Telecommunications – Receiver or analog modulated signal frequency converter – Modulation distortion or cross talk correction or elimination
Reexamination Certificate
1999-05-27
2001-09-18
Nguyen, Lee (Department: 2683)
Telecommunications
Receiver or analog modulated signal frequency converter
Modulation distortion or cross talk correction or elimination
C340S007420, C375S271000, C375S334000
Reexamination Certificate
active
06292655
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to a selective calling radio-receiver, and more particularly to a selective calling radio-receiver receiving and demodulating a selective calling radio-signal, and displaying message included in the received radio-signal.
The invention also relates to a method of receiving a selective calling radio signal in a selective calling radio-receiver, and more particularly to a method of receiving a selective calling radio signal in a selective calling radio-receiver receiving and demodulating a selective calling radio-signal, and displaying message included in the received radio-signal.
2. Description of the Invention
There have been suggested various selective calling radio-receivers which receives a selective calling radio signal and demodulates the received selective calling radio signal for displaying message indicated in the received selective calling radio signal. For instance, Japanese Unexamined Patent Publication No. 8-289345 has suggested such a selective calling radio-receiver.
Such a conventional selective calling radio-receiver as mentioned above generally operates as follows. First, a selective calling radio-receiver receives a selective calling radio signal transmitted from a caller through a base station in a certain signal system such as ERMES, and demodulates the thus received selective calling radio signal. Then, the received selective calling radio signal is shaped in a waveform thereof. Thereafter, data is introduced into the selective calling radio-receiver in accordance with a timing clock transmitted in synchronization with the received data. After a calling number and a message signal have been obtained, a decoder compares the thus decoded calling number to a calling number of the selective calling radio-receiver, stored in a memory. If they are coincident with each other, an annunciator such as a speaker annunciates that a call has been received. A message indicated in the received selective calling radio signal is displayed in a display screen.
As a service area of a base station for a selective calling radio-receiver has been expanded, there has been increased an overlapping area where selective calling radio signals transmitted from a plurality of base stations overlap one another in a common service area. In such an overlapping area, there occurs level fluctuation in a bit signal due to phasing, a difference in delay among transmitting stations, and a difference in a frequency.
A conventional selective calling radio receiver is designed to receive only a point in a center level in a demodulated signal for receiving data included in the demodulated signal. Hence, noises are disadvantageously added to a demodulated signal in a center level thereof, or data error tends to occur due to level fluctuation in the above-mentioned overlapping area, both causing reduction in signal receiving rate.
Japanese Unexamined Patent Publication No. 5-30009 has suggested a radio signal receiver including a timing generator which carried out sampling three or more times for a bit of a demodulated signal having a rectangular waveform, and a controller receiving sampled data, converting the sampled data to actual radio data, and compensating for a sampling timing based on the sampled data.
Japanese Unexamined Patent Publication No. 8-201544 has suggested a selective calling radio-receiver including means for measuring a period of time associated with data “1” and “0”, means for adding time with ½ of the measured period of time being used as an initial value, and means for checking the time.
Japanese Unexamined Patent Publication No. 3-69238 has suggested a selective calling radio-receiver including a detecting and demodulating circuit which demodulates a received signal and outputs a base band signal, a comparator turning the base band signal into a binary signal, and outputting the binary signal, a clock reproducing circuit which reproduces a first clock signal having the same frequency as a bit rate of data to be transmitted, and generates a second clock signal having a higher rate than that of the first clock signal, a multi-timing discriminator which samples the binary signal in accordance with the second clock signal, makes a decision by majority to a plurality of sampling points among the sampled data, and outputs a signal obtained as a result of the decision by majority, and a latch circuit which latches the signal transmitted from the multi-timing discriminator, in accordance with the first clock signal, and outputs the latched signal as reproduced digital data.
Japanese Unexamined Patent Publications Nos. 60-146557, 4-11431 and 4-123550 have suggested selective calling radio-receivers which receive a selective calling radio signal and demodulates the received signal, and displays message included in the received signal, in a display screen.
SUMMARY OF THE INVENTION
In view of the above-mentioned problems in the conventional selective calling radio-receivers, it is an object of the present invention to provide a selective calling radio-receiver which is capable of receiving data without an error in such an overlapping area as mentioned above.
It is also an object of the present invention to provide a method of receiving a selective calling radio signal without an error in such an overlapping area as mentioned above.
In one aspect, there is provided a selective calling radio-receiver including (a) a demodulator demodulating a received selective calling radio signal, (b) a waveform-shaper shaping waveform of a demodulation signal transmitted from the demodulator, (c) a data-receiving signal generator generating a data-receiving signal which is in synchronization with the modulation signal having a waveform having been shaped by the waveform-shaper, and which has a plurality of pulses per a symbol term, (d) a data-receiver receiving the demodulation signal at every pulse of the data-receiving signal, (e) a sign discriminator discriminating a sign of received data at every symbol, based on data having been received in the data-receiver, and (f) a processor processing the received data a sign of which has been discriminated by the sign discriminator.
It is preferable that the sign discriminator determines a sign in the greatest number among signs of data having been received from the data-receiver in a symbol term, as a sign of data having been received in the symbol term.
For instance, the data-receiving signal generator may be designed to include (c1) a synchronization clock generator generating a synchronization signal having a rectangular waveform produced in every symbol period, based on the demodulation signal having a waveform having been shaped by the waveform-shaper, and (c2) a timing signal generator generating a pulse row as the data-receiving signal in a certain period of time around a time associated with a level-turning point of the synchronization signal in a symbol term, the pulse row including a plurality of pulses.
For instance, the timing signal generator may be designed to include (c21) a memory storing therein at least one of information about a timing at which data is received and information about the number of data, (c22) a first controller varying the timing stored in the memory, and (c23) a timing generator generating the data-receiving signal having a pulse width and a pulse period both determined in accordance with the information.
For instance, the timing signal generator may be designed to include (c21) a memory storing therein at least one of information about a timing at which data is received and information about the number of data, (c22) a second controller varying the number of data stored in the memory, and (c23) a timing generator generating the data-receiving signal having a pulse by the number determined in accordance with the information.
When the selective calling radio signal is a binary FSK signal, the waveform-shaper may be designed to include (b1) a reference voltage source generating a reference voltage, and (b2) a comparator comparing the demod
McGuireWoods LLP
NEC Corporation
Nguyen Lee
LandOfFree
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