The ALPHA250 is a programmable board built around a Zynq 7020 SoC. It features a 100 MHz RF front end with 14-bit ADCs and 16-bit DACs, at 250 MSPS. The RF channels are clocked by a dual PLL, ultra-low jitter clock generator. It includes a 4-channel 24-bit ADC and a 4-channel 16-bit DAC. The board comes with a comprehensive, open source, FPGA / Linux reference design.
- 12 V 1.5 A power supply
- Micro-SD card with pre-installed OS
|Programmable logic, processor and memory|
|System On Chip||Zynq 7020 XC7Z020-2CLG400I||Zynq 7020 XC7Z020-2CLG400I|
|Memory||512 MB of DDR3L SDRAM||512 MB of DDR3L SDRAM|
|Processor||ARM dual-core CPU (Cortex-A9)||ARM dual-core CPU (Cortex-A9)|
|100 MHz low-noise RF front-ends|
|RF ADC||2 channels, 14-bit, 250 Msps, DC coupled||4 channels, 14-bit, 250 Msps, DC coupled|
|RF DAC||2 channels, 16-bit, 250 Msps, DC coupled|
|Input to output latency||90 ns|
|Input / Output||1 Vpp, 50 Ω||1 Vpp, 50 Ω|
|Ultra-low jitter clock for RF ADC, DAC and FPGA|
|Clock generator||Dual loop PLL, 100-fs RMS jitter (12 kHz to 20 MHz)||Dual loop PLL, 100-fs RMS jitter (12 kHz to 20 MHz)|
|On-board VCXO||160 dBc / Hz @ 10 kHz||160 dBc / Hz @ 10 kHz|
|Reference clock inputs||FPGA, external clock or internal crystal oscillator||FPGA, external clock or internal crystal oscillator|
|On-board TCXO||10 MHz, 280 ppb||10 MHz, 280 ppb|
|Precision analog monitoring and control|
|Precision ADC||4 channels, 24-bit||4 channels, 24-bit|
|Precision DAC||4 channels, 16-bit||4 channels, 16-bit|
|Voltage reference||2.5 V, low-drift (3 ppm/°C)||2.5 V, low-drift (3 ppm/°C)|
|Temperature sensor||±0.2 °C accuracy||±0.2 °C accuracy|
|Connectivity||10/100/1000 Ethernet, USB 2.0, USB-UART||10/100/1000 Ethernet, USB 2.0, USB-UART|
|General purpose I/O||3V3 16 FPGA I/Os, 8 user LEDs||1V8 16 FPGA I/Os, 8 user LEDs|
|Outside Dimensions||113 mm x 108 mm x 27 mm||113 mm x 108 mm x 27 mm|
|Operating temperature range||-10 °C to 60 °C||-10 °C to 60 °C|
|OS||Ubuntu 16.04||Ubuntu 16.04|
|Reference designs||FFT Analyzer, ADC / DAC with BRAMs, ADC / DAC with DMA, Phase noise analyzer, Loopback||FFT Analyzer, ADC with BRAMs|
The RF ADC and DAC noise floors were characterized with this script available on GitHub. The input referred voltage noise density of the ADC is about 13 nV/√Hz. DAC voltage noise density is about 23 nV/√Hz (19 nV/√Hz after subtraction of the ADC noise floor).
Below is the representation of the noise floor for the 4 ADC version (ALPHA250-4) inputs (50 ohm terminated):
ADC front end frequency response
A 1 Vpp sine wave between 100 kHz and 40 MHz was send by DAC0 and measured by ADC0 (see script). The figure below shows the amplitude of the second and third harmonic, relative to the fundamental frequency:
Distortion performance is limited by the DAC. ADC distortion (HD2 and HD3) stays under -80 dB up to 40 MHz.
The crosstalk between the 2 ADC channels was characterized with the following script. The crosstalk is under -95 dB up to 120 MHz.
The crosstalk between the two DAC channels is shown below:
The phase noise of a 10 MHz OCXO reference clock (from Textronix MCA 3027) against the internal TCXO was measured with the Phase Noise Analyzer reference design:
Input to output latency
Using the loopback reference design, we observe the delay between a pulse in input (green) and the reproduced pulse at the output (yellow) for the ALPHA250 - 2 ADC, 2 DAC version:
Loopback latency is 90 ns, corresponding to a π/4 phase shift at 1.4 MHz.
Temperature stability of voltage reference and precision DAC
Temperature stability of precision DAC measured by precision ADC
DAC output voltage is set to 1 V on channels 0 and 1. Precision DAC output is connected to precision ADC input.
Since the voltage references of the precision DAC and the precision ADC are derived from the same voltage reference, the above measurement realizes a ratiometric measurement which rejects voltage reference drifts. Note that the 2.5 V reference avalaible on the expansion connector can also be used for ratiometric measurement.
- 2: October 2018 - Improved DAC crosstalk.