Differential demodulators using surface elastic wave devices
Programable frequency acoustic wave discriminator Patent #: 4115744
ApplicationNo. 05/954124 filed on 10/24/1978
US Classes:333/193, Using surface acoustic waves333/150, Delay lines including elastic surface wave propagation means333/196, With response weighting means455/180.2UHF and VHF
ExaminersPrimary: Nussbaum, Marvin L.
Attorney, Agent or Firm
International ClassesH03H 9/00 (20060101)
H03H 9/145 (20060101)
H03H 9/64 (20060101)
H03J 5/24 (20060101)
H03H 9/72 (20060101)
H03J 5/00 (20060101)
Foreign Application Priority Data1977-10-28 JP
AbstractA surface-acoustic-wave filter for a channel selection tuning system of a television receiver includes at least two comb filter elements, each of which comprises an input transducer provided on a piezoelectric substrate and adapted to convert an input electrical signal into an elastic surface wave, and first and second output transducers disposed on the substrate for receiving the elastic surface wave propagating in the same direction from the input transducer. The first and second output transducers are positioned from the input transducer with different distances. The transducers of the two comb filter elements are so designed that the respective comb filter elements respond to frequencies of different program channel bands over for example VHF and UHF bands. The distances of the first and the second output transducers from the input transducer in the wave propagating direction are so predetermined that reciprocal of the difference in delay time between the electrical signals derived from the first and second output transducers is equal to a divisor of an interchannel frequency difference in the corresponding channel band.