Transceiver with a receive/transmit fast switch function

Details Transceiver with a receive/transmit fast switch function Transceiver with a receive/transmit fast switch function

1999-02-08

2002-04-09

Trost, William (Department: 2683)

Telecommunications

Transmitter and receiver at same station

With transmitter-receiver switching or interaction prevention

C455S076000, C455S260000, C455S084000

Reexamination Certificate

active

06370361

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to a transceiver, and in particular to a transceiver which has a function of fast switch between receive and transmit implemented by using different frequencies of intermediate frequency (IF) signals.
2. Description of the Prior Art
Today, communication technology, especially in radio communication systems, such as cellular phones and satellite communication, has been widely and swiftly developed and used. Generally, in low-tier personal digital communication systems, variety of modulation schemes can be grouped into IQ modulation systems and non-IQ modulation systems. The way for multiplex includes a time-division duplex (TDD) and a frequency-division duplex (FDD). In generally, to implement GFSK, modulation schemes are classified into Quadrature Modulation and Direct VCO Modulation. In the invention, GFSK modulation schemes applied in the non-IQ modulation system is adopted.
Typically, an IF block used for processing modulation & demodulation signals is included in chip sets in a personal communication system. In the transmission path, the IF block can convert a digital input signal to an analog modulated output signal that serves as an intermediate frequency input signal. In the Rx path, the IF block can also down convert and demodulate a receive signal into a baseband signal. Next, a conventional transceiver will be provided for description.
Referring to
FIG. 1
, a circuit block diagram of a conventional transceiver
14
a
is shown. The conventional transceiver
14
a
includes a receiver
102
, a transmitter
104
a,
a band pass filter
106
and a receive/transmit switch
108
. The receiver
102
includes a Mixer & IF AMP
110
and a discriminator
112
. The transmitter
104
a
includes a phase-lock-loop (PLL)
114
, a transmit signal switch
116
and a power amplifier
118
.
As to a receiving operation thereof, a modulated receive signal
20
a
received from an antenna
12
is filtered by the band pass filter
106
and then delivered to the receive/transmit switch
108
. According to a receive/transmit control signal
30
f,
the receive/transmit switch
108
feeds the filtered and modulated receive signal
122
into the Mixer & IF AMP
110
. At this time, according to an enable/disable signal
30
a,
the Mixer & IF AMP
110
can down convert the receive signal
122
to a Rx IF signal
126
in coordination with a local oscillation signal
124
. The discriminator
112
receives the Rx IF signal
126
, and then generates a demodulated receive signal
22
a.
In TDD mode, the Mixer & IF AMP
110
of the receiver
102
and the discriminator
112
can receive the enable/disable signal
30
a
for enabling/disabling.
Similarly, the transmitter
104
a
receives enable/disable signals
30
b,
30
c
and
30
d.
The phase-lock-loop
114
can receive a PLL enable/disable signal
30
b
to enable all active devices. The phase-lock-loop
114
can receive a VCO enable/disable signal
30
c
to enable/disable a voltage-controlled oscillator (VCO). The power amplifier
118
can be enabled/disabled according to an enable/disable signal
30
d.
The phase-lock-loop
114
included in the transmitter
104
a
is used to generate a radio frequency signal
130
. According to the receive/transmit control signal
30
f,
a required radio frequency signal
130
is selected by the transmit signal switch
116
. When the transceiver
14
a
is at a transmit mode, a radio frequency signal
132
output from the transmit signal switch
116
is fed into the power amplifier
118
, and then amplified. Afterwards, the amplified radio frequency signal
134
is fed into the receive/transmit switch
108
. According to the receive/transmit control signal
30
f,
the radio frequency signal
134
is filtered by the filter
106
, and then transmitted from the antenna
12
.
On the contrary, when the transceiver
14
a
is at a receive mode, a radio frequency signal
130
generated by the phase-lock-loop
114
is selected to serve as the local oscillation signal
124
of the receiver
102
by the transmit signal switch
116
, and then fed into the Mixer & IF AMP
110
of the receiver
102
.
As described above, the transmitter
104
a
and receiver
102
of the transceiver use the same intermediate frequency signal. Therefore, under a transmit mode, it is necessary to perform an open loop operation for preventing distortions caused to the modulated signal by the phase-lock-loop. Furthermore, the time for the open loop modulation system to reach a stable state cannot keep longer, leading to influence to data transmission amount. As a result, a system reaction delay is usually created to lower data transmission amount.
SUMMARY OF THE INVENTION
In view of the above, an object of the invention is to provide a transceiver with a receive/transmit fast switch function which can efficiently prevent interference caused during a signal receive/transmit operation by using different receive/transmit intermediate frequency signals. Additionally, the transceiver of the invention can also eliminate data distortion, lengthen transmission slot and decrease the stand-by time for receive/transmit switches.
The operation of the transceiver with a receive/transmit fast switch function according to the invention will be briefly described hereinafter.
Under a transmit mode, a carrier signal is generated and modulated by a frequency generator, and then fed into a transmitter. Inversely, under a receive mode, a frequency-fixed carrier signal is generated by the frequency generator. Moreover, a first intermediate frequency signal and a second intermediate frequency signal are generated by an intermediate frequency circuit, and then fed into the transmitter and the receiver to serve as local oscillation signals. When transmitting a signal, the modulated carrier signal and the first intermediate frequency signal are received by the transmitter. Then, the modulated carrier signal is up converted by a mixer, and then outputted. Oppositely, when receiving a signal, the receive signal is down converted by a mixer in coordination with the second intermediate frequency signal and the carrier signal, and then outputted. Finally, the receive signal is demodulated into an FSK signal by a discriminator. The transceiver frequency synthesizer is no longer re-set or changed into any frequency between Tx/Rx mode except that a new RF channel is allocated.


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