KR20000050720A - Carrier frequency transceiver for automatic control of frequency in communication system - Google Patents

Abstract

PURPOSE: A transceiver of carrier wave for adjusting frequency automatically in a communication system, is provided automatically to detect similar coherence as a base station and a mobile station operates as a synchronous loop and tracking carrier frequency difference of the mobile station in a base band, by use of a signal received from the base station, and to escape an interference between transmitted and received signals, as a transmitted and received wireless frequency and an intermediate frequency are intervened at a transmitted and received interval. CONSTITUTION: A transceiver of carrier wave for adjusting frequency automatically in a communication system, comprises a frequency difference tracker(211) and control frequency generator(212), a carrier frequency generator(220), a receive processor(230), and a transmit processor(240). The frequency difference tracker(211) tracks difference between carrier frequencies received/transmitted from the base station. The control frequency generator(212) generates a control frequency according to the tracked difference. The carrier frequency generator(220) generates a first and a second carrier frequency which are standardized at upward/downward conversion of frequency of signals received/transmitted from the base station. The receive processor(230) converts a higher frequency receive signal into base band signal downward, and deletes the difference according to the control frequency, to receive the receive signal. The transmit processor(240) converts the base band signal into a higher frequency signal upward, deletes the difference, to transmit the upwardly converted higher signal.

Description

Carrier transceiver for automatic frequency adjustment in communication system {CARRIER FREQUENCY TRANSCEIVER FOR AUTOMATIC CONTROL OF FREQUENCY IN COMMUNICATION SYSTEM}

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a carrier transceiver device in a communication system, and more particularly, to a carrier transceiver device capable of automatically adjusting a frequency difference between a base station and a mobile station in a code division multiple access (CDMA) communication system. .

In general, a communication system needs to adjust the frequency difference between a transmitter and a receiver for accurate detection of a signal.

In addition, the mobile radio communication channel is divided into a forward channel from the base station to the mobile stations and a reverse channel from the mobile station to the base station, and the carrier frequencies of the forward channel and the reverse channel should have a fixed difference.

However, in the actual communication system, since the hardware, that is, the frequency generator between the base station, the mobile station, and the mobile stations are used for each other, this carrier frequency separation has a variable frequency difference.

In this case, the mobile stations can track a single carrier frequency transmitted from a single base station through a forward channel. However, in the case of a base station, a single radio frequency (RF) receiving device transmits carrier signals from multiple mobile stations in a reverse channel. It should not track the transmit carrier frequency of any particular mobile station because it is receiving.

Therefore, for accurate signal recovery in such a channel environment, a method for more stable tracking and adjustment of frequency differences is needed.

1 is a configuration diagram of a carrier transceiver of a mobile station in a conventional communication system, which is largely divided into a transmitter and a receiver.

Here, the transmitting end and the receiving end are each controlled by the baseband processor 101 and are connected to the duplexer 102.

The transmitter comprises low pass filters 111 and 112, frequency upconverters 113 to 115, frequency controller 116, phase shifter 117, adder 118, and band pass filter. 119 and the frequency oscillator 120.

Here, the frequency up-converters 113 and 114, the phase shifter 117 and the adder 118 are modulation functions for modulating the transmission signal.

The receiver comprises frequency down converters 121 to 123, frequency oscillator 124, frequency controller 125, phase shifter 126, low pass filters 127 and 128, and band pass. It consists of a filter 129.

Here, the frequency down converters 121 and 122 and the phase shifter 126 are demodulation functions for demodulating the received signal.

In FIG. 1, the reference frequency oscillator 130, the frequency controller 131, and the carrier frequency oscillator 132 are shared by the transmitter and the receiver.

However, in the conventional carrier transmitting and receiving apparatus as described above, since the carrier receiving end and the transmitting end of the mobile station are controlled independently, it is very difficult to maintain a constant transmission / reception frequency separation of the mobile stations, and accordingly, the transmission and reception of each mobile station received by the base station Since the frequencies are not the same, there is a problem of greatly reducing the reception capability of the base station.

