RF front-end filters address a variety of functions such as band-pass, low-pass, and high-pass filters. RF filters can be easily integrated into front-end modules using ST's thin-film RF IPD process. This process integrates high-quality passive RF components into a single glass or high-resistance silicon substrate.
Applications
What are RF Fliters used for?
RF filters enable or inhibit selected signals or frequencies to eliminate interference or the transmission of unwanted signals. So, our RF filters address a wide range of applications such as mobile and connected devices, cellular base-stations, and consumer applications.
- Asset Tracking
- Energy Generation and Distribution
- Factory automation
- Home and Professional Appliances
- Home, Building and City Automation
Types of RF filters
There are four basic types of RF filters: high-pass, low-pass, band-pass, and band-reject filters.
- Low-pass filters:
There are various types of low-pass filters. The main use of this filter is to suppress the harmonics of the RF amplifier. This characteristic helps avoid unwanted interference in different transmission bands. High frequency filtering give signals a sharper and clearer quality.
- High-pass filters:
In contrast to low-pass filters, high-pass filters attenuate frequencies below a certain threshold so only high-frequency signals can pass. The high-pass filter can be used in combination with a low-pass filter to form a band-pass filter.
- Band-pass filters:
Band-pass filters are circuits that pass signals of two different frequencies and attenuate signals outside a given range. ST RF IPD band-pass filters do not use an external power source and integrate passive components like inductors and capacitors. Active band-pass filters instead need external power and active components like integrated circuits and transistors.
Band-pass filters are commonly used in wireless receivers and transmitters. Band-pass filters minimize the bandwidth of output signals to allow transmitters to send data at desired speeds and formats.
Band-pass filters in receivers only allow desired frequencies to be decoded, while blocking the inclusion of other signals from unwanted frequencies.
Overall, a well-designed bandpass filter can easily maximize signal quality while minimizing conflicts and interference between signals.
- Band-reject filters:
A band-reject or notch filter allows most signal frequencies to pass, but attenuates specific frequency ranges to very low levels. It is the opposite of the band-pass filter.
Which RF filter do I need?
For Bluetooth applications, the MLPF-WB-01D3, MLPF-WB-01E3 and MLPF-WB55-01E3 are impedance matched harmonics filters optimized for our dual-core, multiprotocol wireless STM32WB55Cx, STM32WB55Rx, STM32WB35xx, STM32WB50xx, STM32WB30xxx, STM32WB1xx microcontrollers. It requires seven times less PCB space than the equivalent L-C discrete solution.
The MLPF-WB55-02E3 is tailored to match the output impedance of the STM32WB55Vx, STM32WB1x series, while the MLPF-WB-02D3 is designed to maximize the RF performance of STM32WB5x and STM32WB1x wireless MCUs. In addition, the MLPF-NRG-01D3 is tailored for the BLUENRG-LP(S) systems-on-chip.
| Associated RF Microcontroller | Matched Low Pass Filter Companion Chip | Frequency (MHz) | Integrated filter | Size | Package |
|---|---|---|---|---|---|
| STM32WB55Cx, STM32WB55Rx, STM32WB35xx, STM32WB50xx, STM32WB30xxx, STM32WB1xx | MLPF-WB-01E3 | 2400-2500 | Yes | 1.5 mm x 1.0 mm | Bumpless CSP |
| MLPF-WB-01D3 | 2400-2500 | Yes | 1.5 mm x 1.0 mm | WLCSP 0.4mm | |
| MLPF-WB55-01E3 | 2400-2500 | Yes | 1.5 mm x 1.0 mm | Bumpless CSP | |
| STM32WB55Vx, STM32WB1x | MLPF-WB55-02E3 | 2400-2500 | Yes | 1.5 mm x 1.0 mm | Bumpless CSP |
| STM32WB5x, STM32WB1x | MLPF-WB-02D3 | 2400-2500 | Yes | 1.5 mm x 1.0 mm | WLCSP 0.4mm |
| BLUENRG-LP(S) | MLPF-NRG-01D3 | 2400-2500 | Yes | 1.5 mm x 1.0 mm | WLCSP 0.4mm |
Benefits
- ST's RF filters ensure design simplification and performance optimization.
- Our technology of passive integration on high resistivity substrate provides higher system integration, especially for RF module integration.
- Improves reliability and can significantly reduce the bill-of-materials with respect to alternative discrete solutions.
