The typical use of a diplexer (three port device) enables source transmitters operating on two separate frequencies to use the same antenna. In other applications, the diplexer allows a single antenna to transmit and receive on discreet frequencies. Additionally, a diplexer will provide the ability for an antenna to transmit and receive simultaneously.
When designing and manufacturing passive broadband high frequency cascaded LC (inductor and capacitor) filters, a lot of undesirable component interactions can occur if not properly managed.
The goal is to minimize the difference between a filter constructed with ideal components and one using commercial off-the-shelf (COTS) and custom manufactured components. Limitations of these components are frequency dependent but various techniques can be employed to improve their performance and reduce their impact on the filter's overall electrical response.