Self-oscillating Active Integrated Antenna Research Articles

Multi-layer approach of polarization agile oscillating-type active integrated array antennas for RFtransmitter front-end

AbstractThis paper presents a polarization switchable self-oscillating active integrated array antenna (AIAA) using a multi-layer approach. The antenna comprises two antenna elements, four PIN diodes, and a Gunn oscillator employing a microstrip line resonator. Reconfiguring the feed network of the array antenna realizes slant polarization (± 45°) switching. The multi-layer structure allows the patch spacing to be adjusted, thereby helping to minimize the antenna's sidelobe level. The Gunn oscillator, which employs a λ/2 microstrip–line resonator, is placed at the bottom layer. The proposed AIAA has an effective isotopic radiated power (EIRP) of + 18.25 dBm at the oscillation frequency of 9.47 GHz. EIRP is improved by better than 8.45 dB compared to the single-layer structure. The proposed AIAA features a transmitted power of + 8.45 dBm, DC-to-RF efficiency of 1.0%, and a low phase noise of −101.8 dBc/Hz at 1-MHz offset frequency with better than 12-dB cross-polarization suppression.

A Beam-Switchable Self-Oscillating Active Integrated Array Antenna Using Gunn Oscillator and Magic-T

Herein, a novel self-oscillating active integrated array antenna (AIAA) is proposed for beam switching X-band applications. The proposed AIAA comprises four linearly polarized microstrip antenna elements, a Gunn oscillator, two planar magic-Ts, and two single-pole single-throw (SPST) switches. The in/anti-phase signal combination approach employing planar magic-Ts is adopted to attain bidirectional radiation patterns in the φ =90° plane with a simple structure. The proposed antenna can switch its beam using the SPST switches. The antenna is analyzed through simulations, and a prototype of the antenna is fabricated and tested to validate the concept. The proposed concept is found to be feasible; the prototype has an effective isotropic radiated power of +15.98dBm, radiated power level of +4.28dBm, and cross-polarization suppression of better than 15dB. The measured radiation patterns are in good agreement with the simulation results.

Self-Oscillating Circularly Polarized Active Integrated Monopole Antenna Using Cross-Coupled Pair and Inverted-L Strip

A self-oscillating active integrated antenna (AIA) featuring circular polarization (CP) is presented in this letter. The oscillation is sourced by a cross-coupled pair (XCP) with negative conductance. Microstrip lines with embedded LC resonators are applied to fulfill the feedback loop between the pair of transistors, which functions as the frequency selective element with harmonic suppression capability. A monopole antenna is attached to the output of the XCP for radiating the oscillation power into space; the CP operation, meanwhile, is obtained by introducing a perturbation using an inverted-L strip protruding from the ground plane. A left-handed circularly polarized AIA (CPAIA) was designed at 916 MHz as a potential far-field wireless power charging source in the ultrahigh-frequency ISM (industrial, scientific, medical) band. The experimental validation reveals that, when compared with existing CPAIA designs, the proposed work consumes much less dc power but still keeps acceptable radiation parameters; it also features the smallest size and highest dc-to-RF conversion efficiency. The lowpower consumption makes the direct integration with a small-size solar panel become feasible.

Self-Oscillating Active Integrated Antenna With Harmonic Suppression Using Metamaterial Resonators and Ground Radiation

A self-oscillating active integrated antenna (AIA) with harmonic suppression using metamaterial resonators and ground radiation is proposed and investigated. Two composite right-/left-handed (CRLH) cells are connected in parallel and operated at negative first-order mode as the left-handed resonators to serve as the frequency selective element and the feedback path of the oscillating circuit at the same time. Meanwhile, the radiation parameters are independently controlled by exciting dipole-like ground-mode radiation using the CRLH cells. Benefiting from the high-quality factor of the CRLH cells and the newly added harmonic choking filters, the proposed AIA shows extraordinarily low phase noise, along with notable radiation parameters and good dc-to-RF conversion efficiency. The design principle, linear and nonlinear simulated data, and experimental results are carefully discussed and validated.

A Wearable Self-Injection-Locked Sensor With Active Integrated Antenna and Differentiator-Based Envelope Detector for Vital-Sign Detection From Chest Wall and Wrist

This paper presents a new wearable self-injection-locked sensor with a self-oscillating active integrated antenna (AIA) and a differentiator-based envelope detector for detecting vital signs from the chest wall and the wrist. The AIA is designed to radiate the electromagnetic signal and sense the scattered-back signal, which is phase modulated by the physiological movement of the human chest and wrist. The received self-injection signal from the subject under test locks the AIA and simultaneously introduces a variation in the output magnitude (amplitude modulation) and a shift in the oscillation frequency (frequency modulation). In other words, the output signal of the AIA is a frequency-modulated carrier with an amplitude-varying envelope. To acquire the vital signs from the modulated signal, an envelope detector is integrated with a microwave differentiator to form a differentiator-based envelope detector, which demodulates signal. The heartbeat and wrist pulse rates measured by the proposed sensor agree well with the results acquired by a finger pulse oximeter. Since the proposed demodulator has a simple architecture, it has a potential to be integrated with the AIA in a multilayered printed-circuit board for the realization of a compact wearable self-injection-locked radar sensor.

