DVB-S Half-NIM Tuner Reference Design Uses the MAX2120 Tuner
Figure 1. DVB-S Half-NIM reference design features the MAX2120 tuner.
Important Design Features:
- 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
Figure 2. System block diagram
Lab Measurements
Supply Current
| Parameter | Conditions | Measured | Units |
| Supply Current | LNA supply 3.3V, Ta = +25°C | 26 | mA |
| Supply Current | LNA + MAX2120 3.3v, tA = +25°C | 115 | mA |
Main Signal Path Performance
Test conditions include VCC =+3.3V; RF input signals as specified in the following table; default register settings; and Ta = +25°C.
| Parameter | Test Conditions | Frequency | Measured | Target | Units |
|---|---|---|---|---|---|
| RF Input Frequency | 950 to 2150 | — | — | MHz | |
| Input Return Loss (75Ω system) | Measure at input port | — | < -6 | < -6 | dB |
| Overall Voltage Gain | Unbalanced source impedance = 75Ω, GC1 = 0.5V and GC2 = +15dB | 1050MHz | 91 | > 80 | dB |
| 1550MHz | 88 | ||||
| 2150MHz | 83 | ||||
| Noise Figure | GC2 = +10dB, GC1 = 0.5V | 1050MHz | 5.5 | < 7 | dB |
| 2150MHz | 7.45 | ||||
| I/Q Amplitude Error | Measured at 2MHz; filter bandwidth set to 22MHz | — | 0.25 | < ±1 | dB |
| I/Q Quadrature Phase Error | Measured at 2MHz; filter bandwidth set to 22MHz | — | < 2.5 | < 3.5 | Deg |
| IIP3 (In Band) | GC1 set to provide the nominal baseband output drive when mixing down a -23dBm tone at 2055MHz to 5MHz baseband (fLO = 2050MHz). GC2 set for 7dB gain. Two tones at -26dBm each are applied at 2056MHz and 2060MHz. The IM3 tone at 2MHz is measured at baseband. | — | -1.5 | -2 | dBm |
| IIP3 (Out of Band) | GC1 set to provide the nominal baseband output drive when mixing down a -23dBm tone at 2055MHz to 5MHz baseband (fLO = 2050MHz). GC2 set for 7dB gain. Two tones at -20dBm each are applied at fLO -100MHz and fLO -195MHz. The IM3 tone at 5MHz is measured at baseband. | — | 10 | 5 | dBm |
| IIP2 (Broadband) | GC1 set to provide the nominal baseband output drive when mixing down a -23dBm tone at 2175MHz to 5MHz baseband (fLO = 2170MHz). GC2 set for 7dB gain. Two tones at -20dBm each are applied at 925MHz and 1250MHz. The IM2 tone at 5MHz is measured at baseband. | — | 12.5 | 14 | dBm |
| Phase Noise | 1kHz offset, fLO =1000MHz | — | -73.3 | -70 | dBc/Hz |
| 10kHz offset, fLO = 1000MHz | -85.6 | -82 | |||
| 100kHz offset, fLO = 1000MHz | -108.1 | -102 | |||
| 1MHz offset, fLO = 1000MHz | -120.8 | -122 | |||
| Local Oscillator Signal Leakage at RF Input Terminal | Measured at RF input port with 50MHz increment step from 925MHz to 2175MHz | — | < -80 | < -63 | dBm |
Loop-Through Performance
| Parameter | Conditions | Measured | Target | Units |
| Frequency Range | 925MHz to 2175MHz | -- | -- | MHz |
| Return Loss at TV_OUT | Antenna Input Terminated with 75Ω | < -6 | < -6 | dB |
| Power Gain at TV_OUT | -- | -.04 to 2.8 | -1 to 3 | dB |
| Noise Figure at TV_OUT | -- | < 5.5 | < -6 | dB |
| TV_OUT to ANT_IN Isolation | -- | 35.1 | 35 | dB |
System Performance
DVB-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.
Detailed Description
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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