Design Of High Linearity Current-mode Mixer And Current-mode Programmable Gain Amplifier

With the development of digitizing analog broadcasting, the research of the receiver ICs for DRM (Digital Radio Mondiale) and DAB (Digital Audio Broadcasting) is of great significance for the development of radio communication ICs in our country.The DRM/DAB reciever proposes a dual-conversion low-IF system architecture. The research objects of this paper are the circuits of current-mode mixer (CMixer) and Current-Mode Programable Gain Amplifier (CPGA).The CMixer input is 35.452 MHz first IF voltage singnal, the Lo is 37.5 MHz voltage singnal, and the output is 2.048 MHz second IF current singnal. The CMixer proposed in this paper consists of a dynamic Gm-stage, passive switch pairs, and the current amplifier stage. The current from the Gm-stage pass through the passive switch pairs and final through the current mode amplifier to drive out. The bias of passive switch pairs using dynamic bias technology to overcome the influence of voltage, process and temperature.The input and output signal of the CPGA proposed in this paper are current signals, the center frequency of the CPGA is 2.048 MHz, bandwidth of CPGA is 1.536 MHz. The CPGA takes the current summing network to get current gains. And a DC offset cancellation circuit is used to suppress DC gain, to reduce the instability resulting from mismatch. In addition, an active resistance instead of passive resistance is to reduce the layout area. Also, a digital control logic decoder is used to reduce the number of pads.Two circuits are both designed and tapeouted in standard SMIC’s 0.18-μm RFCMOS technology. Most of the test results meet the targets. After analyzing the test results, some suggestions for future work are given.