With continuously decreasing dimensions of modern mobile phones, the compact design of all internal modules is an essential development goal. The structure considered is from a dual band phone (GSM 900 MHz + DCS 1800 MHz) which combines a diplexer for both bands and a low pass filter for each band. The device is only 4.5 mm by 3.2 mm and utilizes LTCC technology.
Firstly, the diplexer functionality is investigated:
In the diplexer port 2 represents the GSM, port 3 the DCS part. The following figures represent the return loss of both modes as well as the transmission to the common port 1. The left graphs show the simulations, the right ones the measurements. Excellent agreement between the results can be observed.
In the following section, the low pass filters for both the GSM and the DCS bands are considered. The relevant ports for both modes are shown in the structure.
The copyright for the displayed structure is with "Korea Electronics Technology Institute (KETI), High Frequency Materials Research Center".