The Ku-band Frequency Synthesizer Using Incoherent Frequency

Recently, the development and practical application of the optimal control theory, flight control, and digital map, etc, have more attraction for integrated the terrain following and terrain avoidance (TF/TA) techniques, but in consideration of the complexity of them, the current TF/TA techniques are still valuable and have much great progress in military. In the paper, for frequency synthesizers of TF radar-one of the concept research subjects in the 9th five-year plan, we present the circuits of crystal oscillator (CO), spread spectrum modulation, balanced mixer, microwave control, and so on. The Ku-band frequency synthesizer using incoherent frequency hopping is studied with emphasis. The frequency synthesizer is divided into the HF circuits and the microwave circuits according to the bands. The HF circuits consists of one IF CO and one IF-HF local oscillator (LO). The frequency of IF LO can抰 be selected too low for difficulty of designing the band-pass filter (BPF). Taking the stability of the system and the suppression of the BPF into account, the suitable IF-HF LO frequency is selected by analyzing frequencies relation of the system. Microwave circuit consists of a voltage- controlled LO, an up-converter, a BPF and a microwave amplifier. Outputs of the HF circuit are mixed with signals of the voltage-controlled LO at the up-converter, and the signals of upper side band and lower side band are generated. Desired side-band signals are then extracted via the BPF. The signals are amplified at microwave amplifier and are applied to the transmitter as a drive. Simultaneously, the voltage-controlled LO also provides a drive signal for the microwave mixer of receiver. From the point of getting microwave signals and achieving frequency hopping, this paper discussed the designs of key parts, such as microwave voltage controlled oscillator, microwave up-converter and microwave band-pass filter. The designed incoherent frequency hopping system in Ku-band is suited to the TF radar which doesn抰 require the feature of moving target indication. The system has strong anti-interference, high efficiency, low power, small size, light weight and low cost. It is a feasible scheme that is used to the terrain-following radar of incoherent ? frequency hopping in low sky navigation pod.