A high-throughput satellite shared channel C / I performance improvement design method

Abstract

The application discloses a high-throughput satellite shared downlink C / I performance improvement design method. In the process of beam downlink signal forwarding, channel filtering performance influences C / I performance in the beam coverage area. The biggest determining factor of the channel filtering performance is the filtering performance after frequency conversion. The filtering performance is improved by performing multi-channel filtering processing on the signal after frequency conversion and then performing interval channel signal combining processing. The application can obtain better channel out-of-band suppression performance, and the adjacent channel suppression performance is obviously improved compared with the wideband filtering mode. According to the frequency planning of 12% protection bandwidth, the suppression ability of the adjacent edge frequency of the adjacent channel is generally above 15 dB, and the filtering performance of the center frequency point can reach about 30 dB. Considering the inter-channel suppression performance of the output filter, the system can obtain good channel C / I performance.

Description

Technical Field

[0001] This invention relates to a design method for improving the C / I performance of a shared line amplifier for high-throughput satellites, belonging to the field of satellite communication technology. Background Technology

[0002] High-throughput satellites (HTS) employ multi-beam and frequency reuse technologies. Under the same spectrum resources, the overall throughput of a satellite is several times that of a traditional fixed communication satellite (FSS). They can operate in any frequency band, and the throughput varies depending on the allocated spectrum and the number of frequency reuses.

[0003] HTS satellite frequency reuse technology introduces several problems. When two or more beams use the same frequency band, due to non-zero antenna beam roll-off and sidelobes, the same frequency emitted by two or more beams will be received in the same coverage area, resulting in co-channel interference between beams. Furthermore, the modulation signal spectrum in the HTS satellite transponder channel is broadband; if the power suppression capability of adjacent transponder channels is weak, it can also lead to inter-beam interference. Point-beam technology can also cause inter-beam interference and reduce efficiency. Increasing the distance between beams can reduce interference, but this reduces frequency reuse, impacting overall throughput.

[0004] As the capacity requirements of HTS satellites continue to increase, the number of beams in HTS satellites is also increasing, as is the corresponding number of satellite transponder channels. Consequently, the HTS satellite payload transponder system is limited by factors such as weight, structure, and power consumption. The HTS satellite forward transponder (gateway station to user link) needs to be designed in a manner that uses a shared power amplifier (usually a traveling wave tube amplifier, or BR) for adjacent channels to support more beam channels. The signal output from the frequency converter is filtered separately according to the number of beams in the shared BR before entering the BR. The filter has poor out-of-band rejection performance for single-beam channels and no rejection for adjacent channels, resulting in poor C / I performance of the channels. Summary of the Invention

[0005] The technical problem solved by this invention is to overcome the shortcomings of the prior art and propose a design method for improving the C / I performance of a shared line amplifier for high-throughput satellites. By rearranging the channel combination relationship of the payload frequency reuse, channel-based filtering is achieved for each channel, thereby improving the filtering performance of the channel and realizing the payload C / I improvement.

[0006] The technical solution of this invention is:

[0007] A design method for improving the C / I performance of a shared line amplifier in a high-throughput satellite, wherein the satellite payload forward beam downlink channel includes at least three frequency channels, and two or more frequency channels share a line amplifier. The analysis of the factors affecting the C / I performance within the beam coverage area shows that the biggest influencing factor during the forwarding of the downlink signal is the filtering performance after frequency conversion.

[0008] The effective load frequency reuse channel combination relationship after frequency conversion and multi-channel filtering is rearranged, and the signal combining of the interval channels is processed. Then, the power amplifier is shared to improve the filtering performance after frequency conversion and improve the C / I performance in the beam coverage area.

[0009] Preferably, the signal combining process of the interval channels is performed, and the number of the interval channels is determined according to the frequency planning, with one or more intervals.

[0010] Preferably, the signals in the selected merged interval channel are signals from different sources, that is, the two signals do not come from the same broadband signal.

[0011] Preferably, the two signals in the combined path are selected as channel signals with different polarizations.

