KR100964748B1 - Interference surpress system front end of base station - Google Patents

Abstract

The present invention improves the quality of the main received signal so as not to go through an up / down converter for converting a carrier RF signal into an intermediate frequency signal, and prevents the carrier RF signal from being affected by interference and spurious noise due to intermodulation. It is intended to provide the ISS front end of the base station to minimize interference and spurious noise.

The technical configuration of the present invention is a plurality of antennas, the carrier RF signal is received through the plurality of antennas, and pass or stop a frequency signal of a predetermined band of the carrier RF signal, the interference signal except the pass or rejected frequency band And a plurality of ISS filter units including an ISS (Interference Surpress System) filter module to remove ripple, an A / D converter for converting analog signals output from the plurality of ISS filter units into digital signals, and a spatial diver to the digital signals. A receiver comprising a DSP (Digital Signal Process) for signal processing by applying the city method; Interfering signal passing or blocking a frequency band of a predetermined band of the carrier RF signals to be output to the next base station, except the frequency band passed or blocked And a plurality of ISS filter units having an ISS filter module for removing ripples, said ISS filter And a transmitter comprising a drive amplifier and a high power amplifier for driving and power amplifying the output signal of the unit, and an antenna for outputting the amplified carrier RF signal to a next base station.

Base Station, Front End, Front-End, ISS Filter Unit, Interference Suppression

Description

IS front end of base station {INTERFERENCE SURPRESS SYSTEM FRONT END OF BASE STATION}

The present invention relates to an ISS front end of a base station, which can output high quality transmit and receive signals without going through an up / down converter, and can convert RF received signals directly to digital signals, thereby moving 3G and 4G. The present invention relates to an ISS front end of a base station suitable for applying Soft-Defined Radio (SDR) technology to a communication system.

In general, a base station is a wireless communication facility that connects a network and a terminal for a wireless communication service, and a base station that connects a mobile communication access network such as CDMA, GSM, WCDMA and a mobile phone is representative.

Recently, 3G (Generation) and 4G services with transmission speeds capable of transmitting and receiving video have expanded their service contents, and thus, the importance of the base station's signal correction role has increased in networks such as WCDMA and WIBRO. Trends will also be required in upcoming 4G systems.

One of the main components of the base station is called the front end of the base station to receive or send a desired signal, and the role of the front end affects the performance of the base station in the next stage.

Therefore, in the mobile communication network, a diversity method is applied to increase communication efficiency, and in the future, the technology of soft-defined radio (SDR) is applied to a base station due to the development of digital signal processing (DSP) and data conversion technology. Efforts are being made.

In addition, the subscriber's signal received by the base station is transmitted from the subscriber's terminal to reflect a plurality of obstacles and terrain, etc. to form a plurality of signal paths. Delay signal is detected, and the strongest signal is selected and transmitted to the network, which is called a multipath control or diversity technology.

The above-mentioned diversity refers to various radio paths through which signals are transmitted, and is widely used as a methodology for solving fading. For example, when two base stations are provided in a base station, a path for receiving radio waves It is possible to correct this fading phenomenon by two, and in this case, since the reception path of one signal is arbitrarily made, the term diversity can be used.

That is, a method of reducing fading effects by comparing the difference between two received signals or extracting only an appropriate signal by receiving the signal transmission paths spatially, temporally, and frequencyly is called diversity.

Representatively, DMB antennas for vehicles are frequently fading because they watch TV while the vehicle is moving. In this case, two antennas are provided on both sides of the rear glass of the vehicle to eliminate ghosting caused by fading. .

The above-mentioned diversity is mainly a major problem in a mobile communication network, and in general, diversity is space diversity, frequency diversity, time diversity, and cross polarization. Diversity).

Here, spatial diversity is a method of receiving signals after dropping two receiving antennas at a predetermined distance, and a method of synthesizing signals inputted by the two antennas uses one of the following methods.

That is, after receiving the same signal with two antennas, a selective method of selecting only the larger signal of the two signals, an equal gain method of combining the two signals with the same gain, and a signal noise of the two signals One of the methods of comparing the rates and placing the importance on the signal having the good SNR (Maximal Rate) is used.

By combining the signals from the two antennas through the above method, the fading problem can be solved. This synthesis is not usually synthesized at the RF analog stage, but instead is performed through a separate RF stage (DSP: Digital Signal Processing). Process) are synthesized in the stage.

