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A GFSK (Gaussian Frequency Shift Keying) radio transceiver is provided for ISM (Industrial Scientific and Medical) wideband communication. The GFSK radio transceiver includes a transmitter for modulating transmitted signal into RF signal, and a receiver for demodulating received signal into digital form. The transmitter includes a VCO for generating an oscillating signal serving as a carrier signal in the transmitter and a first local oscillating signal in the transmitter; and a variable-gain power amplifier, capable of being adjustable between two gain values, for amplifying the RF signal. The receiver includes a mixer for downconverting the received signal into a first IF signal by using the first local oscillating signal from the transmitter; and an IF demodulator for downconverting the first IF signal into a second IF signal by using a locally generated second local oscillating signal. The GFSK radio transceiver can operate either in half-duplex mode or full-duplex mode in a time-division duplex (TDD) system through micro-processor controls. Further, it utilizes a variable-gain power amplifier that can improve the drawbacks of interference and high power consumption with the prior art, and further utilizes a single wideband VCO to generate an oscillating signal that can be used both as the carrier signal in the transmitter and the first local oscillating signal for the receiver. This allows the GFSK radio transceiver to be implemented with a fewer number of VCOs as compared to the prior art, thus reducing the manufacturing cost.
SUMMARY OF THE INVENTION
It is therefore an objective of the present invention to provide a GFSK radio transceiver for ISM wideband communication, which can be used in conjunction with a time-division duplex (TDD) system and operate selectively in either half-duplex mode or full-duplex mode.
It is another objective of the present invention to provide a GFSK radio transceiver for ISM wideband communication, which utilizes a variable-gain power amplifier that can help improve the problems of interference and high power consumption that are drawbacks with the prior art.
It is still another objective of the present invention to provide a GFSK radio transceiver for ISM wideband communication, which utilizes only one single wideband VCO to generate an oscillating signal that can be used both as the carrier signal in the transmitter and as a local oscillating signal in the receiver, thus allowing the GFSK radio transceiver of the invention to be implemented with a fewer number of VCOs as compared to the prior art so that the manufacturing cost of the GFSK radio transceiver of the invention can be reduced.
In accordance with the foregoing and other objectives of the present invention, a new GFSK radio transceiver is provided for ISM wideband communication. The GFSK radio transceiver of the invention comprises a transmitter and a receiver.
The transmitter used for modulating transmitted signal into RF signal comprises a VCO and a variable-gain power amplifier. The VCO is used for generating an oscillating signal serving as a carrier signal for the transmitted signal. The variable-gain power amplifier, which is capable of being adjustable between a low-power gain and a high-power gain, is used for amplifying the RF signal.
The receiver, which is used for demodulating received signal into digital form, comprises a mixer, a local oscillator and an IF demodulator. The mixer is used for downconverting the received signal into a first IF signal by mixing the received signal with a first local oscillating signal which is fetched from the oscillating signal from the VCO in the transmitter. The local oscillator is used for generating a second local oscillating signal. The IF demodulator is used for downconverting the first IF signal from the mixer into a second IF signal by mixing the first IF signal with the second local oscillating signal.
Compared to the prior art, the GFSK radio transceiver of the invention can operate either in half-duplex mode or in full-duplex mode in a TDD system through micro-processor controls. Further, the GFSK radio transceiver of invention utilizes a variable-gain power amplifier that can improve the problems of interference and high power consumption that are drawbacks with the prior art. Moreover, the GFSK radio transceiver of the invention utilizes one single wideband VCO to generate an oscillating signal that can be used both as the carrier signal in the transmitter and as a first local oscillating signal in the receiver. This feature allows the GFSK radio transceiver of the invention to be implemented with a fewer number of VCOs as compared to the prior art, thus reducing the manufacturing cost.
As a summary, the prior art has the following drawbacks.
(1) First, it requires the use of two frequency synthesizers to implement, which makes both the design and the manufacture of the radio transceiver more complex to carry out.
(2) Second, the scheme of combining two frequency synthesizers into one single unit requires the use of a wideband VCO, a fast switching time, and a large frequency shift in data switching, which would make the radio transceiver very difficult to realize.
(3) Third, the power amplifier used in the prior art is a one-stage amplifier with a fixed gain, which would cause interference to other nearby radio transceivers and high power consumption to the radio transceiver itself, leading to a poor signal quality in transmitting and reception and also a reduced number of radio transceivers that can be used at the same time and the same site.
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