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Home » news » Streaming and Recording Application Options for the U5303A High-Speed Digitizer (1/2)

Streaming and Recording Application Options for the U5303A High-Speed Digitizer (1/2)

The following application options offer multichannel digital down-converter streaming and recording and enable continuous gapless acquisition, implementing:

– Real time multichannel phase coherent digital down converter

– Data steaming to host

– Multichannel recording to disk all I/Q samples for later analysis

Our solution includes a high-speed digitizer, a configured PC workstation, a data storage system configured and qualified. The system depends on the format PCIe.

Digital Down Conversion (DDC): This is real-time firmware (FPGA code) capability to reduce the amount of data to be transmitted, by selecting a programmable instantaneous bandwidth centered around a programmable center frequency, shifting it down and decimating to a lower sample rate. This firmware capability is operating synchronously on all acquisition channels.

CB1 / CB2 principle

Digital Down Conversion

The digital down converter (DDC) mode of the digitizer allows to convert a digitized real signal centered at a center frequency1 (Fc) to a baseband complex signal. In addition to down conversion, DDC decimates to a lower sampling rate, allowing follow-on signal processing by lower speed processors.

Process in frequency domain

When a signal is acquired by a digitizer, aliased images appear at frequencies depending on sampling rate frequency (Fs) due to sampling and folding-back (See example in Fig.2). The aliased signal in 1st Nyquist zone is used for down-conversion and translated in baseband thanks to Local Oscillator (LO) at configurable center frequency (Fc). Then, digital Low-Pass Filtering (LPF) is used to remove some unwanted aliased signal. The baseband signal is decimated then used for streaming and recording.

Figure: Example of a signal acquisition in 3rd Nyquist zone
Sampling causes initial signal in Instantaneous Bandwidth (IBW) to be aliased–back in 1st Nyquist zone. Then, using LO at Fc, the resulting baseband signal is used for streaming.


CB1 / CB2 usage and guidelines

Filtering of input signal

At sampling, unwanted signal in other Nyquist bands can create unexpected aliased signals in the working bandwidth. This could deteriorate the signal once translated in baseband.

To limit this aliasing effect, it is recommended to add a band-pass filter at the digitizer input. Its bandwidth value should select the signal of interest. The filtering may become mandatory if the signal has several carriers .

Sampling Frequency & Instantaneous Bandwidth

Due to aliasing, the Instantaneous analysis Bandwidth (IBW) of input signal must not overlap on two Nyquist zones —Nyquist zones are limited by frequencies multiples of Fs/2.



Streaming: This is the capability of the digitizer to continuously send data to the controlling host while the acquisition is still running.
Recording: This is the capability of the system to send data continuously from the host to a storage device.

CB1/-CB2/-CB3 application options: These bundle options for the U5303A digitizer provides a real-time digital down-converter (DDC) and I/Q data streaming together with recording capabilities.

Local Oscillator (LO): The DDC uses a programmable Local Oscillator to mix sampled signal with the selected center frequency (Fc).

DPU: The Data Processing Unit(s) inside the digitizer is dedicated to 2 channels and includes the FPGA where the firmware of the -CB1, -CB2 & CB3 options are located.

IBW: The intermediate bandwidth is the signal of interest bandwidth before down conversion.


Related products:

U5303A PCIe 12-bit High-Speed Digitizer

To learn more about our Application Options, please contact us at

About Acqiris SA

On August 1, 2017, Keysight PCIe-based digitizer group became a new company and returned to its original name: Acqiris, a leader in signal acquisition, enriched with the experience of Agilent and Keysight Technologies. The same team of dedicated specialists has been developing high quality signal acquisition products, bringing technical excellence to our customer unique application.

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