The objective of this study is to develop a wireless ultrasonic structural health monitoring(SHM) system for aircraft wing inspection. In part I of the study (Zhao et al 2007Smart Mater. Struct. 16 1208–17), small, low cost and light weight piezoelectric (PZT) disctransducers were bonded to various parts of an aircraft wing for detection, localization andgrowth monitoring of defects. In this part, two approaches for wirelessly interrogating thesensor/actuator network were developed and tested. The first one utilizes a pair of reactivecoupling monopoles to deliver 350 kHz RF tone-burst interrogation pulses directly tothe PZT transducers for generating ultrasonic guided waves and to receive theresponse signals from the PZTs. It couples enough energy to and from the PZTtransducers for the wing panel inspection, but the signal is quite noisy and themonopoles need to be in close proximity to each other for efficient coupling. Inthe second approach, a small local diagnostic device was developed that can beembedded into the wing and transmit the digital signals FM-modulated on a915 MHz carrier. The device has an ultrasonic pulser that can generate 350 kHz,70 V tone-burst signals, a multiplexed A/D board with a programmable gainamplifier for multi-channel data acquisition, a microprocessor for circuit controland data processing, and a wireless module for data transmission. Power to theelectronics is delivered wirelessly at X-band with an antenna–rectifier (rectenna)array conformed to the aircraft body, eliminating the need for batteries and theirreplacement. It can effectively deliver at least 100 mW of DC power continuously froma transmitter at a range of 1 m. The wireless system was tested with the PZTsensor array on the wing panel and compared well with the wire connection case.