Noor Azwan Shairi

Design of reconfigurable defected ground structure (DGS) for UWB application

This paper presents the design of reconfigurable defected ground structure (DGS) resonator that can be integrated with ultrawide-band (UWB) microwave filter to produce bandpass and bandstop response simultaneously. The reconfigurable DGS is designed based upon coplanar waveguide (CPW) technology to exhibit bandstop characteristic at 3.5 GHz and 5.5 GHz using FR-4 on a 1.6 mm dielectric substrate thick with dielectric constant εr = 4.6. The simulation performance shows promising results that could be further validated during the experimental works. This topology of reconfigurable DGS is useful for applications when the undesired signals need to be removed such as in wideband systems.

BANDSTOP TO ALLPASS RECONFIGURABLE FILTER TECHNIQUE IN SPDT SWITCH DESIGN

In this paper, a bandstop to allpass reconflgurable fllter technique is proposed in Single Pole Double Throw (SPDT) switch design. Proof of concept of the bandstop to allpass reconflgurable fllter is presented. It is physically realized using transmission line and radial stub in 3.5GHz band (3.4 to 3.6GHz). The isolation, insertion loss and return loss of the SPDT switches are analyzed and to validate this technique the prototypes are fabricated using FR4 substrate with a thickness of 16mm. A very good agreement is shown between the simulated and measured results. Using this technique, it is able to produce more than 30dB isolation with minimum number of PIN diodes, thus reducing 42.7% of the total circuit size compared with conventional design. Besides, additional 22.9% of isolation bandwidth can be obtained with the use of radial stub compared with transmission line stub. The potential application of this SPDT switch is Time Division Duplex (TDD) switching for WiMAX and LTE communication system in the 3.5GHz band.

The potential application of switchable matched parallel-coupled stub resonator in SPDT discrete switch design

This paper discusses the potential application of switchable matched parallel-coupled stub resonator for isolation improvement of Single Pole Double Throw (SPDT) discrete switch in wireless communication system. In addition, an absorptive SPDT switch also can be obtained by the use of the matched resonator. Frequency spectrum at 2.010-2.025 GHz band for TD-SCDMA is chosen to demonstrate this technique. The discussion of the conceptual and operation of the matched resonator and the SPDT switch are included in this paper. The circuit is simulated for further analysis in simulation software where parameters of microstrip line and FR4 substrate are taken into account. Result in simulation shows 15 dB return loss at absorptive port with 40 dB isolation at resonant frequency and more than 30 dB of isolation between 2.010-2.025 GHz.

Isolation improvement of discrete PIN diode switch using square dumbbell Defected Ground Structure

The potential application of Defected Ground Structure (DGS) for isolation improvement of series discrete PIN diode switch is proposed in this paper. A square dumbbell DGS was selected for this application where it was connected in parallel with a single series discrete PIN diode. By realizing the circuit using FR4 substrate, the simulated and measured result clearly show that the isolation of the series discrete PIN diode during OFF state can be improved by square dumbbell DGS. By demonstrating it in 1.5 GHz frequency band, more than 30 dB isolation can be achieved if compared to single series discrete PIN diode without DGS.

Third order intermodulation distortion effect on the constellation error in RF transmitter of IEEE 802.11a WLAN system

In wireless data communication, an advanced nonlinear distortion analysis is required in order to see its effect to the performance of a Radio Frequency (RF) front-end system. This technical paper therefore, reports the effect of third order intermodulation (IM3) distortion on the constellation error (a key measure of modulation quality) in RF transmitter of IEEE 802.11a wireless local area network (WLAN) system. The selected RF transmitter architecture is based on the off-the-shelf components. Advanced Design System (ADS) software has been used for RF transmitter modeling and simulation. The constellation error simulation is based on the IEEE 802.11a standard. As results, two observations have been obtained. First, it is shown that the IM3 distortion in the RF transmitter for IEEE 802.11a WLAN system must be kept in minimum level in order to get lower constellation error. Second, with the same IM3 distortion level, the constellation error is very sensitive to the IM3 distortion at higher data rate (e.g. 54 Mbps) compared to lower data rate (e.g. 6 Mbps).

A NOVEL RECONFIGURABLE UWB FILTERING-ANTENNA WITH DUAL SHARP BAND NOTCHES USING DOUBLE SPLIT RING RESONATORS

This study presents a novel technique for designing an ultra-wideband (UWB) filteringantenna with dual sharp band notches. This design is composed of a modified monopole antenna integrated with resonant structures. The monopole antenna is modified using microstrip transition between the feedline and the patch. In addition, block with a triangle-shaped slot is loaded on each side of the ordinary circular patch to produce wide bandwidth with better return loss and higher frequency skirt selectivity. The resonant structures are constructed using two double split ring resonators (DSRR) loaded above the ground plane of the antenna to produce dual band notches and filter out WiMAX (3.3–3.7GHz) and HiperLAN2 (5.4–5.7GHz) frequencies. The band notch position is controlled by varying the length of the DSRR. The reconfigurability feature is achieved by using two PIN diode switches employed in the two DSRR. The measured results show that the proposed filtering-antenna provides wide impedance bandwidth from 2.58 to 15.5GHz with controllable dual sharp band notches for WiMAX and HiperLAN, peak realized gain of 4.96 dB and omnidirectional radiation pattern.

