TW201008141A - Method for reducing inter-modulation interference and signal receiver using the same - Google Patents

Abstract

The present invention relates to a method for reducing inter-modulation interference and a signal receiver using the same. In order to suppress the inter-modulation distortion (IMD) caused by applying radio frequency (RF) signal into a down conversion circuit, the intermediate frequency (IF) amplifier typically arranged behind the down conversion circuit is removed or the signal power thereof is decreased, and a radio frequency amplifier is added in front of the down conversion circuit or the signal power thereof is increased.

Description

201008141 IX. Description of the Invention: [Technical Field] The present invention relates to an RF signal receiving apparatus, and more particularly to a method for reducing intermodulation interference in a satellite signal receiving apparatus and a signal receiving apparatus to which the same is applied. 5 [Prior Art] In the footsteps of digital TV globalization, in order to enable satellite receivers around the world to receive multi-channel digital TV signals, system operators should try to use the adjacent commercial satellites to transmit more wide-band satellite frequency signals. The receiving terminal 10 collects the satellite signal by the satellite antenna set in the outdoor, and then uses the radio frequency (RF) circuit corresponding to the satellite signal in the low noise block-downconvertor (LNB) and its down-conversion processing. The multi-band intermediate frequency (IF) signal is sent to the digital set-top box (STB) in each user terminal. 15 The first figure shows a circuit structure of a frequency reducer 1 for processing broadband satellite signals. 'When receiving satellite electromagnetic wave signals SAv and SAh in various polarization directions, first use several low noise amplifiers (LNAs). 111, 112 sequentially amplify the signal, and after diverging into two RF transmission paths, a filter 121, 122, 123, 124 is arranged on each RF path to divide the RF signal filtering of each polarization 2 into two. Radio frequency signals RFvl, RFv2, RFM, RFh2 of different bandwidths, wherein the vertical and horizontal polarization signals of the same bandwidth are combined with a local oscillator (LO) by a mixer 131, 132, 133, 134 141, 142 of the frequency reduction processing, the subsequent stages are respectively processed by the first intermediate frequency amplifiers 151, 152, 153, 154, band pass filtering 201008141 161, 162, 163, 164 for different bandwidth and polarization The direction intermediate frequency signals IFvl, IFv2, IFhl, IFh2 can be digitally switched and re-amplified by the two-digit selection switch 17 and the second intermediate frequency amplifiers 181, 182, 183, 184 to enable multiple receiving users to pass through the respective output terminals. 191, 192, 5 1 93, 194 can choose to receive four vertical and horizontal polarization direction intermediate frequency signals IFvl, IFv2, IFhl, IFh2, once corresponding to the digital receiver box of each receiving user, that is, demodulated and digital processing based The baseband signal, such that each digital TV channel program provided by the system operator can be output for viewing by the receiving user. 10 However, in a processing circuit similar to the above-mentioned high-frequency signal, an additional carrier signal which is fed to the effective bandwidth of the signal through the circuit environment, such as electric oscillating or high-frequency radiation, is often faced, so that a new signal is generated in the actually required signal band. The modulation interference of the non-expected signal type causes an alternating modulation signal like the frequency of the new signal', especially in the mixed 15 wave processing process using a plurality of local oscillators 141, 142, each local oscillator H1 5 142 The vibration frequency signal is directly transmitted to the second mixer 13 134 or 132, 133 corresponding to another local oscillator 142 or 141 through a DC line transmission path, a microstrip line oscillation of the filter line, or radiation conduction. After the mixing process, the mixed signal outputted by each of the 13, 132, 133, and 134 outputs includes the above-mentioned interactive modulation interference signal, although the band pass filters ΐ6, 162, 163, and 164 of the subsequent stage can be suppressed. The sideband signal outside the effective frequency range, but the intermodulation noise after the interactive mixing is due to the partial modulation frequency directly appearing in the effective frequency range and cannot be filtered or waved. In addition, therefore the same as the actual signal after a respective IF amplifier stage 15 152,153,154,18 Bu Bu 182 201 008 141 183, 184 more to the enlargement processing, and seriously affect the quality of the output terminal of the baseband signal. Even if the circuit designer repeatedly detects the calibration process, it will try to eliminate the electrical transmission path that each local oscillator may cause interference, so that it is placed in the top 5 isolation position, but the actual high-frequency electromagnetic wave radiation transmission is ubiquitous, even adjacent. In the circuit processing environment, as long as the oscillation energy of the source of the alternating modulation source cannot be completely absorbed, it is reflected back to the original oscillation circuit and turned into a radiation source, so that the alternating modulation wave phenomenon formed by the radiation conduction has become such a drop. Interference signals that cannot be avoided in the frequency circuit. 10 SUMMARY OF THE INVENTION Accordingly, the main object of the present invention is to provide a method for reducing intermodulation interference and a signal receiver to be applied, which can save the circuit space structure and manufacturing cost and effectively reduce the frequency reduction process. 