GENERAL DESCRIPTION
The Quadrature Phase Shift Keying (QPSK) transmitter is a monolithic bipolar IC dedicated for quadrature modulation of the I and Q signals. It includes:
• Two double-balanced mixers
• Symmetrical Voltage Controlled Oscillator (VCO) with 0 to 90 degree signal generation for modulation
• Phase-Locked Loop (PLL) for IF frequency control
• Conversion mixer
• PLL for RF frequency control
• Gain controlled output amplifier
• 3-wire bus and an output buffer. Two PLLs are incorporated, the first PLL includes:
• Fixed main divider
• Crystal oscillator and its programmable reference divider
• Phase/frequency detector combined with a fixed charge pump.

The second PLL includes:
• Divide-by-four preamplifier
• 12-bit programmable divider
• Crystal oscillator and its programmable reference divider
• Phase/frequency detector combined with a ‘clever’ charge pump which drives the tuning amplifier, including 9 V output.

FEATURES
• Programmable gain
• PLL controlled carrier frequency
• 3-wire transmission bus
• 5 V supply voltage.

APPLICATIONS
• QPSK modulation.