Telecommunications – Transmitter and receiver at same station – With a common signal processing stage
Reexamination Certificate
1997-09-19
2002-07-16
Trost, William (Department: 2683)
Telecommunications
Transmitter and receiver at same station
With a common signal processing stage
C455S260000, C455S076000, C329S325000
Reexamination Certificate
active
06421530
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention in general relates to a radio circuit in which the frequency of a local oscillator differs from the transmit frequency or the receive frequency and to a mobile radio apparatus using the same.
2. Related Art of the Invention
In recent years, the mobile communication has rapidly become pervasive and for the radio circuit, it is important to achieve smaller size and lower power consumption. Hereinafter, an example of a conventional radio circuit will be described with reference to the drawing.
FIG. 5
shows the construction of the conventional radio circuit. In
FIG. 5
, reference numeral
41
represents a first local oscillator, reference numeral
42
represents a second transmit local oscillator, reference numeral
43
represents a second receive local oscillator, reference numeral
44
represents a receive frequency converter, reference numeral
45
represents a demodulator, reference numeral
46
represents a transmit frequency converter, reference numeral
47
represents a modulator, reference numeral
48
represents a receive amplifier, reference numeral
49
represents a transmit amplifier, reference numeral
50
represents a duplexer, and reference numeral
51
represents an antenna.
The modulator
47
modulates the output signal of the second transmit local oscillator
42
with a modulating signal to output a transmit intermediate frequency signal. The transmit intermediate frequency signal is converted into a transmit frequency by the first local oscillator
41
at the transmit frequency converter
46
, amplified by the transmit amplifier
49
, passed through the duplexer
50
and sent out from the antenna
51
. The receive signal received by the antenna
51
is passed through the duplexer
50
and amplified by the receive amplifier
48
. The amplified receive signal is input to the receive frequency converter
44
to be frequency-converted into a receive intermediate frequency signal with the output of the first local oscillator
41
. The demodulator
45
demodulates the receive intermediate frequency signal into a baseband signal with the output of the second receive local oscillator
43
.
However, with this arrangement, three local oscillators
41
,
42
and
43
are required and it is therefore difficult to achieve size reduction. In addition, since the local oscillators generate different frequencies, spurious emission readily occurs in transmitting signals and interference readily arises in receiving signals.
SUMMARY OF THE INVENTION
In view of the above-mentioned problems of the conventional radio circuit, it is an object of the present invention to provide a radio circuit suitable for size reduction and in which undesired spurious emission does not occur.
A radio circuit of the present invention comprises a local oscillator, a first receive frequency converter, a frequency divider and a demodulator,
wherein a receive signal and an output of the local oscillator are input to the first receive frequency converter, the receive signal is converted into a signal of a first intermediate frequency by the first receive frequency converter, the signal of the first intermediate frequency is input to the demodulator, the output of the local oscillator is frequency-divided by the frequency divider and input to the demodulator, the signal converted into the first intermediate frequency is demodulated into a baseband signal by the demodulator.
A radio circuit of the present invention comprises a local oscillator, a first receive frequency converter, a second receive frequency converter, a frequency divider and a demodulator,
wherein a receive signal and an output of the local oscillator are input to the first receive frequency converter, the receive signal is converted into a signal of a first intermediate frequency by the first receive frequency converter, the signal of the first intermediate frequency is input to the second receive frequency converter, the output of the local oscillator is frequency-divided by the frequency divider and input to the second receive frequency converter, the signal of the first intermediate frequency is frequency-converted into a signal of a second intermediate frequency by the second receive frequency converter, the signal converted into the second intermediate frequency and a reference signal of the local oscillator are input to the demodulator, the signal of the second intermediate frequency is demodulated into a baseband signal by the demodulator, and a frequency of the reference signal equals the second intermediate frequency.
A radio circuit of the present invention comprises a local oscillator, a transmit frequency converter, a frequency divider and a modulator, wherein an output of the local oscillator is input to the transmit frequency converter and is also input to the frequency divider to be frequency-divided, an output signal of the frequency divider is input to the modulator, the output signal of the frequency divider is modulated into a transmit intermediate frequency signal by the modulator with a modulating signal, and the transmit intermediate frequency signal is input to the transmit frequency converter to be frequency-converted into a signal of a transmit frequency.
A radio circuit of the present invention comprises a local oscillator, a frequency divider, a modulator and a local frequency converter, wherein an output of the local oscillator is input to the frequency divider to be frequency-divided, the local frequency converter. receives the output of the local oscillator and an output of the frequency divider to output a signal of a transmit frequency, and the modulator modulates an output of the local frequency converter with a modulating signal to output a signal of the transmit frequency.
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Behzad Razavi, RF Microelectronics, Prentice Hall PTR, pp. 290-295, 1998.
Adachi Hisashi
Haruki Hiroshi
Ikeda Kazuhiko
Ishida Kaoru
Kosugi Hiroaki
Matsushita Electric - Industrial Co., Ltd.
Smith , Gambrell & Russell, LLP
Sobutka Philip J.
Trost William
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