RF switch yields improved performance in broadband cable systems

August 21, 2013 // By Graham Prophet
PE42720 75Ω RF switch features exceptional linearity and isolation performance

The PE42720 75-Ohm RF switch for broadband cable systems is manufactured on Peregrine’s UltraCMOS technology; the HaRP-enhanced single-pole, double-throw (SPDT) switch features high linearity, leading isolation performance and excellent video feedthrough, for higher data rates in cable modem termination systems (CMTS), multi-service headends, cable television (CATV) optical transceivers, fiber hubs, optical network terminals, and CATV amplifier modules.

Optimised for high linearity and isolation performance, the PE42720 supports increasing data rates as required by the industry transition to DOCSIS 3.1. High linearity minimises distortion in the cable network to support new modulation schemes such as 4096-QAM, while the ability to support high isolation between RF ports minimises unwanted signal interference. This combination is critical as DOCSIS 3.1 relies on orthogonal frequency-division multiplexing (OFDM) to improve spectral efficiency, allowing a 50% increase in data rates up to 10 Gb/sec downstream and 1 Gb/sec upstream.

“As the cable television market moves to OFDM to increase data rates, manufacturers will need to make improvements in efficiency in all parts of the system by reducing noise, intermodulation distortions, and ingress,” said Mark Schrepferman, director of the commercial and industrial product line with Peregrine’s High performance Solutions Business Unit.

This switch features high isolation performance of at least 60dB across the entire broadband frequency range of 5 MHz to 3 GHz (65 dB at 1 GHz (typ) and 64 dB at 2 GHz). The device features excellent video feedthrough of 5 mVpp for reduced distortion, and delivers low insertion loss (0.7 dB @ 1 GHz and 0.8 dB @ 2 GHz), which enhances overall system performance by reducing RF path noise figure. In addition, high linearity with a CTB/CSO of -104 dBc improves dynamic range of CATV systems. The PE42720 supports 1.8V and 3.3V control logic and has ESD performance of 2500V HBM on all ports. There is an evaluation kit to accompany the PE42720; the chip costs $1.06 (10,000).

Peregrine; www.psemi.com