Xiaofa Zhang

Compact dual-band microstrip bandpass filter using stub-loaded stepped-impedance resonator

In this paper, two dual-band microstrip bandpass filters (BPFs) based on the stepped-impedance resonator (SIR) and stub-loaded SIR (SL-SIR) are presented. The characteristics of the SL-SIR are studied by using the even-/odd-mode analysis method. The simulation results show the length of the loaded stub has no influence on the odd-mode resonant frequency, but it can affect the even-mode resonant frequency. In addition, the BPF based on the SL-SIR has higher frequency selectivity and stopband rejection than the one based on the SIR. Whats more, the loaded stub can reduce the size of the BPF. Therefore, the BPF based on the SL-SIR can be applied in the modern wireless communication systems.

Design of X-band low phase noise and low spurious frequency source based on HMC778

For X-band radar velocity measurement system, a low phase noise and low spurious frequency source is designed as the local oscillator of the receiver and the transmitter to improve the SNR and the receiver sensitivity. The design uses phase-locked loop chip HMC778 integrated with VCO from AD company. The reference frequency source is OCXO of low phase noise from KOMA company, and loop filter is active and four-order designed under the Hittite PLL Design software. The power supply part adopts low dropout voltage regulator chip from TI company. The use of power amplifier chip HMC441 can improve the output power, as well as C8051F300 MCU is used for register configuration of the PLL chip. The experimental results show that the phase noise is −92dBc/Hz@10KHz and the spurious suppression is −78dBc in the integer mode, when the phase frequency is 100MHz and the output frequency is 10.6GHz.

Dual-mode dual-band microstrip bandpass filter with high selection performance

In this letter, a new dual-mode microstrip bandpass filter (BPF) which is mainly composed of a dual-mode resonator, i.e., meandered loop resonator, with high selection performance is proposed. Compared with the traditional square loop resonator (SLR), meander loop resonator has more advantages in miniaturization. Besides, a Minkowski-like pre-fractal geometry with 1st order iteration embedded at the center of the resonator is utilized to improve the BPF capability. Both input and output ports are spatially separated 90° from each other. A small patch located in the orthogonal corner of the proposed resonator where is 135° offset from input and output ports is introduced to excite two degenerate modes. By tuning the perturbation, the two degenerate modes are excited. The influence of the variation of the perturbation size on the resonant frequencies and the coupling coefficient of the two degenerate modes is investigated. By observing the distribution of the surface current, it can be more intuitive to understand which part of the resonator has played a role when operating in different frequency bands.

Design of dual-mode dual-band microstrip bandpass filter based on Sierpinski fractal geometry

A new dual-mode dual-band bandpass filter (BPF) which is mainly formed by a cross patch resonator based on the second Sierpinski fractal curve geometry is introduced in this article. The different order Sierpinski fractal-based resonators (SFRs) are generated from the cross patch by using an iterative Sierpinski generator method. The small patch which is placed at the corner of the SFR is applied to excite the degenerate modes. By adjusting the size of the patch, two resonant modes are excited and two transmission zeros are generated which further improve the performance of the BPF. Simulated results show that the proposed filter possesses finer frequency response characteristics. Moreover, the proposed filter can be used for Wireless Local Area Networks (WLAN) and Worldwide Interoperability for Microwave Access (WiMAX) applications.

Radar anti-jamming application of solid-state noise source

Jamming reconnaissance receiver (JRR) is an important anti-jamming equipment of radar. In this paper, we propose a compensation method based on solid-state noise source to against the performance degradation of JRR caused by long-term aging, which can compensate all channels simultaneous and accomplish by JRR itself. First, presented the structure of JRR, analyzed the principle and structure of solid-state noise source. To reduce the influence of ambient temperature on compensation performance, then we given and compared two solutions: constant temperature mode and table lookup mode. At last, advanced a method using attenuator to simulate the influence of long-term aging, and carried on a contrast test. The test results show that, the aging process has no effect on the performance of JRR after the compensation based on solid-state noise source, the long-term stability of JRR has been improved greatly.

EMC Design of Multi-PLL System with High Isolation Performance

First introduced the theory of PLL, analyzed the factors in the multi-PLL system that may affect the isolation. Then employing EMC theory analyzed and designed the multi-PLL system. At the end, presented the results of isolation measurements. The methods used in the design are especially useful and helpful for the design of multi-channel receiver.

Design OFX-Band Solid State Power Amplifier

In this paper, design theory for the X-band power amplifier is introduced firstly, and CAD method is used to design the bias circuit. Precautions In the installation of GaAs FET are given. Power supply protection circuit is designed to satisfy the turn-on and turn-off sequences. At the end test results are presented