This PCB antenna is a flattened CoCo.
The two sides of the PCB antenna are two limbs in column 3 of this sketch
The wide strips shield the thin strips, just like the shield of a Coax. The thin strips therefore do not radiate, and just act as connection between wide strip pieces. The actual radiators are wide strips. The top piece of thin strip projecting above pcb is un-shielded and is therefore a radiator.
This weekend I will prepare it’s computer model and run the simulation.