An ultra-broad-band reflection-type phase shifter is proposed. Theoretically, the proposed phase shifter has frequency-independent characteristics in the case of 180 phase shift. The phase shifter is composed of a 3-dB hybrid coupler and a pair of novel reflective terminating circuits. The reflective terminating circuit switches two states of series and parallel LC circuits. Using an ideal circuit model without parasitic circuit elements, we have derived the determining condition of frequency independence of circuit elements. Extending the concept, we can also obtain a broad-band phase shifter for other phase difference as well. In this case, for a given phase difference and an operating frequency, we also derive a condition to obtain minimum variation of phase difference around the operating frequency. This enables the broad-band characteristics for arbitrary phase difference. The fabricated 180 reflective terminating circuit monolithic microwave integrated circuit (MMIC) has achieved a phase difference of 183 3 over 0.5-30 GHz. The 180 phase-shifter MMIC has demonstrated a phase shift of 187 7 over 0.5-20 GHz. The 90 reflective terminating circuit MMIC has performed a phase difference of 93 7 over 4-12 GHz.

No abstract

This paper reports on the excellent performance of V -band monolithic high electron-mobility transistor (HEMT) oscillators, and discusses oscillation characteristics on drain bias. With regard to output characteristics, double-hetero (DH) HEMT (especially with a high-density Si-planar doped layer) are superior to single-hetero (SH) HEMT's. A monolithic microwave integrated circuit (MMIC) oscillator has been developed with a planar doped DH HEMT and has achieved the peak output power of 11.1 dBm at a 55.9-GHz oscillation frequency. Phase noise of 085 dBc/Hz at 100-kHz offset and 0103 dBc/Hz at 1-MHz offset have been achieved at a drain voltage of 5.5 V and a gate voltage of 0 V. These characteristics have been achieved without any buffer amplifiers or dielectric resonators. This study has revealed that the phase noise decreases as drain voltage increases. This phenomenon is caused by lower pushing figure and lower noise level at a low-frequency range obtained under a high drain voltage. It is because the depletion layer in the channel is extendedto the drain electrode with increase of drain voltage, resulting in the small fluctuation of the gate-to-source capacitance. We also investigate low-frequency noise spectra of AlGaAs/InGaAs/GaAs DH HEMT's with different bias conditions. The low-frequency noise decreases for more than 3 V of the drain voltage. A unique mechanism is proposed to explain this phase noise reduction at high drain voltage.

This paper describes two GaAs HBT MMIC power amplifier modules (PAs) for 2.5-GHz-and 3.5-GHz-band Wi-MAX applications. Each amplifier module integrates a fully 50-Ω input/output matched three-stage amplifier, a 0/20-dB step attenuator, an attenuator controller, and an RF detector together with all bias circuits, featuring on-module full integration. The step attenuator operating with high power handling capability, low-distortion, and low-bias current is placed between the first and second stages, thereby suppressing the change of the input return loss between thru and attenuation modes.With the 4.5 mm x 4.5 mm small-size module, optimized circuit design approaches lead to the following good measurement results under the 6-V supply voltage and WiMAX modulation (64QAM) test condition. The 2.5-GHz-band PA is capable of delivering a high gain (G p ) of over 31.9 dB, EVM of less than 2.1%, and PAE of more than 13.4% at a 28-dBm high output power (P out ). For the 3.5-GHz-band PA, a high G p of over 28.1 dB, EVM of less than 2.4%, and PAE of over 11% are achieved at a P out of 28 dBm.

No abstract