3Hz to 25.6MHz
3-Channel LP/HP/BP/BR
Butterworth and Bessel
GPIB/Manual
--------------------------- Tunable Active Filter
Features Frequency
Range: 3Hz to 25.6MHz
Bessel/Butterworth
Attenuation Slope: 24dB/Octave
Input/Output Gain
Noise: Typically <250µV referred to input
Remote Control: GPIB
Options 020:
Lower frequency cutoff range to
0.3Hz to 200kHz
for channels 1 and 2 only. Rack
Mount Kit: Part No. RK-37, permits installation of the Model 3945 into
a standard 19" rack spacing. Extended 1 Year Warranty: Part No. EW3945.
Related
Models 3900 - LP - 1Hz to 99kHz - 2-Ch Elliptical 3901 - LP/HP/BP/BR - 1Hz to 99kHz - 2-Ch Elliptical 3940 - LP/HP/BP/BR - 3Hz to
2MHz - 2-Ch Butterworth & Bessel 3944 - LP/HP/BP/BR - 3Hz to
2MHz - 4-Ch Butterworth & Bessel
> 3945 - LP/HP/BP/BR - 3Hz to 25.6MHz - 3-Ch
Butterworth & Bessel 3955 - LP - 170Hz to 25.6MHz
- 2-Ch Butterworth or Bessel 3988 - LP/HP/BP/BR - 0.03Hz
to 1MHz - 2-Ch Butterworth & Bessel
DESCRIPTION The Krohn-Hite Model
3945 programmable filter provides one Butterworth channel of low-pass, tunable
over the range from 170Hz to 25.6MHz; and two independent Butterworth or Bessel
channels of low-pass, high-pass or bypass, one channel of band-pass or band-reject,
tunable over the range from 3Hz to 2MHz.
The 3945 has been
specifically designed for applications requiring high frequency band-pass filtering.
The high cutoff may be set to any frequency between 170Hz and 10MHz, and the
lower cutoff to any frequency between 3Hz and 2MHz.
50MHz LOW-NOISE AMPLIFIER
One channel
of the 3945 can operate as a low-noise amplifier, bypassing the filter, delivering
a bandwidth of 50MHz and gains up to 46dB. This is useful to users wanting to
increase the gain of the signal and improve signal-to-noise ratio before filtering.
The other two channels of the 3945 furnish Bessel or Butterworth transfer functions
and can be programmed to operate as two low-pass, high-pass, one band-pass or
band-reject filter with gains to 40dB per channel.
NON-VOLATILE MEMORY The 3945 offers
99 groups of non-volatile memory for storage of front panel set-ups, which are
stored in battery-backed CMOS. Set-ups can be recalled with a simple command.
Self-test diagnostics occur upon power-up insuring that all internal memory
is operating properly. If a failure occurs, the display will indicate which
ROM or RAM has failed.
APPLICATIONS The 3945 can provide
filtering for many applications such as: high frequency anti-aliasing for digital
signal processing, EMI testing, video recording and many more. The Model 3945
has been carefully designed with the user in mind, providing ease of operation,
reliability and price competitiveness.
SPECIFICATIONS
FUNCTION Channel 1.1
and 1.2: Two independent channels of low-pass, high-pass or bypass; one
channel of band-pass or band-reject. Channel 2.1: One low-pass filter channel or amplified bypass.
CHANNELS 1.1 AND 1.2 FILTER
CHARACTERISTICS Type:
4-pole Butterworth (maximally flat) or Bessel (linear phase). Attenuation Slope: 24dB/octave per channel. Tunable Frequency Range (fc): 3Hz to 2MHz. Frequency Resolution: 1Hz from 3Hz to 1kHz; 10Hz to 2kHz; 100Hz to 100kHz;
1kHz to 1MHz; 10kHz to 2MHz. Cutoff Frequency Accuracy (fc): ±2% or least
significant digit (which ever is greater) 20Hz to 500kHz; ±5% to 2MHz. Relative Gain at fc: Butterworth, –3dB; Bessel,
–7.58dB. Bandwidth: dc to fc, dc coupled; 0.2Hz to fc, ac
coupled (low-pass); fc to 10MHz (high-pass). Passband Response (0dB, Input/ Output gain): ±0.5dB to 2MHz. Stopband Attenuation: >80dB. Harmonic Distortion: –80dB at 1kHz at 1Vrms. Noise (referred to input): <200µV with 2MHz bandwidth detector.
Input:
Pre-Filter Gain: 0dB or 20dB; ±0.2dB.
Coupling: ac or dc.
Impedance: 1M ohm in parallel with 100pf.
Maximum Signal (at 0dB gain): ±4.5V peak at fc <1MHz; ±4V peak at 2MHz.
Maximum DC Blocking Voltage: ±200V in ac coupled mode. Output:
Post-Filter Gain: 0dB or 20dB; ±0.2dB.
Impedance: 50 ohms.
Maximum Voltage: ±6.5V peak into ³500 ohms; ±1.3V peak into ³50 ohms.
Maximum Current: ±25mA.
DC Level: Adjustable to zero.
DC Stability: ±0.5mV/°C typical; ±1mV/°C max.
