 Headset control system for operating a microcontroller based device |
| OF THE INVENTION In application Ser. No. 08/920,406 filed Aug. 29, 1997, now U.S. Pat. No. 5,978,68... |
|
| Radiotelephone with handset talking function and hand-free talking function |
| A first object of the present invention is to provide an easier-to-use radiotelephone capable of ... |
|
| Noise suppression of acoustic signal in telephone set |
| An object of the present invention is to provide a small-size telephone set capable of obtaining ... |
|
| Selective pager receiver |
| It is an object of the present invention to provide a selective pager receiver which presents ... |
|
| Instrument panel unit of vehicle having radio signal receiver |
| In view of the foregoing situation, it is an object of the present invention to provide an ... |
|
| Method for detecting fraudulent use of a communications system |
| OF THE PREFERRED EMBODIMENT In accordance with the present invention, FIG. 1 illustrates a first ... |
|
|
Mobile communication terminal for rapid adjustment of a reference frequency to a target frequency
| Details |
Inventors: Ichihara, Masaki;
Assignee: NEC Corporation (Tokyo, JP)
Primary Examiner: Urban; Edward F.
Assistant Examiner:
Attorney, Agent or Firm: Foley & Lardner
In a mobile communication terminal, a switch 10 is initially set to an initial setting mode at time of turning on a power supply. A reference oscillator control circuit is initialized, and in this state, the output frequency of a reference oscillator is usually greatly shifted. The base station search is first conducted, and as a result, if the base station cannot be grasped, an offset signal is generated by a frequency offset generating circuit 12, to shift the output frequency of a reference oscillator 6 through a reference oscillator control circuit 5. This operation is repeated until the base station is grasped so that the base station search is continued while the output frequency of the reference oscillator 6 is being shifted. When a grasp of the base station succeeds, the switch 10 is switched to an AFC side to conduct automatic frequency adjustment. |
|
DETAILED DESCRIPTION The present invention has been made to solve the above problems with the conventional system, and therefore an object of the present invention is to provide a technique by which an error in frequency is well squeezed from an initial state where a power supply is switched on, and a base station is grasped.
In order to achieve the above object, according to the present invention, there is provided a mobile communication terminal, which comprises: a receive circuit for receiving an electric wave which is transmitted from a base station; local signal generating means for outputting a local signal to the receive circuit; a reference oscillator for transmitting a reference signal indicative of a reference of an oscillation frequency of the local signal generating means; reference oscillator control means for generating a control signal that controls the transmit frequency of the reference oscillator; demodulating means for demodulating a signal received by the receive circuit; base station search means that inputs a demodulated signal outputted from the demodulating means for searching an identifying signal indicative of the base station which is included in the demodulated signal to detect the presence/absence of the base station; and frequency offset generating means that changes the control signal generated by the reference oscillator control means according to a search result of the base station search means for offsetting the transmit frequency of the reference signal oscillator.
Also, in the case where the identifying signal indicative of the base station can be correctly detected by the base station search means, the base station search means stops the frequency offset generating means from offsetting the transmit frequency of the reference signal oscillator.
The mobile communication terminal further includes frequency error detecting means that inputs the demodulated signal outputted from the demodulating means for detecting an error in the frequency of the reference oscillator, wherein after a function of offsetting the output frequency of the reference signal oscillator by the frequency offset generating means is stopped, the control signal generated by the reference oscillator control means is produced according to a frequency error signal outputted by the frequency error detecting means to control the transmit frequency of the reference signal oscillator
|
|
Ring Tones 
