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This paper presents a compact size frequency doubler using an artificial transmission line design approach. The multiplier features conversion gain and high fundamental signal rejection. The frequency multiplying is employing the current combining push-push technique. Two GaAs FETs are driven by 900 MHz anti-phase signals from a simple LHM-TL phase shifter instead of the conventional balun/power divider. The transistor can be loaded directly onto the input and output port of the LHM-TL phase shifter since FETs virtually need no input power. The experimental results show the excellent agreements between the design and ADS ® simulations. The frequency doubler has a conversion gain of 5 dB and 30 % of size reduction compare to the conventional transmission line/hybrid circuit implementation.

This paper presents a new dual-mode microstrip ring bandpass filter (BPF) based on the left-handed transmission line (LH-TL). To achieve dual-mode response, a high impedance LH-TL can easily be realized to perturb a pair of degenerate modes, which difficulty is realized in the conventional dual-mode ring filter. The proposed BPF is designed and fabricated on an FR-4 substrate to suit the 2.45GHz ISM band application with a fractional bandwidth of 16.2 percentages. Across the bandwidth, the measured insertion loss is less than 1.5dB, whereas the input and output return losses are better than 20dB from 2.37 to 2.59GHz. The measured results are in good agreement with the simulated results.