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Low Pass Filters - FLP


  • Low insertion loss
  • Second harmonic rejection
  • Small, rugged package


  • Preselect filter
  • Spurious and harmonic suppression
  • Image rejection for receivers

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Download the FLP specsheet (.pdf)


Millitech series FLP low pass filters provide a high rejection and excellent selectivity for frequencies above a corner frequency at band edge. These filters are characterized by very low loss and minimum ripple within the passband. Waveguide cut-off frequency determines the lower band edge for the standard models. This filter has a very wide stopband, rejecting up to three times the highest passband frequency.

Series FLP filters are ideally suited as preselectors for broadband receivers as they provide a high degree of selectivity and a very broad rejection band. They are particularly useful for image undesired signal rejection prior to signal downconversion, and the elimination of undesirable signals from downconverters. When used with oscillators and signal generators, these filters can strongly attenuate spurious outputs and harmonics.

In addition, they are well suited for test instruments and measurement equipment such as network analyzers, which requires a fullband operation with minimal spurious response.

The skirt selectivity characteristics can be tailored to provide the desired amount of attenuation. The passband insertion loss depends on the selectivity or attenuation at a specific high frequency. Figure 1 below and the table on the next page provide general filter characteristics of series FLP products. The lower band edge (corner frequency) of the standard models can be changed to obtain a broadband bandpass filter. See series FWP wide bandpass filters and FHP high pass filters.

Figure 1 - General Characteristics of Low Pass Filters

General Characteristics of Low Pass Filters Legend

Electrical Specifications

Model Number FLP-42 FLP-28 FLP-22 FLP-19 FLP-15 FLP-12 FLP-10
Frequency band and bange(GHz) K
Standard Products
Bandwidth (GHz)* 18-26.5 26.5-40 33-50 40-60 50-75 60-90 75-110
Insertion Loss (dB) 1.0 1.0 1.0 1.0 1.2 1.4 1.6
Upper band edge (fE) (typ) (corner frequency) (GHz) 28.3 41.2 52.0 62.0 77.0 93.0 114.0
Rejection band (fH to fU) (GHz) (typ)*1 34-66 49-95 62-120 74-143 92-178 111-214 139-263
Rejection at fH (min) 40 dB 40 dB 40 dB 40 dB 40 dB 40 dB 40 dB
Waveguide cutoff frequency (fC) (GHz)*2 14.1 21.1 26.3 31.4 39.9 48.4 59.1
Custom Products
Attenuation range for high frequencies (fH to fU) (dB) 22-55 25-50 25-45 25-40 25-40 25-40 25-40

*1 - Rejection band attenuation (fH to fU): greater than 40 dB.
*2 - Frequencies below this waveguide cut-off frequency are significantly attenuated. Typical attenuation at 0.85 times cut-off frequency is 40 dB.

Mechanical Specifications

Model Number FLP-42 FLP-28 FLP-22 FLP-19 FLP-15 FLP-12 FLP-10
A (in/mm) 0.88/22.4 0.75/19.1 1.13/28.7 1.13/28.7 0.75/19.1 0.75/19.1 0.75/19.1
B (in/mm) 2.92/75.2 2.00/50.8 1.40/35.6 1.40/35.6 0.96/24.4 1.85/21.6 0.75/19.1
Flange MIL.F-3922 /54.001* /54-003* /67B-006 /67B-007 /67B-008 /67B-009 /67B-010

*With #4-40 threaded holes.

Outline Drawings

FLP - Outline Drawings

How to Order

Specify Model Number
XX =Waveguide Band
  • WR - number
A = Flange Type
  • R - round
  • S - square
0 = Other Options
  • N - nonstandard (specify requirements)

*Please specify passband and rejection band frequencies as well as square or round flange when ordering nonstandard product.