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ADPLP01 数据表(PDF) 3 Page - Analog Devices |
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ADPLP01 数据表(HTML) 3 Page - Analog Devices |
3 / 8 page AD20msp410 –3– REV. 0 decision confidence bits supplied by the equalizer. Once these decoding functions are complete, digitized voice data is trans- ferred to the ASP through a parallel port. Error control mecha- nisms are used to ensure adequate bad frame indication. Speech Decoding (ASP) Encoded speech data is transferred at 20 ms intervals from the PLP to the ASP in blocks of 260 bits plus the Bad Frame Indicator (BFI). The speech decoder supports a Comfort Noise Insertion (CNI) function that inserts a predefined silence descriptor into the decoding process. The ASP also implements control of talker side-tone and short term echo cancellation. The resulting data, at 104 kb/s, is transferred to the BBC through a dedicated serial path. Voice Digital-to-Analog Conversion The Voice DAC function of the BBC uses a sigma-delta con- verter to convert and noise shape the signal. The 13-bit linear values are converted to the analog domain and filtered to avoid any images. The resulting differential signals can be controlled in volume and drive directly a small earpiece as well as a separate auxiliary output. AUXILIARY SYSTEM FUNCTIONS The ASP, the PLP and the BBC perform a number of auxiliary functions which are essential to build a complete mobile radio. A general radio section constitutes the three functions of transmitter, receiver and synthesizer. Figure 2 shows how the baseband chipset interfaces to a typical radio architecture. The transmitter is fed with baseband analog I and Q signals from the BBC and upconverted to 900 MHz for GSM applications and 1800 MHz for PCN applications. A dedicated power amplifier increases the RF-signal to the required level. The receiver amplifies the antenna signal, down- converts it to an intermediate frequency (IF) and amplifies it there again. After second conversion to baseband, the I and Q components of the signal are fed into the BBC. The BBC, ASP and PLP provide three auxiliary functions for interfacing to the radio subsystem. These auxiliary functions include AGC, AFC and Power Ramping. Power Ramp Envelope (BBC) To meet the spectral and time-domain specifications of the transmitted output signal, the burst has to follow a specified power envelope. The envelope for the power profile originates in the PLP as a set of coefficients, down-loaded and stored in the BBC. This envelope profile is sent to one of the auxiliary DACs on the BBC with each burst. The analog output is fed into the RF power amplifier, controlling the power profile and absolute level of the transmitted data. Automatic Gain Control (AGC) The mobile radio has to cope with a wide range of input signal levels. The major part of the overall gain is provided in the IF amplifier. The incoming signal level is analyzed in the ASP and the PLP and a digital gain control signal is sent to the BBC. A 10-bit auxiliary DAC generates the appropriate analog control signal for the IF amplifier. Additionally gain control can be implemented by using two output flags of the ASP. FLAGS 13 MHz VCTCXO 13 MHz VCTCXO SYNTHESIZER CONTROL SIGNALS AGC AFC RAMP CONTROL AGC PAERROR LOCK 10-BIT DAC I Q I Q PLP ASP BASEBAND/AUXILIARY SECTION OF AD7015 DIGITAL FIR FILTER RAMPING RAM GSMSK MODULATOR BURST STORE PA IF TX DAC TX DAC 10-BIT DAC 10-BIT DAC 8-BIT DAC DIGITAL FIR FILTER DIGITAL FIR FILTER DIGITAL FIR FILTER DIGITAL FIR FILTER RX DAC RX DAC BASEBAND SERIAL INTERFACE AUXILIARY SERIAL INTERFACE Figure 2. Control of RF Section |
类似零件编号 - ADPLP01 |
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类似说明 - ADPLP01 |
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