Phase noise in mutually synchronized oscillator systems is analyzed for arbitrary coupling and injection-locking topologies, neglecting amplitude noise, and amplitude modulation (AM) to phase modulation (PM) conversion. When the coupling phase is chosen properly (depending on the oscillator model), the near-carrier phase noise is reduced to 1/N that of a single oscillator, provided the coupling network is reciprocal. This is proved In general, and illustrated with specific cases of globally coupled and nearest-neighbor coupled oscillator chains. A slight noise degradation is found for unilaterally coupled (nonreciprocal) chains. The 1/N reduction for reciprocal coupling applies over nearly the entire range of free-running frequency distributions required for beam-scanning, and is verified experimentally using a linear chain of coupled GaAs MESFET voltage-controlled oscillators (VCOs) operating at X-band. The effect of a nonoptimum coupling phase on the phase noise of the system is also studied. As the coupling phase deviates from the optimum value, the phase noise increases significantly near the locking range edge for noise offset frequency near the carrier.

Phase noise in coupled oscillators: theory and experiment

Applications of millimeter-wave radar, imaging, and communication technology requires cost-effective implementation of intelligent scanning antenna systems Injection-locking and phase-locked-loop (PLL) techniques can be used to achieve synchronous operation of a number of antenna array elements, and allow for the manipulation of the phase distribution without additional phase-shifting circuitry, suggesting a potential for low-cost beam-scanning systems This paper describes a number of techniques, with an assessment of some remaining technical challenges for practical implementation

Injection- and phase-locking techniques for beam control [antenna arrays]

Active integrated antennas (AIAs) provide a new paradigm for designing modern microwave and millimeter-wave architecture with desirable features such as compactness, light weight, low cost, low profile, minimum power consumption, and multiple functionality. This paper reviews recent research and development related to this emerging technology with emphasis on its applications in high-efficiency radio-frequency (RF) front-end, millimeter-wave power combining, beam steering, and retrodirective arrays, as well as wireless sensors. Optical controlling techniques for AIA's are also described.

Progress in active integrated antennas and their applications

Scanning oscillator techniques previously developed for transmitter applications have been successfully applied to the receive mode. Scanning is achieved through frequency detuning in a coupled set of local oscillators. The design of a five element receiving array is presented, demonstrating a 25/spl deg/ scan range. The array consists of a local oscillator array, mixers, an antenna array and an IF summer. The local oscillator array is composed of five varactor tuned FET VCOs which are designed to work at 8.6 GHz. An injection-locking technique is described for low-phase noise applications.

Coupled-oscillator scanning technique for receiver applications

The analysis and experimental results of an antenna array using injection locked coupled oscillators with self-tuning of oscillator free-running frequencies are presented. With the use of coupled type-II phase locked loops for tuning oscillator free-running frequencies and an external injection signal for stabilizing the array operating frequency, this antenna array can steer its beam through a single control voltage and hold its output frequency at the injection signal frequency in operation. In addition, its beam-pointing error arising from phase errors in coupled oscillators can be reduced and the array works well over a certain frequency band. Phase dynamics and stability are studied and experimentally verified. Experimental results of a three-element injection locked coupled oscillator array show that its uniform phase progression ranges between -16deg and 52deg , and the phase errors are less than 5deg at 2.7 GHz. The operation bandwidth is shown from 2.68-2.72 GHz. By loading the injection locked coupled oscillator array with rectangular patch antennas, the beam-steering radiation characteristics are measured at various control voltages.

A Beam-Steering Antenna Array Using Injection Locked Coupled Oscillators With Self-Tuning of Oscillator Free-Running Frequencies

An active antenna array with optical input and beam scanning capability was developed. The phase shift between antenna elements is controlled by means of unilateral injection locking. The reference signal for injection locking is launched into an optical fiber by a multiquantum-well InGaAs-InGaAsP distributed feedback laser. The RF signal is recovered by a photodetector at the other end of the link and fed to the RF circuit. Experimental results are presented and discussed. >

Tak Kit Tong

Papers

An active phased array with optical input and beam-scanning capability