VCO + QUADRATURE Design Specifications

VCO:

§ Phase Noise: -85dBc/Hz at f_offset= 10kHz;

Phase Noise: -105dBc/Hz at f_offset= 100kHz;

Phase Noise: -120dBc/Hz at f_offset= 1MHz;

§ We suggest you start with a differential LC oscillator topology. You need to use the inductor models and capacitor models provided in previous assignments.

§ The required tuning range to cover the ISM band is 100 MHz ie. from 2.4GHz to 2.5GHz.You need to have a continuous tuning range of 100MHz provided by using a varactor.

Note: We provide a p+/n-well varactor symbol and model for this design. Be careful how you connect the varactor. For the varactor symbol, download, untar and include the following library (library name is varactorE6314) into your Cadence library path. varactor

Then, you will see the varactor cell view and symbol, under the varactorE6314 library in your library manager window.

Please download this varactor model into your directory, and include it in your model library file list in Analog Environment, when you simulate your circuit. If you need a larger varactor, put several in parallel. Your tuning voltage can range from VSS+100mV to VDD-100mV.

§ In your design, you should consider the ±20% value changes of the passive components in the tank – mainly the capacitors -- due to process variations. Calculate how much this will affect your oscillation frequency; you can assume the inductor value does not change. Include switched capacitors in your LC tank or increase the tuning range provided by the varactor to compensate the frequency changes due to process variations. However, you have to maintain the tuning gain of the VCO below 100MHz/V.

Quadrature:

§ For the quadrature generation we propose to use a passive RC network in the I-channel LO path, and a passive CR network in the Q-channel LO path. Please set the pole of the RC network to the mid-point of your band, which is 2450 MHz. Even though the phase difference between the signals at I and Q channels will be 90° for all frequencies, their magnitude will be equal only at one frequency, which is 2450 MHz. This can be compensated by providing sufficient gain in the LO path so that the buffers act as limiters. You may need to increase the gain of LO buffer that you designed for assignment-#2 to limit the signal, so that LO signals both at I and Q channels will have the same magnitude but 90° phase difference at the LO terminals of your mixers.

§ The phase difference between LO signals on I and Q channel paths at the LO terminals of mixers, should be between 89 and 90degrees.

§ The gain error between LO signals on I and Q channel paths at the LO terminals of mixers should be less than 1dB.

§ You are free to use more complicated quadrature generation arrangements.

Design Goals: Minimize the power consumption.

Input and Output Interfaces:

Simulations: The specifications given above are for ‘tt’ (typical, typical process) and 25°. You also have to simulate your design at ‘ss’ and ‘ff’ corners, and -40° and +85° temperatures.

Submission: You have to submit the following materials on November 26th 2005

§ Transistor level schematic of your design

§ Top-level schematics for all test setups. (Before you submit your design, please create a symbol for your VCO and Buffers, and bring out all input, output, power supply and bias pins. Then create top-level test benches, and submit them with your design.)

§ Simulations:

1) Frequency Tuning Curve: LO frequency versus tuning voltage.

2) Run a transient simulation and attach VCO output waveform, RC/CR output waveforms, and LO buffers output waveforms.

3) Phase Noise versus Offset Frequency

4) Table of tuning gain of VCO, gain/phase error of RC/CR network (at 2.4GHz, 2.45GHz and 2.5GHz) and power consumption at all temperatures and corners.

Please submit all your material in one pdf or postscript file. It is not necessary to submit hardcopies. If you are working in a group, please include your partner's name and email in the email and cc them on the message.