John Collins

"It only works in waveguide arrays," John Collins, head of Fortel and phase shifter inventor told Electronics Weekly.

The firm specialises in arrays assembled from two metallised injection moulded plastic halves, leaving plenty of access for printing during manufacture.

The polymers used to construct the varactors remain a secret.Collins would however say that the diodes are voltage driven and are forward biased in operation.

Connections are through silver conductors which can be printed on the bottoms, tops and walls of waveguides, over an insulating layer.

Loss in a Collin's phase-shifting waveguide is around 1dB/m, he said, and 360 degrees shifting is possible.

Multi-layer varactors are available to increase capacitance per unit area at the expense of thickness, although "if it is on a waveguide wall, you want it as thin as possible to minimise return loss," said Collins.

In a 450mm diameter 14mm thick horizontally-mounted car-top antenna, the receive beam can be steered between 5 degrees from the vertical, 5 degrees from the horizontal, and in any direction around the vertical axis, claimed Collins.He also said the antenna would cost around $350 to make in quantity, including electronics.