[0012] Preferably, if the filtering performance of the channel filter decreases, but the protection bandwidth remains unchanged, the in-band ripple performance and delay ripple performance of the channel will be improved.

[0013] Preferably, if the filtering performance of the channel filter decreases and the in-band ripple performance and delay ripple performance of the channel have excessive margin, the protection bandwidth between channels is reduced to obtain channel bandwidth utilization benefits.

[0014] Preferably, the circuit for forwarding the downlink beam signal is as follows: the beam input inverter converts the frequency to the user's frequency; the power divider receives the output signal from the inverter, splits it into several signals, and inputs each signal into a channel filter for filtering; the output signals of the channel filters are combined, and the generated combined signals are output to power amplifiers; each power amplifier amplifies the signal and then performs single-frequency channel output filtering through an output duplexer to obtain the beam required by the user.

[0015] Preferably, the channel filter is a narrowband filter.

[0016] The advantages of this invention compared to the prior art are:

[0017] (1) The present invention achieves good channel near-band suppression performance. Through the design of the shared line amplifier form of the spaced channel combination, each transponder channel can obtain the benefits of the channel filter and output multiplexer on the out-of-band suppression performance of the channel, thereby obtaining better out-of-band suppression performance, reducing interference to adjacent channels, and obviously improving the effective payload C / I performance.

[0018] (2) This invention can improve spectrum utilization efficiency. The C / I performance of HTS satellite payload is determined by the performance of transponder and antenna. When the channel suppression performance of transponder has little impact on the overall C / I performance of payload, the channel protection bandwidth can be reduced to obtain a wider channel frequency bandwidth and improve frequency utilization.

[0019] (3) This invention has good scalability and universality. It is applicable to the design of HTS satellite transponder channels with two or more channels sharing a line amplifier. It can be used as a reference for communication systems with similar design requirements. Attached Figure Description

[0020] Various other advantages and benefits will become apparent to those skilled in the art upon reading the following detailed description of preferred embodiments. The accompanying drawings are for illustrative purposes only and are not intended to limit the invention. Furthermore, the same reference numerals denote the same parts throughout the drawings. In the drawings:

[0021] Figure 1 A schematic diagram of the downlink transmission coverage area for HTS satellite user beam 28;

[0022] Figure 2 A schematic diagram of frequency planning for 28 users of the HTS satellite;

[0023] Figure 3 A schematic diagram of a typical HTS satellite payload (forward) transponder system.

[0024] Figure 4 This is a schematic diagram of frequency planning for a typical HTS satellite forward transponder.

[0025] Figure 5 A block diagram for a common row layout;

[0026] Figure 6 A schematic diagram of the signal flow design for a shared pass amplifier for adjacent channels;

[0027] Figure 7 This is a block diagram illustrating the improved design of the common line amplifier to enhance the suppression performance of adjacent channels in an embodiment of the present invention.

[0028] Figure 8 This is a schematic diagram of the signal flow design for a shared horizontal amplifier in a spaced channel according to an embodiment of the present invention. Detailed Implementation

[0029] Exemplary embodiments of the present disclosure will now be described in more detail with reference to the accompanying drawings. While exemplary embodiments of the present disclosure are shown in the drawings, it should be understood that the present disclosure may be implemented in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided to enable a more thorough understanding of the present disclosure and to fully convey the scope of the disclosure to those skilled in the art. It should be noted that, unless otherwise specified, the embodiments and features described herein can be combined with each other. The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0030] The HTS satellite payload C / I performance reflects the mutual interference between user beams in the downlink transmitted signal of the high-throughput satellite forward payload. Figure 1 This is a schematic diagram of the downlink transmission beam coverage area for HTS satellite user 28, along with a diagram of the corresponding frequency planning. Figure 2 .from Figure 1 , Figure 2 As can be seen, the high-throughput satellite user beam is formed by multiplexing five frequencies within the coverage area. For antenna beams, the actual designed antenna coverage area is larger than the required coverage area. This can cause signals from one beam to fall into the coverage areas of other beams. When two coverage areas have the same frequency, co-channel interference occurs. For example, the user beams corresponding to the frequencies of the three gateway stations F1, F6, and F11 are the same frequency. When the signal from the F1 beam falls into the F5 or F11 beam area, interference occurs. For transponder channels, the frequency components of adjacent channels within the same channel can interfere with neighboring channels. Therefore, for high-throughput satellites, the C / I performance within the beam coverage area is determined by both antenna beam performance and transponder channel suppression performance. Considering both factors, C / I can be expressed as:

