Design and Measurement of a Doppler Radar With New Quadrature Hybrid Mixer for Vehicle Applications

International Journal of Antennas and Propagation

2023

This paper presents an efficient decoupling network using a single directional coupler and transmission lines for closely spaced Tx/Rx antennas in single polarized radar applications. The isolation between both antennas can be enhanced by controlling the phase of the Tx leakage signal and the coupling coefficient of the directional coupler. Its structure provides no loss of Tx/Rx paths excepting minute loss due to the coupling of the directional coupler. The Tx leakage is more insensitive to the antenna impedance variation compared with a conventional monostatic system. The design process is as follows: First, closely separated Tx/Rx antennas were designed and their isolation ( I a ) was extracted. Second, the directional coupler was designed with its coupling coefficient = I a . Finally, both were connected by transmission lines, of which phases were adjusted for the coupled and antenna-isolated signals with 180° phase difference. The Tx/Rx antennas without and with the decoupling network have 15-dB bandwidths of 23.98–24.43/23.98–24.50 GHz and 23.80–24.36/23.80–24.45 GHz, respectively. Gains of 8.17/8.39 and 8.72/8.73 dBi and efficiencies of 60.56%/60.77% and 63.0%/61.8% in the Tx/Rx antennas without and with the decoupling network were achieved at 24.1 GHz, respectively. The dimension of the proposed antenna is 1.62λ0 × 2.09λ0 × 0.0204λ0. The K-band antennas show a good Tx-Rx isolation of 29.3–67.9 dB which was superior at least 9 dB to the conventional antennas.

Section: Introductionmentioning

confidence: 99%

Decoupling Network for Closely Spaced Tx/Rx Antennas Using a Directional Coupler and Transmission Lines

Park

Roh

International Journal of Antennas and Propagation

2023

Direct conversion Doppler radar vital sign detection system using power management technique

Micro & Optical Tech Letters

Lin

Chen

et al. 2014

Furthermore, the tunable operation frequency range of the proposed impulse generator is experimentally studied. This impulse generator can work well at any input frequency around 1-15 MHz. Figure 4 displays the experimental results of the final output impulses at operation frequencies of 1, 5, 10, and 15 MHz. It can be recognized that the lower frequency, the slightly higher amplitude. This is attributed to the recovery time of the RC-circuit of the collector resistance and the output coupling capacitor. When frequency is higher the period is shorter so that the output coupling capacitor has shorter time for recovery. Consequently, the output amplitude is lower. Therefore, by adjusting the values of the collector resistance and the output coupling capacitor, we can broaden the working frequency range. In addition, the fabricated impulse generator was checked by HP 8593E RF spectrum analyzer with generated high-order harmonic up to 10 GHz.With such output UWB short impulses, the impulse generator can be used for many practical applications in electronics and optics. By utilizing the fast leading edge characteristic of the generated short impulses for driving actively mode-locked fiber lasers, we may anticipate a possible generation of shorter optical pulses than reported in [6]. This issue is currently under investigation and will be reported elsewhere. CONCLUSIONIn this article, we have described a method for generating UWB picosecond impulses with fast fall-time based on the fast switchon characteristic of a broadband bipolar transistor and the edge compression characteristic of a NLTL comb generator. The experimental results showed that the generated short impulses had a pulse-width of about 725 ps, a fall-time of 180 ps, and a peak power of 1 W at 50 X. ABSTRACT: This article is the first to present a low power consumption direct conversion Doppler radar vital sign detection system using a power management technique to detect biomedical signals. The optimal pulse bias with simultaneous switching noise considered was designed to decrease power consumption of the sensor. A noncontact vital sign detection measurement using the optimal pulse bias was performed on a human subject. Based on experimental results, the presented simple and low power system can accurately detect human cardiopulmonary activity, including respiration and heartbeat. Calculated physiological signal amplitudes based on a spectral analysis validates the detection result from presented work. When compared with the sensor using a power amplifier, the proposed sensor can achieve low power dissipation for biomedical monitoring and green energy applications.

Low‐power 0.13‐μm CMOS receiver for microwave Doppler sensor

Kim

Micro & Optical Tech Letters

Kim

2019

In this article, we present the design and fabrication of a monolithic microwave‐integrated circuit (MMIC) using 0.13‐μm complementary metal‐oxide‐semiconductor (CMOS) radiofrequency (RF) process for a low‐noise amplifier (LNA) and a passive down mixer for a microwave Doppler sensor receiver operating in the 24‐GHz band (K band). The low‐noise amplifier uses a single‐stage cascode structure to ensure a small size and gain suitable for a microwave Doppler sensor. The down mixer has a passive frequency mixer structure and a single balanced design using balun for the local oscillator (LO) input. The output of the LNA and the input of the down frequency mixer are conjugately matched to minimize the flicker noise generated by the receiver for the microwave Doppler sensor. The designed MMIC showed a voltage conversion gain of 14.46 dB and an input P1dB of −21.16 dBm when the LO power was 0 dBm within the IF range (0.01‐1 GHz). A noise figure of less than 19.24 dB was obtained. The MMIC area and the power consumption were 0.647 × 0.363 mm2 and 6 mW, respectively.