Integrated sub-harmonically pumped up-converter antenna for spatial power combining

A Ka-band sub-harmonically pumped up-converter antenna employing the substrate integrated waveguide (SIW) technique is proposed and used to realise a low-cost transmitter together with spatial power combining architecture in this paper. A single Ka-band sub-harmonically pumped up-converter using SIW band-pass filter is developed, exhibiting a conversion loss of about 7 dB. Based on the designed up-converter and SIW feeding antipodal linearly tapered slot antenna (SIW-ALTSA), the integrated up-converter antenna is designed and fabricated. Measured results of equivalent isotropic radiated power (EIRP) and radiation patterns are given. Finally, a 2 x 2 up-converter antenna array is designed and fabricated. Measured result shows the array has a power combining efficiency of above 90% and IM3 EIRP of 16 dBm. In close-range point-to-point communication and radar systems, the demonstrated millimetre-wave sub-harmonically pumped up-converter antenna array can be considered as a transmitter because of its low cost, high dynamic range and high linearity.     

Design and implementation of a substrate integrated waveguide phase shifter

The design and implementation of a phase shifter based on the substrate integrated waveguide (SIW) technique operating at 10 GHz are presented. The proposed phase shifter consists of a SIW section with two inserted metallic posts. The phase shifting in this configuration is achieved by changing the diameter and the position of these posts. Numerical simulations have been carried out for different diameters and positions, which have shown good agreement with the theory. A parametric study was also conducted to assess the impact of errors made on the diameter and position of the two metallic posts. To prove the concept, prototypes were fabricated and measured. Experimental results agree well with simulations and SII was better than -14 dB, S21 better than -1.08 dB and the phase error was less than 1.5deg.     

Linear scanning array with bulk ferroelectric-integrated feed network

Variable ferroelectric delay line technology has been utilized to implement a proof-of-concept, continuous scanning, ferroelectric integrated phased array antenna system. S₂₁ phase shifts of up to 157° have been achieved from the phase shifter itself via analogous variation of a DC bias. When integrated into a phased array, beam scanning of at least ±12° is achieved prior to any optimization. Some of the key material requirements, fabrication procedures, characterization, and assembly of the ferroelectric material are revealed. The design, integration, and performance of the array system using such phased shifters are presented     

Design and implementation of low sidelobe substrate integrated waveguide longitudinal slot array antennas

Low sidelobe longitudinal slot array antennas are investigated based on substrate integrated waveguide (SIW) technology. The design method consists of the characterisation of the radiating element, the synthesis of the linear array and the development of the planar array including a feeding power divider by performing fullwave electromagnetic simulations for the final accurate design. Two planar slot array antennas are fabricated with a normal printed circuit board (PCB) process. Low sidelobe features are verified by the measured results which are in agreement with the simulated results. For an 8 x 8 SIW slot array antenna, the measured sidelobe levels (SLLs) are below 236 dB in the H-plane and below 225 dB in the E-plane with the Gain of 20.3 dB at 9.9 GHz. And for a 16 x 16 antenna, the SLLs are below 230 dB both in the E-plane and H-plane with the Gain of 24.4 dB at 10 GHz. The achieved design goals on the radiation patterns therefore validate the proposed low sidelobe SIW slot array antennas to be valuable candidates for high performance communication and radar applications.     

Hardware-assisted initialisation for constant modulus algorithm adaptive antenna

A cost-effective approach for initialisation of an adaptive antenna based on the constant modulus algorithm (CMA) is proposed. The technique utilises 1 bit phase shifters and a power detector, which are normally integrated with a multibeam antenna, to determine the maximum power beam direction. Consequently, the beam is exploited as an initial beam for CMA. Development of hardware-assisted initialisation is discussed. In addition, field programmable gate array implementation of a CMA processor and associated control circuitry is presented. Several simulations are performed to evaluate the performance of the proposed initialisation technique. In addition, the developed prototype is tested with a phase array antenna designed for operation at the IMT2000 frequency of 1.95 GHz. Experimental results confirm superiority of the proposed technique.     

