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Delay Equalized Sharp Cutoff Lowpass

Custom Built LC Filters - 1 KHz to 250 MHz
± .25dB MAXIMUM RIPPLE—2dB MAXIMUM INSERTION LOSS
MAXIMUM DELAY VARIATION +/-3% TO - .25dB FREQUENCY
descolp

The Allen Avionics DELAY EQUALIZED SHARP CUT-OFF LOWPASS FILTERS tabulated on this page are the result of many years of experience in the use of specialized computer programs for the design and optimization of Delay Equalized Filters. By using modern digital computers, the composite behavior of the filter and equalizer are optimized to yield the ultimate in both amplitude and delay response.

This type of filter is ideally suited for use as an Anti-Aliasing Filter in analog to digital conversion. When used as a Post-Aliasing Filter in digital processing applications, the passband can be shaped to correct for sin x/x amplitude distortion.

The filters tabulated below represent a widely used group. However, many other combinations of stopband ratio, impedance, delay distortion and size are possible. Two stopband ratios are listed in the table below, 1.22 @ 45dB and 1.32 @ 60dB.

Units normally supplied in metal cans for printed circuit mounting. SMA connectors same size. BNC connectors may require larger cans.

Amplitude, phase and/or delay matching between filters is also available.

CALL FACTORY FOR SPECIAL SIZES AND DELIVERY INFORMATION.

ORDER ANY CUT-OFF FREQUENCY FROM 1KHz TO 250MHz. INTERPOLATION BETWEEN TABULATED DATA ALLOWABLE

Click here for mechanical specs

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Normalized Plot of Amplitude & Delay Response of Delay Equalized Lowpass Filter

A = -.25dB Frequency
B = -3dB Frequency
C = -45dB Frequency or -60dB

Stopband Ratio #1 = 1.22 @ 45dB      Delay (D) = 25.37
Stopband Radio #2 = 1.32 @ 60dB    Delay (D) = 25.03

APPROXIMATE PASSBAND DELAY (seconds)=
Delay (D)
2 x π  x Frequency A(Hz)
 
Delay Equalized Sharp Cutoff Lowpass Filters
Maximum -.25dB Cut-Off Frequency (Last point that delay flatness Is specified)

(Graph location A)

 Maximum 3dB Attenuation Frequency (Graph location B)

B = 1.14 x A

 Attenuation Frequency Graph Location C Impedance Range (Ohms) Approximate Passband Delay Micro-Seconds Standard Size Inches "Space-Saving"
Size Inches
45dB Ratio #1 C = 1.22 x A 60dB Ratio #2 C = 1.32 x A Ratio #1 Ratio #2
1 .0 KHz 1.14 KHz 1.22 KHz 1 .32 KHz 500-2.5K 4038 3984 6 x 3 x 1-1/4 --
2.5 KHz 2.85 KHz 3.05 KHz 3.30 KHz 500-2.5K 1615 1539 6 x 3 x 1-1/4 --
5.0 KHz 5.70 KHz 6.10 KHz 6.60 KHz 500-2.5K 808 797 6 x 3 x 1-1/4 --
10.0 KHz 1 1 .40 KHz 12.22 KHz 13.20 KHz 500-2.5K 404 398 6 x 3 x 1-1/4 5 x 2 x1-1/4
25.0 KHz 28.50 KHz 30.50 KHz 33.00 KHz 100-1. OK 162 159 5 x 3 x 1-1/4 5 x 2 x1-1/4
50.0 KHz 57.00 KHz 61.00 KHz 66.00 KHz 50-600 81 79 5 x 3 x 1-1/4 5 x 2 x1-1/4
100.0 KHz 114.00 KHz 122.00 KHz 132.00 KHz 50-200 40 39 5 x 2 x 1-1/4 4 x 2 x1-1/4
250.0 KHz 285.00 KHz 305.00 KHz 330.00 KHz 50-100 16 15 5 x 2 x 1-1/4 4 x 2 x1-1/4
500.0 KHz 570.00 KHz 610.00 KHz 660.00 KHz 50-100 8.08 7.96 5 x 2 x 1-1/4 4 x 2 x1-1/4
1.0 MHz 1.14 MHz 1.22 MHz 1.32 MHz 50-75 4.04 3.98 5 x 2 x 1-1/4 4 x 2 x1-1/4
2.5 MHz 2.85 MHz 3.05 MHz 3.30 MHz 50-75 1.62 1.59 5 x 2 x 1-1/4 4 x 2 x1-1/4
5.0 MHz 5.70 MHz 6.10 MHz 6.60 MHz 50-75 .81 .79 5 x 2 x 1-1/4 4 x 2 x1-1/4
7.5 MHz 8.55 MHz 9.15 MHz 9.90 MHz 50-75 .537 .531 5 x 2 x 1-1/4 4 x 2 x1-1/4
10.0 MHz 11 .40 MHz 12.20 MHz 13.20 MHz 50-75 .404 .398 5 x 2 x 1-1/4 4 x 2 x1-1/4
12.5 MHz 14.25 MHz 15.25 MHz 16.50 MHz 50-75 .322 .318 5 x 2 x 1-1/4 4 x 2 x1-1/4
15.0 MHz 17.10 MHz 18.30 MHz 19.80 MHz 50-75 .268 .264 5 x 2 x 1-1/4 4 x 2 x1-1/4
17.5 MHz 19.95 MHz 21.35 MHz 23.10 MHz 50-75 .230 .227 5 x 2 x 1-1/4 4 x- 1-1/2  x 1-1/4
20 MHz 22.80 MHz 24.40 MHz 26.40 MHz 50-75 .202 .199 5 x 2 x 1-1/4 4 x- 1-1/2  x 1-1/4
25 MHz 28.50 MHz 30.50 MHz 33.00 MHz 50-75 .162 .159 5 x 2 x 1-1/4 4 x- 1-1/2  x 1-1/4
30 MHz 34.20 MHz 36.60 MHz 39.60 MHz 50-75 .134 .132 5 x 2 x 1-1/4 4 x- 1-1/2  x 1-1/4
35MHz 39.90 MHz 42.70 MHz 46.20 MHz 50 .115 .113 5 x 2 x 1-1/4 4 x- 1-1/2  x 1-1/4
40MHz 45.60 MHz 48.80 MHz 52.80 MHz 50 .100 .099 5 x 2 x 1-1/4 4 x- 1-1/2  x 1-1/4
45MHz 51.30 MHz 54.90 MHz 59.40 MHz 50 .090