KR20050009345A - Radio signal transmit/receive switching circuit using low power switch in time division duplex system - Google Patents

Abstract

PURPOSE: A wireless transceiving switching circuit using a low-power switch in a TDD(Time Division Duplex) system is provided to transceive a high-power wireless signal by applying a circulator to a wireless antenna port for transceiving wireless signals, thereby reducing a manufacturing cost while decreasing an insertion loss. CONSTITUTION: A circulator(44) inputs a wireless signal received from a wireless antenna(40) through a coaxial cable(42) to a low noise amplifier(50) via a filter(46) and a low-power RF switch(48), and receives a wireless signal to be transmitted from a power amplifier(64), then wirelessly transmits the received signal through the wireless antenna(40). The receiving RF switch(48) consists of a low-power switch, and passes the wireless signal received from the circulator(44), so that the passed signal can be inputted to the low noise amplifier(50). The low noise amplifier(50) low noise-amplifies the wireless signal, while a mixer(54) converts the wireless signal into an IF signal through a frequency synthesis with a synthesizer(56). The power amplifier(64) power-amplifies the wireless signal, and wirelessly transmits the signal from the wireless antenna(40).

Description

Wireless transmit / receive switching circuit using low power switch in time division duplex system {RADIO SIGNAL TRANSMIT / RECEIVE SWITCHING CIRCUIT USING LOW POWER SWITCH IN TIME DIVISION DUPLEX SYSTEM}

The present invention relates to a wireless transmission and reception switching circuit using a low power switch in a time division duplex system, and more particularly, to a wireless transmission and reception switching circuit using a low power switch in a time division duplex system.

As is well known, the time division duplex system employs a time division duplex (TDD) scheme in which a base station or repeater and a mobile terminal use a radio transmission / reception frequency together when transmitting and receiving a signal in a radio access scheme. The time division duplex method performs transmission and reception between a base station or a repeater and a mobile terminal by temporally distributing a single frequency, that is, by adjusting a ratio of time slots allocated to each direction according to the amount of forward and reverse traffic. To make it possible.

That is, FIG. 1 shows a configuration of a wireless transmission / reception circuit applied to such a time division duplex system.

As shown in FIG. 1, the wireless transmit / receive circuit includes a wireless antenna 10, an RF switch 12, a filter 14, 18, 24, 30, a low noise amplifier 16, a mixer 20, 24, a synthesizer. And a power amplifier 28.

The RF switch 12 performs a switching connection for supplying a radio signal received from the radio antenna 10 to a receiving end equipped with a low noise amplifier 16, and wirelessly from a transmitting end equipped with a power amplifier 28. A switching connection for wirelessly transmitting a signal through the wireless antenna 10 is performed.

The low noise amplifier 16 low noise amplifies the radio signal passing through the filter 14 from the RF switch 12, and the mixer 20 converts the radio signal into an intermediate frequency signal by frequency synthesis with the synthesizer 22. The output will be converted to.

In addition, the mixer 24 converts the intermediate frequency signal into a wireless signal capable of wireless transmission by frequency synthesis with the synthesizer 22, and outputs the wireless power amplifier 28 that passes through the filter 26. Power amplification of the signal.

In the conventional general time division duplex system configured as described above, when the RF switch 12 is switched to the reception state, the radio signal received from the radio antenna 10 is passed through the filter 14 to the low noise amplifier. After low noise amplification at (16), it is converted into an intermediate frequency signal through the mixer (20) via the filter (18) and output.

On the other hand, when the RF switch 12 is in a switching state for signal transmission, the intermediate frequency signal is converted into a wireless signal through the mixer 24, and then amplified in the power amplifier 28 through the mixer 26, and then The radio is transmitted wirelessly via the wireless antenna 10 via the filter 30 and the RF switch 12.

Here, since the radio signal is a high power signal, the RF switch 12 is preferably a high power switch.

However, in such a conventional time division duplex system, in order to transmit a high power wireless signal normally, a high power RF switch 12 is used at a rear end of the high power power amplifier 28 that amplifies the high power wireless signal. Since the manufacturing cost is inevitably increased due to the use of a high priced high power RF switch, the insertion loss is caused by the characteristics of the high power switch and the MTBF is deteriorated.

Accordingly, the present invention has been made to solve the above-mentioned conventional problems, and an object thereof is to reduce the burden of insertion loss and to reduce the cost by allowing a low power RF switch to be applied to a wireless transceiver circuit of a time division duplex system. To provide a wireless transmission and reception switching circuit using a low power switch in a time division duplex system.

1 is a view showing a configuration of a wireless transmission and reception circuit applied to a conventional general time division duplex system,

2 is a view showing the configuration of a wireless transmission and reception switching circuit using a low power switch in a time division duplex system according to the present invention.