Compact receiver module for a 94 GHz band passive millimetre-wave imager

A compact receiver module for a 94 GHz band passive millimetre-wave (PMMW) imaging system is developed. This receiver module consists of an antipodal linearly tapered slot antenna (LTSA) and microwave monolithic integrated circuit (MMIC) with flip-chip bonding assembly that provides high radio frequency (RF) performance at low cost. A new microstrip-slot transition developed for the LTSA/MMIC interface is also presented and the design procedure for the LTSA is discussed, which obtains almost the same E- and H-plane beam widths. In addition, a low-noise, high-gain MMIC is discussed using inverted microstrip lines that are developed. Finally, it is shown that the PMMW imager can generate a millimetre-wave image.     

Improved Hybrid Precoding Technique with Low-Resolution for MIMO-OFDM System

This paper proposes an improved hybrid beamforming system based on multiple-input multiple-output orthogonal frequency division multiplexing (MIMO-OFDM) system. The proposed beamforming system improves energy efficiency compared to the conventional hybrid beamforming system. Both sub-connected and full-connected structure are considered to apply the proposed algorithm. In the conventional hybrid beamforming, the usage of radio frequency (RF) chains and phase shifter (PS) gives high power and hardware complexity. In this paper, the phase over sampling (POS) with switches (SW) is used in hybrid beamforming system to improve the energy efficiency. The POS-SW structure samples the value of analog beamformer to make lower resolution than conventional system. The number of output data in POS is decided by the resolution of POS system. The limited number of POS decides the resolution of antenna array and the values of POSs are designed from maximum and minimum phase angle antenna array. Energy efficiency without the phase shifter is high although channel capacity is nearly similar with conventional system. Also, the amplifier with POS-SW system is proposed to improve the BER performance. According to the data bits, the output signals of POS are decided. The system with 2, 3 and 4 bits is simulated to prove the proposed algorithm. In order to overcome the loss of low-resolution system, the amplifier with POS-SW system using channel information is proposed. The average sum-rate of 4 bits system shows the similar performance with the conventional hybrid beamforming system. This structure can play an important role by increasing the energy efficiency of the wireless communication system that many antennas are used. It is shown that the BER, average sum rate and energy efficiency of the proposed scheme are more improved than the conventional hybrid beamforming system.     

Compensated circuit with characteristics of lossless double negative materials and its application to array antennas

A compensated circuit showing the characteristics of lossless double negative (DNG) materials is proposed and applied to an active integrated antenna array. A properly selected matching circuit produces the phase advance, which is characteristic of a left-handed wave (backward-wave), and the lossy resonant circuit generates the negative group velocity. An amplifier is used to compensate for the inherent loss of the resonant circuit, including its resistor. Then, a series-fed antenna array with a proposed DNG circuit is also designed and fabricated. It consists of two subarrays, each made of two aperture-coupled patch antennas, and the DNG circuit block inserted between the subarrays. In comparison to a conventional array, without the DNG circuit whose two subarrays are connected directly by a microstrip line, the proposed array shows a negligible beam squint and flat gain, over a considerable bandwidth of 11%     

X波段基片集成波导四路功分器的设计

 功分器作为复合器、耦合器和天线的馈电系统中的关键部分,在微波、毫米波系统中得到广泛应用.从矩形波导功分器的工作原理出发,利用基片集成波导高Q值、低损耗等特点,研究了基片集成波导功分器的设计规则和关键技术.设计并实际制作了一个X波段基片集成波导的四路功分器.测试结果表明,其输入端反射系数在9.0～11.0 GHz内均小于-15 dB,相对带宽达到了20%,通带内的电压传输系数在-9.0～-7.7 dB之间波动,满足设计要求.该功分器成本低,且结构简单,可以广泛应用于微波电路中,适于批量生产.     

Optically produced true-time delays for phased antenna arrays

A device is described for generating true-time delays optically for microwave signals used in beam steering and beam shaping in phased-array antennas. The device can be adapted to provide delays from picoseconds to nanoseconds. A single, compact unit should provide parallel delays for more than 64 independent antenna elements with a greater than 6-bit resolution. The time delays are produced by multiple reflections in a mirror configuration with continuous refocusing. A single spatial light modulator selects independent optical path lengths for each of the parallel antenna elements. Amplitude control for beam shaping can be integrated into the device. The unit can be made rugged for harsh environments by use of solid-block construction. The operation of the true-time delay device is described, along with the overall system configuration. Preliminary experimental data are given.     

