The development of a novel switched-mode 2.45？GHz microwave (MW) multiapplicator system intended for laparoscopic and open surgical thermoablative treatments is presented. The system differs from the other synchronous and asynchronous commercially available equipments because it employs a fast sequential switching (FSS) technique for feeding an array of up to four high efficiency MW applicators. FSS technology, if properly engineered, allows improving system compactness, modularity, overall efficiency, and operational flexibility. Full-wave electromagnetic (EM) and thermal (TH) simulations have been made to confirm the expected performances of the FSS technology. Here we provide an overview of technical details and early ex-vivo experiments carried out with a full functional β-prototype of the system. 1. Introduction In cancer treatment, open surgery and chemotherapy are still the physicians’ first choices. The gold standard treatment for most of the tumors in the liver, lung, and kidney is surgical resection. However, up to 80% of liver cancer patients and 50% of lung cancer patients are refractory to surgery due to multifocal disease, poor baseline health, or comorbidities such as cirrhosis and emphysema [1, 2]: for some patients, removal of tumors with open surgery is not possible or involves a too high risk due to the poor condition of the patient himself. Therefore their success rate largely depends on the type of malignancy treated and on the progress of the disease. Minimally invasive surgery or percutaneous interventions may in these cases be adequate to increase safety, reduce trauma, and shorten operative time [3–5]. Microwave ablation (MWA) is a relatively new technology in continuous development because it offers some advantages when compared to the radiofrequency ablation (RFA) [6–8], the technology which currently represents the prevailing clinical focal therapy. MWA can generate higher temperatures in less time since tissue charring does not hinder the radiation of MW fields and it is less susceptible to the heat-sink effect of peritumoral vessels [9]. For these reasons, MWA and their minimally invasive approach have fertile ground for innovation through future systems and technological developments. Clinical MWA equipment operate at 915？MHz or 2.45？GHz since these bands, which are allowed for medical use and relatively high-power devices, are readily available providing a balance between localized heating and sufficient energy penetration to treat most focal tumors [10]. The power that the coaxial structure of a microwave applicator can
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