SKY74702

The SKY74702 device is a single-supply, monolithic integrated circuit. It is designed for use in single-mode Code Division Multiple Access (CDMA) cellular voice/data applications including extensions for CDMA-Japan.

The SKY74702 is a highly integrated superheterodyne transmitter that incorporates the following components:

• In-Phase and Quadrature (I/Q) modulator accepts the analog I and Q current outputs from the baseband analog processor and converts them to Intermediate Frequency (IF) signals
• Voltage Controlled Oscillator (VCO) and VHF synthesizer generates the LO signal for the quadrature modulator
• UHF synthesizer controls the UHF oscillator
• Variable Gain Amplifier (VGA) provides the variable output  power for CDMA systems
• Image reject upconverter and power amplifier (PA) drivers

The signal of SKY74702 enters the chip as a baseband I/Q signal, which is upconverted by an I/Q quadrature modulator. The resulting signal is fed through a VGA to provide variable output power. After leaving the open collector output of the VGA, the signal enters a switch matrix. This switch matrix of SKY74702 allows the signal to be routed through an external filter, or it can be filtered by the tuned collector load and passed directly to the UHF image reject mixer.

The image reject mixer is internally connected to the PA driver. The mixer driver combination has a variable gain control that can be used to reduce the RF gain, which improves the in-band  Signal-to-Noise Ratio (SNR) at a lower output power. The PA driver amplifies the RF signal to the appropriate level  for the desired output power. This is then filtered by a bandpass filter and sent to an external PA to obtain the final rated output power at the antenna.

The SKY74702 package and pinout for the 40-pin RF Land Grid Array (RFLGA) are shown in Figure 1. A block diagram of the SKY74702 is shown in Figure 2.