Phirun Kim

Ultra-High Transforming Ratio Coupled Line Impedance Transformer With Bandpass Response

An impedance transformer (IT) with a ultra-high impedance transforming ratio (UHITR) is presented in this letter. The UHITR is obtained by controlling coupling coefficients of cascaded open-circuited coupled lines. Two transmission poles have appeared in the passband for an under-matched region. For the validation, the IT with impedance transforming ratio of 10 was designed at a center frequency (f0) of 2.6 GHz. From the experiment, insertion and return losses at f0 were determined as 0.55 dB and 21.47 dB, respectively. Within the operating band from 2.515 to 2.73 GHz, the insertion and return losses were better than 0.8 dB and 18 dB, respectively. The out-of-band suppression characteristics are higher than 20 dB from dc to 1.92 GHz and better than 18 dB from 3.28 to 7.2 GHz.

A DUAL-BAND RF ENERGY HARVESTING USING FREQUENCY LIMITED DUAL-BAND IMPEDANCE MATCHING

In this paper, a novel dual-band RF-harvesting RF-DC converter with a frequency limited impedance matching network (M/N) is proposed. The proposed RF-DC converter consists of a dual-band impedance matching network, a rectifler circuit with villard structure, a wideband harmonic suppression low-pass fllter (LPF), and a termination load. The proposed dual-band M/N can match two receiving band signals and suppress the out-of-band signals efiectively, so the back-scattered nonlinear frequency components from the nonlinear rectifying diodes to the antenna can be blocked. The fabricated circuit provides the maximum RF-DC conversion e-ciency of 73.76% and output voltage 7.09V at 881MHz and 69.05% with 6.86V at 2.4GHz with an individual input signal power of 22dBm. Moreover, the conversion e-ciency of 77.13% and output voltage of 7.25V are obtained when two RF waves with input dual-band signal power of 22dBm are fed simultaneously.

Compact negative group delay circuit using defected ground structure

A novel design of compact negative group delay circuit (NGDC) using U-shaped defected ground structure (DGS) is presented in this paper. The required group delay (GD) time can be controlled by an external resistor connected across the DGS slot. For experimental verification, a single stage NGDC is designed, fabricated, and compared with a circuit simulation. To enhance NGD bandwidth, two stages NGDC with the different center frequencies in cascade are demonstrated and GD of -3.8 ns with maximum signal attenuation of 37.10 dB was obtained on 3.45-3.55 GHz.

A design of negative group delay power divider: Coupling matrix approach with finite unloaded-Qu resonators

In this paper, a novel approach to design a power divider with the predefined negative group delay (NGD) is presented. The proposed topology is based on a coupling matrix with a finite unloaded quality factor (Qu) of resonators, which does not require any lumped elements such as resistor for generating NGD. The NGD bandwidth and magnitude flatness can be controlled by inter-resonating couplings. As an experimental illustration, a microstrip line NGD power divider is designed and fabricated at center frequency of 2.14 GHz. The measurement results are in good agreement with simulations.

High Selectivity Coupled Line Impedance Transformer with Second Harmonic Suppression

This paper presents a design of an impedance transformer (IT) with high frequency selectivity characteristics. The frequency selectivity can be controlled by even- and odd-mode impedance of a shunt coupled transmission line (TL). For experimental validation, a 50- to 20- Ω IT was implemented at a center frequency (f0) of 2.6 GHz for the long-term evolution signal. The measured results were in good agreement with the simulations, showing a return loss higher than 19 dB over a passband bandwidth of 0.63 GHz (2.28–2.91 GHz) and good sharp frequency selectivity characteristic near to the passband. The series coupled TL provides a transmission zero at 5.75 GHz, whereas the shunt coupled TL provides three transmission zeros located at 2 GHz, 3.1 GHz, and 7.14 GHz.

High frequency-selectivity impedance transformer

This paper presents the design of an impedance transformer (IT) with high selectivity and wide out-of-band suppression characteristics. The proposed IT provides two transmission poles in the passband and a sharp frequency selective characteristic. For validation, a 50-to-20 Ω IT has been implemented at a center frequency (f0) of 2.6 GHz. The measurement results show a return loss higher than 20 dB over the passband of 2.2-3 GHz and the insertion loss less than 0.4 dB over the same passband. The out-of-band suppression higher than 17 dB from DC to 1.85 GHz and higher that 11 dB from 3.5 GHz to 7.2 GHz are obtained.

Negative Group Delay Circuit with Improved Signal Attenuation and Multiple Pole Characteristics

This paper presents a design of a transmission line negative group delay (NGD) circuit with multiple pole characteristics. By inserting an additional transmission line into a conventional NGD circuit, the proposed circuit provides further design parameters to obtain wideband group delay (GD) and to help reduce signal attenuation. As a result, the number of gain compensating amplifiers can be reduced, which can contribute to stable operation when integrated into RF systems. The multiple pole characteristics can provide wider NGD bandwidth and can be obtained by connecting resonators with slightly different center frequencies separated by quarter-wavelength transmission lines. For experimental validation, an NGD circuit with two poles GD characteristic is designed, simulated, and measured.

Unequal termination impedance parallel-coupled lines band-pass filter with arbitrary image impedance

Abstract This paper presents an analytical design for a microstrip parallel-coupled line bandpass filter (BPF) with arbitrary termination and image impedances. Using the proposed design formulas, multistage arbitrary termination impedance BPFs can be designed with a very high impedance transforming ratio (r). The fractional bandwidth and return losses are maintained even though the r and image impedance are varied. To validate the design formulas, two- and three-stage BPFs are fabricated and measure at the center frequency (f0) of 2.6 GHz. The filter 1 and filter 2 are designed with termination impedances of 50–300 Ω and 20–50 Ω, respectively. The measured results of both filters show a good agreement with the simulations. The measured passband insertion and return losses of filter 1 are better than 0.8 and 19.6 dB, respectively. Similarly, the measured passband insertion and return losses of filter 2 are better than 1.5 and 19 dB, respectively.

A power divider with positive and negative group delay characteristics

In this paper, a power divider is suggested for predefined positive and negative group delay characteristics. The positive group delay (PGD) is obtained in between transmission paths 2 and 1, whereas the negative group delay (NGD) is in between transmission paths 3 and 1. The PGD and NGD are controlled by characteristic impedance of horizontal transmission line Z1 and shunt resistor R. Perfect input and output matching characteristics as well as perfect isolation are obtained at a center frequency (f0). For an experimental demonstration, microstrip line power divider with the PGD and NGD of 0.6 and -0.5 ns, respectively, was designed and fabricated at f0 of 2.14 GHz. The measurement results are agreed well with simulation results and theoretical predicated values.

Power divider with tunable positive and negative group delays using parasitic compensated PIN diode

This paper presents a design of power divider with tunable positive and negative group delays. The positive group delay can be obtained between paths 2 and 1 whereas negative group delay (NGD) between paths 3 and 1. The NGD is controlled by varying bias voltage of parasitic compensated PIN diodes. For experimental verification, power divider was designed and fabricated at center frequency of 2.14 GHz. Measurement results had a good agreement with simulation results.