Telecommunications – Transmitter and receiver at same station – With transmitter-receiver switching or interaction prevention
Reexamination Certificate
1997-09-29
2001-05-08
Bost, Dwayne (Department: 2681)
Telecommunications
Transmitter and receiver at same station
With transmitter-receiver switching or interaction prevention
C455S079000, C455S024000, C455S063300, C455S278100, C455S296000, C370S278000
Reexamination Certificate
active
06229992
ABSTRACT:
The invention relates to full-duplex radio transmitter/receivers. With such radio transceivers the antenna arrangement may comprise a common transmit/receive antenna, or electrically separated antennas which are physically joined together or physically and electrically separate antennas which can be an the same housing or otherwise positioned very close to one another. Such a transmitter/receiver, or transceiver unit, conventionally employs a diplexer filter to prevent the receiver components being overloaded by signals coupled from the transmitter channel. The two channel frequencies are separate and the filter discriminates the signals on the basis of frequency.
For optimum radio spectrum utilisation the transmit/receive frequencies should be close, but constraints on the design of the diplexer filter mean that the smaller the transmit/receive frequency split, the bulkier and costlier is the diplexer filter. Largely for this reason the current cellular radio telephone system operating at 900 MHz has a transmit/receive channel split of 45 MHz, namely about 5% of the operating frequency. Many systems, including the recently proposed 220 MHz system in the USA, operate with a much narrower transmit/receive split, eg 1 MHz at 220 MHz. This represents only about 0.45% and the bulk and expense of an adequate diplexer filter would prohibit the satisfactory implementation of hand-held full-diplex transceivers.
An object of the invention is to provide a transceiver with an alternative to a diplexer filter.
According to the invention there it provided a radio transceiver, comprising:
at least one antenna, for receiving signals and for transmitting signals;
means for generating signals to be transmitted;
means for processing received signals;
means for generating a cancellation signal from the signals to be transmitted;
means for subtracting the cancellation signal from the received signals to produce cancelled received signals for processing; and,
means for controlling the generation of the cancellation signal in order to minimise the amount of the signals for transmission appearing in the cancelled received signals.
This has the advantage that the transmitter output signal can be largely removed from the receiver input, irrespective of the presence or otherwise of a transmit/receive frequency split.
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Bateman Andrew
Beach Mark Anthony
Kenington Peter Blakeborough
McGeehan Joseph Peter
Slingsby Wycliffe Timothy
Bost Dwayne
Persino Raymond B.
Townsend and Townsend / and Crew LLP
University of Bristol
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