Tapered distributed analogue tunable phase shifter with low insertion and return loss

Some improvements for distributed Schottky diode tunable phase shifters are carried out. First, near- and far-end sections are tapered to improve return loss. Then, to reduce device length, and the number of varactors, inductances are added in series with the varactors, leading to an improved Cmax/Cmin ratio. For a 360° tunable phase shifter working at 1 GHz, insertion losses are limited to 2.4 dB maximum. Return loss is better than 20 dB. The tapered sections allow a wide working frequency range, typically from 800 to 1200 MHz with the same characteristics: around 2.4 dB insertion losses, 20 dB return loss.