如何制作适配12GHz辐射成像装置双偏振实验的电磁波偏振器？

Great question! I’ve tinkered with Ku-band (12GHz falls right in this range) polarization setups using off-the-shelf satellite hardware, so let’s break down practical, doable ways to build a polarizer that works for your experiment.

1. Wire Grid Polarizer (Most Reliable & Easy to DIY) #

This is the go-to for RF polarization—think of it as the RF equivalent of a visible-light polarizing filter. The principle is simple: electromagnetic waves with electric field parallel to the grid wires get absorbed/reflected, while waves with electric field perpendicular pass through.

• Calculate grid specs: At 12GHz, the wavelength λ is ~2.5cm (λ = c/f, where c=3×10⁸ m/s). Your grid spacing needs to be much smaller than λ—aim for 2.5mm to 5mm (λ/10 to λ/5). Narrower spacing = better polarization rejection. Keep wire width as thin as possible (≤1mm) to minimize signal loss for the allowed polarization.
• DIY construction:
  • Grab an insulating substrate: FR-4 circuit board, acrylic sheet, or even stiff cardboard (avoid conductive materials!).
  • Apply copper foil to one side, then use a laser cutter, hobby knife, or vinyl cutter to etch/cut parallel, evenly spaced lines. If you don’t have a cutter, you can also glue thin copper wires (0.1–0.5mm diameter) onto the substrate with epoxy, making sure they’re perfectly parallel and tight.
  • Make the grid larger than your receiver’s antenna aperture (at least 2x the size) to ensure the entire RF beam passes through the polarizer.
• Use case: Mount the grid on a rotating bracket, and you can easily replicate the classic "crossed polarizers" experiment—rotate the grid to see signal drop to near zero when it’s perpendicular to your receiver’s polarization.

2. Repurpose Satellite TV Components #

Since you’re already using satellite hardware, you can leverage existing Ku-band parts to avoid building from scratch:

• LNB Polarization Modification: Most Ku-band LNBs (low-noise blocks) support switching between horizontal and vertical polarization via a voltage. You can disassemble an old LNB, extract the internal polarization selector (a metal plate or waveguide with a slot), and mount it on a rotating holder. This will act as a precise polarizer tailored for 12GHz.
• Used Waveguide Polarizers: Ku-band waveguide polarizers are common in satellite communications. You can find used ones from surplus electronics stores that are pre-tuned for 12GHz. These are more precise than DIY grids, perfect if you need high polarization isolation.

3. Quick & Cheap Wire Array (For Prototyping) #

If you need a polarizer fast for a test run, this is the way to go:

• Build a frame using plastic or wood (non-conductive).
• Stretch thin copper wires across the frame, keeping them parallel and spaced 2.5–5mm apart. Secure the ends tightly with tape or screws to prevent sagging.
• Test it immediately: Point your 12GHz source at your receiver, then rotate the wire array. You should see a clear drop in signal when the wires are parallel to your receiver’s polarization axis.

Pro Tips for Testing & Optimization #

• Verify Polarization Isolation: Use your receiver’s signal strength meter to measure how much signal is blocked when the polarizer is crossed with your receiver’s polarization. Aim for at least 10dB of isolation (a 10x drop in signal) for a good experimental setup.
• Circle Polarization (If Needed): To replicate circular polarization experiments, add a 1/4-wave plate after your wire grid. For 12GHz, use a PTFE (polytetrafluoroethylene) sheet with a thickness of ~1.5cm (calculated as λ/(4*(n-1)), where n=1.4 is PTFE’s refractive index). Mount the wave plate at a 45° angle to the wire grid, and you’ll convert linear polarization to circular.

内容的提问来源于stack exchange，提问作者JRE