Abstract: An electron paramagnetic resonance (EPR) spectrometer includes a sample resonator with a sample area for a measurement sample to be held in the sample resonator, a tunable microwave source for generating a tunable microwave signal to be applied to the sample resonator, a magnet system for generating a variable magnetic field to be applied at least to the sample area in the sample resonator, and a microwave detector connected to the sample resonator for detecting microwave radiation. The tunable microwave source comprises a fixed frequency microwave oscillator for generating a fixed frequency microwave signal, a tunable frequency generator for generating a tunable high frequency (HF) signal of lower frequency than the fixed frequency microwave signal, and a mixer for mixing the fixed frequency microwave signal and the tunable HF signal, thus generating a tunable microwave signal. A simple EPR spectrometer with high spectral resolution is thereby provided.

Abstract: A microwave power amplifier arrangement for an electron paramagnetic resonance (EPR) system provides amplified microwave pulses having a microwave frequency in the X-band. The arrangement has a microwave input and a microwave output, and comprises at least one transistor amplifier device, and at least one switchable reflection device. A respective transistor amplifier device comprises a transistor amplifier device input directly or indirectly connected to the microwave input (2), at least one transistor, and a transistor amplifier device output directly or indirectly connected to the microwave output. A respective switchable reflection device comprises a PIN diode and a lambda/4 line connected directly or indirectly to the transistor amplifier device output of at least one transistor amplifier device and to a first port of the PIN diode, with lambda being the wavelength of the microwave radiation within the lambda/4 line. A second port of the PIN diode is connected to ground.

Abstract: A microwave power amplifier arrangement for an electron paramagnetic resonance (EPR) system provides amplified microwave pulses having a microwave frequency in the X-band. The arrangement has a microwave input and a microwave output, and comprises at least one transistor amplifier device, and at least one switchable reflection device. A respective transistor amplifier device comprises a transistor amplifier device input directly or indirectly connected to the microwave input (2), at least one transistor, and a transistor amplifier device output directly or indirectly connected to the microwave output. A respective switchable reflection device comprises a PIN diode and a lambda/4 line connected directly or indirectly to the transistor amplifier device output of at least one transistor amplifier device and to a first port of the PIN diode, with lambda being the wavelength of the microwave radiation within the lambda/4 line. A second port of the PIN diode is connected to ground.