Problem Description
Design Challenges
The design and implementation of the 5G outdoor base station antenna is very challenging mainly due to the following reasons:
- Two-port isolation for dual-linear polarization.
- For use in base station antenna arrays which may require MIMO and smart-beam performance.
- Stable radiation pattern, beamwidth, efficiency and realized gain within the desired frequency bands and high polarization purity.
- Compact, light-weight, low profile, and low maintenance with a simple feeding structure
- Large fractional bandwidth requirement in the new sub-6 GHz spectrum covering the frequency bands, 3.3 GHz to 3.8 GHz and 4.8 GHz to 5.0 GHz.
AI-driven Design with Latest SADEA (in-house at the moment)
Optimization Problem
For the given 5G base station antenna structure, the specifications set as the optimization goals are as follows:
- Maximum reflection coefficient (S11) < -10 dB (3.3 GHz to 3.8 GHz)
- Maximum reflection coefficient (S11) < -10 dB (4.8 GHz to 5.0 GHz)
- Maximum reflection coefficient (S22) < -10 dB (3.3 GHz to 3.8 GHz)
- Maximum reflection coefficient (S22) < -10 dB (4.8 GHz to 5.0 GHz)
- Maximum transmission coefficient (S12) < -20 dB (3.3 GHz to 3.8 GHz)
- Maximum transmission coefficient (S21) < -20 dB (4.8 GHz to 5.0 GHz)
- Maximum transmission coefficient (S12) < -20 dB (3.3 GHz to 3.8 GHz)
- Maximum transmission coefficient (S21) < -20 dB (4.8 GHz to 5.0 GHz)
- Minimum realized gain (G) > 5 dBi (3.3 GHz to 3.8 GHz)
- Minimum realized gain (G) > 5 dBi (4.8 GHz to 5.0 GHz)
- Minimum half power beam width (HPBW) > 60 deg. (3.3 GHz to 3.8 GHz)
- Maximum half power beam width (HPBW) < 70 deg. (3.3 GHz to 3.8 GHz)
- Minimum half power beam width (HPBW) > 60 deg. (4.8 GHz to 5.0 GHz)
- Maximum half power beam width (HPBW) < 70 deg. (4.8 GHz to 5.0 GHz)
- Number of resonances (NR – S11) > 1 (3.3 GHz to 3.8 GHz)
- Number of resonances (NR- S11) > 1 (4.8 GHz to 5.0 GHz)
- Number of resonances (NR – S22) > 1 (3.3 GHz to 3.8 GHz)
- Number of resonances (NR – S22) > 1 (4.8 GHz to 5.0 GHz)
- Note that resonances are only required in the antenna’s operating bands when the returning loss is poor and return loss matching might be needed.
- Hence, if the return loss specification is met in any of the bands, it is assumed that a resonance exists and NR is defaulted to 1.
Layout of the 5G Outdoor Base Station Antenna
(a) The geometry of the 5G Outdoor Base Station Antenna: Crossed-dipole Radiator and Reflector Base
(b) L-shaped Feeding Structure of the 5G Indoor Base Station Antenna.
Ranges of the 23 Design Variables for the Design Exploration
For this case:
- The synthesized antenna by the latest SADEA (in-house at the moment) obtains the following results using 1087 EM simulations in 7.5 days.
- Maximum reflection coefficient (S11) = -11.77 dB (3.3 GHz to 3.8 GHz)
- Maximum reflection coefficient (S11) = -13.58 dB (4.8 GHz to 5.0 GHz)
- Maximum reflection coefficient (S22) = -11.14 dB (3.3 GHz to 3.8 GHz)
- Maximum reflection coefficient (S22) = -12.89 dB (4.8 GHz to 5.0 GHz)
- Maximum transmission coefficient (S12) = -32.27 dB (3.3 GHz to 3.8 GHz)
- Maximum transmission coefficient (S21) = -34.03 dB (4.8 GHz to 5.0 GHz)
- Maximum transmission coefficient (S12) = -32.23 dB (3.3 GHz to 3.8 GHz)
- Maximum transmission coefficient (S21) = -34.07 dB (4.8 GHz to 5.0 GHz)
- Minimum realized gain (G) = 7.45 dBi (3.3 GHz to 3.8 GHz)
- Minimum realized gain (G) = 7.89 dBi (4.8 GHz to 5.0 GHz)
- Minimum half power beam width (HPBW) = 69.35 deg. (3.3 GHz to 3.8 GHz)
- Maximum half power beam width (HPBW) = 69.57 deg. (3.3 GHz to 3.8 GHz)
- Minimum half power beam width (HPBW) = 66.63 deg. (4.8 GHz to 5.0 GHz)
- Maximum half power beam width (HPBW) = 66.94 deg. (4.8 GHz to 5.0 GHz)
- The measurement results are in close agreement with the simulation results.
- The size of the fabricated antenna is 60 mm x 60 mm x 18 mm.