A Multiple Unit Steerable Antenna for Short-Wave Reception*

Abstract

This paper discusses a receiving system employing sharp vertical‐plane directivity, capable of being steered to meet the varying angles at which short radio waves arrive at a receiving location. The system is the culmination of some four years effort to determine the degree to which receiving antenna directivity may be carried to increase the reliability of short‐wave transatlantic telephone circuits. The system consists of an end‐on array of antennas, of fixed directivity, whose outputs are combined in phase for the desired angle. The antenna outputs are conducted over coaxial transmission lines to the receiving building where the phasing is accomplished by means of rotatable phase shifters operating at intermediate frequency. These phase shifters, one for each antenna, are geared together, and the favored direction in the vertical plane may be steered by rotating the assembly. Several sets of these phase shifters are paralleled, each set constituting a separately steerable branch. One of these branches serves as an exploring or monitoring circuit for determining the angles at which waves are arriving. The remaining branches may then be set to receive at these angles. The several receiving branches have common automatic gain control and thus provide a diversity on an angle basis. To obtain the full benefit of the angular resolution afforded by the sharp directivity, the different transmission times, corresponding to the different angles, are equalized by audio delay networks, before combining in the final output. The experimental system, located at the Bell Telephone Laboratories' field laboratory near Holmdel, New Jersey, is described. This system comprises six rhombic antennas extending three quarters of a mile along the direction to England. Two receiving branches, in addition to a monitoring branch, are provided. Experience obtained with this system since the spring of 1935 is discussed. The benefits ascribable to it are (1) signal‐to‐noise improvement of seven to eight decibels, referred to one of the six antennas alone, and (2) a substantial quality improvement due jointly to the diversity action and the reduction of selective fading. While a three‐quarter‐mile short‐wave antenna system is an unusually long one, the steerability feature permits the employment of considerably more directivity, afforded by further increasing the length. A system two miles long is believed to be practicable and desirable. It could be expected to perform more consistently better than the three‐quarter‐mile trial installation, and should yield a signal‐to‐noise improvement of twelve to thirteen decibels referred to one rhombic antenna. With the object of predicting the performance of larger systems, the performance of the experimental system is examined in great detail and compared with theory.

Radio communication via Near Vertical Incidence Skywave propagation: an overview

“…Frequency diversity, time diversity, antenna (spatial and polarization) diversity and adaptive beamforming to suppress unwanted multipath were originally invented in the early 1930s, and implemented in intercontinental HF radio communication As measurement methods are not always described in full and differ from one researcher to the other, these values must be taken as indicative. The items with * are unverified manufacturer specifications only systems [120,121]. At the technological level of that era this required great ingenuity and considerable expenses.…”

A Corpus-Based Evaluation of Beamforming Techniques and Phase-Based Frequency Masking

“…The Delay-and-Sum (DAS) beamformer [ 11 , 12 ] is the simplest technique evaluated here. It aims to first “align” the input signals to compensate for the TDOAs at each microphone and add (although an averaging is usually carried out) the resulting “aligned” signals so as to obtain a type of “constructive interference” at its output.…”

“…To this effect, a similar minimization paradigm to MVDR's is used, but now with the restriction shown in Equation (11).…”

Βελτιστοποίηση Και Αξιολόγηση Της Επίδοσης Ασύρματων Ψηφιακών Συστημάτων Επικοινωνίας Με Πολλαπλές Κεραίες Εκπομπής Και Λήψης

“…Friis et al (1934) [24] clearly demonstrated the qualitative relation between angles of arrival and propagation delays of the received signal components; the greater the delay the greater the angle above the horizontal (azimuth plane). Friis and Feldman (1937) [25] exploited this phenomenon with the aid of a special arrangement whereby individual wave groups arriving at different vertical angles were received separately and, after delay equalization, combined coherently to offer directional diversity or directivity diversity. 34 Later, Vogelman et al (1959) [27] extended the concept of a single beam steerable to a multibeam antenna, where signal components associated with individual beams were particularly 30 This implies that (L − 1)T ≥ Tc ⇒ L ≥ (Tc/T ) + 1.…”