Your Cart

Combline & Interdigital

Combline & Interdigital Filters

  • BANDWIDTH OF 1% TO 66%

Combine filters are bandpass filters used in the frequency range of 30 MHz to 18GHz The structure consists of a series of TEM resonators of circular or rectangular cross-section resonated by a capacitor at the open circuit end. The bandwidth and response of the filter is governed by the coupling of each resonator to its immediate neighbor. This is also a function of the resonator size, resonator spacing and ground plane separation. Typical construction is silver-plated aluminum. This achieves the lowest passband loss while maintaining lightweight. Computer design programs result in close correlation between theoretical and actual performance.

In applications where flat group-delay narrowband filters are required, linear phase responses of typically 1 to 5% variations over 70% of the filter bandwidth can be achieved.

As the frequency of operation is reduced, the reactance components increase in physical size. But for a given Q, the size of an air-spaced inductor increases as the frequency decreases.

 Model K2CModel K3CModel K6CModel K7C
FO: (standard)30 – 450 MHz400 – 3000 MHz2000 – 6000 MHz6000 – 12400 MHz
  (special)20 – 600 MHz250 – 4000 MHz1500 – 14000 MHz500 – 18000 MHz
Sections3 to 62 to 72 to 72 to 4
VSWR (Max)1.5:11.2:11.2:11.5:1
Temperature Range-54° to +100° C


KW Microwave’s interdigital filters fill the need for moderate and wide bandwidth filters in the 1.0 to 12 GHz frequency range. Our standard unit is available with up to 17 sections, while custom designs have 20 sections. KW Microwave’s interdigital filters offer low loss, high “Q” performance in package styles suitable for many applications, including space.

Frequency Range1000 – 10000 MHz500 – 12000 MHz
Number of Sections3 to 103 to 20
VSWR (Max)1.5:11.3:1
Temperature Range-54° to +100° C