Abstract
Composite right/left-handed (CRLH) waveguide leaky-wave antenna (LWA) with low sidelobe level (SLL) and high radiation efficiency is investigated and designed in this paper. Due to the characteristic of negative and positive dominant mode propagation constant of the CRLH transmission line, a backward to forward beam-steering LWA can be realized through frequency scanning. The leaky-wave radiation is analyzed first based on a Ka-band CRLH waveguide with straight slots differently offset on the broadwall. The propagation constant maintains almost invariable as the slot offset varies, meanwhile the attenuation constant has a considerable dynamic range. Thus meandering long slot, whose offset varies along the CRLH waveguide, can be cut on the broadwall to generate a tapered excitation distribution. A prototype of the proposed CRLH waveguide LWA with meandering long slot is designed and fabricated to validate the design. Measurement results show that continuous beam-steering capability from −29° to +31° is achieved, meanwhile the optimized SLLs for the designed antenna patterns are kept below −18.5 dB in the major operating band with the minimum SLL of −22.4 dB at 33 GHz, and the average radiation efficiency is 65.4%. The realized SLLs and radiation efficiency performances of our CRLH LWA surpass others reported in open literatures.
Highlights
Beam-steering capability is highly demanded in many radars systems, especially in tracking radars
We have proposed a Composite right/left-handed (CRLH) ridge substrate integrated waveguide (RSIW) slot array antenna in [10]
A CRLH waveguide composed of 100 unit cells is used to design the leaky-wave antenna (LWA), and the desired pattern for this antenna is specified as a Taylor radiation pattern with −30 dB sidelobe level (SLL)
Summary
Beam-steering capability is highly demanded in many radars systems, especially in tracking radars. The comparison of the full-wave simulation for the surface current of this CRLH waveguide with the analytical derivation is performed in the previous work in [25] This characteristic is the principle for designing high performance CRLH LWAs because the slot offsets can be varied to realize a tapered excitation distribution to achieve low SLL of radiation patterns. The effect of various parameters to the CRLH characteristic is first studied to give a guidance to the balanced CRLH LWA unit cell design As stated above, this CRLH waveguide is operating in the dominant mode, the cutoff frequency of the main. Balance condition for the CRLH unit cell can be achieved by optimizing the different parameters responsible for the LH and RH propagation, respectively This design can be treated as a general technique to obtain similar CRLH structures for different operating frequencies. A CRLH waveguide composed of 100 unit cells is used to design the LWA, and the desired pattern for this antenna is specified as a Taylor radiation pattern with −30 dB SLL
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