15 interactive modulation interference. In order to achieve the foregoing disclosure, the method for reducing the intermodulation interference provided by the present invention is to suppress the intermodulation distortion generated by the radio frequency signal after passing through a down-conversion circuit, and is determined by the output of the downstream stage and the output end of the down-conversion circuit. The intermodulation noise power in the frequency band and the IF signal frequency range, when the intermodulation noise power is too large 2, the ratio between the IF signal power and the noise power is reduced, the signal between the output terminal and the down-converting circuit The power is reduced and the signal power before the down circuit is increased. The signal receiver provided by the present invention is characterized in that: the frequency reduction circuit and the at least one RF signal receiving end have a plurality of low noise 201008141 amplifiers connected in series with each other, and between the plurality of intermediate frequency signal outputs A switching circuit is selected, wherein the frequency signals of the plurality of different frequency bands generated by the frequency reducing circuit respectively input at least one filter and then input to the selection switching circuit. 5 [Embodiment] Hereinafter, a preferred embodiment will be described with reference to a plurality of drawings for further explaining the components and functions of the present invention, wherein the brief description of each of the drawings is as follows: The functional block diagram of the circuit 10 of the signal receiver provided by the embodiment; the second figure is the circuit structure of the signal receiver provided by the above preferred embodiment; the fourth figure is the output of the signal receiver provided by the above preferred embodiment. The frequency response characteristic curve of the measured signal; 15 The material drawing is a flow chart of the operation of reducing the intermodulation noise in the signal receiver provided by the above preferred embodiment. Referring to the second and third figures, a signal receiver 2' for receiving the electromagnetic 20-wave signals in the vertical and horizontal polarization directions is provided for the general satellite antenna in the preferred embodiment of the present invention. Receiving a processing satellite signal and transmitting it to a digital set-top box of the user terminal, the signal receiver 2 includes a frequency amplifying circuit 20, a high-frequency filtering circuit 3〇, a frequency reducing circuit 40, and an intermediate frequency filtering circuit. 5〇 and a selection switching circuit, wherein: the high frequency amplifying circuit 20 has two receiving ends 21, 22 and a plurality of low noise amplifiers 23 or 24 electrically connected to each receiving terminal 2010 or 21 or 22, when vertical and horizontal The satellite signals SAv and SAh in the direction of the polarized electromagnetic wave are respectively transmitted by the feed antennas to the receiving ends 21 and 22, and the high-frequency electromagnetic waves in the respective polarization directions are successively composed of a plurality of low noise amplifiers 23 or 24 5 . The signal is successively subjected to multi-stage linear amplification conversion processing, which can avoid the nonlinear conversion of the single-stage high-power amplification processing and fall into the operational characteristics of the amplifier, and even generate the influence of the RF signal feedback oscillation. The signal receiver 2 if the signal is enlarged to increase the required power can be enlarged to the high frequency circuit 20 adds the number of cascaded amplifiers 23 and 24 produce linear amplification function. The high frequency filter circuit 30 has two signal splitters 3 32 (splitter) and two filters 33, 35 or 34, 36' electrically connected to the respective splitters 31 or 32. Each of the splitters 31 or 32 will be amplified. The subsequent satellite signals SAv or SAh are divided into two transmission lines. The filters 33, 35 or 34, 36 are filtering functions of two different band pass bands, so that the satellite signals 15 SAv or SAh of each polarization type can be used. The area is divided into two kinds of RF signals RFvl, RFV2 ❹ or RFhl, RFh2 of different bandwidths. Of course, if the frequency of the RF signal is to be further subdivided, the output lines of the remote branches 31 and 32 can be set based on the line matching. The extension, and then the bandpass filter with a predetermined bandwidth on each output line can generate more frequency band RF signals. The down-converting circuit 4 has one of the mixers 41, 42, 43, 44 electrically connected to each of the filters 33, 34, 35, 36, and the mixers 41, 42, 43, 44 electrically connected to the local oscillators 45, 46, one of the inputs corresponding to the RF signal RFvl, RFM or RFv2 RFh2 of different polarization directions but the same bandwidth § 玄 mixer 41, 44 or 42, 43 That is, 201008141 is operated by the same local oscillator 45 or 46 at the same aliasing frequency, and the RF signals RFW, RFhl or RFv2, RFh2 of different polarization types but of the same bandwidth are still down-converted to the same lower frequency. Wide distribution, the intermediate frequency signal formed after frequency reduction not only has a mixing range of multiple frequency superpositions and a mixed frequency modulation frequency band of 5 high-order spectral waves, and since each local vibration 45 is privately set to two kinds of polarized electromagnetic waves Between the processing lines, the vibration rate signal is transmitted to the second mixer 42 or 43 corresponding to the local oscillator 46 or 45 through the DC line transmission path, the microstrip line oscillation of the filter line or the radiation conduction mode. 4 Bu 44 and - with the mixed wave processing, so that each mixer ίο The actual mixing range of 41 42 43 44 produces an alternating modulation interference signal entrained by the effective intermediate frequency signal in the frequency response characteristic measured in the fourth figure. The intermediate frequency filtering circuit 50 has a plurality of bandpass choppers. 5 Bu 52, 53 and 54' respectively receive the order of each of the mixers 4, 42, 43, 44 of the down-converting circuit 40 by their respective input groups 511, 521, 53 and 54丨15. The frequency 'produces corresponding polarization by the money processing _ and the frequency range IF IFv 1, IFh 丨 ' coffee, leg output to each output group 512, 522, 532, 542 ' to exclude unwanted mixed frequency bands In the case of the above-mentioned intermodulation _, the high-frequency amplifier I has amplified the RF signal power before the mixing to the μ-frequency signal IF compared to the mutually acceptable signal-to-noise ratio .