Accordingly, the present invention has been made to solve the above problems, by reducing the complexity of the system design and performance of the system by adjusting the transmission carrier of the mobile station within a tolerance that is suitable for the base station to receive It is an object of the present invention to provide a carrier transceiver in a communication system that can be significantly improved.

1 is a configuration diagram of a carrier transmitting and receiving device in a conventional communication system.

2 is a configuration diagram of an embodiment of a carrier transceiver for frequency automatic adjustment in a communication system according to the present invention;

3A and 3B are explanatory diagrams for an automatic tracking process of a carrier frequency difference of a carrier transceiver according to the present invention.

Explanation of symbols on the main parts of the drawings

210: baseband processing unit 211: frequency difference tracking unit

220: carrier frequency generator 221: reference frequency oscillator

222 and 223: frequency controller 224 and 225: carrier frequency oscillator

230: reception processing unit 231, 233, 235, 237: frequency down converter

232, 234: bandpass filter 238, 239: lowpass filter

240: transmission processor 241, 242: low pass filter

243, 245, 248: frequency upconverter 236, 244: phase shifter

246: adder 247: bandpass filter

250: duplexer

The present invention for achieving the above object, in the carrier transmitting and receiving apparatus in a communication system, by using the signal received from the base station to track the difference between the carrier frequency received from the base station and the carrier frequency transmitted to the base station, Frequency difference tracking and control frequency generating means for generating a control frequency in accordance with the tracked frequency difference tracking value; Carrier frequency generating means for generating first and second carrier frequencies as reference for frequency downconversion of the signal received from the base station and frequency upconversion of the signal transmitted to the base station; Down-converting a high frequency received signal received from the base station to a baseband signal using the first and second carrier frequencies and the control frequency, and removing the carrier frequency difference between the base station and the mobile station according to the control frequency Receiving processing means for receiving a signal; And up-convert the baseband signal for transmission to the base station to a high frequency signal using the first carrier frequency, and remove the carrier frequency difference between the base station and the mobile station according to the control frequency to transmit the upconverted high frequency signal. And transmission processing means.

Hereinafter, with reference to the accompanying drawings will be described in detail a preferred embodiment of the present invention.

2 is a configuration diagram of an apparatus for transmitting and receiving a carrier for automatic frequency adjustment in a communication system according to the present invention.

As shown in FIG. 2, the apparatus for transmitting and receiving carriers of the present invention includes a frequency difference tracking unit 211 which tracks a difference between a reception carrier frequency of a mobile station and a transmission carrier frequency of a base station using a signal received from a base station, and a frequency. A control frequency oscillator 212 for receiving a frequency difference tracked through the difference tracking unit 211 and oscillating a control frequency for controlling a difference between a reception carrier frequency of a mobile station and a transmission carrier frequency of a base station; A carrier frequency generator 220 for generating a carrier frequency to be used, a carrier frequency transmitted from the carrier frequency generator 220 and a control frequency transmitted from the control frequency oscillator 212 are used to generate a high frequency received signal. The baseband processor 2 performs down-conversion and removes a frequency difference between carrier frequencies using the control frequency. 10) frequency up-converts the baseband transmission signal into a high frequency signal by using the reception processor 230 for transmitting to the control unit 230 and the first carrier frequency transmitted from the control frequency and the carrier frequency generator 220, and converts the control frequency. The transmission processor 240 removes the frequency difference and transmits the radio frequency signal to the base station, and transmits the high frequency signal received from the base station to the reception processor 230 and transmits the high frequency signal transmitted from the transmission processor 240 to the base station. A duplexer 250 is provided.

The frequency difference tracking unit 211 is a functional unit performed in the baseband processor 210.

The carrier frequency generator 220 controls a carrier frequency according to a reference frequency oscillator 221 that generates a reference frequency as a reference for generation of a carrier frequency, and a reference frequency transmitted from the reference frequency oscillator 221. Frequency controllers 222 and 223 for generating signals, carrier frequency oscillator 224 controlled by frequency controller 222 to oscillate the first carrier frequency, and controlled by frequency controller 223 to second carrier Carrier frequency oscillator 225 oscillating frequency.

