High-Performance RF Power Detector Simultaneously Delivers rms and Envelope Outputs

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.



Envelope Output



Operating within the 1 MHz to 4 GHz frequency range, ADI’s new ADL5511 TruPwr rms and envelope detector provides a unique approach to improving PAE with a smaller footprint and reduced cost and is a highly accurate, easy-to-use 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 and Pricing



The ADL5511 is sampling now and is available for $7.33 per unit in 1,000-unit quantities.



RF IC Portfolio Covers Entire RF Signal Chain



Using a unique combination of design skills, system understanding and process technologies, Analog Devices offers the broadest portfolio of RF ICs covering the entire RF signal chain from industry-leading high-performance discrete RF function blocks to highly-integrated multi-functional single-chip RF solutions. ADI’s RF portfolio includes TruPwr™ rms power detectors and logarithmic amplifiers; PLL and DDS synthesizers; RF prescalers; VGAs; ADC drivers, gain blocks, LNAs and other RF amplifiers; RF mixers; direct conversion modulator and demodulator products; integrated transceivers, transmitters and receivers and more. These products are supported by a wide range of free design tools, evaluation boards and other design resources to ease the development of RF systems.