Rf Modulator Applied Research And The Realization Of Cbb Circuit

In moderm wireless communication system, the direct RF-modulation for transmitting signal is a new developing trend of RF radio. The great advantages of the quadrature modulator is not only output the signal of higher power but also have well linearity, so the communication system can not use the IF circuits, to achieve the quality and reduce the cost.The thesis focuses in depth on the types and the application field of RF-modulator in the front of text. Firstly, having explained the work theory, mainly RF specifications, the reliebility test meature, summed the notice point of RF-modulator choice. The second, in the base of introduceing some modle application circuits, discused the reliability application of modulator and summed some reliability application points. Afterword, the hardware circuits of AD8345's CBB (COMMON BUILDING BLOCK) in 450MHz frequency channel including the baseband interface and local oscillator interface have designed for cdma 450 product. By the simulation analysis and measurement, the baseband interface can completely satisfy the request of providing the common DC and filtering the high order harmonic waves from AD9777. The result reveal that the within channel SWR of the local oscillator interface circuits are more excellent than the recomended circuis of producer and the outer channel SWR of the local oscillator interface circuits are also smaller than 12dB, so the feaquency draught of local oscillator signal can be suppressed at large.The reliability application points and circuit design theory of RF-modulator in this paper can be applied by any quadrature modulator. The CBB ciucuit by designed in this paper has strong applicability, because it can be applied in new frequency channel through simply replacing some parts. Through actual use in the cdma 450 product, the CBB ciucuit have manifested well performance and high reliability.