Switching system for diversity antenna FM receiver
First Claim
1. An FM receiver having a plurality of antennas, an FM signal detector generating a strength signal indicating a level of radiowave voltage, and a noise detector generating a noise signal indicating the level of noise, and a switching circuit including a logic control for selecting one of said plurality of antennas in response to the strength signal or the noise signal reaching a threshold level;
- wherein said logic control further comprises an adapter for revising said threshold level, said adapter comprising at least one of a first interrupt generator and a second interrupt generator, said first interrupt generator being responsive to a significant short duration drop in signal level, and said second interrupt generator being responsive to a significant short duration increase in noise.
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Abstract
An FM radiowave receiver includes a diversity antenna system responsive to signal strength and noise levels. The signal strength and noise detectors generate representative signals that are compared with a threshold value for determining the input to a control for the antenna switch alternately connecting two or more antennas to the front end of the FM receiver. The present invention provides an adaptive threshold for each of the signal strength and noise signals so that the switching is limited to significant changes in signal strength and noise levels. In the preferred embodiment, the noise level threshold is adapted as a function of the modulation level of the audio composite signal delivered from the FM detector to the FM stereo decoder of the receiver.
63 Citations
14 Claims
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1. An FM receiver having a plurality of antennas, an FM signal detector generating a strength signal indicating a level of radiowave voltage, and a noise detector generating a noise signal indicating the level of noise, and a switching circuit including a logic control for selecting one of said plurality of antennas in response to the strength signal or the noise signal reaching a threshold level;
wherein said logic control further comprises an adapter for revising said threshold level, said adapter comprising at least one of a first interrupt generator and a second interrupt generator, said first interrupt generator being responsive to a significant short duration drop in signal level, and said second interrupt generator being responsive to a significant short duration increase in noise. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12)
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13. An FM receiver having first and second antennas, an FM signal detector generating a strength signal indicating a level of radiowave voltage, a noise detector generating a distortion signal indicating the level of high frequency signal, and a switching circuit for selecting one of said first and second antennas in response to a strength signal or said distortion level reaching a threshold level;
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wherein said receiver further comprises a logic control including an adapter for revising said threshold level, said adapter comprising at least one of a first interrupt generator and a second interrupt generator, said first interrupt generator being responsive to a predetermined ratio level of instant signal level to average signal level, and said second interrupt generator being responsive to a predetermined ratio of an instant distortion level to average distortion level; wherein said logic circuit includes an interrupt selector selecting at least one of said first interrupt generator and said second interrupt generator upon detection of a first threshold level and responding to both said first and second interrupt generators in response to a second threshold level.
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14. A method for controlling an FM receiver with a decision logic controller and having first and second antennas, an FM signal detector generating a strength signal indicating a level of radiowave voltage, a distortion detector generating a signal indicating the level of high frequency signal, and a switching circuit including a logic control for selecting one of said first and second antennas in response to a strength signal or said distortion level reaching a threshold level;
- the method comprising
adapting said threshold level with at least one interrupt generator by using a first interrupt generator determining compliance with a predetermined ratio level of instant signal level to average signal level, or determining compliance with a second predetermined ratio of an instant distortion level to average distortion level; actuating said switching means upon compliance; and ignoring interrupts for a predetermined time after compliance.
- the method comprising
Specification