DF818
Tunable Multi-Band Digital Filter

The CECI Model DF818 Tunable Multi-Band Digital Filter is a multirate digital signal processing system that employs dual digital tuners and signal processors to provide variable bandwidth arbitrary transfer function digital filtering.

The DF818 is capable of processing a continuous bandwidth of more than 8 MHz in the range of 50 kHz to 30 MHz using a user specified arbitrary filter shape. The user specifies the filter shape in the frequency domain by defining passband and band reject regions or by specifying the amplitude and phase characteristics of an equalizer or matched filter.

The DF818 front panel includes a high resolution color graphic display to indicate the filter frequency response and the spectrum of the input or output signals. Changes to the output spectrum can be observed while the filter shape is modified on-line.

All filtering parameters can be controlled from the front panel using a cursor and keypad or via optional remote control interfaces. Interfaces for RS-232, GPIB, and Ethernet are available. The settings for up to 30 different system configurations can be permanently stored and recalled. Remote control interfaces also support downloading of filter transfer functions from a personal computer or workstation. These transfer functions may represent matched filters or channel equalizers derived from off-line analysis.

More Sample Displays: Sample 2 | Sample 3 | Sample 4 | Sample 5 | Sample 6 | Sample 7

APPLICATIONS

TECHNICAL DESCRIPTION

The DF818 implements a filter transfer function by fast convolution using FFT lengths of 1024 to 65536. The filtering algorithm permits the specification of arbitrary transfer functions in the frequency domain.

The system allows a trade off of resolution for bandwidth by varying the FFT length and overlap. The selected frequency band is down-converted to baseband. Digital filtering is then performed, and the filtered signal is translated back to the original frequency or a different frequency specified by the user.

The user specifies the desired transfer function by specifying the start and end frequencies of passbands and stopbands and the gain in each of these regions. Passbands may be placed within stopbands and vice versa, allowing the specification of coarse structure first, followed by narrowband modifiers. The control microprocessor then constructs a linear phase (or arbitrary phase) transfer function with smooth transitions between specified bands.

TUNING RANGE

  • Limits: DC to 30 MHz

  • Resolution: < 0.1 Hz

ANALYSIS BANDWIDTH

  • From 2 to 8 MHz

SPECTRAL RESOLUTION

  • From 50 Hz to 7 kHz

FFT SIZES

  • 1024, 4096, 16384, 65536 Complex Input Samples and Spectral Lines

DYNAMIC RANGE

  • Intermodulation + Spurious: -60 dBc

  • Noise Floor: < -65 dBc

INPUT CHARACTERISTICS (RF Input)

  • Coupling: DC or AC (100 Hz cutoff)

  • Sensitivity: 20 mV to 3 V p-p in 1 dB Steps (-30 dBm to +13 dBm)

  • Level Indicators: Low, Normal, Overload

  • Maximum Safe Input: +30 dBm Continuous

  • Impedance: 50 Ohm, Single-ended

OUTPUT CHARACTERISTICS (RF Output)

  • Full Scale: 1 V p-p

  • Impedance: 50 Ohm, Single-ended

FRONT PANEL DISPLAY CHARACTERISTICS

  • Type: Color LCD

  • Resolution: 640 x 480 pixels

  • Pre-filter Spectrum

  • Filter Shape

  • Post-filter Spectrum

  • Relative Phase

  • Alphanumeric

FREQUENCY SELECTION
  • Keypad and Vernier Trackball

FILTER PARAMETER STORAGE/RETRIEVAL

  • Up to 30 Complete Configurations
  • Long Term Non-Volatile Storage

PHYSICAL CHARACTERISTICS

  • Dimensions: 17" W x 7" H x 20" D
  • Weight: 35 lb.
  • Power: 115 VAC, 47-63 Hz
  • Operating Temp: 0 to +50 C
  • Storage Temp: -20 to +70 C

OPTIONS SIGNAL INTERFACE MODULES

  • Analog and Digital RF Input (Real)
  • Analog and Digital Baseband Output (Complex)
  • Analog and Digital RF Output (Real)

REMOTE CONTROL

  • GPIB, RS-232, Ethernet
  • All Front Panel Controls
  • Filter Amplitude and Phase Function Loading

REMOTE DISPLAY

  • VGA Compatible, Analog

RGB REAL-TIME SPECTRUM ANALYZER

  • Display Mode: Input Power Spectrum
  • Real-time Bandwidth: 8 MHz Maximum
  • Outputs: Digital Power Spectrum Digital Complex Spectrum

Contact CECI | About CECI

Copyright © 2003 Creative Engineering Concepts, Inc.