The reception processor 230 includes a frequency down converter 231 for down converting a high frequency signal received from a base station to a primary reception intermediate frequency band by using a first carrier frequency transmitted from the carrier frequency oscillator 224, and a frequency down converter. A band pass filter 232 for filtering out the output signal of the signal 231 to remove noise, and an intermediate frequency band for receiving the output signal of the band pass filter 232 using the control frequency transmitted from the control frequency oscillator 212. A frequency downconverter 233 for downconverting the signal, a bandpass filter 234 for removing noise by filtering the output signal of the frequency downconverter 233, and a second carrier frequency transmitted from the carrier frequency oscillator 225. A frequency downconverter 235 for downconverting the secondary intermediate frequency band signal transmitted from the bandpass filter 234 to a baseband signal using the carrier frequency and the carrier frequency Band pass filter using a phase shifter 236 for shifting the phase of the second carrier frequency transmitted from the male oscillator 225 by 90 ° and a second carrier frequency shifted in phase by the phase shifter 236. Frequency downconverter 237 for downconverting the second intermediate frequency band signal transmitted from 234 to the baseband signal and baseband signals output from downconverters 235 and 237 are respectively filtered to remove noise. Low pass filters 238 and 239 are passed to the baseband processor 210.

Here, the frequency down converter 237 and the phase shifter 236 demodulate a signal transmitted by being modulated from the base station.

The transmission processor 240 may control the low pass filters 241 and 242 to remove noise by filtering the baseband signal transmitted from the baseband processor 210 and the control frequency transmitted from the control frequency oscillator 212. A frequency upconverter 243 for up-converting the baseband signal transmitted from the low pass filter 241 to a transmission intermediate frequency band, and a phase of 90 ° for shifting the phase of the control frequency transmitted from the control frequency oscillator 212. A frequency upconverter for up-converting the baseband signal transmitted from the lowpass filter 242 to the transmission intermediate frequency band by using the phase shifter 244 and the control frequency shifted by the phase shifter 244. 245, an adder 246 for adding the output signals of the frequency up-converters 243 and 245, a band pass filter 247 for filtering the output signal of the adder 246 to remove noise, Using a first carrier wave transmitted from the transmission frequency oscillator 224 consists of a frequency up-converter 248 for up-converting an output signal of the band pass filter 247, the mobile station transmits a high-frequency band.

Here, the frequency up-converters 243 and 245, the phase shifter 244 and the adder 246 are modulation functions for performing a function of modulating a baseband signal for transmission to a base station.

The operation of the carrier transceiver of the present invention having the structure as described above will be described in detail with reference to FIGS. 3A and 3B.

3A and 3B are explanatory diagrams of an automatic tracking and adjustment process of a carrier frequency difference of a carrier transceiver according to the present invention, and the signal spectrums of points indicated by a, b, c, d, e and f of FIG. According to the present invention, a frequency difference is controlled.

First, in order to facilitate explanation, the symbol written in each figure is demonstrated.

WRXRF is the center frequency of the received high frequency signal of the mobile station and is equal to the center frequency of the transmitted high frequency signal of the base station.

WRXRF is the center frequency of the transmission high frequency signal of the mobile station and is equal to the center frequency of the reception high frequency signal of the base station.

WRFLO is the center frequency of the first carrier frequency generated from the carrier frequency oscillator 224 and should ideally have a frequency exactly the same as the first carrier frequency of the base station.

However, as described above, in general, the first carrier frequency of the mobile station has a frequency difference between β and the first carrier frequency of the base station. Here, β may have both positive, negative, or '0' values.

WRXIF1 and WRXIF2 are the primary and secondary receive intermediate frequencies of the mobile station, respectively, and WTXIF is the transmission frequency of the mobile station.

The carrier frequency WIFLO2 generated from the carrier frequency oscillator 225 should have the same frequency as the second carrier frequency of the base station at the mobile station second carrier frequency in the ideal case, but has a frequency difference of α as described above. However, α may have both positive, negative, or '0' values.

The control frequency WIFLO1 generated from the control frequency oscillator 212 is the center frequency of the control frequency and is a control frequency when both α and β are zero.

