The AD8339 is a quad channel
I/Q demodulator, configured by a low noise preconfiguration with differential outputs
amplifierdrive and optimized for the LNAs used in the AD8332/AD8334/AD8335 family of VGAs. The device contains four identical I/Q demodulators with a 4x local oscillator (LO) input, which divides this signal and generates the internal 0° and 90° phase internal LOs required to drive the mixer. Each of the four I/Q demodulators uses different RF inputs and is therefore completely independent of each other (assuming a common LO is acceptable).
The AD8339 combines continuous wave (CW) analog beamforming (ABF) and I/Q demodulation in a single 40-lead, ultracompact chip-scale device, making it ideal for high-density ultrasound scanners. In ABF systems, time-domain consistency is achieved through proper phase alignment and multi-receiver channel summation. The reset pin synchronizes multiple ICs to start each LO divider within the same quadrant. Each channel has sixteen programmable 22.5° phase increments. For example, if Channel 1 is used as the reference channel and Channel 2 is 45° ahead of the I/Q phase, the user can phase align Channel 2 and Channel 1 by selecting the correct code.
The mixer output is in the form of a current for easy summing. The output currents of the independent I and Q mixers are summed and converted to voltage by a low noise, high dynamic range, current and voltage (I-V) transimpedance amplifier such as the AD8021 or AD829. After the current is summed, the combined signal is applied to a high resolution analog-to-digital converter (ADC) such as the AD7665 (16-bit, 570 kSPS).
The device provides an SPI-compatible serial interface port for easy phase programming of each channel; This interface allows data to be shifted from SDI to SDO through each chip, enabling daisy-chaining. SPI also allows individual channels and the entire chip to be shut down separately. During shutdown, the serial interface remains active, allowing the device to be programmed again.
The dynamic range of the I and Q outputs is typically 160 dB/Hz. The AD8339 is available in a 6 mm × 6 mm, 40-lead LFCSP package and is specified over the industrial temperature range of −40°C to +85°C.
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Medical imaging (CW ultrasonic beamforming)
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