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Connect with Robin Hassell at ASMS 2017, Indianapolis, USA, June 4 – 8

Robin Hassell, Business Manager for High-Speed Digitizer Technology will introduce you to the latest developments on Mass Spectrometry (MS-TOF) applications and PCIe digitizers.

For more information about the exhibition: https://www.asms.org/conferences/annual-conference/annual-conference-homepage

Robin Hassell’s contact details: +1 (940) 602 0860 e.mail: robin_hassell@keysight.com

 

 

Network with Robin Hassell at Photonics West 2017, San Francisco, California, USA, 28 January – 2 February

Robin Hassell, Business Manager for High-Speed Digitizer Technology will introduce you to the latest developments on Swept-Source (SS-OCT) application options and PCIe digitizers.

For more information about the exhibition: http://spie.org/conferences-and-exhibitions/photonics-west

Robin Hassell’s contact details: +1 (940) 602 0860 e.mail: robin_hassell@keysight.com

 

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

In the following example, we capture 2 channels simultaneously at 1 GS/s with signal at 1.8 GHz center frequency  and 200 MHz IBW  

Sampling and compliancy with Nyquist zones

– The IBW is in 4th Nyquist band (between 1.5 GHz and 2 GHz) and doesn’t cross over between Nyquist zones

– For signal in 4th Nyquist band, sampling at 1 GHz Fs causes an aliased signal in negative frequency domain . This aliased signal is then down-converted in baseband

Filtering requirements

– It is recommended to add a pass-band filter at the digitizer input, selecting the signal IBW (1.7 GHz to 1.9 GHz)

Local Oscillator

– For down conversion, LO would be set at signal center frequency 1.8 GHz  (physically the signal is aliased at -200 MHz, thus LO is at -200MHz).

IBW and data rate

– The signal 200 MHz IBW  requires to select higher decimated sampling rate 250 MS/s, resulting in a 1000 MB/s data rate

Multi-channel streaming

– Using U5303A-CB1: a single digitizer can manage the 2 channels simultaneously since streaming limit is 2.4 GB/s

   – either use two digitizers

   – or a single digitizer with 12-bit mode: this case results in two channels at 700 MB/s per channel with resolution: I – 12 bits, Q – 12 bits

To learn more about our Application Options, please contact us at acquiris_support@keysight.com

 

 

Frequency Analysis Measurements with the New 10-bit PCIe Digitizer

Up to 10 GS/s and more than 2 GHz Instantaneous Bandwidth per Channel

Key Features:

-One channel at 10 GS/s or two channels at 5 GS/s, DC up to 2.5 GHz bandwidth

-Dual full scale range 250 mV and 1 V

-Low noise density, low distortion and optimized frequency response flatness

 

 Our High-Speed Digitizers Team announces capability of more than 2 GHz instantaneous bandwidth on the U5310A 10-bit PCIe high-speed digitizer.

This unique ADC card is designed for frequency analysis such as wireless, telecommunication and spectroscopy applications.

The new U5310A high-speed digitizer features one channel at 10 GS/s or two channels at 5 GS/s, DC up to 2.5 GHz bandwidth and dual full scale range at 250 mV and 1 V.

We developed proprietary ICs for the U5310A. In particular, low noise and low distortion signal conditioning amplifier to drive interleaved ADCs and specific clock distribution to minimize the clock jitter and spurious. Moreover, optimized frequency response flatness provides enhanced measurement accuracy.

“With those proprietary technologies, we provide the unique solution to interleave DC coupled 10-bit ADCs without adding distortion while providing low full scale and wide bandwidth input” said Daniel Frund, Analog and IC Design Manager.”

Here below some examples of frequency analysis measurements:

1) Frequency response (nominal) to a 100 MHz single tone input signal at -1 dBFS, acquired at 5 GS/s, without equalization, and using 1V FSR.

U5310A-Frequency-Response-100 MHz-single tone input signal

 

2) Frequency response (nominal) to a 1.9 GHz single tone input signal at -1dBFS, acquired at 5 GS/s, without equalization, and using 1V FSR.

U5310A-Frequency response-1.9-GHz-single-tone-input-signal-at -1dBFS

 

3) Frequency response (nominal) to a 1.9 GHz single tone input signal at -1dBFS, acquired at 10 GS/s, without equalization, and using 1V FSR.

U5310A-Frequency-response-1.9-GHz-single-tone-input-signal

For more information about High-Speed Digitizers, please contact us at acqiris_support@keysight.com

 

 

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.

 

Definitions:

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

More News about SS-OCT (2/2)

Swept laser source non-linearity and k-clock instability compensation

Swept source OCT lasers are non-linear. This non-linearity must be compensated to improve both resolution and sensitivity.

Non-linearity correction can be done in two ways:

Direct ADC clocking: the ADC capturing the OCT interference is clocked directly with a clock signal that contains the information of the laser source non-linearity.

Digital Resampling: The ADC capturing the OCT interference is clocked at constant sampling period. The digitized OCT interference is digitally non-linearly resampled in a way to compensate the non-linearities computed on the K-clock and acquired with a second ADC channel. K-clock can be easily generated with a Mach-Zehnder interferometer (MZI) connected to the same laser source.

Current solution is based on the resampling approach. If it requires an additional channel, on the other hand, it provides more flexibility, and simpler implementation of the OCT system. For instance, it is not required to generate a “dummy” K-clock out of the source sweep.  Besides, the digital resampling approach offers additional capabilities, such as:

-Compensation of the optical path difference between K-clock and OCT-signal

-Programmable maximum analysis depth. 

U5303A High-Speed Data Acquisition Card for SS-OCT: Product features and specifications 

Image clarity and high-resolution

Acquisition card signal integrity characteristics are critical to guarantee the best image quality. This unique solution offers:

  • A best in class signal noise ratio for a 12 bits resolution digitizer (57-58 dB typical)
  • Improved spurious free dynamic range (SFDR) thanks to x4 (SS2) or x2 (SS1) oversampling interpolation. For instance, with -SS2 option, artefacts are reduced by 14 dB due to interpolation.
  • Better phase stability thanks to accurate synchronization for A-scan triggers
  • SS1 option: ENOB = 9.3 (typical) at 100 MHz
  • SS2 option: ENOB = 9.1 (typical) at 410 MHz

Flexible SS-OCT analysis depth

To allow deep analysis, the system needs a high sampling rate. The new SS2 option doubles the sampling rate from 500 MS/s to 1GS/s, allowing:

-either to double the maximum analysis depth with same A-scan rate.

-or to double the image speed (double A-scan rate), keeping the same analysis depth.

In addition, the maximum analysis depth is programmable by selecting the effective sampling rate of the ADC card.

Key advantages of this approach are:

–           Flexibility from changing the A-scan rate.

–           Independency from K-clock frequency

–           Programmable through variable sampling rate (internal clock from 250 MHz up to 1 GHz).

Fast scan measurement and image restitution

3-D images are very long to acquire. The sustained scan rate is a crucial parameter to minimize unwanted samples movement in ophthalmic applications or to reduce the measurement time when the blood flow is stopped in cardio-vascular applications.

This solution enables up to 200 kHz A-scan rate (i.e. 200’000 A-scan per second), allowing fast acquisition of B-scans. The high scanning speed and fast image restitution are continuously guaranteed and not only for a limited period of time, thanks to:

–           Continuous mode with simultaneous OCT signal acquisition and image data readout (see Signal acquisition sequence)

–           Continuous acquisitions