<Description of the symbols for the main parts of the drawings>

40: wireless antenna, 42: coaxial cable,

44: circulator, 46, 52, 60, 66: filter,

48,62: RF switch, 50: low noise amplifier,

54, 58: mixer, 56: synthesizer,

64: power amplifier.

In order to achieve the above object, according to the present invention, a circulator for inputting a radio signal received from a radio antenna to a signal receiving side, receiving a radio signal to be transmitted and transmitting the radio signal through a radio antenna, and at the time of signal transmission A signal transmitting end having a low power transmitting RF switch for switching connection, converting an intermediate frequency signal to be transmitted into a radio signal and outputting the power to the circulator after power amplification and filtering by the switching connection of the transmitting RF switch; It is equipped with a low power receiving RF switch for switching when receiving a signal, and a signal receiving end for outputting a radio signal from the circulator as an intermediate frequency signal through low noise amplification and filtering by the switching connection of the receiving RF switch. Low power in time division duplex systems It provides a wireless transmission and reception switching circuit using the position.

Hereinafter, the present invention configured as described above will be described in detail with reference to the accompanying drawings.

That is, FIG. 2 is a diagram illustrating a configuration of a wireless transmission / reception switching circuit using a low power switch in a time division duplex system according to the present invention.

As shown in FIG. 2, the wireless transmission / reception switching circuit using the low power switch according to the present invention includes a wireless antenna 10, a coaxial cable 42, a circulator 44, a filter 46, 52, 58, 64, RF switches 48, 62, Low Noise Amplifier (LNA) 50, Mixer 54, 58, Synthesizer 56, Power Amplifier; PA) 64.

The coaxial cable 42 connects between the wireless antenna 40 and the circulator 44 to minimize signal loss due to the transmission and reception of a wireless signal.

The circulator 44 inputs the wireless signal received from the wireless antenna 400 through the coaxial cable 42 to the low noise amplifier 50 through the filter 46 and the low output RF switch 48, and the power amplifier. A wireless signal to be transmitted from 64 is received, and the wireless signal is transmitted through the wireless antenna 400 through the coaxial cable 42.

The receiving side RF switch 48 is a low output switch, which is switched during the reception operation of the radio signal, passes the radio signal from the circulator 44 through the filter 46 and enters the low noise amplifier 50. Be sure to

The low noise amplifier 50 low noise amplifies the radio signal passing through the low power RF switch 48 of the receiving side, and the mixer 54 is low noise amplified by the low noise amplifier 50 and filters the filter 52. The radio signal that has passed is converted into an intermediate frequency signal by frequency synthesis with the synthesizer 56 and output.

In addition, the mixer 58 converts the intermediate frequency signal into a wireless signal capable of wireless transmission by frequency synthesis with the synthesizer 56, and outputs the radio frequency switch 62. In addition, the power amplifier is connected to the input side of the power amplifier 64 in order to reduce the influence on the noise level of the reception band, switching the wireless signal to be transmitted at the time of transmission of the wireless signal to pass through the filter 60 power amplifier Is applied to (64).

The power amplifier 64 power amplifies the radio signal passing through the filter 60 and the low power RF switch 62, and the power amplified radio signal is transmitted from the radio antenna 40 through the circulator 44. Allow wireless transmission.

In the present invention configured as described above, while the receiving RF switch 48 is switched off at the time of the transmission of the radio signal, the transmitting RF switch 62 is connected to the switching side from the transmitting RF switch 62. The wireless signal to be transmitted is power amplified by the power amplifier 64 and wirelessly transmitted by the coaxial cable 42 and the wireless antenna 40 via the filter 66 and the circulator 44.

In that state, the insertion loss of each filter is 1 dB, the insertion loss of the circulator 44 is 0.2 dB, and the Voltage Standing Wave Ratio (VSWR) between the circulator 44 and the coaxial cable 42 is shown. Is 1.2: 1, the loss of the coaxial cable 42 is 5dB, and the voltage standing wave ratio VSWR of the wireless antenna 40 is 1.5: 1, the insertion loss of the filter (1dB) + circulator 44 Insertion loss (0.2dB) + reflection due to voltage standing wave ratio of coaxial cable 42 (21dB) + insertion loss of circulator 44 (0.2dB) + insertion loss of filter (1dB) = 23.4dB The level of the signal input to the transmitting-side RF switch 62 is input at a level attenuated by about 23.4 dB relative to the output of the power amplifier 64.

That is, for example, in the case where the power amplifier 64 is used for 20 W (43 dBm) / 10 MHz, the RF switch 62 becomes a low output switch because the input level of the RF switch 62 becomes 20.6 dBm. Can be used.

