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Coax power supply, fixed voltage

An easy and quick building of "Coax power supply, fixed voltage" module based on the SMD components and used for powering up active antennas and amplifiers through a coaxial cable. The module includes a schematic and PCB GERBER files prepared for setting up into aluminum enclosure with dimensions 80 x 50 x 20 mm with SMA connectors. Based on the submitted files, you can order PCB manufacturing at the factory (PCBWay, JLCPCB). In turn, I developed PCB for the independently manufacturing based on the existing circuit. As a result, the self-made manufacture of the "Coax power supply, fixed voltage" module is cheaper than buying a ready-made device.

Current development progress:

Progress Progress

Current available implementations at EasyEDA platform:

How does it work?

Coax power supply module is built on the principle of using Bias Tee. Bias Tees are the components, that are used to supply DC currents or voltages to bias RF circuits. Bias tee is a three-port device. A signal that consists of RF + DC is incident at port 1 of the Bias Tee. The capacitor blocks all DC signals from getting through to port 2 and only allows the RF signals to pass through. Whereas, the inductor in the circuit blocks all RF signals from getting through to Port 3 and allows all DC signals to get through.

Bias Tee schematic

A feature of this module is the stabilization of supply voltage for powering up different active antennas or LNA, which will allow to set a fixed value of the output voltage and avoid a situation where the antenna or LNA characteristics may change due to the instability of the supply voltage (for example, battery discharge). This decision will positively affect the quality of the work of active antennas or LNA and achieving stable performance throughout the entire operating time.

Basic characteristics of the Coax power supply, fixed voltage module:

  • Input voltage: USB type B, DC 5 V
  • Frequency range: 10 MHz - 10 GHz (according to the datasheet on TCBT-14+, upper frequency may be unattainable with FR-4 PCB material)
  • Output voltage: DC +3.3 V (can be changed by replacing the linear regulator LP5907MFX-3.3)
  • Maximum output current: 200 mA
  • RF connector: SMA
  • Feed line: 50 Ohm coaxial cable
  • Used PCB Material: FR-4
  • PCB thickness: 1.6 mm
  • PCB copper weight: 1 oz

Used only to power receiving antennas or amplifiers! Using the device in a transmitting radio channel can damage the TCBT-14+ (maximum allowable power is 30 dBm).

What was used in the development?

Source Description
What is a Bias Tee? A simple definition of the concept of Bias Tee.
Bias tee Wikipedia article describing the idea of Bias Tee in more detail.
#284: Basics of RF Bias Tees including applications and examples A video on YouTube telling basic things about the concept of Bias Tee, there are examples of design and using of different Bias Tees.