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A monolithic hbt active tunable bandpass filter
A monolithic hbt active tunable bandpass filter
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机译:单片HBT有源可调带通滤波器
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摘要
An active tuneable band-pass filter is provided which has a negative resistance circuit for generating a tuneable amount of negative resistance for a passive band-pass filter structure so as to compensate for resistive losses. The negative resistance circuit has a bipolar transistor with a base connected in shunt to the passive filter structure and a collector connected to a shunt inductive element. A negative resistance is generated at the base of the transistor and is applied to the passive filter structure. A coarse Q-factor tuning circuit is coupled to the emitter of the transistor for providing a coarse amount of tuning of the negative resistance. Also connected to the emitter terminal, is a fine tuning circuit for providing fine tuning of the negative resistance. The fine tuning may be achieved manually or automatically with a control circuit. The coarse and fine tuning capability provides a tuneable negative resistance which eliminates oscillations and compensates for resistive loss variations to realize improved q-factor.
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