The output terminal group 512=H=the money exchange devices 51, 52, 522, 532, 542 of the selection switching circuit 6〇I 53 and 54 can be received from each user at each of the output terminals 20 201008141 601 602 603, 604 The switching command of the terminal, and then the internal digital control circuit determines the type of the signal frequency band to be output to each of the output terminals 601, 602, 603, and 604, and the selection switching circuit 6Q provided in this embodiment is a group of four inputs. For example, the matrix switch 6b 62 5 of the output of the human two is controlled by two switching transistors as required for the circuit layout. Of course, the present invention does not limit the type of the matrix switch used. In order to enable all of the intermediate frequency signals IFv1, IFv2, IFhl, and IFh2 to be selectively switched from the outputs, 602, 603, and 604, the received users are received by the corresponding receiving users, and each of the matrix switches 61, 62 receives one of them. The IFW, IFV2, and IFh IFh2 are separately shunted by the IF filter circuit 50 to be switched for each switch, so that the output terminals 601, 602, 603, and 604 of the selection switching circuit 60 are respectively set before the switches 601, 602, 603, and 604. An intermediate frequency amplifier 63 64, 65, 66, can compensate the nickname power reduced by the shunt current to ensure the signal power quality output by the signal receiver 2, I5 of course, the noise power entrained in the sustaining signal can be Within the maximum power range allowed, the higher the power gain values of the intermediate frequency amplifiers 63, 64, 65, 66, the higher the power can be supplied to the receiving user. Therefore, the signal receiver 2 provided by the present invention maintains the signal 20 power required by each of the output terminals 601, 602, 603, and 604 by the high frequency amplifying circuit 20 because the RF signal has been completed in the front stage of the down converter circuit 40. The power amplification 'can eliminate the additional IF amplifier after the down-conversion process, avoiding the intermodulation noise generated by the down-conversion process can not be filtered by the filter and amplified together with the actual signal; further, due to the signal amplification processing Before the RF signal is divided by the high frequency filter circuit 30, it is not necessary to separately add amplifying frequency to each of the 201008141 frequency band signals after frequency division to achieve the required signal power, that is, the high frequency filter circuit 30. Each single amplifier added in the front stage can omit each amplifier required to be set in each frequency band of the latter stage, effectively saving the number of amplifiers to increase circuit space and reduce cost. 5 In addition, since the signal is still subjected to various circuit processing after the frequency reduction circuit 40, the output signals 601, 602, 603, and 604 are outputted to receive the required intermediate frequency signal of the user terminal, and the design is in addition to the present invention. The signal receiver 2 is provided to remove the intermediate frequency amplifier corresponding to the intermediate frequency filter circuit 50 to avoid the intermodulation noise, and the circuit frequency power of the subsequent intermediate frequency signal 10 is further considered in the circuit processing. The attenuation situation, therefore, can be performed as shown in the fifth figure. The following steps are used to effectively balance the signal output power and maintain low intermodulation noise: 1. Measure each IF signal IFvl, IFv2, IFhl, IFh2 The 15 signal powers outputted by the output terminals 601, 602, 603, and 604 of the switching circuit 60 are selected; 2. the intermodulation noise corresponding to the frequency band of the intermediate frequency signal is measured at the output terminals 601, 602, 603, and 604. Power, the ratio of the intermediate frequency signal power to the intermodulation noise power is defined as a minimum signal to noise ratio (S/N ratio); 3. When the output terminals 601, 602, 603, 604 measure the signal to noise ratio When it is less than the minimum signal noise ratio, the selection is selected The amplification power gain values of the intermediate frequency amplifiers 63, 64, 65, and 66 of the switching circuit 6 are reduced, so that the intermodulation noise power measured by the output terminals 601, 602, 603, and 604 is reduced; 4. The RF signal of each polarization direction in the amplifying circuit 20 is 11 20 201008141. The amplification power gain value of at least one of the low noise amplifiers 23, 24 is increased or added to the low noise amplifiers 23, 24 to ensure the outputs. 6 (Π, 602, 603, 604 required output intermediate frequency signal iFv IFv2

