# US 2018/0323656 A1 · Waveform design for rf power transfer > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 2018/0323656 A1 - Document ID: US20180323656A1 - Status: Published application - Kind: A1 - Application number: 15/959,917 - Filed: 2018-04-23 - Published: 2018-11-08 - Earliest claimed: 2017-05-02 - Assignees: Board of Regents, The University of Texas System - Applicants: Board of Regents, The University of Texas System - Inventors: Zygmunt Haas; Zhong Zheng - Web page: https://patentgrep.com/patent/US20180323656A1 ## CPC - H02J 50/20: using microwaves or radio frequency waves - G06K 19/0709: {the source being an interrogation field} - H01Q 1/2225: {used in active tags, i.e. provided with its own power source or in passive tags, i.e. deriving power from RF signal} - H04B 5/45: Transponders - H04B 5/77: for interrogation - H04B 5/79: for data transfer in combination with power transfer - H01Q 1/248: {provided with an AC/DC converting device, e.g. rectennas} - H02J 50/40: using two or more transmitting or receiving devices (H02J50/50 takes precedence) - H04B 5/20: characterised by the transmission technique; characterised by the transmission medium - H02J: ELECTRIC POWER NETWORKS; CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY - G06K: GRAPHICAL DATA READING (image or video recognition or understanding G06V); PRESENTATION OF DATA; RECORD CARRIERS; HANDLING RECORD CARRIERS - H01Q: ANTENNAS, i.e. RADIO AERIALS (radiators or antennas for microwave heating H05B6/72) - H04B: TRANSMISSION ## Abstract A passive tag transponder circuit comprising a receive antenna, reflect antenna, and rectifier network. The receive antenna can be configured to receive an ambient RF signal having a frequency of fc, or, a backscattered RF signal having a frequency of 2fc. The reflect antenna can be configured to receive a rectified output signal from the rectifier network, the rectified output signal having a frequency of 2fc. The reflect antenna can be configured to send a backscattered signal at the frequency of 2fc. The rectifier network can be connected to receive an input corresponding to the ambient RF from the receive antenna and send the rectified output to the reflect antenna. ## Claims ### Claim 1 A passive tag transponder circuit, comprising: a receive antenna configured to receive an ambient RF signal having a frequency of fc, or, to receive a backscattered RF signal having a frequency of 2fc; a rectifier network; and a reflect antenna configured to receive a rectified output signal from a rectifier network, the rectified output signal having a frequency of 2fc and configured to send a backscattered signal at the frequency of 2fc, wherein: the rectifier network is connected to receive an input corresponding to the ambient RF from the receive antenna and send the rectified output to the reflect antenna, and the ambient RF signal has a modified continuous waveform such that the rectified output has substantially no harmonic frequencies greater than 2fc. ### Claim 2 (depends on 1) The transponder circuit of claim 1, further including a first LC circuit connected to the receive antenna, wherein the first LC circuit is switchably configured to tune the receive antenna to the frequency of fc, or, to the frequency of 2fc. ### Claim 3 (depends on 2) The transponder circuit of claim 2, further including a first impedance matching stub connected to the first LC circuit and switchably configured to feed the input to the rectifier network, or, to a logic circuit of the transponder circuit. ### Claim 4 (depends on 1) The transponder circuit of claim 1, further including a second impedance matching stub connected to the rectifier network and to a second LC circuit, the second LC circuit connected to the reflect antenna, wherein the second LC circuit configured to tune the reflect antenna to the frequency of 2fc. ### Claim 5 (depends on 4) The transponder circuit of claim 4, further including a switch connected to the second LC circuit, the switch configured to switch loads attached to the reflected antenna to have different impedances for representing information bits. ### Claim 6 (depends on 1) The transponder circuit of claim 1, further including a logic module, the logic module connected to: switch the receive antenna to be tuned the frequency of fc, or, the frequency of 2fc; switch the input corresponding to the ambient RF to the rectifier network, or, switch an input from the receive antenna corresponding to the backscattered RF signal to the logic module; and switch between open and short circuits of the reflect antenna to modulate information bits into the backscattered RF signal sent by the reflect antenna. ### Claim 7 (depends on 6) The transponder circuit of claim 6, wherein the logic module further includes a demodulation circuit configured to demodulate the backscattered RF signal fed to the logic circuit. ### Claim 8 (depends on 1) The transponder circuit of claim 1, wherein the receive antenna and the reflect antenna are combined in a single antenna. ### Claim 9 (depends on 1) The transponder circuit of claim 1, wherein the rectifier network has four Schottky diodes. ### Claim 10 (depends on 1) The transponder circuit of claim 1, wherein the transponder circuit is part of a tag-to-tag communication system having an interrogator configured to transmit the ambient RF signal at the frequency fc. ### Claim 11 (depends on 1) The transponder circuit of claim 1, wherein the ambient RF signal has a sinusoid continuous waveform.