Bridged T delay equaliser

Another application occurs when stereophonic sound is connected by landline, for instance from an outside broadcast to the studio centre.

When the landlines are long and the two channels arrive by substantially different routes it can require many filter sections to fully equalise the delay.

Transformer action between the two halves of L, which had been steadily becoming more significant as the frequency increased, now becomes dominant.

For television purposes, a maximum frequency of 6 MHz might be chosen, which corresponds to a delay of 83ns.

In general, much greater attention is paid to the routing and exact length of television cables because many more equaliser sections are required to remove the same delay difference as compared to audio.

Losses in the circuit cause the maximum delay to be reduced, a problem that can be ameliorated with the use of high-temperature superconductors.

The traces are the superconductor yttrium barium copper oxide and the substrate is lanthanum aluminate.

The circuit is for use in the microwave band and has a centre frequency of approximately 2.8 GHz and achieves a peak group delay of 0.7 ns.