This wiki describes the Oregon Ions programmable ultra-low AM noise rf source.

The Squareatron 5000+ consists of a Squareatron 5000 board, a DAC add-on board, and an aluminium case.

The v1.0 Squareatron board was originally designed by the Oxford Ion Trap Group and can be found here. This project uses the v1.1 version modified by Oregon that can be found here. Hopefully we'll eventually merge these changes.

The DAC add-on board is this repository and the CAD files for the case can be found here.

Shown below are the schematic diagrams for the Squareatron and the DAC tuning board that can be used for reference and will be referred to for the changes that have been made.

Squareatron setup

Every squareatron has had some modifications made to the squareatron to connect to the DAC tuning board. The squareatron is not ready to use out of the box and a couple adjustments have been made to enable operation. Detailed in this section is all of the changes that have been made.

Input filtering

The squareatron has some initial filter that has to be set. Initially all of the jumpers are populated which results in the board shorting.

The filtering specifications are: Every board in production has R7 and R8 removed to set FLTA: High and FTLB: Low

Differentiating Tune and Reference Voltage

** Please note that the castellation for the DAC board has the reference and tuning lines label reversed.**

The Squareatron is designed to run on the reference voltage supplied to the DAC tuning board. This being so, R13 was removed to cut the lines between the reference voltage and the tuning voltage.

Available Boards

Shown in the table below is all of the boards that have finished testing and are ready for use All board were tested under the same conditions with an supply of 5.5V from a Rigol DP832 power supply. The boards range in current draw from 49 mA - 51 mA with power dissipation of 270 mW - 281 mW. The SXBP-35W filter is the only DC coupled filter used in production which results in a current of 65 - 69 mA and 350-380 mW of power. RF was being supplied during testing from the Sinara Urukul outputing 9.73 dBm at 30 MHz. 30 MHz is not the center of the pass band for all filters and results in different output powers. SQTD+08 is a special filter for lower frequency and was tested at 19.6 MHz with other conditions the same.

Serial Number	Band Pass Filter	DAC range (V)	Output Range (dBm)
SQTD+00	SXBP-29	0.0073 - 3.2988	10.07 - 9.21
SQTD+01	SXBP-29	0.0065 - 3.2990	10.06 - 9.20
SQTD+02	SXBP-29	0.0070 - 3.2989	10.07 - 9.20
SQTD+03	SXBP-29	0.0072 - 3.2988	10.10 - 9.24
SQTD+04	SXBP-35W	0.0068 - 3.299	10.40 - 9.47
SQTD+05	BPF-C45	0.0071 - 3.299	10.28 - 9.41
SQTD+06	BPF-C45	0.0074 - 3.298	10.16 - 9.30
SQTD+07	BPF-C45	0.0065 - 3.299	10.22 - 9.36
SQTD+08	SXBP-20R5+	0.0070- 3.298	8.62 - 7.74

DAC Programming

The DAC on board is a the AD5541 16-bit DAC. Initial testing of this device was done by bit-banging TTL pulses on the DIO_RJ45 from Sinara. The code used can be found here and is called spi_timing.py