dB Gain Variation Research Articles

A Wideband Flat Gain Low Noise Amplifier Using Active Inductor for Input Matching

This brief presents a wideband flat gain low noise amplifier using active inductor for input matching. The current reuse technique is adopted for the active inductor to reduce power consumption. The noise contribution of the active inductor is optimized by noise cancelling technique. The design is demonstrated in a standard 0.13- ${\mu }\text{m}$ CMOS process. The input return loss is better than 10 dB across the bandwidth of 0.7–4.6 GHz. The nominal gain is 10.1 dB with 1.3 dB gain variation in the passband. The measured noise figure is below 4.5 dB and the input referred third order intercept point is better than −1.6 dBm. The amplifier consumes 4.4 mA from a 1.4 V supply.

High-Efficiency and Wideband Aperiodic Array of Uniformly Excited Slotted Waveguide Antennas Designed Through Compressive Sensing

A uniformly excited slotted waveguide (WG) antenna array for point-to-point communication is presented. The European Telecommunications Standards Institute class-II sidelobe level requirements are satisfied in all planes at almost all frequencies by the aperiodic arrangement of several parallel ridge WGs in the E-plane, each with a different number of equally spaced radiating slots along the H-plane. Both the optimal separation and number of slots per WG are determined through a compressive sensing approach. This results in 160 slots organized in 16 columns offering 29 dBi peak gain at $Ka$ -band. A dedicated 16-way analog beamforming network is designed to provide the optimal nonuniform and in-phase excitation of the 16 WG channels, thereby compensating for the variable number of slots per column and the phase difference due to the E-plane aperiodicity. The measurements confirm the simulated reflection coefficient and radiation pattern characteristics, as well as the high aperture efficiency (70%–90%) over a 13.6% relative bandwidth (27.5–31.5 GHz) and <2 dB gain variation over 3.75 GHz (12.7%).

Wideband Accurate-Out-of-Phase-Fed Circularly Polarized Array Based on Penta-Mode Aperture Antenna Element With Irregular Cavity

This communication presents a wideband circularly polarized (CP) aperture antenna array with a specially designed feeding network. First, an irregular-cavity-backed aperture antenna element is introduced. Due to its penta-mode operation, a 72% CP bandwidth (5.3–11.2 GHz) is obtained, which is much wider than many existing unidirectional aperture-/slot-based CP antennas. In order to solve the element beam tilting problem, a novel four-element array with rotationally symmetric array arrangement and accurate out-of-phase feeding network is then proposed, which has advantages such as compact feeding structure, less gain variation, and symmetric radiation patterns. Measured results indicate that the four-element array achieves a CP bandwidth of 70.6% (5.48–11.46 GHz), a peak gain of 12.8 dBic, a 3 dB gain variation bandwidth of 69%, and averaged front-to-back ratio of 18 dB.

Co-Design of a Wideband Circularly Polarized Filtering Patch Antenna With Three Minima in Axial Ratio Response

A co-design of a wideband circularly polarized (CP) patch antenna is proposed in this paper. The patch antenna is seamlessly integrated with two bandpass filter networks consisting of one and two $\lambda $ /2 resonators, respectively, which are designed to excite two orthogonal modes with equal magnitude and quadrature phase over a widened bandwidth. In co-design of this filtering antenna, the patch antenna is equivalently treated as the last-stage resonator and the output port of the filter network. In analysis of its far field, axial ratio (AR) of CP wave is mapped to its magnitude and phase responses. By simultaneously synthesizing the magnitude ratio and phase difference of the two filter networks’ transmission coefficients to vary around 1° and 90°, respectively, wideband AR response with three minima is realized. Based on this design method and the theoretically derived results, a CP patch antenna prototype with a height of $0.028\lambda _{0}$ is fabricated and measured. It is experimentally demonstrated that around 8.8%, bandwidth can be achieved with VSWR < 2, AR < 3 dB, and 3 dB gain variation.

$W$ -Band Low-Profile Transmitarray Antenna Using Different Types of FSS Units

A low-profile transmitarray (TA) antenna consisted of three different types of frequency-selective surface (FSS) unit cells and a “short” feed horn is proposed. The FSS unit cells, which have different magnitude and phase responses, are properly arranged on one layer of a substrate to enhance the phase-shift range. The proposed TA with a thickness of 0.127 mm ( $0.042~\lambda _{{0}}$ at 100 GHz) is placed near the feed aperture to achieve a low-profile TA antenna. The full TA prototype is fabricated and measured. The maximum gain measured at 100 GHz is 23.8 dBi, which has an 8 dB improvement compared to the feed without increasing the radiation aperture size. A relative bandwidth of 15% is obtained within 3 dB gain variations. The cross-polarization level is −43.4 and −47.9 dB for E- and H-planes, respectively. A maximum gain of 24.5 dBi with an aperture efficiency of 46.1% is achieved at 97.7 GHz. This method considerably reduces the complexity of TA and achieves a much more compact structure.

