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An X-band high-power amplifier (HPA) based on gallium nitride (GaN) high electron mobility transistors (HEMTs) has been developed for synthetic aperture radar (SAR) applications. A hybrid power combining technique, including microstrip circuits and waveguides, is used to design the HPA. For reducing the size, four 50 W GaN HEMTs cascaded with one 1-to-4 power divider and one 4-to-1 power combiner form a 4-way power combined PCB circuits. For combing the high power and driving an antenna, two PCB circuits are combined by magic-T waveguides. The transmission efficiency of the power combining is approximately 80%. In the 10% duty cycle (pulse width 100 us), the output power of the HPA is over 200 W across the band of 9.5–9.8 GHz. The maximum output power is 230 W at 9.5 GHz, and the power gain is 8.3 dB at 46.1°C.

This paper presents a triple-band low-noise amplifier (LNA) fabricated using a 0.18 μm Complementary Metal-Oxide-Semiconductor (CMOS) process. The LNA uses a double-peak load network with a switched component to accomplish the triple-band operation. Moreover, noise reduction using a substrate resistor to ameliorate the noise performance is presented. Noise reduction of 1.5 dB can be achieved at 2.5 GHz without additional dc power and extra manufacturing costs. An input matching technique is realized simultaneously using a gyrator-based feedback topology. The triple-band LNA can be realized by using a dual-band input network with a switched matching mechanism. The target frequencies of the triple-band LNA are 2.3–2.7 GHz, 3.4–3.8 GHz, and 5.1–5.9 GHz, covering the operating frequency bands of time-division long-term evolution (TD-LTE), mid-band Fifth-generation (5G), LTE-unlicensed (LTE-U) band, and Wireless LAN (WLAN) technology. The measured power gains and noise figures at 2.5, 3.5, and 5.2 GHz are 12.3, 15.3, and 13.1 dB and 2.3, 2.2, and 2.6 dB, respectively.

In this paper, a new low-profile smart multiple-input multiple-output (MIMO) antenna system is presented for WiFi IEEE 802.11a/b/g/n/ac/ax applications. The proposed compact 2.4-GHz antenna system employs two beam-switching antenna cells for MIMO operation. Each antenna cell is composed of four reconfigurable frequency-selective reflectors (RFSRs) and a one-to-four switching feeding network. The RFSRs are constructed using a one-wavelength metal loop resonator, which functions as a radiating antenna or a wave reflector to reflect beams along a specific direction, as controlled by the switching network. The feeding switching network utilizes PIN diodes to adjust the phase and impedance required for changing the operational status of each RFSR. The overall dimensions of the antenna system, including the metallic ground, are 120 mm ´ 120 mm ´ 9.5 mm. Moreover, the measured operational bandwidth of the 2.4-GHz antenna is approximately 100 MHz, and the radiation efficiency of each directed beam is 40%–70%.

An ultra-wideband (UWB) low-noise amplifier (LNA) implemented using 180 nm complementary metal-oxide-semiconductor technology is presented for wireless personal area network (WPAN) and wireless body area network (WBAN). Increasing the resistance of the substrate resistor R B reduces the noise factor. When additional substrate resistors and a composite feedback topology are employed, the proposed LNA can achieve both a 1.4 dB reduction of the noise figure (NF) and a 4 dB enhancement in power gain (PG). Over the operating frequency range from 3.1 to 4.8 GHz, the LNA achieves a maximum PG of 14.5 dB, a minimum NF of 1.5 dB, and an input return loss of

In automotive radar applications, a realistic road surface can cause multipath reflection, degrade the received power, and reduce detection probability. This paper proposes a one-transmitter–two-receiver (1T2R) 24-GHz frequency-modulation continuous-wave (FMCW) radar architecture with spatial diversity and ground effect compensation for automotive applications. A ray-tracing technique was developed to evaluate the multipath effect of the road surface. In the proposed design, suitable spacing between the two receiving antennas compensated for the multipath effect of the road surface and improved the signal-to-ground clutter ratio of the receivers by a minimum of 20 dB at certain distances. The measurement and calculation results of the proposed radar are in close agreement.

