ext/dsent/model/optical/RingDetector.cc - public/gem5 - Git at Google

 /* Copyright (c) 2012 Massachusetts Institute of Technology
  *
  * Permission is hereby granted, free of charge, to any person obtaining a copy
  * of this software and associated documentation files (the "Software"), to deal
  * in the Software without restriction, including without limitation the rights
  * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
  * copies of the Software, and to permit persons to whom the Software is
  * furnished to do so, subject to the following conditions:
  *
  * The above copyright notice and this permission notice shall be included in
  * all copies or substantial portions of the Software.
  *
  * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
  * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
  * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
  * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
  * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
  * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
  * THE SOFTWARE.
  */

 #include "model/optical/RingDetector.h"

 #include <cmath>

 #include "util/Constants.h"
 #include "model/PortInfo.h"
 #include "model/TransitionInfo.h"
 #include "model/EventInfo.h"
 #include "model/std_cells/StdCell.h"
 #include "model/std_cells/StdCellLib.h"
 #include "model/optical_graph/OpticalWaveguide.h"
 #include "model/optical_graph/OpticalDetector.h"
 #include "model/optical_graph/OpticalFilter.h"
 #include "model/timing_graph/ElectricalDriver.h"
 #include "model/timing_graph/ElectricalNet.h"

 namespace DSENT
 {
     // TODOs for this model
     // Add the other receiver topologies from [Georgas, CICC 2011]
     // Split integ_time_ratio = SA integ time ratio
     // Right now perfect clock gating is assumed...may not be what we want

     // Constants
     const String RingDetector::INTEGRATINGSENSEAMP = "INTSA";

     RingDetector::RingDetector(const String& instance_name_, const TechModel* tech_model_)
         : OpticalModel(instance_name_, tech_model_), OpticalReceiver()
     {
         initParameters();
         initProperties();
     }

     RingDetector::~RingDetector()
     {}

     void RingDetector::initParameters()
     {
         addParameterName("DataRate");
         addParameterName("InStart");
         addParameterName("InEnd");
         addParameterName("DetStart");
         addParameterName("DetEnd");
         addParameterName("DropAll");
         addParameterName("Topology");
         return;
     }

     void RingDetector::initProperties()
     {
         return;
     }

     void RingDetector::constructModel()
     {
         // Get parameters
         WavelengthGroup in_wavelengths = makeWavelengthGroup(getParameter("InStart"), getParameter("InEnd"));
         WavelengthGroup det_wavelengths = makeWavelengthGroup(getParameter("DetStart"), getParameter("DetEnd"));
         int number_wavelengths = det_wavelengths.second - det_wavelengths.first + 1;
         bool drop_all = getParameter("DropAll");
         const String& topology = getParameter("Topology");

         // Set some generated properties
         getGenProperties()->set("NumberWavelengths", number_wavelengths);

         // Create device area result
         addAreaResult(new AtomicResult("Photonic"));
         // Create electrical results
         createElectricalAtomicResults();
         if (topology == INTEGRATINGSENSEAMP) addEventResult(new AtomicResult("Receive"));
         else ASSERT(false, "[Error] " + getInstanceName() + " -> Unknown receiver topology (" + topology + ")!");

         // Create optical ports
         createOpticalInputPort(         "In",   in_wavelengths);
         createOpticalOutputPort(        "Out",  in_wavelengths);
         // Create the filter and modulator
         createFilter(                   "RingFilter",   in_wavelengths, drop_all, det_wavelengths);
         createDetector(                 "RingDetector", det_wavelengths, this);
         OpticalFilter* ring_filter = getFilter("RingFilter");
         OpticalDetector* ring_detector = getDetector("RingDetector");
         // Connect the filter and modulator
         getWaveguide("In")->addDownstreamNode(ring_filter);
         ring_filter->addDownstreamNode(getWaveguide("Out"));
         ring_filter->setDropPort(ring_detector);

