Cartesian Feedback Loop Transmitter

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Two-way Radio ICs

The AK2403 is a transmitter IC with the Cartesian Feedback Loop Linearization Technique.  The AK2403 realize high linearity by receiving feedback signal from an external Power Amplifier (PA) via a coupler.  The core circuit of Cartesian Feedback Loop consists of forward path part and feedback path part.
The forward path consists of differential amplifier and I/Q modulator. And the feedback path consists of attenuator, demodulator, phase shifter and differential to single amplifier.  Since the AK2403 has a built- in DAC and PLL, the area of the system can be reduced.  The built-in PLL in the AK2403 can generate Local signal by using built-in VCO or external VCO.  The AK2403 can execute the DC offset calibration automatically by using the built-in DAC.

Key Features

● Frequency range: 50MHz to 1GHz
● Operation Voltage: 2.7 to 3.3V  (Charge pump: 2.7 to 5.5V)
● Temperature range: -40 to +85 ºC
● Forward path / Feedback path: 31dB gain control(1dB step)
● Forward path IQ modulator
● Feedback path IQ demodulator
● Integrated ΔΣ Fractional-N PLL
● 360 degrees phase shifter(in 5.625-degree step)
● Active HPF for stability detection
● Integrated 12-bit DAC
● 68-pin QFN  (8 x 8mm, 0.4mm pitch) package

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Block Diagram

Block Diagram

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