Design of a vector-sum integrated microwave photonic phase shifter in silicon-on-insulator waveguides

An orthogonal vector-sum integrated microwave photonic phase shifter (IMWPPS), consisting of mode-order converter multiplexers (MOCMs), a variable optical power splitter (VOPS), an optical switch (OS) and fixed time delay lines (FTDLs), was theoretically demonstrated in a silicon-on-insulator wafer. MOCMs, as a key element of our device, were employed to generate orthogonal vector signals and served as lossless optical combiners. Combining with the thermo-optical VOPS, OS and FTDLs, the microwave phase shift of 0～2π could be achieved by a refractive index variation of 0～15×10(-3) in the millimeter wave band. The corresponding tuning resolution was about 1.64°/°C. This work, for the first time to our knowledge, provides an attractive solution to transferring a vector-sum method based bulk MWPPS into a integrated one, which is very important for large-scale optically controlled phase array antenna.     

Beamforming technique to solve the hidden beam problem in wireless communication systems

A new method to deal with the hidden beam problem in carrier sensing medium access (CSMA)-based systems is proposed. The method is based on the modification of the beamformer weights that reduce null depths of any given beam. The proposed technique is applied to uniformly spaced linear antenna arrays with broadsided and endfired beams to planar beams and to Dolph?Chebychev beams. The throughput of nonpersistent CSMA systems using a uniformly spaced broadsided linear antenna array is evaluated and the performance of the proposed technique is compared with that of a original beam in terms of reducing the hidden beam problem. The proposed methodology is shown to be effective in solving the hidden beam problem in a CSMA-based system by reducing the null depths and is shown to yield higher throughput than the original beam.     

Sectorised antenna array and measurement methodology for indoor ultra-wideband applications

A new sectorised antenna array (SAA) and measurement methodology are proposed for indoor ultrawideband (UWB) applications. The proposed SAA comprises of one centre element and six side elements. The one centre element and six side elements are arranged in a semi-spherical antenna array configuration. The measurement system and methodology for the coverage of the SAA are developed. The measured bandwidth of the SAA for voltage standing wave ratio (VSWR) <2 is 37.5%, ranging from 3.06 to 4.47 GHz. The boresight gain is more than 5.2 dBi across the impedance bandwidth. The proposed SAA is able to provide omni-directional pattern with an average gain of 5.2 dBi over the angles (0-3608). The discone reference antenna is used to measure the coverage of the proposed SAA. The proposed measurement study shows that the proposed SAA offers omni-directional coverage desirable in UWB indoor location and short-range communication systems.     

Passive varactor tuned equivalent transmission line phase shifter at C-band in 0.25 μ BiCMOS

The design of a C-band phase shifter fabricated in a commercial 0.25 mum BiCMOS technology is presented. Phase shift is enabled by tuning the varactors of a lumped element, equivalent of a transmission line. Only one single control voltage is required. The circuit is optimised for adaptive antenna combining on the basis of the 802.11a standard and matched for 50 Omega terminations. Within a frequency band ranging from 5.2 to 5.8 GHz, the circuit yields a phase control range of higher than 195deg, an insertion loss of only 3.6 +1.5 dB, return losses higher than 12 dB and a 1 dB compression point above 10 dBm. The chip and circuit areas amount to 0.6 and 0.25 mm², respectively. To the knowledge of the authors, at comparable phase control range, the lowest insertion loss for a passive phase shifter integrated in silicon reported to date is demonstrated.     

Demonstration of a folded Sagnac sensor array immune to polarization-induced signal fading

We demonstrate a new folded Sagnac sensor array design that combines a Faraday rotator mirror and a polarization beam splitter to eliminate the optical noise pulses otherwise generated in a folded Sagnac sensor array. A depolarization scheme compatible with this configuration is also proposed and demonstrated experimentally. It is shown that this new configuration passively eliminates polarization-induced signal fading on every sensor in the array. The minimum detectable phase was measured to be approximately 1.1 microrad/square root of Hz, in agreement with theory.     

