Query: rat race modulator

title: Frequency chirp modulation by electro optic modulator integrated with microwave rat race circuit and measurement of chirp parameter by using optical fiber dispersion
abstract: The rat race (RR) circuit, which operates as a 180 degree hybrid, with an asymmetric power split ratio was integrated with the dual electrode type electro optic modulator on the same substrate. Thereby, frequency chirp modulation with a compact configuration was realized. The RR circuit was designed with 4.5:1 power split ratio on a z cut LiNbO3 substrate. The operation of the modulator was confirmed by observing the output light spectra. Moreover, the chirp parameter was directly measured by using the chromic dispersion of the optical fiber, where the power penalty of detected modulation signals transmitted through optical fiber was observed as a function of the fiber distance. The chirp parameter of the modulated light at 10 GHz was confirmed to be 0.47 by the measurement.

title: A Compact QPSK Modulator with Low Amplitude and Phase Imbalance for Remote Sensing Applications
abstract: A new, compact and wide band Quadrature Phase Shift Keying (QPSK) modulator is presented for remote sensing applications. The microstrip based modulator employs quadrature hybrid coupler, Wilkinson divider, rat race coupler and GaAs MESFET switches. It is designed to be part of an X band remote sensing transmitter with a center frequency of 8.25GHz. The fabricated module demonstrates the lowest reported amplitude and phase imbalances (0.1dB and 0.4deg respectively) around its center frequency. The modulation, tested up to 160 Mbps data rate, displays carrier suppression greater than 30 dB. With negligible DC power consumption and low insertion loss, it operates for a wide bandwidth of 3 GHz (7 10 GHz) The effect of amplitude and phase imbalance is investigated on the performance of the modulator. Finally, a transmitter employing this modulator exhibits an excellent overall Error Vector Magnitude (EVM) of around 8 that is considerably low as compared to the typically obtained values for such transmitters.

title: 2.4 GHz direct digital binary phase shift keying modulator using MEMS switch
abstract: A novel MEMS based binary phase shift keying direct digital modulator operating at a carrier frequency of 2.4 GHz is presented. The circuit is composed of a rat race coupler and a single pole double throw MEMS switch controlled by a digital baseband signal. The coupler divides the input waveform into two signals that are 180deg out of phase and the MEMS switch is used to select between these two signals. This circuit has been experimentally verified and results are reported.

title: A 5.8 GHz QPSK modulator
abstract: A QPSK modulator can be configured with a 90/spl deg/ coupler, two balanced (BPSK) modulators, and a power combiner. In the modulator of the present design the LO carrier operating at f/sub c=/5.8 GHz is connected to the input of a conventional 90/spl deg/ branch line hybrid producing the two signal paths in phase quadrature, to be used in BPSK modulators. The stream of polar (NRZ) pulses applied to each modulator has a data rate of 100 Mbps. Balanced modulators implemented as passive balanced mixers by use of rat race hybrids and Schottky diodes. For diodes, the HP device HSMS 202 has been used. It contains a pair of Schottky diodes properly connected for mixer applications and it is offered in a surface mount package suitable for MIC implementations.

title: Low chirp electro optic intensity modulation using planar microwave 180 degree hybrid directly prepared on LiNbO3 substrate
abstract: An electro optic (EO) modulator integrated with the microwave planar circuit directly prepared onto a LiNbO3 substrate for low chirp performance and compact configuration is introduced. A microwave rat race (RR) circuit, which operates as the 180 degree hybrid, is designed on a z cut LiNbO3 substrate to create two modulation signals of the same amplitude in antiphase with each other from a single input signal. Output ports of the RR were connected to the modulation electrodes on the substrate. The two signals drive two phase modulation parts of dual electrode Mach Zehnder modulator so that the symmetric interference are realized to obtain low chirp intensity modulated light signals. The modulator was designed and fabricated for around 10 GHz modulation frequencies and 1550 nm light wavelength. The chirp parameters were measured to be less than 0.2 in the frequency range between 8 and 12 GHz. By compensating the unbalance of the light power splitting the chirp could be significantly reduced.

title: Microwave image reject mixer modeling
abstract: A 10 GHz Image Reject Mixer (IRM) for planar technology has been designed and modeled in Ansys Ansoft Designer. The mixer can be used for both the up and down converters. Achieved parameters such as conversion gain, local oscillator (LO) and image suppression as well as required local oscillator level are highly acceptable for many applications. This IRM works with very low intermediate frequency (IF) and for this reason allows arrangement of a microwave equipment with single frequency conversion. The LO is phased by 3 dB hybrid coupler. Signals from quadrature branches are added in rat race coupler and IF signals are phased in lumped elements hybrid coupler. Similar concept can be used for zero IF frequency as single sideband modulator and demodulator.