         // Create electrical ports
         createOutputPort("Out", makeNetIndex(0, number_wavelengths-1));
         // Create net
         createNet("OutVFO");
         // Create output driver
         createDriver("OutDriver", false);
         // Connect driver
         getDriver("OutDriver")->addDownstreamNode(getNet("OutVFO"));
         // Connect output
         assignVirtualFanout("Out", "OutVFO");

         // Precompute some technology values
         precomputeTech();

         return;
     }

     void RingDetector::updateModel()
     {
         // Get some generated properties
         unsigned int number_wavelengths = getGenProperties()->get("NumberWavelengths");

         // Get tech model numbers
         double ring_area = getTechModel()->get("Ring->Area");
         double thru_loss = getTechModel()->get("Ring->ThroughLoss");
         double drop_loss = getTechModel()->get("Ring->DropLoss");
         double pd_loss = getTechModel()->get("Photodetector->Loss");
         double pd_responsivity = getTechModel()->get("Photodetector->Responsivity");

         // Design the receiver
         designReceiver();

         // Update losses
         // Connect the filter and modulator
         OpticalFilter* ring_filter = getFilter("RingFilter");
         OpticalDetector* ring_detector = getDetector("RingDetector");
         ring_filter->setLoss(thru_loss * number_wavelengths);
         ring_filter->setDropLoss(drop_loss + thru_loss * number_wavelengths);
         ring_detector->setLoss(pd_loss);
         ring_detector->setResponsivity(pd_responsivity);
         // Update device area
         getAreaResult("Photonic")->setValue(ring_area * (number_wavelengths));

         return;
     }

     void RingDetector::useModel()
     {
         // Get parameters
         const String& topology = getParameter("Topology");

         // Get some generated properties
         unsigned int number_wavelengths = getGenProperties()->get("NumberWavelengths");

         // Get optical input transition info
         const TransitionInfo& in_trans = getOpticalInputPort("In")->getTransitionInfo();

         // Get tech models
         double vdd = getTechModel()->get("Vdd");
         // Get caps
         double unit_gate_cap = getTechModel()->get("Gate->MinWidth").toDouble() * getTechModel()->get("Gate->CapPerWidth").toDouble();
         double unit_drain_cap = getTechModel()->get("Gate->MinWidth").toDouble() * getTechModel()->get("Drain->CapPerWidth").toDouble();
         double inv_x1_gate_cap = getTechModel()->getStdCellLib()->getStdCellCache()->get("INV_X1->Cap->A");
         double inv_x1_drain_cap = getTechModel()->getStdCellLib()->getStdCellCache()->get("INV_X1->Cap->Y");

         // Construct a simple sense-amp model
         if(topology == INTEGRATINGSENSEAMP)
         {
             // Use ratios from the receiver published in [Georgas, ESSCIRC 2011]
             // Note:
             // The numbers in the paper (43fJ/b, 50 fJ/b in the cited work) is done with the clock buffer (there are 4 receivers),
             // capacitive DAC, and extra output flops used in the physical layout, as the compared receiver is extremely conservative
             // We simplified this model to not have the capacitive DAC, the clock buffer (since this is an individual receiver), or
             // the extra output flops (since receiver structure is already a posedge flop functionally).
             // Look for an upcoming paper [Georgas, JSSC 2012] (when it is published) for the power breakdown pie-chart for the receiver.
             // This model only models the latch (sampler) and the dynamic to static (RS latch) part of the design, which is all you really
             // need in the receiver.