A novel filtering diplexing antenna for dual-band operation is presented. The antenna is composed of a slot-loaded patch and two resonators with a commonly used ground. Dog-bone-shaped slots are used on the ground for achieving broadside magnetic coupling and increasing the isolation between operating bands. The antenna design is based on a second-order Chebyshev bandpass filter synthesis. The proposed antenna exhibits high band-edge selectivity performance, low cross-polarization levels with half-power beamwidths greater than 86° for 2.4- and 5.2-GHz WLAN communication bands. The measured and simulated results are highly consistent.

In this paper, a CMOS multichannel transceiver (TRX) is proposed for angular identification in automotive car radar applications. Two transmitters (TXs) and six receivers (RXs) are placed on the same die using 65-nm CMOS technology with chip size $3.5 \times 3$ mm2. To generate a millimeter-wave (MMW) frequency-modulated continuous-wave signal, an injection-lock frequency sextupler cascaded a 1-to-8 Wilkinson power dividing network with wideband isolation is designed as the LO-chain to convert external source from 12.5–13.7 to 75–82.2 GHz for both the TXs and RXs. Each TX achieves above 11-dBm output power and the RXs achieve 30-dB conversion gain from 75 to 82 GHz, and the total power dissipation of whole chip is 1.43 W. Compared with other published multichannel TRXs in silicon germanium (SiGe) process, this paper demonstrates compatible performances and the potential of multichannel TRX using CMOS for MMW automotive car radar application.

This communication proposes a compact multiband antenna fed by microstrip coupling for handsets with conducting edge applications. The antenna is composed of a U-shaped loop, an inserted open-end T-shaped slot, and a feed line with a compact antenna area. Three types of resonant modes are excited, namely loop mode, slot mode, and monopole mode. Parametric studies have been performed. After the related parameters are controlled, the bandwidth of this antenna has the potential to cover the mobile bands of GSM (824–960 MHz), DCS (1710–1880 MHz), PCS (1850–1990 MHz), UMTS (1920–2170 MHz), LTE bands (FDD–LTE bands 1–10, 15, 16, 18–20, 22, 23, 25–27, and 30 and TDD–LTE bands 33–43). Good radiation characteristics, such as gain and radiation efficiency, are obtained with these operating bands. In addition, the structure of the inserted slot antenna reduced the user’s hand effects on the radiation efficiency.

A current-reused voltage-controlled oscillator (CRVCO) with amplitude-balanced technique is presented. A cascode cross-coupled pair is adopted, which is used to improve the difference between the differential output amplitudes of CRVCO at a 1.3 V supply voltage. The measured amplitude imbalance ratio is less than 0.15%. The measured phase noise is −114 dBc/Hz at 1MHz offset when oscillation frequency is at 7.8 GHz, resulting in an FOM of − 187dBc/Hz.

This communication proposes a compact U-shaped slot antenna with a coupling feed for 4G handset applications. The antenna is composed of a simple open-end U-shaped slot and a feeding line with an antenna area of 58 mm × 12 mm. Two types of resonant modes are excited, including slot mode and monopole mode. Parametric studies on the slot geometry have been demonstrated. By controlling the related parameters, the bandwidth of this antenna can potentially cover the mobile bands of LTE Band 12 (698-742 MHz)/DCS (1710-1880 MHz)/PCS (1850-1990 MHz)/UMTS (1920-2170 MHz)/LTE Band 40 (2300-2400 MHz)/Band 41 (2496-2690 MHz)/Band 42 (3400-3600 MHz)/Band 43 (3600-3800 MHz). Good radiation characteristics, like gain and radiation efficiency are obtained over these operating bands. This antenna is suitable for the metal casing of handheld devices.

A novel compact dual-band pattern diversity antenna is proposed. Dual-band reconfigurable frequency-selective reflectors are designed and applied to form a right-angle corner reflector antenna with reconfigurable patterns. With only one switch, the reconfigurable frequency-selective reflector can be controlled to be transmissive or reflective to vertically polarized waves at 2.45 and 5.25 GHz. By changing the combinations of the switch states, multiple patterns can be obtained. A dual-band feeding antenna designed via using the coupling effects is made to achieve well-matching conditions in all circumstances corresponding to various switch states at both frequencies. The measured results show good agreement with the calculated ones and demonstrate good pattern diversity virtues.

