DFP2 Digital Filter Package

Example of a high pass filter, used to block power supply hum (60 Hz-frequency component) from a higher frequency signal. The cutoff frequency is set to 1 kHz with a narrow transition region of 1% (very steep). Channel 2 displays the unfiltered signal, while B shows the filtered result. The FFT analysis of the signal before and after the filtration is displayed by traces A and C. Notice the disappearance of the 60 Hz component.

Leading Features

• Wide variety of FIR digital filters:

Low Pass
High Pass
Band Pass
Band Stop
Raised Cosine
Raised Root Cosine
Gaussian
User Designed

FIR filters are all Butterworth type

• Wide variety of IIR Digital Filters:

  Low  Pass
  High Pass
  Band Pass
  Band Stop
  User Designed

  All available with Butterworth, Chebyshev or Inverse Chebyshev, or Bessel type.

• Basic Setup:

3dB frequency/width
Center Frequency
Rolloff/decade
Corner Frequency (Cosine Beta)
Corner Frequency (Gaussian Beta)

• Advanced Setup:

Low Frequency Cutoff
High Frequency Cutoff
Transition Width
Stop Band Attenuation
Pass Band Ripple
Number of Taps

• Can be coupled with other LeCroy analysis packages:

Advanced Math Package	(XMATH)
Disk Drive Measurements	(DDM2)
Jitter and Timing Analysis	(JTA2)
Serial Mask Package	(SDM)

LeCroy’s Digital Filter Package (DFP2) implements a set of linear-phase Finite Impulse Response (FIR) filters and IIR filters. It enhances your ability to examine important signal components by filtering out undesired spectral components such as noise. With the custom design feature, you can reconstruct corrupted signals by applying matched (mirror) filters to compensate for known distortions.

DFP2 eliminates the need to transfer acquired data to a PC for analysis. It can be used for circuit design: you can view the effects of different filters on your data before implementing the actual filters into your designs. If more complex filters are desired, filters can be cascaded, or new, custom-designed filters can be defined.

Custom filters can be designed and the coefficients loaded into the scope using a spreadsheet.

Applications
The DFP2 option has a broad range of applications:  

System Identification

• Telephone channel identification
• Modem echo cancellation

• CDMA interference
• Adaptive CDMA receiver
• Spectral whitening

• ECG noise control
• Background noise

• Sample applications include datacom, telecom, disk drive, and optical recording analysis, for an accurate RF signal detection.

• Sample applications include medical equipment such as ECG monitors, where the dominant ripple at 50/60Hz is rejected, leaving the low-energy biological signals intact.
• For digital troubleshooting, the inherent frequency of the switched power supply is blocked, revealing power lines voltage drop and glitches caused by the system clock oscillator.

• Sample applications include radio channel identification, broadband transmission, ADSL, and clock generators (eliminating the central frequency, displaying harmonics only), and telecom (jitter measurement over a selected frequency range).

• Some applications include disk drive and optical recording (emulation of the slicing function).

Raised cosine, raised root cosine, and Gaussian filters are low pass filters with unique shapes.

• Raised cosine is one of a class of filters used to minimize intersymbol interference. The time domain impulse response crosses zero at all multiples greater than one of the bit period. Harmonies of the modulation frequencies are therefore canceled.
• Applying raised root cosine twice (or, for example, at the sending and receiving end of a signal) produces the same result as a raised cosine filter.
• Applications include wireless cellular communications such as WCDMA, datacom, telecom, disk drive, and optical drive analysis.

The custom-designed filter feature lets you design filters with virtually any desired characteristics. Typical applications may include areas such as matched (or mirror) filters and modem echo cancellation.

The required custom filter can be designed with a digital filter design or math package such as MATLAB^® or Mathcad^®.