EXPERIMENTAL TUNNEL-DIODE CONVERTER FOR CONVERSION OF X-BAND FREQUENCIES TO UHF
AIR FORCE CAMBRIDGE RESEARCH LABS HANSCOM AFB MA
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A tunnel-diode down converter designed and developed for conversion from X-band frequencies to UHF has proved that low noise figures are possible, when a forward bias voltage is chosen in the first region of the I-V characteristic of the tunnel diode so that the conductance Go is positive. When a sufficient local-oscillator voltage can drive the operating point into the negative-resistance region, the tunnel diode down converter exhibits a conversion gain and a noise figure 3 to 4 db lower than attainable with converters having common diodes. With a local oscillator frequency of 8.33 kMc and an IF of 30 mc, an average noise figure of 4.5 db was measured. For mismatched conditions of the in put admittance, a generator conductance Gg of 2 mhos was advantageously chosen in order to get a low noise factor and high gain. A microstrip line transformer was used to establish the high generator conductance. The measured noise figure of an improved second device, similar to the first one, was 3.0 db. The experimental devices are of attractively small size.
- Electrical and Electronic Equipment
- Electricity and Magnetism