             // Gate caps
             double c_gate_sampler = unit_gate_cap * (4 * 2.0 + 2 * 1.0 + 2 * 3.0 + 2 * 5.0) + unit_gate_cap * (2 * 6.0 + 2 * 1.0) + inv_x1_gate_cap;
             double c_gate_rslatch = unit_gate_cap * (4 * 1.0) + inv_x1_gate_cap;
             // Drain caps
             double c_drain_sampler = unit_drain_cap * (2 * 2.0 + 2 * 1.0 + 3 * 5.0 + 1 * 3.0) + inv_x1_drain_cap;
             double c_drain_rslatch = unit_drain_cap * (2 * 6.0) + inv_x1_drain_cap;
             // Sum up cap switched for the sampler
             double c_sampler = c_gate_sampler + c_drain_sampler;
             double c_rslatch = c_gate_rslatch + c_drain_rslatch;
             // Average cap switched
             // Sampler is differential, one side will always switch (R or S in the latch) regardless of probability
             double avg_cap = c_sampler + c_rslatch * in_trans.getProbability0() * in_trans.getProbability1();

             // Get parameters corresponding to a unit-inverter
             double unit_leak_0 = getTechModel()->getStdCellLib()->getStdCellCache()->get("INV_X1->Leakage->!A");
             double unit_leak_1 = getTechModel()->getStdCellLib()->getStdCellCache()->get("INV_X1->Leakage->A");

             // Approximate leakage (curve fit with design)
             double total_leakage = 0.5 * (unit_leak_0 + unit_leak_1) * 7.43;

             // Create results
             getEventResult("Receive")->setValue(vdd * vdd * avg_cap * number_wavelengths);
             getNddPowerResult("Leakage")->setValue(total_leakage * number_wavelengths);

         }
         else ASSERT(false, "[Error] " + getInstanceName() + " -> Unknown receiver topology (" + topology + ")!");

         return;
     }

     void RingDetector::propagateTransitionInfo()
     {
         // Propagate probabilities from optical input to electrical output port
         getOutputPort("Out")->setTransitionInfo(getOpticalInputPort("In")->getTransitionInfo());

         return;
     }

     void RingDetector::precomputeTech()
     {
         // Get parameters
         const double data_rate = getParameter("DataRate");
         const String& topology = getParameter("Topology");

         // Get tech model numbers
         double pd_cap = getTechModel()->get("Photodetector->Cap");
         double parasitic_cap = getTechModel()->get("Photodetector->ParasiticCap");
         double apd = getTechModel()->get("Photodetector->AvalancheGain");
         double vdd = getTechModel()->get("Vdd");

         // Constants shortcuts
         double pi = Constants::pi;
         double k = Constants::k;
         double q = Constants::q;
         double T = getTechModel()->get("Temperature");

         if(topology == INTEGRATINGSENSEAMP)
         {
             // Get more tech parameters
             double integ_time_ratio = getTechModel()->get("Receiver->Int->IntegrationTimeRatio");
             double BER = getTechModel()->get("SenseAmp->BER");
             double CMRR = getTechModel()->get("SenseAmp->CMRR");
             double offset_comp_bits = getTechModel()->get("SenseAmp->OffsetCompensationBits");
             double offset = getTechModel()->get("SenseAmp->OffsetRatio").toDouble() * vdd;
             double supply_noise_rand = getTechModel()->get("SenseAmp->SupplyNoiseRandRatio").toDouble() * vdd;
             double supply_noise_det = getTechModel()->get("SenseAmp->SupplyNoiseDetRatio").toDouble() * vdd;
             double noise_margin = getTechModel()->get("SenseAmp->NoiseMargin");
             double jitter_ratio = getTechModel()->get("SenseAmp->JitterRatio");

             // Approximate tao using FO4
             double unit_drain_cap = getTechModel()->get("Gate->MinWidth").toDouble() * getTechModel()->get("Drain->CapPerWidth").toDouble();
             double c_g = getTechModel()->getStdCellLib()->getStdCellCache()->get("INV_X1->Cap->A");
             double c_d = getTechModel()->getStdCellLib()->getStdCellCache()->get("INV_X1->Cap->Y");
             double r_o = getTechModel()->getStdCellLib()->getStdCellCache()->get("INV_X1->DriveRes->Y");
             // Calculate sense amp tau from sense amp output loading
             double tau = r_o * (c_g + c_d);
             // Set output inverter drive strength
             getDriver("OutDriver")->setOutputRes(r_o);

