In this paper, a dynamic wireless power transfer (WPT) system is realized using a metamaterial-loaded Clapp free-running oscillator (FRO) at 50 MHz. The WPT transmitter (TX) acts as the feedback network of this Clapp FRO. Also, the WPT receiver (RX) acts as the load of this Clapp FRO through mutual inductive coupling. The metamaterial unit cell is a multiring-resonator (MRR) with low magnetic loss, placed between the TX and RX. When the mutual coupling between the TX/RX pair changes due to the variation of the TX/RX distance, the Clapp FRO dynamically adapts its operating frequency to match the frequency of peak efficiency. The MRR metamaterial loading allows for several advantages including frequency and efficiency stability and lower specific absorption-rate (SAR) value when compared to the FRO-WPT system without MRR metamaterial. The theory is verified by employing simulations and measurements. The fabricated TX and RX are compact and have 20×20 and 10×10 mm2 areas. The metamaterial has two stacked layers, each with an area of 20×20 mm2. The measured dc-RF efficiency is 45% at 10 mm TX/metamaterial separation and it peaks at 51.5% in the air with an output power of 17 dBm while consuming 13 mA from a 7.5 V supply. When the receiver is embedded in a phantom medium at 10 mm depth, the metamaterial-loaded FRO-WPT system has an output power and efficiency of 15.2 dBm and 42%, respectively when consuming a 10.5 mA from a 7.5 V supply.

The use of multi-band matching for rectifiers leads to design complexity. Instead, recent advancements suggested self-matched branches combined in parallel to enable multiband operation. However, this method controls only the imaginary part. In this letter, we propose an efficient dual-band rectifier with compact realization. The rectifier consists of two self-matched parallel branches. Each branch provides comprehensive impedance control over real and imaginary parts in the corresponding band independent of the design frequency. The branch impedance matching is analyzed theoretically, and design equations are presented. To verify the proposed theory, a compact dual-band rectifier was fabricated with a compact area of only 0.42 cm2 after excluding the area required for the RF connector. The measured RF-DC power conversion efficiency (PCE) was > 50% for input power (𝑷𝒊𝒏) ranging from -5.5 dBm to 11 dBm at 390 MHz with a peak of 69%. Also, the PCE was > 50% for 𝑷𝒊𝒏 ranging from -4 dBm to 12 dBm at 690 MHz with a peak of 68%. The fabricated rectifier operates with a wide load range from 0.5 KΩ to 3 KΩ with PCE > 50% at both bands when 𝑷𝒊𝒏 = 𝟓 dBm.

This paper features the realization of CMOS millimeter-wave high-performance filters with multiple transmission zeros (TZs) employing right-/left-handed Πnetworks. First, the design methods for low pass filter (LPF) with two TZs and high pass filter (HPF) with one TZ using righthanded and left-handed networks are proposed, respectively. In both cases, the networks are analyzed, and the design equations are derived. Furthermore, for both filters, electromagnetic models are proposed and verified by on-chip prototypes on 180nm CMOS technology. The LPF prototype has a measured insertion loss of < 0.6 dB from dc to 60 GHz, a cutoff frequency of 77.7 GHz with two TZs at 100 GHz and 180 GHz. The HPF prototype has a measured insertion loss <1.05 dB from 60 to 147 GHz, a cutoff frequency of 46.9 GHz with one TZ at 33 GHz. Furthermore, a design method for band pass filters (BPFs) is proposed by cascading the LPF and HPF achieving a BPF with three TZs. After EM verification, three prototypes were fabricated on-chip exhibiting three TZs and 3-dB fractional bandwidths of 28%, 41%, and 58%. The corresponding measured insertion losses were 2.5 dB, 1.95 dB, and 1.5 dB, respectively. Also, the corresponding fabricated chip sizes were 0.045 mm2 , 0.046 mm2 , and 0.054 mm2 , respectively.