A low-noise active balun with IM2 cancellation for multiband portable DVB-H receivers

Broadband low noise amplifiers are needed in a variety of applications, from multistandard cellular receivers to terrestrial and handheld TV tuners [1,2]. For broadband and multiband operation, intermodulation and cross-modulation impose additional linearity requirements to the RF front-end [2,3]. In a multiband DVB-H receiver covering both VHF-III (from 170 to 230MHz) and UHF IV–V (from 470 to 890MHz) receive bands [4], cross-modulation between VHF III and UHF IV–V channels gives rise to second order intermodulation distortion (IM2) products that fall from 650MHz up to 890MHz, covering most of the UHF IV–V band. Cross-modulation between UHF IV–V band channels gives rise to IM2 products covering the whole VHF-III band. The most stringent second-order intermodulation intercept point (IIP2) requirement is given by single-tone S2 test patterns [4]: the maximum interferer level for a portable receiver (class b2, c) is −28dBm, 42dB above the desired signal. Assuming a 5dB NF and a minimum SNR of 12.7dB, the minimum IIP2 is 26.8dBm. The most stringent IIP3 requirement is set by L2, L4 test patterns: the maximum interferer level is −35dBm, 47dB above the desired channel, resulting in a minimum IIP3 of −4.4dBm.