Telecommunications – Receiver or analog modulated signal frequency converter – Local control of receiver operation
Reexamination Certificate
2000-03-01
2002-12-31
Hunter, Daniel (Department: 2684)
Telecommunications
Receiver or analog modulated signal frequency converter
Local control of receiver operation
C455S307000
Reexamination Certificate
active
06501944
ABSTRACT:
TECHNICAL FIELD
The invention relates to a method for the control of the bandpass width in the filtering of an intermediate frequency signal of an audio receiver of a radio reception apparatus in which a signal parameter of a user signal of the audio receiver which is received at a reception frequency is determined and taken into account. The invention also relates to a corresponding radio reception apparatus with an audio receiver for the reception of a user signal at a reception frequency, an intermediate frequency filter unit for the filtering of an intermediate frequency signal corresponding to the user signal and a filter selection unit for the selection of a bandpass width for the intermediate frequency filter unit of the audio receiver.
BACKGROUND OF THE INVENTION
In radio reception apparatuses of this kind the user signal, i.e. the wanted signal, is received in an input circuit of the audio receiver by means of an antenna, pre-amplified and converted to an intermediate frequency signal in a heterodyning circuit so that the user signal is for example present as a frequency modulation of an intermediate frequency of 10.7 MHz. The intermediate frequency signal is amplified and bandpass filtered in the intermediate frequency filter unit with a specific bandpass width.
Known radio reception apparatuses have, for the selection of the bandpass width of the intermediate frequency filtering, a filter selector unit in which a suitable signal parameter of the user signal is determined and in which in dependence on this a corresponding bandpass width is set in the intermediate frequency filter unit. If for example a lower reception quality is detected, a narrower bandpass width is selected in order to filter the frequency-wise adjacent disturbance signals out of the user signal.
This filtering with a narrower bandpass width indeed reduces the influence of disturbance signals of this kind and thus improves the selectivity; it however also leads to a worsening of other parameters, such as for example the stereo channel separation. Therefore the filter selection unit causes the use of a greater bandpass width as soon as a higher reception quality is detected. Since the improvement of the reception quality however can be effected by the previously caused use of a narrower bandpass width, this control mechanism can lead to an audible and thus disadvantageous continual change among the various filters available.
SUMMARY OF THE INVENTION
An object of the invention is to provide a method for the control of the bandpass width in the intermediate frequency filtering in which a continual change among various bandpass widths is avoided.
This object is satisfied for a method of the initially named kind in that a signal parameter of at least one neighboring signal which is received at a neighboring frequency adjacent to the reception frequency is determined; and in that the bandpass width of the intermediate frequency filtering is selected in dependence at least on the signal parameter which is determined from the user signal, on the signal parameter which is determined from the neighboring signal and on the frequency distance between the reception frequency and the neighboring frequency.
It is thus provided in accordance with the invention to determine and take into account for the calculation and setting of the bandpass width not only a signal parameter which is associated with the audio user signal, but also at least one signal parameter which is associated with a disturbing neighboring signal on a different neighboring frequency which is adjacent to the reception frequency of the user signal.
In the context of this invention a signal parameter of the user signal is to be understood to be a parameter which can be determined from the user signal and which at least indirectly enables a statement on the quality of the signal reception in the audio receiver or on the presence of undesirable disturbing influences. For example the signal level or the signal strength of the user signal, in particular in the form of the electric field strength, or the deviation of the user signal, come under consideration as a signal parameter of this kind. A further possible signal parameter of the user signal can be given by an output signal of an associated reception quality detector, in particular by a so-called ultrasonic-noise (USN) signal, which provides information on the presence of neighboring signals.
In the method in accordance with the invention an unintentional continual change among different filters or filter bandwidths respectively can be more easily avoided, since with the relevant signal parameter of the neighboring signal a selection criterion can in principle be used which is not influenced by a change in the bandpass width for the user signal. As a result of this additional selection criterion, a criterion can also be used as the signal parameter of the user signal which, in comparison with the reception quality, which is taken into account in known methods, is not or is merely insignificantly influenced by a change of the bandpass width of the intermediate frequency filtering.
A signal parameter of the neighboring signal is to be understood in the sense of this invention to mean a parameter which can yield a statement on the strength of the associated neighboring signal and accordingly on the suitability of the neighboring signal for the disturbing influencing of the user signal. For example the signal strength, in particular the electrical signal strength, or the deviation of the neighboring signal can be used as such a parameter of the disturbing signal.
In this manner a direct feedback between the selected bandpass width on the one hand and the determined signal parameters on the other hand is avoided to a great extent, and the known regulation mechanism is replaced by a stable control.
The determination of the respective signal parameter of the user signal and of the neighboring signal can take place particularly effectively when the relevant signal is already transformed to an intermediate frequency signal and as such has been amplified and filtered as well as in particular demodulated again.
In order to select a corresponding bandpass width of the intermediate frequency filtering on the basis of the explained signal parameters of the user signal and the neighboring signal, these signal parameters can be compared relative to one another. It is in particular possible to compute the respective characteristic values with one another, for example to subtract them, to add them and/or to divide them, and in this to provide them with different weighting factors.
Preferably, the bandpass width is in principle selected all the narrower, the higher the ratio of the signal strength of the neighboring signal to the signal strength of the user signal and/or the lower the distance between the reception frequency and the neighboring frequency is.
Furthermore, it is preferred when the neighboring signal is determined by means of a separate additional receiver, the reception frequency of which, i.e. the neighboring frequency, can be set independently of the reception frequency which is set in the audio receiver. In this way the additional receiver can continually monitor different neighboring frequencies so that the current setting of the bandpass width of the intermediate frequency filtering can be continually monitored and corrected when appropriate, without it being necessary for the audio receiver to interrupt its reception at the reception frequency for this.
If the signal parameter of the neighboring signal can be determined in a correspondingly short time, it is however in principle also possible to receive the neighboring signals which are required for the selection of the bandpass width by means of the audio receiver, in that the latter continually changes, for short times and thus not perceivably by the listener, from the reception frequency to the relevant neighboring frequency and back.
If the neighboring signal is determined by means of an additional receiver, it is preferred when the latter
Shatara Raed S.
Szydlowski Zbigniew
Delphi Technologies Inc.
Funke Jimmy L.
Tran Tuan
LandOfFree
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