A L-band active cold noise source for radiometer calibration

For application in radiometer calibration, a L-band(1400-1430MHz) active cold noise source(ACNS) is designed. A hybrid circuit has been realized with a Pseudomorphic High Electron Mobility Transistor(pHEMT), lumped elements and microstrip transmission lines. At ambient temperature, the ACNS exhibits an excellent noise temperature of only 68.7 K, a return loss higher than 25 dB and a negative temperature sensitivity of -1.64 K/O in the 1400-1430 MHz frequency range.