FM/AM broadcast signal converter
First Claim
1. Apparatus for converting an FM broadcast signal to an intermediate frequency signal from which modulating information may be recovered, comprising:
- receiving means for receiving the FM broadcast signal;
first and second mixing means for mixing the received FM broadcast signal with first and second local oscillating signals, respectively;
local oscillation means for generating said first and second local oscillating signals exhibiting a predetermined phase shift relative to each other and for supplying said first and second local oscillating signals to said first and second mixing means, respectively, said local oscillating signals being of a frequency such that said mixing means produce output signals in an intermediate frequency range of approximately two orders of magnitude less than the intermediate frequency normally produced from said received FM broadcast signal;
phase shift means coupled to said first and second mixing means for imparting predetermined phase shifts to said output signals produced by said mixing means such that image signal components present in respective ones of said produced output signals are phase shifted to be out-of-phase with each other;
combining means coupled to said phase shift means for combining said phase shifted output signals, whereby the out-of-phase image signal components are substantially cancelled; and
filter means coupled to said combining means and tuned to the intermediate frequency which is approximately two orders of magnitude less than the normal intermediate frequency for passing said output signals produced by said mixing means having frequencies within a predetermined range of said intermediate frequency which is approximately two orders of magnitude less than the normal intermediate frequency.
1 Assignment
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Accused Products
Abstract
A received modulated information signal is converted to an intermediate frequency (IF) signal from which modulating information may be recovered by supplying the modulated information signal to two mixers supplied with local oscillating signals of equal frequency but phase shifted with respect to each other. Output signals produced by the mixers are supplied through phase shift circuits which impart predetermined phase shifts thereto such that image signal components present in respective ones of the mixer output signals are phase shifted to be out-of-phase with each other. The phase shifted mixer output signals are combined, whereby the out-of-phase image signal components are substantially cancelled. A filter tuned to the IF frequency is coupled to the output of the combining circuit to pass the mixer output signals having frequencies within a predetermined range of the IF frequency.
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Citations
25 Claims
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1. Apparatus for converting an FM broadcast signal to an intermediate frequency signal from which modulating information may be recovered, comprising:
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receiving means for receiving the FM broadcast signal; first and second mixing means for mixing the received FM broadcast signal with first and second local oscillating signals, respectively; local oscillation means for generating said first and second local oscillating signals exhibiting a predetermined phase shift relative to each other and for supplying said first and second local oscillating signals to said first and second mixing means, respectively, said local oscillating signals being of a frequency such that said mixing means produce output signals in an intermediate frequency range of approximately two orders of magnitude less than the intermediate frequency normally produced from said received FM broadcast signal; phase shift means coupled to said first and second mixing means for imparting predetermined phase shifts to said output signals produced by said mixing means such that image signal components present in respective ones of said produced output signals are phase shifted to be out-of-phase with each other; combining means coupled to said phase shift means for combining said phase shifted output signals, whereby the out-of-phase image signal components are substantially cancelled; and filter means coupled to said combining means and tuned to the intermediate frequency which is approximately two orders of magnitude less than the normal intermediate frequency for passing said output signals produced by said mixing means having frequencies within a predetermined range of said intermediate frequency which is approximately two orders of magnitude less than the normal intermediate frequency. - View Dependent Claims (2, 3)
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4. Apparatus for converting either an FM or an AM broadcast signal to an intermediate frequency signal from which modulating information may be recovered, comprising:
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receiving means for receiving the FM or AM signal from which a respective predetermined intermediate frequency is normally produced; first and second mixing means for mixing the received FM or AM signal with FM or AM local oscillating signals, respectively; local oscillating means for generating first and second FM local oscillating signals exhibiting a predetermined phase shift relative to each other in which the frequency of said FM local oscillating signals is such that said first and second mixing means produce output FM intermediate frequency signals with frequencies approximately two orders of magnitude less than the FM intermediate frequency normally produced, and for generating first and second AM local oscillating signals exhibiting said predetermined phase shift relative to each other in which the frequency of said AM local oscillating signals is such that said first and second mixing means produce output AM intermediate frequency signals with frequencies approximately one order of magnitude less than the AM intermediate