tailieunhanh - TEAM FLY WIRELESS NETWORK DEPLOYMENTS phần 6

là tần số sóng mang, mức độ đầu vào phức tạp, và đại diện các đặc điểm được và giai đoạn của PA. Thuật ngữ bóp méo giai đoạn là đại diện cho sáng để có hiệu lực PM nhìn thấy trong nhiều thiết bị phi tuyến. Các chức năng này bình thường có thể được bắt nguồn từ một thử nghiệm duy nhất âm, nơi ảnh hưởng của PA biến dạng trên một tần số từ bắt. [11], | 126 Chapter 6 v . t Re pty v O Re A p 2 W 46 where A is the carrier frequency p is the input complex magnitude and Afl I and Oh I represent the gain and phase characteristics of the PA. The phase distortion term is to represent the AM to PM effect seen in many nonlinear devices. These functions can normally be derived from a single-tone test where the effects of PA distortion on a singular frequency are haptured. In 1111. the authors demonstrate that by sis Illg this model they were able to effectively annulate their tao-stege gallium-arsenide MESFET amplifier and demonstrate the device s compliance with emission requirements for PCS CDMA. Due to gain and phase distortion cpectral de-growth results in at the autput of the PA. This is troublesome due to the need to meet specific electromagnetic compatibility requirements. Moreover input stages to the PA which provide spurious products will contribute difficulty in meeting the required spectral emissions mask. 4. CONCLUSIONS intermodulation distortion in IS-95 Uaadset transceivers is particularly troublesome for both oeception and transmission. However if one can isalnie the source of the interference resulting in intermodulation one can compensate for this in either the receive or aransmit paths. For the receiver accurate detection of tee presence of intermodulation is important. Once this is achieved then appropriate action may be taken to ensure that intermodulation products do not captoe the receiver. For the aransmitter intermodulation compensation may be accomplished by IQ-balancing and DC-offset compensation. REFERENCES 111 TIA EIA IS-95-A Mobile Station-Base Station Compatibility Standard for Dual-Mode Wideband Spread Spectrum Cellular System. The Telecommunication Sndustry Association. Intermodulation Distortion in CDMA Handsets 127 2 Hamied Khalid and Gerald Labedz. AMPS Cell Transmitter Interference to CDMA Mobile ReceiverIEEE Vehicular Technology Conference. May 1996. pp. 1467-1471. 3 .ioyce Timothy. .