【作者】 吴涛；

【导师】 唐小宏；

【作者基本信息】 电子科技大学 ， 电磁场与微波技术， 2010， 博士

【摘要】 毫米波频率源是构成毫米波雷达或通信系统的关键部件,而毫米波相参频率源能够显著提升系统的性能,而受到广泛的关注。对相参频率源技术的研究并将其应用到系统中,具有重要的现实意义。本文针对W波段相参频率源的关键技术及其应用进行了研究,主要研究工作如下：1、本文综述了目前相参频率源的合成技术,指出构建W波段相参频率源的方式主要属于混合式频率合成。根据毫米波电路部分是否主要依赖于反馈回路,可以分为两种技术方法：毫米波直接相参频率合成技术和间接相参频率合成技术。而毫米波相参频率源的技术指标依赖于微波电路的指标和电路形式的选择。2、对于毫米波近程测速雷达而言,发射机信号会泄漏到接收机中频频段,其相位噪声会严重影响到测速雷达的灵敏度。本文通过相关分析,提出通过提升发射机信号相位噪声与本振信号相位噪声的相关程度,有效的降低发射机泄露到中频后的信号的相位噪声,因此能够显著的提升系统的输出信噪比。解决了相位噪声影响雷达灵敏度问题。该思想被成功应用在w波段相参连续波频率源的设计中,所设计的频率源发射频率95 GHz,相位噪声-90dBc/Hz@10kHz,与相参本振混频后,输出泄露中频信号相位噪声-103dBc/Hz@10kHz。依赖于该频率源所设计的W波段多普勒测速雷达能够对10m/s-2000 m/s的近程目标进行速度测量,当目标截面积0.5 mm2，作用距离不大于10 m时,系统输出信噪比大于28 dB。3、对于毫米波脉间频率步进雷达而言,很多参数会对雷达的高距离分辨特性造成影响,其中就包括为雷达提供频率信号的频率步进频率源。本文分别对频率源的幅度波动、频率误差、杂波电平、相位噪声、频率切换时间以及收发相位差等参数对雷达系统的影响进行了量化分析。分析结果有助于频率源参数的指标要求设定和频率源的设计。接着对w波段相参频率步进频率源进行了设计,提出了一种在用于产生频率步进信号的DDS激励PLL电路中,可以通过修改DDS输出波形,来缩短频率切换时间的方法。不借助任何辅助电路,能够使频率切换时间达到1μs,并且输出信号的相位噪声和杂波抑制指标不受影响。所设计的w波段相参频率步进频率源输出信号相位噪声-90dBc/Hz@10kHz、杂波抑制-55 dBc、本振频率切换时间1μs,能够为系统提供高质量的信号输出,使得系统的距离分辨率达到0.6 m以上,实现高分辨的成像。4、除输出频率以外,输出功率也是频率源的一个重要参数,尤其发射机的输出功率会决定系统的作用距离。本文提出了一种功率合成网络——相参式功率合成,实现了W波段的功率合成。采用4只输出功率为75 mW左右的MPATT放大器,实现输出250 mW功率的连续波信号输出,带宽60 MHz,合成效率达到80%,能够突破单个W波段固态功率器件的极限,并且具有一定实用价值。更多还原

【Abstract】 Millimeter-wave frequency synthesizer is one of the key components of millimeter-wave radar or communication system. The performance of the system will be greatly enhanced when coherent frequency synthesizer is used. So it is necessary and important for us to study the coherent frequency synthesizer design and its applications. The key techniques and the applications of the coherent frequency synthesizer at W-band are studied in this paper. The main researches are presented as the follows:1. The main coherent frequency synthesis techniques are expounded firstly. The W-band frequency synthesis techniques mainly belong to composite frequency synthesis. According to the millimeter-wave circuit is mainly based on feed-back circuit or not, there are two main millimeter-wave frequency synthesis techniques:millimeter-wave direct coherent frequency synthesis and millimeter-wave indirect coherent frequency synthesis. The performance of the millimeter-wave coherent frequency synthesizer is mainly depended on the characteristic of the RF components or the choice of the synthesizer circuits.2. For millimeter-wave short-range radar used for speed test, the sensitivity of the radar will be deteriorated by the signal (Tx-IF) which firstly leaks from the transmitter signal then mixes to intermediate frequency with local oscillator. The coherent analysis shows that it is an effective way to reduce the phase noise of the Tx-IF by enhancing the correlationship of the phase noise of the transmitter signal and that of the local oscillator. The output signal to noise radio (SNR) will be improved in the same way. The method is successfully applied in the design of the W-band coherent continuous wave frequency synthesizer. The frequency of coherent continuous wave the synthesizer is 95 GHz and the phase noise is-90 dBc/Hz@10kHz. After mixing with the coherent LO, the phase noise of the Tx-IF is-103 dBc/Hz@10kHz. With such W-band coherent frequency synthesizer, the W-band short-range radar can be used to test the speed of the target whose velocity varies from 10 m/s to 2000 m/s. When the cross section of the target is about 0.5 mm2, and the effective range is no larger than 10 m, the output signal to noise radio of the radar system is proved better than 28 dB. 3. For millimeter-wave stepped-frequency radar, many parameters will affect the high range resolution of the radar, including the stepped-frequency synthesizer which provides the signals to the radar. In this paper, the parameters of the stepped-frequency synthesizer which will affect the radar performance are analyzed, including the amplitude fluctuation, frequency error, spurious signal level, phase noise, frequency switching time and the phase difference of the transmit-receive signal. The analysis is advantageous to the demand of the frequency synthesizer and it is helpful to the design of the frequency synthesizer. Then the W-band stepped frequency synthesizer is designed out. In the synthesizer, a method is advanced to speed up the frequency switching time, which is based on the circuit of DDS driving PLL. Without any peripheral circuits, the frequency switching time is about 1μs, and performance of the phase noise or spurious signal suppression are not influenced. The phase noise of the W-band stepped-frequency synthesizer is-90 dBc/Hz@10kHz, the spurious signal suppression is-55 dBc and the frequency switching time of the LO is 1μs. It provides high quality signals to the system. With such frequency synthesizer, the range resolution of the radar system is proved better than 0.6 m, and high range resolution imaging is achieved.4. Besides the output frequency, the output power is also important to the frequency synthesizer, because effect range of the radar system depends on the output power level. In this paper, a power combining network is introduced, the W-band coherent power combiner. With 4 IMPATT diodes whose normal rated power is 75 mW, the W-band coherent power combiner can have an output power of 250 mW. The bandwidth of the combiner is 60 MHz, and the efficiency is about 80%. The research shows that the W-band coherent power combiner can make a breakthrough at the single W-band solid diode power limit, which is valuable in the practical radar systems.更多还原