Two new compact planar triple-mode resonators embed- ded with inductive or capacitive cross coupling are proposed for band- pass fllter design. Both resonators consist of a shorted half-wave ring. In the flrst resonator, two shorted half-wave sections with inductive coupling are connected to the shorted via of the ring. In the second, two quarter-wave sections with capacitive coupling are connected. The inductive coupling is realized by a short grounded high-impedance seg- ment, and the capacitive coupling is implemented by an interdigital ca- pacitor. When both the inductive and capacitive coupling coe-cients are properly realized, a transmission zero can be created at designated position in either upper or lower stopband. The shorted ring is accom- modated inside the area of the other two resonance sections so that a compact area can be achieved. As compared with a conventional dual- mode ring resonator fllter, the proposed resonators use only 46.7% and 22.5% in area. Two triple-mode resonator bandpass fllters are fabri- cated and measured to validate the ideas. Measurement results have good agreement with the simulation responses.

A broadband impedance transformer is proposed for microstrip realization and to release the tight gap size (30 pm) required for coupled-stripline. Design curves of the transformer are obtained by solving the analytical equations derived from the transmission line theory. Two transformers are fabricated and measured. One is designed for a 1:2 ratio and return loss better than 30 dB over a fractional bandwidth Δ = 68%, and the other is a 1:2.8 transformer with |S11| < −25 dB over a bandwidth of Δ = 71%. In realization, the metal traces are folded so that the circuit sizes are less than λ/8×λ/8. Good agreement between measured and simulation is obtained.

Dual-mode ring resonator filters are implemented with asymmetric inductive perturbation for creating transmission zeros on both sides of the passband. In analysis, dependence of the resonance modes and the zeros on positions and sizes of both the inductive and capacitive perturbations is investigated. Under certain conditions, the even- and odd-mode frequencies for a capacitively perturbed ring are the same as the odd and even ones, respectively, for a ring with inductive perturbation. Theoretical background is clearly explained how the two transmission zeros are split up from the center frequency. Two dual-mode ring resonator filters are fabricated and measured for demonstration. To obtain a miniaturized circuit area, the 1-λ ring trace is folded into a double-ring or spiral configuration. The inductive perturbation is chosen as the crossover and implemented by a short high-impedance coplanar waveguide interconnection in the ground plane of the microstrip. Measurement results show good agreement with the simulation responses.

A compact S-band auto-tracking antenna feed for 6 m mono-pulse auto-tracking ground station is presented. It is designed to reduce the effect of blockage of the antenna systems and modify the orientation angle of the main reflector to align antenna boresight with a satellite. A circular waveguide is designed to connect to the septum polarizer for communication between the earth and LEO satellite. Based on the circular waveguide as an inner metal, a cylindrical metal is added as an outer metal to form a coaxial line for tracking LEO satellite. The uplink band of the antenna feed is from 2.025 to 2.12 GHz and the downlink band is from 2.2 to 2.3 GHz. The results show that the antenna gain of 6 m reflector is about 39.7 dBic and the 1-dB-beamwidth is 1 degree. The polarization isolation between sum and difference patterns is larger than 30 dB, and the axial ratio is lower than 1.1 dB within ± 0.5 degree range.

A novel compact filtering 180° hybrid utilizing coupled resonators is presented. The equivalent-circuit structure is just like a bandpass filter, thus the frequency response is filter-like. The sum and difference port operations respectively correspond to the symmetric and antisymmetric states; therefore, isolation between sum and difference ports is accomplished by geometrical symmetry. The synthesis method of the filtering 180° hybrid is illustrated. The proposed structure is decomposed into one power divider and one balun, which are designed separately. A second-order filtering 180° hybrid prototype centered at 2.4 GHz with 0.2-dB Chebyshev equal-ripple response and 10% fractional bandwidth is demonstrated. The passband insertion loss is about (3.0 + 0.7) dB, and the isolation between the sum and difference port is greater than 20 dB. Magnitude imbalance is less than 1 dB and phase imbalance is within 2°. Good agreement between simulation and experimental results is achieved.

