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PRECISION 28000 Signal Conditioning System
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28000 System Filter CharacteristicsYou want your analog data to come clean before digital conversion. The 28000 System has a variety of high-performance filter characteristics available for HP, LP or BP Precision filtering, as well as, traditional filter types such as Butterworth and Bessel characteristics and others. Our new choice of LP4FP 4-pole or LP8FP 8-pole flat/pulse low-pass filters provide the user with the versatility to address applications in either the time or frequency domain and are available on many 28000 card models. Frequencies can range as high as 204.6 kHz with fixed frequency choices for economy.
BE? Bessel 4, 6, or 8-Pole Low-Pass Filter BU? Butterworth 4, 6, or 8-Pole Low-Pass Filter EH4 4-Pole, 4-Zero Equiripple High-Pass Filter EH8 8-Pole, 8-Zero Equiripple High-Pass Filter EL4 4-Pole, 4-Zero Equiripple Low-Pass Filter EL8 8-Pole, 8-Zero Equiripple Low-Pass Filter LP1 6-Pole, 6-Zero Elliptic Low-Pass Filter LP4F & LP4P 4-Pole, 4-Zero Low-Pass Filters LP8F & LP8P 8-Pole, 8-Zero Low-Pass Filters TD4 4-Pole, 4-Zero Time Delay Filter (Linear Phase/Flat Time Delay) TD6A 6-Pole, 4-Zero & TD6B 6-Pole, 6-Zero Time Delay Filter (Linear Phase/Flat Time Delay) TD8A 8-Pole, 6-Zero & TD8B 8-Pole, 8-Zero Time Delay Filter (Linear Phase/Flat Time Delay) BE? Bessel 4, 6, or 8-Pole Low-Pass FilterThe Bessel family of low-pass filters provides linear phase and thus delays all frequency components in the pass-band of the filter equally in time. The Bessel characteristic has an amplitude response that decreases monotonically with increasing frequency. As a consequence of the Bessel’s linear phase property, the filter exhibits broadly rounded amplitude response characteristics. As with any “all pole” filter, the Bessel reaches a terminal attenuation slope of 6 n dB/octave where n is the number of poles. The BE? family of low-pass filters have the advantage of extremely low phase distortion attributable to their linear phase characteristics. In response to a step input, the Bessel has little overshoot and settles very rapidly. The amplitude response of the Bessel family of low-pass filters are inferior to most other common characteristics. The Bessel is a good choice for applications where linear phase (i.e., constant time delay) and fine transient response are critical while a rounded amplitude response can be tolerated. Download specifications from the Reference Library BU? Butterworth 4, 6, or 8-Pole Low-Pass FilterThe Butterworth family of low-pass filters is formulated by uniformly placing poles on the unit circle about the origin in the left half of the complex plane. The
Butterworth characteristic exhibits no ripple in the pass-band. The Butterworth low-pass filter has moderate amounts of phase distortion due to its non-linear phase behavior. Response to a step function results in large overshoot and long settling times. When compared to an Elliptical filter of the same order, the Butterworth delivers inferior amplitude response and comparable phase and step response. A tightly controlled Butterworth filter will give excellent flatness in the lower portion of the pass-band, often making it a satisfactory choice for amplitude critical applications such as spectral analysis. Download specifications from the Reference Library
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The EH4 4-pole, 4-zero High-Pass filter has 0.1 dB p-p
pass-band ripple and 80 dB stop-band attenuation at 0.212 times the cutoff
frequency (Fc). The EH4 is a good choice for eliminating low frequency noise or
as a companion with a low-pass filter for moderate Q band-pass filtering. The EH4 has characteristics comparable to a 6-pole Butterworth
yet only requires 4-poles and 4-zeros to implement. When compared to a 6-pole
Butterworth, the EH4 provides more useable bandwidth (–0.1 dB frequency is 1.209
versus 1.370 for a 6-pole Butterworth) and identical rolloff characteristics to
the –80 dB stop-band. Cascade an EH4 with an EL4 to form a band-pass filter. If the
filters are set with the –0.1 dB frequencies overlapping, the resulting
band-pass filter will have 0.2 dB of insertion loss and will provide more than
80 dB of attenuation below 0.212 Fc and 4.72 Fc. Q’s of over 2.6 are attainable. Download specifications from the Reference Library EH8: 8 Pole, 8 Zero Equiripple High Pass FilterThe EH8 8-pole, 8-zero High-Pass filter has 0.1 dB p-p pass-band ripple and 90 dB stop-band attenuation at 0.559 times the cutoff frequency (Fc). The sharp transition of the EH8 makes it an ideal filter for rejecting interfering signals that are close to the pass-band. The EH8 uses a unique equiripple pass-band and stopband response to achieve complex pole pairs with lower Q’s. The result is a very selective filter with less sensitivity to component tolerance and lower spectral noise, especially near the cutoff frequency. Cascade the EH8 with an EL8 and form a very sharp bandpass filter. If they are set to the same cutoff frequency, the band-pass filter will have 0.2 dB insertion loss and will provide more than 90 dB attenuation below 0.56Fc and 1.79Fc. Q’s of over 8 are attainable. Download specifications from the Reference Library EL4 4-Pole, 4-Zero Equiripple Low-Pass FilterThe EL4 4-pole, 4-zero low-pass filter has 0.1 dB p-p pass-band ripple and 80 dB stop-band attenuation at 4.719 times the cutoff frequency (Fc). The EL4 is a good choice for eliminating high frequency noise or for less stringent anti-aliasing applications where a moderately high sampling ratio is available. The EL4 has characteristics comparable to a 6-pole Butterworth yet only requires 4 poles and 4 zeros to implement. When compared to a 6-pole Butterworth, the EL4 provides more useable bandwidth (–0.1 dB frequency is 0.83 Fc versus only 0.73 Fc for a 6-pole Butterworth) and identical rolloff characteristics to the –80 dB stop-band. The EL4 has moderate