Hiromasa Nakaguro

Fast Measurement Technique for Phased Array Calibration

A novel measurement method is proposed in order to measure the active electric fields of the individual antenna elements in a phased array antenna. Fast and accurate measurements can be realized by the proposed method because the electric fields of multiple elements can be obtained simultaneously and no phase measurements are required. Hence, it can be easily applied to the on-board diagnostics and re-calibration in the operating phased array antenna systems. In the first step with this method, the phases of multiple antenna elements are successively shifted with the specified phase intervals while the array power variations are measured. Next, the measured power variation is expanded into a Fourier series and the terms are rearranged to put them into the form of the rotating element electric field vector (REV) method. Finally, the REV solution is used to identify the electric fields of the individual elements. Additionally, a theoretical study is carried out on the accuracy of the proposed measurement method. Simple, closed-form equations have been successfully derived for the measurement errors and the calibration accuracy is theoretically estimated. The proposed measurement method is validated with experimental results and the measurement accuracy is compared with the theoretical prediction.

An 18 GHz-band MMIC linearizer using a parallel diode with a bias feed resistance and a parallel capacitor

An 18 GHz-band MMIC linearizer using a parallel diode with a bias feed resistance and a parallel capacitor has been proposed. This linearizer has weak positive gain deviation and its gain deviation can be controlled without changing phase deviation. By applying this linearizer to an 18 GHz-band power amplifier, an improvement of IMD3 of 20 dB has been achieved.

Design of compact-size high isolation branching OMT by the mode-matching technique

This paper presents the design and performance of a compact-size branching orthomode transducer (OMT) with high isolation characteristics. The design is performed using the mode-matching applied to the circular-to-rectangular waveguide Tjunctions. The design example demonstrates the high efficiency of this design method for X-band branching OMT without septa, and realizes excellent performance. The theory is verified by a good agreement with measurements.

Beam pointing error analysis for phased array antennas with true time delay modules

The beam pointing error theory for the phased array antennas (PAA) with true-time-delay (TTD) module is proposed in closed form and is confirmed to be valid. The proposed theory easily gives the optimum subarray size, which is a unit of a TTD module, and maximum delay length of the TTD module in order to attain the desired beam pointing accuracy.

Development results of partial model of a Ka-band active phased array antenna for gigabit satellite

The high data rate and global satellite communication systems are expected to be an improvement agenda to the social and economic activities in the 21st century. The experimental high data rate (gigabit) communications satellite is required to face the technological challenges of the future growing multi-media applications. For this gigabit communications system, a Ka-band scanning spot beam antenna (SSBA) which realizes multiple beam forming is required. CRL and MELCO have been developing Ka-band active phased array antenna (APAA) for the SSBA as one of the most important and challenging technology. An APAA has been developed mainly for radar systems for many years. CRL and MELCO are investigating and developing the direct radiating APAA for communication satellites which can operate under wide frequency band in Ka-band. This paper describes the preliminary study results of the Ka-band APAA for gigabit satellite and the radiation performances of the partial experimental model of Ka-band APAA with two multiple beams to both transmit and receive signals. The partial model includes the active MMIC device such as HPA (high power amplifier), LNA (low noise amplifier) and PS (phase shifter), and multi-layered BFN (beam forming network) as key components. Performances such as radiation pattern, beam scanning performance and input-output performance have been measured. We also verified that the REV (rotating element electric-field vector) method was effective for pattern calibration.

A Large-Signal Simulation Program for Multi-Stage Power Amplifier Modules by Using a Novel Interpolation

A large-signal simulation program for multi-stage power amplifier modules by using a novel interpolation is presented. The Load-Pull and Source-Pull (LP/SP) data are provided from small number of measured LP/SP data by using a novel interpolation. The large-signal characteristics as a function of both frequency and temperature of the multi-stage amplifier module can be calculated by this simulation program. The simulation program has been applied to the design of the amplifier. It is considered that the program presented here is effective for calculating large-signal characteristics of the amplifier module.