超小型人工衛星QSAT用アンテナの研究開発 ●中島　究 宇宙機ダイナミクス研究室

内容 目的及び背景 概要 展開方法 QSATにおける配置 マッチング回路 試験結果 結論及び今後の予定 アンテナ・パターン アンテナ・ゲイン 回線設計 結論及び今後の予定 This is today’s contents. First of all, I explain background, and concept for my antennas. Next, I show the method to develop antennas, and antennas arrangement in QSAT. In result, I show antenna pattern and link budget. About antenna pattern and link budget, I will explain in results pages. Last is conclusion.

目的及び背景 目的 背景 超小型人工衛星QSATに適したアンテナの開発 超小型人工衛星開発の広がり 従来のアンテナ：高コスト，複雑，大型 In recent years, low cost and micro satellites have become popular. But, antennas used for usual satellites are very big, complex and expensive. There is need to develop the suitable antennas for micro satellites. Of course, that should be low cost and simple. In our laboratory, the 50 kg micro satellite QSAT is being developed. In my graduation thesis, I developed the low cost and simple antennas for QSAT.

概要 機構がシンプル，指向性が比較的広いモノポールアンテナ，ダイポールアンテナを利用 種類 周波数帯 [MHz] 波長 [mm] アンテナ長 衛星搭載 受信用 ¼波長モノポールアンテナ 145.80 ~ 146.00 2068 517 送信用 半波長ダイポールアンテナ 435.00 438.00 690 345 As I said, antennas must be cheap and simple for micro satellites. So, I choose simple mechanism antennas, ¼ wave length monopole antenna, and half length dipole antenna. About ¼ wave length monopole antenna, electric power is supplied at end of antenna, and about half wave length dipole antenna, power is supplied at center of antenna. QSAT use amateur radio band. So, antenna lengths become quarter and half of each wave length.

展開方法 巻尺（コンベックステープ）を利用 巻尺の復元力による展開機構の簡略化 分離前 展開 分離後 　　　　　巻尺の復元力による展開機構の簡略化 分離前 For QSAT, measurement tapes are used as antennas. Because elastic power of measurement tapes make deployment system simple. Before launch, antenna is fixed in this position. In orbit, this fixed position is released, then antenna deploy without complex mechanisms. 展開 分離後

QSATにおける配置 伸展ブームによる姿勢の安定化 下面地球方向 下面にアンテナを配置 　　　　下面地球方向 　　　　下面にアンテナを配置 QSAT have extension boom for attitude control. So, this surface always face the earth, then antennas are attached to this surface.

ダイポールアンテナの配置 まずダイポールアンテナの配置を考慮 First, I consider about half wave length antenna. If antenna is attached near to satellite, In opposite side of antenna, there are very wide region not to communicate. But, if antenna is attached far from satellite, antenna need mechanism to join to satellite. So, I decide to attach dipole antenna on the corner of satellite.

モノポールアンテナの配置 不要電波の受信を防ぐ ダイポールアンテナからの電波を考慮 Next, I consider about ¼ wave length monopole antenna. If receive antenna receive unnecessary radio wave, sometimes it is harmful to antenna’s circuit. So receiver antenna must avoid unnecessary wave. Especially , very strong radio wave come from dipole antenna. I decide to attach monopole antenna here to avoid radio wave from dipole antenna. Because, basically monopole antenna can’t receive radio wave in this direction. And this photo show QAST and antennas.

マッチング回路 マッチング回路 ： アンテナと同軸ケーブルのインピーダンスの整 合を行う マッチング回路　：　アンテナと同軸ケーブルのインピーダンスの整 　　　　　　　　　　　　 合を行う バラン　　　　　　 ：　アンテナに180度位相のずれた電流を供給する SMA コネクタ πマッチング 回路 モノポール アンテナ 受信機 同軸ケーブル 送信機 LCバラン ダイポール アンテナ SMA コネクタ

マッチング回路 ¼波長モノポールアンテナ：πマッチング回路 半波長ダイポールアンテナ：LCバラン Zo ： アンテナのインピーダンス Next, I show antenna pattern. Antenna pattern show antenna’s directivity. But, about half wave length dipole antenna, antenna pattern can not be measured. Because of defect of circuits. So, I show antenna pattern about ¼ wave length monopole antenna only. This is antenna pattern. Standard dipole antenna emit radio wave for monopole antenna. And monopole antenna and QSAT were turn around like this. Then, we measured how much radio wave monopole antenna received. Zo　：　アンテナのインピーダンス SWR ： Standing Wave Ratio，定在波比

マッチング回路 LCバランを改良 SWR ： Standing Wave Ratio，定在波比 L C1 C2 L C1 C2 Next, I show antenna pattern. Antenna pattern show antenna’s directivity. But, about half wave length dipole antenna, antenna pattern can not be measured. Because of defect of circuits. So, I show antenna pattern about ¼ wave length monopole antenna only. This is antenna pattern. Standard dipole antenna emit radio wave for monopole antenna. And monopole antenna and QSAT were turn around like this. Then, we measured how much radio wave monopole antenna received. L C1 C2 SWR ： Standing Wave Ratio，定在波比

アンテナ・パターン アンテナ・パターン測定風景 Next, I show antenna pattern. Antenna pattern show antenna’s directivity. But, about half wave length dipole antenna, antenna pattern can not be measured. Because of defect of circuits. So, I show antenna pattern about ¼ wave length monopole antenna only. This is antenna pattern. Standard dipole antenna emit radio wave for monopole antenna. And monopole antenna and QSAT were turn around like this. Then, we measured how much radio wave monopole antenna received.

アンテナ・パターン ¼波長モノポールアンテナのパターン アンテナ・パターン：アンテナの指向性を示す Next, I show antenna pattern. Antenna pattern show antenna’s directivity. But, about half wave length dipole antenna, antenna pattern can not be measured. Because of defect of circuits. So, I show antenna pattern about ¼ wave length monopole antenna only. This is antenna pattern. Standard dipole antenna emit radio wave for monopole antenna. And monopole antenna and QSAT were turn around like this. Then, we measured how much radio wave monopole antenna received. アンテナ・パターン：アンテナの指向性を示す

アンテナ・ゲイン アンテナ・ゲイン G 仮定 θ アンテナ・パターンは円形である． θ=360[deg] θ : 半値角[deg] 極大値の半分の 　　　　値(-3dB)になる角度 η : 効率 仮定 　アンテナ・パターンは円形である． 　θ=360[deg] [dB] -25.9[dB] -21.8[dB] θ [deg] From antenna pattern, antenna gain is calculated using this equation. θ is beam width. This show angle to become half value from peak in antenna pattern. And, basically antenna pattern is measured twice for one antenna. Parallel plane to antenna and normal plane to antenna. Here, I use one assumption. ¼ wave length monopole antenna’s pattern are circular form. Because, this pattern have many peak and circular form give the worst gain calculated from this equation. -25.7[dB]

回線設計(1/4波長モノポール) KUGS : Kyushu University Ground Station In link budget, we estimate if communication can be done between satellite and ground station. And margin should be higher than 0 [dB]. About monopole antenna, satellite can communicate with ground station. KUGS : Kyushu University Ground Station FSK : Frequency Shift-Keying

結論及び今後の予定 結論 ¼波長モノポールアンテナ 今後の予定 広い指向性 地上局と通信可能 巻尺をアンテナとして利用可能 半波長ダイポールアンテナのマッチグ，パターン測定 より広い電波暗室でのパターン測定 回線設計 10km程度の距離をおいた実際の通信実験 環境試験