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Home Sensors Pulse Microwave (MW) Bridge for a Q-Band Electron Spin-Echo (ESE) Spectrometers Equipped with Frequency Counter

Pulse Microwave (MW) Bridge for a Q-Band Electron Spin-Echo (ESE) Spectrometers Equipped with Frequency Counter

Description

Spin-echo experiment is in exciting of the spin system with a high power pulse of MW energy and then measuring the emission signal that is referred to as spin echo signal - the response of the spin system on pulse excitation. Q-band Pulse MW Bridge representing a transmitter-receiver module (TRM) designed for ESE spectrometer operation. The main part of the transmitter module is the two-stage pulse amplifier which provides signal amplification in output up to 23-24 W with input power of 30-40 mW (gain factor 25-27 dB) and operates on the principle of external synchronization. The operating mode of the two-stage coherent MW generator is a serial burst of pulses. The output power of the pulse amplifier can be attenuated by a high power attenuator (0-40 dB) inserted after it.

Gunn diode is used as a master oscillator. Its output power of 100 mW is split into two parts. One part of the signal is served as a driving signal for transmitter module and the second part delivers to the reference arm to balance mixer of receiver module providing the coherent detection of the ESE signal. The direct amplification scheme is selected for receiver module including balance mixer based on Shottky diode and phase-lock detector, attenuators, phase shifter, low noise amplifier (LNA) protected from pulse signals by limiter and switch. The switch is controlled by TTL pulse. LNA noise figure is no more 3dB. For the evaluation of pulse characteristics two monitor signals could be picked up through amplitude detector: one just before the pulse amplifier to observe its output pulses and a second one before the protect PIN diode to monitor the pulses reflected from the probehead. The MW bridge is optimized for standard Davies and Mims pulse ENDOR experiment and equipped with Frequency Counter to measure the operating frequency of Gunn diode.

Specifications:

  • Power in pulse ––––––––––––––––––––––––––––––––– up to 15 W;
  • Burst of pulse: ––––––––––––––––––––––––––––––––– 1- 3;
  • Duration pulse: –––––––––––––––––––––––––––––––– 10-300 ns;
  • Phase deviation within and between pulses: ––––––––– ≤ 5° for 100 ns and ≤ 15° for 300 ns;
  • Frequency repetition of pulse burst: ––––––––––––––– 100 Hz-1 kHz.

Innovative Aspect and Main Advantages

The advantage of the MW bridge, designed for the coherent ESE spectrometer, over available one in the world is a low cost, simple operation mode, optimal output power, minimal pulse duration. The low cost of the MW bridge, is ensured by utilization of the pulse IMPATT diodes designed for amplification of the mw pulses instead of high cost TWT amplifiers. Simple operation mode of MWbridge is ensured by selection of direct amplification scheme for receiver module. 15 W output power and minimal pulse duration ranging between 10 - 100 ns is achieved by design of twostage pulse coherent generator. For comparison, the MW output power of MW bridge in commercially available Bruker ELEXSYS E 580 Q-band spectrometer has value of one order lower than that in suggested MWbridge (1W).

Areas of Application

  • Relaxation Time measurements;
  • Field-Swept Echo Spectroscopy;
  • Spin-Echo Envelope Modulation;
  • Spin-Echo ENDOR spectroscopy (optimized for Davies and Mims pulse sequences).



Q-band Pulse Microwave Bridge Configuration.
1.hase shifter, 2 - PIN modulators; 3 - two - stage pulse amplifier; 4, 8 - amplitude detectors;
5 - attenuator Att1; 6 - circulator; 7 - probehead; 9 - protective switch; 10 - balance mixer.

Stage of Development

Pilot samples.

Contact Details

V. Lashkaryov Institute of Semiconductors Physics of the National Academy of Sciences of Ukraine
Contact persons: E.N. Kalabukhova
Address: 41, Prospect Nauki, 03028, Kiev, Ukraine
Tel./Fax: (+38 044) 489 1704
E-mail: This e-mail address is being protected from spambots. You need JavaScript enabled to view it

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