A new filtering microstrip antenna array is presented. The antenna elements, together with the very compact feeding network, function as a third-order bandpass filter. The feeding network, which consists of one power divider and two baluns, provides the first two stages, and the microstrip antenna elements provide the last stage in the filter design. The equivalent lumped circuit model is analyzed, and the detail synthesis procedure is presented. A third-order filtering 2 × 2 microstrip antenna array is designed at a center frequency of 5 GHz with 3% fractional bandwidth and Chebyshev 0.3-dB equal-ripple broadside antenna gain response. The results from circuit model, full-wave simulation, and measurements agree well. Compared to the conventional patch antenna array, the proposed filtering microstrip antenna array successfully suppresses the unwanted signals in out-of-band, preserves good selectivity at band edges, and retains the flatness of the passband broadside antenna gain response.

A compact printed filtering antenna with high band-edge gain selectivity is presented. Occupying about the same substrate area as a conventional antenna, the proposed structure not only serves as a radiator but also a second-order bandpass filter, with one filter pole provided by a Γ-shaped antenna and the other by a newly proposed coupled line resonator. High band-edge selectivity is achieved due to two additional stop-band transmission zeros provided by the coupled line resonator. To minimize the required area and reduce the spurious radiation, a coupled line structure composed of a microstrip line and a coplanar waveguide by broadside coupling is adopted and intruded into the Γ-shaped antenna area. According to the filter specifications, a design procedure for the proposed filtering antenna is depicted in detail. One example at 2.45 GHz with a second-order Chebyshev bandpass filter of 0.1 dB equal-ripple response is tackled. As compared to the conventional Γ -shaped antenna, the proposed filtering antenna not only possesses a similar antenna gain but also provides better band-edge gain selectivity and flat passband gain response. The measured results, including the S-parameters, total radiated power, and antenna gains versus frequency, have good agreement with the designed ones.

Synthesis and design of a new printed filtering antenna is presented in this communication. For the requirements of efficient integration and simple fabrication, the co-design approach for the integration of filter and antenna is introduced. The printed inverted-L antenna and the parallel coupled microstrip line sections are used for example to illustrate the synthesis of a bandpass filtering antenna. The equivalent circuit model for the inverted-L antenna, which is mainly a series RLC circuit, is first established. The values of the corresponding circuit components are then extracted by comparing with the full-wave simulation results. The inverted-L antenna here performs not only a radiator but also the last resonator of the bandpass filter. A design procedure is given, which clearly indicates the steps from the filter specifications to the implementation. As an example, a 2.45 GHz third-order Chebyshev bandpass filter with 0.1 dB equal-ripple response is tackled. Without suffering more circuit area, the proposed structure provides good design accuracy and filter skirt selectivity as compared to the filter simple cascade with antenna and a bandpass filter of the same order. The measured results, including the return loss, total radiated power, and radiation gain versus frequency, agree well with the designed ones.

This letter introduces a coupling element to enhance the isolation between two closely packed antennas for 2.4-GHz wireless local area network (WLAN) application. The proposed structure occupies two antenna elements and a coupling element in between. By putting a coupling element that artificially creates an additional coupling path between the antenna elements, the antenna isolation can be enhanced. The advantage of this design is that no extra space is needed for antenna elements. With the proposed design, more than 15 dB isolation can be achieved for two parallel individual inverted-F antennas (IFAs) with 5-mm spacing. Parametric studies for the design are also included to show how to increase isolation bandwidth and control the isolation frequency.

Design, fabrication, and measurement of a compact filtering microstrip antenna with second-order quasi-elliptic broadside antenna gain response are presented. A U-shape radiating patch is excited by a T-shape resonator through an inset coupling structure. The U-shape patch acts as a radiator as well as the last stage of the filter, and the inset coupling structure can be treated as the admittance inverter in filter design. The design procedure follows the circuit approach-synthesis of bandpass filters. The broadside gain of the filtering antenna has two poles in passband and two broadside radiation nulls (zeros) at the band edges for improving selectivity. Compared to the conventional inset-fed microstrip antenna, with a little extra circuit area, the proposed filtering antenna has a flatter passband response, better frequency skirt selectivity, and almost twice wider bandwidth. The measurement result shows a good agreement with the simulations.

