# CORDIC demystified

CORDIC means COordinate Rotation Digital Computer; a little difficult of an acronym to remember. This is used to find an angle (Φ) made line joining origin and point (x,y) with positive x-axis. The algorithm is like this, Rotate the point (x,y) by +45º. If the new y co-ordinate become negative, then it says (Φ) angle be estimated … Continue reading CORDIC demystified

# CDMA RAKE

One evening thought: The desire to achieve high through put or data rates is limited by multi-path nature of wireless channels. Reduced symbol time enables increased data rates but multi-path nature of the channel results in ISI (Inter symbol interference). ISI occurs when the symbol time is less than delay spread of the channel. So, if … Continue reading CDMA RAKE

# Relation between BER and PER

Its interesting to know that it depends on size of packet(N) A packet is error if one or more number of bits are errors. P(Ne>=1) = 1-P(Ne=0) Pb = Probability of bit error (Pb+1-Pb)^N = Nc0*(Pb)^N + Nc1*(Pb)^(N-1)*(1-Pb)+ .....+ NcN*(1-Pb)^N P(Ne=0) = (1-Pb)^N P(Ne>=1) = 1 - (1-Pb)^N For suppose in Bluetooth, a BER constraint … Continue reading Relation between BER and PER

# Poison puzzle

One among 100 bottles of water is poisoned. What is the minimum number of people required to find the poisoned bottle. [It takes an hour for the poison to effect on the person, and you have only one hour to find the poised bottle] mail me to know the answer...

# Convolution Interleaver

The below figure is being referred in many links on the web to explain convolution interleaver. Should n't the output be like ....X0,X-3,X-6,X-9,X4,X1,X-2,X-5.... instead of ...X0,X-3,X-6,X-9,X4,X-2,X-5,... as shown in figure. Many of the below links refer to this same figure: [1]https://wiki.cse.buffalo.edu/cse545/content/burst-error-correcting-codes [2 https://en.wikipedia.org/wiki/Burst_error-correcting_code#Convolutional_interleaver

# BB to PB to BB conversion

In Heterodyne receiver, RF frequency is converted to IF frequency and then IF is converted to Base band. (Two mixers?) In monodyne receiver, RF frequency is directly converted to Base Band. (One mixer).