UHF-BOX Boxcar Averager

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The UHF-BOX Boxcar Averager is the first fully digital boxcar averager in history opening new perspectives and innovative ways of analyzing non-sinusodial signals with low duty cycles. It operates as a high speed digitizer synchronized to an oscillator and therefore captures every sample without any dead times while rejecting all non-periodic signal components. The LabOne® toolset comprises a Periodic Waveform Analyzer (PWA) that visualizes the averaged signal over a single or multiple periods and allows convenient setting of the averaging windows for the signal and the baseline suppression. The UHF-BOX Boxcar Averager is an option for the UHFLI Lock-in Amplifier and contains 2 independent Boxcar units with one PWA each.

UHF-BOX Key Features

  • 2 Boxcar units
  • 600 MHz repetition rate
  • Baseline suppression
  • Zero acquisition dead time
  • 2 Periodic Waveform Analyzers (PWA)
  • Harmonic analyzer with 512 lines
  • Graphical setting of Boxcar and Baseline windows

UHF-BOX Upgrade and Compatibility

  • Option upgradeable in the field
  • Compatible with all other UHF options

UHF-BOX Applications

  • Pulsed laser spectroscopy
  • THz spectroscopy
  • Asynchronous optical sampling (ASOPS)
  • Synchrotron radiation experiments
  • Electrical pump-and-probe experiments
  • Pulsed radars
  • Fluorescence decay analysis
  • Time-of-flight mass spectroscopy
  • Superconductor magnetic field penetration

UHF-BOX Functional Diagram

Synchronous detection of signals with small duty cycles

Boxcar Averagers (alternative names are gated integrator and boxcar integrator) are designed to recover small duty cycle signals by cutting out only the relevant parts in the time domain. The ratio between the average time when an actual signal is present and the time when only noise is there can be as low as 10-9. Even for less extreme examples it is evident that optimum signal-to-noise cannot be achieved by simply averaging over all samples but can be achieved only by effectively rejecting all noise sources. As the bulk of such experiments is dealing with strictly repetitive signals with a fixed periodicity, the Zurich Instruments Boxcar was designed as a synchronous detection tool. That means it is not based on a point-by-point trigger based extraction but instead uses an internal or external reference frequency and so transfers the measurement into the frame of reference of the actual experiment. As for the lock-in detection also for the Boxcar Averaging synchronous detection rejects all signal components that are not linked to the frequency of interest.

Periodic Waveform Analyzer

For convenient setting of the gating and the baseline windows, the Periodic Waveform Analyzer (PWA) graphically displays an average of the signal where cursors can be used to pick the signal parts that matter. The PWA operates at a sampling rate of 450 MHz and associates every input sample to one of the 1024 available bins depending on the phase of the reference oscillator. One or multiple periods can be displayed over either phase or time. The FFT of the signal reveals all harmonic components present in the signal – a multi-harmonic analyzer. With this tool the user can immediately infer how much signal power is in the individual harmonics. Phase and amplitude of up to 8 of the harmonic components can be measured with the lock-in demodulators.

Baseline suppression

Boxcar averaging is a two-step process. In a first step the mean value of all samples that come to lay within the measurement window are determined and in a second step the mean of these results - over a user-adjustable number of oscillator periods - is calculated. The baseline suppression feature enables background subtraction based on a measurement in a second window within the same period. This keeps the signal constant even if the signal offset changes. In addition, when tuning the reference frequency to half the experiment frequency, subsequent signals that contain ON and OFF type of information, e.g. in pump-probe experiments, can be subtracted.

Multi-channel Boxcar

The multi-channel boxcar supports dual-timebase experiments. This applies for instance to setups where a pulsed laser undergoes a slower modulation of the physical experiment. The multi-channel operation associates the measurement result of the fast pulses to the time bins according to the slow frequency. The result is the deconvoluted time series of the dual-timebase. Asynchronous Optical Sampling (ASOPS) is a prominent example for such experiments where two slightly detuned repetitive laser sources are used in a pump-probe experiment. The Boxcar averager extracts the low duty cycle signal in a first step and then a PWA displays the Boxcar results by associating these results according to the relative phase of the two lasers.

Check for more UHF-BOX product highlights and a discussion of the differences to old-school boxcar models based on analog signal processing.

UHF-BOX Specifications

Old-school boxcar features
signal inputs 2
boxcar averagers 2
signal input bandwidth DC - 600 MHz,
1.5 ns rise time (20% - 80%)
repetition rate External trigger: 100 Hz to 600 MHz
Internal trigger: 1 Hz to 600 MHz
With baseline suppression: <450 MHz
acquisition dead time 0 (repetition rate < 450 MHz)
1.6 ns (repetition rate > 450 MHz)
input sensitivity range 10 mV to 1.5 V 1
boxcar gain 1,000,000 V/V 1
input noise 4 nV/√Hz, corresponding to 100 µV at full bandwidth
integrator gating time 556 ps to 9.3 ms 2, 3
integrator gating delay 360 degrees full range, very high resolution
boxcar averaging length 1 to 1 M averaged integrator results
boxcar output 1 to 512 updates per averaging length, up to 2.5 MS/s
Digital boxcar features
input sampling 12 bit, 1.8 GSa/s
periodic waveform analyzers 2
data bins for periodic waveform analyzer 1024
data bins for multi-channel boxcar 1024
harmonic analyzer, simultaneously measured harmonic frequencies 512
advanced operation modes baseline suppression
fully differential measurement
multi-channel boxcar

1 legacy specification, mentioned to allow comparison with old-school boxcars
2 spec depends on the repetition rate, only sensible combinations provide a useful result
3 the performance is conditioned by the 600 MHz analog input filters

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