M3SR FU221 VHF Automatic Filters and Multicouplers by Rohde & Schwarz

Companies & Organizations:


Rohde & Schwarz GmbH & Co KG
Muehldorfstrasse 15
81671 Muenchen

The R&S®FD221 and R&S®FU221 filters are an essential part of radio equipment. They are used at radio sites where the reciprocal influence of neighboring radio systems must be selectively restricted. Selective restriction is the only way multiple radio systems can be simultaneously operated in very tight spaces. As a result, sustainable, higher quality radio links that are more reliable can be achieved.


The frequency-agile R&S®FD221 and R&S®FU221 filters protect the operator's radio system against third-party RF interference. The filters work in both the transmit and receive directions.


A wide variety of radio installations can be the source of unwanted RF interference. Frequent sources include broadcasting, microwave link and radar applications because they often operate with high transmit power. The filters protect the operator's radio system against such interference in the receive direction.


In the transmit direction, the filters protect sensitive third-party radio applications, such as navigation and radiomonitoring equipment, against the operator's out-ofband RF signals.


The filter effect in the receive and transmit directions also lets operators make economic use of their frequency bands. The frequency spacing between useful channels is substantially reduced, making it easier to install the required antennas. The physical spacing between the antenna sites is significantly reduced because the filters substantially increase the RF decoupling.


The highly selective filters are mechanically rugged and therefore can be used on board ships and semi-mobile facilities as well as in ground installations.


Key Facts


Excellent mechanical precision

Short tuning time

Power supplied directly from the radio system

Available as two, three and four-way multicoupler

Very low insertion loss


Features & Benefits


Receiver benefits

- Suppression of out-of-band based intermodulation products by additionally attenuating all signals and their harmonics which are outside the receiving range and – due to nonlinearities and mixing – could cause intermodulation products to fall within the useful VHF or UHF band and interfere with reception

- Suppression of third-order crossmodulation products by attenuating strong interfering signals which could transfer their modulation to the wanted signal

- Increase of image frequency rejection by additionally attenuating signals defined as image frequency relative to the received frequency

- Prevention of desensitization (reciprocal mixing) by attenuating strong interfering signals which could otherwise transfer the noise sidebands of the receiver oscillator, mixed onto the interfering signal, to the useful band, thus reducing sensitivity


Transmitter benefits

- Attenuation of broadband transmitter noise caused by the radio oscillator or power amplifiers

- Suppression of spurious emissions caused by the radio power amplifier

- Suppression of harmonics mainly generated in the output stages

- Attenuation of transmitter (backward) 3rd order or higher intermodulation products, mainly caused by simultaneously operating radio systems with co-sited transmitters

Defense Products & Services: M3SR FU221 VHF Automatic Filters and Multicouplers by Rohde & Schwarz
Companies & Organizations: 
Country: Germany
Description: M3SR FU221 VHF Automatic Filters and Multicouplers
Source of Information: Rohde & Schwarz GmbH & Co KG