# Source code for skrf.frequency



'''
.. currentmodule:: skrf.frequency
========================================
frequency (:mod:skrf.frequency)
========================================

Provides a frequency object and related functions.

Most of the functionality is provided as methods and properties of the
:class:Frequency Class.

Frequency Class
===============
.. autosummary::
:toctree: generated/

Frequency

Functions
=============

.. autosummary::
:toctree: generated/

overlap_freq

'''

# from matplotlib.pyplot import gca,plot, autoscale
from numpy import pi, linspace, logspace
import numpy as npy
from numpy import fft, shape, gradient# used to center attribute t at 0
import re
from .util import slice_domain,find_nearest_index
#from .constants import ZERO
global ZER0
ZERO=1e-4 # currently needed to allow frequency __eq__ method to work
# comparing 1e-4hz is very small for most applications

[docs]class Frequency(object):
'''
A frequency band.

The frequency object provides a convenient way to work with and
access a frequency band. It contains  a frequency vector as well as
a frequency unit. This allows a frequency vector in a given unit
to be available (:attr:f_scaled), as well as an absolute frequency
axis in 'Hz'  (:attr:f).

A Frequency object can be created from either (start, stop, npoints)
using the default constructor, :func:__init__. Or, it can be
created from an arbitrary frequency vector by using the class
method :func:from_f.

Internally, the frequency information is stored in the f property
combined with the unit property. All other properties, start
stop, etc are generated from these.
'''
unit_dict = {\
'hz':'Hz',\
'khz':'KHz',\
'mhz':'MHz',\
'ghz':'GHz',\
'thz':'THz'\
}
multiplier_dict={
'hz':1,\
'khz':1e3,\
'mhz':1e6,\
'ghz':1e9,\
'thz':1e12\
}

[docs]    def __init__(self,start=0, stop=0, npoints=0, unit='ghz', sweep_type='lin'):
'''
Frequency initializer.

Creates a Frequency object from start/stop/npoints and a unit.
Alternatively, the class method :func:from_f can be used to
create a Frequency object from a frequency vector instead.

Parameters
----------
start : number
start frequency in  units of unit
stop : number
stop frequency in  units of unit
npoints : int
number of points in the band.
unit : ['hz','khz','mhz','ghz']
frequency unit of the band. This is used to create the
attribute :attr:f_scaled. It is also used by the
:class:~skrf.network.Network class for plots vs.
frequency.
sweep_type : ['lin', 'log']
type of the sweep. 'lin' for linear and 'log' for logarithmic.

Notes
--------
The attribute unit sets the property freqMultiplier, which is used
to scale the frequency when f_scaled is referenced.

---------
from_f : constructs a Frequency object from a frequency

Examples
---------

>>> wr1p5band = Frequency(500,750,401, 'ghz')

'''
self._unit = unit.lower()
self.sweep_type = sweep_type

start =  self.multiplier * start
stop = self.multiplier * stop

if sweep_type.lower() == 'lin':
self.f = linspace(start, stop, npoints)
elif sweep_type.lower() == 'log':
self.f = logspace(npy.log10(start), npy.log10(stop), npoints)
else:
raise ValueError('Sweep Type not recognized')

def __str__(self):
'''
'''
try:
output =  \
'%s-%s %s, %i pts' % \
(self.f_scaled, self.f_scaled[-1], self.unit, self.npoints)
except (IndexError):
output = "[no freqs]"

return output

def __repr__(self):
'''
'''
return self.__str__()

def __getitem__(self,key):
'''
Slices a Frequency object based on an index, or human readable string

Parameters
-----------
key : str, or slice
if int; then it is interpreted as the index of the frequency
if str, then should be like '50.1-75.5ghz', or just '50'.
If the frequency unit is omited then self.frequency.unit is
used.

