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Linear RMS RF power detector targets 3G/4G handsets

Posted: 18 Aug 2010     Print Version  Bookmark and Share

Keywords:RMS  RF  power detector  3G/4G handsets 


National Semiconductor Corp. debuts the LMH2120, a linear root-mean-square (RMS) radio frequency (RF) power detector that offers high precision with up to 40dB dynamic range. The PowerWise LMH2120 offers increase in wireless coverage and extension of battery life for third-generation (3G) and fourth-generation (4G) mobile handsets.

National's LMH2120 linear RMS RF power detector enables accurate RF power amplifier (PA) measurements, which are used to control transmit power and avoid interference with neighbouring signals. The LMH2120 provides stable performance over the full temperature range of -40�C to 85�C, with a temperature variation of just ±0.5dB over a wide 40dB dynamic range at 1900MHz, minimising guard bands. This feature increases coverage and quality of service, such as higher uplink data rates at greater distance from the cell tower.

The LMH2120's performance remains consistent across various modulation schemes in multi-mode handsets and data cards using CDMA, W-CDMA, UMTS, LTE, GSM and GPRS cellular standards. It provides modulation-independent measurements of less than 0.3dB, which eliminates the extensive look up tables required for accuracy. The LMH2120 also includes a shutdown pin for reducing power consumption in between measurements to extend handset battery life.

The LMH2120 linear RMS RF power detector operates from a single 2.7V to 5V supply and provides an output voltage proportional to the RF input power in dBm. This minimises the need for extra calibration and reduces the resolution requirement for the system's analogue-to-digital converter. Handset designers can connect the LMH2120 to the output of the PA with a directional coupler or a resistive tap.

The LMH2120 features a supply current of 2.9mA and includes a low-power shutdown-mode that reduces power consumption to 3.8µA. It supports frequencies of 50MHz to 6GHz, with an RF power detection range of -35dBm to 5dBm.

The LMH2120 joins the recently released LMH2110 LOG RMS RF power detector. The LMH2110 provides precise control of RF PAs operating from 50MHz to 8GHz, with an RF power detection range of -40dBm to 5dBm.

The LMH2120 is available now and is supplied in a small 0.82mm by 1.22mm, 6-bump microSMD package. It is priced at Rs.112.73 ($2.40) each in 1,000-unit quantities.

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