Multi-level digital modulation performed directly at carrier frequency

Abstract

Direct modulation of the carrier signal has been shown to be an attractive means of reducing the complexity of the RF hardware required in a communications transceiver. To this end, a proof-f concept X-band vector modulator, realised using monolithic phase shifters and attenuators, has been used to demonstrate that multi-level digital modulation can be implemented at high data rates and without requiring significant control power. The measured constellations for OPSK, 32-PSK and 16 CAM modulation are presented. This technique is suitable for both microwave and rrillimetre wave appicatons.

An Efficient Technique for Designing High-Performance Millimeter-Wave Vector Modulators With Low Temperature Drift

“…Combining these 0018-9480/$25.00 © 2008 IEEE two modulated portions with a Wilkinson coupler completes the modulating function. Assume that the input is an amplitude normalized signal with the frequency of , the voltage of output can be written as (1) where the constant coefficient is induced by the 3-dB coupler;…”

“…Normally, it is achieved by a complex and costly up-converter chain, which consists of baseband modulator, mixers, filters, and amplifiers. The in-phase and quadrature-phase (I-Q) vector modulator is now innovated to reduce the front-end cost and complexity for its capability of direct carrier modulation, and it gradually plays a significant role in modern wireless communication systems [1], [2].…”

An efficient technique for designing balanced vector modulators with low insertion loss

“…For each push-pull bi-phase amplitude modulator, the combined output is the vector sum of the two RTA transmission coefficients which are directly related to bias controlled reflection coefficients r of the cold-pHEMT terminations. The transmission coefficient of the amplitude modulator can be written as follows: (1) where the constant coefficient 1/J2 is induced by the the 3dB coupler; SI2}, SQ21 are the transmission coefficients of the I-Q amplitude modulators respectively and qJ is the additional phase shift. The insertion loss (IL) and phase shift (£J) of the vector modulator can be obtained as follows:…”

Accurate modelling of cold-MESFETs for adaptive MMIC signal processing applications

“…With MMIC technology, a tunable resistor is often realised using a voltage-controlled cold-MESFET [1][2][3][4][5]. Here, a standard MESFET has no DC bias applied to its drain termination.…”

“…For example, a floating cold-MESFET is found in tunable active inductofs (1,2]. Applications of shunt coldMESFETs include:-group delay synthesisers [3], balanced modulators (3,4,5]; and analogue itattenuators [6].…”