title: Differential Mode to Common Mode Conversion Detector Based on Rat Race Hybrid Couplers: Analysis and Application to Differential Sensors and Comparators
abstract: A microwave device able to detect differential mode to common mode conversion (or vice versa) in a four port balanced circuit is proposed. For mode conversion detection, the balanced circuit should be fed by a differential mode signal, generated by means of a rat race balun from a single ended signal. By connecting the pair of output ports of the balanced circuit under test to one of the two pairs of isolated ports of a second rat race coupler, conversion to the common mode (if it exists) can be detected and recorded in the \Sigma port. Since the signal level at the output (single ended) port depends on mode conversion efficiency, the complete two port structure, including the pair of rat race couplers plus the balanced circuit in between, can be used as a comparator or differential microwave sensor based on mode conversion. In such a sensor, the working principle is symmetry disruption (caused, e.g. by an asymmetric dielectric load) and the output variable is the transmission coefficient, related to the level of asymmetry. A detailed analysis, considering an arbitrary unbalanced four port test structure (to account for symmetry disruption) is carried out. Then, such analysis is particularized to the case of a pair of unbalanced and uncoupled matched lines, and the conditions for sensitivity optimization are obtained. Finally, a differential sensor and comparator based on a pair of balanced (and meandered) matched lines, designed according to the guidelines for sensitivity optimization, is fabricated and validated.

title: Novel Evanescent Mode Cavity Filter With Reconfigurable Rat Race Coupler, Quadrature Coupler and Multi Pole Filtering Functions
abstract: A novel evanescent mode cavity filter with multiple reconfigurable functions including filtering rat race coupler, filtering quadrature coupler and multi pole filtering is proposed in this paper. It simply consists of four substrate integrated waveguide (SIW) evanescent mode cavity resonators which are arranged in a ring loop. By loading piezoelectric actuators on top of each resonator and inserting varactors between adjacent resonators, the structure can achieve multiple reconfigurable functions among filtering rat race coupler, filtering quadrature coupler and single ended multi pole filters, in addition to continuously frequency, independent bandwidth, and power division tuning. Measurement shows that the filtering quadrature coupler corves a frequency range of 2.08 3.00 GHz with insertion loss of 2.99 0.31dB, while the filtering rat race coupler corves a frequency range of 2.31 2.71 GHz with insertion loss of 2.97 0.13dB; The single ended filter can be switched among two pole, three pole, and four pole with frequency range of 2.38 to 3.01 GHz, 2.47 to 3.08 GHz and 2.53 to 3.00 GHz, respectively. Good agreement is obtained between simulated and measured results.

title: Novel Reconfigurable Filtering Rat Race Coupler, Branch Line Coupler, and Multiorder Bandpass Filter With Frequency, Bandwidth, and Power Division Ratio Control
abstract: In this article, for the first time, a novel four port coupler with reconfigurable multifunctions of filtering rat race coupler (FRC) filtering branch line coupler (FBC) and conventional single ended two port multipole bandpass filter (BPF) is proposed. It simply consists of four varactor loaded stepped impedance resonators that are arranged symmetrically. Through appropriate coupling type (electrical coupling or magnetic coupling) conversion, 90deg or 90deg phase shift between the adjacent resonators can easily be obtained and works as a key factor in the transformation between different filtering coupler modes. With this simple configuration, the proposed coupler achieves reconfigurable FRC and FBC with not only operating frequency tuning over a wide tuning range but also bandwidth and power division ratios (PDRs) control for each filtering mode. In addition, by imposing open circuit at any two ports, the four port coupler can be converted to the conventional single ended two port BPFs with reconfigurable filter orders of second, third, and fourth. The measured results show that the FRC and FBC can continuously cover the frequency ranges of 1.21 1.67 and 1.2 1.61 GHz with 1 dB bandwidth tuning of 60 120 and 55 110 MHz, respectively. The 3 and 6 dB PDRs have been demonstrated for both filtering coupler modes. In single ended two port BPF mode, the frequency tuning ranges are measured of 1.12 1.6, 1.16 1.6, and 1.2 1.61 GHz, respectively, for the proposed two port second third and fourth order BPFs. Measured and simulated results are in good agreement, validating the proposed design method.

title: Single Layer Planar Wideband Rat Race Coupler Using a Shorted Parallel Coupled Multi Line Section
abstract: In this brief, a novel single layer planar wideband rat race coupler using a shorted parallel coupled multi line section is demonstrated. The proposed coupler consists of three transmission lines and a shorted parallel coupled six line. The performances of wider bandwidths and compact size are achieved just by employing a shorted parallel coupled multi line microstrip structure, which has a high coupling factor. Explicit design equations of the proposed coupler were derived using the equivalent approach and the even/odd mode analysis. For demonstration, a 3 dB broadband rat race coupler operating at 2.2 GHz was designed. Under the criterion of <inline formula> <tex math notation="LaTeX"{S}_{11} 16.6$ /tex math>/inline formula> dB and <inline formula> <tex math notation="LaTeX"{S}_{33} 16.75$ /tex math>/inline formula> dB, the measured relative bandwidths are 68.84% and 56.67% respectively. Within the above passband, the isolation <inline formula> <tex math notation="LaTeX"{S}_{31} /tex math>/inline formula> is higher than 20.61 dB. The size is 0.034 <inline formula> <tex math notation="LaTeX"\lambda }_{\mathrm{ g}{2} /tex math>/inline formula> Good agreement is obtained between the experimental and simulated results.