In this architecture, when the switches are off the input signal is transferred to the output and the ASK modulator is in the ON state. On the other hand, when the switches are turned on, no input signal is transferred to the output and the ASK modulator is in OFF state.
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The distributed structure requires a large number of switches since the resistances of the switches in the OFF state should be small to realize a lossy transmission line. However, low-quality parasitic capacitances in the switches, which are located on a silicon substrate, are expected to degrade the transmission line characteristics. Note that the isolation characteristics become degraded upon reducing the number of switches since each switch has a leakage to the output.
To achieve high isolation with a reduced number of switches, the transmission line length between switches is adjusted. When the millimeter-wave signal travels from the source to the load, the switches do not only dissipate the incident signal, but they also reflect and leak it as shown in Figure Illustration of transmitted, reflected, dissipated and leaked signals of a switch in the a ON and b OFF states of the modulator when the millimeter-wave signal travels from source to the load.
In Figure 13 b , the calculated leaked, reflected and dissipated powers are shown as a function of the distance between switches. Since the dissipated power in the switches is insensitive to the transmission line length, reflection should be maximized to minimize the leakage. To obtain maximum reflected power and minimum leaked power, the switches are separated by a quarter-wavelength distance.
In this case, the isolation is maximized with a lower number of switches. Since the parasitic capacitance of each switch in the OFF state is negligible, the input impedance of each transmission line is equal to the load impedance and the input power is transferred to the output. When the digital input is 1V, the switches are turned on.
The transmission line with a quarter wavelength transforms the low impedance of the switch to a high impedance and reflection is maximized. In this case, the leaked power to the output is minimized and high isolation is achieved. The slow-wave transmission line SWTL Cheung, shown in Figure 15 is used for implementing the quarter-wavelength transmission lines and the networks between the circuit and the pads to reduce the size of the modulator.
In the SWTL, a slotted ground shield under the signal line is laid orthogonal to the direction of the signal current flow. This structure results in the propagating waves having lower phase velocity; thus, the corresponding wavelength at a given frequency is reduced.
Low Power RF Circuit Design in Standard CMOS Technology
Transient internal waveforms are simulated as shown in Figure A ps pulse is applied from the data port to analyze the response of the circuit. The total time of the rising and falling gate. Transient simulation; a ps applied data pulse, and responses of b the gate voltage of the NMOSFET switch, and c input and d output signals. Figure 17 shows a micrograph of the fabricated ASK modulator. The size of the chip is 0. The core size is 0. The measured and simulated insertion losses of the modulator for the two states are shown in Figure 18 a for comparison.
The isolation is nearly flat from 20 to 80GHz, although the maximum isolation is measured at 60GHz. As a result, shorter transmission lines may be adopted to reduce the insertion loss caused by the SWTL in the ON state of the modulator. The simulated isolation is shown at frequencies up to GHz in Figure 18 b to demonstrate. The time-domain response is measured using a 70GHz sampling oscilloscope, a 60GHz millimeter-wave source module and a pattern generator.
No external filters are applied in the measurement. A 60GHz continuous wave is applied to the RF input and the modulator is controlled by the pattern generator. The rising and falling times of the applied baseband signal are 6ps and 8ps, respectively. The output response for the maximum data rate is shown in Figure 19 a.
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In Figure 19 b , the output response is shown for a ps single-baseband pulse by reducing the scale to 20ps. Measured output response of the modulator for a an 8Gbps data train and b a single ps data pulse. The maximum data rates as a function of the isolation of the millimeter-wave ASK modulators are shown in Figure It can be seen that the isolation and the maximum data rate have a tradeoff relationship. The product of the maximum data rate and the isolation of this modulator is GHz, which is the highest value among multi-Gbps ASK modulators.
Its isolation was maximized by a quarter-wave length transmission line which results in a long transmission lines, therefore the insertion loss becomes high. Off-chip millimeter-wave source module will increase the size, the total power consumption and the cost of the TX system. The oscillator should be embedded in the CMOS chip for a practical application.
The millimeter-wave CMOS oscillators are commonly designed in differential. To utilize the differential-ended output signal, a double-pole-single-throw DPST switch was proposed for modulator as shown in Figure 22 b. Figure 23 shows the schematic of the on-chip 60GHz CW source circuit which consist of two sub-blocks, a 60GHz oscillator and a buffer. The 60GHz oscillator contains an on-chip transmission. Architecture of a a single-ended millimeter-wave pulse transmitter with off-chip 60GHz CW source and b a proposed differential-ended pulse transmitter with on-chip 60GHz CW source.
The size of the devices was chosen by considering the parasitic and the process variations to keep the resonation at the 60GHz millimeter-wave band. The active device and the MOS capacitor models were obtained from the foundry. The transmission lines were characterized by a 3D full-wave electromagnetic field simulation using high-frequency structure simulator HFSS. The bias voltage does not only affect the negative conductance but also power consumption.
