Cartesian Feedback Loop Transmitter
1. General Description
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 builtin 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.
● Frequency range: 50MHz to 1GHz
● Operation Voltage: 2.7 to 3.3V (Charge pump: 2.7~5.5V)
● Temperature range: -40~+85℃
● Forward path / Feedback path: 31dB gain control
● Forward path IQ modulator
● Feedback path IQ demodulator
● Integrated ΔΣ Fractional-N PLL
● 360 degrees phase shifter
● Active HPF for stability detection
● Integrated 12bit DAC
● 68-pin QFN (8 x 8mm, 0.4mm pitch) package 3. Application
● Narrow Band Radio Communication: 6.25kHz / 7.5kHz / 12.5kHz / 15kHz / 25kz / 50kHz / 100kHz / …