KR20080083760A - Channel filtering apparatus with direct conversion for rf repeater - Google Patents

Abstract

A direct-conversion channel filtering apparatus in an RF repeater is provided to reduce the size and manufacturing cost of an RF repeater by implementing an MMIC(Microwave Monolithic Integrated Circuit), a single chip containing low pass filters, without using an IF SAW(Surface Acoustic Wave) filter. A direct-conversion channel filtering apparatus in an RF repeater is comprised of a power divider(10), a local oscillator(26), a down-conversion 90-degree phase shifter(24), two down-conversion frequency mixers(12,18), two low pass filters(14,20), an up-conversion 90-degree phase shifter(28), two up-conversion frequency mixers(16,22), and a power combiner(30). The power divider divides the power of an inputted RF signal into an I channel and a Q channel. The local oscillator generates a local oscillation signal having the same frequency as the carrier frequency of the RF signal. The down-conversion 90-degree phase shifter generates the local oscillation signal and a 90-degree phase-shifted local oscillation signal. The down-conversion frequency mixers respectively mix the local oscillation signal and the phase-shifted local oscillation signal with the power-divided RF signal and downconvert them into baseband signals. The low pass filters pass only a frequency of a desired service band among the downconverted baseband signals. The up-conversion 90-degree phase shifter generates the local oscillation signal, generated from the local oscillator, and the 90-degree phase-shifted local oscillation signal. The up-conversion frequency mixers respectively mix the local oscillation signals generated from the up-conversion 90-degree phase shifter with the baseband signals outputted from the low pass filters and upconvert them into the original RF signals. The power combiner combines the power of the RF signals mixed through the up-conversion frequency mixers.

Description

Channel Filtering Apparatus with Direct Conversion for RF Repeater}

1 is a view for explaining the concept of channel filtering in a conventional RF repeater,

2a and 2b is a channel filtering configuration of the IF method and the RF method, respectively, in the conventional RF repeater,

3 is a schematic block diagram of a channel filtering apparatus for an RF repeater according to the present invention;

4A to 4C are frequency domain graphs for describing an operation of the channel filtering apparatus illustrated in FIG. 3.

*** Explanation of symbols for the main parts of the drawing ***

10: power divider, 12, 16, 18, 22: frequency mixer,

14, 20: lowpass filter, 4, 28: 90 ° phase shifter,

26: local oscillator, 30: power synthesizer

The present invention relates to a channel filtering device for a direct conversion RF repeater, and more particularly to a channel filtering device for a direct conversion RF repeater that can be used in a mobile communication network such as CDMA, WCDMA, and the mobile Internet (WiMax).

As is well known, an RF repeater is a shaded area that amplifies the signal so that the signal from the base station can reach a shaded area such as a tunnel or underground parking lot that is difficult to reach due to a mountain, a building, or other feature. It refers to a device that serves to connect the signal from the shadow area terminal to the base station, the most common type of repeater is the RF repeater.

1 is a diagram illustrating a concept of channel filtering in a conventional RF repeater. As shown in FIG. 1, assume that service bands A, B, and C are adjacent to each other, but different services are provided by different operators. In this case, assuming that the main band is the B band, it is necessary to suppress the other band signal so that the other service band signal does not affect the B band which is the main band. The same channel filtering technique is used.

2A and 2B are diagrams illustrating channel filtering schemes of an IF scheme and an RF scheme in a conventional RF repeater, respectively. Channel filtering methods widely used in the conventional RF repeater include an IF (Intermediate Frequency) channel filtering method as shown in FIG. 2A and an RF channel filtering method as shown in FIG. 2B. First, according to the IF channel filtering method illustrated in FIG. 2A, a base station signal received through a donor antenna (not shown) is input to a low noise amplifier (LNA) through a duplexer (not shown), thereby amplifying low noise. The amplified signal is mixed with the oscillation frequency of the local oscillator in a frequency mixer and down-converted to the intermediate frequency IF. Next, the down-converted signal passes through a surface acoustic wave (SAW) filter having excellent skirt characteristics, so that only signals of a desired middle frequency band are separated. This separated signal is then mixed with the oscillation frequency of the local oscillator in the mixer, up-converted to the original RF signal, amplified by a high power amplifier and then service antenna (not shown). Is emitted through the shaded area. On the contrary, after the signal from the terminal is received by the service antenna, the signal is connected to the base station through the donor antenna through the same process as shown in FIG. 2A.

