Christina F. Jou

Novel Broadband Monopole Antennas With Dual-Band Circular Polarization

Novel broadband monopole antenna designs with dual-band circular polarization (CP) are presented. The proposed antenna comprised of a ground plane embedded with an inverted-L slit, which is capable of generating a resonant mode for broadband impedance-bandwidth, and excites two orthogonal E vectors with equal amplitude and 90deg phase difference (PD) for radiating left-hand circular polarization (LHCP) at 2.5 GHz and right-hand circular polarization (RHCP) at 3.4 GHz. A bevel is cut in the rectangular radiator to increase the impedance-bandwidth. The measured result of the impedance-bandwidth is about 4.46 GHz from 2.12 to 6.58 GHz; the 3-dB axial ratio (AR) bandwidths are about 150 MHz at the lower band (2.5 GHz) and 230 MHz at the upper band (3.4 GHz). Furthermore, embedding an I-shaped slit in the rectangular radiator and adding an I-shaped stub in the ground plane, the impedance-bandwidth can be further increased to 6.30 GHz (2.17-8.47 GHz), and the 3-dB AR-bandwidth at the upper band is greatly enhanced from 230 to 900 MHz.

An Novel L-shape Active Leakly-Wave Antenna with power combining and scanning capability

In this paper, an active-integrated leaky-wave antenna with power combining scanning capability is presented. This leaky-wave antenna with the novel perpendicular L-shape topology is integrated with a varactor-tuned high-electron mobility transistor (HEMT) voltage controlled oscillator (VCO) on the same plane. Changing the VCO frequency, we can control not only the dual-beam scanning angle but also derive the power combining effect with the sum (L) or difference (A) radiation patterns. The power combing effect of difference mode, which is the dual-beam pattern and the sum mode pattern, which is a 3-beam pattern, with the 3rd beam located along the middle direction (450, 1350) of the X and Y axes. The measured scanning angle is steered over a range of 24-460 for the right beam and 127-1480 for the left beam. Compared with single microstrip leaky-wave antenna, the L-shape LWAs configuration has the advantages of switchable radiation patterns as the VCO varied from 10GHz to 10.6GHz.

Development of a Flexible SU-8/PDMS-Based Antenna

In this letter, a flexible SU-8/PDMS-based antenna has been demonstrated, not only targeting the wearable computing, but also fitting well in the RF system-on-package (RF SOP) applications. The characteristics of the proposed antenna fabricated on a flexible polymer substrate (SU-8/PDMS) with different bending angles have been successfully measured and characterized for the first time. The measured results have shown fairly good agreement with the simulation results. The measured bandwidth and maximum gain are 3% from 6.2 to 6.4 GHz and 2.17 dBi, respectively, when the antenna is flat. Moreover, related antenna fabrication process provides a practical approach to realize the flexible antenna for the portable wireless electronics applications.

A Low Voltage Mixer With Improved Noise Figure

A 5.2 GHz low voltage mixer with improved noise figure using TSMC 0.18 mum CMOS technology is presented in this letter. This mixer utilizes current reuse and ac-coupled folded switching to achieve low supply voltage. The noise figure of the mixer is strongly influenced by flicker noise. A resonating inductor is implemented for tuning out the parasitic components, which not only can improve noise figure but also enhance conversion gain. A low voltage mixer without resonating technique has also been fabricated and measured for comparison. Simulated results reveal that flicker corner frequency is lowered. The measured results show 4.5 dB conversion gain enhancement and 4 dB reduction of noise figure. The down-conversion mixer with resonating inductor achieves 5.8 dB conversion gain, -16 dBm P1dB, -6 dBm IIP3 at power consumption of 3.8 mW and 1 V supply voltage.

A novel two-beam scanning active leaky-wave antenna

A novel two-beam scanning active leaky-wave antenna (LWA) has been developed. This LWA with a two-terminal feeding microstrip line structure is integrated with a varactor-tuned X-band high-electron mobility transistor (HEMT) voltage-controlled oscillator (VCO). The signal of the VCO is injected via a T-divider into the radiating element. To excite the first higher order mode, the designed antenna is fed asymmetrically at both ends of the microstrip line. Compared with single-terminal feeding leaky-wave antennas, this configuration offers the advantages of dual-direction and suppression of the reflected wave caused by the open end of the radiating element. The scanning angle is steered over a range of 24-46/spl deg/ for the right beam and 128-150/spl deg/ for the left beam. The effective isotropic radiated power (EIRP) is calculated to be 17.5 and 16.67 dBm at 10.4 GHz, respectively. The measured return loss S/sub 11/ is less than -10 dB in the range of 9-11.5 GHz. The transmission coefficient S/sub 21/ indicates that the power radiates into the space.