The following describes the operation of the carrier transceiver of the present invention using the above symbols.

The mobile station receives the high frequency signal from the base station and transmits the high frequency signal to the receiving processor 230, which converts the high frequency signal into the primary intermediate frequency band through the frequency down converter 231. In this case, as described above, since the first carrier frequency of the mobile station has a frequency difference by β from the base station, the center frequency of the down-converted primary intermediate frequency signal has a difference of β from the original center frequency WRXIF1 ( 3a and 3b, b).

The high frequency signal generated in the downconversion process is removed while passing through the band pass filter 2324. The primary intermediate frequency signal is converted into a secondary intermediate frequency band signal by the frequency downconverter 233, which has the opposite sign of β included in the control frequency as shown in FIGS. 3A and 3B. The β component of the primary intermediate frequency signal is removed by the frequency component.

However, the center frequency of the secondary intermediate frequency signal becomes WRXIF2 + α having a difference by α at the normal center frequency by the opposite sign frequency component of the second carrier frequency difference included in the control frequency. The frequency difference by α is a difference component of the second carrier frequency used by the demodulation function, and is a secondary intermediate frequency in advance so that when the received signal is converted to the baseband in the demodulation function, the frequency is exactly '0'. The frequency component applied to the signal.

Therefore, as shown in d of FIGS. 3A and 3B, α, which is a difference component in the frequency downconverters 235 and 237 of the demodulation function, is canceled and canceled from α of the second carrier frequency, so that the baseband signal is exactly Has '0' as the center frequency. However, all hatched portions in the figure are unwanted high frequency signals removed by the bandpass filter and the lowpass filter.

Of course, the α and β components included in the control frequency are initially components estimated by the received signal by the frequency difference tracking unit 211 in the baseband processor 210 and then applied to the control frequency.

2, in the present invention, the first carrier frequency and the control frequency are used in common by the reception processor 230 and the transmission processor 240.

Therefore, as can be seen in Figures 3a and 3b e, if the baseband signal is upconverted to a transmission frequency signal via the frequency upconverters 243 and 245 of the modulation function, the transmission intermediate frequency signal is the original normal center. The difference is as much as α and β from the frequency WTXIF. The output signal of the modulating function is converted into a high frequency signal by the frequency up-converter 248 after passing through the band pass filter 247. In this process, β which is a difference component of the first carrier frequency included in the transmission intermediate frequency signal Is removed.

Therefore, only the α component, which is the difference component of the second carrier frequency, remains in the final transmission high frequency signal of the mobile station, which takes into account the stability of the carrier frequency generator in the design of the system so that the component can be kept within an acceptable range at the receiver of the base station. Just do it.

Furthermore, since the? Component is a difference component of the second carrier frequency having a relatively low frequency, the variation between the mobile stations can be kept small.

When all mobile stations transmit to the base station with the controlled transmission frequency as described above, the base station has a single radio frequency reception processing unit, and it is possible to receive and process the transmission frequencies of all the mobile stations without tracking them.

In conclusion, the operation of the present invention is significantly different from the conventional method, whereas the conventional method attempts to compensate for the frequency difference of the carrier frequency oscillator, whereas in the present invention, the carrier frequency oscillator is used instead of the method of compensating the frequency difference. Instead of leaving the frequency difference, the control frequency oscillator is controlled to offset the frequency difference.

Although the technical idea of the present invention has been described in detail according to the above preferred embodiment, it should be noted that the above-described embodiment is for the purpose of description and not of limitation. In addition, those skilled in the art will understand that various embodiments are possible within the scope of the technical idea of the present invention.

As described above, the present invention has the following effects.

First, by using the signal received from the base station to track the carrier frequency difference of the mobile station in the baseband, to ensure reliable communication without the need for complicated circuits or high-quality crystal oscillator for carrier synchronization in the high frequency signal processing stage can do.

Secondly, since the base station and the mobile station operate as one synchronization loop, they can automatically have the effect of similar coherent detection. That is, since the transmission frequency error of the mobile station is automatically adjusted, the base station can perform data demodulation well even through noncoherent detection.