A fully integrated 4 × 2 element CMOS RF phased array receiver for 5G

This paper presents a fully integrated phased array receiver containing two four element radio frequency (RF) beamforming receivers supporting two multiple-input multiple-output channels. The receivers are designed and fabricated using 45 nm CMOS SOI technology. A 10 bit IQ vector modulator phase shifter (IQVM) is implemented in RF signal paths to control the phase and amplitude of the received signal before combining. Each IQVM provides 360° phase shift control and 17 dB gain variation. An off-chip, simultaneous high-Q impedance matching and bandpass filtering technique for each low-noise amplifiers is presented using non-uniform transmission line segments. Measured downconversion gain at 100 MHz intermediate frequency and noise figure (NF) of a single path are 23 and 5.4 dB, respectively, giving estimated 3.4 dB NF for a single element when simulated PCB and matching losses are taken into account. 1 dB compression point and Input third-order intercept point (IIP3) are − 37 and − 28 dBm, respectively. Each four-element receiver consumes 486 mW DC power from 1.2 V power supply. Total area of two receivers is 5.69 mm2.

A Wideband Microstrip Array Design Using RIS and PRS Layers

In this letter, a wideband microstrip antenna (MSA) array using reactive impedance surface (RIS) and partially reflecting surface (PRS) is proposed. The antenna with RIS and PRS provides wider impedance bandwidth (BW), less gain variation, and further miniaturization compared to antenna with single RIS. The proposed antenna provides 24.3% impedance bandwidth, which covers the frequency band from 5.14 to 6.56 GHz. Maximum gain of 12.5 dBi with less than 1.1 dB gain variation over three individual bands viz. 5.15–5.35 GHz (ISM), 5.725–5.875 GHz (ISM), and 5.9–6.4 GHz (satellite uplink) is achieved. Broadside radiation patterns have sidelobe level (SLL) 20 dB. The overall antenna dimensions are 1.55 λ 0 × 1.55 λ 0 × 0.11 λ 0, where λ 0 is the free-space wavelength corresponding to 5.85 GHz, central frequency of the operating frequency band. The structure is fabricated and tested, and the measured results agree with simulation results.

A mmWave Wideband Slot Array Antenna Based on Ridge Gap Waveguide With 30% Bandwidth

A wideband $8 \times 8$ element slot antenna array based on ridge gap waveguide feeding network has been proposed for mmWave applications. The antenna subarray consists of four radiating slots which are excited by a groove gap cavity layer. Compared with previously published works, the proposed planar antenna array has quite wide impedance bandwidth. The antenna covers a wideband of 50–67.8 GHz with 30% impedance bandwidth (VSWR < 2). Also, the antenna has only 2.5 dB gain variation over the entire bandwidth which implies also good radiation characteristics for the proposed antenna. The maximum measured gain value is about 27.5 dBi with a total efficiency of 80% for the proposed antenna within the band of interest. With this performance, the proposed antenna array is a promising candidate for mmWave communication systems.

A Frequency Agile Microstrip Patch Phased Array Antenna With Polarization Reconfiguration

A novel multifunctional $1 \times 4$ phased array antenna employing wideband frequency agile microstrip patches with simultaneous polarization reconfiguration has been designed and experimentally verified. Each radiating element consists of a circular microstrip patch connected to an annular microstrip ring via four varactor diodes for achieving frequency agility between 1.5 and 2.4 GHz (frequency agility bandwidth $\approx 46$ %, $S_{11} \leq -10$ dB). Employing two feed points per radiator enables switching among four polarization senses (two linear and two circular polarizations) using a polarization feed network (PFN). For realizing beam steering, the optimum amplitude and phase excitation coefficients for each radiating element were calculated using projection matrix method based on active element pattern, which is then applied to each corresponding radiating element using programmable digital phase shifters, low noise amplifiers, and attenuators arranged in a beam forming network. Measurement shows ±52° beam peak steering at 1.5 GHz and ±28° beam peak steering at 2.4 GHz based on 3 dB gain variation criteria for both the linear and circular polarizations. The simulated and measured results agree reasonably well.

