phase - 2025 ACF Regionals

Question

This quantity for a modulated signal differs by a fixed amount for the two streams in I/Q data, which is derived from the narrowband assumption. For 10 points each:

[10h] Name this quantity whose “keying” is plotted on “constellation diagrams” in digital modulation. This quantity names a class of time-invariant vectors that are generalized by analytic signal representations.

ANSWER: phase [accept phasors or phase-shift keying] (The I/Q data of a signal is its decomposition into in-phase and quadrature components.)

[10e] Phasors are representations of functions with this shape, since they encode the amplitude and phase of a signal. Functions with this shape are the usual terms in a Fourier series.

ANSWER: sinusoidal [accept sine or cosine; prompt on periodic]

[10m] In circuit analysis, the ratio of two phasors corresponds to this complex quantity. A generalization of Ohm’s law for inductors and capacitors in AC circuits states that voltage equals current times this quantity.

ANSWER: impedance [prompt on Z]

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Summary


California	2025-02-01	Y	3	16.67	100%	67%	0%
Florida	2025-02-01	Y	3	6.67	67%	0%	0%
Lower Mid-Atlantic	2025-02-01	Y	6	13.33	83%	17%	33%
Midwest	2025-02-01	Y	6	20.00	100%	50%	50%
North	2025-02-01	Y	3	10.00	67%	33%	0%
Northeast	2025-02-01	Y	5	12.00	80%	40%	0%
Pacific Northwest	2025-02-01	Y	2	10.00	50%	50%	0%
South Central	2025-02-01	Y	2	20.00	100%	100%	0%
Southeast	2025-02-01	Y	4	2.50	0%	25%	0%
UK	2025-02-01	Y	10	19.00	100%	70%	20%
Upper Mid-Atlantic	2025-02-01	Y	8	15.00	88%	38%	25%
Upstate NY	2025-02-01	Y	3	3.33	33%	0%	0%

Data


Claremont A	UC Berkeley B	0	10	0	10
UCLA	Claremont B	0	10	10	20
UC Berkeley A	UCSD	0	10	10	20
Florida State A	Valencia A	0	10	0	10
UCF B	Florida B	0	0	0	0
UCF C	Florida A	0	10	0	10
Duke	UNC C	0	10	0	10
Liberty A	Virginia Tech A	0	10	0	10
William & Mary	Liberty B	0	0	0	0
UNC B	South Carolina	10	10	10	30
Virginia A	Liberty C	10	10	0	20
UNC D	Wake Forest	0	10	0	10
Chicago C	Chicago B	0	10	10	20
Chicago D	Missouri	0	10	0	10
Illinois C	Indiana B	10	10	0	20
Indiana A	Illinois B	10	10	10	30
Missoui S&T	Illinois A	10	10	0	20
WashU B	Chicago A	0	10	10	20
Iowa State	Carleton	0	10	10	20
Winona State	Minnesota B	0	10	0	10
Wisconsin B	Wisconsin A	0	0	0	0
Tufts A	Brandeis A	0	10	0	10
Brandeis B	BU	0	0	0	0
Harvard A	Dartmouth A	0	10	10	20
Brown A	UMass Boston	0	10	10	20
Alberta	UBC	0	10	0	10
UW B	UW A	0	0	10	10
ASU	TAMU	0	10	10	20
Texas A	Texas B	0	10	10	20
Louisville A	Georgia Tech B	0	0	0	0
Georgia Tech C	Georgia Tech D	0	0	10	10
Vanderbilt A	Georgia Tech A	0	0	0	0
Bruin A	Tennessee A	0	0	0	0
Oxford C	Bristol	0	10	10	20
Cambridge A	NYU C	0	10	10	20
Oxford A	Cambridge B	10	10	10	30
Manchester	Cambridge C	0	10	10	20
LSE	Cambridge D	0	10	10	20
Cambridge E	Imperial A	0	10	0	10
Warwick A	Durham	10	10	10	30
Imperial B	Warwick B	0	10	0	10
Sheffield	Southampton A	0	10	10	20
Oxford B	Southampton B	0	10	0	10
Maryland A	Columbia B	0	0	10	10
Haverford A	Cornell B	0	10	0	10
Vassar A	George Washington A	0	10	0	10
Maryland B	George Washington B	0	10	0	10
John Jay College	Haverford B	0	10	0	10
Harvard B	MIT A	0	10	0	10
NYU B	Johns Hopkins A	0	10	0	10
Penn A	Penn B	10	10	10	30
Rutgers A	Yale A	10	10	10	30
Binghamton A	Cornell C	0	0	0	0
Cornell D	RIT A	0	10	0	10
ESF A	RIT B	0	0	0	0