Examples
-----------
>>> b = rf.Frequency(50,100,101,'ghz')
>>> a = b['80-90ghz']
>>> a.plot_s_db()
'''

output = self.copy()

if isinstance(key, str):

# they passed a string try and do some interpretation
re_numbers = re.compile('.*\d')
re_hyphen = re.compile('\s*-\s*')
re_letters = re.compile('[a-zA-Z]+')

freq_unit = re.findall(re_letters,key)

if len(freq_unit) == 0:
freq_unit = self.unit
else:
freq_unit = freq_unit

key_nounit = re.sub(re_letters,'',key)
edges  = re.split(re_hyphen,key_nounit)

edges_freq = Frequency.from_f([float(k) for k in edges],
unit = freq_unit)
if len(edges_freq) ==2:
slicer=slice_domain(output.f, edges_freq.f)
elif len(edges_freq)==1:
key = find_nearest_index(output.f, edges_freq.f)
slicer = slice(key,key+1,1)
else:
raise ValueError()
try:
output.f = npy.array(output.f[slicer]).reshape(-1)
return output
except(IndexError):
raise IndexError('slicing frequency is incorrect')

if output.f.shape > 0:
output.f = npy.array(output.f[key]).reshape(-1)
else:
output.f = npy.empty(shape=(0))

return output

[docs]    @classmethod
def from_f(cls,f, *args,**kwargs):
'''
Construct Frequency object from a frequency vector.

The unit is set by kwarg 'unit'

Parameters
-----------
f : array-like
frequency vector

*args, **kwargs : arguments, keyword arguments
passed on to  :func:__init__.

Returns
--------
myfrequency : :class:Frequency object
the Frequency object

Examples
-----------
>>> f = npy.linspace(75,100,101)
>>> rf.Frequency.from_f(f, unit='ghz')
'''
temp_freq =  cls(0,0,0,*args, **kwargs)
temp_freq.f = npy.array(f) * temp_freq.multiplier
return temp_freq

def __eq__(self, other):
#return (list(self.f) == list(other.f))
# had to do this out of practicality
if len(self.f) != len(other.f):
return False
elif len(self.f) == len(other.f) == 0:
return True
else:
return (max(abs(self.f-other.f)) < ZERO)

def __ne__(self,other):
return (not self.__eq__(other))

def __len__(self):
'''
The number of frequeny points
'''
return self.npoints

def __mul__(self,other):
out = self.copy()
out.f = self.f*other
return out

def __rmul__(self,other):
out = self.copy()
out.f = self.f*other
return out

def __div__(self,other):
out = self.copy()
out.f = self.f/other
return out

@property
def start(self):
'''
starting frequency in Hz
'''
return self.f

@property
def start_scaled(self):
'''
starting frequency in :attr:unit's
'''
return self.f_scaled
@property
def stop_scaled(self):
'''
stop frequency in :attr:unit's
'''
return self.f_scaled[-1]

@property
def stop(self):
'''
stop frequency in Hz
'''
return self.f[-1]

@property
def npoints(self):
'''
number of points in the frequency
'''
return len(self.f)

@npoints.setter
def npoints(self, n):
'''
set the number of points in the frequency
'''
self.f = linspace(self.start, self.stop, n)

@property
def center(self):
'''
Center frequency in Hz

Returns
---------
center : number
the exact center frequency in units of hz
'''
return self.start + (self.stop-self.start)/2.

@property
def center_idx(self):
'''
closes idx of :attr:f to the center frequency
'''
return int(self.npoints)/2

@property
def center_scaled(self):
'''
Center frequency in :attr:unit's

Returns
---------
center : number
the exact center frequency in units of :attr:unit's
'''
return self.start_scaled + (self.stop_scaled-self.start_scaled)/2.

@property
def step(self):
'''
the inter-frequency step size (in hz) for evenly-spaced
frequency sweeps

see df for general case
'''
return self.span/(self.npoints-1.)

@property
def step_scaled(self):
'''
the inter-frequency step size (in self.unit) for evenly-spaced
frequency sweeps

see df for general case
'''
return self.span_scaled/(self.npoints-1.)