CHANNEL 2.1
FILTER CHARACTERISTICS Filter Type: 4-Pole, Butterworth,
low-pass. Attenuation Slope: 24dB/Octave. Tunable Cutoff Frequency Range: 170Hz to 25.6MHz. Frequency Resolution: 10Hz from 170Hz to 2.56kHz; 100Hz from 2.6kHz to
25.6kHz; 1kHz from 26kHz to 256kHz; 10kHz from 260kHz to 2.56MHz; 100kHz from
2.6MHz to 25.6MHz. Cutoff Frequency Accuracy: ±2% to 2.56MHz, ±5% to 25.6MHz. Passband Response: ±0.2dB up to 2.56MHz, ±0.5dB to 25.6MHz. Stopband Attenuation: -100dB to 1MHz; -75dB at 10MHz; -55dB at 30MHz;
-50dB at 50MHz; -40dB to 100MHz. Input/Output Coupling: AC or DC. AC coupling cutoff is approximately
16Hz at the input and 10Hz at the output with a 50W termination. Note
that the internal 50W input termination is before the AC coupling. Noise Spectral Density (10kHz to 100MHz referred to input): Below –128dBm/Hz
into 50 ohms.
This translates into a wideband noise power or voltage for a 30MHz BW of below
–53dBm or 500µVrms referred to input. Harmonic Distortion (1Vrms sinewave): >–60dB below signal up to
100kHz (0.1%). All harmonics below 50dB to 1MHz; below 40dB above 1MHz. Spurious Signals: Below –80dBm to 65MHz; below –75dBm to 100MHz. Referred
to input represented in voltage form: 22mV and 40mV respectively. DC Stability: ±0.5mV/°C referred to input.
Input: Pre-Filter Gain: 0dB, +10dB, +20dB; ±0.1dB.
Impedance: Selectable 1M ohms or 50 ohms, ±2%, shunted by 65pF.
Maximum Signal: ±1.5V peak with 0dB input gain, reduced in proportion
to input gain selected.
Maximum Input Without Damage: 12Vrms with input terminator OFF, 7Vrms
with input terminator
ON.
Maximum DC Blocking Voltage: 200V. Note that the internal input termination
is before the AC
coupling and can only tolerate 7Vrms when ON.
Output: Post-Filter Gain: 0dB, +6dB, +20dB, +26dB; ±0.1dB.
Impedance: 50 ohms, ±2%.
Maximum Signal: ±3V peak open circuit; ±1.5V peak into 50 ohms.
DC Level: Adjustable to Zero.
AMPLIFIER MODE CHARACTERISTICS
(Channel 2.1 only) Bandwidth: >50MHz. Input: Pre-Filter Gain: 0dB, +10dB, +20dB; ±0.1dB.
Impedance: Selectable 1M ohm or 50 ohms, ±2%, shunted by 65pF.
Maximum Signal: ±1.5V peak with 0dB input gain, reduced in proportion
to input gain selected.
Maximum Input Without Damage: 12Vrms with input terminator OFF, 7Vrms
with input terminator
ON.
Maximum DC Blocking Voltage: 200V. Note that the internal input termination
is before the AC
coupling and can only tolerate 7Vrms when ON. Output: Post-Filter Gain: 0dB, +6dB, +20dB, +26dB; ±0.1dB.
Impedance: 50 ohms, ±2%.
Maximum Signal: ±3V peak open circuit; ±1.5V peak into 50 ohms.
DC Level: Adjustable to Zero.
Rise and Fall Time: <7ns with 0dB input gain 6dB output gain; <10ns
with +20dB input
or output gain. <5% ringing or overshoot.
GENERAL Frequency Control:
Keypad entry or increment, decrement keys. Memory: 99 selectable groups; memory is non-volatile battery-backed CMOS. Overload Modes (Channel 2.1 only): Three selectable modes; non-latching,
that monitors all channels and displays the first channel to have an overload;
latching, that maintains the overload display until it is cleared; and no indications. Overload Indicators (Channel 2.1 only): LEDs for input and output. Gain
display flashes when overload occurs on displayed channel. Self-Test Diagnostics: MPU checks unit upon power-up. Display indicates
failure mode. Displays: 7 segment, green, LED; 0.3" high. Remote Programming: IEEE-488.1 interface. Subsets: SH1, AH1, T6, L4,
SR1, RL1, PP1, DC1, DT0, C0, E1. Operating Temperature: 0°C to 50°C. Isolation to Chassis: ±200Vdc. Storage Temperature: –20°C to 70°C. Input/Output Connectors: BNC, front and rear. Power Requirements: 90-132/180-264 volts ac, 50Hz-400Hz, 35 watts. Dimensions: 3.5" (9cm) high, 8.5" (21.8cm) wide, 18" (46.2cm) deep. Weights: 12 lbs (5.4kg) net; 14 lbs (6.3kg) shipping. Accessories: 6 foot, 3 terminal line cord, operating manual.
OPTIONS
020:Lower
frequency cutoff range to 0.3Hz to 200kHz for channels 1 and 2 only. Rack Mount Kit: Part No. RK-37, permits installation of the Model 3945
into a standard 19" rack spacing. Extended 1 Year Warranty: Part No. EW3945.
OPTIONAL
ACCESSORIES
CAB-010:
GPIB Cable with
Connectors, 2-Meters
CAB-011:
GPIB
Cable with Connectors, 1-Meters
CAB-025:
Cable, BNC, 3ft, Low Noise
Specifications apply
at 25°C ±10°C.
Specifications subject to change without notice.
HIGH FREQUENCY BAND-PASS
OPERATION
Connecting the output
of channel 1.1 or 1.2 (set to high-pass) to the input of channel 2.1 (set to
low-pass, 50 ohm input impedance, 6dB output gain), provides a band-pass filter
with 0dB insertion loss and the low-cutoff adjustable between 3Hz and
2MHz, and the high-cutoff adjustable between 170Hz and 10MHz. At high-cutoff
settings above 10MHz, the passband response will deteriorate.
