Telecommunications – Receiver or analog modulated signal frequency converter – Signal selection based on frequency
Patent
1995-02-27
1998-04-14
Eisenzopf, Reinhard J.
Telecommunications
Receiver or analog modulated signal frequency converter
Signal selection based on frequency
455134, 4551612, 455205, 4552262, 455296, 455303, 381 10, H04B 118
Patent
active
057405239
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The present invention relates to a radio receiver equipped with an FM and/or AM receiving function. More particularly, the present invention relates to a radio receiver equipped with functions such as a high frequency cutoff function, a stereo separation adjustment function, an automatic receiving frequency seek function, an automatic mono/stereo selector function, or an automatic wide
arrow selector function for selecting a band with.
BACKGROUND OF THE INVENTION
When operating an FM receiver, the problem exists of the characteristic FM noise, when the signal is weak and the antenna input level is low. The drop in the S/N ratio consequent on a weak signal is much greater for a stereo signal than for a monaural signal, and it is known for the stereo drop to be 20 dB or more compared with the monaural drop.
A conventional response to this problem is to vary the stereo separation when the signal is weak, to increase the S/N ratio. For example, as shown in FIG. 4, based on a composite signal from an FM detector IC 12, an FM multiplexer IC 14, which regenerates left and right signals, demodulates the subsidiary signal in this composite signal. At this point, by varying the demodulation level of this subsidiary signal it is possible to control the stereo separation for a weak signal.
On the other hand, for monaural broadcasts, the drop in the S/N ratio for a weak signal can be countered by implementing a high frequency cutoff function, reducing the level of high frequencies, and improving the subjective S/N ratio. The FM multiplexer IC 14 of FIG. 4 has a built-in high frequency cutoff function. The high frequency cutoff function and elements relating to it are also hereafter referred to by the abbreviation HCC (for "High Cut Control"), and the stereo separation control function similarly by the abbreviation SPC ("Separation Control").
The FM multiplexer IC 14 has an HCC pin 30a and an SPC pin 34a. The signal meter output voltage from the FM detector IC 12, representing the strength of the signal, is divided by resistors R1 and R2, and the result tog HCC and SPC voltages are applied to the pins 30a and 34a respectively.
In a conventional system as described above, the high frequency cutoff and stereo separation control functions are adjusted by means of the variable resistor R2 connected to the pins 30a and 34a. Not only, however, does this require troublesome manual operations, but it is also often extremely difficult to make adjustments for the desired characteristics. This is because of the inevitable variations in the many components of an FM receiver, which cause the signal meter output to vary from unit to unit. Because of the variability of the output from the signal meter, in many cases the whole unit has to be rejected because the adjustment is not possible within the adjustment range of the variable resistor R2, and this causes production problems.
Moreover, in a two-tuner diversity receiving system, in which two tuners are used, and the tuner with the higher antenna input level is selected, the following erroneous operation occurs. Namely, if the signal meter output voltages from the two tuners are different when the same antenna levels are input, although the tuner with the higher signal meter output voltage is selected, in fact this results in selecting the tuner with the lower antenna input level. Therefore, it is in fact necessary for the two tuner components when using this method to be selected to have substantially the same characteristics.
Moreover, there are also variability problems when using a seek function, which automatically scans through the broadcast frequencies and selects a station with a high receiving sensitivity. The condition for the seek is that the output from a station detector (SD) goes high. At the manufacturing stage, an operation is needed, for example using a trimmer or a variable resistor, to adjust the point at which this station detector output goes high. For example, in the manufacturing adjustment stage, a trimmer or a variable resistor ma
REFERENCES:
patent: 4087750 (1978-05-01), Allen et al.
patent: 4356567 (1982-10-01), Eguchi et al.
patent: 4903328 (1990-02-01), Ichikawa
patent: 4926498 (1990-05-01), Suzuki et al.
patent: 5201062 (1993-04-01), Nakamura et al.
patent: 5390344 (1995-02-01), Nagata
patent: 5526530 (1996-06-01), Sueoka et al.
patent: 5564093 (1996-10-01), Matsumoto
Nakajima Yukihiro
Tsukuda Masami
Eisenzopf Reinhard J.
Shintom Co., Ltd.
To Doris
LandOfFree
Radio receiver does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Radio receiver, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Radio receiver will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-648989