The signal-to-noise ratio of IFhl and IFh2 is greater than or equal to the minimum signal-to-noise ratio of 0. Only the above-mentioned ones are only preferred embodiments of the present invention, so that the application specification and the scope of the patent application are The structural change is intended to be included in the patent of the present invention.

12 201008141 [Simplified description of the drawings] The first figure is a circuit diagram of a conventional signal receiving system; the second figure is a circuit function block diagram of the signal receiver provided by the preferred embodiment of the present invention; The circuit diagram of the signal receiver provided by the example; the fourth diagram is a frequency response characteristic diagram of the signal measured by the output of the signal receiver provided by the above preferred embodiment; the fifth figure is provided by the above preferred embodiment A flow chart for reducing the noise of each other in the signal receiver.

13 201008141 [Main component symbol description] 2 signal receiver 20 high frequency amplifier circuit 21, 22 receiving end

23, 24 low noise amplifier 31, 32 splitter 40 frequency reduction circuit 30 high frequency filter circuit 33, 34, 35, 36 filter 4 42 42, 43 44 mixer 45, 46 local oscillator 50 IF filter Circuit

10 15 51, 52, 53, 54 bandpass filters 511, 521, 531, 541 input set 512, 522, 532, 542 output set 60 select switching circuit 601, 602, 603, 604 output 61, 62 matrix Switch 63, 64, 65, 66 intermediate frequency amplifier SAv, SAh satellite signal RFv Bu RFM, RFv2, RFh2 RF signal IFvl, IFM, IFv2, IFh2 IF signal

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Claims (1)

