New balun antenna matching design occupies up to 90 percent less board space

January 15, 2013 // By Paul Buckley
STMicroelectronics has developed an integrated 2.4 GHz balun design for Nordic Semiconductor's nRF51 and nRF24 Series transceivers and SoCs that eliminates the need for RF antenna matching circuitry.

The solution slashes board space requirements by up to 90 percent while improving performance, simplifying design, and reducing cost and BoM.   

The design does away with  RF antenna matching circuitry that would typically comprise up to eight passive components (capacitors and inductors) and the interconnections between them.      

The STMicroelectronics design incorporates a BAL-NRF01D3 Integrated Passive Device (IPD) balun matching network in a single 1.0 x 1.5 mm flip-chip package. The IPD balun takes direct differential input from a Nordic nRF device and feeds directly out into a single-ended 50-Ohm antenna. The Nordic nRF24 Series devices require no further matching and harmonic suppression components. The Nordic nRF51 Series devices require only a single 0.8 pF capacitor externally to the ST BAL-NRF01D3.           

The high Q (antenna performance boosting) thin-film technology employed in the ST BAL-NRF01D3 also significantly improves RF performance and characteristics over the use of standard passive component matching. This includes: a +0.9 dB average output power improvement at 4 dBm; +1 dB better sensitivity at 1Mbs on-air transmit speeds; 10 dB better LO (local oscillator) suppression; and -39.1 dBm 2nd harmonic suppression. The improved harmonic and LO suppression levels also promote simpler mandatory FCC/ETSI compliance testing and approvals.     

The up to 90 percent reduced board space benefit of the BAL-NRF01D3 IPD balun is especially useful in applications where PCB floor space is at a premium (although the overall performance improvements will benefit almost any design) including coin-sized sports watches and related accessories, smartphone and cellphone proximity and alert tags, and smart inventory RF tracking ID tags.     

The BAL-NRF01D3 is available now directly from ST Microelectronics and through authorized distributors.     

More information about the BAL-NRF01D3 at