Multi-carrier GSM can utilize the GXSC ADC/clock jitter eliminator as a replacement for the AD9689/HMC7044

In mobile communication networks, the multi-carrier deployment mode (multi-carrier GSM) significantly improves spectrum utilization and system capacity by aggregating multiple carriers within the same frequency band, making it suitable for scenarios with high communication demand, such as densely populated areas and transportation hubs.

The core challenge of multi-carrier GSM systems lies in achieving precise acquisition, efficient conversion, and stable transmission of multi-carrier RF signals—the system must simultaneously process multiple GSM carrier signals (typically 4 to 8), which are characterized by concentrated frequency bands, large amplitude variations, and susceptibility to interference. Clock jitter is one of the primary sources of interference in multi-carrier GSM signal acquisition. Even minor clock jitter can cause phase deviations in ADC sampling, leading to signal distortion and inter-carrier crosstalk, which degrades system demodulation performance and communication quality.

The GXSC ADC converts received analog signals into digital signals, providing an accurate data source for downstream processing, while the GXSC jitter eliminator supplies low-jitter, highly synchronized clock signals to the ADC and other digital components in the system, making it ideally suited for the signal acquisition requirements of multi-carrier GSM systems.

The GXSC ADC offers advantages such as wide input bandwidth, high sampling rates, excellent linearity, and a small package with low power consumption. The dual-channel ADC core employs a multi-stage pipelined architecture and integrates on-chip digital calibration algorithms. Each ADC features a wide-bandwidth input and supports a variety of user-selectable input ranges. An integrated reference voltage source simplifies design complexity. Both the analog input and clock signals are differential inputs, and several features are available to simplify automatic gain control (AGC) in communication receivers. A programmable threshold detector allows monitoring of incoming signal power using fast detection control bits in the ADC registers.

The clock jitter eliminator performs frequency conversion, selects a reference signal, and generates an ultra-low phase-noise clock to supply high-speed data converters for parallel or serial (JESD204B) interfaces. The chip provides 14 low-noise, configurable outputs that can be flexibly matched to many different device interfaces in RF transceiver systems, such as data converters, local oscillators, transmit/receive modules, FPGAs, and digital front-end (DFE) ASICs.

The chip can generate up to seven pairs of DCLK and SYSREF signals that comply with JESD204B interface requirements, featuring excellent crosstalk, frequency isolation, and spurious performance, and supporting both single-ended and differential output frequencies. The DCLK and SYSREF clock outputs can be configured to different output signal standards, such as CML, LVDS, LVPECL, and LVCMOS.