Frequency modulated oscillator for transmitting short range signals
OwnerShiu Hung Cheunginventor
Life of this patent
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Abstract
A broadcast transmitter for generating low power modulated signals, especially for a wireless speaker system. A signal source such as a source of composite audio signals including left and right audio signals and a pilot signal are applied to a radio frequency signal oscillator. The radio frequency signal oscillator includes a bipolar transistor connected in a common base configuration, and having a stripline element as a frequency determinative component in the collector circuit of the bipolar transistor. The modulating signal is applied to the base of the bipolar transistor which modulates the collector junction capacitance of the transistor thereby frequency modulating the signal produced by the oscillator. Varactor tuning is provided for setting a nominal frequency of oscillation.
Claims4
A broadcast transmitter for generating a low power modulated signal comprising:
- a source of composite signals;
- a bipolar transistor receiving said composite signals on a base thereof, having a collector connected to a stripline element exhibiting a resonance at a frequency within a wireless frequency band, and a feed back element connecting said collector to an emitter of said transistor which is in turn connected to a common terminal through a resistor, said base being capacitively connected to said common terminal;
- means connected to provide a d.c. voltage between said collector and said common terminal;
- and
- biasing means connected to said base for providing a bias current to said transistor wherein said transistor oscillates in a grounded base mode and the collector junction capacitance of said transistor changes in response to said composite signals correspondingly changing the frequency of oscillation.
Dependencies are inferred from the claim text.