As claimed by the company, Analog Devices unveiled its only converter which implants features required for multi-carrier generation to the Nyquist frequency in baseband mode for wireless macro base stations, point-to-point microwave radio, military radios and radio test equipment. The converter is a quad 16-bit D/A which integrates on chip phase locked loop (PLL) and eight-lane JESD204B interface in a single device.
A PLL is a control system that generates an output signal whose phase is related to the phase of an input signal. The oscillator generates a periodic signal. The phase detector compares the phase of that signal with the phase of the input periodic signal and adjusts the oscillator to keep the phases matched. Bringing the output signal back toward the input signal for comparison is called a feedback loop since the output is ‘fed back’ towards the input forming a loop.
On the flipside, JESD204B is a serial interface standard which was created through the JEDEC committee to standardise and reduce the number of data inputs/outputs between high-speed data converters and other devices, such as FPGAs (field-programmable gate arrays). Fewer inter-connects simplifies layout and allows smaller form factor realisation without impacting overall system performance. These attributes are important to address the system size and cost constraints of a range of high speed ADC applications, including wireless infrastructure (GSM, EDGE, W-CDMA, LTE, CDMA2000, WiMAX, TD-SCDMA) transceiver architectures, software-defined radios, portable instrumentation, medical ultrasound equipment and Mil/Aero applications such as radar and secure communications.
In reference to the press release, “The AD9154 DAC provides a maximum sample rate of 2.4 GSPS, permitting multi-carrier generation up to the Nyquist frequency in baseband mode. It includes features optimised for direct conversion transmit applications including complex digital modulation, input signal power detection and gain, phase, and offset compensation. The DAC outputs are optimised to interface seamlessly with the ADRF672x radio frequency quadrature modulators from Analog Devices, Inc. In the mix mode, the AD9154 DAC can reconstruct carriers in the second and third Nyquist Zones. A serial port interface (SPI) provides for the programming/readback of internal parameters. The full-scale output current can be programmed over a range of −4 mA to −20 mA. The AD9154 is available in an 88-lead LFCSP.”
Further the release mentions, “The AD9154 converter was designed with an eight-lane JESD204B interface that simplifies board layout by providing deterministic latency and multi-device synchronisation for radio transmitters that use multiple antennas—an increasingly common feature in wireless base stations, radar and military radio communications.”
The key features of AD9154 are listed below:
- Supports input data rates up to 1 GSPS
- Proprietary, low spurious and distortion design
- Single carrier LTE 20 MHz BW, ACLR = 76.7 dBc at 180 MHz IF
- Six carrier GSM IMD = 78 dBc, 600 kHz carrier spacing at 180 MHz IF
- SFDR = 72 dBc at 180 MHz IF, −6 dBFS
- Flexible 8-lane JESD204B interface
- Multiple chip synchronization
- Fixed latency
- Data generator latency compensation
- Input signal power detection
- High performance, low noise PLL clock multiplier
- Digital inverse sinc filter
- Digital quadrature modulation using an NCO
- “Mix mode” Nyquist Band Selection
- Selectable 1×, 2×, 4×, and 8× interpolation filters
- Low power: 2.11 W at 1.6 GSPS, full operating conditions
- 88-lead, exposed pad LFCSP