Appeal No. 1999-0859
Application No. 08/330,972
to a desired frequency band selected from a first frequency band
and a second frequency band. The received radio frequency
signal is phase shifted and mixed with signals from a divided
local oscillator, the frequency of the local oscillator being
selected to be in the middle of the two selected frequency
bands. The intermediate frequency signal produced as the output
of the mixing operation is phase shifted and filtered through
first and second bandpass filters having differing widths. The
desired intermediate frequency is selected from the outputs of
either the first or second bandpass filters through operation of
a switch. Appellant asserts at pages 3 and 4 of the
specification that the claimed circuit arrangement achieves the
desired result using a single selector switch, thereby avoiding
the problems associated with prior art multi-switch
arrangements.
Claim 1 is illustrative of the invention and reads as
follows:
1. A circuit arrangement for switching the frequency range of
a radio receiver, utilizing image frequency bands, to a
desired frequency band selected from between a first
frequency band having channels with a first bandwidth and a
second frequency band having channels with a second
bandwidth, whereby the frequency of a local oscillator is
adapted approximately to the middle of the two selected
2
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