of the properties for the UHD Sink and UHD Source blocks.



UBX Schematics

Key Component Datasheets

Part Number Description Schematic ID (Page)
MAX2871 Fractional/Integer-N Synthesizer/VCO U3 (3); U9 (5); U19 (7); U23 (9)
ADL5375-05 Quadrature Modulator U22 (8)
LFCN-2250+ Low Pass Filter F1 (3); F24 (7); F34, F35 (10)
LTC5510 Active Mixer U15 (6)
LFCN-490+ Low Pass Filter F12 (5); F15 (6); F26 (7); F31 (9); F33, F36 (10)
NBB-400 Amplifier U13 (6); U30 (11)
PHA-1+ Amplifier U31 (11)
ADA4927-2 Differential ADC Driver U6 (4)
ADL5380 Quadrature Demodulator U8 (4)
MGA-62563 Low Noise Amplifier U36 (11)
LFCN-1700+ Low Pass Filter F41 (11)
VMMK-3603 Low Noise Amplifier U34 (11)
LFCN-2600+ Low Pass Filter F14, F17 (6)
855916 SAW Filter F16 (6)
LTC5510 Active Mixer U15 (6); U28 (10)
LFCN-2600+ Low Pass Filter F14, F17 (10)
TCM1-63AX+ RF Transformer T1 (3); T2, T3 (4); T7 (8)
ADA4927-2 Differential ADC Driver U6 (4)
AD8591 Operational Amplifiers U7 (4)
ADL5380 Quadrature Demodulator U8 (4)
HMC624ALP4E ATTENUATOR U16 (6); U29 (10)
LFCN-800+ Low Pass Filter F2 (3); F25 (7)
ADP7104-3.3 CMOS LDO U4, U5 (3); U10, U11 (5); U20, U21 (7); U24, U25 (9); U48 (13)
ADL5375-05 Quadrature Modulator U22 (8)
LTC5510 Active Mixer U28 (10)
24LC024 EEPROM U38, U39 (12)
ADP7104-5.0 CMOS LDO U41, U42, U43, U44, U45, U46, U47 (13)
ZXTC2062E6 TRANSISTORS Q2, Q3, Q4, Q5 (13)

Mechanical Information


RF Connectors

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



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Certificate of Volatility


Important Notes

  • A larger 24W (6V, 4A) power supply is required when using a UBX-40 daughterboard and integrated GPS Disciplined Oscillator accessory together in a USRP2, USRP N200, or USRP N210 device.
  • The UBX-160 transmitter path has 160 MHz of bandwidth throughout the full frequency range of the device; the receiver path has 84 MHz of bandwidth for center frequencies from 10 MHz to 500 MHz.


FPGA Resources

UHD Stable Binaries

UHD Source Code on Github