High supply voltage results in a high-power dissipation. Even though a maximum 1. The inputs are connected to the complementary outputs of the on-chip 60GHz signal source. The gates of the switches are controlled by binary data. Since the parasitic capacitance of each switch in the OFF state is negligible, the input impedance of each transmission line is equal to the load impedance and the input power is transferred to the output as shown in Section 2.
The transmission line transforms the low impedance of the switch to high impedance and reflection is increased. In this case, the leaked power to the output is reduced and isolation is improved as shown in Section 2. Circuit schematic of the differential-ended ASK modulator for 60GHz millimeter-wave pulse transmitter. The isolation is theoretically maximized when the switches are separated by a quarter-wavelength transmission line however long transmission lines result higher insertion loss. As a result, shorter transmission lines may be adopted to reduce the insertion loss caused by the on-chip transmission line in the ON state of the modulator.
Figure 25 shows the micrographs of the pulse transmitter chip. A 60GHz continues-wave signal was measured at the output of the circuit whose spectrum is shown in Figure In this measurement setup, the total power loss of the probe, cables, connecters and harmonic mixer is approximately 42dB. It was observed that the fabricated chip starts to oscillate when the bias voltage is larger than 0.
The measured operating frequency as a function of supply voltage is plotted in Figure 27 a. Figure 27 b shows the power dissipation and millimeter-wave RF power as a function of the supply voltage from 0. As the supply voltage increases, the power dissipation rapidly increases. However, the millimeter-wave output power saturates when the supply voltage reaches near to 1V. The power. Measured a operating frequency of the oscillator and b power dissipation and output millimeter-wave power of the oscillator as a function of supply voltage.
We reduced to the supply voltage to 1V for low-power operation where the millimeter-wave output power was measured to be In this study, we found out that our layout versus schematic verification software had not been functioning properly while we had been designing the circuit using this 90nm CMOS technology first time. The core of the oscillator operates properly; however, because of the verification error in the layout, we noticed that the buffer attenuates the generated millimeter-wave signal by 18dB although it was designed to have 10dB gain.
The measured insertion losses of the modulator for the two states are shown in Figure 28 a. When the gate voltage is 0 volt, the insertion loss was measured to be a 2. When the gate voltage was increased to VDD, the insertion loss became Figure 28 b shows the measured reflection of loss of the modulator for the two states.
When the modulator was turned on by increasing the gate voltage, the S11 became The product of the maximum data-rate and the isolation of this modulator is slightly less than the previous work in Section 2. The chip was measured by on-waver. The output is connected to the sampling oscilloscope by on-wafer probe and cables.
The measurements were performed without any external filters at the output. Due to the high-speed binary base-band signal leakage from the gate, the baseline varied. Especially the leakage became stronger at 10GHz but it will not distort the transmitted millimeter-wave signal since the base-band leakage will be filtered out in the 60GHz band antenna.
The RF power can be measured from the time-domain response shown in Figure It corresponds to dBm peak power. By using this circuit up 10Gbps short-range wireless or proximity communication can be realized a power dissipation of Our study showed us that with a proper buffer design and improved layout verifications, the output RF power would be increased up to a few dBm with an additional cost of a few tens of mW power dissipation for longer range applications.
Conventional QAM receivers downconvert the received millimeter-wave signal to baseband using one or two voltage-controlled oscillator VCO and phase-locked loop PLL circuits. However, these building blocks consume several tens of mW. Additionally, total power consumption further increases using an analog-to-digital converter and a high-speed modulator, particularly when the data rate exceeds 1Gbps. By removing these power-hungry building blocks, 2Gbps and 5Gbps millimeter-wave CMOS impulse radio receivers were developed with a better power efficiency.
The 2Gbps receiver detects millimeter-wave single-ended pulses using a single-ended CMOS envelope detector, and high-speed data is only processed using a limiting amplifier. The second receiver design contains a differential envelope detector, a voltage control amplifier, a current mode offset canceller and the data is processed using a high-speed comparator with hysteresis.
The general architecture of conventional millimeter-wave QAM receivers is shown in Figure 31 a , where the received signal is downconverted using a local oscillator LO consuming a power of several tens of mW Razavi, ; Mitomoto, Also, total power dissipation will even increase using a high-speed analog-to-digital converter ADC and a high-speed demodulator DMOD , particularly for the multi-Gbps data rate.
The architecture is adopted from that of optical communication receivers due to the similarity between an optical pulse and a millimeter-wave pulse. In the following sections, the pulse receiver design and the measurement results are presented. Multi-Gbps communication will have low power consumption when a received signal is detected without using a high-frequency LO and high-speed data are processed using only a limiting amplifier LA , as shown in Figure 31 b.