A novel wide-band printed antenna, named forked shape monopole antenna (FSMA), is proposed. The forked shape line structure is introduced to create a capacitive coupling effect to reduce the antenna size and enhance the impedance bandwidth. The proposed antenna is to be applied in a compact USB dongle. And it is designed for the reception of the digital video broadcasting (DVB) signal in the 470 ~ 860 MHz frequency band. In addition to the DVB application, the upper band limit of the FSMA even can be extended from 860 MHz to 1142 MHz, suitable for use in the Global System for Mobil Communication (GSM850/900). By employing the branched-line and forked shape configurations, an antenna with 86% impedance bandwidth (SWR

A novel configuration is described for a compact microstrip-line fed slot antenna which is shorter than one-eighth wavelength at the operating frequency. Antenna size is reduced by placing two matching capacitors at both sides of an electrically small open-end slot, through the use of a wideband antenna equivalent circuit model established by considering the physical geometry. With the proposed antenna configuration, a 2.45 GHz slot antenna is first designed using an open-end slot of size 9 mm by 1.5 mm that is originally resonant at 4.8 GHz in a conventional design. Experimental results correlate well with those of the full-wave simulation and the equivalent circuit calculation, which shows a bandwidth of 109 MHz and peak gain of 1.89 dBi. By using the same slot size, several slot antennas operating at even lower frequencies (1.9, 1.64, 1.57 GHz) are then designed and demonstrated. Nearly omni-directional radiation patterns with peak gains 0 dBi and radiation efficiencies larger than 45% are obtained. Given its simplicity and compactness, the proposed electrically small antenna is feasible for circuit integration and highly promising for wireless mobile devices.

Two 3-5-GHz low-power ultra-wideband (UWB) low-noise amplifiers (LNAs) with out-band rejection function using 0.18- ?m CMOS technology are presented. Due to the Federal Communications Commission's stringent power-emission limitation at the transmitter, the received signal power in the UWB system is smaller than those of the close narrowband interferers such as the IEEE 802.11 a/b/g wireless local area network, and the 1.8-GHz digital cellular service/global system for mobile communications. Therefore, we proposed a wideband input network with out-band rejection capability to suppress the out-band properties for our first UWB LNA. Moreover, a feedback structure and dual-band notch filter with low-power active inductors will further attenuate the out-band interferers without deteriorating the input matching bandwidth in the second UWB LNA. The 55/48/45 dB maximum rejections at 1.8/2.4/5.2 GHz, a power gain of 15 dB, and 3.5-dB minimum noise figure can be measured while consuming a dc power of only 5 mW.

The design is described of a very compact quadrifilar helix antenna. A hollow ceramic rod is used as a dielectric load to reduce antenna size, which is only 2.7% of an air-loaded quadrifilar helix antenna. A simple equivalent circuit is established for the proposed quadrifilar helix antenna to demonstrate impedance characteristics. A self-phasing method for achieving circular polarization is also proposed. This method is convenient for tuning circular polarization. Additionally, a compact matching structure is designed to match the proposed antenna, which only utilizes short transmission-line sections and one capacitor. For experiments, the proposed antenna is designed at 1.575 GHz such that it can be utilized for global position system. Measurement and simulation results agree. A hemispherical pattern with a beamwidth of 150deg is measured. This circular-polarized pattern with a wide beamwidth is feasible for mobile applications.

In this communication, we propose a simple and compact printed ultrawideband (UWB) antenna. The antenna is mainly composed of a monopole section and a quasi-transmission line section. The input signal from the feed line first passes through the line section then enters the monopole. The quasi-transmission line section provides different functions as the operating frequency changes. It serves not only as an impedance matching circuit but also a main radiator, which leads to the UWB performance of the antenna. The resonance mechanisms across the full band are described, followed by a thorough study of the antenna's geometrical parameters.

A radiation pattern diversity reflector antenna is investigated. Novel switchable frequency selective reflectors are designed and developed to construct a square corner reflector antenna. By controlling a switching device on the frequency selective reflector, one can make it opaque or transparent to a vertically polarized incident wave. This antenna is fed by a monopole. By configuring the switch states of the frequency selective reflectors, various beam shapes can be formed and steered. Measured results of the antenna show good agreement with the calculated ones.

