Interfacing the ADL5374 I/Q Modulator to the AD9779A Dual-Channel, 1 GSPS High Speed DAC (cn0020)
This circuit provides a simple, elegant interface between the ADL5374 I/Q modulator and the AD9779A high speed DAC. The ADL5374 and the AD9779A are well-matched devices because they have the same bias levels and similarly high signal-to-noise ratios (SNR). The matched bias levels of 500 mV allow for a "glueless" interface–there is no requirement for a level shifting network that would add noise and insertion loss along with extra components. The addition of the swing-limiting resistors (RSLI, RSLQ) allows the DAC swing to be scaled appropriately without loss of resolution or of the 0.5 V bias level. The high SNR of each device preserves a high SNR through the circuit.
Figure 1: Interface Between the AD9779A and ADL5374 with 50 Ω Resistors to Ground to Establish the 500 mV DC Bias for the ADL5374 Baseband Inputs (Simplified Schematic)
Схемы и диаграммы
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