MESFET-device surface-wave-device channel selector
AssigneeTexas Instruments Incorporated
InventorDarrell L. Ash
Life of this patent
Estimating the term…
Abstract
An improved channel selector for a television receiver includes a metal semiconductor field effect transistor, i.e. MESFET mixer in combination with an acoustic surface wave device filter. The MESFET mixer simultaneously receives a plurality of channels and mixing signals of a selectable frequency, and in response thereto frequency shifts selectable channels to a predetermined center frequency. The MESFET mixer has almost perfect square law characteristics, and accordingly introduces extremely small distortion into the system. The acoustic surface wave device filter has an input coupled to the output of the MESFET mixer. The surface wave device filter provides essentially all of the channel selectivity of the receiver.
Claims12
A radio frequency-intermediate frequency section of a frequency channel selector for obtaining a selected channel of frequencies from a plurality of non-overlapping frequency channels, said radio frequency-intermediate frequency section comprising:
- at least one mixing means including a metal semiconductor field effect transistor and having first and second inputs coupled to simultaneously receive radio frequency signals representative of the plurality of frequency channels and mixing signals of a selected intermediate frequency for frequency shifting the selected frequency channel to a predetermined center frequency in the intermediate frequency range;
- and
- acoustic surface wave filter means connected to the output of said mixing means for essentially passing only the channel of said predetermined center frequency.
A radio frequency-intermediate frequency section of a frequency channel selector for obtaining a selected channel of frequencies from a plurality of non-overlapping frequency channels, said radio frequency-intermediate frequency section comprising:
- first and second mixing means, each of said mixing means including a metal semiconductor field effect transistor and having first and second inputs coupled to simultaneously receive radio frequency signals representative of the plurality of frequency channels and mixing signals of a selectable intermediate frequency for frequency shifting the selected frequency channel to a predetermined center frequency in the intermediate frequency range;
- switching means connected to the outputs of said first and second mixing means;
- and
- acoustic surface wave filter means connected to said switching means, said switching means being operable to alternately interconnect the outputs of said first and second mixing means to said acoustic surface wave filter means such that said acoustic surface wave filter means is effective to pass only the channel of said predetermined center frequency from the output of the mixing means to which said acoustic surface wave filter means is interconnected via said switching means.
Dependencies are inferred from the claim text.