Nonuniformly Spaced Array with the Direct Data Domain Method for 2D Angle-of-Arrival Measurement in Electronic Support Measures Application from 6 to 18 GHz

This paper introduces a 2D angle-of-arrival (AoA) estimator, which has a 6–18 GHz 7-element nonuniformly spaced array (NSA) and a Direct Data Domain- (D3-) based AoA algorithm for a 2D isotropic-element planar array (IEPA). A 2D calibration and data-transformation method is developed to convert the NSA data to the output of the IEPA, so that the NSA-measured data can be used in the D3 algorithm. Using the steering vector (SV) of the IEPA and the results derived from the D3 method, a new 2D AoA searching method is also developed, which offers frequency-independent performance defined by the probability of AoA estimation, when the required estimation accuracy and signal-to-noise ratio (SNR) are given. For the applications of electronic support measures, this paper also presents the use of precalculated SV and data-transformation matrix databases built on preselected frequency points and a 2D-angle grid that is close to uniformly distributed directions. The simulation results show that with good SNR (≥15 dB), the estimator can have 50% probability of AoA estimation with root mean square error (RMSE) less than or equal to 1° using just a few samples from the NSA. Moreover, the study focuses on the applications with low SNR by using more samples from the NSA. Results show that the estimator has 52% and 80% probabilities of AoA estimation with RMSE ≤1° and 5°, respectively, for phase- or frequency-modulated radar pulses, when the SNR is within [−10, 0] dB. The study also shows that the estimator prefers a circular-shaped planar array with a triangular interelement pattern, since it presents more symmetrical characteristics from different azimuth angles.

Antena Bikonikal Tabung untuk Aplikasi Radar Electronic Support Measures Dengan Pola Radiasi Omni-directional pada Frekuensi 2-18 GHz

Pada tulisan ini, dibahas hasil penelitian mengenai perancangan antena bikonikal tabung yang memiliki pola radiasi omni-directional yang akan digunakan pada radar Elektronic Support Measures (ESM). Antena bikonikal memiliki karakteristik bandwidth yang sangat lebar (ultra wide band) cocok digunakan pada aplikasi ESM dengan frekuensi 2–18 GHz. Bentuk pola radiasi omni-directional yang dirancang bertujuan agar pada saat ESM melakukan deteksi frekuensi radar (S-, C-, X-, dan Ku-band) dari pancaran radar yang berada di sekitarnya dapat melakukan deteksi ke segala arah. Karena kegunaan ESM sebagai detektor radar dengan sifat sebagai penerima (receiver) dibutuhkan VSWR di bawah 2,5 dengan nilai return loss di bawah -7,436. Antena bikonikal yang dirancang menggunakan dua plat tembaga yang dibentuk kerucut dengan penambahan tabung dengan pemasangan yang saling berhadapan, yang dipasang pada inner connector dan ground. Antena bikonikal dipasang mengunakan balun ¼ λ, agar matching impedansi antara antena dengan konektor 50 Ω. Plat tembaga yang digunakan dengan tebal 0,8 mm.