VLSI Implementation of 8-PSK/8-QAM/16-QAM Transmitter Circuit in CMOS Technology

In this paper a VLSI implementation of 8-PSK/8-QAM/16-QAM transmitter using the same circuit architecture in CMOS technology is presented. The circuit is used for transmissions in the ISM radio bands at a carrier frequency of 433 MHz. In order to simplify the circuit implementation, all digital modulations provided by the proposed transmitter present message points that use combinations of only two distinct values of their coordinates. As consequence, the circuit provides the same average transmission power for all modulations and uses the same circuits for all component blocks, except for the number of levels used by the digital modulation and their digital control logic. The operation of the proposed transmitter has been analyzed considering an AWGN communication channel and a receiver circuit model. In the paper the constellation diagram and the signal trajectory of all digital modulations implemented in the transmitter circuit are plotted and the bit error rates have been calculated. The simulations performed in 180 nm CMOS technology confirm the mathematical results.