A 2-11-GHz high linearity CMOS down-conversion mixer with wideband active baluns using 0.18-mum CMOS technology is demonstrated in this paper. The mixer employs a folded cascode Gilbert cell topology and on-chip broadband active baluns. The folded cascode approach is adopted to increase the output swing, and the linearity is enhanced by a harmonic distortion canceling technique derived from the harmonic balance analysis. The proposed configuration shows the highest IIP3 and IP1 dB, and exhibits more compact size than most published studies. A broadband active balun is used to generate wideband differential signals, together with the derivation of a closed-form expression for the phase imbalance. This single-ended wideband mixer has the conversion gain of 6.9plusmn1.5 dB, input 1-dB compression point (IP1 dB) of - 3.5 dBm, single-sideband noise figure of 15.5 dB, and third-order input intercept point (IIP3) of 6.5 dBm under the power consumption of 25.7 mW from a 1.8-V power supply. The chip area is 0.85 x 0.57 mm2.

We propose a miniaturized microwave current choke for blocking the current flowing along the edge of a substrate's ground plane. The proposed current choke is composed of a printed inductor and a printed capacitor, which possesses a size much smaller than a conventional quarter-wavelength current choke. By introducing the choke at one side of the ground plane, an effective electrical open circuit is performed for reflecting the ground edge current. The size of the proposed ground edge current choke (GECC) is as small as around 0.06 wavelength in free space. Two applications of the GECC are presented in this paper. The first is the radiation pattern regulation of a printed monopole antenna with long ground plane. The GECC in this application reflects the induced traveling-wave current along the ground plane edge and changes it to a standing-wave one, thus regulating the tilted radiation pattern due to the traveling-wave current to a broadside pattern. The other application is the decoupling of two nearby monopole antennas. By placing the proposed compact GECC in between the antennas, it is found that the isolation between the antenna ports can be enhanced from 8 dB to 32 dB. The experimental results agree well with the simulation, which demonstrate the feasibility of the proposed GECC.

SUMMARY This paper proposes a new circuit-fed 2-D amplifying array architecture using the multi-ported aperture-coupled patch antennas. The power distribution achieved by this array is formed by stacking three kinds of basic cells repeatedly. Each cell, which serves as a radiator and also a power relay, has a multi-ported patch antenna and one or two amplifiers. The signal transmission coefficient of the cell from the input port to the output port is designed with a power level of 0 dB and a phase of 360 ◦ .A n X-band 4× 3 element array with uniform amplitude distribution is demonstrated. The measured results, such as the antenna gain and the radiation patterns, agree very well with the predicted ones, due to the precision design of the basic cells. The measured gain of the antenna array is 27.7 dBiA at the frequency of 10.4 GHz on the H-plane, with a half-power beamwidth of 14 ◦ in the H-plane and 16 ◦ in the E-plane.

A compact decoupling network for enhancing the port isolation between two closely spaced antennas is proposed in this paper. In the network, we first connect two transmission lines (TLs) individually to the input ports of two strongly coupled antennas. The length of the TLs is designed so that the trans-admittance between ports changes from a complex one at the antenna inputs to a pure imaginary one. A shunt reactive component is then attached in between the TL ends to cancel the resultant imaginary trans-admittance. Finally, a simple lumped-element circuit is added to each port for input impedance matching. The even-odd mode analysis is adopted to investigate the currents excited on the antennas for predicting the radiation pattern of the two-element antenna array. Two examples of printed antennas at 2.45 GHz are tackled by using the proposed decoupling structure. The measurement results agree quite well with the simulation ones. High antenna isolation and good input return loss are simultaneously achieved in both cases, which demonstrates the feasibility of the structure. The decoupled antenna array in each example radiates, as prediction, toward different but complementary directions when the input power is fed in turn to the two input ports. The array efficiency is estimated better than 75% in each example. This pattern diversity effect is helpful for reducing the channel correlation in a multiple-input multiple-output (MIMO) communication system.

