A 1024-Element Ku-Band SATCOM Phased-Array Transmitter With 45-dBW Single-Polarization EIRP

This article presents a 1024-element Ku-band phased-array transmitter for mobile satellite communications. The array is based on eight-channel transmit (TX) SiGe beamformer chips. Dual-polarized stacked-patch antennas enable the array to synthesize linear, rotated-linear, and left- and right-hand circular polarization. The array consists of four quadrants of 256-element subarrays, each of which has 64 beamformer chips and a driver chip assembled on a printed circuit board (PCB). The array achieves an effective isotropic radiated power (EIRP) of 75 dBm per polarization (78-dBm circular polarization) and scans to ±75° in all planes. This is achieved using an antenna spacing of $\lambda $ /2 at 14.4 GHz in an equilateral triangular grid. The array also results in 30-dB cross-polarization rejection up to 60° scan angles. Measured error vector magnitude (EVM) for 50-, 100-, 200-, and 500-MBd QPSK and 8 phase-shift keying (8PSK) waveforms results in at most 1.5%rms and 2.5%rms at $P_{1\textrm {dB}}$ and $P_{\mathrm{ sat}}$ , respectively, at 14 GHz over all scan angles. Also, the adjacent channel power ratio (ACPR) was measured as −32 dB for 200- and 500-MBd QPSK and 8 phase-shift keying (8PSK) waveforms at $P_{1\textrm {dB}}$ at 14 GHz. To the authors’ knowledge, this work presents a state-of-the-art planar phased-array system with high EIRP for Ku-band satellite communication (SATCOM) mobile transmitter terminals.

I. Introduction

Mobile satellite communication (SATCOM) provides a feasible solution for broadband Internet access to underserved areas [1]. Low-Earth orbit (LEO) satellite constellations, with orbits at 800–1200 km and a latency of 30 ms, are currently being built and launched for this purpose and are expected to enter operation in 2021 and 2022. The LEO satellites have a typical rise to set times of 0.5–1 hour and need to be constantly tracked, and an active electronically scanned array (AESA) is essential for reliable operation [see Fig. 1(a)]. Also, phased arrays are promising for ground, maritime, and airborne satellite communication-on-the-move (SOTM) platforms for both LEO and geostationary Earth orbit (GEO) applications since the antenna can be pointed quickly to the satellite and can easily compensate for the platform motion [2]–[4]. Fig. 1.

(a) 1024-element dual-polarized SATCOM TX phased-array based on eight-channel beamformer chips. (b) subarray with an eight-channel Ku-band TX beamformer chip. (c) 12-layer PCB stackup.