Silicon CapacitorsApplication for Base Station RFPA

Signal-frequency broadband expansion and issues associated with 5G high-speed large capacity communications

An expansion of several times to several tens of times of the current bandwidth is being considered to enable communications speed of 10 Gbps, which is 100 times the current speed. However, it is known that when a broadband signal is output at a high power, an Inter Modulation Distortion (IMD) is generated in the Power Amplifier Module (PAM), reducing signal integrity. IMD frequency is a proportional function of the bandwidth, and the affected frequencies in Second-Order IMD are up to 400 MHz with Sub 6 GHz or several GHz with mmWave.

Target application: RFPA Module for Base Station

Solution for Decoupling

Solutions by silicon capacitor

Following is an explanation of how to remove Second-Order IMD. The low frequency band of IMD can be removed using a bias circuit connected to an FET drain. However, the high frequency band of IMD is difficult to remove outside of the PAM due to the influence of the microstrip line for RF-Blocking. In the method described here,the silicon capacitor (Si-Cap) is installed directly onto the metal substrates of the PAM, and the FET and Si-Cap are connected by a wire.
This method uses a small Si-Cap that maintains a high capacity under actual usage conditions, enabling the removal of the IMD in the limited space inside the PAM.

Feature of Si-Cap

Realizing a small size and high capacitance in actual usage conditions (high temperature environment with applied voltage)

Murata technology was used to make the Si-Cap with deep trenches and tripod pillars, providing 100 times more electrode surface area than with a planar structure, and enabling a small size and high capacitance. In addition, a temperature compensating material is used as the dielectric of the Si-Cap, maintaining capacitance even in actual usage conditions, enabling a maximum capacitance density in small and vertical capacitors.

Standard Product Lineup

Wire bondable series

Si-IPD Option

Customization according to your needs available


+ Resistor

Optimum capacitance and resistance value for each PAM made in 1 chip

Murata offers Si-Caps in not only our standard lineup, but also customized IPDs (Integrated Passive Devices) made to according to the customer's needs. With an IPD, you can integrate as much capacitance and resistance as required all in a single chip. Therefore, it is possible to create capacitors with a higher capacitance value than our standard lineup, and to consider chips with resistors and capacitors connected in a series to suppress antiresonance.

Inquiries about custom designs