KR20020074751A - Noise reduction apparatus in wireless transceiver - Google Patents

Abstract

PURPOSE: An apparatus for reducing noises in a wireless transmit-receive system is provided to reduce the noise generated by the difference between transmit power and receive power in a TDD(Time Division Duplex) wireless transmit-receive system by installing a dummy current switch activated selectively according to the magnitude of a transmit power control signal and maintaining the difference of transmit power and receive power identically. CONSTITUTION: A TDD wireless transmit-receive system comprising a dummy current switch(234) consists of a receiving part and a transmitting part. The receiving part is composed of a low noise amplifier(206), BPFs(Band Pass Filters)(208,212), a mixer(210), an IF(Intermediate Frequency) amplifier(214), an IF processor(216), and a buffer amplifier(224). The signal received to an antenna is transferred to the receiving part through a BPF(202) and a TDD switch(204). The TDD switch(204) connects the BPF(202) with the receiving part. The received signal is primarily amplified by the low noise amplifier(206). Then the amplified signal is filtered through the BPF(208). The mixer(210) mixes the output of the BPF(208) with a local oscillation signal, generated from the voltage controller oscillator(222) of the transmitting part and inputted through the buffer amplifier(224), and generates the first IF signal, 110.592MHz. The IF processor(216) converts the first IF signal into the second IF signal, demodulates it, and generates a received data signal(DATA_IN).

Description

Noise reduction apparatus in wireless transceiver system

The present invention relates to a wireless transmission and reception system, and more particularly to a wireless transmission and reception system of a time division duplex (TDD).

Wireless transmission / reception systems using TDD include CT-2, DECT, and Bluetooth. The TDD wireless transmission / reception system will be described with reference to FIG. 1 as follows.

FIG. 1 is a block diagram illustrating a configuration of a conventional time division duplex (TDD) wireless transmission / reception system, and illustrates a case of DECT (Digital European Cordless Telephone or Digital Enhanced Cordless Telephone).

In FIG. 1, the signal received at the antenna is transmitted to the receiver via the bandpass filter 102 and the TDD switch 104. The receiver comprises a low noise amplifier 106, a band pass filter 108, 112, a mixer 110, an intermediate frequency amplifier 114, an intermediate frequency processor 116, and a buffer amplifier 118. The transmitter includes a Gaussian filter 120, a voltage controlled oscillator 122, a phase locked loop circuit 124, a buffer amplifier 124, a band pass filter 126, a drive amplifier 128, and a power amplifier 130, 132. It consists of. The DECT wireless transmit / receive system operates in the TDD scheme in the 1881.972 MHz to 1897.344 MHz band. The transmission frequency and the reception frequency are the same, and the transmission unit and the reception unit alternately operate according to the period of the TDD and are transmitted to the antenna through the TDD switch 104.

In the reception mode, the TDD switch 104 connects the bandpass filter 102 to the receiver. The received signal is first amplified by the low noise amplifier 106 so that unnecessary band signals are removed from the bandpass filter 108. The mixer 110 mixes the output of the bandpass filter 108 and the local oscillation signal to generate a first intermediate frequency signal of 110.592 MHz. The local oscillation signal is input to the mixer 110 through the buffer amplifier 118 the oscillation signal generated by the voltage controlled oscillator 122 to be described in the transmitter. The intermediate frequency processor 116 receives the first intermediate frequency signal, converts it to a second intermediate frequency, and demodulates it to generate a received data signal DATA_IN.

In the transmission mode, the TDD switch 104 connects the bandpass filter 102 to the transmitter. The transmission data signal DATA_OUT which has passed through the Gaussian filter 120 is converted into a transmission frequency of 1881.792 MHz to 1897.344 MHz by the voltage controlled oscillator 122 and transmitted to the band pass filter 126 via the buffer amplifier 124. The bandpass filter 126 removes unnecessary signals such as harmonics from the input transmission data signal DATA_OUT, and is then amplified by the driving amplifier 128 and the power amplifier 132 to transmit the TDD switch 104 and the band. The pass filter 102 is transmitted to the radio section through the antenna. The amplification degree in the driving amplifier 118 and the power amplifiers 130 and 132 is determined by the transmission power control signal.