             // Calculate sense amp input cap based on schematic
             double sense_amp_cap_in = unit_drain_cap * (2.0 + 3.0 + 5.0 + 1.0);

             // Residual offset
             double v_residual = 3 * offset / pow(2, offset_comp_bits);
             // Noise
             double v_noise = supply_noise_rand * supply_noise_rand / (CMRR * CMRR);
             // Sense amp voltage build-up minimum
             double v_sense = vdd * exp(-(1 - integ_time_ratio) / (data_rate * tau)) + noise_margin + v_residual + supply_noise_det / CMRR;
             // Sigmas corresponding to BER
             double sigma = calcInvNormCdf(BER);

             //K_int is the time the bit is valid for evaluation

             // Total input cap load
             double input_node_cap = sense_amp_cap_in + pd_cap + parasitic_cap;
             double z_int = integ_time_ratio / (data_rate * input_node_cap); //should use K_int

             // Store precalculated values
             m_quad_a_ = 1 - (sigma * sigma * jitter_ratio * jitter_ratio);
             m_quad_b1_ = - 2 * pi / 2 * sigma * sigma * q * 0.7 * data_rate;
             m_quad_b2_ = -2 * v_sense / (z_int * apd);
             m_quad_c_ = 1 / (z_int * z_int) * (v_sense * v_sense - sigma * sigma * (k * T / input_node_cap + v_noise));
         }
         else ASSERT(false, "[Error] " + getInstanceName() + " -> Unknown receiver topology (" + topology + ")!");

         return;
     }

     void RingDetector::designReceiver()
     {
         // Get some generated properties
         unsigned int number_wavelengths = getGenProperties()->get("NumberWavelengths");

         // Get relevant properties/parameters
         const String& topology = getParameter("Topology");

         // Construct a simple sense-amp model
         if(topology == INTEGRATINGSENSEAMP)
         {
             // No really good way to estimate the area...can assume each receiver is the size of 40 inverters, which is
             // about the right size for just the sense amp in the layout
             double unit_area_active = getTechModel()->getStdCellLib()->getStdCellCache()->get("INV_X1->Area->Active");
             double unit_area_metal1 = getTechModel()->getStdCellLib()->getStdCellCache()->get("INV_X1->Area->Metal1Wire");
             getAreaResult("Active")->setValue(unit_area_active * 40 * number_wavelengths);
             getAreaResult("Metal1Wire")->setValue(unit_area_metal1 * 40 * number_wavelengths);
         }
         else ASSERT(false, "[Error] " + getInstanceName() + " -> Unknown receiver topology (" + topology + ")!");

         return;
     }

     double RingDetector::getSensitivity(double ER_dB_) const
     {
         // Get parameters
         const String& topology = getParameter("Topology");
         // Turn extinction ratio into a ratio from dB scale
         double ER = pow(10, ER_dB_ / 10);

         // Initialize sensitivity
         double sensitivity = 1e99;
         // Construct a simple sense-amp model
         if(topology == INTEGRATINGSENSEAMP)
         {
             // Scale photodetector shot noise using ER, add rest of noise source
             double b = m_quad_b1_ * (1 + ER) / (2 * (ER - 1)) + m_quad_b2_;

             // Find sensitivity (-b + sqrt(b^2-4ac)) / 2a
             sensitivity = ((-b + sqrt(b * b - 4 * m_quad_a_ * m_quad_c_)) / (2 * m_quad_a_));
         }
         else ASSERT(false, "[Error] " + getInstanceName() + " -> Unknown receiver topology (" + topology + ")!");

         return sensitivity;
     }

     double RingDetector::calcInvNormCdf(double num_)
     {
         // 53 bit precision for double FP
         unsigned int num_iterations = 20;
         // Upperbound the step
         double step = 20;
         double out = step;
         // Iteratively guess and check calculation
         for (unsigned int i = 0; i < num_iterations; ++i)
         {
             double current = 0.5 * erfc(out / sqrt(2));
             if (current > num_) out += step;
             else out -= step;
             step = step * 0.5;
         }