This study proposes a compact 5-GHz front-end module with embedded antenna on a low-temperature co-fired ceramic substrate, which is to be used for the IEEE 802.11a wireless local area network applications. The module comprises an embedded inverted-F antenna, a bandpass filter, and a low-pass filter. Both the proposed filters possess transmission zeros at out band for suppressing unwanted signals. A double-pole double-throw bare die transmitting/receiving switch is mounted on the surface of the substrate. The interconnection between the bare die switch and the buried circuits is established by bond wires. The effect of the bond wire is considered by incorporating its equivalent inductance into the design of the filters. The overall size of the antenna front-end module is only 6.2 mm times 5.4 mm times 0.98 mm with most of the space (near two-thirds of the volume) reserved for the antenna so as to have a better radiation performance. Also, to avoid the potential close proximity coupling among the buried circuits and the antenna, numerous metal vias connecting the top and bottom grounds in the module are designed for shielding. Since the radiation of a small antenna is influenced by the nearby circuit ground due to induced ground current, the developed antenna front-end module is tested on two FR4 printed circuit boards (PCBs) with different sizes (i.e., 55 mm times 20 mm and 80 mm times 46 mm). It is demonstrated that the antenna module performs well on these two grounded PCBs. The achieved 10-dB return-loss bandwidths are near 900 MHz for the transmitting and receiving paths. The measured radiation patterns are quite omnidirectional with peak gains (including the losses of circuit components) at approximately 0 dBi for the transmitting path and -1.7 dBi for the receiving path.

A systematic model-parameter-extraction technique is presented for accurately modeling on-chip spiral inductors in radio frequency integrated circuits (RFICs). The model is a pi-circuit with an additional parallel RC network connecting both vertical branches to account for substrate coupling. The extraction starts with extracting the series inductance and resistance at low frequencies. Then, the oxide capacitance is evaluated in an intermediate frequency range. Afterward, the substrate effects including the substrate resistance and capacitance, as well as coupling, are extracted at higher frequencies. All the lumped circuit element values are analytically determined by the network analysis from the measured network parameters (S- or Y-parameters). The proposed approach thus can provide better circuital interpretations of the inductor behaviors for facilitating the design of RFIC inductors. Square and circular CMOS spiral and octagonal BiCMOS7 spiral inductors are investigated to test this technique. Highly accurate frequency responses by the extracted parameters are obtained over a wide frequency band without any optimization. This reveals the validation and capability of the proposed parameter-extraction method.

A dual-mode folded microstrip reflectarray antenna was developed and demonstrated in this paper. The proposed folded reflectarray antenna contains three parts: a planar main reflector, a planar subreflector, and printed feed antennas. The main reflector is used to produce twisted reradiated fields and to provide phase compensation for focusing. The subreflector parallel with the main reflector is made of a substrate printed with high-density metal grid lines, which is transparent to perpendicularly polarized fields, but would reflect the parallel ones. Three fixed-position patch antennas with polarization parallel to the grid lines are created for the radar mode, so that the radiation beam is switchable. Another patch with perpendicular polarization is designed for communication. A simple approach was proposed for simulating and designing the folded reflectarray. Measured results show good agreement with the calculated ones.

A novel compact planar antenna utilizing cascaded right/left-handed transmission lines is proposed. The significance of layout planning with respect to radiation is investigated and discussed in this paper. Two segments of transmission lines of the same electrical length with opposite signs are cascaded to provide zero phase at the operation frequency. The closed-form formulas for the equivalent circuit of a transmission line are used for circuit design. Both antenna layout and radiation mechanism are discussed. For experimental demonstration, the proposed antenna operating at 2.45 GHz was implemented on an FR4 substrate. The topology using several patches has quite smaller size than the conventional patch antenna. Besides, a fairly omnidirectional radiation pattern was measured.

