Aselsan Elektronik Sanayi Ve Ticaret Anonim Sirketi

Bulent Sen

Filiz Ece Filci

Filiz Ece Sagcan

Aylin Bayram

An analog input signal (X) is processed by a Peak to Average Ratio Reduction (PARR) block to diminish the difference between peak amplitudes and average amplitudes of the analog input signal (X). After, a distorted signal (h(n)) having low peak to average amplitude ratio, generated at the PARR block output, is processed by a delta sigma modulation (DSM) block converts the distorted signal (h(n)) into a digitally modulated distorted signal (h_dsm) with high signal to noise ratio (SNR). Afterwards, the digitally modulated distorted signal (h_dsm) is corrected and amplified by a Class-D RF power amplifier fed by a feeding signal (env) generated from a digital correction signal (z_dsm). As a result, a digitally modulated signal (y(n)) with high signal to noise ratio (SNR) of the analog input signal (X) is generated at the output of the Class-D RF power amplifier.

Class-S RF transmitter for MRI scanners

An all digital outphasing transmitter includes, at least one decomposition unit for decomposing an input signal to generate a first sub-signal and a second sub-signal; at least one outphasing signal generator to convert said first sub-signal to an outphasing signal; at least one delta sigma modulator to convert said second sub-signal to a delta sigma modulated signal; at least one mixing unit for mixing the outphasing signal and delta sigma modulated signal to generate a first and second mixed signal; at least one first amplifier for amplifying the first mixed signal; at least one second amplifier for amplifying the second mixed signal; at least one combiner for combining the first and second amplified mixed signals to generate a delta sigma modulated output signal and at least one band pass filter for filtering the delta sigma modulated output signal to recover the input signal envelope back on to the output signal.

All digital outphasing transmitter

In the present invention, an all digital, multi channel RF transmitter is utilized for a parallel magnetic resonance imaging (MRI) device, MRI signal generation, modulation and amplification are employed entirely digitally in the proposed RF transmitter, which enables each transmit channel to be easily and individually reconfigured in both amplitude and phase. Individual channel control ensures a homogeneous magnetic field in the multi channel RF coil in MRI. Besides the homogeneous magnetic field generation, multi-frequency MRI signal generation is made easy by the present invention with very high frequency resolution. Multi-frequency enables faster image acquisition which reduces MRI operation time. Digital Weaver Single Side Band (SSB) modulation is also incorporated into the all digital transmitter to suppress unwanted bands of Double Side Band (DSB) MRI signals. The power amplifier in the MRI transmitter does not amplify the unwanted band so that SSB modulation leads to higher power efficiency.

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Ankara, Turkey

Bulent Sen