Specifying a Low Pass Filter

The graph shown here illustrates a typical low pass filter (LPF) function. It indicates how much attenuation is achieved at a given frequency for, in this instance, the IMF2293. All other LPF graphs will be similar to this one, but will have different frequency spans and different gradients depending on the design of the filter. In order to quote/specify a low pass filter, the following information must typically be provided: 1. The extent of the passband (i.e.; what frequencies does the low pass filter PASS?). 2. The passband insertion loss (how much power is dissipated by the filter) 3. The stop band attenuation levels and frequencies (which frequencies does the filter reject and by how much?). Generally, IMS filters will have passband insertion losses ranging between 0.5 dB and 1.0 dB with a few exceptions, depending on design. If a customer needs less than 0.3dB loss, it is unlikely that IMS can meet that requirement. Conversely, if the customer can live with greater than 2 dB insertion loss, then they may be able to use an off the shelf lowcost LTCC device. The extent of the passband is usually described as "DC to 1.5GHz" or "DC to 2.4GHz"