2010 IEEE MTT-S International Microwave Symposium Technical Program

Session: WEPA	Development in Signal Geneation
Chair:	Scott Wetenkamp, SCEAN

WEPA-1	Impact of Radiated EMI in High Frequency Crystal Oscillator
3:00 PM-5:00 PM	U. L. Rohde², A. K. Poddar¹, ¹Synergy Microwave Corp., Paterson, United States, ²University of Cottbus, Cottbus, Germany
(1176)	The high frequency (HF) crystal oscillator is susceptible to electromagnetic interference (EMI), which affects the stability or accuracy of reference frequency standards. The effect of radiated EMI can be both deterministic and random in nature that shows up as jitter in the time domain and phase noise in the frequency domain. In this paper, we studied the impact of radiated EMI in 155.6 MHz crystal oscillator (XO) and the design consideration for EMI and jitter insensitive signal sources for reference frequency standard applications. Experimental results and CAD simulated data provides insight into observed characteristics (mode-jumping, sub-harmonics and jitter, and validated with the design example of 155.6 MHz crystal oscillator circuits. Although, the likelihood of frequency shift in a noisy electromagnetic environment is far higher, however, this paper reports the mode-coupled phase-injected techniques to restrict the frequency shift and also minimizes the phase noise by 8-10 dB.

WEPA-2	Time-Filtered Squarewave Output from Direct Digital Synthesis
3:00 PM-5:00 PM	E. W. McCune, RF Communications Consulting, Santa Clara, United States
(1373)	To achieve a squarewave output from a direct digital synthesizer (DDS) without analog signal processing, the lower order bits in the DDS accumulator are used to properly position the rising and falling edges of the accumulator most significant bit (MSB). A digital technique called “time filtering” is proposed to individually manipulate each rising and falling edge on the accumulator MSB. This technique is shown to achieve the design goals. Design parameters necessary to meet spurious suppression requirements are presented.

WEPA-3	Frequency-tunable High-Efficiency Power Oscillator using GaN HEMT
3:00 PM-5:00 PM	S. Shin, G. Choi, H. Kim, S. Lee, S. Kim, J. Choi, Kwangwoon University, Seoul, Republic of Korea
(1695)	In this paper, a frequency tunable, high-efficiency power oscillator using GaN HEMT for the RF power source applications is presented. The steady state oscillation occurs in a delay line feedback loop which length is adjusted to tune oscillation frequency. A harmonic-tuned matching network is employed to obtain high conversion efficiency of the oscillator. The measured output power and conversion efficiency of the fabricated oscillator are 44.63±0.2 dBm and better than 62%, respectively, across the 890-950 MHz band with a drain bias voltage of 40 V. Then a hair-pin resonator is employed into the oscillator to improve phase noise characteristics and frequency selectivity. The experimental results of the oscillator with the hair-pin resonator exhibit the output power of 43.55 dBm, corresponding to the conversion efficiency of 61% at 920 MHz. The measured phase noise characteristics are -64 dBc/Hz and -81.24 dBc/Hz at 10 kHz offset without and with the hair-pin resonator, respectively.

If you encounter any problems, please contact