US 5,369,470 AGranted

FM receiver which detects and responds to receiving and interference states

AssigneeH.U.C. Elektronik GmbH

InventorJens Hansen

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Abstract

An FM receiver includes an IF unit followed by an LF unit, the IF unit having an IF filter arrangement. The center frequency of the IF filter arrangement, which is relatively narrow-banded with respect to the channel bandwidth, is controlled in dependence on the receiving conditions. The receiver has circuitry for changing the signal transmission characteristic of the IF and/or LF units, including a detector module with detector circuits for detecting values characteristic of receiving or interference states, with the inputs of said circuits each being connected with a circuit point of the IF or LF unit carrying the signal to be processed, and with the outputs of these circuits providing signals characterizing receiving and interference states. The circuitry for changing the signal transmission characteristic also includes an evaluation circuit for processing the signals characteristic of receiving or interference states, the evaluation circuit having an input portion with at least one amplitude and/or time threshold circuit connected with the detector module and having a logic unit which is connected to the input portion and which provides processed signals characteristic of receiving and interference states as control signals to influence the individual stages of the IF or LF unit.

Claims29

Dependent claims

An improved FM receiver which includes an IF unit having a plurality of stages of an LF unit having a plurality of stages, the IF unit including a relatively narrowbanded IF filter having a controllable center frequency and the LF unit providing at least one audio frequency output signal, wherein the improvement comprises:

at least one stage of the IF unit has a control input port and at least one stage of the LF unit ha a control input port;
and
the FM receiver additionally includes a transmission characteristic change means for changing a signal transmission characteristic of at least one of the IF and LF units, said transmission characteristic change means comprising
a signal detector module (28) including detector circuits (29 to 33) for detecting values characteristic of receiving or interference states, with said detector circuits having inputs which are each connected with a stage of the IF or LF unit, and with said signal detector module having outputs for signals characteristic of receiving or interference states, respectively;
and
evaluation means (400, 600) for generating processed signals characteristic of receiving or interference states, respectively, as control signals to influence the signal transmission characteristic of at least one of the IF and LF units, with inputs of the evaluation means being connected with outputs of the signal detector module and the outputs of the evaluation means being connected with control input ports of stages of the IF and LF units,
wherein the evaluation means includes timer means (700) for increasing the duration of at least one of the signals which is output by the detector module during an interference state until reception has improved for a predetermined minimum time-span.

4 more elements

An FM receiver having an input port for an IF signal, comprising:

a demodulator having an input port and an output port;
IF transmission path means for defining a transmission path for he IF signal from the input port of the receiver to the input port of the demodulator, the IF transmission path means including a filter through which the IF signal flows, the filter having filter characteristics;
a low frequency portion having an input port that is connected to the output port of the demodulator, the low frequency portion carrying a demodulated signal;
and
filter control means for controlling the filter characteristics in accordance with receiving conditions, the filter control means being responsive to the demodulated signal and to the IF signal carried by the transmission path, the filter control means including timer means for determining when receiving conditions have remained in an improved state for at least a predetermined minimum time-span in order to suppress frequent changes in the filter characteristics during rapidly changing receiving conditions, the timer means including means for generating first and second pulse trains with the same frequency but different phases.

2 more elements

Dependencies are inferred from the claim text.