This spatial diversity is used more frequently in the base station than the mobile station terminal in that way, when looking at the base station, three antennas are usually seen in one sector, which has one transmitting antenna and two receiving antennas (for diversity).

On the other hand, frequency diversity is a method of transmitting the same communication information on a plurality of frequencies in order to prevent fading occurring during the transmission and reception of a signal, using a property that has a different reception characteristic for each frequency A method of preventing fading by selecting a good received signal or combining different signals.

For example, if multiple signals are sent from one area to another, each signal may have different reception characteristics if the signals are sent to different frequencies. To do this, the frequency bandwidth should be used widely.

Accordingly, when several signals share a wide frequency band instead of using different frequencies, each signal has an effect of having a wide bandwidth, which is called frequency diversity.

In order to reduce the degradation of transmission quality in the mobile communication path, the above-mentioned time diversity is a good transmission quality by resynthesizing these received signals at the receiving side when transmitting the same signal several times. It is a technique to get.

That is, the signal reflected due to multipath fading has a longer propagation path than the original signal, so that the signal arrives at the receiving end with a somewhat delay time. The method of separating to reduce the fading effect is called time diversity.

For example, CDMA uses a rake receiver to take advantage of this time diversity, which is a device that independently separates and demodulates received echoes with a time delay. Since multipath fading can be canceled, CDMA can provide excellent performance in urban areas with many reflectors such as buildings.

Among these various diversity methods, the spatial diversity method using two receiving antennas can obtain the efficiency of the communication network of about 2 dB to 8 dB. For more information about diversity and fading, refer to the reference "RF MICROELECTRONICS" by B. Refer to Razabi, Chapter 4, Prentice Hall (1998), and "CDMA wireless technology" by Lee Sang-keun, Bang Hyo-chang, Chapter 2, Sehwa Publishing Co., Ltd. (2001), and a detailed description thereof will be omitted.

On the other hand, the above-described software-defined radio (SDR) is a technology that changes the way the radio base station and the terminal supports the radio frequency (RF) to the hardware in the form of software, that is, one in a wireless communication environment of multi-mode, multi-band, multi-environment As a wireless communication technology for economically providing a service regardless of a place and a time by a terminal of a terminal, a wireless device and a service can be provided by operation of software.

In other words, when the SDR module is installed in a mobile terminal such as a mobile phone, a personal digital assistant (PDA) or a notebook computer, it is possible to simultaneously support different frequency bands and two or more systems in one terminal. It is a technology that can provide a new communication method for various wireless networks, various wireless communication methods, different frequency bands, and high-speed data communication in the fourth generation communication.

Furthermore, in the 3G or 4G WCDMA and WIBRO networks, new demands and demands on the contents of the communication as well as the quantity of the communication are expected to continue to develop, thus satisfying the corresponding communication equipment by hardware. Since there is a large rise in unit prices, the need for SDR is increasing.

When the SDR method is applied to the ICS Repeater (Interference Cancellation System Repeater), which is being actively developed recently, the SDR method is applied by applying digital signal processing (DSP) and data conversion. It can be upgraded to meet the quantity and contents of the communication according to the demand and demand of the market, and research is reported that it can reduce power consumption, size, configuration complexity, and price by about one fifth, especially when applied to base stations. .

The main components of the above-described base station include a base station controller for controlling signal processing of the base station, a power amplifier (PA) for amplifying the transmission signal of the base station, and a combination of signals transmitted from the output amplifier to the transmission antenna. There are a combiner (combiner), a filter for blocking unnecessary frequencies other than the frequency used for service, and an antenna for radiating a transmitted signal to the air and detecting a received signal.

1 is a block diagram schematically illustrating a front end to which spatial diversity is applied to a typical WCDMA base station. As shown in the figure, spatial diversity is applied to the receiving end 110 of the base station front end 100 and is provided with two antennas 111a and 111b.

The diversity signals received through the two antennas 111a and 111b spaced at regular intervals are respectively a band pass filter (BPF) and a low noise amplifier (LNA). Low Noise Amplifier (115a, 115b) filters the noise generated during the propagation process and amplifies the signal.

The amplified first and second received signals are analog signals and are input to an analog / digital converter (ADC) 117 to convert them into digital signals. In this process, one of the above-described spatial diversity methods is applied, and the first and second reception signals are combined and input as a main RX signal.

