The AD8340 vector modulator performs arbitrary amplitude and phase modulation of an RF signal. Because the RF signal path is linear, the original modulation is preserved. This part can be used as a general-purpose RF modulator, a variable attenuator/phase shifter, or a remodulator. The amplitude can be controlled from a maximum of −2 dB to less than −32 dB, and the phase can be shifted continuously over the entire 360° range. For maximum gain, the AD8340 delivers an OP1dB of 11 dBm, an OIP3 of 24 dBm, and an output noise floor of −149 dBm/Hz, independent of phase. It operates over a frequency range of 700 MHz to 1.0 GHz.
The baseband inputs in Cartesian I and Q format control the amplitude and phase modulation imposed on the RF input signal. Both I and Q inputs are dc-coupled with a ±500 mV differential full-scale range. The maximum modulation band- width is 230 MHz, which can be reduced by adding external capacitors to limit the noise bandwidth on the control lines.
Both the RF inputs and outputs can be used differentially or single-ended and must be ac-coupled. The RF input and output impedances are nominally 50 Ω over the operating frequency range. The DSOP pin allows the output stage to be disabled quickly to protect subsequent stages from overdrive. The AD8340 operates off supply voltages from 4.75 V to 5.25 V while consuming approximately 130 mA.
The AD8340 is fabricated using the Analog Devices, Inc. proprietary, high performance 25 GHz SOI complementary bipolar IC process. It is available in a 24-lead RoHS-compliant LFCSP package and operates over a −40°C to +85°C temperature range. Evaluation boards are available.
APPLICATIONS
- RF PA linearization/RF predistortion
- Amplitude and phase modulation
- Variable attenuators and phase shifters
- CDMA2000, GSM/EDGE linear power amplifiers
- Smart antennas