Third, since the intermediate frequencies as well as the transmission and reception radio frequency are spaced apart from each other, the interference between the transmission and reception signals can be avoided.

Claims (7)

In the carrier transmitting and receiving device in a communication system, Frequency difference tracking and control frequency generating means for tracking the difference between the carrier frequency received from the base station and the carrier frequency transmitted to the base station by using the signal received from the base station, and generating a control frequency according to the tracked frequency difference tracking value. ; Carrier frequency generating means for generating first and second carrier frequencies as reference for frequency downconversion of the signal received from the base station and frequency upconversion of the signal transmitted to the base station; Down-converting a high frequency received signal received from the base station to a baseband signal using the first and second carrier frequencies and the control frequency, and removing the carrier frequency difference between the base station and the mobile station according to the control frequency Receiving processing means for receiving a signal; And Up-converting a baseband signal for transmission to the base station to a high frequency signal using the first carrier frequency, and transmitting the upconverted high frequency signal by removing a carrier frequency difference between the base station and the mobile station according to the control frequency Transmission processing means Carrier transceiver device for automatic frequency adjustment in the communication system comprising a. The method of claim 1, The frequency difference tracking and control frequency generating means, Frequency difference tracking means for tracking a difference between a carrier frequency received from the base station and a carrier frequency transmitted to the base station using the signal received from the base station; And Control frequency generating means for generating the control frequency by receiving the frequency difference tracking value tracked by the frequency difference tracking means Carrier transceiver device for automatic frequency adjustment in the communication system comprising a. The method of claim 1, The carrier frequency generating means, Reference frequency generating means for generating a reference frequency which is a reference for generation of the first and second carrier frequencies; First frequency control means for providing a first control signal for controlling generation of the first carrier frequency in accordance with the reference frequency; First carrier frequency generating means for generating said first carrier frequency in accordance with said first control signal; Second frequency control means for providing a second control signal for controlling generation of the second carrier frequency in accordance with the reference frequency; And Second carrier frequency generating means for generating the second carrier frequency according to the second control signal Carrier transceiver device for automatic frequency adjustment in the communication system comprising a. The method of claim 1, The reception processing means, First downconverting means for downconverting a high frequency signal received from the base station into a signal of a first intermediate frequency band using the first carrier frequency; First filtering means for filtering out an output signal of the first downconverting means to remove noise; Second downconverting means for downconverting the output signal of the first filtering means into a signal of a second intermediate frequency band according to the control frequency; Second filtering means for filtering out an output signal of the second downconverting means to remove noise; Third downconverting means for downconverting the output signal of the second filtering means into a baseband signal using the second carrier frequency; First phase shifting means for shifting the phase of the second carrier frequency; Fourth downconverting means for downconverting the output signal of the second filtering means into a baseband signal in accordance with the frequency shifted by the first phase shifting means; Third filtering means for filtering the baseband signal output from the third downconverting means to remove noise; And Fourth filtering means for filtering the baseband signal output from the fourth downconverting means to remove noise Carrier transceiver device for automatic frequency adjustment in the communication system comprising a. The method of claim 4, wherein The first phase shifting means, And a phase shift of the second carrier frequency by substantially 90 [deg.]. The method according to any one of claims 1 to 5, The transmission processing means, Fifth and sixth filtering means for filtering out a baseband signal for transmission to the base station to remove noise; First up-converting means for up-converting the output signal of the fifth filtering means into a signal of a third intermediate frequency band according to the control frequency; Second phase shifting means for shifting the phase of the control frequency; Second upconverting means for upconverting the output signal of the sixth filtering means into a signal of a fourth intermediate frequency band by using the frequency shifted in phase by the second phase shifting means; Adding means for adding output signals of the first and second upconverting means; Seventh filtering means for filtering out an output signal of the adding means to remove noise; And Third up-converting means for up-converting the output signal of the seventh filtering means to a high-frequency signal using the first carrier frequency Carrier transceiver device for automatic frequency adjustment in the communication system comprising a. The method of claim 6, The second phase shifting means, And a phase shift of the control frequency substantially 90 °. A carrier transceiver apparatus for automatic frequency adjustment in a communication system.