frequency normally produced; selector means for selecting said first and second phase shifted FM local oscillating signals or said first and second phase shifted AM local oscillating signals to be supplied to said first and second mixing means; phase shift means coupled to said first and second mixing means for imparting predetermined phase shifts to the output signals produced by said mixing means such that image signal components present in respective ones of said produced output signals are phase shifted to be out-of-phase with each other; combining means coupled to said phase shift means for combining the phase shifted output signals, whereby the out-of-phase image signal components are substantially canceled; and FM and AM filter means coupled to said combining means and tuned to the FM intermediate frequency which is approximately two orders of magnitude less than said FM intermediate frequency normally produced and the AM intermediate frequency which is approximately one order of magnitude less than said AM intermediate frequency normally produced, respectively, for passing said output signals produced by said mixing means having frequencies within a predetermined range of the FM intermediate frequency which is approximately two orders of magnitude less than said FM intermediate frequency normally produced or the AM intermediate frequency which is approximately one order of magnitude less than said AM intermediate frequency normally produced. - View Dependent Claims (5, 6, 7, 8, 9, 10, 11, 12)
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13. Apparatus for converting a broadcast AM signal to an intermediate frequency signal from which modulating information may be recovered, comprising:
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receiving means for receiving the AM broadcast signal; first and second mixing means or mixing the received AM broadcast signal with first and second local oscillating signals, respectively; local oscillation means for generating said first and second local oscillating signals exhibiting a predetermined phase shift relative to each other and for supplying said first and second local oscillating signals to said first and second mixing means, respectively, said local oscillating signals being of a frequency such that said mixing means produce output signals in an intermediate frequency range of approximately one order of magnitude less than 455 kHz which is the intermediate frequency normally produced from said received AM broadcast signal; phase shift means coupled to said first and second mixing means for imparting predetermined phase shifts to said output signals produced by said mixing means such that image signal components present in respective ones of said produced output signals are phase shifted to be out-of-phase with each other; combining means coupled to said phase shift means for combining said phase shifted output signals, whereby the out-of-phase image signal components are substantially canceled; and filter means coupled to said combining means and tuned to the intermediate frequency which is approximately one order of magnitude less than 455 kHz for passing said output signals produced by said mixing means having frequencies within a predetermined range of said intermediate frequency which is approximately one order of magnitude less than 455 kHz. - View Dependent Claims (14, 15, 16, 17, 18, 19, 20, 21, 22)
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23. Apparatus for converting either an FM or an AM broadcast signal to an intermediate frequency signal from which modulating information may be recovered, comprising:
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receiving means for receiving the FM or AM signal; first and second mixing means for mixing the received FM or AM signal with FM or AM local oscillating signals, respectively; local oscillating means for generating first and second FM local oscillating signals exhibiting a predetermined phase shift relative to each other in which the frequency of said FM local oscillating signals is such that said first and second mixing means produce output FM intermediate frequency signals with frequencies approximately two orders of magnitude less than 10.5 MHz which is the FM intermediate frequency normally produced, and for generating first and second AM local oscillating signals exhibiting said predetermined phase shift relative to each other in which the frequency of said AM local oscillating signals is such that said first and second mixing means produce output AM intermediate frequency signals with frequencies approximately one order of magnitude less than 455 kHz which is the AM intermediate frequency normally produced; selector means for selecting said first and second phase shifted FM local oscillating signals or said first and second phase shifted AM local oscillating signals to be supplied to said first and second mixing means; phase shift means coupled to said first and second mixing means for imparting predetermined phase shifts to the output signals produced by said mixing means such that image signal components present in respective ones of said produced output signals are phase shifted to be out-of-phase with each other; combining means coupled to said phase shift means for combining the phase shifted output signals, whereby the out-of-phase image signal components are substantially canceled; and FM and AM filter means coupled to said combining means and tuned to the FM intermediate frequency which is approximately two orders of magnitude less than 10.5 MHz and the AM intermediate frequency which is approximately one order of magnitude less than 455 kHz, respectively, for passing said output signals produced by said mixing means having frequencies within a predetermined range of the FM intermediate frequency which is approximately two orders of magnitude less than 10.5 MHz or the AM intermediate frequency which is approximately one order of magnitude less than 455 kHz. - View Dependent Claims (24, 25)
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Specification