Based on the application, electrical, mechanical requirements, and knowing what type of filter topology to use can help exceed the performance of the product. Both of these designs use specific topologies based on frequency and power handling requirements.
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.