A novel planar ultrawideband (UWB) antenna with band-notched function. The antenna consists of a radiation patch that has an arc-shaped edge and a partially modified ground plane. The antenna that makes it different from the traditional monopole antenna is the modification in the shape of ground plane, including two bevel slots on the upper edge and two semicircle slots on the bottom edge of the ground plane. These slots improve the input impedance bandwidth and the high frequency radiation performance. With this design, the return loss is lower than 10 dB in 3.1-10.6 GHz frequency range and the radiation pattern is highly similar to the monopole antenna. By embedding a pair of T-shaped stubs inside an elliptical slot cut in the radiation patch, a notch around 5.5 GHz WLAN band is obtained. The average gain is lower than -18 dBi in the stopband, while the patterns and the gains at frequencies other than in the stopband are similar to that of the antenna without the band-notched function.

An on-package planar inverted-F antenna (PIFA) is described. The on-package PIFA consists of a single folded metal plate and has several advantages, including small size, light weight, low cost, and ease of fabrication. The antenna radiation pattern is omnidirectional in the H-plane. The coupling effect between the on-package PIFA and the radio-frequency (RF) components in the shielding package was studied. The antenna performance rarely changes and the isolation between the antenna and the RF components can be maximized when the locations of the components are appropriately arranged in the package. Finally, a wireless local-area network (WLAN) front-end module (FEM) including the switch, low-pass filter (LPF), bandpass filter (BPF), and power amplifier (PA), is embedded into the shielding package of the antenna. The error vector magnitude (EVM) of the resultant antenna integrated FEM, together with a WLAN card containing the baseband/medium-access control (MAC) circuitry, is tested. Good performance is obtained, showing the usability of the proposed antenna configuration.

There are two novel printed inverted-F antenna (PIFA) related dual-band antennas for 2.45 and 5.25 GHz wireless local area network (WLAN) applications introduced in this paper. One is designed by spiraling the tail of the PIFA and the other is by modifying the feed structure of the PIFA into a coupling configuration. An equivalent transmission line model is proposed to explain the dual-band operation of the spiraling PIFA. The measurement results show that the former antenna has a 10 dB return loss with bandwidth 140 MHz in the 2.45 GHz frequency band and bandwidth 756 MHz at 5.25 GHz, whereas the latter one has the bandwidth 240 MHz at 2.45 GHz and bandwidth 672 MHz at 5.25 GHz. In addition, omnidirectional radiation patterns are achieved at those operating frequency bands with average antenna gains near 0 dBi. The proposed antenna possesses the properties of good performance, compact size (about 50% of a typical PIFA), low profile, and low cost; hence, it is suitable for practical applications in a combo WLAN system

Investigations into a surface that reflects one sense of circularly polarized electromagnetic wave but transmits the other, namely a circular-polarization selective surface (CPSS), were carried out. This paper presents CPSS using simple planar structure without any vertical conductive segments. Couplings, through the use of L-shaped traces, were produced to replace the vias. Operational principle and design procedure are developed, thus the optimal design parameters are found. Also presented are the results of numerical computations and measurements for "isolation" and "transmission loss". A 30 GHz example demonstrates the performances of the design and the attractiveness in millimeter-wave circular polarization selectivity applications

This paper shows the design of a broadband single-end low noise amplifier for UWB system with TSMC 0.18 μm CMOS processes. The proposed amplifier achieves broadband input matching by cascode feedback topology with parallel resonate cavity and the bandwidth is from 3.1 GHz to 10.1 GHz. The simulation results are as follows: 12 ± 1 dB of gain, the input/output return loss are greater than 10 dB, minimum noise figure is about 3.3 dB, and 1 dB gain compression point is about −15 dBm. The total current consumption included bias network is 9.1 mA under a 1.8V single supply voltage. Chip area is 0.8mm× 0.8mm. DOI: 10.2529/PIERS061005190725

A dual-bandpass filter that utilizes a serial configuration of the inductive coupled-line (ICL) filter and the capacitive coupled-line (CCL) filter is investigated in this study. Numerical analysis is presented for the difference between the ICL and CCL filters. The dual-bandpass filter has a similar behavior to the individual single-band filter around the corresponding passband. An extra transmission zero can be generated between the two passbands of the dual-bandpass filter in that the ICL and CCL filters exhibit an out-of-phase response. Four architectures of dual-bandpass filters are proposed for the 2.4/5-GHz systems. Two of them are demonstrated by the low-temperature co-fired ceramic multilayer technology. Measurements results agree quite well with the simulation ones