         return out;
     }

 } // namespace DSENT
	/* Copyright (c) 2012 Massachusetts Institute of Technology
	*
	* Permission is hereby granted, free of charge, to any person obtaining a copy
	* of this software and associated documentation files (the "Software"), to deal
	* in the Software without restriction, including without limitation the rights
	* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
	* copies of the Software, and to permit persons to whom the Software is
	* furnished to do so, subject to the following conditions:
	*
	* The above copyright notice and this permission notice shall be included in
	* all copies or substantial portions of the Software.
	*
	* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
	* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
	* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
	* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
	* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
	* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
	* THE SOFTWARE.
	*/

	#include "model/optical/RingDetector.h"

	#include <cmath>

	#include "util/Constants.h"
	#include "model/PortInfo.h"
	#include "model/TransitionInfo.h"
	#include "model/EventInfo.h"
	#include "model/std_cells/StdCell.h"
	#include "model/std_cells/StdCellLib.h"
	#include "model/optical_graph/OpticalWaveguide.h"
	#include "model/optical_graph/OpticalDetector.h"
	#include "model/optical_graph/OpticalFilter.h"
	#include "model/timing_graph/ElectricalDriver.h"
	#include "model/timing_graph/ElectricalNet.h"

	namespace DSENT
	{
	// TODOs for this model
	// Add the other receiver topologies from [Georgas, CICC 2011]
	// Split integ_time_ratio = SA integ time ratio
	// Right now perfect clock gating is assumed...may not be what we want

	// Constants
	const String RingDetector::INTEGRATINGSENSEAMP = "INTSA";

	RingDetector::RingDetector(const String& instance_name_, const TechModel* tech_model_)
	: OpticalModel(instance_name_, tech_model_), OpticalReceiver()
	{
	initParameters();
	initProperties();
	}

	RingDetector::~RingDetector()
	{}

	void RingDetector::initParameters()
	{
	addParameterName("DataRate");
	addParameterName("InStart");
	addParameterName("InEnd");
	addParameterName("DetStart");
	addParameterName("DetEnd");
	addParameterName("DropAll");
	addParameterName("Topology");
	return;
	}

	void RingDetector::initProperties()
	{
	return;
	}

	void RingDetector::constructModel()
	{
	// Get parameters
	WavelengthGroup in_wavelengths = makeWavelengthGroup(getParameter("InStart"), getParameter("InEnd"));
	WavelengthGroup det_wavelengths = makeWavelengthGroup(getParameter("DetStart"), getParameter("DetEnd"));
	int number_wavelengths = det_wavelengths.second - det_wavelengths.first + 1;
	bool drop_all = getParameter("DropAll");
	const String& topology = getParameter("Topology");

	// Set some generated properties
	getGenProperties()->set("NumberWavelengths", number_wavelengths);

	// Create device area result
	addAreaResult(new AtomicResult("Photonic"));
	// Create electrical results
	createElectricalAtomicResults();
	if (topology == INTEGRATINGSENSEAMP) addEventResult(new AtomicResult("Receive"));
	else ASSERT(false, "[Error] " + getInstanceName() + " -> Unknown receiver topology (" + topology + ")!");

	// Create optical ports
	createOpticalInputPort( "In", in_wavelengths);
	createOpticalOutputPort( "Out", in_wavelengths);
	// Create the filter and modulator
	createFilter( "RingFilter", in_wavelengths, drop_all, det_wavelengths);
	createDetector( "RingDetector", det_wavelengths, this);
	OpticalFilter* ring_filter = getFilter("RingFilter");
	OpticalDetector* ring_detector = getDetector("RingDetector");
	// Connect the filter and modulator
	getWaveguide("In")->addDownstreamNode(ring_filter);
	ring_filter->addDownstreamNode(getWaveguide("Out"));
	ring_filter->setDropPort(ring_detector);

