Date: 20/12/2010

RF envelop detector for 3G/4G/LTE/ WiMAX systems to boost power amplifier efficiency

Analog Devices (ADI) has introduced a new RF detector for use in wireless, instrumentation, defense, and other broadband applications. ADI's new ADL5511 TruPwr rms (root mean square) and envelope detector (an electronic circuit that takes a RF signal as input and provides an output that represents the envelope of the signal) combines two RF functions in single chip.

ADI suggests, "improving the PAE (power added efficiency) of high-powered amplifiers continues to be a challenge for wireless and broadband equipment manufacturers. Next-generation WiMAX systems and LTE mobile data and voice systems are adopting OFDM (orthogonal frequency division multiplexed) modulation that supports a large number of subcarriers. The high peak-to-average ratio of these modulated signals causes PAs (power amplifiers) to be backed off from their maximum transmit powers significantly, thereby making the PA less efficient. To improve PA efficiency, an envelope detector has become increasing popular. In drain modulation architectures, an envelope detector modulates the PA power supply from the incoming RF signal, thereby only giving the PA the power needed to properly transmit the RF signal. Traditional architectures leave the PA biased at a much higher power level in order to ensure the PA can properly transmit peak power, but are not capable of reducing PA bias when transmitting lower RF power."


Operating within the 1 MHz to 4 GHz frequency range, ADI's new ADL5511 TruPwr rms and envelope detector improves PAE through means of extracting the envelope of a modulated signal. The envelope output is presented as a voltage that is proportional to the envelope of the input signal. The rms output is a linear in V/V output voltage that is independent of the peak-to-average ratio of the input signal. The extracted envelope can be used for power amplifier linearization and efficiency enhancements, and the rms output can be used for true power measurement. The ADL5511 offers best-in-class performance including ±0.25 dB rms detection accuracy versus temperature; ±0.25 dB envelope detection accuracy versus temperature and a ± 1 dB dynamic range of 40 dB. The ADL5511 is specified across the industry's widest temperature range of -40°C to +125°C, making it ideal for high-temperature environments found in remote radio heads and power amplifiers.

Availability: Now in Samples
Price: Each $7.33 per unit in 1K

Editorial product Rating: ** (Average Plus)

Major Drawback: High cost