Zeroth-Order Self-Oscillating Active Integrated Antenna Using Cross-Coupled Pair

By ingeniously integrating a pair of zeroth-order resonators (ZORs) with a cross-coupled pair, for the first time, a novel zeroth-order self-oscillating active integrated antenna (AIA) is developed. Unlike the conventional feedback oscillating AIA, the new configuration is realized by, respectively, inserting a ZOR into each of the feedback paths of the cross-coupled pair to satisfy the Barkhausen criterion, and hence stabilize the oscillation. A self-oscillating AIA operates at the UHF radio frequency identification (RFID) band was demonstrated as a proof of concept. Benefitting from the infinite-wavelength property, the embedded ZORs are electrically large and capable of providing efficient power radiation into space. The oscillation parameters, meanwhile, remain good, thanks to the inherent high-quality factor property of metamaterial resonators. Without relying on ground radiation, the new design achieves good radiation and oscillation performances at the same time, hence adding extra flexibility on shaping the radiation pattern. According to the experimental results, the developed AIA, oscillating at 0.92 GHz, features a high dc-to-RF conversion efficiency of 52%, a moderate effective isotropic power of 8.9 dBm, and a low phase noise of −124.7 dBc/Hz at a 1 MHz offset from the carrier frequency. The design principle and experimental demonstration are thoroughly discussed.

High-Efficiency Self-Oscillating Active Integrated Antenna Using Metamaterial Resonators and Its Application to Multicarrier Radio Frequency Identification Systems

A self-oscillating active integrated antenna with very high dc-to-radio frequency (RF) conversion efficiency is proposed and validated with the aid of metamaterial resonators. The key innovation is the new integration scheme which allows an independent control of the resonators used in the feedback oscillator and the radiating element in the integrated antenna. The metamaterial resonator, featuring a high quality factor for good oscillation performances, is applied to excite the dipole-mode ground radiation with good radiation efficiency at the same time. The design principle is introduced; the circuit and antenna parameters including the loop gain, oscillation output power, phase noise, effective isotropic radiated power, and radiation patterns are investigated in detail. Its application to multicarrier RF identification systems as a low-cost continuous-wave source is supported by quantitative measurement results.

Pattern-Reconfigurable Self-Oscillating Active Integrated Antenna With Frequency Agility

A frequency-agile pattern-reconfigurable self-oscillating active integrated antenna (AIA) is investigated in this paper. With the aid of two PIN diodes and a varactor, the proposed active antenna shows pattern reconfigurability and frequency tunability at the same time. The antenna, composed of two monopoles and a semi-ring radiator, can be switched between four states, with two featuring omnidirectional patterns and the other two having end-fire radiation. The polarizations of the two omnidirectional states are spatially orthogonal to each other. By embedding a varactor diode, the voltage-controlled tuning range is from 4.27 to 4.94 GHz, while the effective isotropic radiated power (EIRP) varies from 5.4 to 9.3 dBm. The phase noise is better than ${-}102.7$ dBc/Hz at a 1-MHz offset from the carrier frequency.

Miniaturized Self-Oscillating Active Integrated Antenna with Quasi-Isotropic Radiation

By placing a loop radiator over a truncated ground plane, a self-oscillating active integrated antenna with quasi-isotropic radiation is proposed in this communication. The proposed antenna comprises a loop radiator and an unstable transistor in direct integration. As the radiator is partially shielded, equivalent electric and magnetic dipole moments can be generated simultaneously, therefore giving rise to nearly uniform radiation in terms of the total electric field. The design concept is first introduced, followed by the simulation scheme and experimental results. The measured radiation characteristics support the operational principle of the proposed scheme.

Frequency-Reconfigurable Self-Oscillating Active Antenna With Gap-loaded Ring Radiator

We investigate a new topology for realizing a compact frequency-reconfigurable self-oscillating active integrated antenna. The new design consists of a passive ring radiator, an unstable transistor, and two p-i-n diodes. Two gaps are etched across the radiator, with the diodes bridging the gaps to switch the antenna topology. By properly selecting the location of the gap with respect to the gate/drain terminals, the oscillation can be stabilized at two distinct frequencies, each associated with a resonance mode of the ring radiator. The simulated methods and experimental results are introduced in this letter, along with the discussion of design principles and considerations.

A dual-gate FET subharmonic injection-locked self-oscillating active integrated antenna for RF transmission

A planar subharmonic injection-locked GaAs dual-gate MESFET (DGMESFET) self-oscillating active integrated antenna (AIA) is presented for RF transmission. The oscillation is obtained with one gate of the DGMESFET at 2.052 GHz, and the stabilization of the oscillation is achieved by injecting a small subharmonic low-noise signal into the other gate of the DGMESFET. Phase noise was measured to be -98 dBc/Hz at the 10 KHz offset. The structure was shown to have the potential in performing triple functions of radiation, low noise oscillation and mixing (or modulation), a capability required for low cost wireless systems such as RFID tags and indoor positioning systems.