Enhanced scanning range of coupled oscillator arrays utilizing frequency multipliers

Abstract

-Scanning in arrays is conventionally achieved through phase shiften. Recent work has indicated that scanning can be achieved with significantly reduced complexity and cost using coupled-oscillator techniques. However, the scan range has been somewhat limited using this tecbnique. This paper describes a simple method to greatly enhance the scan range using varactor frequency doublers, which has the added advantage of simplifying the fimdamental mode oscillator design.In an effort to combine power in an efficient way the field of quasi optical power combining was born.[3]-[6] A large number of solid state oscillators can be integrated in such a way that their respective outputs coherently add in free space. The low loss properties of free space, especially at higher frequencies, along with the reliability of solid state devices make this approach particularly attractive.Extensive work, theoretical [1,7,8] and experimental [1,2] on the coupling dynamics of these discrete oscillators has already been performed. A significant breakthtough of this research was the discovery of a simple way to induce beam scanning in such an array of coupled oscillators [2]. This can be achieved by frequency &tuning the end elements of the array. Since conventional beam steering mandates the use of one phase shifter per array element, the simplicity of implementation of this new technique becomes obvious. There is no more need for a cumbersome control network to create a phase shift between successive elements. Never&heless, the phase shift and therefore the scan angle is now limited by coupled oscillator dynamics. Some concem has been expressed over these limitations. In this paper we are proposing a slight modification on the coupled oscillator beam scanning array that will drastically enhance its scanning characteristics. A small inclrease in implementation complexity is expected, but is somewhat offset by other advantages. A frequency doubler is inserted between each oscillator and its respective antenna Fig. 1. The phase shift generated between each oscillator is doubled along with the oscillator's frequency. The radiating elements are phase shifted with respect to each other, tsvice as much as the oscillators feeding them are. Clearly the scan angle is increased. Furthermore, the oscillators need to be designed, at only half of the array 0peratiOeal frequency.As was shown in [ 1,7] the theoretical phase shift At) that can be generated between successive coupled oscillators lies within -900 Sit) S900. In an array of element ~7803-27145/95/s4.000 1995 IEEE 1308

Injection signal controlled active phased arrays without mode jumps

“…Because the phase doubles when the frequency is doubled, the change in the range of the phase difference is also doubled to -π to +π. A broader scanning range than that obtained by radiating the fundamental was obtained in an experiment on multiplying the output of the oscillators with a frequency doubler and then radiating [12], and also in an experiment using active integrated antennas [13] for frequency multiplication at the same time as fundamental oscillation and the radiation of a second harmonic [14]. Another issue is the application of this technique to these antenna arrays.…”

Active phased array antenna radiating second harmonic output wave

“…However, since locking phenomena are used, the variations of the phase difference between the active antennas can be obtained only up to π. Hence, an attempt has been made to insert a multiplier between the oscillator and the antenna so that the frequency doubled output is radiated [3]. In this case, the variations of the phase difference between the antennas can be obtained up to 2π.…”

A Single-Element Beam Steering Antenna Array with 180° Scanning Range

“…However, the uniform phase progressions of these two approaches range only between -900 and 900, which means a scanning range of ±300 off broadside for an electronically scanned array with half-wavelength spacing among its radiation elements. In [11], a simple method to enhance the scanning range by means of frequency multipliers was studied.…”