Electronic Design

Third UWB Method Solves The Home Networking Problem

Ultra-Wideband (UWB) is that weird wireless technology that spreads the signal over at least 500 MHz of bandwidth between 3.1 and 10.6 GHz, achieving blazing data rates at a range up to 10 m. Fully blessed by the FCC in February 2002, it has seen some frenetic action over the past five years as designers look for a wireless solution for personal-area networks (PANs) and home entertainment connectivity.

There are three types of UWB: impulse radio, orthogonal frequency-division multiplexing (OFDM), and CWave, created by Pulse-Link. Impulse radio came and went for military applications during the 1960s and 1970s, generating a very wide bandwidth that had to be restricted to the microwave range. OFDM-style UWB, which has seen its own share of changes, has range and reliability issues that may not fit all applications.

Pulse-Link resisted the OFDM UWB bandwagon and developed CWave, which utilizes a continuous sine-wave carrier modulated with a special version of binary phase-shift keying (BPSK) (Fig. 1). This technology starts with a 4.05-GHz carrier that is XORed with the serial digital data at 1.35 GHz.

The data pulses are timed to produce three cycles of carrier for each bit or symbol using BPSK (180° shift between symbols). The resulting signal extends from 2.7 to 5.3 GHz for a bandwidth of 2.6 GHz, which is enough to fit the definition of true UWB. Its power level meets the FCC's strict maximum of –41 dBm.

And CWave isn't just a wireless technology. It was additionally created to match up to cable TV coax within the home. Using the same standard, you can put together a hybrid wireless/cable TV coax system that's compatible with the exact equipment you have and where it's located.

Pulse-Link's solution is implemented in a three-chip set known as the PL3100, which will work in both wired and wireless products (Fig. 2). The PL3120 RF transceiver is unique, as it directly digitizes the incoming signal with a rate of 10.7 Gsamples/s. It then parallelizes the signal and sends it to the PL3130 baseband chip for down-conversion, demodulation, and filtering, in addition to other functions.

The PL3130 handles part of the modulation tasks. But the final modulation takes place in the RF chip, which also includes the transmit power amplifier. On-chip phase-locked loop (PLL) synthesizers set the operating frequency. A separate low-noise amplifier (LNA) chip, the PL3110, is used ahead of the receiver to provide extra sensitivity.

CWave's baseband chip is the workhorse of the set. It implements a full 802.15.3b media access controller (MAC). It also can handle asynchronous or isochronous data and provide full quality-of-service (QoS) traffic support. Other features include an advanced forward error correction (FEC) method known as low-density parity check (LDPC) and a piconet coordinator for wireless connectivity.

The physical-layer (PHY) data rate is selectable from 21 to 675 Mbits/s, depending on the level of FEC needed to achieve the desired QoS. The chip set works with Ethernet, IEEE 1394, and HDMI high-speed serial interfaces. These external interfaces attach to the baseband chip's PCI bus.

Whether you're designing an HDTV set, DVD, DVR, media center PC, high-end audio system, set-top box, or gaming system, the CWave chip set is an interesting option to consider.


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