Telecommunications – Transmitter and receiver at same station – With transmitter-receiver switching or interaction prevention
Reexamination Certificate
1999-01-15
2001-10-23
Maung, Nay (Department: 2681)
Telecommunications
Transmitter and receiver at same station
With transmitter-receiver switching or interaction prevention
C455S227000, C455S431000, C455S528000, C370S276000
Reexamination Certificate
active
06308052
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to communication systems and, more particularly, to communication systems such as two-way radios utilized by air-traffic control towers and pilots.
2. Description of the Related Art
Air-traffic control systems (that is, communications between an airport control tower and aircraft) utilize a communication system known as a half duplex communication system. In such a communication system, two-way communications between the tower and one of many aircraft in the vicinity is on the same voice frequency. In this environment, there are multiple transmitter and receivers operating on the same voice frequency such that each receiver receives every transmission. If more than one aircraft transmits at the same time or if any aircraft transmits during a control-tower transmission, then the received signal to all parties on that frequency will experience interference. In addition, the transmitting parties may not be aware of such interference and will not receive the other transmissions.
In a typical scenario, if no transmissions are occurring and if every radio is in receive mode (i.e., no one is transmitting) at the designated frequency for that flight region, then either one of the pilots or the control tower can initiate a transmission at any time. As soon as any transmission is received and heard, it is expected that no other transmission can be initiated until the airways are clear. However, a transmission may not be heard for one of many conceivable reasons, such as simultaneous transmissions, a noisy aircraft environment, a malfunctioning or intermittent headset, and so on.
The current allocation of control frequencies for air-traffic control is 118 MHz to 136 MHz, which yields a bandwidth of 18 MHz. The 18-MHz bandwidth is currently divided into 720 voice channels of 25 kHz. This current voice-channel bandwith is expected to be reduced to 8.33 kdHz (i.e., one-third of the current bandwidth). This proposed reduction in the current voice-channel bandwidth would offer the opportunity to implement many enhancements that could contribute to a more dependable and accurate communication environment.
In view of the foregoing, there is a need in the art of half-duplex communication systems or a radio that is able to indicate to a user when a transmission is taking place.
BRIEF SUMMARY OF THE INVENTION
In view of the foregoing, the present invention provides methods and apparatus for visually indicating that a transmission is currently taking place in an air-traffic environment which utilizes a half-duplex communication system. Accordingly, a pilot or an air-traffic controller can easily determine that the airwaves are free for a transmission and can make such a transmission knowing that he or she will not be interrupting a transmission currently taking place between a control tower and other aircraft. In addition, a pilot or an air-traffic controller can determine if another transmission takes place while he or she is currently making a transmission, and, if so, can halt their current transmission and then retransmit when the airwaves are free again to ensure that the transmission is completely received.
According to one aspect of the present invention, a radio for a half-duplex communication system includes an antenna for receiving a remote signal and for transmitting a local signal. The remote signal and the local signal each include a voice signal and a beacon signal. The radio also includes a transceiver for providing the voice signal of the local signal and a warning circuit for providing an indication when a transmission is taking place.
The warning circuit includes a power splitter for receiving the remote signal from the antenna and for dividing the remote signal into the voice signal and the beacon signal thereof. The power splitter then provides the voice signal to the transceiver. The warning circuit also includes a comparator for comparing a level of the received beacon signal with a reference. The comparator provides an output to an indicator (such as an LED) when the level of the beacon signal is greater than the reference. In other words, the indicator illuminates in the presence of a beacon signal. According to a preferred embodiment of the radio, the beacon signal is generated by the warning circuit and mixed with the local voice signal from the transceiver prior to transmission.
Although adaptable to various communication environments such as police and emergency dispatchers, a preferred implementation of the radio of the invention is in an air-traffic environment. Each aircraft, as well as the control tower, in the environment utilizes the radio of the present invention to transmit and receive voice signals. The indicator of each of the radios accordingly illuminated when one of the radios is making a transmission. Each of the pilots and air-traffic controllers therefore knows when the airwaves are busy or free, and can initiate their own transmissions accordingly.
Other objects, features, and advantages of the present invention will become apparent to those skilled in the art from reading the following detailed description taken in conjunction with the accompanying drawings.
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patent: 4932071 (1990-06-01), Arndt et al.
patent: 5396651 (1995-03-01), Nitardy
patent: 5426666 (1995-06-01), Kato
patent: 5566359 (1996-10-01), Corrigan
Jamali Imran A.
Khatib Rami H.
Jamali Imran A.
Maung Nay
Satermo Eric K.
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