[0031] C / I=C / (I 波束 +I 邻近通道 (1)

[0032] In the formula, I 波束 Interference introduced by antenna beam overlap, I 邻近通道 Interference introduced by the power of the adjacent channel of the transponder. It can be seen from the equation that when I... 邻近通道 When reduced, the C / I performance of the user beam can be improved. In the HTS satellite payload transponder channel system, I... 邻近通道 The performance is mainly determined by the filtering performance of the transmission frequency band.

[0033] A typical HTS satellite payload (forward) transponder system schematic diagram is shown below. Figure 3As shown, the channel filtering performance of the transponder system is mainly determined by the filters after the frequency converter and the power amplifier. Each user beam after the power amplifier needs to be filtered, which needs to ensure low loss while suppressing power amplifier harmonics and noise in the uplink band of the gateway station. The ability to suppress interference signals from adjacent channels is relatively low. Therefore, the ability of the transponder system to suppress interference from adjacent channels mainly depends on the performance of the filters after the frequency converter.

[0034] This is described using a typical HTS satellite forward transponder frequency planning and design. Figure 4 A schematic diagram of a 16-beam, 4-color multiplexed multi-beam frequency planning is given. The gateway station contains 16 frequency signals with 8 frequency channels and 2 polarizations. The F1-F4 and F5-F8 frequencies of each polarization are converted to the user's F1-F4 frequencies through two different local oscillators, LO1 and LO2, which includes a total of 16 signals with 2 polarizations and 4 frequencies.

[0035] Due to limitations in weight and volume bearing capacity, high-throughput satellites typically have dozens to hundreds of beams. It's impractical to configure a power amplifier (usually a line amplifier in satellite communication) for each beam; therefore, multiple beams need to share a common line amplifier in the design. The core difference in the design approach for sharing line amplifiers lies in the design of the frequency converter filter module. A typical shared line amplifier design uses... Figure 5 The design follows the structural model shown, with the filter performing broadband filtering based on the number of beams shared by the horizontal amplifier. This design, employing a broadband filter approach, achieves good in-band ripple performance and time delay variation performance. However, the filter exhibits poor out-of-band suppression for single-beam channels, with no suppression of adjacent channels, resulting in poor C / I performance for the channels. Figure 4 The frequency planning method for this scheme will be explained in detail below:

[0036] When designing a system where every two channels share a pass-through amplifier, the conventional design approach is to use a pass-through amplifier configuration where adjacent channels share the same amplifier, such as... Figure 6 As shown, the design utilizes a shared horizontal amplifier for channels F1+F2 and F3+F4. Taking the shared F1 and F2 channels as an example, channels F1 and F2 are the same local oscillator frequency converter channel. After frequency conversion, they undergo channelization filtering (F1+F2) before entering the same horizontal amplifier. After the horizontal amplifier, a duplexer is used for single-frequency channel output filtering, forming two beams. The signal flow diagram is shown below. Figure 5As shown, the user beams are polarized into R and L, with each polarization including four beams from F1 to F4, totaling eight user beams. Filtering is performed separately for adjacent channels using a shared line amplifier, specifically filtering the four combined channels at frequencies F1+F2 and F3+F4 before entering the line amplifier. This approach simplifies the RF link structure before the line amplifier and reduces the number of filters. However, a drawback is that channel filtering suppression between F1 and F2 frequencies relies solely on the output duplexer's filtering capability. Between F2 and F3 frequencies, a filter that simultaneously filters both F1 and F2 results in a wider filter bandwidth, leading to poor suppression performance for the F3 frequency channel. Based on current multiplexer performance levels, the edge suppression performance of adjacent channels typically only reaches 6–9 dB.