	// Create electrical ports
	createOutputPort("Out", makeNetIndex(0, number_wavelengths-1));
	// Create net
	createNet("OutVFO");
	// Create output driver
	createDriver("OutDriver", false);
	// Connect driver
	getDriver("OutDriver")->addDownstreamNode(getNet("OutVFO"));
	// Connect output
	assignVirtualFanout("Out", "OutVFO");

	// Precompute some technology values
	precomputeTech();

	return;
	}

	void RingDetector::updateModel()
	{
	// Get some generated properties
	unsigned int number_wavelengths = getGenProperties()->get("NumberWavelengths");

	// Get tech model numbers
	double ring_area = getTechModel()->get("Ring->Area");
	double thru_loss = getTechModel()->get("Ring->ThroughLoss");
	double drop_loss = getTechModel()->get("Ring->DropLoss");
	double pd_loss = getTechModel()->get("Photodetector->Loss");
	double pd_responsivity = getTechModel()->get("Photodetector->Responsivity");

	// Design the receiver
	designReceiver();

	// Update losses
	// Connect the filter and modulator
	OpticalFilter* ring_filter = getFilter("RingFilter");
	OpticalDetector* ring_detector = getDetector("RingDetector");
	ring_filter->setLoss(thru_loss * number_wavelengths);
	ring_filter->setDropLoss(drop_loss + thru_loss * number_wavelengths);
	ring_detector->setLoss(pd_loss);
	ring_detector->setResponsivity(pd_responsivity);
	// Update device area
	getAreaResult("Photonic")->setValue(ring_area * (number_wavelengths));

	return;
	}

	void RingDetector::useModel()
	{
	// Get parameters
	const String& topology = getParameter("Topology");

	// Get some generated properties
	unsigned int number_wavelengths = getGenProperties()->get("NumberWavelengths");

	// Get optical input transition info
	const TransitionInfo& in_trans = getOpticalInputPort("In")->getTransitionInfo();

	// Get tech models
	double vdd = getTechModel()->get("Vdd");
	// Get caps
	double unit_gate_cap = getTechModel()->get("Gate->MinWidth").toDouble() * getTechModel()->get("Gate->CapPerWidth").toDouble();
	double unit_drain_cap = getTechModel()->get("Gate->MinWidth").toDouble() * getTechModel()->get("Drain->CapPerWidth").toDouble();
	double inv_x1_gate_cap = getTechModel()->getStdCellLib()->getStdCellCache()->get("INV_X1->Cap->A");
	double inv_x1_drain_cap = getTechModel()->getStdCellLib()->getStdCellCache()->get("INV_X1->Cap->Y");

	// Construct a simple sense-amp model
	if(topology == INTEGRATINGSENSEAMP)
	{
	// Use ratios from the receiver published in [Georgas, ESSCIRC 2011]
	// Note:
	// The numbers in the paper (43fJ/b, 50 fJ/b in the cited work) is done with the clock buffer (there are 4 receivers),
	// capacitive DAC, and extra output flops used in the physical layout, as the compared receiver is extremely conservative
	// We simplified this model to not have the capacitive DAC, the clock buffer (since this is an individual receiver), or
	// the extra output flops (since receiver structure is already a posedge flop functionally).
	// Look for an upcoming paper [Georgas, JSSC 2012] (when it is published) for the power breakdown pie-chart for the receiver.
	// This model only models the latch (sampler) and the dynamic to static (RS latch) part of the design, which is all you really
	// need in the receiver.

	// Gate caps
	double c_gate_sampler = unit_gate_cap * (4 * 2.0 + 2 * 1.0 + 2 * 3.0 + 2 * 5.0) + unit_gate_cap * (2 * 6.0 + 2 * 1.0) + inv_x1_gate_cap;
	double c_gate_rslatch = unit_gate_cap * (4 * 1.0) + inv_x1_gate_cap;
	// Drain caps
	double c_drain_sampler = unit_drain_cap * (2 * 2.0 + 2 * 1.0 + 3 * 5.0 + 1 * 3.0) + inv_x1_drain_cap;
	double c_drain_rslatch = unit_drain_cap * (2 * 6.0) + inv_x1_drain_cap;
	// Sum up cap switched for the sampler
	double c_sampler = c_gate_sampler + c_drain_sampler;
	double c_rslatch = c_gate_rslatch + c_drain_rslatch;
	// Average cap switched
	// Sampler is differential, one side will always switch (R or S in the latch) regardless of probability
	double avg_cap = c_sampler + c_rslatch * in_trans.getProbability0() * in_trans.getProbability1();

