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EVB71111-915-FM-C 参数 Datasheet PDF下载

EVB71111-915-FM-C图片预览
型号: EVB71111-915-FM-C
PDF下载: 下载PDF文件 查看货源
内容描述: 868 / 915MHz的接收器评估板说明 [868/915MHz Receiver Evaluation Board Description]
分类和应用:
文件页数/大小: 14 页 / 614 K
品牌: MELEXIS [ Melexis Microelectronic Systems ]
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EVB71111  
868/915MHz Receiver  
Evaluation Board Description  
By using the internal PLL synthesizer of the TH71111 with the fixed feedback divider ratio of N = 16  
(DIV_32), two types of down-conversion are possible: low-side injection of LO and high-side injection of LO.  
The following table summarizes some equations that are useful to calculate the crystal reference frequency  
(REF) and the LO frequency, for a given RF and IF.  
Injection type  
low  
high  
REF  
LO  
(RF – IF)/32  
32 REF  
RF – LO  
RF – 2IF  
(RF + IF)/32  
32 REF  
LO – RF  
IF  
RF image  
RF + 2IF  
1.6.1 Selected Frequency Plans  
The following table depicts crystal, LO and image signals considering the examples of 868.3 MHz and  
915 MHz RF reception at IF = 10.7 MHz.  
Signal type  
Injection type  
REF / MHz  
RF = 868.3 MHz  
low  
RF = 868.3 MHz  
high  
RF = 915 MHz  
low  
RF = 915 MHz  
high  
27.46875  
879.0  
28.92813  
925.7  
26.80000  
857.6  
28.25938  
904.3  
LO / MHz  
RF image / MHz  
889.7  
936.4  
846.9  
893.6  
The selection of the reference crystal frequency is based on some assumptions. As for example: the image  
frequency should not be in a radio band where strong interfering signals might occur (because they could  
represent parasitic receiving signals), the LO signal should be in the range of 800 MHz to 930 MHz (because  
this is the optimum frequency range of the VCO1). Furthermore the IF should be as high as possible to  
achieve highest RF image rejection. The columns in bold depict the selected frequency plans to receive at  
868.3 MHz and 915 MHz, respectively.  
1.6.2 Maximum Frequency Coverage  
Parameter  
Injection type  
RF / MHz  
fmin  
high  
789.3  
25.0  
800  
fmax  
low  
940.7  
29.0625  
930  
REF / MHz  
LO / MHz  
IF/ MHz  
10.7  
10.7  
39012 71111 01  
Rev. 011  
Page 5 of 14  
EVB Description  
June/07