[0037] To address the drawbacks of sharing a horizontally coupled amplifier (LAB) for adjacent channels and improve inter-channel isolation performance, this invention proposes a high-throughput satellite shared LAB performance enhancement design method. This method employs a shared LAB design where each channel is individually filtered and then combined into a single LAB, specifically using the F1+F3 and F2+F4 channels as examples. The core design features of this invention include:

[0038] 1) The combined filtering method is designed using the idea of ​​combining the two channels of the combined channel. The number of channels between the two shared channels of the combined channel can be one or more.

[0039] 2) The combined channel signals must be combined using the heterogeneous channel combining method.

[0040] The reason for these two design considerations is that, for the design of channel filters, using an interleaved approach allows for a larger transition bandwidth between filter channels, facilitating filter implementation. On the other hand, if adjacent channels share a horizontal amplifier configuration, and the F1 and F2 channels from the same input source are filtered and then combined separately, sufficient guard bandwidth is required between channels to ensure the filter's in-band characteristics meet requirements. Furthermore, the filtering effect (channel isolation performance) between F1 and F2 is almost completely lost after combining. Therefore, the combining channels must be selected from signals with different sources; that is, the two signals combined before filtering do not originate from the same wideband signal. The design scheme using this method selects two signals from two different polarized channels for combining, avoiding the spectral aliasing caused by combining signals from the same source after filtering. Simultaneously, the required inter-channel guard band for each channel filter is reduced (thus improving the utilization of spectrum resources), achieving better in-band characteristics while ensuring necessary out-of-band suppression.

[0041] The design principle block diagram of the filter combining scheme designed according to the present invention is shown below. Figure 6As shown, the signal output by the frequency converter is split and filtered according to the frequency of each channel, and then combined according to the interval channel. The combined signals are combined according to the frequency points of different polarizations. The combined signals are then sent to the horizontal amplifier. Figure 7 The shared line amplifier design shown is relatively complex, with each beam equipped with a narrowband filter. This design, due to its narrowband filter configuration, achieves better out-of-band suppression performance, with significantly improved adjacent channel suppression compared to wideband filtering. Based on a 12% guard bandwidth frequency plan, the suppression capability of adjacent sidebands in adjacent channels is generally above 15dB, and the filtering performance at the center frequency can reach around 30dB. Considering the inter-channel suppression performance of the output filter, the system achieves excellent channel C / I performance.

[0042] by Figure 4 The frequency planning method for this scheme will be explained in detail below:

[0043] See the signal flow diagram for the shared pass amplifier design of the interval channels. Figure 8 The same method is used. Figure 4 The frequency planning is explained below. The user beams are polarized R and L, with each polarization including four beams (F1 to F4), totaling eight user beams. The design employs a filtering and combination method where two channels, separated by one channel, share a horizontal amplifier. Specifically, the four combined channels at frequencies F1+F3 and F2+F4 are filtered before entering the horizontal amplifier. After frequency conversion, the four channels of each polarization are filtered separately, resulting in eight signal channels (F1 to F4) corresponding to the L and R polarizations. To avoid spectral aliasing of signals from the same source, signals from different polarizations are combined: F1(R)+F3(L), ​​F2(R)+F4(L), F1(L)+F3(R), and F2(L)+F4(R). Signals combined according to this combination are then amplified by the shared horizontal amplifier. Using non-same-source signals for combining ensures good channel filtering characteristics and prevents spectral aliasing after combining.

[0044] The number of channels in the spaced channels can be one or more depending on the frequency planning, and the number of channels sharing a line amplifier can be two or more, with the channels originating from different sources. The shared line amplifier method for spaced channels leverages the excellent filtering performance of the narrowband filter after the inverter for adjacent channels. This allows the channel to benefit from the combined suppression performance of the high-end and low-end filters of adjacent channels, resulting in good adjacent channel suppression performance and improved C / I performance of the load system. Furthermore, the channel filters before the line amplifier generally tolerate higher insertion loss, allowing the use of higher-order filters. The out-of-band suppression performance of the channel filters is significantly better than that of the output stage. Combining the suppression performance of the two filter stages, this design method can achieve a suppression performance better than 17–23 dB near the two adjacent channels.