	// Get parameters corresponding to a unit-inverter
	double unit_leak_0 = getTechModel()->getStdCellLib()->getStdCellCache()->get("INV_X1->Leakage->!A");
	double unit_leak_1 = getTechModel()->getStdCellLib()->getStdCellCache()->get("INV_X1->Leakage->A");

	// Approximate leakage (curve fit with design)
	double total_leakage = 0.5 * (unit_leak_0 + unit_leak_1) * 7.43;

	// Create results
	getEventResult("Receive")->setValue(vdd * vdd * avg_cap * number_wavelengths);
	getNddPowerResult("Leakage")->setValue(total_leakage * number_wavelengths);

	}
	else ASSERT(false, "[Error] " + getInstanceName() + " -> Unknown receiver topology (" + topology + ")!");

	return;
	}

	void RingDetector::propagateTransitionInfo()
	{
	// Propagate probabilities from optical input to electrical output port
	getOutputPort("Out")->setTransitionInfo(getOpticalInputPort("In")->getTransitionInfo());

	return;
	}

	void RingDetector::precomputeTech()
	{
	// Get parameters
	const double data_rate = getParameter("DataRate");
	const String& topology = getParameter("Topology");

	// Get tech model numbers
	double pd_cap = getTechModel()->get("Photodetector->Cap");
	double parasitic_cap = getTechModel()->get("Photodetector->ParasiticCap");
	double apd = getTechModel()->get("Photodetector->AvalancheGain");
	double vdd = getTechModel()->get("Vdd");

	// Constants shortcuts
	double pi = Constants::pi;
	double k = Constants::k;
	double q = Constants::q;
	double T = getTechModel()->get("Temperature");

	if(topology == INTEGRATINGSENSEAMP)
	{
	// Get more tech parameters
	double integ_time_ratio = getTechModel()->get("Receiver->Int->IntegrationTimeRatio");
	double BER = getTechModel()->get("SenseAmp->BER");
	double CMRR = getTechModel()->get("SenseAmp->CMRR");
	double offset_comp_bits = getTechModel()->get("SenseAmp->OffsetCompensationBits");
	double offset = getTechModel()->get("SenseAmp->OffsetRatio").toDouble() * vdd;
	double supply_noise_rand = getTechModel()->get("SenseAmp->SupplyNoiseRandRatio").toDouble() * vdd;
	double supply_noise_det = getTechModel()->get("SenseAmp->SupplyNoiseDetRatio").toDouble() * vdd;
	double noise_margin = getTechModel()->get("SenseAmp->NoiseMargin");
	double jitter_ratio = getTechModel()->get("SenseAmp->JitterRatio");

	// Approximate tao using FO4
	double unit_drain_cap = getTechModel()->get("Gate->MinWidth").toDouble() * getTechModel()->get("Drain->CapPerWidth").toDouble();
	double c_g = getTechModel()->getStdCellLib()->getStdCellCache()->get("INV_X1->Cap->A");
	double c_d = getTechModel()->getStdCellLib()->getStdCellCache()->get("INV_X1->Cap->Y");
	double r_o = getTechModel()->getStdCellLib()->getStdCellCache()->get("INV_X1->DriveRes->Y");
	// Calculate sense amp tau from sense amp output loading
	double tau = r_o * (c_g + c_d);
	// Set output inverter drive strength
	getDriver("OutDriver")->setOutputRes(r_o);

	// Calculate sense amp input cap based on schematic
	double sense_amp_cap_in = unit_drain_cap * (2.0 + 3.0 + 5.0 + 1.0);