On the other hand, in the case of receiving a radio signal in the radio transceiver circuit of the present invention, while the transmitting side RF switch 62 is switched off, the receiving side RF switch 48 is switched and connected, the radio antenna 40 Is applied to the RF switch 48 from the circulator 44 through the filter 46 via the coaxial cable 42, and the low noise amplifier 50 from the RF switch 48. Low noise amplification of the received wireless signal.

In that state, when the power amplifier 64 is powered on, the noise output from the power amplifier 64 affects the increase of the reception noise level, so that the power amplifier 64 is minimized to minimize the reception noise level. ) Should limit the gain.

For example, assuming that the gain of the power amplifier 64 is 15 dB and the noise figure is 5 dB, the power amplifier 64 has thermal noise (-174 dBm) + band 10 MHz (70 dB) + gain (15 dB) + noise figure. Since (5dB) = -84dBm / Hz, the noise level at the time of no signal becomes -84dBm / 10MHz.

Therefore, the low noise amplifier 50 by the output noise level of the power amplifier 64 is -84dBm / 10MHz, the noise level of the power amplifier 64 (-84dBm / 10MHz)-the insertion loss of the filter (1dB)-coaxial Reflection by the voltage standing wave ratio (VSWR) of the cable (23 dB)-Insertion loss of the circulator 44 (0.2 dB)-Insertion loss of the filter (1 dB)-Insertion loss of the RF switch 48 (0.2 dB) =- Since it is 109.6dBm / 10MHz, its input level is -109.6dBm / 10MHz.

On the other hand, the present invention is not limited to the above-described typical preferred embodiments, but can be carried out in various ways without departing from the gist of the present invention, various modifications, alterations, substitutions or additions are common in the art Those who have knowledge will easily understand. If the implementation by such improvement, change, replacement or addition falls within the scope of the appended claims, the technical idea should also be regarded as belonging to the present invention.

According to the present invention as described above, by applying a circulator to the port side of the wireless antenna for transmitting and receiving wireless signals in the wireless transmission and reception circuit of the time division duplex system to apply the RF switch as a low output switch As it is possible to reduce the manufacturing cost while applying a low-power low-cost switch, and the insertion loss of the circuit is reduced has the effect that the MTBF can be improved.

Claims (7)

A circulator for inputting a radio signal received from a radio antenna to a receiver of a signal, receiving a radio signal to be transmitted, and transmitting the radio signal through a radio antenna; It has a low output RF switch for switching at the time of signal transmission, and converts the intermediate frequency signal to be transmitted into a radio signal and outputs it to the circulator after power amplification and filtering by the switching connection of the transmitting RF switch. A signal transmitting end, It is equipped with a low power receiving RF switch for switching when receiving a signal, and a signal receiving end for outputting a radio signal from the circulator as an intermediate frequency signal through low noise amplification and filtering by the switching connection of the receiving RF switch. Wireless transmission and reception switching circuit using a low power switch in a time division duplex system, characterized in that. The method of claim 1, Wireless transmission and reception switching circuit using a low power switch in a time division duplex system, characterized in that connected between the wireless antenna and the circulator by a coaxial cable. The method of claim 1, The signal transmitting end is a low output switch in a time division duplex system, characterized in that a low output transmitting side RF switch is connected between a filter and an input of a power amplifier, and a filter is connected between the output end of the power amplifier and a circulator. Wireless transmission and reception switching circuit using. The method of claim 1, The signal receiver is connected to a low-frequency receiving side RF switch between a filter and an input of a low noise amplifier, and a filter is connected to the output of the low noise amplifier. Circuit. The method of claim 2 or 3, The low power transmit side RF switch has an attenuated signal level at the output of the power amplifier due to the sum of the insertion loss of the filter, the insertion loss of the circulator, and the reflection by the voltage standing wave ratio (VSWR) of the coaxial cable. Wireless transmission and reception switching circuit using a low power switch in a time division duplex system characterized in that determined. The method according to claim 2 or 4, Low power in a time division duplex system, characterized in that the signal-free noise level of the power amplifier upon reception of the wireless signal is determined by the sum of the thermal noise of the corresponding power amplifier and the noise, gain, and noise figure of the specific band. Wireless transmission and reception switching circuit using a switch. The method of claim 6, The input level of the low noise amplifier upon reception of the wireless signal is determined by the noise level in the no signal of the power amplifier and the reflection caused by the insertion loss of the filter, the insertion loss of the circulator, and the voltage standing wave ratio (VSWR) of the coaxial cable. Wireless transmission and reception switching circuit using a low power switch in a time division duplex system, characterized in that determined by the estimate.