With the development of miniaturization and single-chip devices, the integration of active and passive circuits is the trend. Conventional filters have become the bottleneck for miniaturization and single-chip of microwave and millimeter wave devices due to their large size (especially in the millimeter wave frequency band), and only chip based filters can solve this problem. In terms of new processes and technologies for chip based filters, microfabrication technology based on silicon wafers has advantages such as high accuracy, low cost, and suitability for mass production. The silicon filter achieved by its processing methods has obvious advantages in the millimeter wave frequency band, such as high Q value, low loss, small size, and low cost. Silicon filters can also be compatible with conventional single chip microwave integrated circuit (MMIC) processes. They have not only become the development trend of various electronic devices, but also an excellent means to solve the chip based problem of millimeter wave filters. PAM-XIAMEN can supply Silicon substrate for filters, take the following specification for example:
1. Substrate Specifications for Silicon Filter
Please visit the website: https://www.powerwaywafer.com/silicon-wafer to choose the specification you need.
Currently, integrated microwave photonic filters are mainly implemented on three material platforms: InP, silicon, and silicon nitride (Si3N4). The process development of InP based platforms is the most mature, which can simultaneously prepare active devices (lasers, modulators, optical amplifiers, and detectors) and passive devices (optical waveguides), but there are problems such as high losses (1.5-3dB/cm), complex processes, high costs, and incompatibility with CMOS processes. Silicon based and silicon nitride based material platforms can utilize existing mature microelectronic integration processes for device preparation, with low waveguide transmission loss (Si: 0.1~2dB/cm; Si3N4: 0.01~0.2dB/cm), low preparation cost, easy mass production, and good compatibility with CMOS standard processes. They have the potential for single-chip integration with drive circuits.
2. About Filter on Silicon Subtrate
Silicon filter is the important component in RF systems, and its performance directly affects the quality of signal communication. Due to the need to receive signals from various frequency bands in the RF front-end, the interference between signals needs to be solved by filters, which are used in both transmission and reception channels. Therefore, it is a core component of the RF system and directly affects the communication quality of signals in various frequency bands. It is widely used in base stations and terminal equipment.
The signal strength passed by the filter varies at different frequencies, and the filtering curve can be drawn to measure the performance of the filter. The key indicators include:
Quality factor: defined as the center frequency divided by the filter bandwidth, measures the ability of the filter to separate adjacent frequency components in the signal. The higher the Q value, the narrower the passband width and the better the filtering effect;
Bandwidth: Generally, it is a 3dB bandwidth, which refers to the bandwidth where the signal loss is within 50%. It describes the frequency range of the signal that can pass through the filter and reflects the frequency selection of the filter;
Insertion Loss: Refers to the attenuation caused by the introduction of filters on the original signal in the circuit, expressed in dB. The larger the insertion loss, the greater the degree of attenuation;
Out Band Rejection: An important indicator for measuring the performance of filter selection. The higher the indicator, the better the suppression of out of band interference signals;
Delay time: The time required for the signal to pass through the filter.