Study Of Key Technologies On Wideband Radar Reconnaissance Receiver

Along with wide applications of new systems and technologies in radardevelopment, the task of radar reconnaissance becomes more and more complex. Themodern radar has ultra-wide bandwidth, complicated signal form, and covert transceivermechanism, making signal interception, parameter estimation, radiation sourceclassification, and multi-signal processing in the radar reconnaissance receiver be atremendous challenge. Facing the modern complex reconnaissance environment, thereconnaissance receiver must have the wide instantaneous interception bandwidth tointercept various radar signals, wide instantaneous dynamic range to deal with theinterception of pulses mixed in time-frequency domain in the case of high density pulsestream and non-equal power complex modulated pulses which arrive at the same time,and ability of parameter estimation and recognition of the complex modulated signal tomeet the requirement of new systems radar reconnaissance. Aiming at these problems,in current level of hardware, this thesis researches the structure of the new type receiverwhich achieves wide instantaneous bandwidth and wide dynamic range, improves andproposes the interception method for the wide signal, and researches several keytechnologies in radar reconnaissance receiving such as intra-pulse parameter estimationof complex modulated signals and direction of arrival (DOA) estimation of the radiantsource. Finally, based on some relevant projects, this thesis verified part of algorithms inengineering environments.The main researches and contributions of this thesis are as follows:1. Aiming at the problem of ultra-wide band signal interception, this thesisresearches the structure of the Nyquist folding receiver (NYFR) prototype anddemonstrates the principle of interception of the ultra-wide band signal in this samplingstructure. From this analysis, we propose an improved NYFR structure based on thechannel coding, double local oscillators, and multiple local oscillators. These improvedstructures figure out the problem that the original receiving structure cannot assure theexistence and uniqueness of the Nyquist zone (NZ) estimation, extend the applicablesignal types of the receiver, and reduce difficulty of engineering realization. Besides, this thesis also gives the parameter estimation algorithm for the frequency agility (FA)signal and the linear frequency modulation (LFM) signal based on this improvedstructure.2. Aiming at the problem of wide band and wide dynamic range signal interception,this thesis proposes a wide band signal interception structure based on the signal phasematching principle (SPMP) from the idea of solving frequency ambiguity in the case ofundersampled signals. This structure uses parallel multiple low velocity and highprecision analog-to-digital converters (ADCs) to sample wide band and wide dynamicsignals in multiple channels. Subsequently, to get the low distortion reconstruction ofthe wide band signal, we solve frequency ambiguity in the case of multi-channelundersampled signals using the SPMP algorithm. This wide band signal interceptionstructure has the properties of seamless connection of sub-channels, non-sensitivity ofdevice differences, easy to implement in engineering, and so on.3. Aiming at the problem of reconnaissance of the complex modulated radar signal,this thesis researches parameter estimation of the convolutive signal combined LFM andPRBC (LFM-PRBC) hybrid modulated signal in the pulse asynchrony situation basedon the sub-pulse synchronization method in direct sequence spread spectrumcommunication.4. Aiming at the problem of radar signal DOA estimation on rotating carrier, thisthesis proposes a direction finding technology based on double antennas rotatingbaseline which is applicable in wide frequency range and researches a solving directionambiguity algorithm for the specific signal environment. As opposed to the similarmethods, this one has the properties of high probability of solving ambiguity, easy toimplement, and so on.5. This thesis researches the system design and hardware implementation ofpassive radar signal processor pricinple prototype, including overall scheme design ofthe pricinple prototype and development of the ADC and digital channelized board andthe parameter estimation board. The testing results show that this pricinple prototypemeets the design index and the system is stable and reliable.