This paper provide a review of the active integrated antenna (AIA) technologies. After a brief introduction on the definition and some historical remarks, the paper concentrates on the research effort on the past decades or so. The AlAs are reviewed in its various functions. First, an oscillator-type AIA is presented, followed by very interesting aspects of coupled oscillator arrays for phase control. Use of an AIA concept for efficient RF front ends is described with examples on high-power amplifier AlAs. Next, a phase-conjugation-based retrodirective array is reviewed. Finally, AIA systems for receiving, transmitting, and duplexing are reviewed.

Active integrated antennas

A retrodirective antenna system (1) for receiving an incoming signal (15) from an object (13) and directing an outgoing signal (11) back to the object (13), comprising two or more transceiver cells (3), each of which receives a part of the incoming signal, produces a phase conjugate output signal, which output signals from the cells combine to form an outgoing signal (11) directed back to the object (13), wherein each transceiver cell (3) comprises an antenna component (7) which detects the part of the incoming signal, a processor which receives the part of the incoming signal and produces first and second same-side, sideband (SB) signals of the part of the incoming signal, a phase shift system comprising a first phase element which receives the first SB signal and outputs a SB signal having a first phase, and a second phase element which receives the second SB signal and outputs a SB signal having a second phase which is in quadrature with the first phase, and an IQ modulator comprising an I input port, a Q input port and a phase adjuster, which receives the SB signal having the first phase on the I input port and the SB signal having the second phase on the Q input port, or receives the SB signal having the first phase on the Q input port and the SB signal having the second phase on the I input port, and phase adjusts the SB signals to produce an output signal which is the phase conjugate of the part of the incoming signal.

Retrodirective antenna systems

A novel two-port bi-directional amplifier, which may simultaneously amplify the waves coming from both ports, is proposed and demonstrated in this paper Using this amplifier, a two-element active Van Atta retrodirective array is implemented and compared to a four-element passive array The bi-directional amplifier is constructed by two identical one-port reflection-type amplifiers and a 3-dB 90/spl deg/ hybrid The reflection-type amplifier is designed using an FET with a single-power-supply configuration A quarter-wavelength microstrip radial stub is connected to the device's source terminal to narrow down the negative-resistance frequency range so as to avoid oscillation at undesired frequencies The fabricated bi-directional amplifier provides the transmission gain over the frequency band from 576 to 688 GHz, with a peak value of 91 dB at 604 GHz Printed Yagi antennas with four directors are adopted to build both the active and passive Van Atta arrays The 3-dB back-scattering beamwidth of the active array is measured as wide as 74/spl deg/ Finally, it is observed from the measurements that, although only half of the antenna elements are used, the active Van Atta array produces a back-scattering field level 45 dB, on average, higher than the passive one does This verifies the performance of the bi-directional amplifier

https://ir.nctu.edu.tw:443/bitstream/11536/28112/1/000180980100030.pdf

A novel bi-directional amplifier with applications in active Van Atta retrodirective arrays

A new technique for full duplex digital communications using adaptive phase conjugation is presented in this paper. The technique is based on mixing the RF signal to an IF where it can be easily processed, and filtering the phase of the IF signal to separate the geometry phase and message phase. The retrodirective array automatically tracks communicating platforms and transmits a directive return signal without the use of phase shifters. A 6-GHz microstrip retrodirective antenna array was built, together with the signal IF processing needed for full duplex operation. The measured RCS values of a linear six-element array are in good agreement with theory and result in a 0- to -5-dB RCS for angles up to /spl plusmn/60/spl deg/. The measured RCS values of a circular array are much flatter and are 0 to -5 dB up to /spl plusmn/80/spl deg/. Two-way digital communications at a baud rate of 78 kb/s was also demonstrated with BER<10/sup -6/ for signal-to-noise ratios around 10 dB. The application areas are in high-performance digital mobile telecommunications for commercial and military applications.

Digital communications using self-phased arrays

A retrodirective transponder based on a novel compact phase-conjugating mixer with conversion gain has been developed. The active circuit uses one port for both incoming and outgoing signals, enabling a reduction of circuit size, and the balanced structure provides suppression of undesired signals. By using a modulated local oscillator, the circuit can modulate the received signal in order to retransmit local information to the remote site. A microstrip antenna is integrated with the phase conjugator and the whole system was fabricated on a single substrate, enabling a one-card system. A four-element prototype array with 0.5/spl lambda//sub 0/ array spacing demonstrated excellent measured retrodirectivity. Additionally, a simplified binary-phase-shift-keying signal transmitted by the array is recovered successfully at the source location, demonstrating great potential for remote tagging and wireless sensor applications.

An active integrated retrodirective transponder for remote information retrieval-on-demand

In this paper, a compact architecture for an active planar retrodirective antenna array is presented and its application in a self-tracking duplex communication link discussed. The problem of beam-pointing error (BPE) is addressed and a method is suggested to reduce this error. The proposed architecture, which conventionally performs the function of the retransmission of an incident signal back in the direction of its source, is modified in order to include a receive function. Experimental verification of these architectures are performed at 1 GHz and the results from the prototypes are compared with a theoretical model. Finally, the utility of the architecture is demonstrated for its potential use in a duplex communication link.

Self-tracking duplex communication link using planar retrodirective antennas

This paper presents modeling strategies to determine the operating characteristics of a heterodyne phase-conjugate retrodirective Van Atta (1959) array in the presence of a plane reflector. The models used are based on physical and geometrical optics principles. Predictions of the operating characteristics of the array due to the close proximity of a plane metallic reflector are compared with experimental measurements. It is shown that provided the reflector is positioned at a distance greater than 1.25 times the separation distance between the transmitter and the retrodirective array its effect on the performance of the retrodirective array appears to be negligible.

S.L. Karode

Papers

Self-tracking duplex communication link using planar retrodirective antennas

Reflector effects on the performance of a retrodirective antenna array