Design and Performance Analysis of Raman Amplified XG-PON System

This paper describes the design considerations and performance analysis for an XG-PON Raman amplification scheme. The experimental results and theoretical calculations presented in this paper demonstrate the feasibility of Raman amplification in O-band access systems; thus, enhancing the performance of existing access installations while still preserving the passive nature of these networks. With the availability of cost-effective quantum dot laser diodes as high-power pumps, Raman amplification is proving to be an attractive candidate for access applications. We experimentally demonstrate that it is possible to achieve a total pump power of 759 mW using polarization multiplexed quantum dot laser diodes (QD-LDs), and using a backward pumping scheme we can support a purely passive XG-PON system with 50 km reach and 64 splits. With system level numerical simulations, we illustrate the use of forward or bi-directional pumping scheme to increase the splits further. We also confirm that the Raman pump output in the experiments, despite being below the single mode cut off for the standard SMF, was efficiently coupled into the trunk fibre using off-the-shelf components. We also show using numerical simulations that a flat gain spectrum can be obtained with less than 0.7 dB gain variation across the XG-PON upstream wavelength band (1260–1280 nm) using a multi-wavelength pumping scheme with just two pump wavelengths. From a detailed system analysis, we discuss the impact of broadband filtering (20 nm) at the receiver adopted by the XG-PON standards, and show that lower class (N1) receivers can be adopted for Raman gains higher than 16 dB.

Dual Circularly Polarized Reflectarray With Independent Control of Polarizations

A reflectarray with independent dual-circular polarizations is proposed for the first time. The reflector panel operates in X-band and contains 97 unit-cells. It is made with a lego-type configuration allowing change manually the phase aperture distribution and demonstrating experimentally the independence of both polarizations in the same frequency band. To this end, various beam pointing directions are selected in right-hand and left-hand polarizations. The achieved bandwidth is 790 MHz (9.4% at the center frequency 8.37 GHz) for an axial ratio lower than 3.5 dB with 1.5 dB gain variations.

An inductorless CMOS programmable-gain amplifier with a > 3 GHz bandwidth for 60 GHz wireless transceivers

An inductorless wideband programmable-gain amplifier (PGA) for 60 GHz wireless transceivers is presented. To attain wideband characteristics, a modified Cherry—Hooper amplifier with a negative capacitive neutralization technique is employed as the gain cell while a novel circuit technique for gain adjustment is adopted; this technique can be universally applicable in wideband PGA design and greatly simplifying the design of wideband PGA. By cascading two gain cells and an output buffer stage, the PGA achieves the highest gain of 30 dB with the bandwidth much wider than 3 GHz. The PGA has been integrated into one whole 60 GHz wireless transceiver and implemented in the TSMC 65 nm CMOS process. The measurements on the receiver front-end show that the receiver front-end achieves an 18 dB variable gain range with a > 3 GHz bandwidth, which proves the proposed PGA achieves an 18 dB variable gain range with a bandwidth much wider than 3 GHz. The PGA consumes 10.7 mW of power from a 1.2-V supply voltage with a core area of only 0.025 mm2.

Wideband Variable-Height Dielectric Resonator Reflectarray for X-Band Applications

A variable-height dielectric resonator reflectarray for X-band operation has been described in this paper. The unit cell consists of a rectangular dielectric resonator, conducting plane with etched slot printed on a standard FR4 substrate. The array consists of 97 elements arranged in a circular fashion and it is illuminated by a pyramidal horn. The mutual coupling between the feed and the elements is considered for full-wave analysis. Through a waveguide setup having plane wave excitation at one end, the phase variation with change in height of the dielectric resonators and the reflection efficiency for effective re-radiation of the incident plane waves are computed theoretically using CST Microwave Studio Suite employing Finite Integration Technique. From the simulated results, total gain of 23 dB is achieved along with 24 % bandwidth for 1 dB gain variation at 10 GHz making the reflectarray suitable for radar, remote sensing, radio astronomy, digital broadcasting applications, etc.

Broad and Flat Brillouin Gain Spectrum in Optical Fiber Obtained by Modulating Driving Current of Laser Diode

A simple method for obtaining a broad and flat Brillouin gain spectrum (BGS) is presented. By modulating the driving current of a pump laser diode with triangular waveform, a BGS with lower than 0.3 dB gain variation over >200 MHz is achieved. With this method, the bandwidth of the flattened BGS can be controlled by adjusting the amplitude and/or frequency of the current modulation.

A CONSTANT GAIN ULTRA-WIDEBAND ANTENNA WITH A MULTI-LAYER FREQUENCY SELECTIVE SURFACE

An ultra-wideband (UWB) antenna with a novel multi-layer frequency selective surface (FSS) reflector is presented. A significant enhancement in the gain has been achieved in a low profile design while maintaining the excellent impedance bandwidth of the UWB antenna. The average peak gain of the antenna has been increased from 4 dBi to 9.3 dBi as a consequence of the use of the FSS reflector. More importantly the gain variation within the frequency range from 3 GHz to 15 GHz is only +/-0.5 dB. This is a significant improvement from §2 dB gain variation of the UWB slot antenna without the reflector. This optimized FSS re°ector provides the flexibility of mounting a planar antenna close to conducting bodies, including screens and cases

Ultra-flat Brillouin gain spectrum via linear combination of two acoustically anti-guiding optical fibres

A novel approach to broadening and flattening the Brillouin gain spectrum is presented. A linear combination of two acoustically anti-guiding optical fibres gives rise to a Brillouin spectrum with less than 0.5 dB gain variation over>200 MHz. The fibres are selected so that they possess individual Brillouin spectra that are shifted in frequency from each other, such that a relative maximum of one overlaps with a relative minimum of the other.

