一．        Numbers of section：

       The numbers of sections is determined by the following steps:

1．Fix the central frequency：e.g.  f₀=500MHz

2．Fix the bandwidth：e.g.  60MHz at 3dB（i.e.f₀=±30MHz，the relative 

bandwidth=12%）

3．The required out-off-band attenuation：e.g.  attenuation≥40dB at 400MHz and 600MHz

4．Fix the bandwidth of 3dB from the central frequency  =（rejectband frequency － central frequency）/ 3dB bandwidth

                    e.g.（400 -500）/ 60 = -1.67

                  （600 -500）/ 60 = +1.67

5．Numbers of sections：n_L（numbers of sections for low end）= 4

                                                       n_H（numbers of sections for high end）= 5

                                                       then n=max（n_L，n_H）=5

一．           Insertion loss calculation ：

1．Formula for the MAX insertion loss at central frequency：

A₀(dB) =（loss constant）×（numbers of sections＋0.5）/%  3dB bandwidth＋0.3note：the real insertion loss is expected to be better than this formula 。

1．Loss constant：

一．           PN rules：

The PN of LC filters consists of performance parameters and package. The standard input/output lead is φ0.5 or φ0.8 signal probe. In case of SMA, it’s required to be marked following the package. 

Note1：

1．In addition to the parameters, customer also can offer PN according to our rules when placing orders。

2．The old PN is also effective.

LC bandpass filters

FB×××—   ××/ ×—  ×    ××  ××

  1            2  3      4       5   6

      Interpretation： FB— bandpass filter

             1—central frequency f₀，taking MHz for unit

             2—passband BW，taking MHz for unit

             3—bandwidth feature   T—3Db BW

                                               O—1dB BW

                                               H—0.5dB BW

                                               F—0.2Db flat BW

                         　                  P—Dot frequency

             4— numbers of section

               5—package ：P：radial pin

                                       C：axial probe

                                       I：parallel（II） probe

                                       L：right angle（L） probe（L）

                      D：DiP dual-in-line integrate circuit pin

                                       S：SMT

               6—package SN

LC lowpass filter

FL×××/×－×××－×× ××

 1   2     3        4    5

  Interpretation：FL—lowpass filter

                1—Cutoff frequency, MHz for unit

                2—Cutoff frequency features 

                                   T—3dB BW 

                                   O—1dB BW

                3—frequency at the suppression point，

taking MHz for unit               

4/5—package series

LC highpass filter

FH×××/× ×××—×× ××

   1    2    3       4    5    

Interpretation：FH—highpass filter

              1—cutoff frequency f_C，taking MHz for unit

              2—cutoff frequency features 

                                  T—3dB BW

                                  O—1dB BW

              3—frequency at the suppression point，

taking MHz for unit 

4/5—package series

LC Notch Filter

FR×××-×××/×× -×× ××

   1      2      3     4    5    

 Interpretation：FR—band-reject filter

           1—central frequency, taking MHz for unit

           2—bandwidth of reject band, taking MHz for unit

           3—suppression of reject band, taking dBc for uni

           4、5—package series 

LC Duplexer

FDS-×/× -× ××—×× ××

         1  2  3   4         5    

 Interpretation：FDS—combining filter

1—CH1 central frequency, taking MHz for unit

2—CH2 central frequency, taking MHz for unit

                     3— frequency feature:  B for bandpass filter

                              P for dot frequency filter

                     4— bandwidth of pass band (only for bandpass filter

5— package series