	// Residual offset
	double v_residual = 3 * offset / pow(2, offset_comp_bits);
	// Noise
	double v_noise = supply_noise_rand * supply_noise_rand / (CMRR * CMRR);
	// Sense amp voltage build-up minimum
	double v_sense = vdd * exp(-(1 - integ_time_ratio) / (data_rate * tau)) + noise_margin + v_residual + supply_noise_det / CMRR;
	// Sigmas corresponding to BER
	double sigma = calcInvNormCdf(BER);

	//K_int is the time the bit is valid for evaluation

	// Total input cap load
	double input_node_cap = sense_amp_cap_in + pd_cap + parasitic_cap;
	double z_int = integ_time_ratio / (data_rate * input_node_cap); //should use K_int

	// Store precalculated values
	m_quad_a_ = 1 - (sigma * sigma * jitter_ratio * jitter_ratio);
	m_quad_b1_ = - 2 * pi / 2 * sigma * sigma * q * 0.7 * data_rate;
	m_quad_b2_ = -2 * v_sense / (z_int * apd);
	m_quad_c_ = 1 / (z_int * z_int) * (v_sense * v_sense - sigma * sigma * (k * T / input_node_cap + v_noise));
	}
	else ASSERT(false, "[Error] " + getInstanceName() + " -> Unknown receiver topology (" + topology + ")!");

	return;
	}

	void RingDetector::designReceiver()
	{
	// Get some generated properties
	unsigned int number_wavelengths = getGenProperties()->get("NumberWavelengths");

	// Get relevant properties/parameters
	const String& topology = getParameter("Topology");

	// Construct a simple sense-amp model
	if(topology == INTEGRATINGSENSEAMP)
	{
	// No really good way to estimate the area...can assume each receiver is the size of 40 inverters, which is
	// about the right size for just the sense amp in the layout
	double unit_area_active = getTechModel()->getStdCellLib()->getStdCellCache()->get("INV_X1->Area->Active");
	double unit_area_metal1 = getTechModel()->getStdCellLib()->getStdCellCache()->get("INV_X1->Area->Metal1Wire");
	getAreaResult("Active")->setValue(unit_area_active * 40 * number_wavelengths);
	getAreaResult("Metal1Wire")->setValue(unit_area_metal1 * 40 * number_wavelengths);
	}
	else ASSERT(false, "[Error] " + getInstanceName() + " -> Unknown receiver topology (" + topology + ")!");

	return;
	}

	double RingDetector::getSensitivity(double ER_dB_) const
	{
	// Get parameters
	const String& topology = getParameter("Topology");
	// Turn extinction ratio into a ratio from dB scale
	double ER = pow(10, ER_dB_ / 10);

	// Initialize sensitivity
	double sensitivity = 1e99;
	// Construct a simple sense-amp model
	if(topology == INTEGRATINGSENSEAMP)
	{
	// Scale photodetector shot noise using ER, add rest of noise source
	double b = m_quad_b1_ * (1 + ER) / (2 * (ER - 1)) + m_quad_b2_;

	// Find sensitivity (-b + sqrt(b^2-4ac)) / 2a
	sensitivity = ((-b + sqrt(b * b - 4 * m_quad_a_ * m_quad_c_)) / (2 * m_quad_a_));
	}
	else ASSERT(false, "[Error] " + getInstanceName() + " -> Unknown receiver topology (" + topology + ")!");

	return sensitivity;
	}

	double RingDetector::calcInvNormCdf(double num_)
	{
	// 53 bit precision for double FP
	unsigned int num_iterations = 20;
	// Upperbound the step
	double step = 20;
	double out = step;
	// Iteratively guess and check calculation
	for (unsigned int i = 0; i < num_iterations; ++i)
	{
	double current = 0.5 * erfc(out / sqrt(2));
	if (current > num_) out += step;
	else out -= step;
	step = step * 0.5;
	}

	return out;
	}

	} // namespace DSENT