201008141 X. Patent application scope: 1. A method for reducing inter-modulation interference to suppress the occurrence of intermodulation noise after radio frequency (RF) signal is generated through a down conversion circuit. The inter-modulation distortion (IMD) includes the following steps: 5 measuring the intermediate frequency signal (IF) intermediate frequency signal outputted by the frequency-receiving signal after being processed by the frequency-reduction circuit Power; measure the intermodulation noise power in the frequency range of the intermediate frequency signal at the output end, and define a ratio of the intermediate frequency signal power to the intermodulation noise power to define a minimum signal noise ratio (S/N ratio) And; when the signal-to-noise ratio measured by the output is less than the minimum signal-to-noise ratio, the signal power between the output and the down-converting circuit is reduced, and the RF signal power before the down-converting circuit is increased, To maintain the signal-to-noise ratio of the output is greater than or equal to the minimum signal-to-noise ratio. ® 15 2 · The method of reducing the intermodulation interference according to the scope of claim 1 'filters the filters used to filter the signals generated by the down-converter circuit to remove the electrical connections. • 3 _Reducing the method of intermodulation interference according to item 2 of the patent application scope. The above intermediate frequency signal is passed through a selection switching circuit 20 before the output terminal. The selection switching circuit receives the control instruction input by the output terminal. After the 'multiple frequency band signals generated by the down-converted mixing of the down-converting circuit can be switched and outputted by the output terminal. 4. The method for reducing the intermodulation interference according to the second or third aspect of the patent application is to reduce the gain of the amplifier by electrically connecting the output to the amplifier. 5. The method of reducing the intermodulation interference according to the first or second aspect of the patent application is to add at least one amplifier before the down-conversion circuit. 6. According to the method of claim 5, the method for reducing the intermodulation interference, 5, the at least one amplifier added before the down-conversion circuit is a low noise amplifier (LNA), which operates on the amplifier Operate as a linear conversion area of the characteristic curve. 7. The method of reducing intermodulation interference according to claim 6 of the patent application scope, wherein the at least one amplifier is connected in series with a plurality of low noise amplifiers having the same amplification power rate. 8 - a signal receiver for reducing an intermodulation interference method according to the scope of claim 1 includes: at least one receiving end for receiving an RF signal; and a frequency amplifying circuit having a plurality of mutually connected The amplifier has a 15-gauge amplification 1 § electrically connected to the at least-receiving end, and the second amplifier is electrically connected to the down-converting circuit; ° 20 is a plurality of mixers and is separately charged from each of the mixers The first filter and a local oscillator (local osciUator, LO), in the frequency down circuit, the first filter is electrically connected to the second amplification: 'the radio frequency is divided into When the different frequency bands are used, the first intermediate frequency signal of each of the mixers and the corresponding local mixed frequency band is used; "the Bevon number and the plurality of second filters receive the first intermediate frequency signals respectively. Each of the mixers is connected to be filtered by the second filter to output a second intermediate frequency signal of the phase 16 201008141; and the third filter is electrically connected to the second filter. To pick up 'end can turn out u' has more Each of the outputs 'outputs the frequency signal of all the frequency bands. Do not output 5 (four) 9. According to the application of the scope of claim 8 the city receives crying == more electrically connected with each of the output terminals The 10th is 'respectively corresponding to the amplification of each of the second intermediate frequency signals. The frequency relaxation is based on the signal receiver described in item 8 of the patent application scope, and the second=receiving end' separate secret electromagnetic wave types w 1 1. According to the shot, the signal mentioned in the item i is received as 'the frequency amplifier circuit has a plurality of sets of mutually connected amplifiers, and each of the receiving ends is electrically connected to the first amplifier, each The radio frequency sfl of the polarized electromagnetic wave type is electrically connected to a plurality of 15 first-filters, and the RF signals of different polarized electromagnetic wave types are filtered to have the same plurality of frequency bands. 1 2 . According to the signal receiving device described in Item 1 of the patent application scope, each of the mixers electrically connected to the first filter of the same filtering frequency band is electrically connected to the local oscillator. . One a signal receiver for reducing intermodulation interference generated by a down-converter circuit, the down-conversion circuit and a plurality of intermediate-frequency signal outputs of the signal receiver having a selection switching circuit, the majority of the frequency-reduction circuit generating The intermediate frequency signals of all frequency bands can be selected for outputting the IF signals of all frequency bands at each output end, and are characterized by: 17 201008141 a plurality of filters, each of the filters having an input terminal group and an output terminal group electrically connected to the frequency reduction circuit and the selection switching circuit, respectively, so that the frequency signal is directly input in a plurality of different frequency bands generated by the frequency reduction circuit At least one of the filters. 18