A Design for a Robust, Selective and Flexible RF Front-End for Wideband Receivers

Recently Sivan Toledo wrote in wanting to share an academic paper he wrote together with Itamar Melamed, both from Tel-Aviv University in Israel. The freely available paper describes the design and evaluation of a second-generation front-end for wideband software defined radios. Their front-end helps SDRs optimize reception by providing filtering, a bias tee for mast head amplifiers and also protects the radio against damage from strong signals with an RF limiter. The abstract reads:

In this paper, we describe the design and evaluation of a second-generation front-end unit for wideband sampling radio receivers. The unit contains a surface acoustic wave (SAW) filter to protect the receiver from strong out-of-band signals, an RF limiter to protect both the filter and the receiver from physical damage due to strong signals, and a bias tee with a DC limiter to provide DC power to a masthead low-noise amplifier, if one is used. The unit allows receivers such as those of the universal software radio peripheral (USRP) N-series type to be effectively used in RF environments with weak signals and strong in-band and out-of-band interferences.

Although the front-end is designed for the USRP SDR, it should also work well with RTL-SDR dongles and other SDRs. The authors also write that their design is uploaded and available for PCB printing on CircuitHub.

Itamar and Sivans RF Front-End
Itamar and Sivans RF Front-End
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Raziel Einhorn

Nice paper. Thanks for sharing.
The suggested front-end can help a lot when investigating a known frequency band, such as ISM433, ISM2.4 etc., however it is not good for a general case, for example if you wish to scan a wide range of frequencies. Also, SAW filters come in pre-defined frequencies, BW and filtering performance, so not every desire can be met by these. You will have to switch between FE’s for different frequencies (or change the SAW filter each time).
I think the main take-away from this paper is the PCB design which is flexible enough to put different SAW filters. Upgrade it to allow implementing LC filters too and you got a nice multitool.

Sivan Toledo

Thanks Raziel. Yes, this is definitely not for scanning. It is intended for applications that use a particular band.