# Workspace Here lies any code/digital work created during the project. This includes design files, measurement data, photographs and more. This is the main folder to be worked in. | Folder | Description | | ----------------------------------------------------------- | ------------------------------------------------------------------------------------------------------------------- | | [`nmr_probe`](./nmr_probe/) | Probe and Probe construction | | [`marcos`](./marcos/) | MaRCoS software and control of the spectrometer | | [`32-channel_current_source`](./32-channel_current_source/) | Digitally controllable current source for driving the shims | | [`tr_switch`](./tr_switch/) | Transmit/Receive Switch for Switching between High-Power RF impulse transmission and low level FID signal reception | | [`rx_lna_preamp`](./rx_lna_preamp/) | Low-Noise Amplifier for the amplification of the FID signal for the RedPitaya | | [`tx_power_amp`](./tx_power_amp/) | Power Amplifier to amplify the excitation pulse of the RedPitaya | ## General Setup ```text +------------+ +--------------+ | | |\ |\ | RX/TX Switch | | | | \ | \ | | | TX |-----| +----------| +---------------------|---x \ | \ | / | | | / | / | \ | \|/ | | |/ |/ | \ | | | | ZFL-1000+ ZHL-3A+ | \ | | | Red Pitaya | | +---|-----------+ | | | | | | /| /| /| | | | | / | / | / | | | | RX |-----+ |----------+ |---------+ |--------|---x | | | \ | \ | \ | | | | | \| \| \| | | | | ZFL-500LN+ PHA-13LN+ PHA-13LN+ | | +------------+ +--------------+ ``` ## Previous NMR Work - Designing and building a low-cost portable FT-NMR spectrometer in 2019: A modern challenge (Alain Lous-Joseph, Philippe Lesot) - OpenCore NMR (Kazuyuki Takeda) - LabTools NMR spectrometer based on RedPitaya - Pavel Demin's NMR spectrometer - [Simple Low-Cost Tabletop NMR for chemical-shift-resolution spectra measurements](https://www.sciencedirect.com/science/article/pii/S1090780718301745#b0110). Home-built magnet, 60Hz resolution at 2.45MHz (58.8mT), in a later paper down to 1ppm. ## NMR Spectrometer Target Specifications In addition to the [thesis description/project proposal](../literature/project_proposal/Master_Thesis_Proposal.pdf) we tried to meet the following specifications. This includes design requirements for the physical setup partially repeated in the various sub-sections in the `workspace` directory. Hardware should be reusable. The end goal would be of type "Bring your own Magnet", i.e. a Red Pitaya SDRLab 122.88, our board and magnet should be enough to do spectroscopy, when building their own probes. - Larmor Frequency: 25MHz (0.6T) - RF-field strength: x.xx mT - pi/2 pulse length: x.xx us > **TODO** > Write down NMR target specifications here In the end, separate modules should be developed for ease of reconfiguration. A nice addition would be a single board, including RX/TX amplifiers, switch and filters on one standard [Eurocard 3U (100mm x 160mm x 1.6mm)](https://en.wikipedia.org/wiki/Eurocard_(printed_circuit_board)) FR4 board, so it can be rack mounted, possibly with the common [DIN 41612](https://en.wikipedia.org/wiki/DIN_41612) (~~STEbus~~, VMEbus) connector at the back end. See also the [ARTIQ/Sinara project](https://github.com/sinara-hw/SiLPA_HL/issues/1). ## Red Pitaya SDRlab 122-16 (STEMlab 122-16) The ADC of the RedPitaya is specified for an RF input voltage of 0.5Vpp. Its absolute maximum rating is 30VDC and 1Vpp RF (~4dBm). This has been verified by looking at the [used ADC](https://www.analog.com/media/en/technical-documentation/data-sheets/218543f.pdf) and the [RedPitaya Schematic](../../literature/instruments/Customer_Schematics_STEM122-16SDR_V1r1(Series1).PDF). Thus the input has to be protected from the power of the transmit cycle. The easiest way to do this is to use a TVS diode for clamping the input to safe levels. Unfortunately, this severely degrades the ADCs performance according to [this Analog Devices Application Note](../../literature/instruments/rf-samp-adc-input-protection.pdf). The same AN suggests using [RB851Y](https://www.mouser.com/datasheet/2/348/rb851y-209815.pdf) Schottky diodes for ADC input protection ### Basic Specs | | | | ------------------ | ------------------------- | | Processor | DUAL CORE ARM CORTEX A9 | | FPGA | FPGA Xilinx Zynq 7020 SOC | | RAM | 512 MB (4 Gb) | | System Memory | Micro SD up to 32 GB | | Console Connection | Micro USB | | Power Connector | Micro USB | | Power Consumption | 5 V, 2 A max | ### RF Inputs | | | | --------------------------------- | ------------------------------------- | | RF input channels | 2 | | Sample rate | 122.88 MS/s | | ADC resolution | 16 bit | | Input impedance | 50 Ohm | | Full scale voltage range | 0.5 Vpp/-2 dBm | | Input coupling | AC | | Absolute max. Input voltage range | DC max 50 V (AC-coupled) 1 Vpp for RF | | Input ESD protection | Yes | | Overload protection | DC voltage protection | | Bandwidth | 300 kHz - 550 MHz | ### RF Outputs | | | | ----------------------- | -------------------------------- | | RF output channels | 2 | | Sample rate | 122.88 MS/s | | DAC resolution | 14 bit | | Load impedance | 50 Ohm | | Voltage range | 0.5 Vpp/ -2 dBm (50 Ohm load) | | Short circut protection | N/A, RF transformer & AC-coupled | | Connector type | SMA | | Output slew rate | N/A | | Bandwidth | 300 kHz - 60 MHz | Next Steps: 1. Build 2x Protection diode blocks with 2x BYS-10 schottky diodes each for input protection (limit power to 4dBm/+-0.5V/1Vpp)