The Design Of A Mixer Based On Low Voltage Supply Circuit

Since 60's, the development of the integrated circuit has been following the Moore law: The integration level of the integrated circuit increases four times every 3 years, and the characteristic size contracts two times in the same time. The characteristic size contracts to make the electric field enlarge in the transistor, which causing hot-carrier effect and grid oxygen broken through and breaking the function of circuit sometimes. So we have to lower the power supply voltage of the circuit along with the contraction of the characteristic size.Being an important part of the radio frequency communication circuit—mixer, its most in common use topology is a double balanced mixer topology—active Gilbert topology. Aiming at the application for the low power supply voltage circuit, the traditional way is to reduce the dc voltage decline of the trans-conductance by change its topology. This kind of method can satisfy the circuit request to some extent. But, lower further along with the power supply voltage, the weakness of this kind of project rears increasingly: non-conducting or poorly conducting switches conveying voltages in the"middle voltage range"between the supply voltages and unsteady of the output voltage due to the effect of clock feed-through; the output resistance for higher conversion gain occupying a large parts of the dc voltage which making the descend circuits work in a worse function due to a deficient working voltage.In order to solve this problem, this paper deals with a"switched trans-conduct or"mixer topology. Note that it is easily possible to make a low ohm switch without oxide reliability issues, provided that its conductive channel is connected to either Vss(NMOST) or Vdd(PMOST). Low ohm switches reduce switch voltage headroom to almost zero. At the mean time, noise caused by switches transistor converted to common mode noise rejected by the differential output structure. Assuming ideal switching, it realizes a transfer function equivalent to a conventional active mixer. The current paper analyzes the mixer performance in detail and compares it to a conventional active mixer. Competitive performance is found, while operating at a much lower supply voltage. In the output- terminal, we take a version of folded-output, reducing the fall of the direct voltage caused by the load resistance, solving the problem that the descend circuits work in a worse function due to a deficient working voltage, and finally achieve the purpose using for the low voltage supply circuit. The simulation results of this circuit on the condition of 1.3V voltage supply show that conversion gain is -11.5dB, noise figure is 20.65dB, 1dB gain compression input power level is -5.65dBm, and IIP3 is 4.7dBm.