7/29/2019 rfic asignment

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ECE 6730: RF Integrated Circuit Design Spring 2009

Assignment #1Topics: Units, Linearity, NoiseDue Date: Jan. 29, 2009

Problem 1: Suppose we wish to deliver 14.3 dBm of power to a 50 antenna at1.9 GHz.

(a) What is the peak-to-peak output swing required of the power amplifier,assuming a sinusoidal output?

(b) Repeat part (a), but this time assume that the output is a triangle wave.

Problem 2: We are designing a system with an LNA whose behavior can be modeledas:

y(t) = 1x(t) + 2x2(t) + 3x

3(t) (1)

where 1 = 10, 2 = 2, and 3 = 0.5. The inputs to the LNA are a desiredsignal at 1 with a peak amplitude of 1 mV, and a blocking signal at 2 with apeak amplitude of 2 V.

(a) Assuming that no filtering takes place before the LNA, what is the gain(in dB) for the desired signal?

(b) If we plan on inserting a SAW (surface acoustic wave) filter before the LNA,and the minimum gain for the desired signal is 19.5 dB, by how many dBmust the filter attenuate the blocking signal at 2?

Problem 3: In class we discussed the IP3 for a system, which quantified the sizeof the third order intermodulation products (output components at 21 2,22 1) relative to the fundamental. In some systems we are more interestedin the size of the second order intermodulation products (output components at1 2, 2 1) relative to the fundamental.

(a) Assuming that the system can be modeled as in (1) from the previousquestion, derive an expression for the AIP2 point (the input amplitude forwhich the second order IM products are equal to the fundamental).

(b) Suppose we know that for an input power of -40 dBm, the power of thefundamental components at the output is -10 dBm and the power of theIM2 components is -50 dBm. What is the IIP2 (input second interceptpoint) of the system?

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7/29/2019 rfic asignment

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ECE 6730: RF Integrated Circuit Design Spring 2009

Figure 1: Schematic for noise factor calculation.

Problem 4: Suppose we have a system that is composed of two blocks, with thefirst block having a gain of 1 = 10 and an input IP3 of AIP3,1 = 1, and thesecond block having a gain of1 = 2 and an input IP3 ofAIP3,2 = 1.

(a) What is the input IP3 of the system as a whole?

(b) What does the system input IP3 become if the order of the blocks is re-versed?

(c) What does this tell us about how we should distribute the gain in a systemif we want to try and maximize the linearity?

Problem 5: Lee: Chapter 11, Problem 6.

Problem 6: Consider the circuit in Fig. 1. Ignore CGD, rO, body effect, and inducedgate noise. Assume all transistors are biased in the saturation region.

(a) Calculate the noise factor of the circuit.

(b) Cp is a parasitic capacitance that is influenced by the physical layout of thecircuit. How does its presence affect the overall noise factor, and should itbe minimized or maximized?

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