Low Noise Traveling-Wave Maser Receiver for Three Millimeter Wavelength

A traveling-wave maser amplifier, using iron-doped rutile as the active material, has been developed in the frequency range 85 - 95 GHz. The device has demonstrated stable traveling-wave maser gain over an instantaneous bandwidth of 140 MHz and is capable of operation as a low noise receiving system for radio astronomy and communication applications in the millimeter wavelength region of the spectrum. The maser device uses a newly developed hybrid transmission mode allowing for easy coupling of the maser material to the microwave circuit. The mode, termed the slot-fed image guide mode provides high slowing and filling factor and is relatively easy to match over a wide bandwidth. Increased system sensitivity of an order-of-magnitude can be expected using this device as an alternative to state-of-the-art cooled Schottky-barrier mixer receivers.