Dual conversion radio frequency transceiver
First Claim
1. A dual conversion radio frequency (RF) transceiver comprising:
- an antenna for transmitting and receiving RF signals;
a low noise amplifier for amplifying the received RF signals from the antenna;
a mixer for mixing the amplified RF signals from the low noise amplifier with first local oscillator signals to generate first IF (intermediate frequency) signals;
an IF filter for filtering the first IF signals from the mixer;
a local oscillator for providing second local oscillator signals;
a demodulator for demodulating the filtered first IF signals from the IF filter into first baseband signals by using the second oscillator signals from the local oscillator;
a baseband circuit for processing the first baseband signals from the demodulator and generating second baseband signals comprising I signals and Q signals to be transmitted;
a modulator for modulating the second baseband signals from the baseband circuit into second IF signals by using the second local oscillator signals from the local oscillator, the modulator comprising a phase shifter for converting the second local oscillator signals into 90 degree phase-shifted signals, an I mixer for mixing the I signals with the phase-shifted signals, a Q mixer for mixing the Q signals with the second local oscillator signals, and an adder for adding the outputs from the I and Q mixers to generate the second IF signals;
a frequency multiplier for multiplying the frequency of the second IF signals from the modulator by a predetermined factor to generate RF signals;
a power amplifier for amplifying the RF signals from the frequency multiplier and passing the amplified RF signals to the antenna;
wherein when the transceiver starts receiving the RF signals, the baseband circuit will produce a fixed baseband signal, the fixed baseband signal will be modulated into fixed frequency signals by the modulator by using the second local oscillator signals and setting the I signals of the second baseband signals to a non-zero constant value and setting the Q signals to zero, and the frequency of the fixed frequency signals will be multiplied by the frequency multiplier to generate the first local oscillator signals.
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Abstract
The present invention discloses a dual conversion RF transceiver which uses only one local oscillator for signal conversion to simplify system complexity and reduce production cost. The transceiver comprises a mixer for mixing input RF signals with first local oscillator signal to generate a first IF signal, an IF filter for filtering the first IF signal, a local oscillator for providing second local oscillator signal, a demodulator for demodulating the filtered first IF signal into first baseband signals by using the second oscillator signal, a baseband circuit for processing the first baseband signals and generating second baseband signals to be transmitted, a modulator for modulating the second baseband signals into a second IF signal by using the second local oscillator signal, and a frequency multiplier for multiplying the frequency of the second IF signal by a predetermined factor to generate a output RF signal. When the transceiver starts receiving the RF signals, the baseband circuit will produce a fixed baseband signal which will be modulated into fixed frequency signal by the modulator by using the second local oscillator signal. And the frequency of the fixed frequency signal will be multiplied by the frequency multiplier to generate the first local oscillator signal.
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Citations
10 Claims
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1. A dual conversion radio frequency (RF) transceiver comprising:
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an antenna for transmitting and receiving RF signals; a low noise amplifier for amplifying the received RF signals from the antenna; a mixer for mixing the amplified RF signals from the low noise amplifier with first local oscillator signals to generate first IF (intermediate frequency) signals; an IF filter for filtering the first IF signals from the mixer; a local oscillator for providing second local oscillator signals; a demodulator for demodulating the filtered first IF signals from the IF filter into first baseband signals by using the second oscillator signals from the local oscillator; a baseband circuit for processing the first baseband signals from the demodulator and generating second baseband signals comprising I signals and Q signals to be transmitted; a modulator for modulating the second baseband signals from the baseband circuit into second IF signals by using the second local oscillator signals from the local oscillator, the modulator comprising a phase shifter for converting the second local oscillator signals into 90 degree phase-shifted signals, an I mixer for mixing the I signals with the phase-shifted signals, a Q mixer for mixing the Q signals with the second local oscillator signals, and an adder for adding the outputs from the I and Q mixers to generate the second IF signals; a frequency multiplier for multiplying the frequency of the second IF signals from the modulator by a predetermined factor to generate RF signals; a power amplifier for amplifying the RF signals from the frequency multiplier and passing the amplified RF signals to the antenna; wherein when the transceiver starts receiving the RF signals, the baseband circuit will produce a fixed baseband signal, the fixed baseband signal will be modulated into fixed frequency signals by the modulator by using the second local oscillator signals and setting the I signals of the second baseband signals to a non-zero constant value and setting the Q signals to zero, and the frequency of the fixed frequency signals will be multiplied by the frequency multiplier to generate the first local oscillator signals. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10)
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Specification