Such a TDD wireless transmission / reception system is affected by noise of various causes. Representative types of noise include noise due to the induction of the RF signal that changes in the TDD period, and noise due to the difference in current consumption in the transmission mode and the reception mode. Noise caused by RF signal induction is compensated for by shielding. The countermeasure against noise due to the difference in current consumption is to smooth the change of the current (voltage) using a capacitor as much as possible, and to design enough to withstand the change of the current (voltage) when designing a main circuit. There is a way.

However, among the methods of minimizing the influence on the noise caused by the difference in current consumption, the method using the capacitor has a limit in preventing the deterioration of the call quality due to the noise in the voice communication system. This is because the signal level that a person can recognize during a call is very low. In addition, the design of the main circuit to withstand the noise caused by the current (voltage) change has to invest a lot of time and effort in the design.

The apparatus for reducing noise of a wireless transmission / reception system according to the present invention includes a dummy current switch selectively activated according to the size of a transmission power control signal, thereby maintaining the same transmission power and reception power in the TDD wireless transmission / reception system. Its purpose is to reduce noise generated by the difference between transmit and receive power.

An apparatus for reducing noise in a wireless transmission / reception system according to the present invention for this purpose includes a receiver, a transmitter, and a dummy current switch. The receiver receives a radio signal through an antenna and demodulates the received radio signal to generate a received data signal. The transmitter modulates the transmission data signal, amplifies the signal modulated according to the transmission power control signal to a predetermined size, and transmits the signal to the wireless section through the antenna. The dummy current switch operates in the transmission mode in which the transmitter operates, and generates a current consumption corresponding to the difference between the receiver current of the receiver and the transmitter current of the transmitter.

1 is a block diagram showing the configuration of a conventional time division duplex (TDD) wireless transmission and reception system.

Figure 2 is a block diagram showing the configuration of a time division bidirectional transmission and reception system with a dummy current switch (Dummy Current Switch) according to the present invention.

Figure 3 is a circuit diagram showing a dummy current switch of the noise reduction device of a wireless transmission and reception system according to the present invention.

Explanation of symbols on the main parts of the drawings

102, 202, 108, 208, 112, 212: bandpass filter

104, 204: TDD switch

106,206: Low Noise Amplifier

110, 210: Mixer

114, 214: intermediate frequency amplifier

116, 216: intermediate frequency processor

118, 124, 218, 224: buffer amplifier

120, 220 Gaussian filter

122, 222: voltage controlled oscillator

124, 224: phase locked loop circuit

128, 228 drive amplifier

130, 132, 230, 232: power amplifier

234: dummy current switch

302: Transistor

304, 306: resistance

308: Inverter

DATA_IN: Receive data signal

DATA_OUT: Transmission data signal

A preferred embodiment of the noise reduction apparatus of the wireless transmission / reception system according to the present invention will be described with reference to FIGS. 2 and 3 as follows. FIG. 2 is a block diagram showing the configuration of a time division bidirectional wireless transmission / reception system including a dummy current switch according to the present invention. FIG. 2 is a diagram illustrating a case of DECT (Digital European Cordless Telephone or Digital Enhanced Cordless Telephone). to be.

In FIG. 2, the signal received at the antenna is delivered to the receiver via the bandpass filter 202 and the TDD switch 204. The receiver comprises a low noise amplifier 206, a band pass filter 208, 212, a mixer 210, an intermediate frequency amplifier 214, an intermediate frequency processor 216, and a buffer amplifier 218. The transmitter includes a Gaussian filter 220, a voltage controlled oscillator 222, a phase locked loop circuit 224, a buffer amplifier 224, a band pass filter 226, a drive amplifier 228, and a power amplifier 230, 232. It consists of. The DECT wireless transmit / receive system operates in the TDD scheme in the 1881.972 MHz to 1897.344 MHz band. The transmission frequency and the reception frequency are the same, and the transmitter and the receiver alternately operate according to the period of the TDD, and are transmitted to the antenna through the TDD switch 204. A transmission power control signal is input to the dummy current switch 234. The dummy current switch operates according to the magnitude of the transmission power control signal to generate a current consumption of a magnitude corresponding to the difference between the current amount of the transmission power and the current amount of the reception power, thereby eliminating the difference between the transmission power and the reception power.

