Heterodyne mixing of two microwave signals has been observed for the first time at 77 K in Bi-(Pb)-Sr-Ca-Cu-O thin-film mixers patterned on MgO substrates. A number of different device designs were tested (all at 77 K) with an RF signal of 26 GHz and 36 GHz. In each case the mixers were subharmonically pumped with a 12 GHz local oscillator. The resulting IF signals observed were in the 1 MHz-2 GHz range with signal to noise typically 60 dB. The maximum IF frequency observed was 8 GHz. Investigation of IF output power as a function of applied RF power revealed a linear relationship whereas IF power as a function of local oscillator power exhibited a maximum at a local oscillator power of -10 dBm. Down-conversion of a 26 GHz carrier modulated with a 1.6 MHz test signal was also achieved.
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