Thus, the signal converted into the digital signal in the A / D converter 117 is input to the DSP 119 for digital signal processing, and then goes to the SDR stage.

Meanwhile, the transmitter 130 amplifies a transmission signal to be radiated through the antenna 137 through a driving amplifier 131 and a high power amplifier 133, and a band pass filter BPF. , 135).

Therefore, the TX signal of the transmitter 130 is radiated into the space in the form of a high output RF carrier.

However, the diversity reception signal received by the receiver 110 may be difficult to convert into a digital signal while satisfying the Skirt, Isolaiton, and Spurious characteristics of the bandpass filters 113a and 113b. Follow.

Therefore, converting an RF signal into an intermediate frequency (IF) signal using a down converter circuit (not shown) and converting the intermediate frequency signal into a digital signal should be included.

When the above-described conversion to the intermediate frequency signal is completed, the analog main received signal is converted into a digital signal and subjected to digital signal processing.

On the other hand, in the transmission signal, the signal passed through the down converter is again converted into an intermediate frequency signal by using an up converter (not shown) and input to the driving amplifier 131 and the high power amplifier 133.

References to this are described in "DSP Bring Base Station SDR Reality", by A. McCann and B. Brannon, 50p-56p, RF Design (Sep, 2004), and the detailed description thereof will be omitted.

However, in the base station front end according to the prior art, the up / down converter used in the process of converting the RF carrier signal to the IF signal and the process of converting the IF signal to the RF carrier has a high cost of the device, resulting in high overall unit cost, By using the up / down converter device, there is a problem such as interference caused by IM (InterModulation).

The present invention has been made to solve the above problems, and an object of the present invention is to provide an ISS front end of a base station that improves the quality of a main received signal so as not to go through an up / down converter for converting a carrier RF signal into an intermediate frequency signal. do.

Another object of the present invention is to provide an ISS front end of a base station that suppresses interference and spurious noise as much as possible so that a carrier RF signal is not affected by interference and spurious noise caused by intermodulation.

Another object of the present invention is to apply an ISS filter unit having excellent skirting and isolation characteristics to the front end of the base station, thereby enabling the base station's ISS to be adapted to WCDMA, WIBRO's 3G and 4G communication systems with increased data capacity and speed. The purpose is to provide a front end.

In order to achieve the above object, the present invention receives a plurality of antennas, a carrier RF signal through the plurality of antennas, passes or blocks a frequency signal of a predetermined band among the carrier RF signals, and passes or stops the frequency. A plurality of ISS filter units having an interference surpressing system (ISS) filter module for removing interference signals and bands except bands, and an A / D converter for converting analog signals outputted from the plurality of ISS filter units into digital signals; A receiver comprising a DSP (Digital Signal Process) for signal processing by applying a spatial diversity method to a digital signal; Pass or stop a frequency signal of a predetermined band of the carrier RF signal to be output to the next base station, Multiple ISS with ISS filter module to eliminate interfering signals and ripple except frequency bands And a transmission stage including a filter unit, a driving amplifier for driving and power amplifying an output signal of the ISS filter unit, a high power amplifier, and an antenna for outputting an amplified carrier RF signal to a next base station.

The ISS filter unit may further include a switch LNA module that inputs or outputs at intervals such that the carrier RF signal is separated within the same frequency band.

In addition, the ISS filter unit is characterized in that it comprises a filter consisting of a plurality of dielectric cavity resonator and one metal cavity resonator, in order to suppress the unwanted wave below a certain level.

As described above, the present invention having the configuration as described above eliminates the conversion process by deleting the up / down converter for converting the received signal to the intermediate frequency at the front end of the base station, thereby increasing the speed of signal transmission and at the same time up / down The volume and cost of the device can be reduced due to the elimination of down converters, providing a high quality signal that enables the application of SDR to the base station, reducing the base station's power consumption, size, configuration complexity and price by about one fifth. It can make such an effect.

 The present invention eliminates an up / down converter for converting a carrier RF signal to an intermediate frequency (IF), and by inserting an ISS filter unit according to the present invention, a receiver can transmit a signal to SDR without interference noise caused by down-converting. The transmitter may radiate a high output signal without reducing the output due to up-converting. The ISS filter unit may include a plurality of low noise amplifiers, a band pass filter, and a compensation circuit to purify a received signal or a signal to be transmitted. It can produce a good signal.

