Demodulator Targets High-Capacity Digital Modems

The ADL5387 high-performance, wide-input-range demodulator from Analog Devices Inc. enables high-capacity digital modems for microwave radio transmission and next-generation broadband access systems, such as 802.16 WiMAX and WiBro applications. High-capacity modems are implemented with higher-order modulation, like OFDM and 128QAM, across wider signal bandwidths. The ADL5387 addresses these requirements by integrating a highly accurate divide-by-two quadrature phase splitter with excellent amplitude and phase balance, and high-linearity Gilbert-cell mixers. The input frequency range is 50 MHz to 2 GHz.

The mixer cores offer high linearity (with a +30-dBm third-order intercept at 900 MHz) and excellent demodulation accuracy (with 0.1-dB amplitude and 0.5° phase accuracy). The highly balanced design provides greater than 60-dBc LO rejection and low second-order distortion—two specifications that are important in higher-order demodulation applications. Additionally, the ADL5387 features a 240-MHz demodulation bandwidth, which allows demodulation of the widest of input signal bandwidths. The baseband output stage delivers a conversion gain of approximately 5 dB and high output drive, which minimizes the need for auxiliary output amplifiers. Fabricated on the company’s XF3 silicon-on-insulator SiGe complementary bipolar process, the ADL5387 comes in a 24-lead small-footprint lead-frame chip-scale package.