Next, according to the RF channel filtering method of FIG. 2B, since the RF frequency and the channel filtering frequency of the base station or the terminal signal are the same, a mixer as shown in FIG. 2A is not required and the configuration thereof is simple. However, this method uses RF channel filter made of dielectric, so other band suppression characteristics are inferior to surface acoustic wave filter due to the characteristics of device. have.

On the other hand, in recent years, although there are problems such as DC offset and I / Q imbalance, due to the size and cost, high frequency RF signal is directly grounded using a local oscillation signal having the same frequency as the carrier frequency. A receiver for down-conversion (also called zero IF) to a baseband signal has been proposed and installed in a mobile communication terminal.

However, the down conversion channel filtering technology is adopted only in mobile communication terminals, and thus is not applied to the RF repeater. Therefore, the size of the RF repeater increases and the manufacturing cost increases.

The present invention has been made to solve the above problems, by applying a direct conversion channel filtering device to the RF repeater to reduce the size of the RF repeater and the manufacturing cost of the direct conversion RF repeater channel filtering It is an object to provide a device.

In accordance with an aspect of the present invention, there is provided a channel filtering apparatus for an RF repeater according to an embodiment of the present invention, comprising: a power divider for distributing input RF signals to I and Q channels; A local oscillator for generating a local oscillation signal having a frequency equal to a carrier frequency of the RF signal; A 90 ° phase shifter for down conversion that generates a local oscillation signal generated by the local oscillator and a local oscillation signal shifted in phase by 90 degrees; Two down-converting frequency mixers for mixing the local oscillation signals respectively provided by the 90-degree phase shifter for the down-conversion with the power-distributed RF signal to down-convert to baseband signals; Two lowpass filters that lowpass only the frequencies of the desired service bands in the down-converted baseband signal; A 90 ° phase shifter for up-conversion generating a local oscillation signal generated by the local oscillator and a local oscillation signal shifted in phase by 90 °; Two frequency mixers and the frequency mixer for frequency-converging the local oscillation signals respectively provided by the 90-phase phase shifter for up-conversion with the baseband signals passed through the respective lowpass filters. It comprises a power synthesizer for synthesizing the power of the mixed RF signal through.

In the above configuration, the local oscillator may be made of a PLL circuit. Furthermore, the channel filtering device may be implemented as a single chip MMIC.

Hereinafter, with reference to the accompanying drawings will be described in detail with respect to the channel filtering apparatus for a direct conversion RF repeater according to a preferred embodiment of the present invention.

3 is a schematic block diagram of a channel filtering apparatus for an RF repeater according to the present invention. As shown in FIG. 3, the channel filtering apparatus of the present invention is a power divider (Power Divider) for power distribution to the I channel and the Q channel through the RF signal received through the donor antenna (not shown) after largely launched from the base station ( 10) a phase of a local oscillation signal generated by a local oscillator 26 or a local oscillator 26 that generates a predetermined local oscillation signal, that is, a local oscillation signal having a frequency equal to a carrier frequency of an RF signal. 90 ° Phase Shifter (24), 90 ° Phase Shifter (24) for down conversion to shift by 90 ° to generate local oscillation signal for Q channel and original local oscillation signal for I channel Two frequency mixers 12, 18, and each frequency mixer 12 for converting each of the signals provided by the respective power distribution RF signals into baseband signals and converting them into baseband signals. Down-converted via 18 In the band signal, the phases of the local oscillation signals generated by the two low pass filters 14 and 18 and the local oscillator 26 which pass only the frequencies of the desired service bands are shifted by 90 °. Local oscillation signals provided by the up-conversion 90 ° phase shifter 28 and the up-conversion 90 ° phase shifter 28 respectively generating local oscillation signals for the channel and the original local oscillation signal for the I-channel, respectively. Two frequency mixers 16, 22 and frequency mixer 16, which are frequency-mixed with the baseband signal passed through the lowpass filters 14, 20 of the signal to be converted to the original RF signal, i.e., up-converted. And a power combiner 30 for synthesizing the powers of the mixed RF signals through the reference numeral 22.

In the above-described configuration, the local oscillator 26 is preferably implemented with a phase locked loop (PLL) circuit. Furthermore, the channel filtering device may be implemented as a microwave monolithic integrated circuit (MMIC) consisting of a single chip.

Hereinafter, the operation of the channel filtering apparatus for the RF repeater of the direct conversion method of the present invention will be described in detail.

4A to 4C are frequency domain graphs for describing an operation of the channel filtering apparatus illustrated in FIG. 3. First, the RF signal emitted from the base station and received by the donor antenna of the RF repeater is eliminated unnecessary bands (including noise) other than the reception band by a band pass filter (not shown). Here, it is assumed that there are three service bands of A, B, and C as shown in FIG. 4A in the RF signal passed through the bandpass filter, and the band to be actually used is the B band. Next, the RF signal passing through the bandpass filter is low noise amplified by a low noise amplifier (not shown), and then is distributed to the I and Q channels through the power divider 10.

