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The evolution of LTE smartphones is currently being accelerated to include the function of multiband support, which uses more than one frequency band to support high-speed communication. There have been an increasing number of smartphone models that can be adapted for carrier aggregation, or CA, as well. The configuration of RF front end has become increasingly complex, which has made it hard for makers to provide terminals with ideal characteristics desired by clients within a short lead time. To provide solutions for this kind of problem, Murata has engaged itself in the development of PAMid, an integrated RF front end module, taking advantage of self-manufactured RF front end.

PAMid block diagram

When PA and DPX are used as individual components of a circuit, they are generally prepared as packaged products by including an additional 50 Ω impedance matching circuit in each device. In contrast, Murata’s PAMid has self-manufactured PA and DPX already mounted on the LTCC substrate. Notice that this is done at a level of wafer specifically designed for the module. This allows us to resin-package an entire module all at once. The process helps us accomplish miniaturization as well as inexpensive manufacturing of the products. What is also important in implementing the miniaturization along with wafer-level devices is the LTCC substrate technology. The use of very thin ceramic sheets enables us to form more than twice as many layers as common resin substrates. Taking advantage of this manufacturing method, we have succeeded in building into the LTCC substrate filters attenuating higher harmonics and impedance matching circuits, realizing the world’s smallest module.

LMTWHT Series (7.5*6.0 mm)
Inside the border: wafer-level devices

When it comes to module characteristics, it is important to optimize an entire product by total engineering. For example, the electromagnetic field coupling of the DPX and the LTCC substrate built-in circuits helps us accomplish isolation equal or superior to that established by the DPX alone. We feel that we do not need to be fastidious about 50 Ω to achieve the impedance matching between the PA and the DPX; instead, we simplify the circuit and reduce the matching loss, and at the same time optimize the phase, to accomplish high efficiency in transmission and noise suppression in reception.

Isolation characteristics between transmitter and receiver

This kind of engineering optimization is accomplished by simulation technologies. Murata uses the self-developed simulator Femtet to analyze the electromagnetic field of entire modules, which helps us conduct the entire optimization process in a short time.

Self-developed electromagnetic field simulation model (Hertz)