# Can phase shift keying delay a wave further?

• Crystal037
In summary, the author suggests that we add the phase 4pi instead of subtracting it from the cosine function. This would delay the wave more, but it doesn't matter because the sign of the phase difference doesn't matter here.

#### Crystal037

Homework Statement
Here we have subtracted the phase 4pi from S2 than S1. Why
Relevant Equations
y=a cos (wt)

See fig(a), S1Q=7lambda
S2Q=9lambda
I think since source S2 is lagging behind. So, we should add the phase 4pi instead of subtracting it from the cosine function. Wouldn't subtracting the phase further delay the wave more.

Last edited:
Delta2
I vote for a very poorly worded explanation! Using the Fig 10.9(a) I agree with your statement.

Unfortunately, if you look at their describing equation (S2- S1=2λ, near the top of the page) the equations they give are consistent.

edit: Fortunately in this case it doesn't matter because the sign of the phase difference doesn't matter here. That's the usual case when working with optics. If working with electrical signals (for instance comparing two signals) it may make a difference. /edit:

Just another case of poor copy editing on the part of the book publisher.

Cheers,
Tom

p.s. Good catch Crystal!

So am I right that y2=a cos(wt+4pi)

Crystal037 said:
So am I right that y2=a cos(wt+4pi)

Cheers,
Tom

Thanks Tom. G but how will it make a difference in electrical signal.

One example would be in data transmission using Phase Shift Keying (PSK). This method uses a fixed frequency transmitting data but varies the phase dependent on the data value at that instant.

Notice that the phase is shifted by 180° as the data changes between '0' and '1'.

(I hope the image shows, it doesn't appear in my Preview. It's the big image on the right of the link with a Black background.)

image found with:

Cheers,
Tom

## 1. What is phase shift keying (PSK)?

Phase shift keying is a digital modulation technique used in communication systems to transmit data over a carrier wave by changing the phase of the wave. It is commonly used in wireless communication systems such as WiFi and Bluetooth.

## 2. How does PSK delay a wave further?

PSK works by encoding data as different phase shifts of the carrier wave. By changing the phase of the wave, the signal can be delayed or advanced in time, effectively shifting the wave further along the time axis. This allows for efficient transmission of data over long distances.

## 3. Can PSK delay a wave indefinitely?

No, PSK cannot delay a wave indefinitely. The amount of delay that can be achieved depends on the modulation scheme used and the characteristics of the communication channel. Eventually, the signal will become too distorted to be accurately decoded.

## 4. What are the advantages of using PSK for communication?

PSK has several advantages over other modulation techniques, including increased data transmission rates, improved signal-to-noise ratio, and better resistance to interference. It also allows for efficient use of bandwidth, making it a popular choice for wireless communication systems.

## 5. Are there any drawbacks to using PSK?

One potential drawback of PSK is its susceptibility to phase noise, which can cause errors in the transmitted data. This can be mitigated by using error correction techniques. Additionally, PSK is more complex and requires more processing power compared to simpler modulation schemes such as amplitude shift keying (ASK).

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