amounts of phase distortion due to its non-linear phase characteristics. The EL4 overshoots 13.4% in response to a step function input and requires 2.59/Fc seconds for the output to settle to 1%. Cascade an EH4 with an EL4 to form a band-pass filter. If the filters are set with the –0.1 dB frequencies overlapping, the resulting band-pass filter will have 0.2 dB of insertion loss and will provide more than 80 dB of attenuation below 0.212Fc and 4.72Fc. Q’s of over 2.6 are attainable. Download specifications from the Reference Library EL8 8-Pole, 8-Zero Equiripple Low-Pass FilterThe EL8 8-pole, 8-zero low-pass filter has 0.1 dB p-p pass-band ripple and 90 dB stop-band attenuation at 1.788 times the cutoff frequency. The sharp transition of the EL8 makes it an ideal filter for rejecting interfering signals that are close to the pass-band. The EL8 uses a unique equiripple pass-band and stop-band response to achieve a transfer function with complex pole pairs having lower Q’s. The result is a very selective filter with less sensitivity to component tolerance and lower spectral noise, especially near the cutoff frequency. For anti-aliasing applications, the EL8’s fast transition provides more usable bandwidth, more attenuation of aliases and operation at a lower sampling frequency than can be attained with conventional filters. Phase and amplitude match for the EL8 are specified throughout its pass-band from DC to the cutoff frequency. 90 dB attenuation of aliases and no more than 0.1 dB attenuation of the signal is obtained at a sampling frequency of 2.79 times the cutoff frequency. Download specifications from the Reference Library LP1 6-Pole, 6-Zero Elliptic Low-Pass FilterThe LP1 6-pole, 6-zero Elliptic (Cauer) low-pass filter has 0.1 dB p-p pass-band ripple, 80.07 dB minimum stop-band attenuation, and 80 dB/octave attenuation slope. Of all filters with the same pass-band ripple, stop-band attenuation, and complexity (number of poles and zeros), the Cauer filter has the fastest transition from pass-band to stop-band making it ideal for rejecting interfering signals close to the pass-band. For anti-alias applications, the LP1’s fast transition provides more usable bandwidth, more attenuation of aliases, and a lower sampling frequency than can be obtained with more conventional filters. With sampling frequency set to three times the highest frequency of interest and the cutoff frequency set to 1.081 times the highest frequency of interest, the LP1 will provide 80 dB attenuation of all aliases with no more than 0.1 dB attenuation of the signal. The LP1 can be cascaded with an HP1 to form a sharp band-pass filter, or it can be used with an HP1 to form a band-reject filter by driving their inputs in parallel and adding their outputs. Download specifications from the Reference Library LP4F & LP4P 4-Pole, 4-Zero Low-Pass FiltersThe LP4F and LP4P 4-pole, 4-zero low-pass filters together provide the user with the versatility to address applications in either the time or frequency domain. The choice of LP4F or LP4P is programmable in most Precision Filters products that offer this filter characteristic. The LP4F is specified to have excellent pass-band flatness and sharp roll-off characteristics. The pass-band characteristic is nearly identical to a 4-pole Butterworth yet the LP4F has a much sharper roll-off. The LP4F is a good choice for applications such as spectral analysis and for less stringent anti-aliasing applications where a moderately high sampling ratio is available. The LP4P has excellent transient response and phase linearity making it a good filter for time domain applications including transient (shock) measurements and time domain waveform analysis. The LP4P has frequency and time domain characteristics superior to the 4-pole Bessel filter. Like the Bessel, the LP4P has a broadly rounded amplitude response that is a consequence of the LP4P’s linear phase property. Cascade an HP4F with an LP4F to form a band-pass filter. If the filters are set with the –0.1 dB frequencies overlapping, the resulting band-pass filter will have 0.2 dB of insertion loss and will provide more than 80 dB of attenuation below 0.107 Fc and above 9.364 Fc. Download specifications from the Reference Library LP8F & LP8P 8-Pole, 8-Zero Low-Pass FiltersThe LP8F and LP8P 8-pole, 8-zero low-Pass filters together provide the user with the versatility to address applications in either the time or frequency domain. The choice of LP8F or LP8P is programmable in most Precision Filters products that offer this filter characteristic. The LP8F is specified to have outstanding pass-band flatness and very sharp roll-off characteristics. The pass-band characteristic is nearly identical to an 8-pole Butterworth yet the LP8F has a much sharper roll-off. The LP8F is a good choice as an anti-aliasing filter and for applications such as spectral analysis. The LP8P has excellent transient response and phase linearity making it an ideal filter for time domain applications including transient (shock) measurements and time domain waveform analysis. The LP8P has frequency domain characteristics superior to the 8-pole Bessel filter. Like the Bessel, the LP8P has a broadly rounded amplitude response that is a consequence of the LP8P’s linear phase property. Cascade an HP8F with an LP8F to form a band-pass filter. If the filters are set with the –0.1 dB frequencies overlapping, the resulting band-pass filter will have 0.2 dB of insertion loss and will provide more than 80 dB of attenuation below 0.487 Fc and above 2.05 Fc. Download specifications from the Reference Library
TD4 4-Pole, 4 Zero-Time Delay Filter
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Reference The following Specifications BE? Specifications BU? Specifications EH4 Specifications EH8 Specifications EL4 Specifications EL8 Specifications LP1 Specifications LP4F & LP4P Specifications LP8F & LP8P Specifications TD4 Specifications TD6 Specifications TD8 Specifications |
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