diff --git a/CHANGELOG.md b/CHANGELOG.md
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,6 +1,15 @@
 Changelog
 =========
 
+Version 0.1.6.0
+---------------
+
+*September 24, 2019*
+
+<https://github.com/mstksg/emd/releases/tag/v0.1.6.0>
+
+*   Add `hilbertPhase` to *Numeric.HHT*.
+
 Version 0.1.5.1
 ---------------
 
diff --git a/emd.cabal b/emd.cabal
--- a/emd.cabal
+++ b/emd.cabal
@@ -4,12 +4,13 @@
 --
 -- see: https://github.com/sol/hpack
 --
--- hash: 6f95be4c5fda6113919d6156cb567274470a1d3ec81ea31a2efdc8efbb2b4d28
+-- hash: ff41309ce78de40674bacd4a2d67e4f7be21c4e08e289bc0faff8f38d771e3fc
 
 name:           emd
-version:        0.1.5.1
+version:        0.1.6.0
 synopsis:       Empirical Mode Decomposition and Hilbert-Huang Transform
-description:    Please see the README on GitHub at <https://github.com/mstksg/emd#readme>
+description:    Empirical Mode decomposition and Hilbert-Huang Transform in pure
+                Haskell.
 category:       Math
 homepage:       https://github.com/mstksg/emd#readme
 bug-reports:    https://github.com/mstksg/emd/issues
@@ -52,7 +53,7 @@
     , transformers
     , typelits-witnesses
     , vector
-    , vector-sized
+    , vector-sized >=1.4
   default-language: Haskell2010
 
 test-suite emd-test
@@ -87,5 +88,5 @@
     , mwc-random
     , statistics
     , vector
-    , vector-sized
+    , vector-sized >=1.4
   default-language: Haskell2010
diff --git a/src/Numeric/HHT.hs b/src/Numeric/HHT.hs
--- a/src/Numeric/HHT.hs
+++ b/src/Numeric/HHT.hs
@@ -47,6 +47,7 @@
   -- * Hilbert transforms (internal usage)
   , hilbert
   , hilbertIm
+  , hilbertPolar
   , hilbertMagFreq
   ) where
 
@@ -281,10 +282,39 @@
     -> (SVG.Vector v (n + 1) a, SVG.Vector v n a)
 hilbertMagFreq v = (hilbertMag, hilbertFreq)
   where
-    v' = hilbertIm v
+    v'           = hilbertIm v
     hilbertMag   = SVG.zipWith (\x x' -> magnitude (x :+ x')) v v'
     hilbertPhase = SVG.zipWith (\x x' -> phase (x :+ x')) v v'
     hilbertFreq  = SVG.map ((`mod'` 1) . (/ (2 * pi))) $ SVG.tail hilbertPhase - SVG.init hilbertPhase
+
+-- | The polar form of 'hilbert': returns the magnitude and phase of the
+-- discrete hilbert transform of a series.
+--
+-- The computation of magnitude is unique, but computing phase gives us
+-- some ambiguity.  The interpretation of the hilbert transform for
+-- instantaneous frequency is that the original series "spirals" around the
+-- complex plane as time progresses, like a helix.  So, we impose
+-- a constraint on the phase to uniquely determine it: \(\phi_{t+1}\) is
+-- the /minimal valid phase/ such that \(\phi_{t+1} \geq \phi_{t}\).  This
+-- enforces the phase to be monotonically increasing at the slowest
+-- possible detectable rate.
+--
+-- Note that this function effectively resets the initial phase to be zero,
+-- conceptually rotating 'hilbert' to begin on the real axis.
+--
+-- @since 0.1.6.0
+hilbertPolar
+    :: forall v n a. (VG.Vector v a, KnownNat n, RealFloat a)
+    => SVG.Vector v (n + 1) a
+    -> (SVG.Vector v (n + 1) a, SVG.Vector v (n + 1) a)
+hilbertPolar v = (hilbertMag, hilbertPhase)
+  where
+    hilbertMag :: SVG.Vector v (n + 1) a
+    hilbertFreq :: SVG.Vector v n a
+    (hilbertMag, hilbertFreq) = hilbertMagFreq v
+    hilbertPhase :: SVG.Vector v (n + 1) a
+    hilbertPhase = SVG.scanl' (+) 0 hilbertFreq
+
 
 -- | Real part is original series and imaginary part is hilbert transformed
 -- series.  Creates a "helical" form of the original series that rotates