High Performance, High IF, 75 MHz Bandwidth, 14-Bit, 250 MSPS Receiver Front End with Band-Pass Antialiasing Filter (CN0242)
The circuit, shown in Figure 1, is a 75 MHz bandwidth receiver front end based on theADL5202 wide dynamic range, high speed, digitally controlled variable gain amplifier (VGA) and the 14-bit, 250 MSPS AD9643 dual analog-to-digital converter (ADC).
The fifth-order Butterworth antialiasing filter is optimized based on the performance and interface requirements of the amplifier and the ADC. The total insertion loss due to the filter network and other resistive components is approximately 2.3 dB. The overall circuit with the band-pass filter has a 1 dB bandwidth of 75 MHz (from 145 MHz to 220 MHz) and a 3 dB bandwidth of 110 MHz (from 120 MHz to 230 MHz). The pass-band flatness is 1 dB.
The circuit is optimized to process a 75 MHz bandwidth IF signal centered at 182.5 MHz (second Nyquist zone) with a sampling rate of 245.76 MSPS. The signal-to-noise ratio (SNR) and spurious-free dynamic range (SFDR) measured with a 182.5 MHz analog input across the 75 MHz band are 68.4 dBFS and 80.7 dBc, respectively.
Figure 1. Single Channel of Quad IF Receiver Front End (Simplified Schematic: All Connections and Decoupling Not Shown), Gains, Losses, and Signal Levels Measured Values at 10 MHz
Схемы и диаграммы
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