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

2 is a diagram schematically illustrating a front end to which a spatial diversity and an ISS filter unit are applied to a base station according to the present invention. The ISS front end 1 of the base station according to the present invention is provided in the ISS (Interference Surpress System) filter units 13a and 13b through two antennas 11a and 11b provided by applying spatial diversity to the receiving end 10. Receive a signal.

The ISS filter units 13a and 13b described above are designed to be used in high power base stations by combining a plurality of BPFs and low noise amplifiers (LNAs) to ensure sufficient skirting, isolation and gain.

The analog first and second received signals passing through the ISS filter units 13a and 13b are converted into digital signals by the A / D converters ADC 17, and the spatial diversity method is applied to the DSP 19. It goes to the next stage without down converting.

Meanwhile, the transmission signal is output as a high quality transmission signal by passing through the ISS filter unit 39 so that the driving amplifiers DA and 31 and the high power amplifiers HPA and 33 are not required without the intermediate frequency being converted into a carrier RF signal. It is transmitted to the antenna 37 and is radiated to the air with a clean signal of high power.

The structure and characteristics of the above-described ISS filter units 13a, 13b, and 39 refer to Patent Application No. 10-2008-0016311 filed by the present applicant, and detailed description thereof will be omitted.

3 is a diagram illustrating an example of the ISS filter unit A applied to FIG. 2. As shown in Figure 3, the ISS filter module (ISS-FM) is equipped with a plurality of LNA and BPF to increase the insertion loss and ripple characteristics to reduce the ripple of the ISS filter module (ISS-FM) to less than 2 dB. It is done so.

That is, the ISS filter unit means the ISS filter module (ISS-FM) in the example of FIG. 3.

In addition, the compensation circuit is configured to apply a band stop filter (hereinafter referred to as a BSP) to stop a frequency band in which ripple exists, and compensate for ripple or include a directional filter to provide a transmission frequency band. By separating and combining the reception frequency bands, a frequency band in which ripple exists can be compensated.

4 is a diagram illustrating another example of the ISS filter unit applied to FIG. 2. As shown in FIG. 4, the ISS filter unit B applied to FIG. 2 includes a switching LNA module and an ISS filter module (ISS-FM).

That is, the ISS filter unit B means that the switching LNA module and the ISS filter are included in another example of FIG. 4.

Here, the switching LNA module generates a time interval between transmission signals by using a circulator and a diode, so that the switching LNA module can be distinguished between the transmission signals and maintain the skirt characteristics and isolation characteristics.

The reason is that the ISS filter module (ISS-FM) filters the main characteristics such as isolation, skirt characteristics, insertion loss, etc. to be compensated or not lost, and thus the ISS filter module (ISS-FM) is used. If so, the switching LNA module is applied to replace the duplexer.

The ISS filter unit B according to the above-described embodiment refers to Patent Application No. 10-2008-0020797 filed by the present applicant, and detailed description thereof will be omitted.

FIG. 5 schematically illustrates another embodiment of the ISS filter unit applied to FIG. 2. As shown in the figure, the filter provided in the ISS filter units (A, B) according to the present invention can be formed as shown in FIG.

Referring to (a) of FIG. 5, one filter is formed by combining a plurality of resonators in series. All five resonators are formed of a dielectric cavity resonator. Referring to FIG. The four resonators are metal cavity resonators and the remaining four resonators are formed of a dielectric cavity resonator.

Here, in the case of FIG. 5B, the spurious characteristic can be greatly improved without significantly damaging the insertion loss. In this case, the spurious characteristic means unnecessary harmonics generated in addition to the desired frequency of the radio transmitter. It refers to signal components such as low harmonics.

In addition, spurious copying or unnecessary copying of unwanted harmonics and low-harmonic signal components into the space is called a spurious copy and is limited to a certain limit or less because it interferes with other communication.

Therefore, a metal cavity resonator made of metal both outside and inside of the resonator and a dielectric cavity resonator formed of a metal outside and inside of a dielectric are connected in series to improve spurious characteristics, and a compensation circuit is not required in series. Ripple is adjustable below 2dB.

However, when strict ripple characteristics are required, it is desirable to connect a compensation circuit.

FIG. 6 is a graph illustrating an output of the ISS filter unit applied to FIG. 2. As shown in the figure, FIG. 6 (a) shows the output of the ISS filter unit before the compensation circuit is applied, and FIG. 6 (b) shows the output of the ISS filter unit after the compensation circuit is applied. will be.

