Digitally Tunable RF Filters

The communication industry is faced with a challenge concerning future wireless communication systems. Since the demand on frequency spectrum resources is increasing, wireless communication systems have to deal with coexistence and interference problems. Ever-evolving communication standards and the need for multi-standard communication devices to keep pace with these developments make digitally tunable RF filters essential.

The tunable RF filters developed by Fraunhofer IIS enhance the capabilities of transceiver units in terms of frequency selectivity, flexibility, and agility. The modules reliably select the required frequency spectrum while rejecting out-of-band signals. They are digitally tunable and can be reconfigured even during operation, which decreases latency and allows for dynamic spectrum access. Digitally tunable filter modules can be used to replace filter banks in RF front ends.

We develop tunable filters for a wide range of applications in the fields of mobile communication, public safety, the Internet of Things (IoT) and satellite communication. Typically RF filters are in use for multiband and broadband receivers and transmitters, multi-standard transceivers, software defined radio (SDR), cognitive radio and frequency monitoring.

Size comparison between 1 cent euro coin and banpass filter — © Fraunhofer IIS
Miniaturized design – digitally tunable RF filters

© Fraunhofer IIS
Solderable SMD module (back side)

© Fraunhofer IIS
SMD module on evaluation board

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RF bandpass filters

In the frequency range between 220 and 1400 MHz there are three different bandpass filters obtainable as solderable SMD modules. Corresponding evaluation boards and S-parameters (S2P data files) are available on request.

tBPF-220-425

tunable Bandpass Filter for frequencies from 220 to 425 MHz

tBPF-430-890

tunable Bandpass Filter for frequencies from 430 to 890 MHz

tBPF-630-1400

tunable Bandpass Filter for frequencies from 630 to 1400 MHz

The RF preselection filters enable frequency hopping in 32 steps within a switching period of 12 μs. The adjustable filters cover the frequency range from 220 to 425 MHz, from 430 to 890 MHz, and from 630 to 1400 MHz.

This includes the following selectable RF bands:

TV white spaces
LTE 800 and GSM 900
433 MHz and 902 MHz ISM band (license-free)
868 MHz short-range device band (license-free)
DVB-T/DVB-T2

Customized bandpass filters

In the range from 220 to 1400 MHz customer-specific adjustments to the RF bandpass filters are possible on request.

RF lowpass filters

In the frequency range between 500 and 720 MHz there is a lowpass filter obtainable as solderable SMD module. A corresponding evaluation board and S-parameters (S2P data files) are available on request.

tLPF-500-720

tunable Lowpass Filter for frequencies from 500 to 720 MHz

The RF preselection filter enables frequency hopping in 32 steps within a switching period of 12 μs.

Customized lowpass filters

In the range from 30 to 3000 MHz customer-specific adjustments to the RF lowpass filter are possible on request.

Customized RF filters

RF filters for various frequencies in the microwave range

In addition to our available RF filter modules we offer customized bandpass, lowpass, highpass and band-stop filters for various frequencies in the microwave range.

Consulting and evaluation

We carry out requirement analyses and technical feasibility studies in order to find the solution that fits your needs. As part of this process, we provide evaluation boards for performance testing.

Development

We offer customization and further development of prototypes according to your individual requirements.

We look forward to your request

The benefits at a glance

Increased flexibility of RF front ends

Frequency-agile filters enhance the flexibility of RF front ends, which can be easily adapted to new communication standards and country- or application-specific frequency ranges even during run-time.

Flexible interference management

Based on their high switching speed and reliability, the digitally tunable filters help to avoid interference between wireless systems and enable flexible coexistence solutions like cognitive radio.

Simple implementation and operation

Replacing filter banks with digitally tunable filter modules reduces the size of RF front ends. The RF filters can be easily adjusted by a 3-wire SPI control signal and operate at a constant supply voltage of up to 3.5 volts.

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