Achromatic phase shifter with eight times magnification of rotation angle in low coherence interference microscopy

An achromatic phase shifter with a rotating half-wave plate (HWP) used at the input and output of the low coherence interference microscopy is presented. This novel achromatic phase-shifter configuration is first investigated, and then its performances are compared with those of traditional phase shifters theoretically by means of Jones matrices. It is evident that the achromatism and the variation of the amplitude ratio of the proposed achromatic phase-shifter configuration is much better than other traditional phase-shifter configurations, and it can provide a phase shift of eight times the rotation angle of the HWP, which is the largest magnification achieved by far. A low coherence interference microscopy system based on the proposed achromatic phase-shifter configuration is also established to confirm the eight times relation between phase-shift and rotation angle of the HWP experimentally. At last, the three-dimensional profile and the groove depth of a step height calibration standard are obtained by using the traditional four-step algorithm to illustrate the capability and the accuracy of the low coherence interference microscopy system based on the proposed achromatic phase-shifter configuration.     

Design and analysis of compact work-recovery phase shifter for pulse tube refrigerator

This paper proposes and describes a compact work-recovery phase shifter of a pulse tube refrigerator. Most pulse tube refrigerators recently developed utilize a long inertance tube and a reservoir for phase control between dynamic pressure and mass flow rate at the cold-end of pulse tube refrigerators. An inertance tube-type phase shifter (long inertance tube and reservoir), however, sometimes creates a problem of compact packaging in cryocooler applications and dissipates the work transferred from a compressor as heat. To overcome this disadvantage, an inertance tube-type phase shifter is replaced with a compact work-recovery phase shifter composed of a mass–spring–damper system and a linear generator in a pulse tube refrigerator. This process is achieved by using analogy of the inertance tube-type phase shifter and the mass–spring–damper system. This paper describes a specific configuration of the designed compact work-recovery phase shifter. Using the simulation code, the performance of the pulse tube refrigerator with the compact work-recovery phase shifter is estimated. As a result, the pulse tube refrigerator with the compact work-recovery phase shifter has the comparable cooling capacity with the pulse tube refrigerator with the inertance tube-type phase shifter. If the recovery work is properly utilized, it can also achieve higher efficiency than that of the pulse tube refrigerator with a typical inertance tube-type phase shifter. In this paper, the parametric study of the mass, the spring and damper coefficients of the compact work-recovery phase shifter has been done and their effects are specifically evaluated.     

Microstrip antenna array controlled with active phase shifter

Abstract

A two‐element microstrip antenna array controlled with active phase shifters has been fabricated and tested. The phase and amplitude of the active phase shifter output can be continuously changed by controlling the gate voltages of the dual gate FET. This array can be mounted on aircraft or missiles and be used in the direction finder or adaptive array systems.

The mutual couplings between microstrip patches are also experimentally studied. It is found that the self‐impedance and resonant frequencies depend highly on the separation if the patches are separated less than 0.4 wavelength and become constant as the separation is greater than 0.5 wavelength. The effect of mutual coupling in the E‐plane is less prominent than that in the H‐plane. In array patterns synthesis, the mutual coupling can be neglected if the separation is greater than 0.5 wavelength. However, if the separation becomes smaller, the mutual coupling must be considered such that the calculated patterns are in good agreement with the experimental results.     

Lithium niobate guided-wave beam former for steering phased-array antennas

We present the theoretical investigation, design, and simulation of a novel guided-wave optical processor for L-band-transmission beam forming in a linear array of phased active antennas. The proposed configuration includes two contradirectional surface acoustic-wave transducers, and it is based on a Y-cut, X-propagating Ti:LiNbO(3) planar waveguide supporting the lowest-order modes of both polarizations (TE(0) and TM(0)) at the free-space wavelength λ = 0.85 μm. A detailed comparison between the processor we propose and other optical and electronic architectures reported in the literature is carried out, exhibiting a number of significant advantages in terms of weight, total chip size, and power consumption, when the number of antenna elements is greater than 50.