Figure 32 a shows the widely used optical receiver architecture Narasimha, ; Le, Here, a low-noise amplifier LNA is not implemented in this work to determine the inherent features of the millimeter-wave pulse receiver. As a result, the receiver consists of a nonlinear amplifier NLA , a five-stage LA, an off-set canceller and an output buffer. To detect the millimeter-wave pulses, a metal-insulator-insulator-metal MIIM diode Rockwell, or a Schottky diode Sankaran, was conventionally used.
And a Schottky diode is not always available in general design rules. To overcome this issue, a common-source amplifier, utilizing a square-law relationship between the drain current I d and the gate voltage V g of an NMOSFET, is used as a detector. At the output of the NLA, the base-band signal is generated as shown in Figure The remainder of the circuitry is designed in the same way as for similar types of optical receivers. The receiver was fabricated by a 90nm CMOS process. A micrograph of the receiver is shown in Figure The millimeter-wave switch in Section 2.
To filter out base-band fluctuations due to switching, a V-band waveguide is inserted between the transmitter and the receiver. Before applying the pulses to the receiver input, the average pulse power is measured using a millimeter-wave power meter. The 60GHz pulses and the demodulated digital signals transmitted at a data rate of 2Gbps are shown in Figure The eye diagram and bit-error rate BER of the receiver are obtained using 2 31 -1 bits of pseudo-random data.
The eye diagram of the receiver is shown in Figure 36 for the data rates of 1 and 2Gbps. In both cases, clear eye openings are observed. The output was mV peak to peak. The measured BER with respect to the average pulse power is plotted in Figure 37 for 1 and 2Gbps data rates. The theoretical BER curves for the case of square-law detection are fitted to the measured data, the shapes of which agree with the square-law detection theory.
The BER of the pulse receiver decreases more rapidly with increasing input power than that of a linear-detection receiver.
Low Power RF Circuit Design in Standard CMOS Technology : Unai Alvarado :
The total power consumption of the pulse receiver including the buffer is The FOM of this receiver is a slightly better than. Product of gain and data rate as a function of power dissipation for the receivers in this work and previously reported optical receivers. It was shown by measuring the scattering parameters that suitable input matching would increase the power gain by 4.
The receiver is also compared with recently reported millimeter-wave receivers in Table 1. Note that digital codes are provided at the output with only The performance of this pulse receiver indicates the possibility of new low-power multi-Gbps wireless communication at the 60GHz band. Besides the digital signal processing, those wireless applications require complex analog circuits operating at very high frequencies RF circuits.
The intention of this research project is to take the next big leap forward in wireless applications, i. Implementing circuit techniques in standard CMOS technologies at those frequencies is again an enormous challenge and will open a lot of new opportunities and applications towards the future due to possibilities in safety monitoring, e. The goal of the proposed project is to perform the necessary fundamental basic research to be able to implement these GHz applications in CMOS technology 45 nm and below. Field of Science wireless signal processing bluetooth.
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Website Contact the organisation. Principal Investigator Michel Steyaert Prof. Administrative Contact Sofie Heroes Ms. Status Closed project. Start date 1 January End date 31 December Development of mm-wave measurement techniques WP-1 2. Design of CMOS RF front-ends in the GHz frequency band WP-3 Since the three objectives are strongly linked to each other characterization of circuits in objective 3 should be designed via the objectives in 2 and measured via the set-up and developed measurement techniques in 1 , and since over the course of the project almost every year a mm-wave CMOS circuit was demonstrated in the aimed frequency range 30 GHzGHz , the project objectives are fully met.
Even better, nowadays circuits are measured over 0. The chip, developed by the research team, demonstrated state-of-the art performance in terms of distance and data-rate. Furthermore, the chip contained an on-chip antenna. A second major achievement is the feasibility to demonstrated plastic-waveguides. Here, we made use of the results developed in the DARWIN project, to establish a novel communication concept that uses cheap plastic fibers and on-chip antennas.
As such, we were able to achieve 10Gbps over 1 meter distance and 2Gbps over 10 meters.
These numbers are highly competitive compared to copper wire line or optical communication. For sure, the research team will continue to investigate the potential of this concept for consumer and automotive applications. Altogether, the research is ended with great success.
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- Fig 415 rf circuit on cmos bulk technology 58 4.
Whereas in the beginning of the DARWIN project, the focus was on basic building blocks, towards the end of the project the focus was clearly on the development of entire radios in the GHz frequency range and the final one was to measure and evaluate new techniques to demonstrate towards the semiconductor industry the capabilities of this frequency range.
This has lead to various publications on a wide range of frequencies: 60GHz, 85GHz E-band communication , GHz wireless connectors and plastic waveguides and even GHz. It is fair to say that thanks to this DARWIN project, not only has KU Leuven maintained its leading position in the field of RF and mm-wave design, it has also allowed us to expand our field of expertise into this new and promising frequency domain. Today, the research group has many collaborations with industry and various follow-up projects thanks to the ERC grant.