@property
def span(self):
'''
the frequency span
'''
return abs(self.stop-self.start)

@property
def span_scaled(self):
'''
the frequency span
'''
return abs(self.stop_scaled-self.start_scaled)

@property
def f(self):
'''
Frequency vector  in Hz

Returns
----------
f :  :class:numpy.ndarray
The frequency vector  in Hz

----------
f_scaled : frequency vector in units of :attr:unit
w : angular frequency vector in rad/s
'''

return self._f

@f.setter
def f(self,new_f):
'''
sets the frequency object by passing a vector in Hz
'''
self._f = npy.array(new_f)

@property
def f_scaled(self):
'''
Frequency vector in units of :attr:unit

Returns
---------
f_scaled :  :class:numpy.ndarray
A frequency vector in units of :attr:unit

---------
f : frequency vector in Hz
w : frequency vector in rad/s
'''
return self.f/self.multiplier

@property
def w(self):
'''

Returns
----------
w :  :class:numpy.ndarray

----------
f_scaled : frequency vector in units of :attr:unit
f :  frequency vector in Hz
'''
return 2*pi*self.f

@property
def df(self):
'''
the gradient of the frequency vector (in hz)
'''
@property
def df_scaled(self):
'''
the gradient of the frequency vector (in self.unit)
'''
@property
def dw(self):
'''
'''

@property
def unit(self):
'''
Unit of this frequency band.

Possible strings for this attribute are:
'hz', 'khz', 'mhz', 'ghz', 'thz'

Setting this attribute is not case sensitive.

Returns
---------
unit : string
lower-case string representing the frequency units
'''
return self.unit_dict[self._unit]

@unit.setter
def unit(self,unit):
self._unit = unit.lower()

@property
def multiplier(self):
'''
Multiplier for formatting axis

This accesses the internal dictionary multiplier_dict using
the value of :attr:unit

Returns
---------
multiplier : number
multiplier for this Frequencies unit
'''
return self.multiplier_dict[self._unit]

[docs]    def copy(self):
'''
returns a new copy of this frequency
'''
freq =  Frequency.from_f(self.f, unit='hz')
freq.unit = self.unit
return freq

@property
def t(self):
'''
time vector in s.

t_period = 1/f_step
'''
return linspace(-.5/self.step , .5/self.step, self.npoints)

@property
def t_ns(self):
'''
time vector in ns.

t_period = 1/f_step
'''
return self.t*1e9

[docs]    def round_to(self, val = 'hz'):
'''
Round off frequency values to a specified precision.

This is useful for dealing with finite precision limitations of
VNA's and/or other software

Parameters
-----------
val : string or number
if val is a string it should  be a frequency unit
(ie 'hz', 'mhz',etc). if its a number, then this returns
f = f-f%val

Examples
---------
>>>f = skrf.Frequency.from_f([.1,1.2,3.5],unit='hz')
>>>f.round_to('hz')

'''
if isinstance(val, str):
val = self.multiplier_dict[val.lower()]

self.f = npy.round_(self.f/val)*val

[docs]    def overlap(self,f2):
'''
Calculates overlapping frequency  between self and f2

---------

overlap_freq

'''
return overlap_freq(self, f2)

[docs]def overlap_freq(f1,f2):
'''
Calculates overlapping frequency between f1 and f2.

Or, put more accurately, this returns a Frequency that is the part
of f1 that is overlapped by f2. The resultant start frequency is
the smallest f1.f that is greater than f2.f.start, and the stop
frequency is the largest f1.f that is smaller than f2.f.stop.

This way the new frequency overlays onto f1.

Parameters
------------
f1 : :class:Frequency
a  frequency object
f2 : :class:Frequency
a  frequency object

Returns
----------
f3 : :class:Frequency
part of f1 that is overlapped by f2

'''
if f1.start > f2.stop:
raise ValueError('Out of bounds. f1.start > f2.stop')
elif f2.start > f1.stop:
raise ValueError('Out of bounds. f2.start > f1.stop')

start = max(f1.start, f2.start)
stop = min(f1.stop, f2.stop)
f = f1.f[(f1.f>=start) & (f1.f<=stop)]
freq =  Frequency.from_f(f, unit = 'hz')
freq.unit = f1.unit
return freq

def f_2_frequency(f):
'''
converts a frequency vector to a Frequency object

Depricated
-------------
Use the class method :func:Frequency.from_f
convenience function