Six-Port Direct Carrier Modulator at 7.5 GHz for Ultra-Wideband Appliations
(English)Manuscript (preprint) (Other academic)
A 7.5 GHz direct-carrier modulator for multi-level quadrature amplitude modulation (M-QAM) using a wideband 7-8 GHz six-port correlator and four controllable impedance terminations implemented with field-effect transistors (FET) is presented in this paper. The proposed encoding schemes of the reflection-type modulator is based on equal impedance values at I and Q ports, such that Γ3 = Γ4 and Γ5 = Γ6 for every symbol in the constellation diagram. The field-effect transistors are operated at zero drain-source voltage (cold-FET). The FET-impedance termination topology includes a source resistor (RS) and a gate resistor (RG) for symmetrical spreading of the reflection coefficients around the origin. In order to validate the 7.5 GHz six-port modulator with cold-FET impedance terminations, the six-port modulator prototype has been realized on a ROGERS4350B substrate of 0.254-mm thickness and tested with a six-port demodulator (receiver). The six-port modulator was measure to have symbol rates of 10 Msymbol/s with QPSK (= 20 Mbit/s) and 250 Msymbol/s with 16-QAM (= 1 Gbit/s).
Terms—modulator, six-port, ultra-wideband
IdentifiersURN: urn:nbn:se:liu:diva-53608ISBN: 978-1-4244-2930-1OAI: oai:DiVA.org:liu-53608DiVA: diva2:290162