In the reception mode, the TDD switch 204 connects the bandpass filter 202 to the receiver. The received signal is first amplified by the low noise amplifier 206 so that unnecessary band signals are removed from the bandpass filter 208. The mixer 210 mixes the output of the bandpass filter 208 and the local oscillation signal to generate a first intermediate frequency signal of 110.592 MHz. The local oscillation signal is input to the mixer 210 through the buffer amplifier 218, the oscillation signal generated by the voltage controlled oscillator 222 to be described in the transmitter. The intermediate frequency processor 216 receives the first intermediate frequency signal, converts it to a second intermediate frequency, and demodulates it to generate a received data signal DATA_IN.

In the transmission mode, the TDD switch 204 connects the bandpass filter 202 and the transmitter. The transmission data signal DATA_OUT passing through the Gaussian filter 220 is converted into a transmission frequency of 1881.792 MHz to 1897.344 MHz by the voltage controlled oscillator 222 and transmitted to the band pass filter 226 through the buffer amplifier 224. The bandpass filter 226 removes unnecessary signals such as harmonics from the input transmission data signal DATA_OUT, and is then amplified by the driving amplifier 228 and the power amplifier 232 to transmit the TDD switch 204 and the band. The pass filter 202 is transmitted to the radio section through the antenna. The amplification degree in the driving amplifier 218 and the power amplifiers 230 and 232 is determined by the transmission power control signal.

3 is a circuit diagram illustrating a dummy current switch of a noise reduction device of a wireless transmission / reception system according to the present invention.

As shown in FIG. 3, the collector of the transistor 302 is supplied with a power supply voltage VCC through three parallel resistors 304, and the emitter is grounded. The collector and base of this transistor 302 are connected via a resistor 306. The base is also controlled by the transmission power control signal inverted by the inverter 308. That is, when the transmission power control signal is greater than or equal to a certain magnitude, the output of the inverter 308 becomes low level, and the transistor 302 is turned on. When the transistor 302 is turned on, a certain amount of current flows through the parallel resistor 304, and the magnitude of the parallel resistance is such that the amount of current flowing corresponds to the difference between the current in the transmission mode and the current in the reception mode. Determine. In general, in the TDD DECT system, there is a current difference of about 60 mA between the reception mode and the transmission mode. Accordingly, the size of the parallel resistor 304 is determined so that an output current of about 60 mA is generated when the transistor 302 is turned on.

By the operation of the dummy current switch 234, the current (voltage) difference between the transmission power and the reception power of the TDD-type wireless transmission / reception system is removed, thereby greatly suppressing noise generation.

The apparatus for reducing noise of a wireless transmission / reception system according to the present invention includes a dummy current switch selectively activated according to the size of a transmission power control signal, thereby maintaining the same transmission power and reception power in the TDD wireless transmission / reception system. It provides an effect of reducing noise generated by the difference between the transmit power and the receive power.

Claims (3)

A receiver which receives a radio signal through an antenna and demodulates the received radio signal to generate a received data signal; A transmitter for modulating a transmission data signal, amplifying the modulated signal to a predetermined size according to a transmission power control signal, and then transmitting the signal to a wireless section through the antenna; And a dummy current switch operating in a transmission mode in which the transmitter operates, and generating a current consumption corresponding to a difference between a reception current of the receiver and a transmission current of the transmitter. The method of claim 1, wherein the dummy current switch, A first resistor having one end connected to the power supply voltage; An inverter for inverting the transmission power control signal; And a switching means switched on / off by the output signal of the inverter. The method of claim 2, wherein the switching means, And a emitter is grounded, a collector is connected to the other end of the first resistor, and the transistor is configured to feed back the output current of the collector to a base through a second resistor.