LNB base type understanding

1. LNB is an important part of the design of the set-top box. Understanding the working mechanism and type of LNB helps us to locate the problem more quickly when debugging the code 2, frequency calculation: C segment output intermediate frequency = local vibration frequency-downward frequency Ku segment output intermediate frequency = downward frequency-local vibration frequency 3. Band downward frequency range: C band: 3.4-GHz to 4.2GHz (difference 800 MHz), calculate the intermediate frequency 950 to 1750 based on the local vibration of 5150 MHz, which covers the full range Ku band 10.7GHz to 12.75GHz (difference 2000 MHz), including 100700 MHz 11700 MH 2 is low frequency band: 1170012750 MHz is high frequency band, so there is a macro KU LNB 22K EDGE FREQUENCY 11700 in ALI project to judge switching wood vibration in ku band. According to the above example, the Ku band cannot cover the whole range through a local vibration, and the two extreme values of the local vibration are calculated as: low local vibration: 10700-950 = 9750 (MAX), high local vibration: 12,750-2150 = 1,0,600 (MIN) (2150 is the boundary, and 950 is the intermediate frequency boundary, the resulting local vibration is 11750-950=10750. Basic summary Ku Band: Downlink frequency-Local vibration = intermediate frequency (the frequency range received by the receiver) (min, max) -9750=950,2150) (min = 10700max = 11900) 9750 cannot cover (10,700,12750) the entire Ku band (min, max) -10,600 = (2150) (min =11550, max = 12,750) combined with local vibration at 10600. C band: local vibration-down frequency = IF (frequency range received by the receiver) 5150- (max, min)=(950, 2150)》(min = 3000, max= 4200) 5750-(max, min)=(950, 2150) (min = 3600max = 4800) C band downward frequency range is 3400 ~ 4200 MHz; the downward frequency range of u segment is 1070012750MH (1070011800 is low frequency band, 11700~12750 for the high frequency band) The range of Ku band is relatively wide, and it cannot cover the 10700~12750MH2 of the whole Ku band with a single local vibration frequency. In order to cover the whole Ku band, so there is LNB with double local vibration frequency. Generally, there are two kinds of Ku bands LNB, namely 9750 / 10600MH and 9750 / 10750 MHz, can cover the whole Ku band. Generally, there are two kinds of LNB with single vibration frequency, namely 10750MH and 11300MH2, C band