Fixed And Selectable Multiband Isolation Of Double Pole Double Throw Switch Using Transmission Line Stub Resonators For Wimax And Lte

A novel selectable multiband isolation of Double Pole Double Throw (DPDT) switch with switchable transmission line stub resonators has been proposed for applications of WiMAX and LTE in 2.3 and 3.5 GHz bands. In this paper, two DPDT switch designs are proposed; the first design is a fixed DPDT switch, and the second is a selectable DPDT switch. The second design allows selecting only one band and unselecting the other or selecting both of them. However, the first design does not allow so. The transmission line stub resonator used in this design is an open stub resonator with quarter wave of the electrical length. By using a simple mathematical model, the theory of the transmission line stub resonator was discussed where it can be cascaded and resonated at center frequencies of 2.3 and 3.5 GHz. Moreover, the cascaded transmission line stub resonators can be reconfigured between allpass and bandstop responses using discrete PIN diodes. The key advantage of the proposed DPDT with switchable transmission line stub resonators is a multiband high isolation with minimum number of PIN diodes. Therefore, the simulated and measured results showed less than 3 dB of insertion loss, greater than 10 dB of return loss and higher than 30 dB of multiband isolation in 2.3 and 3.5 GHz bands.

Design of microstrip bandpass filter with electronically tunable notch response

An integrated high selectivity microstrip wideband bandpass filter with tunable notch response is presented in this paper. The bandpass filter is designed using 7th order short circuited stub filter. Then, the first short circuited stub is replaced with two sections of open circuited stub to exhibit the transmission zeros at lower/higher stopband. The integration with notch filter is realized using U-shape Defected Microstrip Structure (DMS) with varactor diode. By properly varying the DC bias voltages, the notch response can be tuned over a constant bandwidth of around 17%. The experimental result shows that the bandwidth of the wideband bandpass filter is between 2.9 GHz - 5.8 GHz. The notchs tuning range from 4 GHz to 5 GHz is achieved using varactor diode respectively. This type of filter is suitable for applications such as the multi-service and multiband communication system in order to discriminate the undesired signals.

Multiband isolation of DPDT switch with switchable transmission line stub resonators for WiMAX and LTE in 2.3 and 3.5 GHz bands

This paper proposes a multiband isolation of Double Pole Double Throw (DPDT) switch with switchable transmission line stub resonators for applications of WiMAX and LTE in 2.3 and 3.5 GHz bands. The transmission line stub resonator used in this design is an open stub resonator with quarter wave of the electrical length. By using a simple mathematical model, the theory of the transmission line stub resonator was discussed where it can be cascaded and resonated at center frequencies of 2.3 and 3.5 GHz. Moreover, the cascaded transmission line stub resonators can be reconfigured between allpass and bandstop responses using discrete PIN diodes. The key advantage of the proposed DPDT with switchable transmission line stub resonators is a multiband high isolation with minimum number of PIN diodes. Therefore, the simulated and measured results showed less than 3 dB of insertion loss, greater than 10 dB of return loss and higher than 30 dB of multiband isolation in 2.3 and 3.5 GHz bands.

Switchable absorptive bandstop to bandpass filter using dual-mode ring resonator

In this paper, a new switchable absorptive bandstop to bandpass filter using dual mode ring resonator is presented. This switchable filter provides two modes of operation which is absorptive bandstop and bandpass response. The first part of this paper presents a theoretical analysis of the absorptive bandstop dual mode ring resonator based on two low-Q lossy resonators topology. The operating frequency of the absorptive bandstop filter is 2.4 GHz with S11 > −10dB and S21 > −30dB. The absorptive bandstop response can be achieved by controlling the K-inverter and perturbing stub. The second part of this paper presents an investigation and the design of the switchable absorptive bandstop to bandpass filter in EM simulation. Varactor diodes are used to control the K-inverter and a PIN diode is used as the ON and OFF switch of the additional length of perturbing stub. A bandpass response can be achieved by controlling the voltage from 1 V to 10 V of the varactor diodes. The bandpass response can be enhanced to dual-mode bandpass response by adding additional length to the perturbing stub. The parametric studies together with the EM simulation of the new switchable absorptive bandstop to the bandpass dual mode ring resonator filter is presented in this paper.