DVB-S Half-NIM Tuner Reference Design Uses the MAX2120 Tuner
Abstract: This reference design is a commercial Half-NIM DVB-S tuner that uses Maxim's MAX2120 satellite tuner IC. The reference design connects to the motherboard through a 12-pin connector. The downconverted satellite signal from the LNB is supplied to an active, discrete loop-through, which splits the signal into two paths. One signal goes to the MAX2120 and the other provides an additional output from the STB.
A Popular Form Factor Often Used in the Chinese DVB-S Market; Can Be Adopted Without Physical Modifications
Active Loop-Through Using a Discrete LNA
LNB 12V Power Feed-Through
Supply Current
Parameter
Conditions
Measured
Units
Supply Current
LNA supply 3.3V, Ta = +25°C
26
mA
LNA + MAX2120 3.3V, Ta = +25°C
115
mA
Main Signal Path PerformanceDVB-S system measurements for the MAX2120 Half-NIM are made by connecting to a DVB-S demodulator. Figure 3. The DVB-S sensitivity without noise is better than -92.5dBm for 4.42Msps, and better than -84dBm for 27.5Msps across the band.Figure 4. When noise is added, the DVB-S sensitivity is better than -85dBm for 4.42Msps, and better than -77.5dBm for 27.5Msps across the band. For this case, AWGN noise is added with C/N = 5dB. For the 4.42Msps data rate, the noise bandwidth is 5.7MHz; for the 27.5Msps data rate, the noise bandwidth is 35.2MHz. This MAX2120 reference design is a compact Half-NIM DVB-S tuner for satellite STB applications. The design covers the RF range from 925MHz to 2175MHz. The MAX2120 is a fully integrated silicon tuner, which includes a LNA, RF and IF VGAs, a mixer, and a variable-bandwidth LPF in the baseband stage. The tuner is powered by a single 3.3V supply. A small number of passive components are needed to form a complete DVB-S RF front-end solution.
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