Circuit arrangement for derivation of a signal dependent on the

Details Circuit arrangement for derivation of a signal dependent on the Circuit arrangement for derivation of a signal dependent on the

1995-03-06

1996-12-10

Eisenzopf, Reinhard J.

Telecommunications

Receiver or analog modulated signal frequency converter

Signal selection based on frequency

4551851, H04B 118

Patent

active

055840604

DESCRIPTION:

BRIEF SUMMARY
FIELD OF THE INVENTION

The present invention concerns a circuit arrangement for deriving a signal dependent on the change direction of the incoming signal level in a radio receiver controllable by a microcomputer.


BACKGROUND INFORMATION

Radio receivers are increasingly being controlled by microcomputers, with evaluation of a signal representing the signal level also being performed. Such a signal is derived, for example, by amplitude demodulation followed by low-pass filtration of the FM intermediate frequency signal. Following further processing by the microcomputer, a signal strength signal of this kind is used to reduce stereo channel separation or volume when noise occurs and to select one of several transmitters broadcasting the same program. Processing the signal strength signal in the microcomputer, especially determining the change direction, entails computing cost.
The goal of the present invention is to derive a signal as a function of the change direction of the incoming signal level, using minimum computing power.


SUMMARY OF THE INVENTION

This goal is achieved according to the present invention by providing a comparator outside the microcomputer to which a signal representing the respective signal strength and a signal generated by the microcomputer and representing the signal strength at an earlier point in time are supplied, and by an output signal from the comparator being supplied to the microcomputer.
Reducing the computer power required for direction determination of the change in signal strength makes it possible to use the freed capacity of the microcomputer to a greater extent for other functions.
One improvement on the circuit arrangement according to the present invention consists of the signal representing the signal strength at an earlier point in time and the comparator output signal being transmitted through a serial peripheral interface (SPI) between the comparator and the microcomputer. Such an interface is especially advantageous in radio receivers with a high degree of integration, for communication of the microcomputer with the radio receiver.
The advantage of the circuit arrangement according to the present invention, namely the saving in computing power, becomes particularly clear in one advantageous embodiment of the present invention in which the signals representing the signal strength are delivered with a resolution of 16 binary digits. This saves a computer operation of two 16-bit words, which in any event serves only to obtain a 1-bit information signal.
One especially advantageous use of the circuit arrangement according to the present invention consists of testing the signal strengths of alternative transmitters to which the radio receiver is switched for sampling.
During sampling reception of alternative frequencies, only an extremely short time of less than 100 ms for example, is available in order to prevent this sampling reception from causing any audible noise if possible. This time contains various time segments that are not useable for testing, for example the duration of transients in tuner 4, so that only a very short time is required to determine whether the alternative transmitter is being received at a higher signal strength. The circuit arrangement according to the present invention is therefore capable of very rapidly generating a signal corresponding to the direction change.


BRIEF DESCRIPTION OF THE DRAWING

The Figure shows one embodiment of a circuit arrangement according to the present invention.


DETAILED DESCRIPTION OF THE INVENTION

The figures drawing shows essential parts of a radio receiver 1, especially those parts required to explain the function of the circuit arrangement according to the present invention within the radio receiver. In addition, the drawing shows a microcomputer 2 that controls radio receiver 1. Individual circuit blocks within radio receiver 1. constitute functional groups known of themselves. However, it is not necessary within the framework of the present invention to make these functional groups discrete mod

REFERENCES:
patent: 4633519 (1986-12-01), Gotoh et al.
patent: 4868885 (1989-09-01), Perry
patent: 5390357 (1995-02-01), Nobusawa et al.

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