A 2x2 pixel array for Sub-THz detection in which each pixel can be separately addressed has been integrated in a low-cost 0.18 mu m CMOS technology. Each pixel comprises of an NMOS incoherent power detection circuit and a high gain operational amplifier. Efficiency of self-mixing is analyzed and improved for FET detector and the operational amplifier. Sequential pulse generator is used in the design of row and column signal producing circuit in pixel array. The measured peak responsivity is 3.3 kV/W at 90 GHz, 4.3 kV/W at 155 GHz. For comparison, the pixel without load resistor is also characterized. The measured results show that the pixel with load resistor can efficiently increase the pixel output.