Varying Slot Lengths Strip Loading Squared Dielectric Resonator Reflectarray

a new type of dielectric resonator reflectarray composed of 529 elements covering an area of 276 x 276 cm<SUP>2</SUP> is constructed. The unit cell consists of squared DRA supported on a strip with variable slot length, a dielectric layer and a conducting ground plane. The full phase of 360 degree of the array elements can be obtained by superposition two slot-strip sizes. Two types of feeding were analyzed, the first is center fed reflectarray while the second is offset feed to reduce the feeder blockage and as a result the antenna efficiency is improved. The antenna has 10% bandwidth for 1 dB gain variation is obviously wider than that of conventional reflectarray antenna while the offset fed reflectarray provide better far field pattern with back lobes reduction by -5 dB and side lobe by -2 dB. A rectangular X- band pyramidal horn was used in both reflectarrays which have 23 x 23 elements of with cells separation of 12 mm that less than 15 mm (lambda/2) for avoiding grating lobes. CST microwave studio<SUP>©</SUP>(finite integral technique) package is applied and compared with microstripes<SUP>©</SUP> package (transmission line technique) with good agreements between them. The mutual coupling between the feeding horn and the elements of the reflectarray are considered. At 10 GHz, the antenna provides a 3-dB beamwidth of 6 degree with a gain of 28 dB. The antenna bandwidth within 1dB gain variation is found to be 13% and aperture efficiency of 59%.

Dual Sized Varying Slot Lengths Loading Dielectric Resonator Reflectarray

A reflectarray antenna consists of elements of rectangular dielectric resonator (DRA) with slot loading of different lengths is proposed for bandwidth enhancement. Two DRA sizes an two slot widths are available to tune the phase of each element in the reflectarray so that a full 360 degrees phase shifts can be achieved by superposition. Two structures are presented in that paper. The first is center fed reflectarray while the second is offset fed for decreasing the feeder blockage. The antenna has 10% bandwidth for 1 dB gain variation is obviously wider than that of conventional reflectarray antenna while the offset fed reflectarray provide better far field pattern with back lobes reduction by -5 dB and side lobe by -2 dB. A pyramidal X-band horn was used in both reflectarrays which have 23 x 23 elements of with cells separation of 12 mm that less than 15 mm (lambda/2) for avoiding grating lobes. The analyses are carried out using the finite integration technique (FIT) and the transmission line method (TLM) with good agreements between them.

A 1.8-V, 5-mA reconfigurable analog baseband circuit for low-IF multi-mode multi-band receivers

A 1.8-V, 5-mA reconfigurable analog baseband circuit for low-intermediate frequency multi-mode multi-band receivers is presented. It consists of four fixed-gain amplifiers, four programmable gain amplifiers, a complex band-pass filter (CBPF) with reconfigurable bandwidth and a received signal strength indicator (RSSI). CBPF is implemented as the third-order Bessel active resistor–capacitor structure to provide the image rejection with flat group delay, and one on-chip automatic frequency tuning circuit is utilised to set the accurate frequency characteristics and overcome the effects of the process and temperature variations. The reconfigurable analog baseband circuit has been implemented in 0.18 µm complementary-symmetry metal–oxide–semiconductor. The measured results show that the presented circuit could provide 34 dB variable gain, 2 MHz/1 MHz/0.5 MHz reconfigurable bandwidth and accurate RSSI indicator. The analog baseband circuit is powered with a 1.8-V supply and totally draws a current of 5 mA.

Amplified OTDR Systems for Multipoint Corrosion Monitoring

We present two configurations of an amplified fiber-optic-based corrosion sensor using the optical time domain reflectometry (OTDR) technique as the interrogation method. The sensor system is multipoint, self-referenced, has no moving parts and can measure the corrosion rate several kilometers away from the OTDR equipment. The first OTDR monitoring system employs a remotely pumped in-line EDFA and it is used to evaluate the increase in system reach compared to a non-amplified configuration. The other amplified monitoring system uses an EDFA in booster configuration and we perform corrosion measurements and evaluations of system sensitivity to amplifier gain variations. Our experimental results obtained under controlled laboratory conditions show the advantages of the amplified system in terms of longer system reach with better spatial resolution, and also that the corrosion measurements obtained from our system are not sensitive to 3 dB gain variations.