BK Radio P150, Service Manual

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BK Radio Page 4-7
theory of operation
DAC and goes to one of the FET gates.
The AD9864 integrated circuit from Analog Devices accomplishes several important tasks for the
receiver’s backend. The device’s onboard LO Synthesizer compares the input LO voltage controlled
oscillator (VCO) frequency and the reference frequency provided by the TCXO and adjusts the LO
VCO control voltage so that the VCO maintains a stable frequency. The Clock Synthesizer also uses
the TCXO reference to create a clock signal for the IC’s digital functions. The input Low Noise Amplifier
(LNA) provides the necessary signal drive for the mixer. The mixer mixes the LO and the RF input
signals to down-convert the RF signal to the 2nd IF. This signal is then filtered and input into the analog-
to-digital converter (ADC). This converter samples the signal at a very high rate, but it is followed by a
series decimation filters. The bits are then formatted and stored in a buffer in preparation for transfer via
the SSI to the radio’s microprocessor. Ultimately, the sampled data is transferred to the microprocessor
at 19.2 k samples per second with 16 bits of data per sample.