On the other hand, the local oscillator 26 generates a local oscillation signal having the same frequency as the carrier frequency of the RF signal and provides it to the 90 ° phase shifter 24 for down conversion, and the 90 ° phase shifter 24 for down conversion. Phase shifts the local oscillation signal by 90 ° so that the original local oscillation signal is supplied to the I-channel frequency mixer 12, while the 90 ° phase shifted local oscillation signal is supplied to the Q-channel frequency mixer 18. do. Next, the I-channel frequency mixer 12 and the Q-channel frequency mixer 18 respectively mix local oscillation signals provided by the 90 ° phase shifter 24 for down-conversion with the power-distributed RF signal. Conversion to the baseband signal, i.e. down conversion, and the two lowpass filters 14, 20 are again converted in the baseband signal downconverted through the respective frequency mixers 12, 18 in Figure 4b. As shown in Fig. 1, only the frequency signal of the desired service band, that is, the B band shown in solid line, is passed.

Next, the two frequency mixers 16 and 22 for up-conversion convert the B-band baseband signals extracted through the respective lowpass filters 14 and 20 into a 90 ° phase shifter for up-conversion. Frequency mixing with the local oscillation signal for the I-channel and the Q-channel provided at (28), respectively, converts to the original RF signal, that is, up-converts. Next, the up-converted RF signal is synthesized through the power synthesizer 30 to leave only the signal of the B band as shown in FIG. 4C, and then amplified by a high power amplifier (not shown), and then a service antenna (not shown). Is fired towards the terminal.

This can be summarized mathematically as follows.

라 할 때, I채널용의 다운 컨버전 주파수 합성기(12)와 그 저역통과 필터(14)를 순차적으로 거쳐 출력되는 신호와 Q채널용의 다운 컨버전 주파수 합성기(18)와 그 저역통과 필터(20)를 순차적으로 거쳐 출력되는 신호는 각각

와

가 된다.In other words, the original RF signal

The down conversion frequency synthesizer 18 for the I channel and the low pass filter 20 for the Q channel and the down-conversion frequency synthesizer 18 for outputting the signal sequentially passed through the down-conversion frequency synthesizer 12 for the I channel and the low pass filter 14. Are sequentially output signals through

Wow

Becomes

(

)가 된다.The signals output through the up-conversion frequency synthesizer 16 for the I-channel and the signals converted through the up-conversion frequency synthesizer 22 for the Q-channel are respectively. As a result, the signal finally output through the power synthesizer 30 is the same as the original RF signal.

(

)

The RF filtering channel filtering apparatus of the direct conversion method of the present invention is not limited to the above-described embodiments, and various modifications can be made within the range allowed by the technical idea of the present invention. For example, it may be implemented on the MMIC by adding DC Offset Supression or IQ Amplitude / Phase Unbalance Compensation.

According to the channel filtering device for a direct conversion RF repeater of the present invention as described above, since the IF surface acoustic wave filter is not used, it can be implemented as a single chip MMIC with a low pass filter comparable thereto. The size of the repeater can be reduced and its manufacturing costs can be reduced.

Claims (3)

A power divider for distributing input RF signals to I and Q channels; A local oscillator for generating a local oscillation signal having a frequency equal to a carrier frequency of the RF signal; A 90 ° phase shifter for down conversion that generates a local oscillation signal generated by the local oscillator and a local oscillation signal shifted in phase by 90 degrees; Two down-converting frequency mixers for mixing the local oscillation signals respectively provided by the 90-degree phase shifter for the down-conversion with the power-distributed RF signal to down-convert to baseband signals; Two lowpass filters that lowpass only the frequencies of the desired service bands in the down-converted baseband signal; A 90 ° phase shifter for up-conversion generating a local oscillation signal generated by the local oscillator and a local oscillation signal shifted in phase by 90 °; Two frequency mixers that frequency-converge the local oscillation signals provided by the 90 ° phase shifters for up-conversion with the baseband signals passed through the respective lowpass filters, and upconvert to the original RF signals; And a power synthesizer for synthesizing the power of the mixed RF signal through the frequency mixer. 2. The channel filtering apparatus of claim 1, wherein the local oscillator comprises a PLL circuit. 3. The channel filtering apparatus for RF repeater according to claim 1 or 2, comprising a single chip MMIC.

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