[0045] Through this design scheme, in some designs, the improved out-of-band rejection performance of the transponder significantly enhances the performance of the I-adjacent channels in the payload. Considering the impact of the transponder's I-adjacent channels on the system's C / I performance, when the out-of-band rejection performance of the payload is excessive, the filter's requirements for inter-channel filtering performance can be reduced, yielding two potential benefits:

[0046] (1) When the suppression performance of the channel filter decreases, if the protection bandwidth remains unchanged, the in-band ripple performance and delay ripple performance of the channel will be improved.

[0047] (2) When the suppression performance of the channel filter decreases, if the in-band ripple performance and delay ripple performance of the channel have excessive margin, the protection bandwidth between channels can be reduced, such as from 12% to 10%, thereby gaining 2% channel bandwidth utilization benefit.

[0048] Therefore, when designing a system, the efficiency of frequency resource utilization can be systematically considered based on the design results. The performance trade-off between out-of-band suppression and bandwidth utilization can be comprehensively considered, and the in-band performance, C / I performance, and channel utilization efficiency can be integrated to obtain the maximum system benefits.

[0049] The embodiments described above are merely preferred embodiments of the present invention. Ordinary variations and substitutions made by those skilled in the art within the scope of the technical solution of the present invention should be included within the protection scope of the present invention.

Claims

1. A design method for improving the C / I performance of a shared horizontal amplifier in a high-throughput satellite, wherein the downlink channel of the satellite payload forward beam includes at least three frequency channels, and two or more frequency channels share a horizontal amplifier, characterized in that... include: Analysis of the factors affecting C / I performance within the beam coverage area shows that the most significant factor during the forwarding of downlink signals from the beam is the filtering performance after frequency conversion. The frequency reuse channel combination relationship of the effective load after frequency conversion and multi-channel filtering is rearranged, and the signal combining of the interval channels is processed and then the power amplifier is shared to improve the filtering performance after frequency conversion and improve the C / I performance in the beam coverage area.

2. The design method for improving the C / I performance of a shared row amplifier for high-throughput satellites according to claim 1, characterized in that, The signal combining process of the interval channels is performed, and the number of the interval channels is determined according to the frequency planning, with one or more intervals.

3. A design method for improving the C / I performance of a high-throughput satellite shared line amplifier according to claim 1 or 2, characterized in that, The signals in the selected merged channel are signals from different sources, meaning the two signals do not come from the same broadband signal.

4. The design method for improving the C / I performance of a shared row amplifier for high-throughput satellites according to claim 3, characterized in that, The two signals in the combined path are selected as channel signals with different polarizations.

5. The design method for improving the C / I performance of a shared row amplifier for high-throughput satellites according to claim 1, characterized in that, If the filtering performance of the channel filter decreases, but the protection bandwidth remains unchanged, the in-band ripple performance and delay ripple performance of the channel will be improved.

6. The design method for improving the C / I performance of a shared row amplifier for high-throughput satellites according to claim 1, characterized in that, If the filtering performance of the channel filter decreases and the in-band ripple performance and delay ripple performance of the channel have excessive margin, the protection bandwidth between channels can be reduced to obtain channel bandwidth utilization benefits.

7. The design method for improving the C / I performance of a shared row amplifier for high-throughput satellites according to claim 1, characterized in that, The circuit for forwarding the downlink signal of the beam is as follows: the beam input inverter converts the frequency to the user's frequency point; the power divider receives the output signal of the inverter, splits it into several signals and inputs them into a channel filter for filtering; the output signals of the channel filters are combined, and the generated combined signals are output to the power amplifiers; after the power amplifiers amplify the signals, they are filtered by the output duplexer for single-frequency channel output to obtain the beam required by the user.

8. The design method for improving the C / I performance of a shared line amplifier for high-throughput satellites according to claim 7, characterized in that, The channel filter is a narrowband filter.

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