| dc.description.abstract | A novel receiver front-end; Low Noise Amplifier (LNA), mixer and Local Oscillator (LO); is designed and analyzed in Ku-band. Different design aspects of the subsystems along with the trade-offs and improvements are presented.
Two different configurations of the three-stage cascaded LNAs are designed, analyzed, fabricated and tested. The aim is to design, analyze, and improve the performance parameters of three-stage LNA, especially, to minimize the noise figure while keeping considerable gain. A cumulative approach of two-port modelling and noise extraction is presented. The work is extended to the multistage circuit level analysis from the device level analysis. For the same, sixteen-element device distributed model with all possible inherent resistor temperature noise sources is considered and analyzed. Input referred noise was analyzed and presented in terms of intrinsic and extrinsic parasitics. Noise figure was analyzed in terms of correlated and uncorrelated noises, and the conditions were indentified in our case, to make the noise figure minimum by making the correlated noise ideally zero. The achieved noise figure is as low as 1.46dB (with 30.1dB gain) in Ku-band by analyzing the three-stage LNA considering gain-constrained-noise optimization, extrinsic device parasitics, stability resistor and matching networks to the next stage. Measurement results are promising in comparison with the recent relevant work published in Ku-band LNA.
Next, a wideband 3-dB balanced coupler for the mixer application is presented. Typical rat-race coupler is modified by introducing Composite Left/Right Hand (CRLH) transmission line to provide wideband response. Proposed coupler is small in size (4.3mm X 4.3mm) and provides wideband response in 13–16GHz. Using the coupler presented; small size wideband singly balanced passive mixer in Ku-band is designed. Mixer simulated results are presented in terms of mixer performance parameters; conversion loss, noise figure and linearity. Proposed mixer has low conversion loss (–5dB) and very good Radio Frequency (RF)–LO isolation (–25dB) in Ku-band. The mixer exhibits good linear response which is analyzed by 1–dB compression (4dBm) and 3rd order intercept point (IP3) (15.7dBm). Two-stage multiband-reject Intermediate Frequency (IF) filter is designed and simulated to suppress– RF, LO frequency, 2nd order intermodulation products, and 3rd order intermodulation products.
To complete the receiver front end, next, low power Ku-band Voltage Controlled Oscillator (VCO) is designed as LO. Using VCO, frequency can be tuned in order to achieve desired IF. Two different new topologies of the negative resistance voltage-controlled oscillators at Ku-band are proposed. In VCO design-1, novel active open ended planar structure is proposed as a resonator for the VCO. Even though being a planar resonator, it provides very good quality factor (up to 235) which ensures low phase noise. VCO microwave IC is fabricated and tested. Measurements show that the VCO can be tuned for 180MHz by varying resonators’ varactors from 0V to 22V. Measured output power remains in between 4.20dBm and 8.06dBm for the entire tuning range. Measured normalized Phase Noise Figure of Merit (PNFOM) for the VCO is –214.4dBc/Hz. The DC to RF efficiency (ηDC-RF) of VCO is 19%. To the best of our knowledge, PNFOM and ηDC-RF are the best among the published planar resonator based VCOs in our frequency band of interest, to date. In VCO design-2, a novel double negative active metamaterial planar structure is proposed as a resonator. Metamaterial resonator is analyzed and composite complex constituent parameters are extracted. Metamaterial resonator has an improved quality factor compare to the resonator proposed in the design-1. The IC was fabricated and tested. Measurements show 10.37dBm power at 14.3GHz which is improved compare to the VCO design-1. | |
