Wireless Infrastructure: Hi-Perf WiMAX 802.16, 2.5-3.5 GHz BTS RX/TX

In Hi-Perf WiMAX 802.16, 2.5-3.5 GHz BTS RX/TX, Baseband data is interpolated and filtered in the DUC. The DUC presents parallel IQ data to the dual DAC. The DAC provides high speed data conversion of the IQ data. In addition, phase, gain and offset correction of the IQ imbalance are possible using the full featured DAC capabilities. With a complex baseband input, an interpolating DAC can be used to increase the effective data rate through interpolation. The process of complex mixing to translate the signal frequency from baseband to an IF frequency produces sideband and LO feed through, at the IQ modulator output, that falls outside the signal band of interest. The IQ-modulator is capable of performing at frequencies from 0.4-4 GHz, and is thereby suitable to meet the popular WiMAX frequency bands. The CDC/M provides clock recovery, jitter cleaning functions, and is used to generate all the necessary system clocks. SerDes devices provide the parallel-to-serial conversion to implement a high speed interconnect between Baseband and RF cards. The receive chain down converts RF to IF through one analog mixing stage. The ADC converts the IF to a combined IQ for the DDC which provides digital down conversion and carrier/channel selection.

Benefits

Direct up conversion architecture reduces RF BOM.

Supports a wide range of RF frequency bands.

Nonharmonic clock-related spurious signals fall out-of-band.

Tradeoffs

Quadrature modulator I/Q imbalance.

I/Q channel gain mismatching, offset.

Noise performance.

• All Data Converters Block Diagrams