CPRI Serdes delivers ±800ps delay calibration accuracy

National Semiconductor Corp. has introduced an advanced common public radio interface (CPRI) Serdes for next-generation base station architectures. National said the device is the first to guarantee ±800ps delay calibration measurement accuracy and exceed all CPRI interface signal voltage and jitter requirements.

Moreover, the SCAN25100 CPRI Serdes uses dual on-board PLLs to automatically synchronize remote radio heads to the digital processing base station. These features enable distributed base station architectures that use multiple antenna technologies to increase radio efficiency, deployment flexibility, and maximize capacity and coverage, while lowering backhaul, site property and bandwidth costs.

In addition to next-generation GSM, CDMA, W-CDMA, CDMA2000, WiMAX, TD-SCDMA and other base station architectures, the new CPRI Serdes is also suitable for radar, satellite, test equipment, medical imaging, particle accelerator equipment and other high-performance data transfer applications.

Distributed base station architectures decentralize radio electronics by moving the radio circuits from the base station to their respective antennas. These remote radio heads (RRHs) are a challenge because they introduce interconnect delay and synchronization issues for the central base station. With its patent-pending precision delay calibration measurement (DCM) circuitry and independent transmit and receive PLLs, the new CPRI SerDes measures delays and synchronizes the RRHs with the central base station without additional components or complicated system intervention.

A next major step toward improving cellular capacity and coverage at lower per-MB cost is to use multi-element beam-steering "smart" antennas and multiple-input, multiple-output antennas within RRHs. These multiple antenna systems, however, can have even tighter timing requirements. Calibrating delays between the base stations and these RRHs is difficult to perform accurately using traditional logic approaches. To track fiber delay changes as small as 200ps, the new CPRI Serdes integrates DCM circuitry to measure base station-to-RRH and RRH-to-RRH fiber delay components with a guaranteed ±800ps accuracy. This patent-pending DCM circuitry also reports the chips own deterministic latency and measures off-chip system delays as well. DCM operates transparently and does not interrupt the CPRI data link. The system software can launch DCM as often as every five milliseconds if required, such as when tracking fiber delay changes over temperature.

As an option, the SCAN12100, a reduced-speed of 1228.8Mbps and 614.4Mbps version with the same features as the SCAN25100, is also available.

Available today, the SCAN25100 CPRI Serdes is priced at $14.60 and the SCAN12100 is priced at $10.05 each in 1,000-unit quantities.