参考电路 4178

MAX2120 DVB-S Half-NIM调谐器参考设计




图1. MAX2120调谐器的DVB-S Half-NIM参考设计。

重要设计特性:

  • 采用中国DVB-S市场通用的外壳结构;无需修改即可使用
  • 采用分离的LNA有源环通
  • LNB 12V馈电

图2. 系统框图
图2. 系统框图


图1. MAX2120调谐器的DVB-S Half-NIM参考设计。

重要设计特性:

  • 采用中国DVB-S市场通用的外壳结构;无需修改即可使用
  • 采用分离的LNA有源环通
  • LNB 12V馈电

图2. 系统框图
图2. 系统框图

实验室测试

电源电流

Parameter Conditions Measured Units
Supply Current LNA supply 3.3V, Ta = +25°C 26 mA
LNA + MAX2120 3.3V, Ta = +25°C 115 mA

 

主信号通道性能
测试条件包括:VCC = +3.3V,RF输入信号规格如下表所示;采用默认寄存器设置;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
1650MHz 5.54
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

 

环通性能

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 -0.4 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

 

系统性能

将MAX2120 Half-NIM调谐器连接到DVB-S解调器进行DVB-S系统性能测试。


图3. 全频段内不加噪声情况下,DVB-S在4.42Msps码率下,系统灵敏度优于-92.5dBm;在27.5Msps码率下,灵敏度优于-84dBm。


图4. 全频段内加噪声情况下,DVB-S在4.42Msps码率下,系统灵敏度优于-85dBm;在27.5Msps码率下,灵敏度优于-77.5dBm。此时,AWGN噪声C/N = 5dB。对4.42Msps的数据速率,噪声带宽为5.7MHz;对于27.5Msps的数据速率,噪声带宽为35.2MHz。

详细说明

MAX2120参考设计为卫星STB提供了一个紧凑的Half-NIM DVB-S调谐器方案,该设计覆盖925MHz到2175MHz整个RF范围。MAX2120为完全集成的硅调谐器,内部包括LNA、RF和IF VGA、混频器以及一个可变带宽的基带LPF。该调谐器采用单电源3.3V供电,外部仅需要少量的无源元件即可组成一个完整的DVB-S RF前端方案。

 
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MAX2120
完备的直接变频调谐器,用于DVB-S和免费广播系统

  • 925MHz至2175MHz频率范围
  • 单片VCO:无需校准
  • -75dBm至0dBm高动态范围