Kwok-Keung M. Cheng

A New Wilkinson Power Divider Design for Dual Band Application

This letter presents the design of a new Wilkinson power divider for dual-band application. The proposed circuit also features a simple structure, low loss (distributed element only) and exact solution (ideal characteristics). For verification, the measured results of a microstrip power divider operating at 1 and 2.6 GHz are shown.

A Novel Approach to the Design and Implementation of Dual-Band Power Divider

This paper presents the design of a new Wilkinson power divider for dual-band application. The proposed circuit also features a simple structure with realistic impedance values, distributed design with reduced parasitic effect (in compared to lumped component), and exact solution (ideal characteristics). Closed-form design equations are derived using the even-and odd-mode formulation. For verification, the measured results of a microstrip power divider operating at 1 and 2 GHz is shown.

A novel rat race coupler design for dual-band applications

This letter presents a novel and compact rat-race coupler design that can operate at two widely separated frequency bands. It is accomplished by modifying the length and impedance of the branch lines in the conventional structure, and the insertion of two additional shunt stubs. The proposed circuit also features planar structure and low insertion loss. For verification, the measured performance of a microstrip coupler operating at 900/2000MHz are shown.

A Novel Power-Divider Design With Unequal Power-Dividing Ratio and Simple Layout

This paper presents the design of a novel power-divider circuit with an unequal power-dividing ratio. Unlike the conventional approaches, the characteristic impedance values of all the branch lines involved are independent of the dividing ratio. The electrical lengths of the line sections are the only circuit parameters to be adjusted. Moreover, the proposed structure does not require impedance transformers at the two output ports. By the introduction of a transmission line between one of the output ports and the isolation resistor, a flexible layout design with reduced parasitic coupling is achieved. For verification, the measured results of a 2 : 1 and a 4 : 1 power-divider circuits operating at 1 GHz are given. A relative bandwidth of over 20% is obtained based on a return loss and port isolation requirement of -20 dB.

Novel dual-band planar resonator and admittance inverter for filter design and applications

This paper presents, for the first time, the design of planar resonators and admittance inverters that can operate at two widely separated frequency bands. Design equations of the proposed structure and its application to pass-band filter design are given. These building blocks feature dual-band operation, compact planar design and low-insertion loss. For demonstration, the measured results of a dual-band microstrip filter operating at 900 & 2000 MHz based on the proposed configuration are shown.

Theoretical and experimental study of amplifier linearization based on harmonic and baseband signal injection technique

This paper presents a novel linearization scheme for RF amplifiers based on simultaneous harmonic and baseband signal injection. In this method, second-order frequency components generated by predistortion circuits are fed to the input of the main amplifier to mix with the fundamental signal for third-order intermodulation distortion (IMD) cancellation. A general and rigorous analytical formulation of baseband, harmonic, and the proposed injection techniques is presented, and from these derived expressions, the optimum conditions for IMD suppression are developed. The result also reveals the practical limitation of the proposed method subject to gain and phase error associated with the RF and baseband circuitry. For comparison purposes, an amplifying system is constructed for the experimental investigation of second-order signal injection approach. Both two-tone and digitally modulated waveforms are employed in these measurements.

A New Approach to the Realization of a Dual-Band Microstrip Filter With Very Wide Upper Stopband

This paper presents the design of a new dual-band filter with very wide upper stopband. The proposed circuit offers a simple and compact structure with low insertion loss. Spurious suppression is achieved by using specially designed coupling and resonator sections. Moreover, a systematic analysis is applied to the proposed topology with closed-form design equations derived. For verification purposes, the measured performance of a microstrip filter operating at 1 and 2 GHz is shown with stopband attenuation of greater than 20 dB over the frequency range from 2.5 to 8.0 GHz.

CMOS mixer linearization by the low-frequency signal injection method

This paper presents, for the first time, the application of low-frequency signal injection technique to the linearization of a doubly balanced dual gate mixer. The down-conversion mixer is fabricated using 0.35 /spl mu/m CMOS technology and is designed to operate at 900 MHz RF input frequency with good port-to-port isolation, low LO power and current consumption. Reduction of third-order intermodulation distortion (IMD) level of almost 20 dB is achieved by the proposed scheme.

Dual-band Rat-Race Coupler with Bandwidth Enhancement

This paper presents the novel design of a dual-band rat-race coupler with enhanced bandwidth. This is accomplished by the insertion of two additional shunt stubs for bandwidth optimization. The proposed circuit features planar structure, low insertion loss and no via-hole required. For demonstration, the measured performance of a microstrip rat-race coupler operating at 2.45/5.8 GHz is shown. An improvement in bandwidth of 50-100% is achieved with line impedance ranging from 40-90 Omega

Low phase-noise integrated voltage controlled oscillator design using LTCC technology

This paper describes the design and implementation of a highly integrated voltage controlled oscillator (VCO) module based upon Low-Temperature Co-fired Ceramic (LTCC) packaging technology. The circuit is realized by embedding the strip-line resonator and lumped passives inside a multilayer LTCC substrate. Measurement results of a silicon bipolar VCO circuit operating at 2.4 GHz is shown. The constructed module is compact in size and has good phase noise performance.