The ISS filter unit according to FIG. 6A uses a dielectric filter having a 900 MHz frequency band and a pass band of 25 MHz, and a low noise amplifier has a low noise figure (NF) and a gain of about 10 to 20 dB. This inexpensive device was used.

Here, the ISS filter unit according to FIG. 6 shows the skirt characteristics, isolation, gain, and return loss, all of which are suitable for high power repeaters, but the amplitude at the center frequency of 881 MHz is 29.295 dB, and the amplitude at 894 MHz is 23.739 dB. It can be seen that more than about 6 dB of ripple has occurred, and a compensation circuit is required to compensate for the ripple.

In the ISS filter unit of FIG. 6B, 33.752 dB is output at a center frequency of 881.5 MHz, 30.621 dB is output at 894 MHz, and about 3 dB of ripple is generated. The ripple is compensated by about 3 dB through a compensation circuit. It can be seen that. To further improve the ripple characteristics, the compensation circuit may be readjusted or a plurality of compensation circuits may be applied.

FIG. 7 is a graph illustrating an output of the ISS filter unit applied to FIG. 5. As shown in the figure, (a) of FIG. 7 is a case where the filter (a) of FIG. 5 is applied, and (b) of FIG. 7 shows the output frequency when the filter (b) of FIG. 5 is applied.

Here, the output graph of the filter formed only by a plurality of DR cavity resonators shows interference signals such as harmonics and low harmonics other than the desired band, so that spurious characteristics are not good, but the output of the filter formed by connecting a metal cavity resonator in series The graph shows that spurious characteristics are improved by removing interference signals such as harmonics and low harmonics other than the desired band.

In the above described exemplary embodiments of the present invention by way of example, the scope of the present invention is not limited only to this specific embodiment, and those skilled in the art within the scope described in the claims of the present invention Changes may be made as appropriate.

1 is a schematic illustration of a front end with spatial diversity applied to a base station according to the prior art;

2 is a schematic illustration of a front end with spatial diversity and an ISS filter unit applied to a base station in accordance with the present invention;

3 shows an example of an ISS filter unit applied to FIG. 2;

4 shows another example of an ISS filter unit applied to FIG. 2;

5 schematically illustrates another embodiment of an ISS filter unit applied in FIG. 2.

Figure 6 is a graph showing the measurement of the output of the ISS filter unit applied in FIG.

Figure 7 is a graph showing the measurement of the output of the ISS filter unit applied in FIG.

<Brief description of reference numerals for the main parts of the drawings>

1: ISS front end of base station

10: receiving end 11a, 11b, 37: antenna

13a, 13b, 39: ISS filter unit 17: A / D converter

19: DSP 30: transmitter

31: drive amplifier 33: high power amplifier

Claims (3)

A plurality of antennas, an ISS for receiving a carrier RF signal through the plurality of antennas, passing or blocking a frequency signal of a predetermined band among the carrier RF signals, and removing interference signals and ripples except for the frequency bands passed or stopped ( Interference Surpress System) A plurality of ISS filter units including a filter module, an A / D converter for converting analog signals output from the plurality of ISS filter units into digital signals, and signal processing by applying a spatial diversity method to the digital signals. A receiver including a digital signal process (DSP); A plurality of ISS filter units having an ISS filter module for passing or blocking a frequency signal of a predetermined band of the carrier RF signal to be output to the next base station, and to remove interference signals and ripples except the pass or blocked frequency band, the ISS filter And a transmitting stage including a driving amplifier and a high power amplifier for driving and power amplifying an output signal of the unit, and an antenna for outputting the amplified carrier RF signal to a next base station. The ISS filter module, A plurality of filters connected in series and two or more in series so as to pass and stop a frequency signal of a predetermined band; The ISS front end of the base station is provided with a compensation circuit comprising a; Low Noise Amplifier inserted between the plurality of filters to compensate for the insertion loss generated according to the stop band in the filter The method according to claim 1, The ISS filter unit Switch LNA module for inputting or outputting at intervals so that the carrier RF signal is separated within the same frequency band The ISS front end of the base station further comprises. The method according to claim 1 or 2, And the ISS filter unit includes a filter consisting of a plurality of dielectric cavity resonators and one metal cavity resonator to suppress unwanted waves below a predetermined level.

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