Complementary UWB LNA Design Using Asymmetrical Inductive Source Degeneration

This letter proposes a novel LNA design method where the complementary transistor topology is combined with asymmetrical inductive source degeneration to achieve matched input impedance over a wide bandwidth. A 2-10 GHz LNA is designed and fabricated using a commercial 0.18 RF-CMOS process to verify the feasibility of our proposed method. In the intended bandwidth, this LNA has matched input impedance, 20 dB power gain, and 2.4-3.4 dB noise figure, with 25.65 mW power consumption.

Design of a 3.1-10.6GHz low-voltage, low-power CMOS low-noise amplifier for ultra-wideband receivers

A low-voltage, low-power ultra-wideband (UWB) low-noise amplifier (LNA) for IEEE 802.15.3a is presented. A simplified Chebyshev filter is used to achieve the input broadband matching. This input network has lower complexity and good reflected coefficient from 3.1GHz to 10.6GHz. An output-matching buffer is designed specially to match for maintaining high gain at upper frequency. Therefore, it can both achieve flat gain over the whole bandwidth and generate more output current. The LNA is simulated based on TSMC 0.18/spl mu/m mixed signal/RF process. With only 1V bias voltage, the LNA can achieve power flat gain of 10dB with input matching of -9.76dB; the minimum noise figure 3.7dB; and input third-order-intercept point (IIP3) of -1dB. The power dissipation is only 7.2mW.

Studies of suppression of the reflected wave and beam-scanning features of the antenna arrays

This paper describes a two-directional linear scanned design by integrating a short leaky-wave antenna (LWA) with aperture-coupled patch antenna arrays. This architecture proposes a technique not only having the advantage of suppressing the back-lobe due to the reflected wave in the short LWA but also producing two separate linearly scanned beams, each of them radiating in a different region of space (in both the front side and backside of the LWA). In this design, most of the reflected wave of the short LWA is coupled to the patch antenna arrays on the backside of the substrate. The phase of this coupled signal to each antenna element is adjusted by tuning the individual phase shifter in order to control electronically the patch antenna main beam in the cross plane (x<0). Meanwhile, on the front side, the main beam of the short LWA can be simultaneously scanned in the elevation plane (x>0) by changing the operating frequency. Hence, the two linear beam-scanning radiation patterns of individual direction can be created independently, including a narrow beam in the elevation plane (xy plane at x>0) at the front side and a broadside beam in the cross plane (xz plane at x<0) on the backside. The measured results show that the reflected wave of the short LWA in the proposed design is suppressed 8 dB as compared with a traditional short LWA without the aperture-coupled antenna arrays at 10.5 GHz. As a result, this novel architecture provides more flexibility both in the upward elevation plane (H plane) and the downward cross plane (backside-E plane) for possible beam-scanning applications in microwave communications and remote identification.

Two-dimensional scanning leaky-wave antenna by utilizing the phased array

An aperture-fed patch antenna array is connected to the open end of a short leaky-wave antenna (LWA) to demonstrate the two-dimensional beam-scanning capability in this paper. This design not only offers another radiation path of the reflected wave, but also creates another scanning radiation pattern on the back plane of the substrate. The reflected wave of the LWA is equally separated by a power divider, modulated by each varactor-tuned phase shifter, and injected into two radiating aperture-coupled antennas. The operated frequencies are tuned to control the LWA main position in the elevation plane; meanwhile, by tuning the phase difference between two phase shifters, the main beam of the aperture-coupled antenna array can be scanned in the backside E plane. Experimental result shows that the suppression of the reflected wave can be 7 dB at 10.0 GHz with a short LWA length of 6 cm (two wavelengths). The H-plane and backside E-plane scanning radiation patterns have great potential in many applications and provide more flexibility to traditional designs.

A Low Phase Noise Quadrature VCO Using Symmetrical Tail Current-Shaping Technique

This letter presents a new symmetrical tail current-shaping technique to improve the phase noise of a quadrature voltage-controlled oscillator (QVCO). This proposed QVCO consists of two first-harmonic injection-locked oscillators (ILOs) and the outputs are injected back to the gates of the QVCOs tail transistors in order to shape the tail currents. A switching current path is provided between the two tail current sources in order to eliminate the asymmetric phenomenon of the tail currents. The measured phase noise can be improved by 4 dB using this technique. This CMOS LC-tank QVCO has been implemented using the TSMC 0.18 μm mixed-signal/RF CMOS 1P6M technology and the die area is 0.7 × 1.1 mm2. The total power consumption is 11.2 mW at the supply voltage of 1.4 V. The measured phase noise at 1 MHz offset is -119.3 dBc/Hz at the oscillation frequency of 5.28 GHz. The figure of merit (FOM) of the proposed QVCO is -183 dBc/Hz.