RF Multiplexer 8ch 1GHz
This is a PCB-design + Arduino firmware for an Ethernet-controlled 1:8 RF-multiplexer (SP8T). It allows selecting as output one of eight input-channels, as commonly used e.g. in timing-laboratories when one wants to measure many RF-sources (clock outputs like 1PPS or 10MHz) with a single instrument (frequency or time-interval counter). The unselected channels are terminated at 50 Ohms. The design is for two independent MUX-boards to fit in a 1U 19” rack enclosure together with an Arduino MKR ZERO microcontroller with Ethernet interface. The firmware allows for simple control over http with a browser or e.g. the python requests library.
- PDF design files 2018.02: Schematic and PCB
- SP8T: 8 inputs, 1 output. Nominally 50 Ohm characteristic impedance. BNC or SMA connectors.
- Bandwidth >1 GHz
- TE HF3 signal relay with lifetime of 1e7 operations (19 years at a rate of one operation per minute)
- older design: Arduino Duo + Ethernet Shield controller
- current design: Arduino MKR Zero + Ethernet Shield controller
- 10/100 Mbit/s Ethernet, simple control over HTTP (see vide of initial tests https://youtu.be/fustqTdP5m0)
Components and datasheets
- TE HF3 Relay
- MCP23S17 16-Bit SPI I/O Expander with Serial Interface
- ULN2803A Darlington Transistor Array
- TAPR TASS DC-150 MHz
- k5lxp 6x2 Coaxial Remote Antenna Switch
- Pulse Research Labs PRL-8108 DC to 1.5 GHz SP8T multiplexer with 3-bit control. $ 1,707.75.
- Mini-Circuits RC-2SP6T-A12 DC to 12 GHz 2SP6T multiplexer with USB and Ethernet control. SMA connectors. Around $2395.
Design and general questions
- Anders Wallin (anders.e.e.wallin "at" gmail.com)
|2018-02-15||First PCB revision http://www.anderswallin.net/2018/02/rf-multiplexer-first-try/|
|2018-04-25||Second PCB revision http://www.anderswallin.net/2018/04/rf-multiplexer-version-2/|
|2018-06-12||OHWR-page rf-mux-8ch created|
|2018-06-17||initial commit of design to repository: mux-board, due2sata board, enclosure, mux-sw|
|2018-08||simplified design with no on-board voltage regulators and 10-pin IDC-cable for control.|
|2018-11-24||design update for kicad5 symbols and footprints|
|2019-09-07||Arduino MKR Zero carrier board files on wiki|
|2019-11-27||Revised carrier for Arduino MKRZero, with front-panel pushbuttons|
|2020-03||40-channel 3-unit 1PPS measurement system in operational use at VTT MIKES|
|2020-09||Revised mux-PCB with SMA-connectors as option|
|2020-11||Revise schematic to note that MCP23S17 io-expander address bits A0, A1, A2 must be externally driven (not left floating)|
Revised front-panel with pushbuttons B1 and B2. From S/N 4 onwards (2019-11).:
Internal view of S/N 4. Rightmost is the MKR ZERO Ethernet shield, followed by the MKR ZERO, and the carrier-board which takes +5VDC input and has two 10-pin IDC ribbon-cables to the MUX boards.
3x1U MUX-units for a 40-channel 1PPS measurement system. Installed at the VTT MIKES UTC-laboratory in March 2020. The boards are connected (cables not shown) in a tree configuration. One 8-channel MUX-board is used as the root node, where each channel connects to a leaf-MUX. This provides a capacity of 8x8= 64 channels, if seven leaf-MUXs are used. Here we only have 6 MUX-boards in 3U, so 5x8= 40 channels. This system is in continuous 24/7 use with all channels measured every 600s (10 minutes).
Transmission bandwidth test on S/N 4. Note Y-scale is 3 dB/DIV. Bandwidth is >1 GHz.
Older prototype with Arduino Due: