Telecommunications – Transmitter – Power control – power supply – or bias voltage supply
Reexamination Certificate
1999-08-02
2002-06-18
Bost, Dwayne (Department: 2681)
Telecommunications
Transmitter
Power control, power supply, or bias voltage supply
C455S194200, C455S194100
Reexamination Certificate
active
06408166
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates generally to communication systems, and in particular, to a method for controlling the gain of a transmission signal in a communication system.
2. Description of the Related Art
A communication system, such as a cordless telephone has a microphone for receiving a voice input (hereinafter “transmission signal”) from a communicating or sending party. The microphone outputs the transmission signal to a receiving party. On the sending side of the communication link, the transmission signal is unmuted during a conversation (or call) state and the transmission signal is muted during an idle state. As a result, the transmission signal is sent to a receiving party only during a conversation or call state.
The transmission signal is switched from a mute state to an unmute state at the moment the communication system switches from the idle state to the call state. Likewise, the transmission signal switches from the unmute state to the mute state at the moment the communication system is switched from the call state to the idle state. As such, the transmission signal is abruptly changed, as it undergoes a state change (i.e., switch from the mute state to the unmute state and from unmute to mute). The abrupt change of state causes undesirable noise spikes in the transmission signal which deteriorate the speech quality. The noise spikes are generated primarily at an input stage of the microphone, composed of an operational amplifier.
FIG. 1
illustrates changes in a gain of the transmission signal in a conventional cordless telephone and
FIG. 2
shows the corresponding operational state of the transmission signal. As illustrated in
FIG. 1
, the cordless telephone changes operational states in the following sequence: idle state→call state→idle state. In the idle state, the cordless telephone minimizes the gain of the transmission signal so as to mute the transmission signal. While in the idle state, when a call is initiated, the gain of the transmission signal abruptly increases so as to unmute the transmission signal. Further, when the cordless telephone re-enters the idle state after completion of the call, the gain of the transmission signal is abruptly decreased minimizing gain so as to mute the transmission signal. As described above, the gain of the transmission signal is abruptly switched when the call is both initiated and terminated. As previously stated, the abrupt switching of the transmission signal gain introduces noise spikes in the transmitter, as shown in FIG.
2
. The noise spike cause a deterioration in speech quality, thereby reducing the reliability of the communication system. As such, there exists a need for a method of controlling the gain of a transmission signal to prevent noise spikes when a call is both initiated and terminated.
SUMMARY OF THE INVENTION
It is therefore an object of the present invention to provide a method for controlling a gain of a transmission signal to prevent noise spikes from being generated when a call is initiated and terminated.
According to the present invention, there is provided a method for gradually increasing the gain of an amplifier for amplifying a transmission signal (i.e., microphone output) to reach an unmute state, when a call is initiated comprising the steps of: determining when a call is initiated; increasing the gain of an amplifier in discrete steps to reach an unmute state; determining when the call is terminated; and decreasing the gain of the amplifier in discrete steps to reach a mute state upon termination of said call.
According to another aspect of the invention, there is provided a method for gradually decreasing the gain of an amplifier to reach a mute state when a call is terminated comprising the steps of: determining when a call is initiated; increasing the gain of a mute circuit for receiving a signal output from a microphone to reach an unmute state; determining when a call is terminated; and decreasing the gain of the mute circuit in discrete steps to reach a mute state upon termination of said call.
REFERENCES:
patent: 3806663 (1974-04-01), Peek et al.
patent: 3963868 (1976-06-01), Randmere et al.
patent: 4091380 (1978-05-01), Yu
patent: 4700382 (1987-10-01), Means et al.
patent: 4864573 (1989-09-01), Horsten
patent: 4893349 (1990-01-01), Eastmond et al.
patent: 5146610 (1992-09-01), Longshore et al.
patent: 5191606 (1993-03-01), Juang
patent: 5276917 (1994-01-01), Vanhanen et al.
patent: 5339452 (1994-08-01), Sugawara
patent: 5627857 (1997-05-01), Wilson
patent: 5857019 (1999-01-01), Iglehart et al.
patent: 5946384 (1999-08-01), Yee et al.
patent: 6169886 (2001-01-01), Black et al.
patent: 6181949 (2001-01-01), Ozluturk et al.
patent: 6194978 (2001-02-01), Romano
Bost Dwayne
Dilworth & Barrese LLP
Gelin Jean A
Samsung Electronics Co,. Ltd.
LandOfFree
Method for controlling gain of transmission signal does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Method for controlling gain of transmission signal, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Method for controlling gain of transmission signal will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2897058