Zetex chip in satellite dishes

Zetex new chip, ZXHF5000, with a switch matrix; polarisation and band selection logic; and cable drivers is specially developed for the low-noise blocks that sit in front of satellite dishes. These separately receive four channels and multiplex them on to one, two, or four coax cables. “This has never been done before and needed special engineering in the chip layout and the package layout," Zetex development engineer Geoff Stokes told EW." “European satellite operators are typically recommending a minimum isolation figure of 26dB," said Stokes. “We achieved 30dB of channel to channel isolation at 2GHz. The device has 19dB of gain, so the isolation had to approach 50dB or more", he adds. According to Electronics Weekly the firm used CST Microwave Studio, a 3D high-frequency field simulator, to evaluate pin-out and lead-frame options. “This was a very difficult development. We eventually chose a wire-bonded QFN package with slightly-modified lead-frame," Stokes told EW. “After simulation it took more than one physical iteration of the package, and an adjustment of the position of metal tracks on the chip, to get it right", he added.